The amount of smog formed in air and the smog concentration in air is determined by measuring the consumption of nitric oxide.
(n) total concentration of ROC previously introduced into air. The following parameters can also be determined from the methods and systems of the invention: total concentration of nitric oxide previously introduced into air, total concentrations of NO.sub.x and NO.sub.y previously introduced into air, ROC/NO.sub.x concentration ratio of the total ROC and NO.sub.x previously introduced into air and average time of prior introductions of ROC into air.
BACKGROUND ART
Photochemical smog, which is commonly characterized by ozone concentrations in the order of 0.1 ppm or greater in air, is an air quality problem in many urban areas, particularly those with high levels of sunlight.
Photochemical smog formation passes through three sequential phases: (1) oxidation of NO to NO.sub.2, (2) production of O.sub.3, and (3) a final phase when O.sub.3 is maintained at, or near, its maximum amount. Chemical processes occurring during each phase are intimately related and interactions between various competing and consecutive chemical reactions make analysis of smog formation difficult. Also because the atmosphere in a state of dynamic flux since, as well as changing dispersion variables, there are changing emissions and changing meteorological conditions, e.g. sunlight, rain and temperature. In the atmosphere smog formation does not always reach completion because reactants are often dispersed before the final phase.
As a consequence of the above difficulties there is presently, despite considerable prior research efforts, a need for systems and methods which can provide reliable measures of smog formation in the atmosphere.
The commonly employed measure of smog concentration, ozone concentration, gives only a partial indication of the amount of smog formation. This problem arises because many chemical species, in addition to ozone, are products of the smog forming reactions and also because ozone is not a stable compound and is readily consumed, especially by reaction with nitric oxide. Thus at any given time the observed concentration of ozone in air is dependent upon the amount of prior emissions of nitric oxide into the air.
Considerable efforts by the inventor have thus been directed towards developing a robust method for determining the amount of photochemical smog formation in air and a laboratory size smog chamber which provides reproducible and accurate estimates of the photochemical reactivty potential of air being tested therein. However, it has been found that prior art smog chambers are prone to give irreproducible and inaccurate results which are thought to be due to different contributions from many variables, e.g. nature of the chamber walls and surface reactions therewith, shaded zones in the chamber, mixing rates, outgassing, chamber pretreatment, chamber deposits, impurities in reactants, non-uniform temperatures, etc. and smog reaction rates that are dependent on the extent of reaction.
There is also a need for a method for predicting smog formation from Reactive Organic Compounds (ROC)/air mixtures. Such a method could be used for screening solvents and fuels and assessing the photoreactivities of hydrocarbon wastes.
Photochemical smog formation from reactive organic compounds (ROC)/nitric oxide/air mixtures occurs as follows: ##STR1##
Present methods for measuring the essential reactant, ROC, which is essential for smog formation in the atmosphere are inadequate since they are either not sufficiently sensitive, are very cumbersome and labour-intensive or do not take account of the widely differing smog forming reactivities of the individual organic species which taken together comprise ROC. Frequently, the atmospheric concentrations of the individual ROC species, while sufficient to produce significant quantities of photochemical smog, are too small to be detected by the currently available sensors. Air can be analysed for ROC by high resolution gas chromatography using flame ionisation or photoionization detectors but these techniques require cumbersome sample preconcentration procedures, are labour-intensive and give data on only a subset of the photochemically active species present.
Furthermore, knowledge of the concentrations of the components of the ROC mixture does not allow the photochemical reactivity of the air to be quantitatively estimated because the role of many of the individual ROC species, and their reaction products, in the chemistry of smog formation, is uncertain. An approach sometimes adopted for ROC analysis is to measure the total non-methanic hydrocarbon concentration of the air as a single peak, backflushed from a chromatographic column after methane has been eluted, or alternatively as the difference in signal from air and air scrubbed of ROC species but without methane removal.
For some purposes this arrangement provides adequate sensitivity but the method is subject to errors in the measured concentrations because no account can be taken of the differing sensitivities of the detector to the various individual ROC species.
In other words, these techniques typically do not provide a measure of the reactivity of the total ROC in air since they do not provide the ROC compositions and this is important since in the atmosphere 250 or more ROC species have been identified of which there can be 60 major species or more and the rate of smog formation can be greatly affected by the nature and the relative proportions of the ROC species which are present.
Photochemical smog formation is a complex process wherein a multitude of reactant species are simultaneously consumed to give a wide variety of chemical product species. It is possible to measure the concentrations of many of these reactants and products and in the past such measurements have been utilized in various ways as indicators of the extent of photochemical smog production. For example, some measures that have been used to evaluate extent of reaction are: ozone concentration, peroxyacetyl nitrate concentration; nitrogen dioxide concentration; time to reach a maximum ozone concentration; time taken for the concentrations of NO and NO.sub.2 to be equal, ozone concentration attained after illumination for a fixed period and intensity; time for NO concentration to reach one half of its initial value. Such data, however, gives only a limited indication of the progress of reaction and are complex and difficult to interpret in terms of the overall rate and extent of the smog-forming reactions. Additionally the rates at which these individual reactants and products are consumed and produced vary as smog formation progresses.
OBJECTS OF INVENTION
Objects of this invention are to provide methods and systems for analysing the formation of smog in air, and more particularly for determining:
(a) rate coefficient of smog formation in air;
(b) rate of smog formation in air under selected temperature and illumination conditions;
(c) time required for maximum smog formation in air under selected temperature and illumination conditions;
(d) time period during which smog formation in air has occurred;
(e) location of a source of Reactive Organic Compounds (ROC) present in air;
(f) time required for production of a given amount of smog in air;
(g) concentration of smog in air;
(h) amount of prior smog formation in air;
(i) maximum potential smog formation in air;
(j) current extent of smog formation in air;
(k) ozone concentration in air;
(l) nitric oxide, NO.sub.y and/or ozone concentrations in air;
(m) ROC concentration of air; and/or
(n) total concentration of prior ROC emissions into air.
______________________________________
DEFINITIONS
Air Atmospheric air, including pristine air and
pristine air into which smog-forming sub-
stances (including ROC and NO.sub.x have
been introduced at some times (including
up to some days) previously. Air may
have undergone various transport and
dispersion processes including mixing
with air of other compositions and
dilution by pristine air;
a.sup.t .sub.ROC
Activity coefficient for smog formation by ROC at
time t; (units: moles smog/mole ROC/unit
illumination/unit f(T) or moles smog/mole ROC carbon/
unit illumination/unit f(T))
a.sub.ROC(i)
Activity coefficient for smog formation from species
ROC(i);
V.sup.t Volume at time t;
G.sup.t A parameter determined according to equation (58);
H Coefficient of expression (70) and formulae derived
from (70);
L Coefficient of expression (70) and formulae derived
from (70);
E.sup.t .sub.smog
the extent of smog formation in air at time t, extent
being the proportion of amount of smog produced by
time t compared to the maximum potential amount of
smog formation;
NO.sub.x NO + NO.sub.2 ;
NO.sub.y "Total gaseous oxidized nitrogen" is the
sum of NO,NO.sub.2, peroxynitric acid,
(HO.sub.2 NO.sub.2); nitric acid (HNO.sub.3); peroxy-
acetyl nitrate, (PAN); nitrous acid
(HNO.sub.2), dinitrogen pentoxide (N.sub.2 O.sub.5),
nitrate radical (NO.sub.3 .sup..) and other gaseous
organic nitrates. Other nitrogen species at
lower oxidation states, e.g. N.sub.2 O, N.sub.2,
NH.sub.3, HCN, CH.sub.3 CN are not
components of NO.sub.y ;
Smog Concentration
The sum of the concentrations of ozone and
NO.sub.y less the concentration of NO;
Amount of The gross amount of nitric oxide oxidized in
Smog Formation
the air by smog chemistry, i.e. the
moles of NO consumed by the reaction:
RO.sub.2 .sup.. + NO .fwdarw. Products;
RO.sub.2 .sup..
Hydroxyl, alkoxy and peroxy free radical species;
ROC Reactive organic compounds including carbonyl,
ROC' alkane, alkene, aromatic, carbon monoxide and other
ROC" types of gasphase carbonaceous species which when
ROC'" present in illuminated air undergo reaction wherein
oxygen molecules are consumed and nitric oxide is
oxidized;
ROC(i) A specified individual ROC compound or a specified
mixture of ROC compounds.
.sup.T,I.sub.Q t.sbsb.smog
Rate of smog formation in air at time (t) with
temperature (T) and illumination intensity (I);
X.sub.smog .sup.t
The mole fraction of smog in air at time t;
I.sub.X.sbsb.i
The mole fraction of species i in the mixture after
the first selected period;
II.sub.X.sbsb.i
The mole fraction of species i in the mixture after
the second selected period;
III.sub.X.sbsb.i
The mole fraction of species i in the mixture after
the third selected period;
X.sub.i .sup.t
The mole fraction of species i in air at time t
(mole fraction);
n.sub.i .sup.t
Number of Moles, n, of species i in air of volume
V.sup.t at time t (moles);
.sup.m V.sup.t
The volume of a defined parcel of air (m) at time t;
.sup.f n.sub.smog .sup.t
Amount of previous smog formation in air of volume
V.sup.t at time t (moles);
.sup.o n.sub.i
Denotes emissions of number of moles, n, of species i
into air;
.sup.o n.sub.i .sup.t
Cumulative emissions of species i into air of volume
V.sup.t during time period t = O to t = t, in moles;
n.sub.NO.sbsb.x .sup.t
n.sub.NO .sup.t + n.sub.NO.sbsb.2; .sup.t
.sup.o F.sub.NO
The fraction of NO in NO.sub.x emissions (.sup.o n.sub.NO
/.sup.o n.sub.NO.sbsb.x);
.sup.f X.sub.smog .sup.t
The notional concentration of smog formed in air in
the absence of NO.sub.y removal processes (mole
fraction);
o.sub.X.sbsb.i t
The cumulative emissions of species i into
air expressed as a fraction of the moles of
species i emitted to the moles of air (mole
fraction);
.sup.extra X.sub.smog .sup.t
Concentration of smog to be produced at
some future time (mole fraction);
added.sub.n.sbsb.i
Number of moles, n, of species i added to the air in
the course of analysis (moles);
.sup.I n.sub.NO
Number of moles, n, of NO present after first
selected period (moles);
k.sub.j .sup.t
Rate coefficient of reaction j at time t;
R.sub.j .sup.t
Rate of reaction j at time t;
P.sub.j,k Ratio of rate of reaction j to rate of reaction k
P.sub.j,k = R.sub.j /R.sub.k ;
.sup.fmax n.sub.smog
Maximum potential moles of smog formation in air;
.sup.Tmax n.sub.smog
Maximum potential moles of smog that can be present
in air, being total of contributions from both smog
formation processes and emissions of NO.sub.2 ;
.sup.select X.sub.smog
A selected concentration of smog in air (mole
fraction);
.sup.fmax X.sub.smog .sup.t
Maximum potential concentration of smog formed in
air (mole fraction);
.sup.Tmax X.sub.smog .sup.t
Maximum potential concentration of smog that can
be present in air, being total of contributions
from both smog formation processes and emissions
of NO.sub.2 into air (mole fraction);
R.sub.smog .sup.t
Rate coefficient for smog formation at time t;
R Gas constant;
p.sup.t Pressure at time t;
T.sup.t Temperature at time t;
X.sub.i .sup.r
Concentration of species i in reference air;
v.sub.n Volume injected by device n in a specified time;
f Flowrate;
I.sup.t Illumination intensity (in units of rate
coefficient for NO.sub.2 photolysis, min.sup.-1).
.gamma. Coefficient of equation (39);
.beta. A coefficient of smog formation.
"reference Can be simply known temperature and
temperature and
illumination conditions or can be conditions
illumination
determined with reference
conditions" to a reference gas under the same or known
temperature and illumination conditions.
______________________________________
DISCLOSURE OF INVENTION
The present inventor has found that the amount of smog formed in air and the smog concentration in air can be determined by the consumption of a single species, namely nitric oxide, and more particularly the oxidation of NO. A key step leading to smog formation is the dissociation of oxygen molecules by various smog forming reactions. The present inventor has found that for each oxygen molecule thus dissociated it can be taken that an approximately equivalent amount of nitric oxide is caused to be consumed.
Measurement of the total amount of nitric oxide consumed thus provides a quantitative measure of the amount of smog produced. The rate of smog formation can be determined by the amount of smog produced, as indicated by nitric oxide consumption (and thus oxygen dissociation) in the presence of excess nitric oxide, during a selected period under selected conditions of illumination and temperature. Alternatively, for the measurement of smog formation rate the total amount of nitric oxide consumed during the selected reaction period can be determined by addition of excess ozone to the air prior to the selected period in which circumstances the gross consumption of nitric oxide is measured as increase in ozone concentration, there being an equivalence between the nitric oxide consumed and the ozone produced under the selected conditions. Brief summaries of the techniques used to determine various parameters are given below:
1A. Determination of the Amount of Smog Formed in Air
This can be achieved by firstly sampling the air, secondly adding NO so that it is present in excess and, thirdly, measuring the difference between the total amount of nitric oxide which has been present in the air (i.e. the NO emissions into the air prior to sampling plus that added during analysis) and the concentration of residual NO present after the added NO has been allowed to react with and be consumed by any ozone that may have been present in the air.
1B. Determination of Smog Concentration in Air
Concentration of smog in air is determined by addition of excess nitric oxide to the air and after reaction with substantially all ozone present determining the concentration of smog as the difference between the total concentration of the oxidised nitrogen species (i.e. NO, NO.sub.2, peroxyacetyl nitrate, gaseous nitric acid etc) in the mixture and the nitric oxide concentration of the mixture.
A second function of the nitric oxide addition is that by removing ozone it stabilises the air in the dark, minimising the production of nitric acid within the apparatus. This is beneficial because nitric acid is readily absorbed on surfaces and can thus be lost from the gas phase within the apparatus and before being measured at the detector.
2A. Determination of Rate Coefficient for Smog Formation
Rate coefficient for smog formation is determined by subjecting air containing excess NO to photochemical reaction under controlled conditions of temperature and illumination and by measuring the rate at which excess nitric oxide is consumed. A second function of the addition of excess nitric oxide to the air is that when excess nitric oxide is present the rate of nitric oxide consumption is, to a good approximation, independent of the extent of smog formation. Addition of excess nitric oxide makes the measured rate of smog formation independent of the original nitric oxide concentration of the air.
A further function of the excess nitric oxide is that it minimises the concentration of ozone in the system, thus minimising the ozone induced side reactions such as formation of nitric acid and nitrous acids in the unilluminated parts of the system. Ozone can also undergo unwanted reactions in the dark with alkenes.
2B. Determination of Rate Coefficient for Smog Formation in Air
Rate coefficient for smog formation in air is determined by subjecting air containing excess ozone to photochemical reaction under controlled conditions of temperature and illumination and by measuring the rate at which further amounts of ozone are produced. In the presence of excess ozone, nitric oxide is consumed by the smog-forming reactions to produce nitrogen dioxide. Nitrogen dioxide undergoes photochemical reaction to produce ozone and regenerate nitric oxide. A small, steady state, nitric oxide concentration is thus maintained. The net amount of ozone produced under these conditions is a measure of the amount of nitric oxide consumed by smog formation and is thus a measure of the amount of oxygen molecules consumed by smog formation.
3. Prediction of Extent of Maximum Potential Smog Formation in Air
Prediction of the extent of maximum potential smog formation in be ascertained by determination of rate coefficient of smog formation, smog concentration and the total oxidised nitrogen concentration of the air (NO.sub.y) and the application of computational formulae as described herein.
4. Prediction of Rate and Extent of Smog Formation in Air Under Selected Conditions
Prediction of the rate and extent of smog formation that would apply to sampled air when subjected to a wide range of selected atmospheric conditions can be ascertained from the above determined properties of the air and application of the computational formulae described herein.
5. Determination of Time Required for Formation of Selected Amounts of Smog in Air Under Selected Conditions
Determination of the time required for formation of selected amounts of smog in air under a wide range of selected conditions can be ascertained from the above determined properties of the air and application of the computational formulae described herein.
6. Determination
ROC concentration is determined by subjecting air containing excess NO to photochemical reaction under controlled conditions of temperature and illumination for a selected period and by measuring the concentration excess nitric oxide consumed. The nitric oxide consumption is proportional to the ROC concentration of the air and is thus a measure of the ROC concentration of the air. A second function of the addition of excess nitric oxide to the air is that when excess nitric oxide is present nitric oxide consumption is, to a good approximation, independent of the extent of previous photochemical reaction involving the ROC. Addition of excess nitric oxide makes smog formation independent of the original nitric oxide concentration of the air.
A further function of the excess nitric oxide is that it minimises the concentration of ozone in the system, thus minimising ozone induced side reactions such as formation of nitric acid in the unilluminated parts of the system. Ozone can also undergo unwanted reactions in the dark with alkenes.
______________________________________
TABLE SUMMARISING EMBODIMENTS
Number of
Embodiment
Brief Description of Embodiments
______________________________________
1 Method for determining rate coefficient of smog
formation in air; (via NO excess);
2 Method for determining rate coefficient of smog
formation in air; (via O.sub.3 excess);
3 Method for determining concentration of smog in
air;
4 Method for determining amount of prior smog
formation in air;
5 Method for determining maximum potential and
optionally the current extent of smog formation
in air;
6 Method for determining rate of smog formation in
air under selected temperature and illumination
(via excess NO);
7 Method for determining rate of smog formation in
air under selected temperature and illumination
(via excess O.sub.3);
8 Method for determining time required for
maximum smog formation in air under selected
conditions of illumination and temperature;
9 Method for determining time period during which
smog formation in air has occurred;
10 Method for determining time required for produc-
tion of a given amount of smog in air under
selected temperature and illumination conditions;
11 Method of determining ozone concentration in air
(via determined NO and smog concentrations);
12 Method for determining nitric oxide and NO.sub.y or
ozone or both concentrations in air (via de-
termined sunlight, temperature, NO.sub.y and smog
concentrations);
13 System for determining rate coefficient of smog
formation in air (corresponding to method 1,
via NO);
14 System for determining rate coefficient of smog
formation in air (corresponding to method 2, via
O.sub.3);
15 System for determining concentration of smog in
air (corresponding to method 3);
16 System for determining amount of prior smog
formation in air (corresponding to method 4);
17 System for determining maximum potential and
optionally the current extent of smog formation
in air (Corresponding to method 5);
18 System for determining rate of smog formation
in air under selected temperature and illumination
conditions (corresponding to method 6, NO
excess);
19 System for determining rate of smog formation in
air under selected temperature and illumination
conditions (corresponding to method 7, O.sub.3 excess);
20 System for determining time required for maximum
smog formation in air under selected conditions of
illumination and temperature (corresponding to
method 8);
21 System for determining time period during which
smog formation in air has occurred (corresponding
to method 9);
22 System for determining time required for pro-
duction of a selected amount of smog in air under
selected temperature and illumination conditions
(corresponding to method 10);
23 System for determining ozone concentration of air
(corresponding to method 11, via determined NO
and smog concentrations);
24 System for determining nitric oxide and NO.sub.y or
ozone or both concentrations in air (corresponding
to method 12);
25 Method for determining ROC concentration of air
and/or total concentration of prior ROC emissions
into air; and
26 System for determining ROC concentration of air
and/or total concentration of prior ROC emissions
into air (corresponding to method 25).
______________________________________
According to a first embodiment of this invention there is provided a method for determining rate coefficient of smog formation in air, the method comprising:
(a) adding excess nitric oxide to the air to provide an excess nitric oxide/air mixture;
(b) permitting the mixture to react for a first selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(c) determining a first nitric oxide concentration of the mixture after the first selected period;
(d) illuminating the mixture of (a) or the mixture after the first selected period for a second selected period under reference temperature and illumination conditions;
(e) permitting the mixture, after illumination, to react for a third selected period wherein excess nitric oxide in the mixture reacts with any ozone present in the mixture;
(f) determining a second nitric oxide concentration of the mixture after the third selected period; and
(g) determining the rate coefficient of smog formation from the first and second nitric oxide concentrations, the reference temperature and illumination conditions and the duration of the second selected period.
According to a second embodiment of this invention there is provided a method for determining rate coefficient of smog formation in air, the method comprising:
(a) adding excess ozone to the air to provide an excess ozone/air mixture;
(b) permitting the mixture to react for a first selected period wherein excess ozone in the mixture reacts with substantially all nitric oxide in the mixture;
(c) determining a first ozone concentration of the mixture after the first selected period;
(d) illuminating the mixture of (a) or the mixture after the first selected period for a second selected period under reference temperature and illumination conditions;
(e) permitting the mixture, after illumination, to react for a third selected period wherein excess ozone in the mixture reacts with any nitric oxide present in the mixture;
(f) determining a second ozone concentration of the mixture after the third selected period; and
(g) determining the rate coefficient from the first and second ozone concentrations, the reference temperature and illumination conditions and the duration of the second selected period.
Optionally the method of the second embodiment further includes the step of (a)(i) adding a quantity of nitrogen oxides to the mixture prior to step (b). This optional step is recommended for those occasions when the nitrogen oxides concentration of the air is small and limiting on the rate of reaction during step (d).
According to a third embodiment of this invention there is provided a method for determining concentration of smog in air, which method comprises:
(a) adding excess nitric oxide to the air to provide an excess nitric oxide/air mixture;
(b) reacting the mixture for a selected period wherein the excess nitric oxide reacts with substantially all ozone in the mixture;
(c) determining the nitric oxide concentration of the mixture after the selected period;
(d) determining the total oxidized nitrogen (NO.sub.y) concentration of the mixture after the selected period; and
(e) determining the concentration of smog in the air from the nitric oxide concentration of (c) and the NO.sub.y concentration of (d).
Optionally the method of the third embodiment further includes the step of (c)(i) converting NO.sub.y in the mixture to nitric oxide prior to step (d). When step(c)(i) is included the NO.sub.y concentration in step d) can be determined by simply determining the nitric oxide concentration of the mixture.
According to a fourth embodiment of this invention there is provided a method for determining the amount of prior smog formation in air, which method comprises:
(A) determining NO.sub.y concentration of air;
(B) determining the concentration of smog in air by the method of the third embodiment;
(C) determining the concentration of total nitrogen oxides previously emitted into the air from the NO.sub.y concentration in the air and the concentration of smog in the air; and
(D) determining the amount of prior smog formation in air from the concentration of total nitrogen oxides previously emitted into the air as determined in step (C) and the concentration of smog in the air as determined in (B).
Optionally the method of the fourth embodiment further includes the steps of (A)(i), converting NO.sub.y in the air to nitric oxide prior to step (A). When step (A)(i) is included the concentration in step (A) can be determined by simply determining the nitric oxide concentration of the air.
According to a fifth embodiment of this invention there is provided a method for determining maximum potential smog formation in air, which method comprises:
(.alpha.) determining the amount of prior smog formation in air by the method of the fourth embodiment;
(.beta.) determining the concentration of total nitrogen oxides previously emitted into the air from the NO.sub.y concentration in the air and the concentration of smog in the air; and
(.gamma.) determining the maximum potential smog formation in the air from the concentration of total nitrogen oxides previously emitted into the air.
According to a sixth embodiment of this invention there is provided a method for determining rate of smog formation in air under selected temperature and illumination conditions, which method comprises:
(a) adding excess nitric oxide to the air to provide an excess nitric oxide/air mixture;
(b) permitting the mixture to react for a first selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(c) determining a first nitric oxide concentration of the mixture after the first selected period;
(d) illuminating the mixture of (a) or the mixture after the first selected period for a second selected period under selected temperature and illumination conditions;
(e) permitting the mixture, after illumination, to react for a third selected period wherein excess nitric oxide in the mixture reacts with any ozone present in the mixture;
(f) determining a second nitric oxide concentration of the mixture after the third selected period; and
(g) determining the rate from the First and second nitric oxide concentrations and the duration of the second selected period.
According to a seventh embodiment of this invention there is provided a method for determining rate of smog formation in air under selected temperature and illumination conditions, which method comprises:
(a) adding excess ozone to the air to provide an excess ozone/air mixture;
(b) permitting the mixture to react for a first selected period wherein excess ozone in the mixture reacts with substantially all nitric oxide in the mixture;
(c) determining a first ozone concentration of the mixture after the first selected period;
(d) illuminating the mixture of (a) or the mixture after the first selected period for a second selected period under selected temperature and illumination conditions;
(e) permitting the mixture, after illumination, to react for a third selected period wherein excess ozone in the mixture reacts with any nitric oxide present in the mixture;
(f) determining a second ozone concentration of the mixture after the third selected period; and
(g) determining the rate from the first and second ozone concentrations and the duration of the second selected period.
Optionally the method of the seventh embodiment further includes the step of (a)(i) adding a quantity of nitrogen oxides to the mixture prior to step (b). This optional step is recommended for those occasions when the nitrogen oxides concentration of the air is small and limiting on the rate of reaction during step (d).
According to an eighth embodiment of this invention there is provided a method for determining time required for maximum smog formation in air under selected conditions of illumination and temperature, the method comprising:
(A) determining rate coefficient of smog formation in the air according to the method of the first or second embodiments or;
(A)(i) determining rate of smog formation in the air under the selected conditions according to the method of the sixth or seventh embodiments;
(B) determining maximum potential smog formation in the air according to the method of the fifth embodiment; and
(C) determining the time for maximum smog formation, under selected temperature and illumination conditions, From the maximum potential smog formation and the rate coefficient; or
(C)(i) determining the time for maximum smog formation, under selected temperature and illumination conditions, from the maximum potential smog formation and the rate.
According to a ninth embodiment of this invention there is provided a method for determining time period during which smog formation in air has occurred, the time period being substantially the same as or within predetermined period for which the illumination and temperature conditions are known, wherein the end of the predetermined period coincides with the end of the time period, the method comprising:
(A) determining temperatures of the air for the predetermined period;
(B) determining sunlight intensities for the predetermined period;
(C) determining the rate coefficient of smog formation according to the method of the first or second embodiments; or
(C)(i) determining rates of smog formation in the air according to the methods of the sixth or seventh embodiments under temperatures and light intensities corresponding to the determined temperatures and sunlight intensities;
(D) determining the amount of prior smog formation in the air at the end of the time period according to the method of the fourth embodiment; and
(E) determining the time period during which the smog formation in the air has occurred from the amount of prior smog formation, the rate coefficient, the determined temperatures and sunlight intensities, or
(E)(i) determining the time period during which the smog formation in the air has occurred from the amount of prior smog formation and the rates of smog formation.
Optionally the location of the source of ROC present in air may be determined on the basis of the time period of smog formation and separately determined speed of movement and trajectory of the air during the time period.
According to a tenth embodiment of this invention there is provided a method for determining time required for production of a selected amount of smog in air under selected temperature and illumination conditions and with selected initial amount of smog in the air, the method comprising:
(A) determining rate coefficient of smog formation in air according to the method of the first or second embodiments; or
(A)(i) determining rates of smog formation in the air under the selected temperature and illumination conditions according to the method of the sixth or seventh embodiments;
(B) determining NO.sub.y concentration of the
(C) determining the amount of NO.sub.y previously emitted into the air from the NO.sub.y concentration of (B) and the selected initial amount of smog in the air; and
(D) determining the time required for production of selected amount of smog in the air for the selected conditions of temperature and illumination from the rate coefficient and the amount of NO.sub.y ; or
(D)(i) determining the time required for production of the selected amount of smog in the air for the selected conditions of temperature and illumination from the rate and the amount of NO.sub.y previously emitted into the air.
Optionally the method of the tenth embodiment further includes the steps of(A)(i), converting NO.sub.y in the air to nitric oxide prior to step (B). When step (A)(ii) is included the concentration in step (B) can be determined by simply determining the nitric oxide concentration of the air.
According to an eleventh embodiment of this invention there provided a method for determining ozone concentration in air, which method comprises:
(A) determining nitric oxide concentration of the air;
(B) determining NO.sub.y concentration of the air;
(C) determining concentration of smog in the air according to the method of the third embodiment; and
(D) calculating the ozone concentration of the air from the measured nitric oxide concentration, NO.sub.y concentration and the concentration of smog in the
According to a twelfth embodiment of this invention there is provided a method for determining nitric oxide and/or ozone concentrations in air, which method comprises:
(A) determining the sunlight intensity of the air;
(B) determining the temperature of the air;
(C) determining the NO.sub.y concentration of the air;
(D) determining the smog concentration of the air according to the method of the third embodiment; and
(E) determining the concentrations of nitric oxide and/or ozone in air from the NO.sub.y and smog concentrations, the sunlight intensity and the temperature.
Optionally the method of the twelfth embodiment further includes step(B)(i); converting NO.sub.y in the air to nitric oxide prior to step (C). When step (B)(i) is included the concentration in step (C) can be determined by simply determining the nitric oxide concentration of the air
According to a thirteenth embodiment of this invention there is provided a system for determining rate coefficient of smog formation in air, which system comprises:
(a) a combiner for combining excess nitric oxide with the air to provide an excess nitric oxide/air mixture;
(b) a first reactor operatively associated with the combiner wherein the mixture can react in the first reactor for a first selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(c) a photoreactor operatively associated with the combiner and optionally the first reactor;
(d) an illumination source operatively disposed about the photoreactor to illuminate the mixture of (a) in the photoreactor, or the mixture after the first selected period, in the photoreactor for a second selected period under known temperature and illumination conditions;
(e) a second reactor operatively associated with the photoreactor wherein the mixture can react in the second reactor for a third selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(f) a nitric oxide analyser operatively associated with the first reactor, to determine a first nitric oxide concentration of the mixture after the first selected period and operatively associated with the second reactor to determine a second nitric oxide concentration of the mixture after the third selected period;
(g) a temperature sensor operatively associated with the photoreactor to determine the temperature of the mixture;
(h) an illumination sensor operatively associated with the illumination source to determine the amount of illumination of the illuminated mixture; and
(i) calculating means operatively associated with the temperature and illumination sensors and the nitric oxide analyser to calculate the rate coefficient from the first and second nitric oxide concentrations, the known temperature and illumination conditions and the duration of the second selected period.
According to a fourteenth embodiment of this invention there is provided a system for determining rate coefficient of smog formation in air, which system comprises:
(a) a first combiner for combining excess ozone with the air to provide an excess ozone/air mixture;
(b) a first reactor operatively associated with the combiner wherein the mixture can react in the first reactor for a first selected period wherein excess ozone in the mixture reacts with substantially all nitric oxide in the mixture;
(c) a photoreactor operatively associated with the combiner and optionally the first reactor;
(d) an illumination source operatively disposed about the photoreactor to illuminate the mixture of (a) in the photoreactor, or the mixture after the first selected period, in the photoreactor for a second selected period under known temperature and illumination conditions;
(e) a second reactor operatively associated with the photoreactor wherein the mixture can react in the second reactor for a third selected period wherein excess ozone in the mixture reacts with substantially all nitric oxide in the mixture;
(f) an ozone analyser operatively associated with the first reactor to determine a first ozone concentration of the mixture after the first selected period and operatively associated with the second reactor to determine a second ozone concentration of the mixture after the third selected period;
(g) a temperature sensor operatively associated with the photoreactor to determine the temperature of the mixture;
(h) an illumination sensor operatively associated with the illumination source to determine the amount of illumination of the illuminated mixture; and
(i) calculating means operatively associated with the temperature and illumination sensors and the ozone analyser to calculate the rate coefficient from the first and second ozone concentrations, the known temperature and illumination conditions and the duration of the second selected period.
Optionally the system of the fourteenth embodiment further includes a second combiner operatively associated with the first combiner for combining a quantity of nitrogen oxides with the air.
According to a fifteenth embodiment of this invention there is provided a system for determining concentration of smog in air, which system comprises:
(a) a combiner for combining excess nitric oxide with the air to provide an excess nitric oxide/air mixture;
(b) a reactor operatively associated with the combiner wherein the mixture can react in the reactor for a selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(c) a nitric oxide analyser operatively associated with the reactor to determine the nitric oxide concentration of the mixture after the selected period;
(d) a NO.sub.y analyser operatively associated with the reactor to determine the NO.sub.y concentration of the mixture; and
(e) calculating means operatively associated with the nitric oxide analyser and the NO.sub.y analyser to calculate the concentration of smog from the NO.sub.y and nitric oxide concentrations.
Preferably the NO.sub.y analyser of (d) includes a NO.sub.y converter to convert all NO.sub.y in the mixture to nitric oxide, the converter being operatively associated with the nitric oxide analyser of (c). In this preferred arrangement the NO.sub.y analyser consists of the NO.sub.y converter and the nitric oxide analyser of (c).
According to a sixteenth embodiment of this invention there is provided a system for determining amount of prior smog formation in air, which system comprises:
(a) a first NO.sub.y analyser to determine the NO.sub.y concentration of the air;
(b) a combiner for combining excess nitric oxide with the air to provide an excess nitric oxide/air mixture;
(c) a reactor operatively associated with the combiner wherein the mixture can react in the reactor for a selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(d) a nitric oxide analyser operatively associated with the reactor to determine the nitric oxide concentration of the mixture after the selected period;
(e) a second NO.sub.y analyser operatively associated with the reactor to determine the NO.sub.y concentration of the mixture; and
(f) calculating means operatively associated with the nitric oxide analyser and the first and second NO.sub.y analysers to calculate the amount of prior smog formation in air from the NO.sub.y concentration of the air and the NO and NO.sub.y concentrations of the excess nitric oxide/air mixture.
Preferably the NO.sub.y analyser of (a) is the same NO.sub.y analyser employed in (e) operatively associated to the combiner of (b) so as to determine the NO.sub.y concentration of air before excess nitric oxide is combined with air.
Also preferably the NO.sub.y analyser of (a) and (d) includes a NO.sub.y converter to convert all NO.sub.y in the mixture to nitric oxide, the converter being operatively associated with the nitric oxide analyser of (d). In this preferred arrangement the NO.sub.y analyser consists of the NO.sub.y converter and the nitric oxide analyser of (d).
According to a seventeenth embodiment of this invention there is provided a system for determining maximum potential and optionally the current extent of smog formation in air, which system comprises:
(a) a first NO.sub.y analyser for determining the NO.sub.y concentration of the air;
(b) a combiner for combining excess nitric oxide with the air to provide an excess nitric oxide/air mixture;
(c) a reactor operatively associated with the combiner wherein the mixture can react in the reactor for a selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture:
(d) a nitric oxide analyser operatively associated with the reactor to determine the nitric oxide concentration of the mixture after the selected period:
(e) a second NO.sub.y analyser operatively associated with the reactor to determine the NO.sub.y concentration of the mixture; and
(f) calculating means operatively associated and coupled with the nitric oxide analyser and the first and second NO.sub.y analysers to calculate the maximum potential and optionally the current extent of smog formation in air from the NO.sub.y concentration of the air and the NO.sub.y and NO.sub.Y concentrations of the excess nitric oxide/air mixture.
Preferably the NO.sub.y analyser of (a) is the same NO.sub.y analyser employed in (e) coupled to and operatively associated to the combiner of (b) so as to determine the NO.sub.y concentration of air before excess nitric oxide is combined with air.
Also preferably the NO.sub.y analyser of (a) and (e) includes a NO.sub.y converter to convert all NO.sub.y in the mixture to nitric oxide, the converter being operatively associated with the nitric oxide analyser of (d). In this preferred arrangement the NO.sub.y analyser consists of the NO.sub.y converter and the nitric oxide analyser of (d).
According to an eighteenth embodiment of this invention there is provided a system for determining rate of smog formation in air under selected temperature and illumination conditions, which system comprises:
(a) a combiner for combining excess nitric oxide with the air to provide an excess nitric oxide/air mixture;
(b) a first reactor operatively associated with the combiner wherein the mixture can react in the first reactor for a first selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(c) a photoreactor operatively associated with the combiner and optionally the first reactor;
(d) an illumination source operatively disposed about the photoreactor to illuminate the mixture of (a), in the photoreactor, or the mixture after the first selected period, in the photoreactor for a second selected period under selected temperature and illumination conditions;
(e) a second reactor operatively associated with the photoreactor wherein the mixture can in the second reactor react for a third selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(f) a nitric oxide analyser operatively associated with the first reactor to determine a first nitric oxide concentration of the mixture after the first selected period and operatively associated with the second reactor to determine a second nitric oxide concentration of the mixture after the third selected period; and
(g) calculating means operatively associated with the nitric oxide analyser to calculate the rate from the first and second nitric oxide concentrations and the duration of the second selected period.
According to a nineteenth embodiment of this invention there is provided a system for determining rate of smog formation in air under selected temperature and illumination conditions, which system comprises:
(a) a first combiner for combining excess ozone is combined with the air to provide an excess ozone/air mixture;
(b) a first reactor operatively associated with the combiner wherein the mixture can react in the reactor for a first selected period wherein excess ozone in the mixture reacts with substantially all nitric oxide in the mixture;
(c) a photoreactor operatively associated with the combiner and optionally the first reactor;
(d) an illumination source operatively disposed about the photoreactor to illuminate the mixture of (a), in the photoreactor, or the mixture after the first selected period, in the photoreactor for a second selected period under selected temperature and illumination conditions;
(e) a second reactor operatively associated with the photoreactor wherein the mixture can react in the second reactor for a third selected period wherein excess ozone in the mixture reacts with substantially all nitric oxide in the mixture;
(f) an ozone analyser operatively associated with the first reactor to determine a first ozone concentration of the mixture after the first selected period and operatively associated with the second reactor to determine a second ozone concentration of the mixture after the third selected period; and
(g) calculating means operatively associated with the ozone analyser to calculate the rate from the first and second ozone concentrations and the duration of the second selected period.
In preferred embodiments of the thirteenth, fourteenth, eighteenth and nineteenth embodiments the first and second reactors and the photoreactor are the same reactor. In other preferred embodiments the first reactor and the photoreactor are the same reactor and in yet other embodiments the second reactor and the photoreactor are the same reactor.
In still other preferred embodiments the first reactor and photoreactor are two separate vessels through which the mixture can continuously flow in separate streams and the second reactor is a separate vessel through which the mixture from the photoreactor can continuously flow.
In such embodiments, the first reactor provides a first residence time for the mixture when continuously flowing therethrough and the photoreactor and the second reactor in combination provide a second residence time for the mixture when continuously flowing therethrough, the first and second residence times being substantially the same.
Optionally the system of the nineteenth embodiment further includes a second combiner operatively associated with the combiner of ozone in which second combiner a quantity of NO.sub.x is added to air. This is recommended when the nitric oxide concentration of air is small and limiting on the rate of reaction in the photolytic reactor.
According to a twentieth embodiment of this invention there is provided a system for determining time required for maximum smog formation in air under selected conditions of illumination and temperature wherein the system includes:
(A) a NO.sub.y analyser to determine the NO.sub.y concentration of the air;
(B) the system of the thirteenth or fourteenth embodiments to determine the rate coefficient of smog formation in the air; or
(B)(i) the system of the eighteenth or nineteenth embodiments to determine the rates of the smog formation in air under the selected conditions;
(C) the system of the seventeenth embodiment to determine the maximum potential smog formation in the air; and
(D) calculating means operatively associated with the analyser of (A) and the systems of (B) and (C) to calculate the maximum time for smog formation, under the selected temperature and illumination conditions from the NO.sub.y concentration, the extent of smog formation and the rate coefficient; or
(D)(i) calculating means operatively associated with the analyser of (A) and the systems of (B)(i) and (C) to calculate the maximum time for smog formation, under the selected temperature and illumination conditions from the NO.sub.y concentration, the extent of smog formation and the rates.
Preferably the NO.sub.y analyser of (A) includes a NO.sub.y converter to convert all the NO.sub.y in the air to nitric oxide and a nitric oxide analyser to determine the total nitric oxide in this preferred arrangement the NO.sub.y analyser consists of the NO.sub.y converter and the nitric oxide analyser and the NO analysers of the systems of (A), (B) or (B)(i) and (C) are the same analyser,
According to a twenty-first embodiment of this invention there is provided a system for determining time period during which smog formation in air has occurred, the time period being substantially the same as or within a selected period for which the illumination and temperature conditions are known, wherein the end of the selected period coincides with the end of the time period the system includes:
(A) the system of the thirteenth or fourteenth embodiments for determining the rate coefficient of smog formation in the air; or
(A)(i) the system of the eighteenth or nineteenth embodiments for determining the rates of smog formation in the air;
(B) the system of the fifteenth embodiment for determining concentration of smog in the air;
(C) an NO.sub.y analyser for determining the NO.sub.y concentration of air;
(D) a temperature sensor to determine the temperature of the air for the duration of the selected period;
(E) a light sensor to determine the sunlight illumination during the selected period; and
(F) calculating means operatively associated with the temperature sensor, the light sensor, the NO.sub.y analyser and the systems for determining the rate coefficient of smog formation and smog concentration, to calculate the time period during which smog formation in air has occurred under the measured sunlight and temperature conditions; or
(F)(i) calculating means operatively associated with the temperature sensor, the light sensor, the NO.sub.y analyser and the systems of a(i) and (b) to calculate the time period during which smog formation has occurred under the measured sunlight and temperature conditions.
Preferably the NO.sub.y analyser of (C) includes a NO.sub.y converter to convert all NO.sub.y in the mixture to nitric oxide, the converter being operatively associated with a nitric oxide analyser. In this preferred arrangement the NO.sub.y analyser consists of the NO.sub.y converter and the nitric oxide analyser and the NO.sub.y analysers of the systems of (A) and (B) and the NO analyser of (C) are the same analyser.
Optionally the system of the twenty-first embodiment further includes means of determining the speed and trajectory of the air during the selected period and calculating means to determine the location of the emission sources of ROC present in air on the basis of the time period of smog formation, the air speed and trajectory.
According to a twenty-second embodiment of this invention there is provided a system for determining time required for production of a selected amount of smog in air under selected temperature and illumination conditions the system comprising
(A) the system of the thirteenth or fourteenth embodiments for determining rate coefficient of smog formation in the air; or
(A)(i) the system of the eighteenth or nineteenth embodiments for determining the rates of smog formation in the air;
(B) the system of the fifteenth embodiment for determining concentration of smog in the air;
(C) an NO.sub.y analyser for determining the NO.sub.y concentration of the air; and
(D) calculating means operatively associated with the systems for determining: the rate coefficient, smog concentration and the NO.sub.y analyser, to calculate the time required for the production of a selected amount of smog in the air under selected temperature and illumination conditions; or
(D)(i) calculating means operatively associated with the systems of (A)(i) and (B) and the NO.sub.y analyser, to calculate the time required for the production of a selected amount of smog in air under selected temperature and illumination conditions.
Preferably the NO.sub.y analyser of (C) includes a NO.sub.y converter to convert substantially all NO.sub.y in the mixture to nitric oxide, the converter being operatively associated with the nitric oxide analyser of (B). In this preferred arrangement the NO.sub.y analyser consists of the NO.sub.y converter and the nitric oxide analyser of (B).
According to a twenty-third embodiment of this invention there is provided a system for determining ozone concentration in air which system comprises:
(A) a nitric oxide analyser to determine the nitric oxide concentration of the air;
(B) a NO.sub.y analyser to determine the NO.sub.y concentration of the air;
(C) the system of the fifteenth embodiment for determining the concentration of smog in the air; and
(D) calculating means operatively associated with the nitric oxide analyser of (A) the NO.sub.y analyser of (B) and the system of (C) to calculate the ozone concentration from the nitric oxide concentration, NO.sub.y concentration and smog concentration of the air.
Preferably the nitric oxide analyser of (A) and the NO.sub.y analyser of (B) are the same nitric oxide and NO.sub.y analysers of the system of (C).
According to a twenty-fourth embodiment of this invention there is provided a system for determining nitric oxide and NO.sub.y or ozone or both concentrations in air which system comprises:
(A) a light sensor to determine the sunlight intensity of the air;
(B) a temperature sensor to determine the temperature of the air;
(C) an NO.sub.y analyser to determine the NO.sub.y concentration of the air;
(D) the system of the fifteenth embodiment to determine the smog concentration of the air; and
(E) calculating means operatively associated with the light and temperature sensors and the NO.sub.y analyser and smog concentration measurement systems the calculating means to calculate the nitric oxide and ozone concentrations of the air from the sunlight intensity, air temperature and the NO.sub.y and smog concentrations.
Preferably the NO.sub.y analyser of (C) is the same NO.sub.y analyser of the system (D).
According to a twenty-fifth embodiment of this invention there is provided a method for determining ROC concentration of air and/or a method for determining total concentration of prior ROC emissions into air, which method comprises:
(a) adding excess nitric oxide to the air to provide an excess nitric oxide/air mixture;
(b) permitting the mixture to react for a first selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(c) determining a first nitric oxide concentration of the mixture after the first selected period;
(d) illuminating the mixture of (a) or the mixture after the first selected period for a second selected period under known temperature and illumination conditions;
(e) permitting the mixture, after illumination, to react for a third selected period wherein excess nitric oxide in the mixture reacts with any ozone present in the mixture;
(f) determining a second nitric oxide concentration of the mixture after the third selected period; and
(g) determining the ROC concentration of air, and/or determining the total concentration of prior ROC emissions into the air, from the first and second nitric oxide concentrations
According to a twenty-sixth embodiment of this invention there is provided a system for determining ROC concentration of air and/or total concentration of prior ROC emissions into air, which system comprises:
(a) a combiner for combining excess nitric oxide with the air to provide an excess nitric oxide/air mixture;
(b) a first reactor operatively associated with the combiner wherein the mixture can react in the first reactor for a first selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(c) a photoreactor operatively associated with the combiner and optionally the first reactor;
(d) an illumination source operatively disposed about the photoreactor to illuminate the mixture of (a), in the photoreactor, or the mixture after the first selected period, in the photoreactor for a second selected period under selected temperature and illumination conditions;
(e) a second reactor operatively associated with the photoreactor wherein the mixture can in the second reactor react for a third selected period wherein excess nitric oxide in the mixture reacts with substantially all ozone in the mixture;
(f) a nitric oxide analyser operatively associated with the first reactor to determine a first nitric oxide concentration of the mixture after the first selected period and operatively associated with the second reactor to determine a second nitric oxide concentration of the mixture after the third selected period; and
(g) calculating means operatively associated with the nitric oxide analyser to calculate the ROC concentration of air, and/or total concentration of prior ROC emissions into air, from the first and second nitric oxide concentrations.
According to a further embodiment of this invention there is provided a method of locating a source of Reactive Organic Compounds (ROC) present in air, the method comprising:
(.alpha.) determining a time period during which smog formation in the air has occurred, the time period being substantially the same as or within a predetermined period for which the illumination and temperature conditions are known, wherein the end of the predetermined period coincides with the end of the time period by:
(A) determining temperatures of the air for the predetermined period;
(B) determining sunlight intensities for the predetermined period;
(C) determining the rate coefficient of smog formation in the air by the method described herein;
(D) determining the amount of prior smog formation in the air at the end of the time period by:
(I) determining NO.sub.y concentration in the air;
(II) determining the concentration of smog in the air by:
(II)(i) adding excess nitric oxide to the air to provide an excess nitric oxide/air mixture;
(II)(ii) reacting the mixture for a selected period wherein the excess nitric oxide reacts with substantially all ozone in the mixture;
(II)(iii) determining the nitric oxide concentration of the mixture after the selected period;
(II)(iv) determining the total oxidized nitrogen (NO.sub.y) concentration of the mixture after the selected period; and
(II)(v) determining the concentration of smog formation from the nitric oxide concentration of (II)(iii) and the NO.sub.y concentration of (II)(iv).
(III) determining the concentration of total nitrogen oxides previously emitted into the air from the NO.sub.y concentration in the air and the concentration of smog in the air; and (IV) determining the amount of prior smog formation in the air from the concentration of total nitrogen oxides previously emitted into the air as determined in step (III) and the concentration of smog in the air as determined in (II); and
(E) determining the time period during which the smog formation in the air has occurred from the amount of prior smog formation, the rate coefficient, and the determined temperatures and sunlight intensities; and
(.beta.) determining speed of movement and trajectory in the air during the time period; and
(.gamma.) locating said source of ROC from said time period and said speed and trajectory in the air over said time period.
According to a still further embodiment of this invention there is provided a method for determining the current extent of smog formation in air, which method comprises the steps of:
(I) determining maximum potential smog formation in air by the method of the fifth embodiment; and
(II) calculating the extent of smog formation in air as the ratio of the concentration of smog in air to the maximum potential concentration of smog in air.
The temperature of the mixture can be kept constant during illumination, can be allowed to vary and optionally monitored or the temperature of the mixture can be varied according to a preselected or selected temperature profile. Thus, it is preferred that a temperature controller/programmer is operatively associated with the photoreactors of the thirteenth, fourteenth, eighteenth, nineteenth and twenty-sixth embodiments.
The illumination can be kept constant or can be varied according to a preselected or selected illumination profile. It is therefore preferred that an illuminator controller/programmer is operatively associated with and coupled with the illumination sources of the thirteen, fourteenth, eighteenth, nineteenth and twenty-sixth embodiments.
Preferred illumination sources provide an actinic flux of similar intensity and spectral distribution to sunlight at about noon on a clear day. It may be adequate for the purpose, however, to approximate the solar spectrum by only the "UVA" part of the total wavelength band.
Illumination may be provided by a single type of lamp or various lamp type and filter combinations. For example, actinic UV fluorescent tubes are suitable as is a high pressure xenon arc and pyrex glass filter combination. The preferred illumination intensity is that which yields a rate coefficient for the photodissociation of nitrogen dioxide (NO.sub.2 +h.nu..fwdarw.NO+O) of .about.0.4 min.sup.-1. However intensities which depart markedly from this value are viable. Times preferred for the first and third reaction periods are of tile order of a few minutes, which is sufficient for the reaction of nitric oxide with ozone to be substantially complete. The preferred time for the second selected period is about 10 minutes or so long as is required to produce measurable consumption of nitric oxide in air containing significant quantity of ROC.
The systems of the thirteenth, fourteenth, fifteenth, sixteenth, seventeenth, eighteenth, nineteenth and twenty-sixth embodiments optionally include first metered delivery means to deliver metered doses of air to the combiner and includes second metered delivery means to deliver metered doses of nitric oxide to the combiner.
The fourteenth and nineteenth embodiments optionally include third metered delivery means to deliver metered doses of ozone to the combiner and ozone filter to filter ozone prior to injection into the combiner.
Optionally the systems of the thirteenth, fourteenth, fifteenth, sixteenth, seventeenth, eighteenth, nineteenth and twenty-sixth embodiments include an air filter to filter air prior to injection into the combiner and a nitric oxide filter to filter nitric oxide prior to injection into the combiner.
It is preferred that the photoreactor is constructed from material that is transparent to illumination and is chemically unreactive. FEP teflon film is an example of material which is suitable for this purpose.
FEP teflon film has the advantages that it is chemically unreactive and is transparent to ultraviolet light and is available in thin but robust film form.
The concentration of nitric oxide excess i
