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1.
A spatial cumulative distribution function (SCDF) gives the proportion of a spatial domain D having the value of some response variable less than a particular level w. This article provides a fully hierarchical approach to SCDF modeling, using a Bayesian framework implemented via Markov chain Monte Carlo (MCMC) methods. The approach generalizes the customary SCDF to accommodate density or indicator weighting. Bivariate spatial processes emerge as a natural approach for framing such a generalization. Indicator weighting leads to conditional SCDFs, useful in studying, for example, adjusted exposure to one pollutant given a specified level of exposure to another. Intensity weighted (or population density weighted) SCDFs are particularly natural in assessments of environmental justice, where it is important to determine if a particular sociodemographic group is being excessively exposed to harmful levels of certain pollutants. MCMC methods (combined with a convenient Kronecker structure) enable straightforward estimates or approximate estimates of bivariate, conditional, and weighted SCDFs. We illustrate our methods with two air pollution datasets, one recording both nitric oxide (NO) and nitrogen dioxide (NO2) ambient levels at 67 monitoring sites in central and southern California, and the other concerning ozone exposure and race in Atlanta, GA.  相似文献   

2.
We describe movement patterns of hatchery-raised, juvenile, spring chinook salmon, Oncorhynchus tshawytscha, using a two-state Markov chain model. The existence of two states, moving and holding, is suggestedby anecdotalinformation from a large radio telemetry study; yet adequate observations of these small-scale fish behaviors are not available for estimating transition probabilities directly. Instead, we estimate the transition probability matrix from travel times within each of 11 river segments using a method of moments approach. Bootstrapped confidence intervals are presented. Results suggest that fish behavior in the region of the confluence between the Grande Ronde and Snake Rivers includes many transitions between moving and staying while fish behavior in the Snake River is more likely to include long periods of staying.  相似文献   

3.
Open top chambers (OTCs) are useful tools to assess the impact of atmospheric pollutants on plants in the natural environment. We have previously reported that, in tomato plants, the LTR-GUS construct derived from the Tnt1A promoter of tobacco was activated by a realistic level of ozone pollution. In this study, we used OTCs to fumigate tomato plants with benzene or formaldehyde in order to assess the impact of these pollutants on plant growth and development and evaluate the usefulness of the LTR-GUS construct as a biomarker in plants. Whereas the LTR-GUS construct could be used as an efficient biomarker of realistic levels of ozone pollution, it is to a lesser extent applicable to formaldehyde. Indeed, only unrealistic concentration of pollutant activated the construct though important injuries were observed at a lower concentration. For benzene, no activation could be demonstrated, however, we did not notice any visual impact on plant growth and health for this pollutant.  相似文献   

4.
A. K. DOLUI  S. S. ROY 《土壤圈》2005,15(5):611-619
Two Inceptisols and an Alfisol of the Indravati Catchment area in Chattisgarh, India, comprising several gradients in physical and chemical properties were studied to relate phosphate sorption and desorption to soil properties. From the P isotherm curve, the standard P requirement （SPR） of the soils was determined. Phosphate sorption data were also fitted both to the Langmuir and Freundlich Equations. The mean sorption maximum values for three different soil series were： Bastar 〉 Geedam 〉 Mosodi. The fraction of added phosphate sorbed for the 3 series followed this same trend as did SPR; the phosphate sorption maximum and the maximum phosphate buffering capacity, which were estimated by the Langmuir isotherm; and the Freundlich constant 1/n. However, phosphate desorption, as well as the maximum recovery percent did not follow this order. The phosphate affinity constant （K） was also different following the same progression for the 3 soil series as the Freundlich constant K＇, which measured sorption strength. Meanwhile, an inverse order existed for K and K＇ versus the percent desorbed relative to the sorbed as well as the maximum recovery percent. In addition, significant correlation coefficients among sorption parameters of P and soil factors were found.  相似文献   

5.
The enthalpy changes (ΔH) for melting of crystallites formed during retrogradation of 60% (w/w) amylopectins (AP) aged at 4°C were investigated using AP from 13 rice cultivars with well‐known structural properties. According to the Avrami equation, the resultant kinetic parameters for AP retrogradation were obtained in relation to structural factors. Generally, the AP systems studied showed two stages of retrogradation behavior during early (≤7 days) and late (≥7 days) storage. The Avrami exponent for early‐stage kinetics (n1, 1.04–5.54) was greater than the corresponding value for late‐stage kinetics (n2, 0.28–1.52). While the Avrami K constant of the early‐stage kinetics (K1, 1.0×10‐5 to 2.3×10‐1 day‐n) was lower than the corresponding value of late‐stage kinetics (K2, 4.4×10‐2 to 1.4 day‐n). The ΔH values for late and infinite retrogradation stages showed a significantly positive correlation with the proportions of short chain (chain length [CL] ≤ 15 glucose units) and long chain (CL = 16–100 glucose units) fractions, respectively. Retrogradation of AP with a higher number‐average degree of polymerization, greater proportion of short chain fractions, and shorter average chain lengths revealed significantly greater n1 values and smaller K1 values. Values for n2 and K2 showed little influence from the molecular properties except for the proportion of extra long (CL>100 glucose units) and long chain fractions on K2. The negatively linear relationships between log K and n suggest the importance of some nonstructural factors for AP retrogradation mechanisms in various starch systems.  相似文献   

6.
外加盐对凉粉草胶溶液的耐盐性和分子链刚性度的影响   总被引：1，自引：0，他引：1  
在有盐环境下贮藏和加工凉粉草胶必须了解其多糖分子对盐的敏感性，该文绘制了凉粉草胶多糖在不同离子强度NaCl、KCl、MgCl2和CaCl2溶液中的Huggins'图，分别计算其分子链在这4种离子溶液中的耐盐度S、链刚性度B等值，结果发现：凉粉草胶多糖在4种离子溶液中，其耐盐性由强到弱的顺序为:K+>Na+>Mg++>Ca++，其分子链的构象在4种离子溶液中由柔到刚的顺序为:K+>Na+>Mg++>Ca++，这说明凉粉草胶多糖适合在KCl溶液中贮藏和加工。与其他多糖分子链在NaCl溶液中的B值比较后发现，凉粉草胶多糖的分子链构象较海藻酸钠要刚，较黄原胶要柔，这说明凉粉草胶比黄原胶更适合在NaCl溶液中贮藏和加工。  相似文献   

7.
The rate of hydrolysis of urea in soil over the wide range of concentrations, up to 10 moles N per dm3 soil solution, found in fertilizer practice, was examined in Begbroke sandy loam adjusted to different pH values. On rewetting air-dry soil, urease activity increased rapidly, reached a maximum within the first 24 h and then decreased slowly to level off after about 4 days. Pretreatment of the soil with urea or ammonium had no effect on the urease activity. Urease activity increased with substrate concentration, reached an optimum value and then decreased with rising urea concentration. The results could be explained by substrate inhibition at higher urea concentrations, and the data are well described by a modified Michaelis-Menten equation involving three parameters, Vmax, Km and Ki where Ki is an inhibition constant. Km decreased linearily with rise in pH whereas Ki increased slightly between pH 4.9 and 7.0 and steeply between 7.0 and 8.4. Vmax increased with rise in pH, reached a maximum value at pH 6.0 and then declined at higher pHs. There was a further reaction, reaching a maximum rate at a urea concentration of about 0.2 molar N in the soil solution, that followed Michaelis-Menten kinetics. Km for this high affinity reaction increased up to pH 7.2 and then decreased at higher pH values; Vmax increased up to pH 6.8 and then decreased. The contribution of the high affinity reaction was small except at low concentrations of urea.  相似文献   

8.
Samples from potato (Solanum tubersosum), cauliflower (Bropica Oleracu var. Botryhs), and cabbage (Brassica Olerace var. Capitela) and soil samples were collected from fields receiving sewage sludge loads for a long periods and were analyzed for their total concentration of chromium (Cr), cadmium (Cd), lead (Pb), nickel (Ni), and cobalt (Co) in different plant parts and in soil samples. Estimation of these pollutant elements was also made in the extract of the rooting zone (soil) of these plants. The accumulation of pollutant elements was higher in roots than in leaves and shoots, whereas the soil nearer to the discharge point had the maximum DTPA-CaCl2 extractable pollutant elements and their concentrations diminished with distance. In soil samples, accumulation of the pollutant elements occurred in the order Pb > Cr > Ni > Cd > Co. In vegetables, the rate of accumulation was in the order potato > cauliflower > cabbage. The growth of the vegetable plants on contaminated soil was depressed, young leaves showed marked chlorosis, and brown necrotic spots later developed on almost the entire foliage of plants. With increase in age, the affected leaves had a wilted look. The vegetables growing near the discharge point contained the maximum amounts of heavy metals, which were above toxic limits. Of these elements, the accumulation of Cr by potato was highest.  相似文献   

9.
Air quality levels vary over regions due to meteorological factors, proximity to sources, and local conditions (i.e., topography). The Northeast USA is subjected to pollution inputs from both local sources and those from the upwind Midwest USA that are transported by prevailing meteorological patterns. With the passage of the Clean Air Act in 1970 and the establishment of the National Ambient Air Quality Standards (NAAQS), national levels of air pollutants have declined significantly. Our study compared air quality time trends between five of the largest cities within New York State (Albany, Buffalo, New York City, Rochester, and Syracuse) and statewide means to national trends. Data were obtained from the NYS Department of Environmental Conservation (DEC) Bureau of Air Quality Surveillance for six criteria pollutants: carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), particulate matter (PM2.5), and lead (Pb). Regional Kendall tests found significant downward trends for each pollutant statewide from 1980 to 2007, while trends by city varied by decade and pollutant. The evaluation of historical trends of pollution in industrialized nations is useful in showing recent air quality improvements and also in the understanding what can be the result in air pollutant controls in those developing nations currently experiencing high levels of pollution.  相似文献   

10.
邹刚华  赵凤亮  单颖  李勇 《土壤》2019,51(3):517-523
反硝化作用是土壤氮素损失的重要途径,对反硝化潜势的准确估算是农业精准施肥的必然要求。以亚热带典型红壤稻田土作为研究对象,足量添加外源氮进行室内淹水厌氧培养获取反硝化作用动态,并分别用米氏方程和一级动力学方程对其拟合,最后利用土壤基本理化性质对反硝化动力学参数进行估算。结果表明:米氏方程更适合反硝化动力学拟合,最佳的米氏常数(Km)为35mg/kg;米氏最大速率常数(vmax)与一级动力学速率常数(K)具有显著的相关性(r=0.96, P0.05)。土壤总氮,砂粒和粉粒以及土壤容重对vmax影响最大。利用总氮和粉粒含量作为输入参数估算了vmax,准确度达66%。所构建的参数方程既充分挖掘了土壤基础数据潜能,又能快速地获取土壤反硝化动力学曲线,省时省力。  相似文献   

11.
Saturated hydraulic conductivity (Ks) of the soil is a key variable in the water cycle. For the humid tropics, information about spatial scales of Ks and their relation to soil types deduced from soil map units is of interest, as soil maps are often the only available data source for modelling. We examined the influence of soil map units on the mean and variation in Ks along a transect in a tropical rainforest using undisturbed soil cores at 0–6 and 6–12 cm depth. The Ks means were estimated with a linear mixed model fitted by residual maximum likelihood (REML), and the spatial variation in Ks was investigated with the maximum overlap discrete wavelet packet transform (MODWPT). The mean values of Ks did not differ between soil map units. The best wavelet packet basis for Ks at 0–6 cm showed stationarity at high frequencies, suggesting uniform small‐scale influences such as bioturbation. There were substantial contributions to wavelet packet variance over the range of spatial frequencies and a pronounced low frequency peak corresponding approximately to the scale of soil map units. However, in the relevant frequency intervals no significant changes in wavelet packet variance were detected. We conclude that near‐surface Ks is not dominated by static, soil‐inherent properties for the examined range of soils. Several indicators from the wavelet packet analysis hint at the more dominant dynamic influence of biotic processes, which should be kept in mind when modelling soil hydraulic properties on the basis of soil maps.  相似文献   

12.
Abstract

The effectiveness of Stay‐N 2000 or reformulated nitrapyrin [2‐chloro‐6‐(tricholoromethyl) pyridine] was investigated in two Iowa soils representative of Clarion and Okoboji soils that differed in organic carbon, pH, and texture. A nonlinear regression was used to estimate kinetic parameters. The maximum nitrification rate (K max) and the duration of lag period (t′) were derived from the equation to characterize the nitrification process in both soils. Stay‐N 2000 appeared to be a better inhibitor than nitrapyrin to extend t′ and as effective as nitrapyrin in reducing K max. Stay‐N 2000 reduced K max an appreciable amount in the Okoboji soil at the rate of 12 µg a.i. g?1 soil or three times the recommended rate. Nitrification rates were affected by the rates of nitrogen (N) applied to both soils; the higher the N rates, the higher Kmax, and the more the nitrate (NO3 ?)‐N accumulation.  相似文献   

13.
Using within-weather-group air pollution prediction models developed in Part I of this research, this study estimates future air pollution levels for a variety of pollutants (specifically, carbon monoxide – CO, nitrogen dioxide – NO2, ozone – O3, sulphur dioxide – SO2, and suspended particles – SP) under future climate scenarios for four cities in south-central Canada. A statistical downscaling method was used to downscale five general circulation model (GCM) scenarios to selected weather stations. Downscaled GCM scenarios were used to compare respective characteristics of the weather groups developed in Part I; discriminant function analysis was used to allocate future days from two windows of time (2040–2059 and 2070–2089) into one of four weather groups. In Part I, the four weather groups were characterised as hot, cold, air pollution-related, and other (defined as relatively good air quality and comfortable weather conditions). In estimating future daily air pollution concentrations, three future pollutant emission scenarios were considered: Scenario I – emissions decreasing 20% by 2050, Scenario II – future emissions remaining at the same level as at the end of the twentieth century, and Scenario III – emissions increasing 20% by 2050. The results showed that, due to increased temperatures, the average annual number of days with high O3 levels in the four selected cities could increase by more than 40–100% by the 2050s and 70–200% by the 2080s (from the current areal average of 8 days) under the three pollutant emission scenarios. The corresponding number of low O3 days could decrease by 4–10% and 5–15% (from the current areal average of 312 days). For the rest of the pollutants, future air pollution levels will depend on future pollutant emission levels. Under emission Scenarios II and III, the average annual number of high pollution days could increase 20–40% and 80–180%, respectively, by the middle and late part of this century. In contrast, under Scenario I, the average annual number of high pollution days could decrease by 10–65%.  相似文献   

14.
Purpose

To identify the sources and levels of contamination with anthropogenically derived heavy metals (HMs) for appropriate pollution control. We quantified anthropogenic influences with respect to HM pollution in soil, based on multiple pollution indices and cluster analysis derived from the results of an annual nationwide survey conducted in Korea.

Methods

Contamination levels of HMs in soils were quantitatively evaluated using multiple pollution indices: contamination factor (CF), geo-accumulation index (Igeo), Nemerow’s integrated pollution index (NIPI), and pollution load index (PLI). Hierarchical cluster analysis was conducted to elucidate the correlations between HMs and contamination sources. A total of 2214 HM concentration data including six contamination sources were used to evaluate the pollution state of anthropogenic effects of HMs.

Results

The CFs for Zn and Cu revealed a broad enrichment of these HMs in all pollution sources. Scrap recycling sites (SRS) had the highest likelihood of pollutant distribution in soil surfaces. NIPI and PLI varied with the extent of anthropogenic activities or land use, especially in SRS, waste disposal sites (WDS), transport maintenance sites (TMS), and industrial sites (INS), and anthropogenic sources were divided into three discrete clusters: INS-TMS-LDS (land development sites), SRS-WDS, and vicinities of industrial sites (VIS).

Conclusion

Our results confirmed that soil pollution indices combined with cluster analysis were useful to identify sources of anthropogenic HMs in urban soil, as well as to assess the levels of HM contamination.

  相似文献   

15.
重金属和有机污染物在修饰土中的吸附   总被引：13，自引：0，他引：13  
Sorption characteristics of both an organic pollutant （phenol） and a heavy metal （cadmium ion） on the clay layer of a Lou soil （Eum-orthic Anthrosol in Chinese Soil Taxonomy） along with the sorption mechanism were investigated using three soil treatments： modification with a cationic surfactant cetyltrimethylammonium bromide added at an amount equivalent to 50% and 100% of the soil CEC （50? and 100?）, modification with an amphoteric surface-modifying agent dodecyldimethylbetaine （commercially known as BS-12） added at an amount equivalent to 50% and 100% of the soil CEC （50% BS and 100%BS）, and an unmodified control （CK）. Results showed that the BS soil treatments increased sorption of both the heavy metal Cd^2＋ and the organic pollutant phenol. The equilibrium sorption amount of Cd^2＋ decreased in the order： 50%BS 〉 100%BS 〉 CK 〉 50? 〉 100?, with the BS soil treatments being about 1.3 to 1.8 times higher and the CB soil treatments about 23% to 41% lower than CK. Both the single-site and two-site Langmuir models could be applied to describe the sorption of Cd^2＋ in each soil treatment. The equilibrium sorption amount of phenol on the soil samples decreased in the order： 100? 〉 50? 〉 100%BS 〉 50%BS 〉 CK, with the CB soil treatments being 41.0 to 79.6 times higher and the BS soil treatments 4.0 to 8.3 times higher than CK. The Freundlich equation could also be used to describe the sorption characteristics of phenol. In the BS soil treatments, both an organophobic long carbon chain and hydrophilic charged groups resulted in a relatively strong sorption ability for both heavy metals and organic pollutants. In addition, the sorption ratio K, the ratio of phenol sorption amount of the modified soil to that of CK, increased initially and decreased later with the amount of phenol added, and the critical sorption ratio Kc, the peak value of the sorption ratio curve plotted against the added phenol concentration, was a good index for evaluating the sorption ability of phenol in the soil.  相似文献   

16.
Leaf analysis of peach (Prunus persica, L. Batsch) trees is restricted to midsummer (120 days after full bloom), which is the standard time for leaf sampling of fruit trees. In order to carry out foliar diagnosis in this plant at nonstandard times, reference values based on maximum yield exist for specific areas. When a diagnosis is applied with different objetives other reference values are needed. It may prove useful to bring forward the time when samples are taken. Samples taken 60 and 120 days after full bloom for two seasons, 1987 (using the late ripening cultivar “Calanda”; grafted on seedling) and 1992 (irrespective of cultivar or rootstock), were used to calculate the correlation between concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) present in leaves. The high significance gave rise to the following linear regression equations, which show the relationship between nutrients at the above mentioned times: N60days = 0.705N120 days + 1.557; P60days = 0.181P120days + 0.244; K60days = 0.444K120days + 1.303; Ca60days = 0.386Ca120days + 0.639; Mg60days = 0.386Mg120days + 0.233. If we take these equations as a basis and knowing the standard mineral content at 120 days, it should be possible to obtain reference values needed to interprete the analysis of peach leaf samples taken 60 days after full bloom. If we compare the interpretation of several samples, by means of the DOP index, we find a remarkable similarity between the experimental and calculated reference values. This could lead to a new method of early diagnosis of nutritional status.  相似文献   

17.
Sorption of methyl-parathion and carbaryl by an organo-bentonite   总被引：1，自引：0，他引：1  
The modification of bentonite clays by cetyltrimethylammonium bromide (CTMAB) surfactant via cation-exchange produces materials (“organo-clays”) with an increased capacity for sorbing organic compounds such as pesticides. The sorption from solutions of two nonionic pesticides, methyl-parathion and carbaryl, by an organo-bentonite has been investigated. The pesticides are partitioned into the surfactant. The distribution coefficients, K ss, show a strong dependence on surfactant loading of the bentonite. The surfactant configuration at the clay surface has a marked influence on the effective volume and density of the bound surfactant. At low surfactant loadings, the K ss values increased, reached a maximum, and then decreased as the extent of loading increased. At low loading levels, the surfactant appears to form a monolayer (organic film) that effectively adsorbs the pesticides, resulting in very high K ss values. At high loadings, the sorbed surfactant appears to form a bulk-like medium that behaves essentially as a distribution phase. As a result, the K ss values decreased appreciably, and became less dependent on the CTMAB loading. Moreover, when the surfactant concentration in water was greater than the critical micelle concentration, the surfactant uptake on the clay reaches a plateau and an increasing fraction of the micelles remain in solution, together with the pesticides which bound to them. The competition for the pesticides between the aqueous micelles and the sorbed surfactant leads to a decrease in distribution coefficients.  相似文献   

18.
Many persistent organic pollutants (POPs), notably hexachlorocyclohexanes (HCHs), chlorinated cyclodienes, and dichlorodiphenyltrichloroethanes (DDTs), remain in Japanese farming soils, more than 40 years after their use as insecticides was prohibited. In recent years, residues of chlorinated cyclodienes in cucurbit fruits have become a problem. But, though HCHs and DDTs have been staying in the soil, residues of these chemicals in crops have not been a problem. So we compared the fates of HCHs (α-, β-, γ-HCHs), chlorinated cyclodienes (dieldrin, endrin, heptachlor exo-epoxide), and DDTs (DDE, dichlorodiphenyldichloroethylene; DDD, dichlorodiphenyldichloroethane) in soil and investigated their uptake by several non-cucurbits and cucurbits. As for the fate of POPs in soil, not only the total concentrations but also the concentrations in soil solution as bioavailable POPs were determined. The half-lives of total β-HCH and DDTs in soil were the longest, and α- and γ-HCHs the shortest. On the other hand, the half-lives of bioavailable POPs ranged from 1/3 to 1/20 of those of total POPs. The ratio of the half-lives of bioavailable POPs to those of total POPs decreased in the order of HCHs > chlorinated cyclodienes > DDTs. Because hydrophobic chemicals were adsorbed strongly to the soil, the bioavailable POPs in soil are controlled by their hydrophobicity, indicated by the values of log K OW (K OW: n-octanol-water partition coefficient). The shoot concentrations of chlorinated cyclodienes and DDTs were higher in cucurbits than in non-cucurbits. However, among POP insecticides, HCHs did not show clear differences. As for the root concentrations, all tested POPs were higher in cucurbits than in non-cucurbits. Through the determination of POPs in soil solution, we could compare the abilities of plants to take up the chemicals using soil solution bioconcentration factors (BCFSS). The values of BCFSS increased with the magnitude of log K OW, in the order of HCHs < chlorinated cyclodienes < DDTs. In addition, BCFSS did not show marked differences among isomers or chemicals with similar structure. Therefore, plant uptake ability was influenced mainly by log K OW. After being applied to agricultural land, α- and γ-HCHs seemed to disappear quickly, β-HCH persisted longer but the uptake in roots was low because of the low log K OW, and DDTs also persisted longer but the bioavailability decreased rapidly in the soil because of their high log K OW. Chlorinated cyclodienes have remained in the soil and have remained available, because they are less likely than HCHs (except β-HCH) to disappear and less likely than DDTs to become adsorbed to the soil. In addition, their higher log K OW than that of HCHs makes them more easily taken up by roots. However, shoot concentrations were high only in cucurbits, for which they remain a problem in Japan.  相似文献   

19.
The interactive effects of salinity and potassium (K+) availability on biomass production, water status, and ionic composition were investigated in Hordeum maritimum, an annual grass growing natively on saline soils. Plants were grown for 7 weeks on Hewitt nutrient solution supplied with NaCl (0, 100, 150, 200, and 300 mM) combined with low (0.232 mM) or high (5.8 mM) K+ levels. Independent of potassium availability, dry matter of both roots and shoots decreased consistently with increasing NaCl levels in the culture medium, in association with a significant reduction of the shoot water content. This salt‐induced growth reduction did not result from a restriction of K+ nutrition, since H. maritimum expressed similar growth under both low and high K+ supply. NaCl decreased shoot K+ concentrations. This effect was more pronounced in plants grown at high K+ supply than in plants grown at low K+ supply. This result suggests that the absorption systems were strongly selective for K+, and that this selectivity was enhanced by salt.  相似文献   

20.
Nitrogen dioxide is an important gaseous air pollutant. It plays a major role in atmospheric chemistry, particularly in the formation of secondary air pollutants, and contributes to environmental acidification. A comprehensive assessment of NO2 levels in the atmosphere is required for developing effective strategies for control of air pollution and air quality improvement. Air pollution is a serious problem in all major cities of Pakistan and needs to be addressed to minimize detrimental effects on human health and urban vegetation. In this research, we focused on the monitoring of NO2 levels in the urban environment of Rawalpindi city. Because of the lack of expensive continuous sampling devices and to get a good spatial coverage of the NO2 concentrations in the study area, NO2 passive samplers were exposed at 42 different sites within the city limits of Rawalpindi from January to December, 2008. Samplers were exchanged every 10 days and the associated meteorological conditions like temperature, wind speed, rainfall and relative humidity were also monitored. The average NO2 concentration was found to be 27.46?±?0.32 ppb. The highest values of NO2 were measured near to main roads and educational institutions due to intense flow of road vehicles. Moreover, the study showed that the values obtained for NO2 for all sampling points exceeded the annual limit value set by World Health Organization. So, this is very important to take different steps to control this before it becomes a serious hazard for people living in those areas.  相似文献   

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