The influence of highway traffic on ambient nitrogen dioxide concentrations beyond the immediate vicinity of highways

The objective of these analyses was to determine whether highways significantly influence ambient concentrations of NO₂ at distances greater than 200 m. NO₂ was sampled for 14 consecutive days in May 2003 at 67 sites across Montréal, Canada. The association between logarithmic concentrations of NO₂ and land-use variables was assessed using multiple regressions. Locations less than 100 m from the nearest highways were excluded, leaving 61 data points. Then, locations less than 200 m were excluded, leaving 55 data points. Excluding sampling locations located less than 100 or 200 m from the nearest highway did not substantially change the regression parameters. NO₂ was still significantly associated with both the distance from nearest highway and the traffic count on the nearest highway. These findings indicate that the negative association found between distance from highways and NO₂ concentration in several land-use regression studies in Europe and North America was not generated solely by the high concentrations found in the immediate vicinity of highways.     

Effects of nitrogen dioxide on biochemical and physiological characteristics of soybean

One month old soybean (Glycine max (L.) Merrill) cv. 'Williams' plants were exposed to nitrogen dioxide (NO2 at 0.1, 0.2, 0.3, and 0.5 microl liter(-1) and carbon filtered air (control), 7 h per day for five days, under controlled environment. Data were collected on net photosynthetic rate (PN), stomatal resistance (SR), and dark respiration rate (DR), immediately following the fifth day of exposure and 24 h after termination of exposure. Chlorophyll a (Ch a), chlorophyll b (Ch b), total chlorophyll (tot Ch) and foliar nitrogen (N) were measured before and after exposures. Growth characteristics--relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), and root shoot ratio (RSR) -- were computed for treated plants using standard growth equations. Increases of 18% and 23% in PN were observed immediately following exposure to 0.2 microl liter(-1) NO2 and after 24 h recovery period, respectively. With 0.5 microl liter(-1) NO2 treatment, reductions in PN of 23% and 50% were observed, immediately after exposure and following 24 h recovery, respectively. DR rates with 0.2 l liter(-1) treatment were higher than the control. Chlorophyll a and tot Ch showed significant reduction with 0.5 microl liter(-1) NO2 treatment. The percent reduction in Ch a and tot Ch with 0.5 microl liter(-1) NO2 were 45% and 47%, respectively. Increases in foliar nitrogen content after 0.2 and 0.3 microl liter(-1) NO2 treatments were 46% and 69%, respectively. Nitrogen dioxide at 0.5 microl liter(-1) reduced RGR and NAR by 47% and 51%, respectively. Leaf area ratio was 42% higher in 0.5 microl liter(-)1 NO2 treated plants, compared with the control; this increase was insufficient to compensate for the decrease in NAR resulting in a net decline in RGR. Nitrogen dioxide up to 0.2 microl liter(-1) increased PN and foliar-N content of soybean. With 0.5 microl liter(-1) NO2, significant decreases were observed in PN, leaf chlorophyll, foliar-N, NAR and RGR. Nitrogen dioxide up to 0.2 microl liter(-)1 has a favorable influence on overall growth characteristics of soybean; however, inhibitory effects were seen with NO2 treatment at 0.5 microl liter(-1).     

Effects of rural roadside levels of nitrogen dioxide on Polytrichum formosum Hedw

Polytrichum formosum Hedw. was exposed to 60 nl litre(-1) (122.4 microm(-3)) NO2 for 37 weeks in a closed chamber fumigation system. This concentration was chosen to simulate roadside levels in rural areas. Over an initial winter period (October-January) growth of existing shoots was stimulated by NO2. When new growth was recorded in April and May, NO2 pollution over winter and spring had resulted in a 36% reduction in new (< 1 cm) shoot production, and a 46% reduction in old shoots showing new growth. It is concluded that plants of Polytrichum formosum Hedw. growing near to roads may be adversely affected by NO2 pollution. Adverse effects of NO2 on plants and possible synergistic effects with other pollutants could cause growth reductions in sensitive species, thus affecting species composition of roadside vegetation.     

Integrated analysis of the effects of agricultural management on nitrogen fluxes at landscape scale

The integrated modelling system INITIATOR was applied to a landscape in the northern part of the Netherlands to assess current nitrogen fluxes to air and water and the impact of various agricultural measures on these fluxes, using spatially explicit input data on animal numbers, land use, agricultural management, meteorology and soil. Average model results on NH₃ deposition and N concentrations in surface water appear to be comparable to observations, but the deviation can be large at local scale, despite the use of high resolution data. Evaluated measures include: air scrubbers reducing NH₃ emissions from poultry and pig housing systems, low protein feeding, reduced fertilizer amounts and low-emission stables for cattle. Low protein feeding and restrictive fertilizer application had the largest effect on both N inputs and N losses, resulting in N deposition reductions on Natura 2000 sites of 10% and 12%, respectively.     

A land use regression model for predicting ambient concentrations of nitrogen dioxide in Hamilton, Ontario, Canada

This paper reports on the development of a land use regression (LUR) model for predicting the intraurban variation of traffic-related air pollution in Hamilton, Ontario, Canada, an industrial city at the western end of Lake Ontario. Although land use regression has been increasingly used to characterize exposure gradients within cities, research to date has yet to test whether this method can produce reliable estimates in an industrialized location. Ambient concentrations of nitrogen dioxide (NO2) were measured for a 2-week period in October 2002 at > 100 locations across the city and subsequently at 30 of these locations in May 2004 to assess seasonal effects. Predictor variables were derived for land use types, transportation, demography, and physical geography using geographic information systems. The LUR model explained 76% of the variation in NO2. Traffic density, proximity to a highway, and industrial land use were all positively correlated with NO2 concentrations, whereas open land use and distance from the lake were negatively correlated with NO2. Locations downwind of a major highway resulted in higher NO2 levels. Cross-validation of the results confirmed model stability over different seasons. Our findings demonstrate that land use regression can effectively predict NO2 variation at the intraurban scale in an industrial setting. Models predicting exposure within smaller areas may lead to improved detection of health effects in epidemiologic studies.     

Effects of nitrogen dioxide on leaf chlorophyll and nitrogen content of soybean

One-month-old soybean (Glycine max [L.] Merrill), cultivar 'Williams', plants were exposed to nitrogen dioxide (0.1, 0.2, 0.3 and 0.5 ppm) and carbon filtered air (control), 7 h per day, for 5 days, under a controlled environment. Leaf chlorophyll content (Ch a, Ch b, and total Ch content) and foliar nitrogen content (%N) were determined before and after the exposure. The influence of NO(2) treatments up to 0.3 ppm on leaf chlorophyll content was negligible although a stimulatory effect was evident in Ch a and total Ch content with 0.2 ppm NO(2). Marked decline in Ch content was observed with 0.5 ppm treatment; the reductions in Ch a and total Ch were 45% and 47%, respectively. Foliar-N contents of plants treated with 0.2 and 0.3 ppm NO(2) were higher than the control; plants exposed to 0.5 ppm NO(2) showed a 41% reduction in foliar-N compared to pre-exposure values.     

Modeling analyses of the effects of changes in nitrogen oxides emissions from the electric power sector on ozone levels in the eastern United States

In this paper, we examine the changes in ambient ozone concentrations simulated by the Community Multiscale Air Quality (CMAQ) model for summer 2002 under three different nitrogen oxides (NOx) emission scenarios. Two emission scenarios represent best estimates of 2002 and 2004 emissions; they allow assessment of the impact of the NOx emissions reductions imposed on the utility sector by the NOx State Implementation Plan (SIP) Call. The third scenario represents a hypothetical rendering of what NOx emissions would have been in 2002 if no emission controls had been imposed on the utility sector. Examination of the modeled median and 95th percentile daily maximum 8-hr average ozone concentrations reveals that median ozone levels estimated for the 2004 emission scenario were less than those modeled for 2002 in the region most affected by the NOx SIP Call. Comparison of the "no-control" with the "2002" scenario revealed that ozone concentrations would have been much higher in much of the eastern United States if the utility sector had not implemented NOx emission controls; exceptions occurred in the immediate vicinity of major point sources where increased NO titration tends to lower ozone levels.     

Effects of geographical location and land use on atmospheric deposition of nitrogen in the State of Connecticut

A network of eight monitoring stations was established to study the atmospheric nitrogen concentration and deposition in the State of Connecticut. The stations were classified into urban, rural, coastal and inland categories to represent the geographical location and land use characteristics surrounding the monitoring sites. Nitrogen species including nitrate, ammonium, nitric acid vapor and organic nitrogen in the air and precipitation were collected, analyzed and used to infer nitrogen concentrations and dry and wet deposition flux densities for the sampling period from 1997 through 1999, with independently collected meteorological data. Statistical analyses were conducted to evaluate the spatial variations of atmospheric concentration and deposition fluxes of total nitrogen in Connecticut. A slightly higher atmospheric concentration of total nitrogen was observed along the Connecticut coastline of Long Island Sound compared to inland areas, while the differences of nitrogen deposition fluxes were insignificant between coastal and inland sites. The land use characteristics surrounding the monitoring sites had profound effects on the atmospheric nitrogen concentration and dry deposition flux. The ambient nitrogen concentration over the four urban sites was averaged 38.9% higher than that over the rural sites, resulting a 58.0% higher dry deposition flux in these sites compared to their rural counterparts. The local industrial activities and traffic emissions of nitrogen at urban areas had significant effects on the spatial distribution of atmospheric nitrogen concentration and dry deposition flux in the State. Wet and total deposition fluxes appeared to be invariant between the monitoring sites, except for high flux densities measured at Old Greenwich, a monitoring station near to and downwind of the New York and New Jersey industrial complexes.     

The effects of selected NOx reduction scenarios on long-term nitrogen deposition and episodic ozone levels in Europe

For computational reasons, evaluations of NO(x) emission controls usually concentrate on either episodic or annual impacts on pollution or deposition levels. However, previously published model results indicate that the consequences of NO(x) controls can be quite different on these different time scales. In this paper we analyse the impact of a consistent set of NO(x) control scenarios on both the episodic and annual time-scales. Using similar models, we compute levels of episode peak O(3) and NO(2) and annual NO(y)-N and total N deposition at three locations in Europe due to six emission scenarios derived from OECD estimates. An NO(x) control scenario which reduces European emissions by 63%, only results in total annual N deposition reductions of 19, 36 and 26% at the three locations examined because of the influence of ammonia-nitrogen deposition. The same scenario results in either increases or decreases in episode peak O(3) due to the influence of hydrocarbons. Emission reduction strategies should take into account not only NO(x) emissions, but emissions of other pollutants, such as hydrocarbons and ammonia.     

The effects of prior exposure to sulphur dioxide and nitrogen dioxide on the water relations of timothy grass (Phleum pratense) under drought conditions

Studies of the growth and water relations of the grass Phleum pratense L. (Timothy) were made after simultaneous exposure to SO(2) and NO(2) at concentrations ranging from 80 + 57.4 microg m(-3) to 240 + 172.2 microg m(-3) (SO(2) + NO(2)). Decreased partitioning to the roots was evident during exposure to the pollutants, but when the plants were returned to clean air restrictions in root growth did not persist. Shoot to root partitioning was, however, complicated by the additional factor of changes in the nutritional status of the soil after additional columns of fresh soil were attached to the original tubes. The rate of use of soil water was nevertheless substantially increased by the pollution treatment and after a period of 23 days in which water was withheld, a clear pollution x water stress interaction was seen. The ability of polluted leaves to conserve water under severe water stress was tested by excising the leaves and measuring their water loss over time. The results from this second experiment showed that conservation of water by the leaves was appreciably affected after exposure to 80 + 57.4 microg m(-3) or 133.3 + 95.6 microg m(-3) SO(2) + NO(2). It seems likely that damage to the cells in the epidermal layer, leading to malfunctioning of stomata, is mainly responsible for the reduced ability to conserve water under conditions of extreme stress.     

Impact of microenvironmental nitrogen dioxide concentrations on personal exposures in Australia

Indoor and outdoor NO2 concentrations were measured and compared with simultaneously measured personal exposures of 57 office workers in Brisbane, Australia. House characteristics and activity patterns were used to determine the impacts of these factors on personal exposure. Indoor NO2 levels and the presence of a gas range in the home were significantly associated with personal exposure. The time-weighted average of personal exposure was estimated using NO2 measurements in indoor home, indoor workplace, and outdoor home levels. The estimated personal exposures were closely correlated, but they significantly underestimated the measured personal exposures. Multiple regression analysis using other nonmeasured microenvironments indicated the importance of transportation in personal exposure models. The contribution of transportation to the error of prediction of personal exposure was confirmed in the regression analysis using the multinational study database.     

The effects of elevated carbon dioxide levels on a Vibrio sp. isolated from the deep-sea

Introduction

The effect of oceanic CO₂ sequestration was examined exposing a deep-sea bacterium identified as Vibrio alginolyticus (9NA) to elevated levels of carbon dioxide and monitoring its growth at 2,750 psi (1,846 m depth).

Findings

The wild-type strain of 9NA could not grow in acidified marine broth below a pH of 5. The pH of marine broth did not drop below this level until at least 20.8 mM of CO₂ was injected into the medium. 9NA did not grow at this CO₂ concentration or higher concentrations (31.2 and 41.6 mM) for at least 72 h. Carbon dioxide at 10.4 mM also inhibited growth, but the bacterium was able to recover and grow. Exposure to CO₂ caused the cell to undergo a morphological change and form a dimple-like structure. The membrane was also damaged but with no protein leakage.     

Detecting and characterising small changes in urban nitrogen dioxide concentrations

Detecting and quantifying abnormal changes in the concentration of urban air pollutants can be difficult due to the influence of meteorology and atmospheric chemistry. This study presents methods to detect and characterise small changes in the concentration of nitrogen dioxide (NO₂) that deviate from expected behaviour. Generalized additive models (GAMs) are used to describe daily mean NO₂ concentrations at roadside monitoring sites to determine how concentrations deviate from measured concentrations. Structural change methods are applied to time series describing this difference to identify change-points, where concentrations of NO₂ deviate significantly from expected behaviour. Methods are also used which quantify the timing and uncertainty associated in the timing of these change-points. For most time series data considered in London, concentrations of NO₂ underwent relatively abrupt changes rather than smoothly varying increases; changes which remain largely undetected in raw time series data. Most change-points occurred in late 2002 or early 2003, and the factors, which may have contributed to them, are discussed. These methods can also identify technical problems with monitoring equipment and are applicable to other instances where detecting sudden atmospheric composition change is important.     

Effects of sulphur dioxide and nitrogen dioxide, singly and in mixture, on the macroscopic growth of three birch clones

An investigation of some aspects of the effects of low concentrations of the gases, sulphur dioxide and nitrogen dioxide, singly and in mixture, was made on the growth of three birch clones, two of Betula pendula Roth. (silver birch) and one of Betula pubescens Ehr. (downy birch). Comparative measurements of the growth form and dry mass increment were made over one year in glasshouses supplied with charcoal-filtered ambient air, and SO(2) and NO(2), singly or in mixture, at mean concentrations of 62 ppb (nl litre (-1)) of one or both gases. The main effects were found in those plants that were fumigated with SO(2) singly, and SO(2) and NO(2) together. Both treatments induced premature leaf loss and reduction in mass, especially of roots, the effects increasing over time. The heights and initial leaf areas were maintained, apparently at the expense of other parameters. NO(2), if present singly, had little or no effect, but it tended to enhance the damaging effect of SO(2) when the two were applied together. The different clones showed different degrees of response to the pollutants, but these differences became less marked during the second season of fumigation. The effects found are discussed in relation to the annual growth of trees, particularly birch.     

Increasing concentrations of nitrogen dioxide pollution in rural Wales

Monitoring of nitrogen dioxide pollution was carried out in rural environments throughout Wales during a 1-year survey to quantify any changes in background concentrations and distribution of the pollutant since an earlier survey in 1986. There were 23 sites in the present survey of which 16 had been monitored during the 1986 survey. The remaining 7 sites were based on moorland in mid-Wales within map squares for which critical loads for soil acidification are expected to be exceeded by the year 2005. All sites were chosen so as to be remote from major local sources of NO(2) and the values obtained were deemed to be minimum concentrations for the different regions. Measurements were made using diffusion tubes which aimed to provide mean concentrations of NO(2) for 2-week exposure periods. Concentrations of NO(2) were found to be higher in the winter months for most sites and this is probably related to a greater use of fossil fuels for heating buildings at this time of year. The exception was the high concentrations of NO(2) in May and June for several sites in North Wales, and in July and August for a site on Mount Snowdon. These high summer concentrations in North Wales are thought to be related to increased traffic associated with tourism. It is apparent that there has been a substantial increase in rural concentrations of NO(2) throughout Wales since the earlier survey of 1986. As an average of all 16 sites used in both surveys, there was a 53% increase in the annual mean concentration of NO(2). Also, it is evident that, since 1986, there has been a substantial increase in the area of south-eastern Wales which has a background level in excess of 10 ppb NO(2) and a notable reduction in land area with concentrations below 6 ppb NO(2) as an annual mean concentration. The possible future impact of increasing rural concentrations of NO(2) on Welsh vegetation is discussed with references to estimates of critical levels of NO(2) for adverse effects on plants.     

Sources and concentrations of indoor nitrogen dioxide in Barcelona, Spain

Sources and concentrations of indoor nitrogen dioxide (NO2) were examined in Barcelona, Spain, during 1996-1999. A total of 340 dwellings of infants participating in a hospital-based cohort study were selected from different areas of the city. Passive filter badges were used for indoor NO2 measurement over 7-30 days. Dwelling inhabitants completed a questionnaire on housing characteristics and smoking habits. Data on outdoor NO2 concentrations were available for the entire period of the study in the areas of the city where indoor concentrations were determined. Bivariate analysis was performed to investigate relationships between indoor NO2 concentrations on one hand and outdoor NO2 concentrations, housing, and occupant characteristics on the other. Stepwise multiple linear regression was performed with variables that were found to have a significant bivariate relationship. Indoor NO2 mean values ranged between 23.57 ppb in 1996 and 27.02 ppb in 1999, with the highest yearly value of 27.82 ppb in 1997. In the same time period, mean outdoor NO2 concentration ranged between 25.26 and 25.78 ppb with a peak of 30.5 ppb in 1998. Multiple regression analysis showed that principal sources of indoor NO2 concentrations were the use of a gas cooker, the absence of an extractor fan when cooking, and cigarette smoking. The absence of central heating was also associated with higher NO2 concentrations. Finally, each ppb increase in outdoor NO2 was associated with a 1% increase in indoor concentrations.     

The nitration of pyrene adsorbed on silica particles by nitrogen dioxide

Conversion of NO2, HNO2 gas, their mixture and a mixed gas of HNO2 and HNO3 on silica particles was investigated under simulated atmospheric conditions. Both HNO2 and HNO3 were detected as the products from conversion of NO2 on silica particles. However, unlike HNO3, which increased with conversion time, HNO2 underwent an increase-decrease time course due to the increased HNO3 further transformed HNO2 into NO+ on silica particles. Considering the catalytic effect of HNO3 and HNO2 on the nitration of pyrene adsorbed on silica particles by NO2, another electrophilic nitration path, analogous to the one that we previously reported, with NONO2+ and NON2O4+ as electrophiles was suggested. The two paths together gave an appropriate explanation for the catalytic effect of HNO2, HNO3 and their mixed gas on the nitration of the adsorbed pyrene by NO2.     

Monitoring of ambient air PCDD/F levels in Portugal

As part of a monitoring program conducted by IDAD--Institute for Environment and Development and supported by regional municipal solid waste (MSW) management authorities, dioxin concentrations in ambient air were measured in three regions of Portugal: Porto, Lisbon and Madeira. These independent studies were performed with the intention of providing data as a basis for the evaluation of potential impacts of the operation of recently built MSW incinerators. Thus, 170 samples were collected in nine different sites from January 1999 till present. The measured levels revealed an extremely variable content of PCDDs/PCDFs depending both on the area and the season of the year. Samples taken in Porto and Lisbon reveal a similar homologue structure even if concentrations measured in the Porto region are significantly greater. Data from Madeira is characteristic of a remote site with some of the congeners concentrations below the detection limit.     

Response of spinach and kidney bean plants to nitrogen dioxide

Different responses of spinach and kidney bean plants to various concentrations of NO(2) in the light and in the dark were shown. Spinach is more resistant than NO(2) than kidney bean. It is not only due to its greater tolerance to NO(2)(-) accumulated in leaves, but also to its stronger ability to metabolize NO(2)(-). The injury of spinach induced by the exposure to high concentration NO(2) in the light was not caused by the accumulation of NO(2)(-), but concerned the large amount of accumulated NH(3). The primary causes of NH(3) accumulation were that the activity of nitrite reductase was not affected by the fumigation on the one hand, and the activities of glutamine synthetase and glutamate synthase were inhibited on the other.