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1.
The present work discusses the startup and operation of different biotrickling filters during the simultaneous removal of NH3, H2S, and ethyl mercaptan (EM) for odor control, focusing on (a) the impact of pH control in the stability of the nitrification processes during reactor startup and (b) the crossed effects among selected pollutants and their by-products. Two biotrickling filters were packed with poplar wood chips (R1 and R2A), while a third reactor was packed with polyurethane foam (R2B). R2A and R2B presented a pH control system, whereas R1 did not. Loads of 2?C10?g N?CNH3 m?3?h?1, 5?C16?g S?CH2S m?3?h?1, and 1?C6?g EM m?3?h?1 were supplied to the bioreactors. The presence of a pH control loop in R2A and R2B proved to be crucial to avoid long startup periods and bioreactors malfunctioning due to biological activity inhibition. In addition, the impact of the presence of different concentrations of a series of N species (NH 4 + , NO 2 ? , and NO 3 ? ) and S species (SO 4 2? and S2?) on the performance of the two biotrickling filters was studied by increasing their load to the reactors. Sulfide oxidation proved to be the most resilient process, since it was not affected in any of the experiments, while nitrification and EM removal were severely affected. In particular, the latter was affected by SO 4 2? and NO 2 ? , while nitrification was significantly affected by NH 4 + . The biotrickling filter packed with polyurethane foam was more sensitive to crossed effects than the biotrickling filter packed with poplar wood chips.  相似文献   

2.
In the Vosges Mountains (NE of France), integrated plot-catchment studies have been carried out since 1985 in the Strengbach basin to study the influence of acid atmospheric inputs on surface water quality and element budgets. In this paper, available mid-term time series (1985–1991) have been considered to detect obvious trends, if any, in surface water chemistry and element budgets. Air quality data showed a slight decline for SO2, whereas NO2 slightly increased over the period, but these trends are not very significant. This is in agreement with increased N concentration (mainly as NH 4 + ) and with the stability of SO 4 2? in open field precipitation. Because of a significant decrease in rainfall amount over the period, only inputs of NH 4 + increased significantly whereas H+ and SO 4 2+ inputs declined. In spring and streamwaters, pH and dissolved Si concentration increased mainly as a result of a reduced flow. Na+, K+, Cl? and HCO-3~? concentrations remained stable whereas Ca2+, Mg2+ and SO 4 2+ concentrations declined significantly. Only NO 3 ? concentration increased significantly in springwaters. The catchment budgets revealed significant losses of base cations, Si and SO 4 2? . These losses decreased over the period. Nitrogen was retained in the ecosystem. However, a longer record is needed to determine whether or not changes in surface water chemistry have resulted from short-term flow reductions or long-term changes in input-output ion budgets. This is specially true with N because the decline in SO 4 2? output was accompanied by N accumulation.  相似文献   

3.
We evaluated the differences in the use of a quartz filter and a polytetrafluoroethylene (PTFE) filter as a first (F0)-stage filter in a four-stage filter-pack method. A four-stage filter-pack method can completely collect sulfur species (SO2 and SO 4 2? ), nitrate species (HNO3 and NO 3 ? ), and ammonium species (NH3 and NH 4 + ) with little or no leakage irrespectively of the first-stage filter used. On the other hand, a seasonal variation was observed in the efficiency of collection between the quartz filter and the PTFE filter depending on the material to be collected. There was no seasonal variation in the efficiency of collection in sulfur species; in contrast, a clear seasonal variation was observed for the nitrate and ammonium species. As for NO 3 ? , the PTFE filter was more vulnerable than the quartz filter at air temperatures below 21°C, while the quartz filter was more vulnerable than the PTFE filter at air temperatures exceeding 21°C. A similar vulnerability for air temperature was observed for NH 4 + , although the threshold air temperature was 23°C for NH 4 + . Consequently, the evaporation loss of NO 3 ? would be mainly attributable to the volatilization of NH4NO3, although it is also partially due to the volatilization of NH4Cl.  相似文献   

4.
The atmospheric deposition of air pollutants at a forest edge was studied by means of monitoring canopy throughfall at the edge and at five different parallel lines in the forest behind the edge. The investigation was carried out at a pine forest on the Swedish west coast. Throughfall and bulk deposition samples were analyzed for volume, SO 4 2? , NO 3 ? , Cl?, NH 4 + , Na+, K+, Mg2+, Ca2+, and for pH. The results show that the throughfall flow at the edge was increased substantially for most ions. The ratios in throughfall flows between the edge and the line 50 m into the forest were for SO 4 2? , 1.5, NO 3 ? 2.9, NH 4 + 2.7, and Na+ 3.1. Since this effect is not only valid for forest edges but also for hillsides, hilltops, and edges between stands of different age, etc., there might be substantial areas which get much larger total deposition than the normally considered closed forest.  相似文献   

5.
Schwikowski  M.  Novo  A.  Baltensperger  U.  Delmas  R.  Gäggeler  H. W.  Kasper  A.  Kuhn  M.  Maupetit  F.  Nickus  U.  Preunkert  S.  Puxbaum  H.  Rossi  G. C.  Schöner  W.  Wagenbach  D. 《Water, air, and soil pollution》1997,93(1-4):67-91
In order to investigate the seasonal and geographical distribution of snow concentrations anddeposition fluxes of environmentally relevant ionic species in the Alps, the international programSNOSP was initiated. In the framework of this program, intercomparisons of snow samplingtechniques and analytical methods to determine the ionic species C1-, NO 3 - ,SO 4 2- , K+, Na+, NH4 +, Mg2+, and Ca2+, as well as the pH and the specificconductivity were performed. The concentrations of these species in the snow samples collectedin the SNOSP program varied by orders of magnitude with, e.g., concentrations of NO 3 - , SO 4 2- , and NH4 + ranging from 0.2-60, 0.2-90, and 0.1-60 µeq L-1,respectively. The intercomparisons revealed a reasonable agreement of the determinations of thespecies Cl-, NO 3 - , SO 4 2- , Na+, and NH4 + in snow. Results were less satisfactory for K+, Mg2+, Ca2+,and H+, mainly due to the very low concentrations. In conclusion, recommendations areformulated for the reliable derivation of chemical inventories from snow packs.  相似文献   

6.
The chemical composition of snowmelt, groundwater, and streamwater was monitored during the spring of 1991 and 1992 in a 200-ha subalpine catchment on the western flank of the Rocky Mountains near Steamboat Springs, Colorado. Most of the snowmelt occurred during a one-month period annually that began in mid-May 1991 and mid-April 1992. The average water quality characteristics of individual sampling sites (meltwater, streamwater, and groundwater) were similar in 1991 and 1992. The major ions in meltwater were differentially eluted from the snowpack, and meltwater was dominated by Ca2+, SO 4 2? , and NO 3 ? . Groundwater and streamwater were dominated by weathering products, including Ca2+, HCO 3 ? (measured as alkalinity), and SiO2, and their concentrations decreased as snowmelt progressed. One well had extremely high NO 3 ? . concentrations, which were balanced by Ca2+ concentrations. For this well, hydrogen ion was hypothesized to be generated from nitrification in overlying soils, and subsequently exchanged with other cations, particularly Ca2+. Solute concentrations in streamwater also decreased as snowmelt progressed. Variations in groundwater levels and solute concentrations indicate that most of the meltwater traveled through the surficial materials. A mass balance for 1992 indicated that the watershed retained H+, NH 4 + , NO 3 ? , SO 4 2? and Cl? and was the primary source of base cations and other weathering products. Proportionally more SO 4 2? was deposited with the unusually high summer rainfall in 1992 compared to that released from snowmelt, whereas NO 3 ? was higher in snowmelt and Cl? was the same. The sum of snowmelt and rainfall could account for greater than 90% of the H+ and NH 4 + retained by the watershed and greater than 50% of the NO 3 ? .  相似文献   

7.
The study aimed to determine the influence of catchment characteristics and flood type on the relationship between streamflow and a number of chemical characteristics of streamwater. These were specific electrical conductivity (SC), pH, the concentrations of main ions (Ca2+, Mg2+, Na+, K+, HCO 3 ? , SO 4 2? , and Cl?), and nutrients (NH 4 + , NO 2 ? , NO 3 ? , and PO 4 3? ). These relationships were studied in three small catchments with different geological structure and land use. Several flood types were distinguished based on the factors that initiate flooding and specific conditions during events. Geological factors led to a lower SC and main ion concentrations at a given specific runoff in catchments built of resistant sandstone versus those built of less resistant sediments. A lower concentration of nutrients was detected in the semi-natural woodland catchment versus agricultural and mixed-use catchments, which are strongly impacted by human activity. The strongest correlation between streamflow and the chemical characteristics of water was found in the woodland catchment. Different types of floods were characterized by different ion concentrations. In the woodland catchment, higher SC and higher concentrations of most main ions were noted during storm-induced floods than during floods induced by prolonged rainfall. The opposite was true for the agricultural and mixed-use catchments. During snowmelt floods, SC, NO 3 ? , and most main ion concentrations were higher when the soil was unfrozen in the agricultural and mixed-use catchments versus when the soil was frozen. In the case of the remaining nutrients, lower concentrations of NH 4 + were detected during rain-induced floods than during snowmelt floods. The opposite was true of PO 4 3? .  相似文献   

8.
A simple method is presented and used to estimate the portions of SO inf4 sup2? and NO inf? sup3 that contribute to the strong acidity in weekly precipitation samples collected at three NADP sites in the eastern United States. The method assumes that, in general, the difference between SO inf4 sup2? and NH inf+ sup4 represents acidic sulfate and the difference between NO inf? sup3 and soil-derived materials (the sum of Ca2+, Mg2+, and K+) represents acidic nitrate. Acidic sulfate and nitrate are considered to be the predominant source of H+ (determined from laboratory pH) in the weekly precipitation samples. Most of the acidity for all three sites was attributed to acidic sulfate. The highest fraction of acidic SO inf4 sup2? to H+ wet deposition values was for the east-central Tennessee site (0.95) and the northeastern Illinois site (0.90), and the lowest fraction occurred at the central Pennsylvania site (0.75). The Tennessee site had the greatest acidic fraction of sulfate (0.84) and the Pennsylvania site had the greatest acidic fraction of nitrate (0.59).  相似文献   

9.
Ion mass and H+ budgets were calculated for three pristine forested catchments using bulk deposition, throughfall and runoff data. The catchments have different soil and forest type characteristics. A forest canopy filtering factor for each catchment was estimated for base cations, H+, Cl? and SO 4 2? by taking into account the specific filtering abilities of different stands based on the throughfall quality and the distribution of forest types. Output fluxes from the catchments were calculated from the quality and quantity of the runoff water. Deposition, weathering, ion exchange, retention and biological accumulation processes were taken into account to calculate catchment H+ budgets, and the ratio between external (anthropogenic) and internal H+ sources. In general, output exceeded input for Na+, K+, Ca2+, Mg2+, HCO 3 ? (if present) and A? (organic anions), whereas retention was observed in the case of H+, NH 4 + , NO 3 ? and SO 4 2? . The range in the annual input of H+ was 22.8–26.3 meq m?2 yr?1, and in the annual output, 0.3–3.9 meq m?2 yr?1. Compared with some forested sites located in high acid deposition areas in southern Scandinavia, Scotland and Canada, the catchments receive rather moderate loads of acidic deposition. The consumption of H+ was dominated by base cation exchange plus weathering reactions (41–79 %), and by the retention of SO 4 2? (17–49 %). The maximum net retention of SO 4 2? was 87% in the HietajÄrvi 2 catchment, having the highest proportion of peatlands. Nitrogen transformations played a rather minor role in the H+ budgets. The ratio between external and internal H+ sources (excluding net base cation uptake by forests) varied between 0.74 and 2.62, depending on catchment characteristics and acidic deposition loads. The impact of the acidic deposition was most evident for the southern Valkeakotinen catchment, where the anthropogenic acidification has been documented also by palaeolimnological methods.  相似文献   

10.
A long-term hydrological and water chemistry research was conducted in three experimental microbasins differing in land cover: (1) a purely agricultural fertilized microbasin, (2) a forested microbasin dominated by Carpinus betulus (European hornbeam), and (3) a forested microbasin dominated by Picea abies (L.) (Norway spruce). The dissolved inorganic nitrogen (DIN: NH 4 + , NO 2 ? , NO 3 ? ) budget was examined for a period of 3 years (1991–1993). Mean annual loads of DIN along with sulfate SO 4 2? and base cations Ca2+, Mg2+, Na+, K+, and HCO 3 ? were calculated from ion concentrations measured in stream water, open-area rainfall, throughfall (under tree canopy), and streamwater at the outlets from the microbasins. Comparison of the net imported/exported loads showed that the amount of NO 3 ? leached from the agricultural microbasin is ～3.7 times higher (43.57 kg ha?1?a?1) than that from the spruce dominated microbasin (11.86 kg ha?1?a?1), which is a markedly higher export of NO 3 ? compared to the hornbeam dominated site. Our analyses showed that land cover (tree species) and land use practices (fertilization in agriculture) may actively affect the retention and export of nutrients from the microbasins, and have a pronounce impact on the quality of streamwater. Sulfate export exceeded atmospheric rainfall inputs (measured as wet deposition) in all three microbasins, suggesting an additional dry depositions of SO 4 2? and geologic weathering.  相似文献   

11.

Purpose

Nitrate (NO 3 ? ) is often considered to be removed mainly through microbial respiratory denitrification coupled with carbon oxidation. Alternatively, NO 3 ? may be reduced by chemolithoautotrophic bacteria using sulfide as an electron donor. The aim of this study was to quantify the NO 3 ? reduction process with sulfide oxidation under different NO 3 ? input concentrations in river sediment.

Materials and methods

Under NO 3 ? input concentrations of 0.2 to 30?mM, flow-through reactors filled with river sediment from the Pearl River, China, were used to measure the processes of potential NO 3 ? reduction and sulfate (SO 4 2? ) production. Molecular biology analyses were conducted to study the microbial mechanisms involved.

Results and discussion

Simultaneous NO3 ? removal and SO4 2? production were observed with the different NO 3 ? concentrations in the sediment samples collected at different depths. Potentially, NO 3 ? removal reached 72 to 91?% and SO 4 2? production rates ranged from 0.196 to 0.903?mM?h?1. The potential NO 3 ? removal rates were linearly correlated to the NO 3 ? input concentrations. While the SO 4 2? production process became stable, the NO 3 ? reduction process was still a first-order reaction within the range of NO 3 ? input concentrations. With low NO 3 ? input concentrations, the NO 3 ? removal was mainly through the pathway of dissimilatory NO 3 ? reduction to NH 4 + , while with higher NO 3 ? concentrations the NO 3 ? removal was through the denitrification pathway.

Conclusions

While most of NO 3 ? in the sediment was reduced by denitrifying heterotrophs, sulfide-driven NO 3 ? reduction accounted for up to 26?% of the total NO 3 ? removal under lower NO 3 ? concentrations. The vertical distributions of NO 3 ? reduction and SO 4 2? production processes were different because of the variable bacterial communities with depth.  相似文献   

12.
The Nandong Underground River System (NURS) is located in Southeast Yunnan Province, China. Groundwater in NURS plays a critical role in socio-economical development of the region. However, with the rapid increase of population in recent years, groundwater quality has degraded greatly. In this study, the analysis of 36 groundwater samples collected from springs in both rain and dry seasons shows significant spatial disparities and slight seasonal variations of major element concentrations in the groundwater. In addition, results from factor analysis indicate that NO 3 ? , Cl?, SO 4 2? , Na+, K+, and EC in the groundwater are mainly from the sources related to human activities while Ca2+, Mg2+, HCO 3 ? , and pH are primarily controlled by water–rock interactions in karst system with Ca2+ and HCO 3 ? somewhat from anthropogenic inputs. With the increased anthropogenic contaminations, the groundwater chemistry changes widely from Ca-HCO3 or Ca (Mg)-HCO3 type to Ca-Cl (+NO3) or Ca (Mg)-Cl (+NO3), and Ca-Cl (+NO3+SO4) or Ca (Mg)-Cl (+NO3+SO4) type. Concentrations of NO 3 ? , Cl?, SO 4 2? , Na+, and K+ generally show an indistinct grouping with respect to land use types, with very high concentrations observed in the groundwater from residential and agricultural areas. This suggests that those ions are mainly derived from sewage effluents and fertilizers. No specific land use control on the Mg2+ ion distribution is observed, suggesting Mg2+ is originated from natural dissolution of carbonate rocks. The distribution of Ca2+ and HCO 3 ? does not show any distinct land use control either, except for the samples from residential zones, suggesting the Ca2+ and HCO 3 - mainly come from both natural dissolution of carbonate rocks and sewage effluents.  相似文献   

13.
More than 1400 precipitation samples were collected weekly from 5 sites in Nova Scotia between 1978 and 1987. High concentrations of H+, non-marine SO inf4 sup= (*SO4) and NO inf3 sup- were observed in 1978 and 1986. In 1983, concentrations of all three parameters were the lowest in the data record. Fluctuations in emissions for SO2 are insufficient to account for the variability observed in concentration and deposition values. Mean annual concentrations in 1983 were 13, 16, and 6 ueq L-1 for H+, *SO4, and NO inf3 sup- , respectively. In 1986 the values were 35, 28, and 13 ueq L-1. Concentrations in 1978 were 31, 38, and 16 ueq L-1. Average pH of precipitation was 4.61 during the 10 yr study. The two most acidic years were 1979 (4.47) and 1986 (4.46). In 1983, the average pH was 4.89. The ratio (equivalents) of NO inf3 sup- to *SO4 was 0.41, so most acidity in the precipitation results from H2SO4 However, multiple regression analysis revealed that H+ is more sensitive to changes in NO3-concentrations than *SO4. Ratios of summer (JJA) vs winter (JFM) average concentrations were examined. During summer months, *SO4 and H+ were 1.8 times winter values. Summer to winter ratios for NO inf3 sup- and NH inf4 sup+ were 1.4 and 2.5, respectively.  相似文献   

14.
The fluxes of N–NO 3 ? , N–NH 4 + , S–SO 4 2? , Na+, K+, Ca2+ and Mg2+ from bulk precipitation to throughfall, stemflow and soil water surface flows were studied during 1999–2003 in planted Norway spruce forest stands of different ages (11, 24, 91 and 116 years in 1999). Also, runoff from the corresponding Potok Dupniański Catchment in the Silesian Beskid Mts was studied. N deposition was above the critical load for coniferous trees. The interception increased with stand age as well as leaf area index and so did the leaching from the canopy of almost all the analysed elements, but especially S–SO 4 2? , H+ and K+. The nutrient fluxes varied with age of the spruce stands. Throughfall showed a high amount of S and of the strong acids (S–SO 4 2? and N–NO 3 ? ) deposited to the soil, especially in older spruce age classes. Decomposition of organic matter caused a rise in water acidity and an increase in the concentrations of all the analysed ions; the leaching of minerals, however, was low (under 1%). The horizontal soil water flow showed an increase in the amount of water and amount of ions and contributed to a further decrease of pH at the soil depth of 20 cm. Element concentrations and their amounts increased with water penetrating vertically and horizontally on the slopes. Considerable amounts of ions, especially S and alkaline cations, were carried beyond the reach of the root system and then left the catchment. In the long term, these mineral losses will adversely affect health and growth of the spruce stands, and the increased acidity with stand age will presumably have negative effects on the runoff water ecosystem.  相似文献   

15.
Many bryophytes rely to a large extent on atmospheric deposition for their nutrient uptake.However, increasing levels of atmospheric ammonium NH 4 + and nitrate NO 3 - attract concern as to the possible harmful effects onbryophytes from these two nutrient sources. Changes in nitrate reductase (NR) activities, cation(Ca, K and Mg), total nitrogen (N) and organic acid concentrations were investigated for themosses, Racomitrium lanuginosum, Rytidiadelphus loreus and Philonotis fontana, in response to asingle field misting with 3 mol m-3 NH 4 + and NO 3 - . Increases of 20% were recordedfor tissue N content, 48 hr after misting with N containing solutions. When labelled NH 4 + or NO 3 - were applied to R. Lanuginosum at 1, 3 and 6mol m-3 concentrations, partitioning ofincorporated 15N between different tissueregions occured, with the highest N uptake in the upper stem and leaves. High concentrations ofapplied N resulted in reduced efficiency of N uptake. NH 4 + applications caused declines in NR activities, organic acidsand cations, whereas, NO 3 - treatments causedthe reverse response. Changes in cation contents, organic acids and NR activity reflect short-termregulation of N metabolism in the presence of defined N sources, as well as potential mechanismsof regulating cell pH homoeostasis. The consistency of physiological responses, especially NRactivities, over short-term pollution episodes, provides evidence for their use as indicators of both NH 4 + and NO 3 - pollution.  相似文献   

16.
A constructed wetland composed of a pond- and a marsh-type wetland was employed to remove nitrogen (N) and phosphorus (P) from effluent of a secondary wastewater treatment plant in Korea. Nutrient concentrations in inflow water and outflow water were monitored around 50 times over a 1-year period. To simulate N and P dynamics in a pond- and a marsh-type wetland, mesocosm experiments were conducted. In the field monitoring, ammonium (NH 4 + ) decreased from 4.6 to 1.7 mg L?1, nitrate (NO 3 ? ) decreased from 6.8 to 5.3 mg L?1, total N (TN) decreased from 14.6 to 10.1 mg L?1, and total P (TP) decreased from 1.6 to 1.1 mg L?1. Average removal efficiencies (loading basis) for NO 3 ? , NH 4 + , TN, and TP were over 70%. Of the environmental variables we considered, water temperature exhibited significant positive correlations with removal rates for the nutrients except for NH 4 + . Results from mesocosm experiments indicated that NH 4 + was removed similarly in both pond- and marsh-type mesocosms within 1 day, but that NO 3 ? was removed more efficiently in marsh-type mesocosms, which required a longer retention time (2?C4 days). Phosphorus was significantly removed similarly in both pond- and marsh-type mesocosms within 1 day. Based on the results, we infer that wetland system composed of a pond- and a marsh-type wetland consecutively can enhance nutrient removal efficiency compared with mono-type wetland. The reason is that removal of NH 4 + and P can be maximized in the pond while NO 3 ? requiring longer retention time can be removed through both pond and marsh. Overall results of this study suggest that a constructed wetland composed of a pond- and a marsh-type wetland is highly effective for the removal of N and P from effluents of a secondary wastewater treatment plant.  相似文献   

17.
Data from two national precipitation chemistry monitoring networks, and several regional air and precipitation chemistry networks are used to describe some broad-scale features of acidic deposition in eastern North America. In northeastern North America, the coefficient of variation is shown to increase from 10–16% for annual averages to nearly 100% for daily values. There is a strong annual cycle in H+, SO inf4 sup= and NH inf4 sup+ deposition and some of the other ions although these cycles are not all in phase. The wet NO inf3 sup? deposition contributes relatively more than SO inf4 sup= to the acidity of snow as compared to rain. Wet deposition is highly “episodic” with about 50% to 70% of the total annual deposition of SO inf4 sup= and NO inf3 sup? accumulating in the highest 20% of the days. Estimates made in various ways indicate that, over eastern North America as a whole, dry deposition is approximately equal to wet for both SO inf4 sup= and NO inf3 sup? . Dry may exceed wet in the high emissions zone but drops to about 20% of the total deposition in more remote areas. Deposition via fog or low cloud impaction is an important input to high elevation forests, but more data are required to quantify the magnitude and regional extent of this.  相似文献   

18.
At Lange Bramke (Harz) soil solution and runoff concentrations of major elements were observed over 16 yr. During this period acid deposition was high but showed a marked decrease of H+ and SO 4 2? both in concentrations and fluxes over the last five years. Among others, this record reveals the following patterns: seasonality in the signals for SO 4 2? and NO 3 ? in runoff which are synchronous; an accumulation of SO 4 2? in the soil, initially up to 50% of the deposition fluxes; apparently no correlation between runoff and SO 4 2? concentration, and no long-term trend in runoff concentration of SO 4 2? . In this paper we use these patterns in the data set from Lange Bramke to test two established acidification models. The test criterion is that the algorithms employed by the SO 4 2? modules of these models must be able to reproduce these features. To that end, both models need not to be run as it can be shown that even with completely unrestricted parameter values the two algorithms are unable to match the observed SO 4 2? dynamics. The MAGIC model (Cosbyet al., 1985) is unable to reproduce, given the existence of net SO 4 2? accumulation, the constant SO 4 2? concentration in runoff during the last 16 years. The second model, BEM (Prenzel, 1986), is succesful in reconstructing the constant SC>4~ levels in runoff. However, on a monthly time scale BEM predicts a shift between the periodic maximum concentrations of SO 4 2? and NO 3 ? which is not observed in the data.  相似文献   

19.
Nitrogenous air pollutants including nitrogen dioxide (NO2), nitric acid (HNO3), nitrate (NO 3 ? ), ammonia (NH3), ammonium (NH 4 + ), and nitrous acid (HONO) were characterized at an urban forested (UF) site in Hiroshima and at a suburban forested (SF) site in Fukuoka, western Japan, using an annular denuder system for 1?year from May 2006 to May 2007 to compare the concentrations and chemical species of atmospheric nitrogenous pollutants between UF and SF sites. The proximity of the urban area was reflected in higher NO2 concentrations at the UF site than at the SF site. NO2 was more oxidized at the SF site because it is farther from an urban area than the UF site, which was reflected in higher concentrations of HNO3 at the SF site than the UF site. HNO3 and acidic sulfate is neutralized by NH3, existing as ammonium nitrate (NH4NO3) and ammonium sulfate [(NH4)2SO4] at the UF site. At the SF site, acidic sulfate is neutralized by NH3, existing as (NH4)2SO4, but NH4NO3, had scarcely formed at the SF site. A much higher HONO concentration was observed at the UF site than at the SF site, especially in winter and spring at night, which could be explained by higher NO2 concentrations at the UF site because of its proximity to an urban area and stagnant meteorological conditions. Atmospheric HONO determination was critical in evaluating the possibility of damage to trees in UF areas.  相似文献   

20.
Precipitation chemistry data were collected at 8 sites in the western part of the Netherlands over a period of 151/2 yr. Using specially-designed wind direction-dependent rain collectors, it is demonstrated that levels of ion constituents in rain water vary with wind direction, which can be assigned to different sources of contamination. The strongest variation was measured for Na+. As expected, trajectories over sea contributed most. Continental sources slightly reduced the variation for Cl? and Mg2+. For both NH inf4 sup+ and excess SO inf4 sup2? , maxima were found in southeasterly rainfall. It is assumed that polluted air from the large industrial Ruhr Area crosses a region with strong NH3 emissions in the Southeast of the Netherlands. The presence of ammonium sulfate was suggested. Minor variations were measured for NO inf3 sup? (due to diffusely-spread emissions and possible sampling artefact) and for H+ and Ca2+ (dry-deposition effects). Over the period 1973–1987 excess-SO inf4 sup2? levels decreased significantly (?3.3% yr?1, p<0.01) which is consistent with reduced S emission in Western Europe. Over the last decade an upward trend in NO inf3 sup? levels has been observed (3.2% yr?1, p<0.05) which is possibly related to the increased usage of cars.  相似文献   

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