Estimation of S and NOx-N deposition budgets for the United States and Canada

Extensive wet deposition monitoring data, along with much sparser dry deposition monitoring data and isolated field characterizations of droplet deposition, are used to produce an annual deposition budget for S and NO_x-N for each contiguous U.S. state and Canadian province. The contribution to wet deposition from natural sources is estimated, and wet deposition is adjusted accordingly, to focus the analysis on deposition associated with anthropogenic emissions. The budgets, which are appropriate for 1985–1987, include adjustments for increased local wet and dry deposition near point sources and urban areas, which are generally avoided in selecting monitoring sites. When aggregated over the United States and Canada, estimated wet, dry, and droplet deposition account for about 30, 29, and 4% of anthropogenic S emissions, respectively, implying that 37% is exported. For NO_x-N, estimated wet, dry, and droplet deposition account for 30, 43, and 4% of anthropogenic emissions, with 23% exported. Results are in general agreement with a variety of other observational analyses and regional modeling simulations, particularly for eastern North America, and are consistent with estimates of net horizontal mass fluxes of S and NO_x-N across the Atlantic coast of North America.     

pH and hydrogen ion deposition patterns in precipitation for the continental United States and Canada

Maps of both volume-weighted mean pH and mean H⁺ deposition in precipitation were developed for the continental United States and Canada using data from 12 precipitation chemistry monitoring networks. The maps were constructed using 1981–1982 laboratory pH data from approximately 130 monitoring sites. The area of greatest acidity (lowest pH/highest H⁺ deposition) is located in the northern Ohio Valley and southeastern Ontario, an area corresponding to high SO_x and NO_x emissions.     

Calculating nitrogen deposition in Europe

Nitrogen deposition calculations for Europe were performed by separate models describing the long-range transport of ammonia and oxidized N. A linearized version of a non-linear atmospheric chemistry model was used for calculating oxidized N. Model computations were found to be consistent with the observed spatial pattern of wet nitrate deposition in Europe. Interannual meteorological variability was estimated to cause a typical year-to-year variation in annual oxidized N deposition of about 6 to 10%. Nitrogen deposition was computed for several NO _x emissions reduction scenarios. These scenarios were derived from an OECD study and applied to the 27 largest countries in Europe. Most reduction scenarios affected the deposition pattern of oxidized N, but the most extreme NO _x emission reduction scenario did not change very much the overall pattern of total (oxidized N plus ammonia N) N deposition. Depending on the desired level of environmental protection, it may be necessary to reduce ammonia emissions in addition to NO _x emissions in order to reduce N deposition in Europe.     

Dry and wet atmospheric deposition of nitrogen, phosphorus and silicon in an agricultural region

We measured atmospheric nutrient deposition as wet deposition and dry deposition to dry and wet surfaces. Our analyses offer estimates of atmospheric transport of nitrogen (N), phosphorus (P) and silicon (Si) in an agricultural region. Annual dry and wet deposition (ha^?1 year^?1) was 0.3 kg of P, 7.7 kg of N, and 6.1 kg of Si; lower than or similar to values seen in other landscapes. N:P and Si:N imply that atmospheric deposition enhances P and Si limitation. Most P and soluble reactive P (SRP) deposition occurred as dryfall and most dry-deposited P was SRP so would be more readily assimilable by plant life than rainfall P. Dry deposition of N to wet surfaces was several times greater than to dry surfaces, suggesting that ammonia (NH _x ) gas absorbtion by water associated with wet surfaces is an important N transport mechanism. Deposition of all nutrients peaked when agricultural planting and fertilization were active; ratios of NH _x :nitrate (NO _x ) hbox{reflected} the predominant use of NH _x fertilizer. Wet deposition estimates were consistent over hundreds of km, but dry deposition estimates were influenced by animal confinements and construction. Precipitation wash-out of atmospheric nutrients was substantial but larger rain events yielded higher rates of wet deposition. Methodological results showed that local dust contaminated wet deposition more than dry; insects, bird droppings and leaves may have biased past deposition estimates; and estimating dry deposition to dry plastic buckets may underestimate annual deposition of N, especially NH _x .     

Linear programming for abatement of nitrogen oxides acid rain deposition

Linear programming is used to examine NO_x as an air quality management problem. Through the use of transfer coefficients, which translate source emissions of NO_x into receptor impacts, the model developed herein seeks to minimize the total cost of reducing emissions from 14 major Canadian point sources. It does this subject to the constraint that the wet deposition at 5 sensitive receptors must be reduced by at least some minimum amount. Several different reductions in wet deposition are used to observe the increase in costs associated with a systematic ‘tightening’ of the constraint relationships. A particular level of reduction is used to examine, on a more detailed level, the sources requiring some level of removal. These case study results and an analysis of the rationale for their solution are presented. Also presented is a comparison between this type of optimization strategy and the scenario of a single ‘across-the-board’ emissions cutback. From NO_x considerations alone, it would seem more expedient to concentrate current research efforts into developing technologies to further reduce vehicle emissions, since their magnitude considerably outweighs those from the point sources.     

The geographical distribution and temporal variations of acidic deposition in Eastern North America

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.     

Contribution of dissolved organic nitrogen deposition to total dissolved nitrogen deposition under intensive agricultural activities

For elucidating the atmospheric deposition contribution of dissolved organic nitrogen (DON) to the total dissolved nitrogen (TDN) deposition rate, dissolved inorganic nitrogen (DIN: NH₄ ⁺ + NO₃ ^–) and DON deposition rates were annually and monthly estimated during 4 and half-yr monitoring period in an experimental multi-farm under intensive agricultural activities of N fertilizer use and animal husbandry in Central Japan. Annual NH₄ ⁺, DON and NO₃ ^– deposition rates in bulk and wet deposition data accounted for 48%, 32% and 20% of TDN deposition, respectively, which indicated that this area is strongly affected by the intensive agricultural activities. The DIN and DON deposition rates were respectively estimated at 21.6 and 10.1 kg N ha^?1 yr^?1, which ranked high in a worldwide regional data set. Consequently, this area has been exposed to a large amount of N deposition including DON with N fertilizer input. The difference between bulk and wet deposition rates (NH₄ ⁺ and DON) is one of important factors controlling the N deposition in this area. Monthly DON deposition showed positive correlations with DIN and NH₄ ⁺ deposition rates, respectively, with a significant linear regression curve. The linear regression curve of our monthly data (n = 127) indicates the same trend as the worldwide annual data set (n = 31).     

A comparison between wet and bulk deposition at an urban site in the U.K.

As a part of an ongoing investigation into urban acidic deposition in Greater Manchester, a wet-only collector was collocated with a bulk collector in the city centre of Manchester, one of 18 sites of an urban precipitation monitoring network. A comparison of data from these collocated bulk and wet-only collectors allowed estimates of the contribution of dry deposition to the bulk collector to be made. Dry deposition was found to contribute between 15 and 17% to elevated deposition and concentrations of non marine sulphate, nitrate and ammonium in the bulk collector. By a statistical analysis between ion concentrations with gas concentrations and an evaluation of the available literature, the form of the dry deposited material was inferred. The contribution of dry deposited Ca²⁺ to concentration and deposition in the bulk collector was found to be 46%. Calcium species are suggested as being those which reduce acidity most. Statistical analyses revealed significant differences between concentrations of ions found in the bulk and wet-only collectors. An evaluation of the data from the collocated collectors has identified possible sampling artifacts introduced by the use of bulk collectors in urban areas.     

Relationship between wet deposition of sulfate and nitrate and rainfall amount in Japan

A regression model of wet deposition on rainfall amount for non-seasalt sulfate (nss-SO₄ ^2?) and nitrate (NO₃ ^?) was applied to a data set obtained through a nationwide survey from April 1989 to March 1993. Wet-only samples on a biweekly basis were collected at 29 sites over Japan. Reparameterized bivariate lognormal distribution was employed to describe the joint distribution of concentration (C) and rainfall amount (R) for each site. Ranges of geometric mean (μ_D) of biweekly deposition (D = C. R) for each site were 0.54–2.90 meq m^?2 for nss-SU₄ ^2?, and 0.21–1.36 meq m^?22 for NO₃ ^?; that of biweekly rainfall amount (μ_R) was 24.1–78.0 mm. Urban or industrialized areas had high values of μ_D for these ions. Ranges of estimates of the slope of the regression equation of log(D/μ_D) on log(R/μ_R), were 0.45–0.99 for nss-SO₄ ^2?, and 0.35–0.86 for NO₃ ^?; thus estimates of the slope for nss-SO₄ ^2? tend to be larger than those for NO₃ ^?. The present analysis, consequently, statistically clarified some differences between the two ions in deposition processes which is understood in the light of current knowledge of atmospheric chemistry.     

Acid deposition to nature areas in the Netherlands: Part I. Methods and results

In this paper estimates of dry and wet deposition of acidifying substances in the Netherlands are presented. The deposition was estimated from measured concentrations in the atmosphere and in precipitation or if these were not available, from modelled concentrations. The method was applied for the Netherlands on a 5×5 km scale. The most important components are sulphur oxides and ammonia and their reaction products. It was estimated that the annual average deposition of SO _x in the Netherlands decreased from 1570 to 670 mol ha^?1 a^?1 between 1980 and 1989. In 1989, the annual average NO _y deposition was estimated to be 1220 mol ha^?1 a^?1 in 1980 and 1160 mol ha^?1 a^?1 in 1989. The annual average NH _x deposition in the Netherlands was estimated to be 2330 and 2190 mol ha^?1 a^?1 in 1980 and 1989 respectively. HCI deposition was about 100 mol ha^?1 a^?1 in all years. Dry deposition contributes most to the total deposition for each component. The spatial distribution of the total deposition shows a gradient over the Netherlands with highest values in the South and lowest in the North of the country. Meteorological conditions are also of influence on the deposition fluxes for all components. During 1988 and 1989 meteorological conditions favoured low deposition. The estimated uncertainty in the average fluxes of SO _x , NO _y , and NH _x for the Netherlands is 15, 25, and 30% respectively. The wet deposition fluxes can be estimated more accurately than the dry deposition.     

Nature and Magnitude of Atmospheric Fluxes of Total Inorganic Nitrogen and Other Inorganic Species to the Tampa Bay Watershed, FL, USA

We estimated the total inorganic fluxes of nitrogen (N), sulfur (S), chloride (Cl^?, sodium (Na⁺, calcium (Ca²⁺, magnesium (Mg²⁺, potassium (K⁺ and hydronium (H⁺. The resistance deposition algorithm that is programmed as part of the CALMET/CALPUFF modeling system was used to generate spatially-distributed deposition velocities, which were then combined with measurements of urban and rural concentrations of gas and particle species to obtain dry deposition rates. Wet deposition rates for each species were determined from rainfall concentrations and amounts available from the National Acid Deposition Program (NADP) monitoring network databases. The estimated total inorganic nitrogen deposition to the Tampa Bay watershed (excluding Tampa Bay) was 17 kg-N ha^?1 yr^?1 or 9,700 metric tons yr^?1, and the ratio of dry to wet deposition rates was ～2.3 for inorganic nitrogen. The largest contributors to the total N flux were ammonia (NH₃ and nitrogen oxides (NO _x at 4.6 kg-N ha^?1 yr^?1 and 5.1 kg-N ha^?1 yr^?1, respectively. Averaged wet deposition rates were 2.3 and 2.7 kg-N ha^?1 yr^?1 for NH₄ ⁺ and NO₃ ^?, respectively.     

Some Insights into Atmospheric Processes Involving Urban Sulphur and Nitrogen in and around Hong Kong,SAR

The representative mass ratio of the reactive airborne sulphur-to-nitrogen, S/N in the gas and aerosol phases, and in wet and dry deposition over the territory of Hong Kong, SAR,was determined, utilizing available data for the 12 yr period, 1986–1997. Using this information, the representative stoichiometric ratio values for sulphate-to-nitrate in aerosoland in wet and dry depositions were estimated. A limited supplementary data set on various canopy depositions was alsoutilized. This information collectively suggests several basicdifferences in photochemical processes between the urbanatmospheres in and around Hong Kong and the classical, smoggyLos Angeles. This is also supported by the typical diurnal variation of nitrogen oxides in Hong Kong, which suggests a moreefficient photo-oxidation of NO to NO₂ within the territoryand in nearby areas upwind, as compared to further oxidation tothe NO₃ (or nitrate) stage. On the other hand, the relatively low gas-to-particle ratio value estimated for S (～3) relative to N (～26) suggests that the advectedfraction of non-sea salt aerosol sulphate in the territory couldbe considerably greater than the corresponding fraction for nitrate. Finally, significant losses (probably related to sampling) of NH₄-NH₃ in dry deposition could be inferred, while for SO₄ in wet deposition, a moderate enrichment factor of ～2 is observed in relation to SO₄ in aerosol.     

山西省太原市旱作农区大气活性氮干湿沉降年度变化特征

鉴于大气氮素沉降对整个生态系统的重要影响,我国近年来陆续开展了不同尺度的大气氮素干、湿沉降的研究,但少有农业区多年连续监测的资料。本研究利用DELTA系统、被动采样器和雨量器在山西省太原市郊区阳曲县河村旱作农业区进行了4年的监测试验,观测大气氮素干、湿沉降的时间变异。结果表明:2011年4月—2015年3月,河村4年大气活性氮NH_3、HNO_3、NO_2、颗粒态NO_3~-(pNO_3~-)、颗粒态NH_4~+(pNH_4~+)平均沉降量分别为4.50 kg(N)·hm~(-2)·a~(-1)、3.54 kg(N)·hm~(-2)·a~(-1)、2.56 kg(N)·hm~(-2)·a~(-1)、1.62 kg(N)·hm~(-2)·a~(-1)、2.75 kg(N)·hm~(-2)·a~(-1),大气氮素干沉降总量为12.38~18.95 kg(N)·hm~(-2)·a~(-1),以2011年的氮干沉降量最高,2014年的最低。2011年4月—2015年3月各月氮干沉降量与氨气沉降量之间存在显著正相关,相关系数在0.809 8~0.937 1,由此可知,该地区活性氮沉降主要受农业氨气排放的影响。河村4年雨水中NO_3~-、NH_4~+平均浓度分别为3.20 mg(N)·L~(-1)和2.43 mg(N)·L~(-1),大气氮素湿沉降11.67~41.31 kg(N)·hm~(-2)·a~(-1)。年度间氮素湿沉降存在很大差异,以2012年氮素年湿沉降量最高,2014年最低,每年大气氮素湿沉降占氮总沉降量的份额超过50%。此外,4年湿沉降中不仅NO_3~--N和NH_4~+-N之间、且二者与降雨量也呈显著线性或二次相关关系,说明降雨量对NO_3~--N和NH_4~+-N的湿沉降影响较大。本研究表明太原市旱作农区不同年份间氮素湿沉降比干沉降差异更大,且总沉降数量较高。虽然是旱作区,该地区氮素干沉降略低于湿沉降。研究结果为该地区农田氮肥施用和氮素循环监测提供了理论依据。     

Increasing contributions of nitrogen to the acidity of surface waters in Norway

The acidification of lakes in southern Norway is largely due to sulfate. Recent data from regional surveys of lakes and from monitoring stations indicates that nitrate concentrations have increased in many lakes and rivers in southernmost Norway. The ratio of NO₃ to NO₃ + SO₄ is still low for most areas, but is 0.54 on an equivalent basis in lakes and rivers in the area of high runoff in southwestern Norway. Here, concentrations of nitrate in the runoff are lower than for sites in Central Europe, but are higher than those in North America. The sites showing increases in NO₃ also increased in Al. Further increases in nitrate as a mobile anion which may be due to decreased uptake in the watershed, will contribute to acidification in the same manner as sulfate.     

Study of wet and dry atmospheric deposition at two altitudes in central Switzerland

The analysis of various ions in atmospheric deposition at two altitudes (515 m and 950 m a.s.l.) in Switzerland during 1983/84 revealed that dry deposition depends more on altitude than wet deposition. During autumn and winter, when vertical air exchange is limited, dry deposition of substances from anthropogenic sources (e.g. SO₄-S) was higher at the lower site. In the course of the year, the pattern of wet deposition was independent of altitude and showed highest rates for S, N and Ca in summertime. A comparison between rates of wet, particulate and gaseous S and N deposition suggested that during the growing season wet deposition is the dominant flux. Total (wet + dry) deposition of S, N and Cl was lower than in other parts of Europe, but a substantial increase of NO₃-N deposition during the past 25 years must have occured.     

The acidifying potential of atmospheric deposition in Canada

It is proposed that the value of ([SO₄ ^??] - [Ca⁺⁺ + Mg⁺⁺]) in precipitation is a suitable way to describe the acidifying potential (AP) of the wet desposition. In eastern North America, the AP of precipitation varies from 20 to 85% of the total sulphate, the remainder of the sulphate being neutralized H₂SO₄, sulphate from salts in dust or from sea salt. The AP ranges from 20 to 80% of the H⁺ in the wet deposition. The rest of the H⁺ is contributed by the net effect of N compounds. Ammonium and nitrate ions from ammonia and NO_Xemissions do not represent a net acidic loading to the terrestrial ecosystem if they are taken up by vegetation. However, when N leaches from watersheds in the form nitrate, it constitutes an acidifying demand on the ecosystem. Therefore, the overall net acidifying potential (NAP) applied to the terrestrial ecosystem is defined by the value of ([SO₄ ^??] - [Ca⁺⁺ + Mg⁺⁺]) in precipitation plus [NO₃ ^??] in runoff from the watershed.     

上海地区氮素湿沉降及其对农业生态系统的影响

试验研究上海地区N素湿沉降及其对农业生态系统的影响结果表明,上海地区湿沉降中N营养盐含量较高,其中NO3-为2.587mg/L,NH4 达2.155mg/L,TIN的含量均在4.000mg/L以上。湿沉降输入到上海地区农业生态系统N营养盐的年通量较高,其中NH4 平均为26.580kg/hm2,1999年达到38.930kg/hm2;NO3-平均为31.545kg/hm2;TIN平均为58.123kg/hm2,相当于124.549kg/hm2尿素或327.980kg/hm2碳酸氢铵,1999年TIN输入量为77.750kg/hm2,相当于166.607kg/hm2尿素或438.732kg/hm2碳酸氢铵,占1998年全国化肥(N)平均施用量的35%。湿沉降中N的输入对农业生产有重要影响。     

A Computational Approach Based on GIS Technology for the Development of an Anthropogenic Emission Inventory of Gaseous Pollutants in Greece

This paper describes a computational system developed for the compilation of an anthropogenic emission inventory of gaseous pollutants for Greece. The inventory was developed using a geographical information system integrated with SQL programming language to provide high temporal gridded emission fields for CO, NO₂, NO, SO₂, NH₃ and 23 non-methane volatile organic compounds (NMVOCs) species for the reference year 2003. Activity and statistical data from national sources were used for the quantification of emissions from the road transport, the other mobile sources and machinery sectors and from range activities using top-down or bottom-up methodologies. Annual emission data from existing national and European emission databases were also used. The emission data were spatially and temporally disaggregated using source-specific spatiotemporal indicators. On national scale, the road transport sector produces about 60% of the annual CO and NMVOC total emissions, with gasoline vehicles being the main CO and NMVOC emissions source. The road transport is responsible for approximately half of the higher alkanes and for more than half of the ethene and toluene emissions. The maritime sector accounts for about 40% of the annual total NO_x emissions, most of which are emitted by the international shipping subsector, whilst SO₂ is emitted mainly by the energy sector. The evaluation of the emissions inventory suggests that it provides a good representation of the amounts of gaseous pollutants emitted on national scale and a good characterisation of the relative composition of CO and NO_x emission in the large urban centres.     

Nitrogen oxides,regional transport,and ozone air quality: Results of a regional-scale model for the midwestern United States

An overview of the role of NO _x in the formation of rural O₃, regional transport and its potential impact on urban air quality is presented. An analysis of a specific O₃ excursion in southeast Michigan (8-2-90) is performed based on a combined urban and regional-scale model. The regional component of the model represents transport and photochemistry from sources as far away as Texas. Results suggest that rural O₃ and regional transport sensitive to NO _x emissions and relatively insensitive to changes in volatile organic carbon (VOC) emissions. This differs from the situation in urban areas, where O₃ is sensitive to both NO _x and VOC. Regional transport and upwind NO _x emissions have a significant impact on peak O₃ in Detroit. Implications for urban and regional-scale abatement strategies are discussed.     

Estimation of source-receptor matrices for deposition of NOx-N

The contributions of the anthropogenic sources of NO_x from various combinations of contiguous U.S. states or Canadian provinces to integrated deposition across selected states or provinces are estimated with the Advanced Statistical Trajectory Regional Air Pollution (ASTRAP) model. The model assumes linearity between emissions and deposition, and uses the same parameterization methods, although with different rates, as in simulations of transport and deposition of SO_X. Vertical distributions of emissions for the two classes of pollutants are substantially different in the gridded inventories used in simulations, with a weighted mean effective emission height of 160 m for NO_X and 310 m for SO_X. This might be expected to lead to an effective transport distance before deposition shorter for NO_X than for SO_X. However, the calculated fraction of NO_X emissions deposited within the contiguous United States and Canada south of 60 deg N (57%) is not greatly different from the fraction calculated for SOX emissions (54%). This suggests that there may be compensating factors in the horizontal distribution of NO_X emissions, and in the lower dry deposition velocities for NO/NO₂ than for SO₂ in ASTRAP.