Scavenging ratios and deposition of sulphur,nitrogen and chlorine species in eastern England

Measurements of wet deposited NH₄⁺, SO₄²⁻, NO₃⁻ and Cl⁻, as well as airborne concentrations of these species and gaseous HNO₃, HCl and NH₃, have been made at a site in eastern England. Scavenging ratios based solely upon aerosol-associated species and upon aerosol plus gaseous airborne species are presented and compared with literature values. It appears that HCl and HNO₃ have only a rather minor influence upon wet deposition at our site. Gaseous NH₃ influences ground-level air chemistry appreciably, but scavenging ratios for NH₄⁺ are low, even when based upon aerosol NH₄⁺ concentrations alone, presumably due to altitudinal gradients in this species. The problems inherent in interpretation of scavenging ratios are discussed. Deposition of nitrogen in various chemical forms is estimated from rainwater and air composition. If a transport-limited deposition velocity is assumed for ammonia gas, dry deposition of this species accounts for around 40% of total nitrogen deposition to the ground.     

Atmospheric concentrations and deposition of nitrogen and major ions in conifer forests in the United States and Federal Republic of Germany

Emission densities of air pollutants are higher in Europe than in the U.S. as a whole, suggesting similar differences in atmospheric deposition. We determined air concentrations and deposition during the warm season at conifer forests in Tennessee and northern Germany. Our results confirmed major differences in both chemistry and fluxes. Atmospheric and precipitation concentrations of all ions except H⁺ were higher at the German site, most significantly for the nitrogen species. The much higher levels of NH₄⁺ at this site reflect higher emissions of NH₃, which was the species largely responsible for the lower levels of H⁺. Total airborne nitrate was dominated by HNO₃ in Tennessee. In Germany we found comparable amounts of HNO₃ and aerosol NO₃⁻, the concentration of which varied seasonally, apparently in response to agricultural emissions of NH₃ that reacted to form NH₄NO₃. Total deposition of all major ions was much higher at the German site, particularly for the nitrogen species, which exhibited a marked edge effect in throughfall. Dry deposition was determined from air concentrations by using a canopy resistance model and from a statistical model of throughfall fluxes, each of which yielded comparable fluxes for several ions. Dry deposition contributed 10–70% of the ion input and was most important at the German site. Both forest canopies absorbed 40–50% of total deposited nitrogen, primarily from dry deposition.     

On the interaction between equilibration processes and wet or dry deposition

Atmospheric equilibration processes between two phases with different deposition velocities have the potential to affect significantly the amount of total material deposited on the ground. The magnitude of the effects of the equilibration processes depends primarily on the ratio of the deposition velocities of the two phases, on the production/emission rate of the gas phase species, and on the initial distribution of species between the two phases. The deposition of a condensible species equilibrating between gas and aerosol phases can increase by as much as 20 times over that when equilibration processes are not present under appropriate conditions (very large aerosol particles, most of the material initially in the gas phase and high gas-phase production rate) or to decrease by as much as 15 times (very small aerosol particles, most of the material initially in the gas phase and high gas-phase production rate). In fog episodes, the deposition of a gaseous species with a Henry's Law constant between 10³ and 10⁶ M atm⁻¹ (e.g. SO² for pH between 4.5 and 7, H₂O₂, HCHO etc) can be enhanced by as much as a factor of 3 because of its transfer to the aqueous phase. For the NH₃HNO₃NH₄NO₃ system the total deposition can be reduced by as much as a factor of 3 for typical conditions in a polluted atmosphere and small initial concentration of aerosol NH₄NO₃ with NH₃ initially dominating HNO₃ in the gas phase. If an operator splitting scheme is used in a mathematical both equilibration and removal processes should be included in the same operator or very small operator time steps (typically less than 1 min) will be necessary.     

European scale application of atmospheric reactive nitrogen measurements in a low-cost approach to infer dry deposition fluxes

A European scale network was established in 2006 as part of the NitroEurope Integrated Project to infer reactive nitrogen (Nr) dry deposition fluxes, based on low-cost sampling of gaseous and aerosol species and inferential modelling. The network provides monthly measurements of NH₃, NH₄⁺, HNO₃ and NO₃⁻, as well as SO₂, SO₄²⁻, HCl, Cl⁻ and base cations at 58 sites. Measurements are made with an established low-cost denuder methodology (DELTA) as a basis to: (1) examine temporal trends and spatial patterns across Europe, (2) improve and calibrate inferential modelling techniques to estimate exchange of Nr species, (3) provide best estimates of atmospheric dry N deposition, and (4) permit an analysis of net GHG exchange in relation to atmospheric and agricultural N inputs at the European scale. Responsibility for measurements is shared among seven European laboratories. An inter-comparison of the DELTA implementation by 6 laboratories at 4 test sites (Montelibretti, Italy; Braunschweig, Germany; Paterna, Spain and Auchencorth, UK) from July to October 2006 provided training for the laboratories and showed that good agreement was achieved in different climatic conditions (87% of laboratory site-means within 20% of the inter-laboratory median). Results obtained from the first year of measurements show substantial spatial variability in atmospheric Nr concentrations, illustrating the major local (NH₃) and regional (HNO₃, NO₃⁻, and NH₄⁺) differences in Nr concentrations. These results provide the basis to develop future estimates of site-based Nr dry deposition fluxes across Europe, and highlight the role of NH₃, largely of agricultural origin, which was the largest single constituent and will dominate dry Nr fluxes at most sites.     

The spatial distribution and particle size of some inorganic nitrogen,sulphur and chlorine species over the North Sea

The use of filter packs and a cascade impactor during a series of research cruises in the southern area of the North Sea has yielded detailed spatial distribution patterns of aerosol concentrations, Cl⁻, NO₃⁻, SO₄²⁻¹ and NH₄⁺ and gaseous concentrations, HCl, HNO₃ and NH₃. The overall distribution of the atmospheric concentrations closely parallels published modelled results for metallic species. The chemical transformations of these aerosols and gases are investigated together with their interactions with the seasalt aerosol. Aerosol chloride loss is greatest in the more polluted areas, whilst concentrations products of NH₃ with HNO₃ and HCl appear insufficient to sustain the existence of NH₄NO₃ and NH₄Cl. Nitrate is associated predominantly with larger particles and appears to be present substantially as a surface coating on marine aerosol. The total dry deposition input for nitrogen species is calculated for the southern sector with extrapolation to the whole of the North Sea, using particle size weighted deposition velocities of 0.63 and 0.21 cm s⁻¹ for NO₃⁻¹ and NH₄⁺, respectively, and literature-derived values for the gaseous constituents. Finally the use of air-mass back trajectories illustrates the role of source regions in influencing the chemical composition of the North Sea atmosphere.     

应用扩散管测量霾污染期间大气氮硫化合物浓度的方法

活性氮和硫化合物在大气颗粒物形成过程中扮演重要角色,但对它们气相/颗粒相的同步观测结果比较缺乏.本研究尝试基于扩散管的DELTA系统测量氮和硫化合物短时累积浓度,以期捕捉它们在霾污染期间的演变规律.结果表明,DELTA系统收集气态污染物的扩散管中以及颗粒物滤膜上NH_4~+和NO-3空白干扰较小,适用于研究NH_3、HNO_3、NH_4~+和NO-3的日均浓度,可以作为城市环境空气质量监测参数的有效补充;但采样系统中SO_2-4背景含量较高,仅适合监测48 h以上时间尺度的SO_2浓度和周~月尺度SO_2-4浓度,用于大气硫沉降观测.北京2016年5月9日~6月7日观测期间,大气NH_3、HNO_3、NH_4~+和NO-3浓度具有明显的逐日演变规律,呈现出随着风向转变而发生周期性波动的典型特征;这些含氮污染物与PM_(2.5)、CO、SO_2和NO_2浓度的变化规律一致,其来源可能与化石燃料燃烧源有关.污染天NH_3、HNO_3、NH_4~+和NO-3浓度约为清洁天的2倍,但还原性氮和氧化性氮的相态分布在清洁天和污染天无明显差异;整个观测期间,HNO_3/NO-3约为1.2,NH_3/NH_4~+为4.5,春夏之交较高的温度有利于活性氮在气粒平衡过程中偏向于气态形式存在.     

Measurements of atmospheric HNO3, HCl and associated species on a small network in eastern England

Measurements of gaseous HNO₃, HCl and NH₃ and particulate NO₃⁻, SO₄²⁻, Cl⁻ and NH₄⁺ have been made at a small network of sites in eastern England using sampling intervals from 3 h to 7 days. Both HCl and HNO₃ are spatially rather uniform, with some variation apparently due to spatial variations in NH₃, which stoichiometrically exeeded the sum of both gaseous acids. Mean concentrations of NH₃, HCl and HNO₃ between February 1987 and January 1988 were 1.90, 0.67 and 1.01 μg m⁻³, respectively. Pollution roses revealed low NH₃ concentrations, and high associated HCl and HNO₃ with winds from the North Sea. HCl, but not HNO₃ showed an appreciable elevation in concentration on the sector NW from our site, which we speculate may be due to the large capacity of coal-fired power stations in this upwind sector. Three-hourly data have been examined for diurnal effects and its is concluded that nocturnal formation of NO₃⁻ is occurring.     

Fogwater chemistry at Riverside,California

Fog, aerosol, and gas samples were collected during the winter of 1986 at Riverside, California. The dominant components of the aerosol were NH₄⁺, NO₃⁻, and SO₄₂₋. Gaseous NH₃ was frequently present at levels equal to or exceeding the aerosol NH₄⁺. Maximum level were 3800, 3100, 690 and 4540 neq m⁻³ for NH₄⁺, NO₃²⁻ and NH_3(g), respectively. The fogwater collected at Riverside had very high concentrations, particularly of the major aerosol components. Maximum concentrations were 26,000 29,000 and 6200 μM for NH₄⁺, NO₃⁻ and SO₄²⁻, respectively. pH values in fogwater ranged from 2.3 to 5.7. Formate and acetate concentrations as high as 1500 and 580 μM, respectively, were measured. The maximum CH₂O concentration was 380 μM. Glyoxal and methylglyoxal were found in all the samples; their maximum concentrations were 280 and 120 μM, respectively. Comparison of fogwater and aerosol concentrations indicates that scavenging of precursor aerosol by fog droplets under the conditions at Riverside is less than 100% efficient.The chemistry at Riverside is controlled by the balance between HNO₃ production from NO_x emitted throughout the Los Angeles basin and NH₃ emitted from dairy cattle feedlots just west of Riverside. The balance is controlled by local mixing. Acid fogs result at Riverside when drainage flows from the surrounding mountains isolate the site from the NH₃ source. Continued formation of HNO_3(g) in this air mass eventually depletes the residual NH_3(g). A simple box model that includes deposition, fog scavenging, and dilution is used to assess the effect of curtailing the dairy cattle feedlot operations. The calculations suggest that the resulting reduction of NH₃ levels would decrease the total NO₃⁻ in the atmosphere, but nearly all remaining NO₃⁻ would exist as HNO₃. Fogwater in the basin would be uniformly acidic.     

Apparent deposition velocity and compensation point of ammonia inferred from gradient measurements above and through alfalfa

Understanding the cycling of ammonia between croplands and the atmosphere is of importance to agriculturalists and atmospheric scientists. Flux densities of gaseous ammonia (NH₃), particulate ammonium (NH₄⁺), and total ammoniacal nitrogen (AN) were measured using an aerodynamic method above an alfalfa (Medicago sativa, L.) canopy between April and July 1981 at a rural location in central New York State. In air not influenced by local sources, NH₃ and NH₄⁺ averaged 1.5 and 3.0 ppb, respectively, at 1 m above the crop. Ambient NH₄⁺ varied consistently with synoptic air masses, being lowest (2.3 ppb) for NW and highest (6.4 ppb) for SW flows. Concentrations and gradients of both species were higher during periods of hay harvest. Gradients of NH₃ were much steeper than those of NH₄⁺ within the alfalfa canopy, but NH₄⁺ contributed appreciably (36% on average) to above-canopy AN gradients. Alfalfa's NH₃ compensation point was estimated by combining concentration and gradient data with transport resistances. Gaseous gradients indicated a compensation point of 2 ppb, lower than previously published estimates. Conversion of NH₃ to NH₄⁺ within the canopy air could have reduced NH₃ gradients and caused a low estimate of the compensation point. Acidic aerosols, by keeping NH₃ levels low, may compete with plants for NH₃. Future studies of ammonia exchange should distinguish between NH₃ and NH₄⁺ if flux densities are to be related to ambient conditions. Total AN level is a poor predictor of soil-plant-atmosphere ammonia exchange since high AN was frequently associated with low NH₃, and NH₃ is more surface reactive than NH₄⁺.     

冬季猪粪固体堆放过程中NH3、N2O和NO排放特征研究

针对农村猪粪典型处理方式中的固体堆放管理,研究猪粪在冬季(2012年11月~2013年2月)固体堆放过程中NH3、N2O和NO排放特征.实验共设两个处理——无覆盖(non-covered,NC)和水稻秸秆覆盖(covered,C),堆放时间为73 d,期间进行了3次翻堆操作.实验观测了3种含氮气体(NH3、N2O和NO)的排放通量和堆体剖面N2O浓度变化.结果表明,猪粪固体堆放过程中NH3、N2O和NO排放累积量(以N计)分别占初始TN的比例为2.1%~2.6%、0.02%和~0.000 25%.两个处理的含氮气体排放通量变化趋势基本一致,且有覆盖堆体的含氮气体的排放量略低于无覆盖堆体.在堆放初期,NH3排放量最先出现峰值,之后N2O和NO排放开始增加.NH3和NO在固体堆放的中前期呈现互为消长的变化趋势;到堆放后期,N2O开始出现比前期高出两倍的排放高峰,而NH3和NO出现小幅增长.翻堆前后,NH3的排放无明显变化,而N2O排放在翻堆后均出现降低的变化,NO排放却出现升高的变化.     

Atmospheric dry deposition on pines in the Eastern Brook Lake Watershed,Sierra Nevada,California

Atmospheric dry deposition to branches of Pinus contorta and P. albicaulis was measured during summer 1987 in a sub-alpine zone at Eastern Brook Lake Watershed (EBLW), eastern Sierra Nevada, California. Results are presented as deposition fluxes of NO₃⁻, SO₄²⁻, PO₄³⁻, Cl⁻, F⁻, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺, K⁺, Zn²⁺, Fe³⁺, Mn²⁺, Pb²⁺ and H⁺, and compared with other locations in California and elsewhere. Deposition fluxes of anions and cations to the pine branches were low, several times lower than the values determined near the Emerald Lake Watershed (ELW), another sub-alpine location in the western Sierra Nevada. The sums of deposition fluxes of the measured cations and anions to pine surfaces were similar, in contrast to the ELW location where the sums of cation fluxes were much higher than the sums of anion fluxes. A strong positive correlation between depositions of NO₃⁻ and NH₄⁺, as well as SO₄²⁻ and Ca²⁺, suggested that large portions of these ions might have originated from particulate NH₄NO₃ and CaSO₄ deposited on pine surfaces. An estimated total N dry deposition (surface deposition of NO₃⁻ and NH₄⁺ and internal uptake of NO₂ and HNO₃) to the forested area of the EBLW was 29.54 eq ha⁻¹ yr⁻ (about 414 g H ha⁻¹ yr⁻¹).     

稻田气溶胶NH3和气体NOx排放在线测定研究

气溶胶NH3和气体NOx是大气颗粒物和降水的主要成分,是形成气溶胶的关键物种.田间集约化氮肥施用是气溶胶NH3和气体NOx的一个重要来源,目前该领域的研究鲜有报道.2010年5月～2010年10月,在线监测了稻田施用尿素后气溶胶NH3和气体NOx的排放情况.监测系统的时间分辨率设置为1 h.在4次稻田施肥试验中,施肥后对气溶胶NH3排放和相应的气象因子连续采样20 d.在第4次施肥试验中,施肥后连续采样47 d,进而研究气体NOx的排放规律及其与气象因子的关系.结果表明,气溶胶NH3的排放因子分别为2.6%、5.5%、4.0%和1.6%,相应的排放通量分别为3.97、2.08、1.52和1.22 kg·hm-2.温度(空气温度和土壤温度)是影响稻田施肥气溶胶NH3排放的主要因子,而空气湿度和土壤水分对其排放的影响却不明确.通过分析监测数据可知,稻田施肥后NO2-N排放量与NO-N排放量的比值为9/4,气体NOx的排放因子和排放通量分别为0.14%和0.30 kg·hm-2.气象因子与气体NOx排放通量的关系也进行了初步探讨.     

Changing sources of impurities to the Greenland ice sheet over the last 250 years

Because the composition of precipitation reflects the composition of the atmosphere, polar ice cores provide a useful way of investigating past and present atmospheres. We have measured concentrations of major ions in nine sections of a central Greenland ice core and we found that concentrations of both SO₄²⁻ and NO₃⁻ have increased dramatically over the last 250 years, up to three to four times the 18th century levels. Large changes have also occurred in the average concentrations of several other chemical species, such as NH₄⁺, excess Cl, and Ca²⁺. We used a principal-component analysis to characterize variations of the season of maximum deposition rate of HNO₃ and H₂SO₄ to the snow. We found that source fluctuations of H₂SO₄ are faithfully recorded in the Greenland snow and appear to switch their preferential time of deposition in the snow from summer to winter early in the 20th century. On the other hand, HNO₃ is deposited preferentially during summer throughout the core, emphasizing the role of photochemistry in understanding nitrogen cycling in the Arctic. Anthropogenic inputs have clearly modified the behavior of several chemical compounds in the atmosphere.     

峨眉山地区大气中的硝酸和氨

为了研究峨眉山地区降水、云雾水明显酸化的原因,1985年10月我们进行了集中观测,并就其测定结果进行分析研究。     

内蒙古温带草原氮沉降的观测研究

在内蒙古太仆寺旗对温带草原地区的氮沉降进行了为期1 a(2011年11月～2012年10月)的观测.在线分析大气NH3和NO2浓度,用CMAQ模型计算的干沉降速率计算了气体干沉降量;采集降水、降尘和穿透雨样品并测定NH4+和NO3-浓度,分别得到湿沉降、颗粒物干沉降和穿透雨沉降量.观测结果表明该地区的氮沉降量已经高达3.43 g.(m2.a)-1,有可能对草原生态系统产生危害.其中,湿沉降占44%,气体干沉降占38%,颗粒物干沉降占18%.干沉降对氮沉降的贡献大于湿沉降,必需重视干沉降的测定,而穿透雨沉降明显小于总沉降,说明穿透雨法不适合于草原地区.从组分上看,还原态氮(包括NH4+和NH3)对氮沉降的贡献为71%,而氧化态氮(NO3-和NO2)的贡献仅29%,因此在控制氮沉降时,不应只针对NOx排放进行削减,NH3减排同样重要.     

Two options to explain the ammonia gap in The Netherlands

This paper addresses two hypothesis that try to explain the difference observed between the estimated NH₃ emission levels in The Netherlands and those indicated by atmospheric measurements, the so called ‘ammonia gap’: the role of SO₂ emissions regulating ambient NH₃ concentrations through co-deposition, and long-term NH₃ emissions after slurry injection. It was found that throughfall measurements of NH₄⁺ could not be used as indicator for changes in NH₃ emissions. The throughfall deposition of NH₄⁺ is in close equilibrium to SO₄²⁻ and NO₃⁻ and is thus regulated by the equilibrium of ambient NH₃ and NH₄⁺ in wet deposition and canopy water layers. When SO₂ emissions decrease, the amount of available SO₄²⁻ decreases, which imposes a limit on the deposition of (NH₄)₂SO₄. Long-term emissions of NH₃ after application of manure were monitored using a new technique, which continuously measures the concentration of NH₃ in a cross-section of the emission plume downwind of the source. The emissions could be registered for 3 weeks after application of manure. The results indicate that the long-term emissions only contribute 1–2% to the total emission level. Both the effect of SO₂ on the NH₃ deposition levels and the long-term emission fluxes are not enough to explain the observed ammonia gap. It seems that several counteracting effects, some of them emerging from the new emission reduction regulations, contribute to the ammonia gap. An integrated approach to abate ammonia emissions is, therefore, needed. The implementation and regulation of production ceilings for reactive nitrogen might be a good option.     

Interactions of aerosols (ammonium sulfate,ammonium nitrate and ammonium chloride) and of gases (HCl,HNO3) with fogwater

The concentrations of aerosols (NH₄NO₃, (NH₄)₂SO₄ and NH₄Cl) and of gases (HCl_(g), HNO_3(g), NH_3(g) were determined by denuder methods under different conditions (in the absence of fog, before, during and after fog events). At this site situated in an urban region, high concentrations of the gaseous strong acids HCl_(g) and HNO_3(g) are observed. NH₄Cl and NH₄NO₃ aerosols represent a major fraction of the Cl⁻ and NO₃⁻ aerosols (<2.4 μm)collected by denuders. During a fog event, very high concentrations of SO₄²⁻ were found in small aerosols, which are attributed to the aqueous phase oxidation of SO₂ under the influence of high pH due to the presence of NH₃. Differences in SO₄²⁻ concentrations measured in aerosols (<2.4 μm) and in fog droplets were probably due to mass-transport limitations of the SO₂ oxidation. Ammonium sulfate aerosols represent in some cases a significant fraction of the total S present (SO_2(g) + SO₄²⁻. Soluble aerosols and gases contribute to the composition of fogwater and are released again after fog dissipation.     

Ambient concentrations,scavenging ratios,and source regions of acid related compounds and trace metals during winter in northern michigan

Daily measurements the atmospheric cocnentrations of HNO₃, NO₃^-, NO₂, SO₂, SO₄²⁻, NH₄⁺, and several trace metals were made at the University of Michigan Biological Station over a 124-day period during the 1984–1985 winter. The composition of the daily precipitation was also determined. The relative contributions of scavenged NO₃⁻ and HNO₃ to the precipitation was estimated by assuming that the NO₃⁻ scavenging ratio was the same as that of trace metals with a similar particle size. Similarly, the SO₄²⁻ and SO₂ contributions were based on the scavenging ratios of NH₄⁺ and trace metals. On this basis, it was determined that the event median NO₃⁻ and HNO₃ scavenging ratios were 500 and 3500, respectively. HNO₃ scavenging accounted for 83% of the total scavenged NO₃⁻. Scavenging of SO₄²⁻ accounted for all the snow SO₄²⁻ in 67% of the events. In the remaining events, some SO₂ was scavenged, with a median scavenging ratio of 219. Overall, 67% of the snowfall acidity appeared to be due to HNO₃ scavenging. Backward air-mass trajectories that were calculated for each event were used to determine the general source regions of the acidic species. Snow associated with air masses from the south and west accounted for 81 and 75% of the deposited NO₃⁻ and SO₄²⁻, respectively.     

常规施肥条件下农田不同途径氮素损失的原位研究:以长江中下游地区夏玉米季为例

为了解农田常规施肥条件下的不同途径氮素损失特征,本文通过田间原位试验同步研究了长江中下游地区夏玉米生长季氮肥施用后的农田N2O排放、NH3挥发、氮渗漏和地表径流的变化.结果表明,在复合肥为基肥,尿素为追肥,基追肥氮素水平均为150 kg·hm-2的条件下,整个玉米生长季N2O排放系数为3.3%,NH3挥发损失率为10.2%,氮渗漏和地表径流损失率分别为11.2%和5.1%.此外,基肥施用以氮素渗漏损失为主,而追肥氮素损失以氨挥发和渗漏为主,表明不同途径化肥氮素损失主要受氮肥品种影响,玉米季追肥可改用低氨挥发氮肥品种以减少氮素损失.     

施用畜禽粪便堆肥品的蔬菜地CH4、N2O和NH3排放特征

农田是重要的温室气体排放来源之一,其中蔬菜地的温室气体排放日益受到人们关注.以北京市郊某温室种植的油麦菜地为研究对象,通过大棚试验,考察和比较了油麦菜地施用不同类型畜禽粪便堆肥产品的CH4、N2O和NH3排放特征及其影响因素.结果表明,油麦菜地NRM、RM、CF处理的CH4排放系数分别为0.2%、0.027%、0.004%;N2O排放系数分别为0.18%、0.63%、0.74%;NH3排放系数分别为2.00%、3.98%、2.53%.CH4排放通量与土壤温度和地表湿度相关,N2O排放通量与土壤温度、地表温度和湿度相关,CH4、N2O和NH3排放通量均受土壤含水率影响,而温室中的气温不是影响CH4、N2O和NH3排放的主要因素.