Pollutant aerosol deposition into Southern Lake Michigan

Current estimates of pollutant aerosol input to southern Lake Michigan are based on a single calculated emission inventory and various estimates of the fraction of emissions that enter the Lake. Alternative, but still crude, estimates of urban elemental emissions and their wet and dry deposition in the lake are made here. Observed elemental concentrations in urban air are used to calculate emissions and recently measured wet and dry deposition parameters are used to calculate deposition. All available treatments conclude that atmospheric inputs of at least Fe, Pb, Ti, and V are sizable fractions of total lake input of these metals. This study suggests tentatively that 1) wet and dry inputs from the atmosphere are about equal, 2) between 3 and 15 % of elemental pollutant emissions from Chicago and NW Indiana enter the Lake, and 3) this fraction increases with particle size.     

Dry deposition loading of Lake Michigan by airborne particulate matter

A transport model as a function of particle size is presented which couples Chicago area meteorological data through the mixed layer with laboratory and field data on water surface dry deposition. The model is used to (a) estimate a minimum mass transfer efficiency by dry deposition from the Chicago area to Lake Michigan, (b) compare this minimum with the maximum wet deposition likely, and (c) estimate the transfer efficiency of trace metals. Dry deposition is found to cause 15% or more mass transfer efficiency of aerosols to the Lake. This value is considered to be equal to or greater than the efficiency of precipitation scavenging mass transfer. However, dry deposition as a function of particle size is such that the transfer of trace metals by this mechanism appears to be a few percent or less. Consequently, precipitation scavenging appears to be the dominant mechanism for trace metal transfer to Lake Michigan.     

Water pollution in Lake Michigan by trace elements from pollution aerosol fallout

Certain trace elements which are strongly associated with air pollution sources in the Lake Michigan basin may be contributing significantly to lake water pollution by an atmospheric fallout route. In this paper a partial inventory of air pollution emissions for 30 trace elements is presented for the Chicago, Milwaukee, and northwest Indiana metropolitan areas, based on available published information. The inventory is then compared with actual stream inputs measured for Zn, Cu, and Ni and with estimates of pre-industrial unpolluted stream inputs for 28 elements. Evidence indicates that the atmosphere may now be a major source of Zn in Lake Michigan, and atmospheric inputs of Cu and Ni may also be considerable. Moreover, the evidence suggests that air pollution probably exceeds expected unpolluted stream inputs for many additional elements in Lake Michigan, highlighting the need for more comprehensive chemical data to quantify the evaluation.     

Lake Ontario atmospheric deposition 1969–1978

Nine years of atmospheric deposition data have been analyzed from six locations along the Canadian shore of Lake Ontario. Results indicate that atmospheric deposition is affected by large scale air masses which influence the entire northern shore, and local inputs which at times could mask the large scale air masses effects. The observed increase in acidity in atmospheric deposition in the early seventies may be due to an imbalance caused by a greater reduction in total suspended particles than in SO₂ emissions.     

Comment on water pollution in Lake Michigan from pollution aerosol fallout

The hypothesis that air pollution is a major source of some water pollution trace elements in Lake Michigan (Winchester and Nifong, 1971) is reexamined. Hazards evaluation techniques are used to assess the overall transfer efficiency of pollution from air to the lake. This efficiency was found to be at least 25%, which supports the hypothesis. It is suggested that the problem be studied taking into account local mesoscale systems (such as lake breeze) and the distribution of air trajectory, wind speed and stability categories.     

Wet and dry deposition of phosphorus into Lake Huron

The deposition rates for wet, dry, and integrated fallout of P to the southern portion of Lake Huron were determined. Samples were analyzed for water-soluble, acid (pH =2) soluble, and insoluble (bound) P. The term ‘available P’ was used to indicate the sum of the water- and acid-soluble fractions of P in each type of input. Of the integrated fallout samples, approximately one-third was present as available P. The deposition rate for dry fallout of available P was determined to be 1.7 ng cm^?2 day^?1. The wet deposition rate was estimated to be 2.2 ng cm^?2 day^?1 for available P. Total fallout of available P, determined from shore-based integrated fallout collectors, was calculated to occur at a rate of 6.5 ng cm^?2 day^?1. The difference between the wet-plus-dry deposition and the integrated deposition rates has been ascribed to the contamination of integrated fallout collectors by local sources (roads, agricultural activity, etc.) though attempts were made to minimize this problem. The presence of large quantities of biological material (pollen, algae, insect larvae) accounted for a large fraction of the difference observed, especially in the spring months.     

Input of pesticides by atmospheric deposition

Sampling and analytical methods were developed to examine the input of various pesticides on noncultivated areas of the FAM (Research Network on Agroecosystems) Research Station Scheyern. Off-target drift from pesticide application on nearby cultivated land, as well as input due to long-range atmospheric transport, were measured. The wet deposition was determined by a cooled wet-only sampler. Bulk samplers and specially designed samplers with glass-fiber surface were used for total deposition measurements. Analysis of pesticides was carried out using liquid/liquid or solid-phase extraction and high performance liquid chromatography-UV (HPLC-UV) or gas chromatography-nitrogen/phosphorus-sensitive detector/MS (GC-NPD/MS) detection. Obtained results demonstrated that for several compounds, total deposition, i.e. the sum of wet and dry deposition, was marginally higher than wet deposition alone. In contrast, total deposition data of pesticides having been applied near the sampling site exceeded wet deposition values by orders of magnitude. In addition to direct drift, determined as droplets depositing near pesticide application areas, an indirect drift represented by particle-associated or gaseous transport was observed, both of which contributed considerably to total deposition. Therefore, to determine the input of pesticides to nontarget areas in the close vicinity of pesticide application, direct and indirect drift, and background deposition must be considered.     

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.     

中国南方典型地区阔叶林大气氮沉降通量研究

A one-year study in a typical red soil region of southern China was conducted to determine atmospheric nitrogen （N） fluxes of typical N compounds （NH3, NH4-N, NO3-N, and NO2） and contribution of three sources （gas, rainwater, and particles） to N deposition. From July 2003 to June 2004, the total atmospheric N deposition was 70.7 kg N ha^-1, with dry deposition accounting for 75% of the total deposition. Dry NH3 deposition accounted for 73% of the dry deposition and 55% of the total deposition. Moreover, NO2 contributed 11% of the dry deposition and 8% of the total deposition. Reduced N compounds （NH4^＋ and NH3） were the predominate contributors, accounting for 66% of the total deposition. Therefore, atmospheric N deposition should be considered when soil acidification and critical loads of atmospheric deposition on soils are estimated.     

Long term effects of enhanced nitrogen deposition on a lowland dry heath in southern Britain

Experimental additions of ammonium sulphate to a nitrogen-poor dry heathland have been carried out since 1989. There are four nitrogen treatments: a control (receiving artificial rain only), a low treatment which receives an additional 7.7 kg N ha^?1 yr^?1, a high treatment receiving 15.4 kg N ha^?1 yr^?1 and an alternating treatment which receives either the control or the high nitrogen additions, in alternate years. The estimated background deposition at the study site is 13–18 kg N ha^?1 yr^?1, a value similar to the critical load that has been suggested for the conversion of lowland heath to grassland. Over the past 5 years there have been significant stimulations in shoot growth, flowering, canopy density and litter production. Flowering, in particular, strongly reflects nitrogen additions in the alternating treatment. Current models of the response of dry Calluna heathlaud to enhanced nitrogen deposition suggest that higher tissue nitrogen levels will occur and will be accompanied by heightened sensitivity to secondary stresses. This may in turn lead to canopy breakdown and replacement by grassland. The application of nitrogen at deposition rates only slightly in excess of the critical load over five years has produced small, non-significant increases in shoot nitrogen content. However, there is clear evidence of a large positive effect on shoot growth, flowering, litter production and canopy density of Calluna. The observation of these responses at the application rates used in this study supports the current proposals for critical loads of nitrogen for lowland heaths.     

大气氮湿沉降及其对惠州西湖水体富营养化的影响

根据2000～2004年广东省惠州市降水中氮浓度,采用单因子评估模式评价了大气氮湿沉降及其对惠州西湖水体富营养化的影响.结果表明,近5年惠州市湿沉降平均NO-3 -N含量为0.469 mg · L-1,NH 4 -N含量为0.391 mg · L-1,总无机氮(TIN)含量为0.861 mg · L-1,远大于富营养水体中氮浓度阀值(0.2 mg · L-1).湿沉降中氮含量呈逐年增加趋势,2004年湿沉降氮含量较2000年增加了近1倍.依据降水中氮浓度,2000～2004年湿沉降中总氮含量为Ⅲ～Ⅳ类水;而降水氮含量季节变化中,总氮为Ⅱ类～劣Ⅴ类水,Ⅴ和劣Ⅴ类水质开始频繁出现.湿沉降每年输入惠州市的TIN为16.26 kg · hm-2,湿沉降中氮浓度已超过水体富营养化阈值.因此,湿沉降输入氮对惠州西湖水生态环境,特别是水体富营养化的影响值得关注.     

Comparison of RADM dry deposition algorithms with a site-specific method for inferring dry deposition

Data collected during 1986 at seven widely separated sites in the eastern United States were used to estimate weekly averages of deposition velocities for SO₂, O₃, HNO₃, and SO _inf4 ^sup2? with both a modified version of the RADM dry deposition module and a site-specific inferential technique developed by the Atmospheric Turbulence and Diffusion Division of the National Oceanic and Atmospheric Administration's Air Resources Laboratory. The results show some systematic differences between the two techniques, even when the module uses distributions of landuse types that match as closely as possible the observed vegetation coverages used in the inferential technique. When one ignores the systematic differences that easily could be removed by minor changes in the algorithms for computing resistances to deposition, weekly averages of the deposition velocities calculated with the two methods are within approximately ±30% of each other for SO₂ and O₃. Overall, the relative differences in the deposition velocities for HNO₃ and SO _inf4 ^sup2? are about ±30 and ±50%, respectively. Use of the module with landuse types extrapolated to areas as large as RADM grid cells (approximately 80 km square) around the measurement stations produces weekly averages within ±20% of the site-specific estimates for SO₂, O₃, and SO _inf4 ^sup2? and approximately ±30% for HNO₃ if one avoids landuse types such as urban and water areas that are both nonrepresentative and have very different characteristics from the measurement sites. These estimates are not complete measures of the true uncertainty associated with the two techniques because they do not account for such effects as differences in the siting of instrumentation for collecting input data and the inability of the computational algorithms to include the many surface nonuniformities that typically exist in the areas surrounding measurement sites.     

Trace element concentrations and background values in the arid soils of Hormozgan Province of southern Iran

Trace element concentrations in soils of arid regions of southern Iran are described to assess the concentration ranges of selected elements in a variety of soils and rocks, and to evaluate the potential bioavailability of trace elements in relation to soil properties. The study area was classified into three sub-regions consisting of (1) shale, gypsum, and limestone (western part), (2) igneous rocks and limestone (northern part), and (3) sandstone and limestone (eastern and northeastern part). The gained background values of trace elements were used for evaluating the quality and degree of contamination with native and also with anthropogenic elements of studied soils. Some soil samples indicated a significant enrichment for Pb and Ni, with an enrichment factor (EF) of around 6.0. Soils have only been cultivated for few years compared to hundreds and thousands of years for many agricultural soils; therefore, there has been less crop removal. Furthermore, soils are not highly weathered because they are in an arid climate with low precipitation, which results in a slow rate of weathering. However, slight elemental differences between soil horizons indicated that most soils are poorly developed and also represented the similarity of trace element contents between soils and parent materials.     

Evidence for acidification of sensitive Scottish soils by atmospheric deposition

The Scottish soils most sensitive to acidification from acid deposition are peats and those derived from quartzite or Devonian and Torridonian sandstones. It is shown that the surface horizons of Calluna moorland podzols derived from these mineral parent materials behave in a similar way to peats, in that their pH depends upon cation exchange equilibria between H⁺ and Ca²⁺. The pH is therefore related, as might be expected from the ratio law, to the ratio [H⁺]:[Ca²⁺], and this relationship may be used to predict the effect of emission reductions or increases upon these soils.     

Measured values of the dry deposition velocities of atmospheric aerosols carrying natural and fallout radionuclides using artificial collectors

The dry deposition velocitiesVg of aerosols carrying (a) fallout beta activity from nuclear tests, (b) natural radioactivity due to thoron daughter²¹²Ph (Th-B) and (c) cosmic-ray produced⁷Be have been measured in Bombay, India, using artificial collectors consisting of trays with a thin layer of water to retain the deposited material. The location of Bombay is eminently suitable for such measurements in view of the existence of a long dry period of several months without any rainfall. The measuredVg values (cm s^?1)) are 0.063 ± 0.06 (1 S.D.) for fallout beta activity from 900 daily readings, 0.033 ± 0.03 (1 S.D.) for²¹²Pb from 80 daily measurements and 0.023 ± 0.014 (1 S.D.) for⁷Be from 23 bi-monthly measurements. A study of the associated meteorological parameters showed some correlation with wind velocity only in the case of radioactive fallout.     

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。     

Atmospheric input of trace metals to Lake Michigan

Atmospheric bulk deposition was collected on a monthly basis in the Lake Michigan basin from September 1975 through December 1976 to determine the atmospheric loading of trace elements to Lake Michigan. The sampling network consisted of bulk collectors located at 21 locations in the northern and southern basin. Atmospheric loading rates to Lake Michigan were estimated as (in units of 10⁵ kg yr^?1): Al-50; Fe-28; Mn-6.4; Zn-11; Cu-1.2; Pb-6.4; Cd-0.11; Co- <0.25; Ca-798; Mg-155; Na-110; K-64. Atmospheric deposition of all elements measured was greater in the southern basin than in the northern basin as a result of intense urban/industrial activity in the former. The percentage of total atmospheric deposition falling in the southern basin was: Fe-74%, Al-71%; Mn-75%; Zn-67%; Cu-62%; Pb-78%; Cd-74%; Co- ti 56%; Ca-79%; Mg-62%; Na-65%; K-61 %. Atmospheric loading rates reported are in general agreement with estimates made by others from emission inventories and aerosol concentrations. Atmospheric loadings were estimated to represent 10% or more of the total loadings to Lake Michigan from tributary and erosion sources for the trace elements Mn, Zn, Cu, Cd and Pb. Also, atmospheric deposition may account for recent accumulations of Zn, Cu, Cd, Pb and Co in southern Lake Michigan surficial sediments. The atmospheric Ph flux to southern Lake Michigan was estimated as ～1.7 μg sm^?2 yr^?1 for 1975–1976 which compares favorably with the 1972 anthropogenic Pb flux of 1.3 μg cm^?2 yr^?1 (total ? ～1.5 μg cm^?2 yr^?1) as determined from Pb-210 dating (Edgington and Robbins, 1976). The geographical distribution of trace element loading implicates the southern periphery of Lake Michigan as the principal emission source area.     

Cadmium in the Southern Basin of Lake Michigan

Recent measurements of Cd concentrations in the tributaries, waters, and sediments of Lake Michigan's southern basin, as well as in rain and airborne particulate matter over the lake, permit the establishment of a preliminary mass balance for this element. Atmospheric inputs are found to dominate (60%); sedimentation is the major removal mechanism (> 90%). The estimated present input rate exceeds the estimated loss rate by a factor of about 2.5, implying that the Cd concentration will increase from its current value of ～ 20 ng l^?1 in off-shore waters. We have applied a simple model to predict future Cd concentrations given various assumptions about potential increases in input rate. According to the model, even modest rates of growth in the annual input of Cd could lead within a few decades to concentrations in the range where deleterious effects on zooplankton communities are readily observable.     

大气氮素沉降研究进展

人为干扰下的大气氮素沉降已成为全球氮素生物化学循环的一个重要组成部分。作为营养源和酸源, 大气氮沉降数量的急剧增加将严重影响陆地及水生生态系统的生产力和稳定性。本文从大气氮沉降对土壤和水体环境、农业和森林生态系统以及生物多样性等方面综述了近年来国内外大气氮素沉降的研究现状及其对生态系统的影响, 并总结探讨了前人采用的大气沉降氮测定方法, 展望了我国大气氮沉降的研究前景。     

Forest canopy transformation of atmospheric deposition

Solute fluxes to the ground in open plots and under the forest canopy of different species were investigated in a number of long-term ecosystem studies in West Germany. From the canopy flux balance, rates of interception deposition and canopy/deposition interactions were assessed. Chemically, both open precipitation and throughfall are dilute solutions of H₂SO₄ and HNO₃ and their salts. For the sites investigated, mean pH in bulk precipitation ranged from 4.1 to 4.6, and in throughfall from 3.4 to 4.7. The increase in acidity after canopy passage at most sites indicates considerable interception deposition of strong acids to the forest stands, exceeding the rate of H+ buffering in the canopy. Evidence for buffering processes can be directly deduced from the fact that on sites with high soil alkalinity and high foliage base status, throughfall pH is usually higher than precipitation pH. Furthermore, the same idea can be concluded from changes in solution composition after canopy passage: the H⁺/SO _inf4 ^sup2? ratio is decreasing at most sites, while alkali earth cations from exchange processes occur in throughfall (Ca²⁺/SO _inf4 ^sup2? ratio increases). Solution composition and element flux data are presented for each of the sites, and the regional, orographical and site specific (species composition, ecosystem state) differentiations are discussed. A method for the assessment of total deposition and of canopy interactions such as H⁺-buffering and cation leaching is described, and results of calculations are shown. From these calculations it is concluded that forest ecosystems in Germany receive mean H⁺ loads of ca. 1 to 4 keq H⁺ · ha^?1 · a^?1 from atmospheric deposition. Acidity deposition rates seem to be related to a few key factors such as regional characteristics and ecosystem characteristics.