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.     

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.     

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.     

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.     

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.     

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.     

Measurement of dry deposition to vegetative surfaces

The importance of dry deposition was assessed to oak and pine trees, in a hardwood and coniferous canopy, respectively. In both canopies, ambient particle and gas concentrations on the interior were decreased relative to perimeter concentrations due to dry deposition scavenging by the canopy. Deposition of all species was higher to perimeter leaves than to interior leaves, due both to the lower concentrations and the lower wind speeds in the sheltered interior. The deposition velocities measured to the pine needles were similar to the values measured to the oak leaves.     

The chemical composition of atmospheric precipitation from selected stations in Michigan

The pH and amount of rainfall from over 60 selected stations throughout northern and lower Michigan was determined from September 1972 to December 1974. Precipitation pH was determined for each station by calibrated electrode meters. The seasonal weighted average and median pH from all stations in the study was 5.0 and 6.3, respectively. Daily readings from stations throughout Michigan indicate that pH is dependent on the amount of rainfall and that variations in it are often locally controlled. Collectively the pH values suggest carbonic acid control for most of the state. Annual median pH varied from a high of 8.45 at Dimondale, a station located 1.5 km from a concrete tile plant in central Michigan to 4.65 at Vassar, a small town located east of several industrial centers in the thumb region of the state. A comparison of annual nutrient loading for NO ₃ ^? , SO ₄ ⁼ , Cl^?,PO ₄ ^≡ , Ca⁺⁺, Mg⁺⁺ Na⁺ K⁺ and pH of rainwater from selected stations revealed that the eastern U.S. stations reporting pHs < 4.02 have similar loadings for NO₃ but twice the SO₄ input found for rural areas of Michigan.     

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.     

Decay of sandstone in urban areas correlated with atmospheric aerosol

The decay of sandstone in urban areas has been investigated. Patterns and composition of the damage layers sampled on monuments and historical buildings are described. The elemental concentrations of black surface crusts are reported. Enrichment factors in relation to the sandstone and crustal rock composition have been calculated in order to point out the component due to atmospheric deposition. The presence of anthropogenic aerosol and its role in the process of damage is evidenced.     

Distribution of Trace Elements in Meromictic Pit Lake

Studies were conducted at the deepest location of the meromictic Piaseczno pit lake, southern Poland, which was created in abandoned sulphur opencast. Pearson correlation and PCA were used to established the relationship between the elements and physico-chemical parameters of the water, whereas discriminant test to study vertical and time differentiation of Cd, Pb, Sr, Cu, Zn, Mn, and Fe concentrations. The results indicated both vertical (except Cu and Zn) and time differentiations of studied elements in the lake water. The highest concentrations of Cd, Pb, and Sr were found in the monimolimnion, that of Mn and Fe in the anoxic water. Depth profiles of Cu and Zn did not show any pronounced trend. Pb and Sr distributions in the water were related to alkalinity, Cl^? and COD, Cd to alkalinity and Cl^?, Mn and Fe to the redox conditions, Mn to water pH, and Fe to the alkalinity. The upper (0–15 cm) layer of the sediment consisted mainly of S (24.2 Atom%), Fe (21.62%), Ca (18.4%), Si (14.3%), and (Al 6.3%) and reflected mainly processes proceeded in the anoxic water-sediment interface. Calculated accumulation coefficients (K _d) of the elements in the sediment are discussed.     

Wet and dry deposition of nutrients in Central Alberta

Dry and wet deposition rates of various forms of phosphate and N and of Fe, sulphate, Na, K, and silica ions are reported for a 1 yr period in central Alberta. The results are extrapolated from event samples of rain and snow, and from dry deposition samples in distilled water collectors and snowpack. Following corrections for contamination and evaporation the most reliable dry deposition rates are found for orthophosphate, organic and nitrate N, and Fe, sulphate, and K ions. Ion concentrations in snow are significantly lower than those in rain for ammonia, organic, and total N and for sulphate and silica ions. More than 50% of the concentrations of total phosphate and total N in wet deposition samples is dissolved or in fine particles (less than 0.45 μ) but only about one third of dry deposition sample concentrations is in such form. Dry-to-wet deposition ratios for the year exceed one for filtered total N, filtered total phosphate, Fe, and sulphate. The largest dry-to-wet deposition ratios are about 5 for sulphate and unfiltered total N.     

Procedures for estimating atmospheric deposition properties of organic chemicals

A rationale for procedures to estimate the climatological mean dry deposition velocity and precipitation scavenging ratio of organic chemicals is developed. Both deposition parameters depend strongly on vapor pressure, as it affects the partitioning between vapor and sorbed phases. Separate formulae are presented for vapor and sorbed fractions using their mass-weighted average to describe the deposition parameters for the total airborne concentration. Deposition of sorbed fractions is controlled solely by particle size, and methods for estimating the particle size are presented. Dry deposition velocity for the vapor fraction is derived by semiempirical analysis, and is found to depend on Henry's Law constant, molecular diffusion coefficients in air and water, and the chemical's reaction rate in water. Estimates of the dry deposition velocity for 5 chlorinated hydrocarbons are made and compared with observations. Estimates of the precipitation scavenging ratio are compared with observational data for 11 chlorinated or aromatic hydrocarbons. The estimates generally are within an order of magnitude of the measured values.     

Modeling of throughfall chemistry and indirect measurement of dry deposition

Precipitation over a forested watershed is altered by interaction with plant surfaces which act as a filter for airborne gases and particles. This results in a major transfer to the forest floor of materials captured, washed, and leached from the forest canopy. Sequential samples of wetfall and sequential samples of throughfall under deciduous and coniferous trees were collected and chemically analyzed for major anions and cations. A simple washoff, mixing model based on leaf area index was used to simulate throughfall chemistry and to decouple foliar exudation from dry deposition. Model results gave excellent predictions of the measured sequential throughfall using estimated values of dry deposition. The model can also be used to calculate dry deposition, if the sequential throughfall data and wetfall data are used as input variables.     

Identifying indicators of atmospheric nitrogen deposition impacts in acid grasslands

Atmospheric deposition of nitrogen has become a serious concern for nature conservation managers and policy makers. It has the potential to reduce species richness, increase the graminoid component of the sward, encourage species typical of more fertile conditions and alter the soil biogeochemistry of grasslands. Calcifugous grasslands (grasslands found on acid soils) are among the most sensitive to N deposition due to their poorly buffered soils and species typical of nutrient poor environments.Indicators have an important role to play in detecting the impact of nitrogen deposition on sites of conservation importance and assessing conservation status. This study investigates potential indicators of nitrogen deposition impacts that could be incorporated into site condition monitoring programmes such as the UK Common Standards Monitoring.Using two national surveys of calcifugous grasslands we examined the potential for using: the presence or absence of indicator species, the cover of indicator species, the species richness and richness of functional groups, and the cover of functional groups as indicators of N deposition impacts. Of all the potential indicators investigated, graminoid:forb ratio was found to be the best indicator of N deposition impacts. It showed a significant relationship to N deposition in both data sets and is quick and easy to assess in the field. Vegetation indicators must be used with caution as there is potential for vegetation management regime and nutrients from other sources to cause similar changes in species composition. Consideration must be given to these before attributing changes to nitrogen deposition.