Effects of varying air trajectories on spatial and temporal precipitation chemistry patterns

This study was designed to determine if judicious use of synoptic data and an operational trajectory model could identify probable source regions of anthropogenic pollutants in northeastern United States precipitation and thus relate receptor measurements to emissions data without consideration of the complex intervening meteorological and chemical processes. The storm event of April 8 to 10, 1979, was selected for intensive study. Precipitation chemistry data were obtained from event samples at six MAP3S sampling sites and from hourly samples at Brookhaven National Laboratory. Concentrations of hydrogen, sulfate, nitrate and ammonium ions were used as receptor data. Some emissions data for SO_x and NO_x were obtained from the MAP3S emissions inventory. Surface and upper air meteorological data were analyzed. Backward trajectories ending at each of the sampling sites during the precipitation period were computed with the Heffter Interactive-Terminal Transport Model using selected transport layers. Results show that concentrations of pollutant species in event precipitation samples were much higher at stations at end points of trajectories passing through the Ohio River valley than at stations with other trajectories. Likewise, concentrations at Brookhaven were much higher during the end period of a trajectory through the same region than with more northerly and more southerly tracks. The model produced back trajectories consistent with synoptic flows. Concentrations of air pollutants in precipitation were roughly proportional to the number of major pollutant sources along the trajectory. These results suggest that a larger number of studies might identify more restricted source areas or even establish a quantitative relationship between source emissions along a trajectory and concentrations in precipitation at receptor sites.     

Acidic precipitation: Considerations for an air quality standard

Acidic precipitation, wet or frozen precipitation with a H⁺ concentration greater than 2.5 μeq l^?1, is a significant air pollution problem in the United States. The chief anions accounting for the H⁺ in rainfall are nitrate and sulfate. Agricultural systems may derive greater net nutritional benefits from increasing inputs of acidic rain than do forest systems when soils alone are considered. Agricultural soils may benefit because of the high N and S requirements of agricultural plants. Detrimental effects to forest soils may result if atmospheric H⁺ inputs significantly add to or exceed H⁺ production by soils. Acidification of fresh waters of southern Scandinavia, southwestern Scotland, southeastern Canada, and northeastern United States is caused by acid deposition. Areas of these regions in which this acidification occurs have in common, highly acidic precipitation with volume weighted mean annual H⁺ concentrations of 25 μeq l^?1 or higher and slow weathering of granitic or precambrian bedrock with thin soils deficient in minerals which would provide buffer capacity. Biological effects of acidification of fresh waters are detectable below pH 6.0. As lake and stream pH levels decrease below pH 6.0, many species of plants, invertebrates, and vertebrates are progressively eliminated. Generally, fisheries are severely impacted below pH 5.0 and are completely destroyed below pH 4.8. At the present time studies documenting effects of acidic precipitation on terrestrial vegetation are insufficient to establish an air quality standard. It must be demonstrated that current levels of precipitation acidity alone significantly injure terrestrial vegetation. For aquatic ecosystems, current research indicates that establishing a maximum permissible value for the volume weighted annual H⁺ concentration of precipitation at 25 μeq l^?1 may protect the most sensitive areas from permanent lake acidification. Such a standard would probably protect other systems as well.     

Assessment of the use of principal components analysis to relate air and precipitation chemistry to climate

A classification of atmospheric circulation was derived using principal components analysis (PCA) of daily sea level pressure over a 10 year period. Correlation coefficients of up to 0.65 were obtained between the individual principal component loadings and monthly means of gas and precipitation ion concentrations for a Scottish and a Norwegian station from the European Monitoring and Evaluation Programme (EMEP) network. The mean synoptic patterns of months predicted to have high or low gas and ion concentrations from their component loadings agreed well with previous work. High concentrations occur frequently with southerly flow or anticyclonic conditions, and low concentrations with westerly and northwesterly flow. We conclude that the PCA classification is a sensible method to use to derive circulation pattern-pollutant relationships, and is an encouraging first step to use the general circulation model (GCM) projections of future climate to assess possible future air/precipitation composition patterns     

Relationships between precipitation chemistry and some meteorological parameters in the Netherlands: a statistical evaluation

Bulk precipitation was sampled every 2 weeks for more than 2 yr in a lowland catchment in the eastern part of the Netherlands and dissolved constituents were determined. This paper discusses only concentrations of the main constituents: S0₄, NH₄, Cl, NO₃, Na, Ca, H, Mg, and K (in decreasing order) and tries to delineate specific source regions for these ion species. Despite the complex character of precipitation chemistry and the rather long sampling interval, statistical evaluation (cluster- and discriminant analyses) of the data provided discriminating results. Four sources could be distinguished: seaspray supplying major part of Na, Mg, and CI; industrial activities (Ruhr area) contributing excess amounts of Cl and SO₄ in association with NH₄; rural activities supplying N0₃, while K, Ca and excess amounts of Na and Mg mainly derive from local dust. No clear source area could be detected for H, but it was shown that SO₂-emission is the main source of acidification of precipitation at the study catchment.     

Some measurements of air quality and precipitation in Saint John,N.B.

For the period of November 19 to 23, 1973, and July 13 to 23, 1974, air quality and precipitation measurements were made in and around Saint John, New Brunswick. For both periods it was found that SO₂ concentrations could be appreciable at several locations (with hourly maxima near 40 pphm). Sulfur dioxide fumigation from a power plant plume and H₂S concentrations near a Kraft process pulp and paper mill are discussed. For the July period, O₃, NO and NO₂ were measured in the background air as well as in air downwind of the city. The ambient concentrations were not unusually high, with the O₃ reaching levels up to 8 pphm (hourly average) on clear sunny days. Precipitation samples were collected on several occasions and the analyses indicate that concentrations of acid-forming species were not markedly different from those found in other Canadian cities.     

Measurement and modeling of Western Washington precipitation chemistry

Water, Air, & Soil Pollution - Precipitation was collected and chemically analyzed for a 1 yr period at four sites in Western Washington. Spatial and seasonal variabilities in concentrations...     

Influence and prevention of bird-droppings in precipitation chemistry experiments

An effective device for keeping away birds during precipitation chemistry experiments is described. It is shown that bird-droppings can have a great influence on the P0₄- K- and NH₄-content of precipitation samples.     

Calibration of collection procedures for the determination of precipitation chemistry

Precipitation is currently collected by several methods, including several different designs of collection apparatus. We are investigating these differing methods and designs to determine which gives the most representative sample of precipitation for the analysis of some 25 chemical parameters. The experimental site, located in Ithaca, New York, has 22 collectors of 10 different designs. The designs include bulk (wet and dry deposition collected together), wet only (only rain and snow) and wet/dry (collects wet and dry deposition separately). In every sampling period, which varies from 1 day to 1 mo, depending on the time variable being tested, the following chemical parameters are determined: conductivity, pH, Ca, Mg, Na, K, NH₄, N0₃, N_total Si0₄, PO₄, P_total, Cl, SO₄, DOC, Zn, Cu, Mn, Fe, Al, Ni, Cd, Pb, Ag, DDT, DDE, Dieldrin and PCB's. The results of the investigation lead us to conclude that:

1. Precipitation samples must exclude dry deposition if accurate information on the chemical content of precipitation is required.
2. Substantial contamination results when glass and plastic collectors are used to sample precipitation for inorganic and organic components, respectively.
3. The inorganic components of precipitation samples of low pH (3.5 to 4.5), with the exception of P0₄ and Cl, exhibited no significant change in concentration when stored at 4\dgC for a period of 8 mo. We believe this is due to the stabilizing influence of a large concentration of H ions.
4. If quantitative information on the chemical composition is required, precipitation samples should be collected at no longer than weekly intervals if immediate collection is not possible.

     

Analysis and assessment of precipitation chemistry at Caribou,Maine

Over the last 30 yr, Caribou, Maine has been the only U.S. collection site which has been a part of all four national precipitation chemistry networks. Due to its remote but strategically important location, the data from this site are very useful in evaluating transboundary transport of the major ions present in precipitation. This paper assesses the reliability of the Caribou data base and looks at the more recent data with the aid of the GAMBIT (Gridded Atmospheric Multilevel Backward Isobaric Trajectory) model. An examination of the historical data base indicates serious contamination problems in pre-1980 samples, particularly with S0₄ measurements. The trajectory climatology shows that the largest number of precipitation events track along the U.S. coast. Preliminary chemistry measurements indicate highest concentrations of H+ and S0₄ occur from events associated with trajectories passing through southern Canada.     

Aerosol and precipitation chemistry relationships at big bend national park

Aerosol chemistry, precipitation and visibility parameters are currently being measured at Big Bend National Park in Texas. This is part of a large-scale air resource evaluation program which the National Park Service is sponsoring in several southwestern national parks and monuments to determine the potential impact of local and distant pollutant sources on the environmental quality within these areas. Analysis of aerosol samples collected at six sites in the Southwest indicates that soil-derived components, organic materials and the acid-base ions of sulfate, nitrate, and ammonium are the major constituents of suspended airborne particulate matter in the remote areas of the arid region. Comparison of particulate matter chemistry and precipitation chemistry data at Big Bend National Park shows consistent features which indicate that the airborne alkaline soil material and NH₃ largely neutralize the atmospheric acidic species of H₂SO₄ and HNO₃. Given the similarity of the particulate matter composition and loading at the other monitoring sites, it is suggested that the trace chemical composition of precipitation will be similar in many remote regions of the Southwest.     

Mercury in precipitation and ambient air a new scenario

Theoretical calculations and experimental work, mainly consisting of bubbling ambient air through different synthetic solutions and natural waters and also bubbling Hg- and O₃-free air through precipitation samples, have given some new information. The oxidation process of Hg^o by means of O₃ in natural waters and in synthetic solutions has been clarified. The primary products are water soluble Hg-compounds which are reduced by SnCl₂. Subsequently volatile or nonvolatile Hg-species may be formed. These are not reduced by SnCl₂. Further it has been shown that in precipitation those Hg-forms, which are not reducible with SnCl₂ consist of non volatile species only. The dominant one seems to be highly dispersed and easily sorbed on to solid surfaces. It is reducible with NaBH₄. Besides this there is another one consisting of larger particles. Their core contains some Hg which can be released as Hg^o by a high temperature thermal process. Species with the same properties have also been observed in ambient air but in very low concentrations.     

Temporal variation in precipitation chemistry on the shore of the Chesapeake Bay

We studied precipitation chemistry at the Rhode River on the western shore of the Chesapeake Bay. We sampled on an event basis, beginning in 1973 for some constituents in bulk precipitation. Beginning in 1981, we also sampled wet precipitation separately from bulk precipitation. In this report, we examine temporal variability of precipitation chemistry at different time scales. Several constituents showed long-term trends. In bulk precipitation, hydronium concentration increased by 27% of its mean concentration per decade, calcium by 67%, ammonium by 28%, and nitrate by 25%, while organic nitrogen decreased by 41%, organic phosphorus by 31%, and organic carbon by 16%. In wet precipitation, ammonium increased by 33% and calcium by 100%, while magnesium decreased by 78% per decade. Concentrations differed greatly among precipitation events, increasing as the volume of precipitation decreased and as the interval since the previous event increased. Most constituents also showed marked seasonal variation. We used a regression model to predict concentrations for each event from month, precipitation volume, and the time since the previous event. We evaluated how much of the interannual variability could be explained by these factors. The event-scale model accounted for almost half of the variability among annual means for ammonium, sodium, and magnesium in bulk precipitation, and for potassium in wet precipitation. This suggests that much of the interannual variability of concentrations may result from interannual variation in the temporal distribution of precipitation.     

Multivariate statistical analysis of precipitation chemistry in northwestern Spain

149 samples of rainwater were collected in the proximity of a power station in northwestern Spain at three rainwater monitoring stations. We analyze the resulting data using multivariate statistical techniques. Firstly, the Principal Component Analysis shows that there are three main sources of pollution in the area (a marine source, a rural source and an acid source). The impact from pollution from these sources on the immediate environment of the stations is studied using Factorial Discriminant Analysis.     

Ten years of precipitation chemistry in Haifa,Israel

Rain event samples have been collected in Haifa, Israel, for nine hydrological years 1981 to 1990. Precipitation amount, pH, SO₄ ⁼, NO₃ ^?, Cl^?, NH₄ ⁺, Na⁺, K⁺, Ca⁺⁺, Mg⁺⁺ and alkalinity of rainwater samples were recorded. The sampling and analysis program was based on WMO recommendations for background networks. The sampling was performed manually, and the analysis was based on wet chemistry for ions and atomic absorptions for metals. Data of 187 rain samples showed that the average pH was 5.3±1.1∶ 26% of the rain events were below pH of 5.6 and 23% above pH of 7.0. Some simple chemical mass-balance considerations indicate that natural sources, sea salt and soil carbonates are the main contributors to rain chemistry. However, the presence of low pH events observed over the years suggests that the impact of anthropogenic emissions may overwhelm the buffering capacity of the alkaline aerosol.     

Step-wise analysis of precipitation and river chemistry trends in Atlantic Canada

Monotonic trends in hydrogen (H⁺), sulfate (SO₄ ^–2)and nitrate (NO₃ ^–) were calculated using non-parametric techniques at four Canadian Air and Precipitation Monitoring Network (CAPMoN) sites and six nearby river systems in Atlantic Canada for the period 1983–1991. Over the whole interval, there were increasing nitrate concentrations and deposition trends at three of the four monitoring sites and no trends in SO₄ ^–2 or H⁺ concentrations and deposition. We found that SO₄ ^–2 concentrations increased at three of our six river sites, NO₃ ^– increased at one site and H⁺ decreased at one site. River exports showed no trends in the entire study interval. The series were also analyzed in five year time windows, incremented by six months, to see if changes in trend presence or direction would occur, compared to trend analysis over the entire interval. We show that while trends in river chemistry do not contradict deposition patterns, the changes that occurred were not necessarily in step. We also found that the trends which we measured were the result of short-term changes as opposed to long-term continuous monotonic trends. The time lag between precipitation and chemistry trend changes seemed longer in basins dominated by softwoods than by hardwoods.     

Spatial and temporal variability in precipitation chemistry in the urban area of Greater Manchester

To investigate the spatial and temporal variability of acid deposition in the urban environment a small-scale intensive network of bulk collectors has been deployed around Greater Manchester, UK. This network has been in operation since 1986. The concentrations and deposition rates of non-marine (nm) sulphate, nitrate, ammonium, calcium and hydrogen are reported for 1994. Acidity was generally lower in the city centre of Manchester where calcium concentrations were highest. Calcium compounds in the urban atmosphere effectively buffer the precipitation acidity.     

Biology and chemistry of three Pennsylvania lakes: Responses to acid precipitation

The biology and chemistry of three northeastern Pennsylvania lakes was studied from summer 1981 through summer 1983 to evaluate lakes with different sensitivities to acidification. At the acidified lake (total alkalinity ≤ 0.0 μeq L^?1) there were fewer phytoplankton and zooplankton species than at the moderately sensitive lakes. The most numerous plankton species in all three lakes are reportedly acid tolerant. Among the benthic macro- invertebrates (BMI) there were more acid tolerant Chironomidae at the acidified lake, but more acid intolerant Ephemeroptera and Mollusca and a higher wet weight at the least sensitive lake. There were no differences among the lakes' BMI mean total numbers or mean number of taxa. The fish community at the acidified lake was dominated by stunted Lepomis gibbosus, but L. machrochirous were most abundant in the other lakes. Principal component analysis suggested a shift in all three lakes over the sampling period toward combined lower pH, alkalinity, specific conductance, Ca and Mg and higher Al and Mn. Such chemical changes have been associated with acidification. The rate and extent of acidification appeared to be controlled by geological and hydrological characteristics of the drainage basins.     

The effect of alkaline dust decline on the precipitation chemistry in northern Japan

The precipitation chemistry in northern Japan, especially Hokkaido, has been investigated since 1982. This area has often been found to have high concentrations of alkaline road dust (asphalt dust) in the air, caused by the use of studded tires during the winter. It is well known that the composition of precipitation in these areas is often dominated by asphalt dust including calcium bicarbonate. However, recently the concentration of asphalt dust in the air has decreased owing to a ban on the use of studded tires. Simultaneously, in precipitation, the lowering of pH values and the increase of hydrogen ion depositions have been occurring owing to the decrease of non-sea-salt calcium ions (nss-Ca²⁺) concentrations and depositions derived from asphalt dust. In addition, we found that a decrease of nss-Ca²⁺ firstly leads to a decrease of bicarbonate ions (HCO₃ ^?), the counter ion to nss-Ca²⁺ in asphalt dust. Therefore, the increase of H⁺ concentrations and depositions was great in comparison with the decrease of nss-Ca²⁺ concentrations and depositions in areas where the HCO₃ ^?concentrations, varied by pH, and depositions had been low. Furthermore, this variation was mainly observed in the ionic composition of snow cover and snowfall at sites along the Japan Sea in northern Japan during winter. In this area, the Acid Shock effect may become a serious problem from the decline of pH values in melting snow. Moreover, we found that ammonium ions and non-sea-salt sulfate ions depositions have also been decreasing in response to a decrease of nss-Ca²⁺ depositions, derived from asphalt dust. It seems that this phenomenon is caused by the decrease of asphalt dust concentrations in the air.     

Intra-urban precipitation quality: Hamilton,Canada

Intra-urban variability of H⁺ (as measured by pH) along with S, halogens and heavy metals are studied in bulk precipitation from a network of 11 collectors located in the city of Hamilton, Canada. Bulk precipitation is shown a useful indicator of both elemental intra-urban variability and sources. Precipitation acidity is an order of magnitude less within urban areas than of that measured outside the city. Bulk depositional characteristics are classified into three distinct patterns as influenced by industrial emissions (Cu, Cl, Fe, Mn, and V), urban sediments (Ca and Mg), and automobile emissions (Br and Pb). A substantial component of S and Zn loadings are attributed to anthropogenic sources from outside the city while a substantial component of Al, I, and Na loadings are attributed to natural sources.     

Some measurements of the pH and chemistry of precipitation at Davis and Lake Tahoe,California

Precipitation samples were collected at Davis and Lake Tahoe, California, in 1972–73 and 1977–78 and analyzed for pH and major cations and anions. Rain and snow in this region of northern California are derived primarily from winter cyclonic storms which move easterly from the Pacific Ocean over Davis and then Lake Tahoe. Precipitation at both sites was found to be more acid than water in equilibrium with atmospheric CO₂. Acidity at Lake Tahoe apparently increased over the 5-yr period of the study. Sulfate was the dominant acid anion in 1972–73 (not measured in 1977–78). A major source of sulfate in precipitation was probably industry in the San Francisco Bay Area, upwind of the study sites. Automobile exhaust emissions throughout the region, which contains three major interstate highways and several large urban centers, contribute both sulfate and nitrate precursors to the atmosphere. As in the Eastern United States, these strong acid anions are influencing precipitation chemistry in northern California, including the Sierra Nevada mountains.