Long-term trends in the chemistry of precipitation and lake water in the Adirondack Region of New York,USA

Long-term changes in the chemistry of precipitation (1978–94) and 16 lakes (1982–94) were investigated in the Adirondack region of New York, USA. Time-series analysis showed that concentrations of SO₄ ^2–, NO₃ ^–, NH₄ ⁺ and basic cations have decreased in precipitation, resulting in increases in pH. A relatively uniform rate of decline in SO₄ ^2– concentrations in lakes across the region (1.81±0.35 eq L^–1 yr^–1) suggests that this change was due to decreases in atmospheric deposition. The decrease in lake SO₄ ^2– was considerably less than the rate of decline anticipated from atmospheric deposition. This discrepancy may be due to release of previously deposited SO₄ ^2– from soil, thereby delaying the recovery of lake water acidity. Despite the marked declines in concentrations of SO₄ ^2– in Adirondack lakes, there has been no systematic increase in pH and ANC. The decline in SO₄ ^2– has corresponded with a near stoichiometric decrease in concentrations of basic cations in low ANC lakes. A pattern of increasing NO₃ ^– concentrations that was evident in lakes across the region during the 1980's has been followed by a period of lower concentrations. Currently there are no significant trends in NO₃ ^– concentrations in Adirondack lakes.     

Role of precipitation chemistry versus other watershed properties in Wisconsin lake acidification

Data for over 100 watershed properties, including aspects of topography, hydrology, geology, soils, vegetation, lake morphometry and input precipitation chemistry, have been developed since 1980 for 316 watersheds in northern Wisconsin. The hypothesis being evaluated for this lake population is that the observed water chemistry, can be accounted for as a function of antecedent water and chemical inputs, after considering exchange processes in the lake and watershed and the lake/groundwater interactions. The variables found by regression analysis to explain observed variability in color, sulfate, and acid neutralizing capacity (ANC) levels in Wisconsin lakes are: for color, vegetative characteristics, mean depth, and water renewal times; for sulfate, precipitation concentration of sulfur, evaporative concentration, and lake water renewal time; ANC appears to be controlled by the size of the watershed, lake depth or water renewal time, and the intensity of anthropogenic inputs and cultural developments in the watershed. These results differ from previous studies in Wisconsin and nearby areas of Michigan and Minnesota by indicating that in some lakes acidity may not be in equilibrium with current precipitation chemistry.     

近地表土壤水分条件对坡面土壤侵蚀过程的影响

 采用人工模拟降雨实验,研究近地表土壤水分条件对安塞黄绵土和杨陵塿土土壤侵蚀过程的影响,尤其是土壤水分饱和条件下的土壤侵蚀过程。结果表明:土壤质地对入渗和径流过程有较大影响。对同一质地的供试土壤,随着前期近地表土壤含水量的增大,入渗量减少,而径流强度增大,坡面初始发生产流时间也越早。当前期近地表土壤含水量相近时,杨陵塿土的初始产流时间早于安塞黄绵土,坡面径流量和侵蚀产沙量也随前期近地表土壤水分含量的增加而增大。对于安塞黄绵土,当前期土壤含水量分别为饱和含水量的100%、75%和50%时,其径流量分别占饱和含水量的25%时的2.5、2.2和1.3倍,其侵蚀产沙量分别为50、25和1.3倍。而对于供试土壤为杨陵塿土,当前期土壤含水量分别为饱和土壤含水量的100%和50%时,其径流量分别是占饱和土壤含水量的25%时的1.1和1.0倍,其侵蚀产沙量分别为6.5和2.0倍。在降雨过程中,前期土壤含水量越大,片蚀发展为细沟侵蚀的时间越早,而且细沟侵蚀也越严重。     

Effects of liming on nutrient limitation of epilithic algae in an acid lake

The processes of lake acidification and lake restoration frequently involve major changes in DIC and DIN, both of which may potentially limit algal growth. We evaluate nutrient limitation of benthic algal biomass and species abundances during summers 1987 and 1989, before and after the liming of Lake Earnest (NE Pennsylvania) in November 1988. Limestone addition caused immediate increases in pH from 4.7 to 7.2. Alkalinity was ?34 μeq L^?1 in summer 1987, but rose to 620 μeq L^?1 in summer 1989, whereas DIN declined from 10.7 μmol L^?1 to 1.1 μmol L^?1 The algae were sampled after 45 to 46 d from clay flower pot substrates diffusing combinations of N, P and C. Algal biomass was strongly C-limited in 1987, but NP-limited in 1989. Mougeotia sp., which comprised >99% of total algal biovolume prior to liming, declined to < 1% of the community on control substrates, while Oedogonium sp. increased to 43% of total biovolume in 1989. The stimulation of chlorophyll-a accrual with C-enrichment during 1987 was consistent with the later increase in chlorophyll-a on control substrates following liming. Species enhanced by the diffused nutrients, however, generally differed from those which dominated the natural community.     

Patterns of water chemistry among twenty-seven oligotrophic lakes in Kejimkujik National Park,Nova Scotia

A cluster analysis was used to apportion 27 oligotrophic lakes in southwestern Nova Scotia into five multivariate groups on the basis of patterns of covariation of 11 chemical variables (Cl, SO₄, Gran alkalinity, organic anions, Ca, Mg, K, Na, H⁺, and color). These groups are described in terms of the average values of the chemical variables. The relationships among the groups were investigated by an ordination by detrended correspondence analysis. The first, and by far the strongest axis of the ordination separated lakes with relatively large concentrations of alkalinity, from strongly colored lakes with large concentrations of H⁺ and organic anions. Axis 2 separated acidic lakes, from lakes with large concentrations of Ca and alkalinity.     

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.     

Rain,snow and lake water chemistry on and near the Precambrian Shield of Western Canada

Regional surveys of rain, snow and lake water chemistry have been conducted in several locations of western Canada which are considered sensitive to acidic deposition and are within several hundred kilometres of major Canadian point source emitters (664,000 tonne S0₂ in 1981). Snow and rain in the western Precambrian Shield is acidic with pH values generally ranging between 5.0 and 6.4. However, there is little evidence to suggest that the area is receiving significant amounts of acidic deposition. Total deposition of sulphate is approximately 2 kg ha^?1 between the months of April to October in 1983. Environmental impacts at present are minimal with most small lakes in the region having pH values near nuetrality and low concentrations of metals such as Al.     

Seasonal variations of water chemistry in oligotrophic streams and rivers in Kejimkujik National Park,Nova Scotia

The seasonal patterns of flow and the concentrations of color, Mg, Ca, H⁺, Na, Cl, organic anions, SO₄, and Gran alkalinity are examined for five streams or rivers in Kejimkujik National Park (Lower Mersey River, Atkins Brook, Grafton Brook, Pebbleloggitch Brook, and Beaverskin Brook). These range in organic color and acidity from very darkwater Atkins Brook (average 191 Hazen units, pH 4.2) to clearwater Beaverskin Brook (5 Hazen units, pH 5.5). In general, most dissolved substances are present in a relatively large concentration during the high-flow period of winter-spring (most notably color, Mg, H⁺, Ca, Na, organic anions, and SO₄). In contrast, Gran alkalinity generally occurs in its highest concentration during the lowflow period. These observations suggest that during the high-flow period, substances are “flushed” from the terrestrial watersheds of these rivers and streams.     

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.     

Effects of tillage systems in dryland farming on near-surface water content during the late winter period

Tillage systems modify, at least temporarily, some of the physical properties of soil, such as soil porosity. Tillage also has an indirect effect on soil water content throughout the growth cycle, particularly in areas with a Mediterranean climate. This paper presents the results of monitoring the water content in the topsoil (0–0.20 m) of three adjacent plots during February to May cycles starting in 1994–1995 and ending in 1998–1999. Each of the plots had a surface area of 2700 m², an 8% slope and Calcic Cambisol soil. Starting in 1994, three different tillage systems were applied: conventional tillage, which is typical of the area (CT); minimum tillage (MT); and no-tillage (NT). Two vertical 200 mm TDR probes were permanently installed in each plot and measurements were taken every week. The results show that, under an NT system, the soil had significantly higher water content than the other two soil plots. However, this increased quantity of water did not denote increased crop production; on the contrary, these preliminary data point to a decrease in crop production.     

Addition of sulphuric acid to high organic carbon lake water: Effects on macro-chemistry,aluminium, and iron

A humic lake of pH 5.6 was acidified with H₂SO₄ to pH 4.1. Measurements of total and hollow-fiber ultrafiltered samples were made after three different times of storage, before and after the acid treatment. The nominal molecular weight cutoff of the hollow-fiber membrane was 10 kDalton. Assuming a linear molecular weight distribution of the organic complexes present in solution, the average organic molecule had an average molecular weight of 12.8?08 kDalton (n=6). Not only Ca²⁺ and Mg²⁺, but also detectable amounts of Na⁺ and K⁺ was found to be present on high molecular weight forms. No significant change in the molecular weight distribution of these elements were observed after the pH decrease. Changes in the molecular weight distribution after the acid treatment were only observed for Fe and Al. Significant amounts of SO₄ ^2? were present on high molecular weight forms. A small, but significant increase in the relative amounts of SO₄ ^2? present on high molecular weight forms was observed after the pH lowering. Kinetic constraints were demonstrated for dissolution of Al and Fe. To some extent, kinetic constraints in the equilibrium distribution of cation/anion exchange reactions of Al, Fe, and SO₄ ^2? were also observed. After the acid treatment, the cation exchange capacity (CEC) of the organic pool present was estimated to be at least 18.2±1.4 (n=3) μeq of positive charges per mg C, probably because the negative sites on the organic pool are either not totally protonated or occupied by other cations at pH 4.09. This CEC is of the same order as industrially made cation exchange resins.     

Trends in small lake water chemistry near Sudbury,Canada, 1983–1991

While many studies have documented improvements in chemical conditions of large lakes near Sudbury, Canada in response to reduced smelter emissions, few have examined changes in water chemistry of small lakes. We studied trends in water chemistry of 97 small (<10 ha), shallow (<15 m) lakes northeast of Sudbury that are important habitat for breeding waterfowl. Currently, many small lakes near Sudbury are acidified, with little acid-neutralizing capacity and with relatively high concentrations of Al, Mn, and Ni. We also present evidence of short-term improvements in pH and SO₄ levels, but demonstrate that, over a nine year period, there has been no consistent, long-term trend of chemical recovery. Chemical conditions in these lakes varied considerably between 1983 and 1991, and responded quickly to changes in precipitation levels. However, the present condition of most lakes suggests that further reductions in emissions will be required to improve these habitats for breeding waterfowl.     

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.     

Variations in the acid content of rain water in the course of a single precipitation

The major acid components in the rain water collected during five different rainfall events in July and August 1977, were found to be a strong acid, the weak acid NH _in4 ^su+ and dissolved CO₂ from the atmosphere. Variations in their concentrations were determined as a function of time in the course of each of the rainfall events. Two experimental methods were used in this investigation, a microtitrim etric method and a coulometric method, and the data were analyzed by the use of modified Gran functions. Both methods gave the same results. The most significant observation was that the strong acid concentration increased from very low values to a maximum and then decreased in the course of a single rainfall event.     

Impacts of forests on water chemistry

Forest canopies and soil organic horizons have been identified as two major components of forest ecosystems interacting with and altering the chemistry of rainwater. Data, collected over a 13-yr period from different softwood and hardwood stands located in central New Brunswick, are presented to demonstrate differences among stands in their ability to alter the chemistry of rainwater. In both the canopies and the soil organic horizons, retention and exchange processes are effective in altering the chemistry of rainwater. Significant species effects are recognized in the partitioning of rainwater into throughfall, stemflow, and interception, and in altering of its chemistry. Stemflow components generally contribute to acidity, while throughfall reduces acidity of rainwater. Some of the chemical characteristics of rainwater reaching the forest floor are shown to be similar to those of streams associated with the forest stands. The data show significant species effects on the moisture retention characteristics of the organic materials accumulated under each stand, which in turn affect the residence time of the acid components of rain. Admittedly, before entering streams and lakes associated the composition of the liquid leaving the organic horizons is further altered by mineral soils.     

Effects of cold and warm years on the water chemistry at the Birkenes catchment,Norway

During the last years, several scientists have been concerned with the consequences of global warming. In the Birkenes catchment, situated in southernmost Norway, several warm years have occurred during the last decade. In this climatic region, warm years primarily mean warmer winters with mean air temperatures close to or higher than 0 °C. Small temperature changes are therefore decisive for the quality of precipitation, i.e. whether the precipitation enters the catchments as snow or rain, which accordingly has large consequences for the residence time of water and its pathways through the catchment. Another important effect of higher winter-temperatures at Birkenes, is that stronger and more frequent seasalt episodes seem to occur. This may enhance the negative effects to aquatic organisms, because the most extreme concentrations of acute toxic Al-forms in streamwater are related to seasalt episodes during warm winters, when the precipitation comes as rain and thus leaves the catchment relatively fast through the uppermost soil layers. When seasalt-enriched water enters into the uppermost soil horizons, a large amount of sodium will be temporarily retained due to cation exchange processes, where sodium may substitute for H⁺ and cationic Al. At Birkenes, but also in similar acidified areas with high seasalt input, seasalt episodes are probably of greater importance for the periodic variations in streamwater H⁺ and Alⁿ⁺ than commonly recognized. Higher winter-temperatures may also change the timing of the highest streamwater fluxes of nitrate. This may have local consequences for the primary-production in the fjords, both quantitatively and qualitatively. Thus, global warming may have negative consequences for the surface water chemistry in near-coastal areas that also receive high amounts of acidifying atmospheric compounds, and may change the eutrophication status of many fjords.     

Effects of simulated acid precipitation on cadmium- and zinc-amended soil and soil-pine systems

In order to determine the effect of acid precipitation on the movement of Cd and Zn in metal-contaminated systems, Cd- and Zn-amended soil systems, with and without eastern white pine seedlings, were treated with solution at pH levels of 2, 3, 4, and 5.3 for a 10-week period. While the soil parameters measured were not significantly altered by the higher pH treatments, treatment at pH 2 decreased soil pH, base saturation, and leachate pH, and increased leachate metal content. The presence of the seedlings moderated the effects of the pH 2 treatment by a probable combination of root cation exchange capacity and plant uptake. Seedlings receiving the higher pH treatments exhibited the expected metal distribution pattern (roots ? stems = leaves), while the pH 2 seedlings exhibited a different pattern (roots = stems = leaves). Cadmium and Zn levels in the stems and needles of the pH 2 plants were significantly higher than levels in those of the higher pH seedlings, while levels in the roots treated with pH 2 solution were significantly lower. This unusual distribution pattern may be the result of root injury due to the highly acidic solution. Although metal distribution was clearly affected by the acid treatments, increased toxicity symptoms were not observed in seedlings subjected to soil applications of acidified solutions.     

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.

     

Bridging the gap between air quality and precipitation chemistry

Data sets recently have become available providing simultaneous, regional scale observations of ambient air quality and precipitation chemistry. The data cover parts of the greater northeastern United States. With certain key assumptions, the observations of ambient SO_x and NO_x concentrations can be linked with precipitation concentrations through Junge's concept of rainout efficiency, assumed to be qualitatively equivalent to the washout ratio. A preliminary comparison between data taken from the Sulfate Regional Experiment (SURE) and the parallel precipitation studies using Junge's approach reveals certain useful consequences. Apparent dramatic differences in SO_x and NO_x scavenging are found. Ratios between sulfate in the aerosol and in precipitation compared with trace elements suggest the importance of particulate scavenging processes. Such results show promise for simplified analysis of these data as approaches to differentiating mechanisms involved in cloud-precipitation chemistry.     

Peatland water chemistry in Central Ontario in relation to acid deposition

Thirty-one peatlands from two areas of central Ontario were sampled to assess the influence of acid deposition on peatland water chemistry. Factor analysis differentiated peatland water chemistry along three major axes of chemical variation, interpreted as axes of organic concentration, mineral concentration, and deposition influence. Water from the surface mats had a higher organic concentration than water from open pools. Mineral influence in peatland waters was reflected by higher concentrations of Ca, Mg, Na, and silica in fen pools compared to bog pools. The influence of high acid deposition in the Wanapitei study area was indicated by high concentrations of sulphate, Ni, Mn, and Cu, and lower pH compared to an area that has received less acidic deposition (Ranger). Regression analyses indicated that H⁺ variation in bogs could be largely explained by organic C concentration, but that sulphate concentration was also positively associated with acidity, while Ca was negatively associated with acidity.