Investigation of Differences between Field and Laboratory pH Measurements of National Atmospheric Deposition Program/National Trends Network Precipitation Samples

A study was undertaken to investigate differences between laboratoryand field pH measurements for precipitation samples collected from 135 weekly precipitation-monitoring sites in the National Trends Network from 12/30/1986 to 12/28/1999. Differences in pH between field and laboratory measurements occurred for 96% of samples collected during this time period. Differences between the two measurements were evaluated for precipitation samples collected before and after January 1994, when modifications to sample-handling protocol and elimination of the contaminating bucket o-ring used in sample shipment occurred. Median hydrogen-ion and pH differences between field and laboratory measurements declined from 3. 9 μeq L^-1 or 0. 10 pH units before the 1994 protocol change to 1. 4 μeq L^-1 or 0. 04 pH units after the 1994 protocol change. Hydrogen-ion differences between field and laboratory measurements had a high correlation with the sample pH determined in the field. The largest pH differences between the two measurements occurred for high-pH samples (>5. 6), typical of precipitation collected in Western United States; however low-pH samples (<5. 0) displayed the highest variability in hydrogen-ion differences between field and laboratory analyses. Properly screened field pH measurements are a useful alternative to laboratory pH values for trend analysis, particularly before 1994 when laboratory pH values were influenced by sample-collection equipment.     

Field and laboratory studies of exposures of brown trout to acid waters

Some recent work on the effects of acid waters on brown trout are presented. Laboratory bioassay experiments have demonstrated that yearling trout are relatively insensitive to pH >4.3. Aluminium is demonstrated to be extremely toxic with suppression of growth occurring at concentrations above 20 μg L^?1 at pH 4.4 to 5.2. Aluminium toxicity is reduced at high pH (5.9 and 6.3). Field studies carried out on 61 acidic and circumneutral streams in upland areas of England and Wales showed a strong relationship between water quality and standing crop of 1+ brown trout. Measured pH levels per se were too high to be directly toxic. On the other hand, heavy metal and Al concentrations could account for low or zero brown trout biomass in the more acidic streams. A mobile bioassay laboratory has been developed to allow controlled bioassay experiments to be carried out in the field. Natural and synthesised waters can be tested concurrently in multi-factorial experiments with in situ determinations of pH, Ca, Al (total and monomeric) and other water quality characteristics.     

Chemical characteristics and temporal trends in eight streams of the Catskill Mountains,New York

Discharge to concentration relationships for eight streams studied by the U.S. Geological Survey (USGS) as part of the U.S. Environmental Protection Agency's (U.S. EPA) Long-Term Monitoring Project (1983–89) indicate acidification of some streams by H₂SO₄ and HNO₃ in atmospheric deposition and by organic acids in soils. Concentrations of major ions in precipitation were similar to those reported at other sites in the northeastern United States. Average concentrations of SO₄ ^2? and NO₃ ^? were similar among streams, but base cation concentrations differed widely, and these differences paralleled the differences in acid neutralizing capacity (ANC). Baseflow ANC is not a reliable predictor of stream acidity at high flow; some streams with high baseflow ANC (>150 Μeq L^?1) declined to near zero ANC at high flow, and one stream with low baseflow ANC (<50 Μeq L^?1) did not approach zero ANC as flow increased. Episodic decreases in ANC and pH during peak flows were associated with increased concentrations of NO₃ ^? and dissolved organic carbon (DOC). Aluminum concentrations exceeding 300 Μg L^?1 were observed during peak flows in headwater streams of the Neversink River and Rondout Creek. Seasonal Kendall Tau tests for temporal trends indicate that SO₄ ^2? concentrations in streamwater generally decreased and NO₃ ^? concentrations increased during the period 1983–1989. Combined acid anion concentrations (SO₄ ^2? + NO₃ ^?) were generally unchanged throughout the period of record, indicating both that the status of these streams with respect to acidic deposition is unchanged, and that NO₃ ^? is gradually replacing SO₄ ^2? as the dominant acid anion in the Catskill streams.     

Geochemical Comparison of Stream Water, Rain Water, and Watershed Geology in Central Korea

A hilly to mountainous watershed in Chonju in central Korea does not receive acid rain (average pH: 6.2); however, the stream water in the granite watershed is slightly acidic (6.4–6.7) and contains a low concentration of Ca compared to the stream water in sedimentary and volcanic rock watersheds (6.8–7.6). Although the concentrations of Ca and Sr and the ⁸⁷Sr/⁸⁶Sr ratio in the stream water change in accordance with the watershed geology, the stream ⁸⁷Sr/⁸⁶Sr ratios are closer to the ⁸⁷Sr/⁸⁶Sr ratios of rain than to those of the substrate rocks, suggesting the selective but sluggish weathering of Ca-containing minerals neutralizes acid. The concentrations of trace metals (As, Cr, Cu, Mo, Ni, Pb) in the water are lower than those in rain and less dependent on the watershed geology, indicating that they originated dominantly from the atmosphere. This result is consistent with the stream water having Pb isotope ratios close to that of rain but distinct from that of the rocks. We assume that the soil pool of exchangeable ions dominantly contains atmospherically derived heavy metals, which are subsequently discharged into streams. It is likely that the poor acid-neutralizing capacity of granite makes the aquatic systems in the granite watershed in Chonju sensitive to atmospheric acidification.     

Temporal and Elevation-Related Variability in Precipitation Chemistry from 1993 to 2002, Eastern Erzgebirge, Germany

The Erzgebirge, part of the so-called former “Black Triangle”, used to represent the strongest regional air pollution of Central Europe. To test the hypothesis of deposition enhancement with height, an altitudinal gradient along a N-S transect from the Elbe river lowlands to the Erzgebirge summit was chosen to investigate chemical composition, elevation-related variability, temporal changes, and seasonal patterns of ion concentrations from 1993 to 2002. The following questions were to be answered: (1) Which role does orography play on the composition of precipitation?, (2) Does fog occurrence overrule the orographic influence?, (3) Are there changes in the past 10 years, and if so, why?, (4) Do relevant seasonal changes occur and why? Air streams from westerly and to a lesser degree south-easterly directions prevail. The average precipitation was ion-poor (23 μS cm^?1 and acidic (pH 4.5). Sulphate still was the dominant anion (52.3–59.9 μeq L^?1, while NH⁺ ₄ determined the cations (41.9–62.2 μeq L^?1. Ion concentrations decreased with altitude to about 735 m a.s.l. and subsequently increased. The seeder-feeder effect largely explains the chemical composition of precipitation; enhanced in winter through snow crystals. Sub-cloud scavenging does not explain the observed patterns. Fog occurrence enhanced the observed effects at higher altitudes. Deposition amounts doubled from the lowlands to the Erzgebirge summit. From 1993 to 2002, acidity decreased by about 50%, mainly due to reduced SO₂ -emissions.     

Atlantic salmon resources in the Northeastern United States and the potential effects of acidification from atmospheric deposition

The Atlantic salmon (Salmo salar) was formerly abundant in northeast coastal rivers in the United States from the Canadian border to the Connecticut River, and possibly as far south as the Delaware River. It was eliminated from most of its former range by a combination of overfishing, construction of dams impassable to migrating fish, and municipal and industrial pollution. Reproducing populations are now limited to a few rivers in Maine, but attempts are under way to reintroduce the species to some rivers where populations formerly existed. Most of the native Atlantic salmon rivers are low in acid neutralizing capacity and receive acidic precipitation. The third order streams are not now acidic; however, in some first and second order streams in Maine, pH episodically declines to 4.7 and Al increases to 350 μg g^?1. These conditions could be toxic to sensitive early life history stages of Atlantic salmon. Comparison of chemical conditions in two Maine rivers in 1980–1982 with those in 1969–1970 indicated that the streams have not become more acidic during this interval. Data on the sport catch of Atlantic salmon indicated that populations have generally remained stable or recently increased in the Maine rivers having naturally reproducing populations. The recent increase probably resulted from introductions of hatchery smolts to supplement natural reproduction, and the occurrence of strong year classes in 1978 and 1980. The population in one stream has declined significantly in recent years, but the cause of the decline is probably not related to acidic precipitation. Atlantic salmon resources in the U.S. have apparently not been adversely affected by atmospheric deposition at the present time.     

Release of cationic aluminium from acidic soils into drainage water and relationships with land use

The concentration of cationic monomeric aluminium (A1³⁺) was determined in streams draining areas in different land use. Relationships between the concentrations of A1³⁺ and companion ions were examined both for streams and for eluates from soil leached in the laboratory with simulated rainwater that ranged in pH and salt concentration. The concentrations of A1³⁺ were consistently greater in streams draining Sitka spruce woodland than in streams in adjacent catchments draining rough grazing. In no case was the A1³⁺ concentration governed by the solubility product of gibbsite. The concentrations of A1³⁺ were very closely correlated with excess anions (total inorganic anions minus basic cations) both for stream water and for eluates from soil leached with simulated rainwater at a constant pH equal to that of the soil (3.8). Exchangeable A1 was the source of A1³⁺ in leachates from soil in the laboratory and the displacement of exchangeable Al was the dominant process accounting for the levels of A1³⁺ in acidic streams. Hydrogen ions were much more important than basic cations in displacing exchangeable Al from the acidic soil used in the laboratory experiments and probably from soils in the field. The greater excess of inorganic anions in streams from Sitka spruce woodland probably resulted from a greater anion excess in the input water (acid rain) together with a greater NO, production in the soil. All three major anions, CI, SO₄ and NO₃ contributed to the greater anion excess.     

Soil Property Changes After Conversion from FOrest to Pasture in Mount Sacinka,Artvin, Turkey

Turkey's forests have been continuously facing conversion into both agriculture and pasturelands, causing not only degradation and fragmentation of forested lands but also negative changes in soil properties that have not been thoroughly investigated. In order to determine possible changes in some physical and hydrophysical soil parameters along with the dispersion ratio between natural coppice forests and the neighbouring forest‐to‐grassland converted areas, a foothill of Mount Sacinka in Artvin was chosen as a research area. Besides land use, possible effects of elevation change on soil properties due to the mountainous and moderately steep landscape of the region were also taken into consideration. The soil samples were analysed for soil texture, permeability, field capacity, bulk density, organic matter, pH and dispersion ratio. The results indicated that whereas permeability (43·05 mm h⁻¹ in forest and 18·82 mm h⁻¹ in pasture), field capacity (43·45% in forest and 38·08% in pasture) and organic matter (6·36% in forest and 5·34% in pasture) values turned out to be higher in forest soils, bulk density (0·91 g cm⁻³ in forest and 1·06 g cm⁻³ in pasture) and pH (5·89 in forest and 6·55 in pasture) values were low in grassland soils, meaning that conversion has negative effects on soil properties. Additionally, the mean dispersion ratios of 27·55% and 33·58% for forest and pastureland soils, respectively, indicated soil erosion problems in both land uses. In addition, as for elevation effect, forest soils especially showed better characteristics at higher elevations with high permeability, field capacity and organic matter and low pH and dispersion ratio. Copyright © 2015 John Wiley & Sons, Ltd.     

Macroinvertebrate Community and Chemistry of the Most Atmospherically Acidified Streams in the Czech Republic

We performed a comparative study of strongly acidified mountain streams covering 10 sites in the Czech Republic in the season 1999/2000. The aim of the study was to determine how acidification influenced macroinvertebrate community structure within a relatively narrow pH range. We focused on strongly acidified, non-humic running waters with low ionic content (pH < 4.6, total organic carbon < 10 mg l^?1, specific conductivity < 100 μS cm^?1) and minimum human influence in the catchment. The actual pH values ranged from 3.98 to 4.65, and concentrations of reactive aluminium ranged from 0.2 to 2.0 mg l^?1. Characteristic macroinvertebrates were the stoneflies Leuctra nigra, Nemurella pictetii, and Protonemura spp.; the chironomids Corynoneura spp.; and the caddisfly Plectrocnemia conspersa – the former two stoneflies formed together 46% of total organisms. The sites were divided into three groups with use of divisive classification. Individual groups reflected similarity in water chemistry, catchment characteristics, and geographical proximity. The largest biotic difference detected by PCA was in the abundance of stoneflies, mainly Diura bicaudata and Leuctra major. The strongest correlation with this gradient was shown by pH (and associated heavy metals), followed by the distance from source. The results show that even in such narrow pH range, the number of taxa is determined by the low pH value and related high concentrations of aluminium and heavy metals.     

Amendment of Acidic Coal Refuse with Yard Trimmings Compost and Alkaline Materials: Effects on Leachate Quality and Plant Growth

Establishment of vegetative cover on coal refuse stabilizes the pile surface and reduces off site deposition of acidic sediments and drainage water. Direct revegetation through the use of by-product amendments would eliminate the need for topsoil cover and provide a beneficial use for by-product materials. This 8 month greenhouse study investigated yard trimmings compost, flue gas desulfurization (FGD) by-product, and agricultural limestone (ag-lime) amendments for direct revegetation of hyper-acidic coal refuse and their effects on leachate and plant quality. Pots (30 cm tall × 15 cm diam) of coal refuse were amended with five rates of compost (0 to 200 g kg^?1), with and without sufficient agricultural limestone (ag-lime) to raise refuse pH to 7, and planted with orchardgrass (Dactylis glomerata). Compost increased leachate pH from <2 to 4.4, decreased specific conductance from >17 to <5 mmho cm^?1 (due to large decreases in Al, Fe, and S), and decreased leachate concentrations of several trace elements. The pH increase from ag-lime greatly reduced leachate Al, Fe, and S and largely masked any effects of compost addition. Because no plant growth occurred with compost only, after 2 months FGD (200 g kg^?1) was added to the upper 1/3 depth of compost-amended coal refuse. The FGD increased refuse pH to the range 4.2 (no compost) to 5.7 (200 g kg^?1 compost), decreased leachate Al and Fe, increased leachate B, and allowed vigorous growth of orchardgrass. When combined with FGD, compost increased downward movement of Ca and Mg. Although compost addition decreased plant growth at the first harvest due to N immobilization, application of mineral N fertilizer alleviated this problem in subsequent harvests. Compost did not increase orchardgrass growth when combined with ag-lime. With FGD, however, compost increased orchardgrass growth to levels above that for ag-lime and compost, in spite of increased plant tissue B.     

LIMESTONE PARTICLE SIZE AND RESIDUAL LIME CONCENTRATION AFFECT PH BUFFERING IN CONTAINER SUBSTRATES

The objective was to quantify how the concentration and particle size of unreacted “residual” limestone affected pH buffering capacity for ten commercial and nine research container substrates that varied in residual calcium carbonate equivalents (CCE) from 0.3 to 4.9 g CCE·L^?1. The nine research substrates contained 70% peat:30% perlite (by volume) with dolomitic hydrated lime at 2.1 g·L^?1, followed by incorporation of one of four particle size fractions [850 to 2000 μm (10 to 20 US mesh), 250 to 850 μm (20 to 60 US mesh), 150 to 250 μm (60 to 100 US mesh), or 75 to 150 μm (100 to 200 US mesh)] of a dolomitic carbonate limestone at 0, 1.5 or 3.0 g·L^?1. Substrate-pH buffering was quantified by measuring the pH change following either (a) mineral acid drenches without plants, or (b) a greenhouse experiment where an ammonium-based (acidic) or nitrate-based (basic) fertilizer was applied to Impatiens wallerana Hook. F. Increasing residual CCE in commercial substrates was correlated with greater pH buffering following either the hydrochloric acid (HCl) drench or impatiens growth with an ammonium-based fertilizer. Research substrates with high applied lime rate (3.0 kg·m^?3) had greater pH buffering than at 0 or 1.5 g·L^?1. At 3 g·L^?1, the intermediate limestone particle size fractions of 250 to 850 μm and 150 to 250 (20 to 60 or 60 to 100 US mesh) provided the greatest pH-buffering with impatiens. Particle fractions finer than 150 μm reacted quickly over time, whereas buffering by particles coarser than 850 μm was limited because of the excessively slow reaction rate during the experimental periods. Addition of acid from either an ammonium-based fertilizer or HCl reduced residual CCE over time. Dosage with 40 meq acid from HCl per liter of substrate or titration with HCl acid to substrate-pH of 4.5 were well-correlated with pH buffering in the greenhouse trials and may be useful laboratory protocols to compare pH buffering of substrates. With nitrate fertilizer application, residual CCE did not affect buffering against increasing pH. Residual limestone is an important substrate property that should be considered for pH management in greenhouse crop production under acidic conditions.     

Spatial Distribution of Acid-sensitive and Acid-impacted Streams in Relation to Watershed Features in the Southern Appalachian Mountains

A geologic classification scheme was combined with elevation to test hypotheses regarding watershed sensitivity to acidic deposition using available regional spatial data and to delimit a high-interest area for streamwater acidification sensitivity within the Southern Appalachian Mountains region. It covered only 28% of the region, and yet included almost all known streams that have low acid neutralizing capacity (ANC ≤20 μeq l^?1) or that are acidic (ANC ≤0). The five-class geologic classification scheme was developed based on recent lithologic maps and streamwater chemistry data for 909 sites. The vast majority of the sampled streams that had ANC ≤20 μeq l^?1 and that were totally underlainby a single geologic sensitivity class occurred in the siliceous class, which is represented by such lithologies as sandstone and quartzite. Streamwater acid-base chemistry throughout the region was also found to be associated with a number of watershed features that were mapped for the entire region, in addition to lithology and elevation, including ecoregion, physiographic province, soils type, forest type and watershed area. Logistic regression was used to model the presence/absence of acid-sensitive streams throughout the region.     

Mineralization-immobilization of soil organic S and oxidation of elemental S in subtropical soils under flooded and nonflooded conditions

Information on the influence of soil moisture on elemental sulphur (S⁰) oxidation and transformation into organic S in semi-arid subtropical soils is scarce. We studied the impact of three moisture regimes on the mineralization of soil organic S, and the oxidation and immobilization of S⁰ in acidic (pH 4.9), neutral (pH 7.1) and alkaline (pH 10.2) subtropical soils. Repacked soil cores were incubated under aerobic (40% and 60% water-filled pore space, WFPS) and flooded soil conditions (120% WFPS) for 0, 14, 28 and 42 days with and without incorporated S⁰ (500 µg g^-1 soil). Soil moisture had profound effects on these processes and the mineralization of native soil organic S, oxidation of applied S⁰ and transformation of S⁰ into soil organic S proceeded most rapidly at 60% WFPS, irrespective of soil pH. Mineralization of native soil organic S resulted in the accumulation of 34, 49 and 44 g SO₄^2--S g^-1 soil in acidic, neutral and alkaline soil in a 42-day period at 60% WFPS. The oxidation rate of added S⁰ during the initial 14-day period at 60% WFPS was highest in alkaline soil (428 µg S cm^-2 day^-1), followed by neutral soil (326 µg S cm^-2 day^-1), and lowest in acidic soil (235 µg S cm^-2 day^-1). These rates are several folds higher than those reported in earlier studies because now we computed the oxidation rates by including the amount of S⁰ that was immobilized to organic S. Of the applied S⁰ at 40% and 60% WFPS, 2.6% and 6.0%, 3.4% and 10.0%, and 9.4% and 14.4% oxidized to SO₄^2-, and 15.0% and 17.6%, 17.6% and 19.6%, and 17.6% and 23.6% transformed into organic S in the 42-day period in acidic, neutral and alkaline soil, respectively. These results suggest that in order to synchronize the availability of S with plant need, S⁰ may be applied well before the seeding of crops especially in acidic soils and in rainfed regions where soil moisture remains at less than 60% WFPS. Apparently no oxidation of S⁰ and significant reduction of SO₄^2--S (7, 53 and 78 µg SO₄^2--S g^-1 in acidic, neutral and alkaline soil, respectively) under flooded conditions suggest that S⁰ is least effective for correcting S deficiency in flooded soil systems such as rice fields.     

Processes Controlling Trace-Metal Transport in Surface Water Contaminated by Acid-Mine Drainage in the Ducktown Mining District, Tennessee

Former mining activities lasting 140 years in the Ducktown Mining District, Tennessee, USA, has contaminated the streams draining the district with acid-mine drainage (AMD). North Potato Creek and its major tributary, Burra Burra Creek, are two of the most heavily AMD-impacted streams in the district. The removal of dissolved metals from the water in these creeks is largely attributable to the sorption of Cu, Zn, Co, Al, and Mn on suspended hydroxide precipitates of Fe. The fraction of trace metals remaining in solution decreases with increasing pH in the sequence Pb?<?Cu?<?Zn?<?Co. The concentration of Fe in solution also decreases with increasing pH due to the formation of ferric hydroxide precipitates which accounted for up to 81.4% by weight of the total suspended sediment. The concentration of suspended sediment substantially decreases as the water of North Potato Creek flows through a large settling basin, where 1.3 (±0.3)?×?10⁶ kg/year of trace-metal-laden suspended sediment would be annually deposited. In spite of this attempt to purify it, the water discharged into the river is acidic (pH 3.6) and still contains high concentrations of dissolved trace metals, which would resorb on to suspended sediment and be ultimately transported to a downstream reservoir, Ocoee No. 3 Lake.     

Electrode pH error,seasonal epilimnetic pCO2, and the recent acidification of the maine lakes

Based on laboratory experiments involving standard pH protocols, on statistical analysis of data from the Eastern Lake survey, and on independent field evidence (1985–86), recent (post 1975) electrometric pH measurements for Maine lakes are reevaluated for accuracy. A standard pH protocol used in Maine up until September 1985 can introduce bias of ca. ?0.3 to ?0.4 pH units for representative epilimnetic samples with low CO₂ concentrations (near atmospheric equilibrium). The bias arises out of the very long electrode equilibration times for such samples. A new protocol using these same Ross combination electrodes provides pH estimates accurate within 0.03 pH units for a wide range of northeastern environmental samples, and independent of sample DOC and conductance. The new pH measurements, when paired with the earliest colorimetric measurements from the same Maine lakes, indicate that epilimnetic pH's may have increased significantly (by 0.1 to 0.2 units) since the pioneering lake surveys of G. P. Cooper (1938–44). Earlier, often-cited, reports documenting historical pH reductions in Maine lakes are apparently vitiated by analytical error in many modern electrode pH measurements. The error also affects the calibration of paleo-ecological models of recent lake acidification in New England.     

硫杆菌以及好养异养型硫氧化菌对元素硫的氧化

The prediction of the oxidation rate of elemental sulfur (S⁰) is a critical step in sulfur (S) fertilizer strategy to supply plant-available sulfur. An incubation experiment was conducted to determine the rate and amount of S⁰ oxidation in relation to the contribution of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria. After 84 days, 16.3% and 22.4% of the total S⁰ applied to the soil were oxidized at 20 and 30 ℃, respectively. The oxidation of S⁰ proved to be a two-step process with a rapid oxidation during the first 28 days and a slow oxidation from then on. The highest oxidation rate of 12.8 μg S cm^-2 d^-1 was measured during the first two weeks at 30 ℃. At 20 ℃ the highest oxidation rate of 10.2 μg S cm^-2 d^-1 was obtained from two to four weeks after start of the experiment. On an average the soil pH declined by 3.6 and 4.0 units after two weeks of experiment. At the same time the electric conductivity increased nine times. With the oxidation of S⁰ the population of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased. The corresponding values for Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased from 2.9 × 10⁵ and 1.4 × 10⁵ g^-1 soil at the start of the experiment to 4 × 10⁸ and 5.6 × 10⁸ g^-1 soil 14 days after S⁰ application, respectively. No Thiobacillus spp. was present eight weeks after S⁰ application. The results suggested that oxidation of residual S⁰ completely relied on aerobic heterotrophic S-oxidizing bacteria.     

Relationship Between pH and Stream Water Total Mercury Concentrations in Shenandoah National Park

The purpose of this study was to gather information on the spatial and temporal variation of stream water total mercury concentrations ([THg]) and to test the hypothesis that stream water [THg] increases as stream pH decreases in the Shenandoah National Park (SNP). We based our hypothesis on studies in lakes that found mercury methylation increases with decreasing pH, and studies in streams that found total mercury and other trace metal concentrations increase with decreasing pH. Stream water was collected at baseflow in SNP in April, July, and October 2005 and February 2006. Contrary to our hypothesis, stream water [THg] decreased with decreasing pH and acid neutralizing capacity. In SNP, stream pH and acid neutralizing capacity are strongly influenced by bedrock geology. We found that bedrock also influences stream water [THg]. Streams on basaltic bedrock had higher [THg] (0.648 ng L^?1?±?0.39) than streams on siliciclastic bedrock (0.301 ng L^?1?±?0.10) and streams on granitic bedrock (0.522 ng L^?1?±?0.06). The higher pH streams on basaltic bedrock had the highest [THg]. The variation in stream water [THg] occurred despite no known variation in wet deposition of mercury across the SNP. The findings of this study indicate that the SNP can be an important area for mercury research with significant variations in mercury concentrations across the park.     

Chemical and biological trends associated with acidic atmospheric deposition in the Rhode River watershed and estuary

The Rhode River estuarine/watershed system is a tributary of Chesapeake Bay located on the inner Atlantic Coastal Plain. Its soils are fine sandy loams. Bulk precipitation pH in the spring season declined from 4.95 in 1974 to 3.82 in 1981 and was 4.03 in 1985. The changes in pH of a forested primary stream were more related to changes in bulk precipitation pH than were the changes in pH of agricultural streams, reflecting the importance of other major terrestrial sources of acidity on agricultural systems. Surges in acidity and dissolved total Al concentration in primary (first order) streams reached extremes of pH 3.2 and 300 μg Al L^?1. Higher order streams were observed to have surges in acidity with pH minima below 5.0. Surges in acidity ocurred during accelerated groundwater percolation following storm events and did not coincide with surface runoff or snowmelt. One of the reasons why groundwater is more acidic than surface runoff is that the vegetation exchanges H30 ⁺ for alkaline cations in the soil and translocates these ions to the vegetational canopy. When it rains, subsequently, H₃0⁺ in the precipitation displace some of these alkaline cations from the canopy. The end result is that overland flow during storms is enriched in alkaline cations, while groundwater is enriched in H₃0⁺. Although the source of dissolved Al is dissolution of clay minerals with atomic ratios of Al to silicate of 1:l, 1:2, or 1:3, this ratio in stream water rapidly declined to 1:1200 due to loss of Al. On average, forest drainage was the most acidic, the highest in dissolved Al, and the lowest in Ca. Surges in acidity were most severe from pastureland, and next most severe from cropland. Total fluoride concentrations were high relative to Al from all three land uses. Rhode River spawning runs of Perca flavescens declined drastically from the early 1970s to essentially zero since 1981. Larval bioassays of acidity indicate negligible toxicity to Hyla crucifer, significant toxicity to Perca flavescens and drastic effects on Morone saxatilis at pH 5.0.     

The influence of organic acidity on the acid-base chemistry of surface waters in Maine,USA

Results from surveys of low-ANC lakes (high elevation, and seepage lakes), and of surface waters in dystrophic, acidic bogs, indicate that acidic precipitation and organic acidity are each generally necessary, but not solely sufficient, for chronically acidic status in Maine lakes. Acidic, low DOC (ANC < 0; DOC < 5 mg L^-1) lakes of all hydrologic types are acidic due largely to acidic deposition; high DOC (DOC > 30 mg L^-1) acidic seepage lakes are acidic due largely to organic acidity, and high DOC drainage lakes are acidic due to a combination of both factors. No low DOC drainage lakes are known with pH less than about 5.0, suggesting that organic acidity is necessary to depress lake pH values to below 5 in Maine at current deposition loadings,The dominant anion of low DOC, acidic waters is sulfate. Acidic waters with intermediate concentrations of DOC (5 to 30 mg L^-1), may be dominated by S04 and/or organic acidity. Seepage-input lakes were the only group to include both organically-dominated (37% of the acidic lakes) and S0₄-dominated members (63% of the acidic lakes). High DOC systems are typically low pH bogs, and are all organic acid-dominated.     

Bulk density and content,density and stock of carbon,nitrogen and heavy metals in vegetable patches and lawns of allotments gardens in the northwestern Ruhr area,Germany

Purpose

In view that soils are bodies and that processes such as storage and release of water, carbon, nutrients and pollutants, and aeration and rooting happen in these bodies, it is of interest to know the density of elements and compounds in soils. On the basis of soil bulk and element density of organic carbon (OC), N, and heavy metals in soils and of horizon thickness, stocks of these elements for garden soils were calculated.

Materials and methods

Fourteen gardens in four allotments of the northwestern part of the Ruhr area, Germany were investigated. The research included 14 vegetable patches, 13 lawns, 2 compost heaps, and 1 meadow. Volume samples were taken. The soil analysis included pH, soil bulk density, and OC, N, Pb, Cd, Zn, Cu, and Ni contents.

Results and discussion

The soils were from sandy loam to loamy sand. The pH was slightly acid and C/N ratio about 20. Soil bulk density was between 0.8 and 1.4 g cm^?3 and mean bulk density was 1.1 g cm^?3. Mean OC content was for compost 7.4 %, vegetable patches 5.2 % (0–30 cm depth), and lawns and meadow 5.8 and 5.2 % (0–5 cm depth). OC density for compost was 76 mg cm^?3, vegetable patches 56 mg cm^?3, and lawns 67 mg cm^?3 (0–5 cm). Mean OC stock in 0–30 cm soil depth in vegetable patches was 16.4 kg m^?2, lawns 15.5 kg m^?2, and meadow 11.1 kg m^?2. N contents were between 0.06 and 0.46 %. For compost, the mean was 0.39 %, vegetable patches 0.27 % (0–30 cm), lawn 0.28 %, and meadow 0.26 % (0–5 cm). Mean stock of N in 0–30 cm depth for vegetable patches was 0.84 kg m^?2, lawn 0.76 kg m^?2, and meadow 0.55 kg m^?2. For heavy metals in compost, vegetable patches, lawn and meadow, Cd contents were in the range of 1.7 to 3.0 mg kg^?1, Pb 49 to 152 mg kg^?1, and Zn 52 to 1830 mg kg^?1. The amounts stored per square meters in 30 cm depth were for Cd 0.6–1.1 g, Pb 15–52 g, Zn 41–440 g, Cu 4–39 g, and Ni 1–8 g.

Conclusions

Allotment gardens have a high capacity to store CO₂ as OC. Roughly, there will be 7–8 million tons of OC stored in the 1.3 million allotment gardens of Germany. The high amount of 8000 kg N ha^?1 could damage the groundwater when released by wrong soil management. Cd, Zn, Pb, Cu, and Ni amounts of 7.8, 1000, 300, 135, and 30 kg ha^?1, respectively, are a lasting burden.