Factors affecting the content of heavy metals in bulk atmospheric precipitation,throughfall and stemflow in central Bohemia,Czech Republic

Content of copper, manganese, lead, and zinc in samples of bulk precipitation, throughfall and stemflow has been studied in a forest area in central Bohemia. The sampling localities are situated on two types of bedrock, granite and cenomaniau sandstones. The content in bulk precipitation reflects the impact of fossil fuel emission sources and the vehicular sources of lead. The deposition rate of elements in throughfall, in comparison with that of the deposition on an open land, exhibits increased values in essential microelements (in Mn approx. 45 times, Zh-5 times, Cu and Cd-2 times), with significant seasonal fluctuations. The value of the same ratio for ecotoxic lead is 0.23. The enhanced flux of elements in throughfall is ascribed mainly to the metabolic processes of the trees. Differences in the chemical composition of throughfall and stemflow collected on stands with different kind of bedrock are ascribed to various degree of accessibility of the micronutrients and various intensity of their vegetation uptake.     

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.     

Ion Fluxes with Bulk and Throughfall Deposition along an Urban–Suburban–Rural Gradient

Fluxes of principal anions and cations with bulk and throughfall deposition during the growing period (April–September) were investigated for three years (2001–2003) at three sites differently exposed to the second biggest Lithuanian city – Kaunas. Fluxes of all investigated anions (SO₄ ^2?, NO₃ ^? and Cl^?) and most cations were found to be the highest in suburban area to compare with both – Rural and urban sites. The highest seasonal variability of monthly ion fluxes and the highest differences between throughfall and bulk fluxes (net throughfall) were recorded in suburban area. The highest throughfall enrichment by sulphur was detected in spring and the beginning of summer (April, May) in urban and especially in suburban sites. For nitrogen compounds (NO₃ ^?, NH₄ ⁺) positive net throughfall values were characteristic for urban and suburban sites and negative for rural site almost during the entire growing period. Uptake of NH₄ ⁺ ions was detected to be much higher of that for nitrates in rural area (46% vs. 22%). The most intensive enrichment of throughfall fluxes by K⁺ ions took place during the summer time (May, June, July), however, intensity of potassium leaching at the same amount of precipitation was the highest in suburban area.     

北京密云油松人工林对降水及其营养元素含量的影响

对北京密云水库库西油松人工林的林冠截留、穿透降水和树干茎流的观测和分析结果表明，单次降雨过程中的林冠截留量与林外降水量呈幂函数关系，而穿透雨量和树干茎流量跟林外降水量皆呈线性相关关系，它们占林外降水的比例分别为7．23％～87．39％，12．56％～91．58％和0．007％～1．77％。环境状况、气象条件和降水特性的不同是造成同一地区大气降水化学性质差异的主要原因；降水透过油松林冠层后，穿透降水和树干茎流中元素含量都有不同程度的增加。穿透降水中各元素含量变化均与降水时间间隔呈正相关，而与降雨强度和降水量呈负相关；除N外，树干茎流中P，K元素含量与降水特性的关系与穿透降水的相同。     

Patterns of acid deposition to a Danish spruce forest

Bulk precipitation and bulk throughfall was collected during the period September to November 1984 in a Danish spruce forest. Samples were analyzed for all major anions and cations as well as strong and total acidity. The acid load to the forest ecosystem was estimated adding the throughfall fluxes of protons (79 eq ha^?1mo^?1), ammonium (99 eq ha^?1mo^?1) and a calculated estimate oflthe protons buffered by exchange processes in the canopy (75 eq ha^?1 mo^?1). This is still a minimum estimate but it exceeds the proton load determined by pH measurement in bulk throughfall and bulk precipitation by factors 3 and 6, respectively. Throughfall fluxes of all major cations and anions except ammonium decreased with distance from the trunk.     

凉水国家级自然保护区原始红松林和人工落叶松林降雨的水化学特征

对凉水国家级自然保护区原始红松林和人工落叶松林2种森林类型的林外降雨、穿透雨和树干茎流中的无机态N、TN、11P、K＋、Ca2＋、Na＋、Mg2＋等养分元素进行测定,研究2种森林类型的水化学特征。结果表明：林外降雨中Ca2＋含量最高,TP含量最低,无机态N以N时．N为主,养分元素平均含量（以mg／L计）排列顺序为Ca2＋〉TN〉K＋〉Na＋〉Mg2＋〉TP,各养分元素在林外降雨中的季节变化较大,变化幅度最小的是Ca2＋;降雨经过林冠层后,穿透雨的水化学特征发生了很大变化,自7月开始,K＋、Mg2＋含量增加,Ca2＋在7月减少,8、9月增加,无机N含量降低,TP在原始红松林穿透雨中增加,在人工落叶松林中则减少;2种森林类型的树干茎流中,养分元素的含量存在明显的不同,但总体变化趋势一致,K＋、Ca2＋、Mg2＋的含量均大于穿透雨中的含量,自7月开始,TP、K＋、Ca2＋、Mg2＋含量均高于林外降雨中的含量,且在人工落叶松林中增加量要比在原始红松林中的高,无机态N均低于林外降雨中的含量。研究结果可为凉水国家级自然保护区森林生态系统养分循环的研究提供重要的本底资料。     

Vegetation,soils, and ion transfer through the forest canopy in two Nova Scotia lake basins

Characterization of the forest vegetation and soils in two adjacent; contrasting headwater lake basins located in Kejimkujik National Park, Nova Scotia was completed in 1980. Precipitation chemistry was studied during May to November, 1981–83 at two forested plots in each basin. There were 2012 stems ha^-1 in Beaverskin basin and 1816 stems ha^-1 in Pebbleloggitch basin. Beaverskin species composition was predominantly coniferous (72% of stems) while Pebbleloggitch was predominantly deciduous (52% of stems). Thickness and mass of organic soil layers were greater in Beaverskin. Mineral soil cation concentrations were similar. There were no differences between the basins in mean incident bulk precipitation pH. Mean volume-weighted pH for the period (73 collections) was 4.80. Sixteen percent of collections had a pH < 4.25. Sulphate deposition in incident bulk precipitation (May – November) ranged from 5.4–8.5 kg ha^-1 during 1981–83 while NO _inf3 ^sup- ranged from 0.04–0.93 kg ha^-1. The partitioning of incident precipitation into throughfall varied considerably (69%–38%) year-to-year. Temporal flux of ions did not differ significantly. Amounts of all major ions in throughfall especially SO _inf4 ^sup2- and base cations(Ca²⁺ + Mg²⁺ + K⁺ + Na⁺) were enriched.     

Elevational Patterns of Acid Deposition into a Forest and Nitrogen Saturation on Mt. Oyama, Japan

Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid deposition in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3 – 23.5 kg ha^?1 yr^?1 (annual inorganic total N deposition: 9.6 – 10.7 kgN ha^?1 yr^?1) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that in precipitation. The average soil surface nitrate concentration in 1998 was 140 µg g^?1 (the range: 21.1 – 429 µg g^?1, n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L^?1 (the range: 2.38 – 20.6 mg L^?1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.     

Long-Term Monitoring Study on Rain, Throughfall, and Stemflow Chemistry in Evergreen Coniforous Forests in Hokkaido, Northern Japan

Long-term study on acid precipitation monitoring at suburban forests in Sapporo city showed that bulk precipitation pH were below 4.8 in recent years. Throughfall and stemflow chemistry for two main coniferous species (Abies sachalinensis and Picea jezoensis) showed different regime for pH and element deposition. The mean annual pH values of throughfall and stemflow in Picea stand were 1.0 to 1.3 units higher than that of rain collected outside the forest. In contrast, mean annual pH of throughfall and stemflow in Abies stand were 0.3 to 0.5 units higher than that of rain. Mean annual inorganic nitrogen input via throughfall and stemflow were estimated 0.41±0.11 gN/m²/yr in Abies stand, 0.44±0.13 gN/m²/yr in Picea stand. Cation input via throughfall, especially for K, in Picea stand was 1.4 times as large as that in Abies stand. Mean annual input of S in both stands was the same level. The possible effects on surface soil properties and nutrient cycling in northern evergreen conifers was discussed.     

Chemistry of bulk precipitation throughfall,soil water and stream water in a small catchment in Devon,England

Monthly mean concentrations of potassium, calcium, sodium, magnesium chloride and nitrate-nitrogen were determined from samples of bulk precipitation, throughfall, soil water and streamflow collected weekly between April 1975 and September 1977 in a small catchment in Devon, England. Soil water concentrations are compared with the analysis of exchange capacity in composite soil samples. Rain contributed much sodium and chloride to total catchment output, and potassium was selectively enriched in throughfall. Calcium and magnesium concentrations were high in soil water samples and on the soil exchange complex.     

Element Inputs and Canopy Interactions in two Pine Forest Ecosystems in Berlin,Germany

For 3 years (1986-89), element fluxes with bulk deposition and throughfall were determined in a 40 yr. old pine plantation and a 80-140 yr. old mixed pine/oak stand in the Grunewald forest in Berlin. Although SO₄-inputs are very high (60 kg S·ha^?1.a^?1) due to the urban character of the study site, acid inputs are moderate because of the buffering action of airborne alkaline dusts. This is reflected in the high Ca-inputs (12 kg·ha^?1a^?1 in bulk precipitation). Acid neutralisation was also observed in the canopies and could be attributed to 60-80% to increased Ca- and Mg-fluxes in throughfall, stemming from foliage leaching and dust interception. Heavy metal inputs were low in comparison to other Central European study sites, the decrease in Pb-inputs over the 3-year period could be attributed to the increased use of unleaded gasoline since 1987. Total inputs and canopy leaching showed clear seasonal patterns for some elements: SO₄-, H-, Ca- and Mg-fluxes were higher in winter, on the other hand, K- and Mn-enrichment in throughfall showed two peaks, in early summer and late fall.     

Trends in Sulfate,Base Cations and H+ Concentrations in Bulk Precipitation and Throughfall at Integrated Monitoring Sites in Finland 1989-1995

Temporal trends in sulfate, base cation (Ca2+ + Mg2+ + K+), and H+ ion concentrations in bulk precipitation and throughfall samples collected over a seven year period (1989-95) in four forested catchments in Finland are presented. The catchments are in remote locations and span the boreal zone (61-69 °N). The stands represent old, undisturbed forests, and are composed of varying proportions of Scots pine, Norway spruce and deciduous species (mainly Betula spp.). Monthly SO₄ ^2- and H+ ion concentrations in bulk precipitation averaged over the study period and catchments were: 18.7 µmol L^-1 and 32.3 µmol L^-1. The corresponding values for throughfall were: 37.4 µmol L^-1 and 32.4 µmol L^-1. Sulfate and H+ ion concentrations in bulk precipitation and throughfall both showed negative linear trends, which were significant (p < 0.05) for the three southernmost catchments. Concentrations and trend slope decreased northwards (e.g., bulk precipitation SO₄ ^2- slope estimates: ^-1.6 to ^-1.0 µmol L^-1 yr^-1). The decline was greater for throughfall than for bulk precipitation, indicating a proportionally greater reduction in dry deposition than wet. The sum of base cation concentrations averaged 12.1 µmol(+) L^-1 in bulk precipitation and 83.1 µmol(+) L^-1 in throughfall. There were no significant trends in the sum of base cations (p > 0.05). It is concluded that the reported reduction in S emissions over the study period has resulted in a significant reduction in the acidity and SO₄ ^2- concentration of bulk precipitation, and this reduction has has been reflected in throughfall concentrations. The greatest reduction has taken place in the southern part of the country.     

Chemical composition of throughfall and stemflow from citrus canopies 1

The main objective of this study was to examine the chemical composition of incident rainfall, throughfall, and stemflow from canopies of ‘Marsh’ grapefruit, and ‘Hamlin’ and ‘Temple’ orange trees. The concentrations of ammonium (NH₄) and nitrate (NO₃) were lower in the throughfall under the canopy or along the dripline as compared to those in the incident rainfall. This reduction is due to absorption of those nitrogen (N) forms by the tree foliage, thus, provides an evidence of contribution of (N) through wet deposition to N requirement of the trees. In contrast, concentrations of potassium (K), calcium (Ca), magnesium (Mg), and chloride (Cl) were greater in the throughfall or along the dripline compared to those in the incident rainfall. This is due to possible leaching of those elements from the foliage by the rainwater. Stemflow and throughfall also had greater pH and electrical conductivity (only in two out of three citrus varieties) as compared to the incident rainfall. Good correlation were found between concentrations of either K, Mg, or Ca, and Cl, phosphorus (P), or sulfur (S) in the incident rainfall for two storm events.     

Transport of metal cations through a nutrient-poor forest ecosystem

Metal cations were analyzed in bulk precipitation, soil water, and stream flow in a southeastern U.S. lower Coastal Plain pine flatwoods for 6 yr. Extractable ions in mineral soil and total amounts in herbaceous vegetation were also determined. Concentrations for all ions were higher in soil water than in bulk precipitation, but especially Na⁺ and Mg⁺⁺. There were smaller concentration differences between soil water and stream flow, except for three-fold higher Ca⁺⁺ in stream flow. Base saturation in the mineral soil was less than 10%, with Al dominating cation exchange sites. Of all cations, only K showed a significant relationship between exchangeable amounts in the soil and total amounts in herb layer vegetation. Soils in the watershed-ecosystem are experiencing minimal mineral weathering, although this can be spatially quite variable. We conclude that the chemistry of such soils is susceptible to change over several forest harvest rotations and continued acid deposition.

     

THE USE OF BULK COLLECTORS IN MONITORING WET DEPOSITION AT HIGH-ALTITUDE SITES IN WINTER

Concentrations of dissolved ions from samples collected by wet/dry collectors were compared to those collected by bulk collectors at Halfmoon Creek and Ned Wilson Lake in western Colorado to determine if bulk collectors can be used to monitor wet deposition chemistry in remote, high-altitude regions in winter. Hydrogen-ion concentration was significantly lower (p <0.05) in the bulk collectors. All other ion concentrations were significantly higher (p <0.05) in the bulk collectors except for ammonium (p >0.05) at Halfmoon Creek. Wet deposition concentrations were predicated from bulk deposition concentrations through linear regression analysis. Results indicate that anions (chloride, nitrate and sulfate) can be predicted with a high degree of confidence. Lack of significant differences between seasonal (winter and summer) ratios of bulk to wet deposition concentrations indicates that at sites where operation of a wet/dry collector during the winter is not practical, wet deposition concentrations can be predicted from bulk collector samples through regression analysis of wet and bulk deposition data collected during the summer.     

Deposition gradients and foliar and soil leachate concentrations of air pollutants in Scots pine stands of S.-E. Finland and the Karelian Isthmus,N.-W. Russia

Bulk precipitation and throughfall analyses in 50–100-year-old Scots pine stands revealed decreasing sulphur, nitrogen, calcium and magnesium deposition gradients, which extend from the St. Petersburg-Leningrad region and N.-E. Estonia to S.-E. Finland. The Ca and Mg deposition alleviate the acidifying effect of sulphur and nitrogen. The Scots pine canopies acted as a sink for ammonium and nitrate, while the canopy interactions increased sulphur, calcium and magnesium content in throughfall. Foliar S, N and Ca concentrations correlated positively with the corresponding deposition loads. In contrast, low foliar magnesium concentrations were detected in the vicinity of St. Petersburg. The results indicate that the sulphur and calcium deposition may have increased soil leachate S and Ca concentrations in the most polluted Scots pine stands.     

Effects of Precipitation and Air Temperature on Nitrogen Discharges from Rhode River Watersheds

We studied discharges of total-N, nitrate, ammonium, and total organic-N from seven contiguous small watersheds on the Atlantic Coastal Plain in Maryland for up to 25 yr. These watersheds have perched aquifers so all groundwater discharges as well as surface runoff were measured at V-notch weirs which included volume-integrating flow-proportional samplers. Interannual variations in annual and seasonal precipitation during this study spanned approximately the range of 160 yr weather records in the region. Annual total-N area yields from the overall watershed varied nine-fold, correlations of all N-parameter discharges with precipitation were highly significant, and power function regressions of precipitation vs N-discharge explained from 36 to 59% of the variance. Nitrogen fluxes from a cropland watershed were much higher and more variable with volume of precipitation, while fluxes from a forested watershed were much lower and were primarily composed of organic-N. Correlations of N-fluxes with precipitation were higher in the winter and spring. Annual and seasonal N-concentrations also often increased significantly with precipitation. Variations in seasonal air temperature sometimes explained significant amounts of variance in N-discharges, especially ammonium. A model composed of regressions was used to construct graphical and tabular summaries.     

The influence of basic aerosols on throughfall fluxes of sulfate,ammonium and nitrate in three oak stands along a distance gradient from a lime quarry

Three oak stands (Quercus petraea and Quercus robur) in the Weinviertel, Lower Austria, located along a distance gradient from a lime quarry, were studied to determine the effects of basic aerosols on the deposition of ammonium, nitrate and sulfate. Higher concentrations of limestone aerosols in the vicinity of the quarry are suggested by higher Ca²⁺ fluxes and pH in throughfall and precipitation. The ammonium/nitrate ratio in throughfall decreases with distance from the quarry, though monitoring of NH₃ and NO₂ concentrations in the air with passive samplers shows the opposite trend. These findings support the theory of discrimination against NH₃ in dry deposition due to the presence of Ca ²⁺ particles on leaf surfaces resulting from limestone aerosols. Higher sulfate deposition near the quarry is consistent with higher atmospheric SO₂ concentrations and co-deposition between calcium and sulfate.     

Transmission of Atmospherically Derived Trace Elements Through an Undeveloped, Forested Maryland Watershed

The transmission of atmospherically derived trace elements (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn) was evaluated in a small, undeveloped, forested watershed located in north-central Maryland. Atmospheric input was determined for wet-only and vegetative throughfall components. Annual throughfall fluxes were significantly enriched over incident precipitation for most elements, although some elements exhibited evidence of canopy release (Mn) or preferential uptake (As, Cr, and Se). Stream export was gauged based on systematic sampling under varied flow regimes. Particle loading appears to contribute significantly to watershed export (> 10%) for only As, Pb, and Fe, and then only during large precipitation/runoff events. The degree of watershed transmission for each trace element was evaluated based on a comparison of total, net atmospheric input (throughfall) to stream export over an annual hydrologic cycle. This comparison indicates that the atmospheric input of some elements (Al, Cd, Ni, Zn) is effectively transmitted through the watershed, but other elements (Pb, As, Se, Fe, Cr, Cu) appear to be strongly sequestered, in the respective orders noted. Results suggest that precipitation and subsequent soil pH are the primary factors that determine the mobility of sequestered trace element phases. To further resolve primary atmospheric and secondary weathering components, the geochemical model NETPATH was applied. Results indicate that minerals dissolved include chlorite, plagioclase feldspar, epidote, and potassium feldspar; phases formed were kaolinite, pyrite, and silica. The model also indicates that weathering processes contribute negligible amounts of trace elements to stream export, indicative of the unreactive orthoquartzite bedrock lithology underlying the watershed. Thus, the stream export of trace elements primarily reflects atmospheric deposition to the local watershed.     

PRECIPITATION OF CARBONATES IN SOILS IN CONTACT WITH WATERS UNDERSATURATED OR OVERSATURATED IN RESPECT TO CALCITE*

Under transient conditions, the precipitation of carbonates in a calcareous and a non-calcareous soil was influenced by calcium, magnesium and bicarbonate ions from soil sources. These sources were: the soil solution, the soil exchange complex and the dissolution of aluminosilicates. There was no significant difference between the amount of carbonates which precipitated in the two soils when in contact with the same water. It was found that for small portions of water in contact with the two soils, precipitation of carbonates took place both from under-saturated and the over-saturated waters. As the cumulative amounts of water in contact with the soils increased, the amount of ions contributed by the residual soil solutions and the exchange complexes decreased, and the amount of precipitating carbonates decreased also. At very large cumulative amounts of water, the precipitation of carbonates in the soils was controlled by both the water and the ions released from the soils.