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1.
The protected area ??Bohemian Switzerland National Park?? with its characteristic sandstone landscape was influenced by the long-term air pollution and acidic deposition within the area known as Black Triangle (located where Germany, Poland, and the Czech Republic meet, is one of the Europe??s most polluted areas). The local Upper Cretaceous sandstone is subhorizontally stratified, fine- to coarse-grained, quartz dominated, with low content of clay minerals. One of the significant negative effects of the intensive acidic deposition on sandstone outcrops has been identified as chemical (salt) weathering, i.e., a process when the porous sandstone rock is except of chemical influence attacked also by force of crystallization of growing salts crystals. Anions NO 3 ? together with SO 4 2? and cation NH 4 + were the most abundant solutes in bulk precipitation samples. Current (2002 to 2009) bulk deposition fluxes of SO 4 2? determined at three sites directly in the National Park indicate decline from 23 to 16 kg?1 ha?1 year?1. Infiltration of bulk precipitation solutes into the sandstone mediates the weathering processes. Natural outflow of sandstone pore-water (sandstone percolates) can be sampled only during certain days of year when the sandstone becomes saturated with water and percolates drip out on small number of sites from roofs of overhangs. Under usual conditions percolation water evaporates at the sandstone surface producing salt efflorescences??the typical example is Prav?ická brána Arch locality. The average pH of the dripping sandstone percolates was 3.76. Concentration of SO 4 2? and Al in sandstone percolates reached up to 46 and 10 mg L?1. The concentration of Al in percolates has been 160-fold greater the one in the precipitation samples suggesting the sandstone as a source. The water O and H isotopic composition of percolates has been virtually identical to precipitation samples, indicating thus relatively short residence time of the solutions within the sandstone pore-spaces. Evaporation experiments with bulk precipitation and percolate samples proved possible origin of some Ca in bulk precipitation and the sandstone rock as the source of Al and possibly of K for the salt efflorescence identified on Rock Arch body.  相似文献   

2.
Experiments were carried.out in Chongging-a city seriously damaged by acid precipitation in southwest China — to explore chemical compositions of open bulk precipitation, throughfall and stemflow in a Masson pine (Pinus massoniana) forest. The results showed that annual mean pH values of and annual ion depositions in the three types of rain water were 4.47 and 50.6 g m?2, 3.82 and 69.7 g m?2, and 2.92 and 0.215 g m?2 respectively. pH values demonstrated an obvious seasonal variation; they were lower in winter than in the rest of the year. Ca2+ and NH inf4 sup+ together made up more than 80% of the total cation, while SO in4 sup2? alone contributed over 90% to the total anion. This high level of SO in4 sup2? in rain water in Chongqing, which outran those found in other cities in China, was closely related to the combustion of locally produced coal that contains 3 to 5% sulphur. Thus, acid precipitation in Chongqing is of a typical sulphuric-acid type.  相似文献   

3.
In the Vosges Mountains (NE of France), integrated plot-catchment studies have been carried out since 1985 in the Strengbach basin to study the influence of acid atmospheric inputs on surface water quality and element budgets. In this paper, available mid-term time series (1985–1991) have been considered to detect obvious trends, if any, in surface water chemistry and element budgets. Air quality data showed a slight decline for SO2, whereas NO2 slightly increased over the period, but these trends are not very significant. This is in agreement with increased N concentration (mainly as NH 4 + ) and with the stability of SO 4 2? in open field precipitation. Because of a significant decrease in rainfall amount over the period, only inputs of NH 4 + increased significantly whereas H+ and SO 4 2+ inputs declined. In spring and streamwaters, pH and dissolved Si concentration increased mainly as a result of a reduced flow. Na+, K+, Cl? and HCO-3~? concentrations remained stable whereas Ca2+, Mg2+ and SO 4 2+ concentrations declined significantly. Only NO 3 ? concentration increased significantly in springwaters. The catchment budgets revealed significant losses of base cations, Si and SO 4 2? . These losses decreased over the period. Nitrogen was retained in the ecosystem. However, a longer record is needed to determine whether or not changes in surface water chemistry have resulted from short-term flow reductions or long-term changes in input-output ion budgets. This is specially true with N because the decline in SO 4 2? output was accompanied by N accumulation.  相似文献   

4.
Solute fluxes to the ground in open plots and under the forest canopy of different species were investigated in a number of long-term ecosystem studies in West Germany. From the canopy flux balance, rates of interception deposition and canopy/deposition interactions were assessed. Chemically, both open precipitation and throughfall are dilute solutions of H2SO4 and HNO3 and their salts. For the sites investigated, mean pH in bulk precipitation ranged from 4.1 to 4.6, and in throughfall from 3.4 to 4.7. The increase in acidity after canopy passage at most sites indicates considerable interception deposition of strong acids to the forest stands, exceeding the rate of H+ buffering in the canopy. Evidence for buffering processes can be directly deduced from the fact that on sites with high soil alkalinity and high foliage base status, throughfall pH is usually higher than precipitation pH. Furthermore, the same idea can be concluded from changes in solution composition after canopy passage: the H+/SO inf4 sup2? ratio is decreasing at most sites, while alkali earth cations from exchange processes occur in throughfall (Ca2+/SO inf4 sup2? ratio increases). Solution composition and element flux data are presented for each of the sites, and the regional, orographical and site specific (species composition, ecosystem state) differentiations are discussed. A method for the assessment of total deposition and of canopy interactions such as H+-buffering and cation leaching is described, and results of calculations are shown. From these calculations it is concluded that forest ecosystems in Germany receive mean H+ loads of ca. 1 to 4 keq H+ · ha?1 · a?1 from atmospheric deposition. Acidity deposition rates seem to be related to a few key factors such as regional characteristics and ecosystem characteristics.  相似文献   

5.
The pH and amount of rainfall from over 60 selected stations throughout northern and lower Michigan was determined from September 1972 to December 1974. Precipitation pH was determined for each station by calibrated electrode meters. The seasonal weighted average and median pH from all stations in the study was 5.0 and 6.3, respectively. Daily readings from stations throughout Michigan indicate that pH is dependent on the amount of rainfall and that variations in it are often locally controlled. Collectively the pH values suggest carbonic acid control for most of the state. Annual median pH varied from a high of 8.45 at Dimondale, a station located 1.5 km from a concrete tile plant in central Michigan to 4.65 at Vassar, a small town located east of several industrial centers in the thumb region of the state. A comparison of annual nutrient loading for NO 3 ? , SO 4 = , Cl?,PO 4 ≡ , Ca++, Mg++ Na+ K+ and pH of rainwater from selected stations revealed that the eastern U.S. stations reporting pHs < 4.02 have similar loadings for NO3 but twice the SO4 input found for rural areas of Michigan.  相似文献   

6.
A simple method is presented and used to estimate the portions of SO inf4 sup2? and NO inf? sup3 that contribute to the strong acidity in weekly precipitation samples collected at three NADP sites in the eastern United States. The method assumes that, in general, the difference between SO inf4 sup2? and NH inf+ sup4 represents acidic sulfate and the difference between NO inf? sup3 and soil-derived materials (the sum of Ca2+, Mg2+, and K+) represents acidic nitrate. Acidic sulfate and nitrate are considered to be the predominant source of H+ (determined from laboratory pH) in the weekly precipitation samples. Most of the acidity for all three sites was attributed to acidic sulfate. The highest fraction of acidic SO inf4 sup2? to H+ wet deposition values was for the east-central Tennessee site (0.95) and the northeastern Illinois site (0.90), and the lowest fraction occurred at the central Pennsylvania site (0.75). The Tennessee site had the greatest acidic fraction of sulfate (0.84) and the Pennsylvania site had the greatest acidic fraction of nitrate (0.59).  相似文献   

7.
More than 1400 precipitation samples were collected weekly from 5 sites in Nova Scotia between 1978 and 1987. High concentrations of H+, non-marine SO inf4 sup= (*SO4) and NO inf3 sup- were observed in 1978 and 1986. In 1983, concentrations of all three parameters were the lowest in the data record. Fluctuations in emissions for SO2 are insufficient to account for the variability observed in concentration and deposition values. Mean annual concentrations in 1983 were 13, 16, and 6 ueq L-1 for H+, *SO4, and NO inf3 sup- , respectively. In 1986 the values were 35, 28, and 13 ueq L-1. Concentrations in 1978 were 31, 38, and 16 ueq L-1. Average pH of precipitation was 4.61 during the 10 yr study. The two most acidic years were 1979 (4.47) and 1986 (4.46). In 1983, the average pH was 4.89. The ratio (equivalents) of NO inf3 sup- to *SO4 was 0.41, so most acidity in the precipitation results from H2SO4 However, multiple regression analysis revealed that H+ is more sensitive to changes in NO3-concentrations than *SO4. Ratios of summer (JJA) vs winter (JFM) average concentrations were examined. During summer months, *SO4 and H+ were 1.8 times winter values. Summer to winter ratios for NO inf3 sup- and NH inf4 sup+ were 1.4 and 2.5, respectively.  相似文献   

8.
A study on pH and chemical composition of precipitation was carried out in two Italian sites, one urban (site 1) and one rural (site 2), located approximately 30 km far from Bologna, during a 3-year period. No significative site variation was found. In both locations, bulk deposition pH ranged from slightly acid to slightly alkaline, despite the volume weighted mean concentration of acidic species, NO 3 ? and SO 4 2? (67.4 and 118.4 μeq l?1 in site 1 and 88.7 and 103.8 μeq l?1 in site 2), that were similar to those of typical acidic rainfall region. This might be ascribed to the neutralization reaction of the Ca2+, attributed to the calcareous soil and the frequent dusty air mass intrusion from the Sahara. The pair correlation matrix and the analysis of the main components suggested also ammonium and other crustal elements as neutralization agents. The depositional rate of SO 4 2? and NO 3 ? , chemical elements of agricultural interest, amounted to 38 and 28 and 32 and 35 kg ha?1 for site 1 and site 2, respectively. These supplies of nutrient were not negligible and had to be considered on cultivated lands. NH 4 + deposition rate on site 2 was 7 kg ha?1, 23% over site 1, probably due to nitrogen fertilization in the fields around the monitoring station. In site 1, SO 4 2? presented a seasonal trend, indicating that its principal source was the residential heating. Results emphasized that the entity of the bulk deposition acidification is linked not only to the ions local emission sources (fossil fuel combustions, heating, and fertilizers) but also to the surrounding territory and the prevalent wind that transports through kilometers air masses which may contain acidic and alkaline species.  相似文献   

9.
Atmospheric deposition and surface water chemistry have been monitored intensively at 5 geologically “sensitive” sites in southeastern Canada. The sites receive differing acid inputs that span the entire range found in Canada. Surface water data collected at 9 stations from 1981 to 1993 for SO 4 2? , NO 3 ? , Alkalinity, DOC, pH, Ca2+ and Mg2+ have been analyzed to detect monotonic trends. Similarities between the temporal patterns and trends for SO 4 2? in deposition and surface water suggest that they are strongly linked at our sites. Our 13-year datasets showed significant negative SO 4 2? trends at the 3 Ontario sites and a positive trend in Nova Scotia. A climatically-induced SO 4 2? increase in northwestern Ontario has been reversed. Mobilization and export of adsorbed SO 4 2? and/or reoxidized S from the basins of central Ontario sites is delaying their recovery. Two of our 9 stations (in Quebec and central Ontario) are continuing to acidify. The 2 Nova Scotia stations have the highest DOC levels and both exhibit a decreasing trend. Ionic compensation for declining SO 4 2? varies from station to station, sometimes involving an Alk increase, sometimes a base cation decrease, and sometimes more complex combinations. Additional factors (e.g. climatic variation) also influence variable trends, and data records longer than those presently available will be needed to unequivocally verify acidification recovery.  相似文献   

10.
Humus chemistry and respiration rate, ATP, ergosterol, and muramic acid concentration as measures of chemical properties, microbial activity, biomass, and indicators of fungal and bacterial biomass were studied in a long-term acid rain experiment in the far north of Finnish Lapland. The treatments used in this study were dry control, irrigated control (spring water, pH 6), and two levels of simulated acid rain (pH 4 and pH 3). Originally (1985–1988), simulated acid rain was prepared by adding both H2SO4 and HNO3 (1.9:1 by weight). In 1989 the treatments were modified as follows. In subarea 1 the treatments continued unchanged (H2SO4+HNO3 in rain to pH 4 and pH 3), but in subarea 2 only H2SO4 was applied. The plots were sampled in 1992. The acid application affected humus chemistry by lowering the pH, cation exchange capacity, and base saturation (due to a decrease in Ca and Mg) in the treatment with H2SO4+HNO3 to pH 4 (total proton load over 8 years 2.92 kmol ha-1), whereas the microbial variables were not affected at this proton load, and only the respiration rate decreased by 20% in the strongest simulated acid rain treatment (total proton load 14.9 kmol ha-1). The different ratios of H2SO4+HNO3 in subareas 1 and 2 did not affect the results.  相似文献   

11.
Daily measurements of the concentrations of major ions in ambient air and in precipitation at Kejimkujik National Park, Nova Scotia, Canada over the period May 1979 to December 1987 are used to estimate the wet, dry and total deposition to the watershed. Variations on three time-scales are apparent. The strongest variation, of up to two orders of magnitude occurs on a day to day basis resulting in a coefficient of variation in the range of 110 to 140%. Deposition is highly episodic with the highest 20% of the daily events accounting for 55 to 60% of the long-term deposition. The most systematic variation is the annual cycle observed for many of the species. The air concentration of SO2 has the most pronounced cycle with a winter maximum and a summer minimum. The SO inf4 sup= air concentrations show a smaller amplitude and are out-of-phase with SO2, showing a summer maximum. Air concentrations of HNO3 and particulate N0 inf3 sup- also have an out-of-phase annual cycle, with a summer maximum and summer minimum respectively. Wet deposition of SO inf4 sup= shows a broad maximum through the summer months, but for NO inf3 sup- no systematic cycle is evident. On an ion equivalent basis, NO inf3 sup- contributes as much as SO inf4 sup= to the acidity of winter precipitation, but only one-third as much in the summer months. Although 8.7 yr is too short a time-scale to establish long term variations with any certainty, there does appear to be an overall downward trend in S concentrations and deposition, but not for N. This is not inconsistent with the trends in the emissions of SO2 and NOX in the regions upwind of Nova Scotia. The fraction of the S input to the watershed as dry deposition is estimated to average 22% of the total.  相似文献   

12.
In this study, an iron?Czirconium binary oxide with a molar ratio of 4:1 was synthesized by a simple coprecipitation process for removal of phosphate from water. The effects of contact time, initial concentration of phosphate solution, temperature, pH of solution, and ionic strength on the efficiency of phosphate removal were investigated. The adsorption data fitted well to the Langmuir model with the maximum P adsorption capacity estimated of 24.9?mg P/g at pH?8.5 and 33.4?mg P/g at pH?5.5. The phosphate adsorption was pH dependent, decreasing with an increase in pH value. The presence of Cl?, SO 4 2? , and CO 3 2? had little adverse effect on phosphate removal. A desorbability of approximately 53?% was observed with 0.5?M NaOH, indicating a relatively strong bonding between the adsorbed PO 4 3? and the sorptive sites on the surface of the adsorbent. The phosphate uptake was mainly achieved through the replacement of surface hydroxyl groups by the phosphate species and formation of inner-sphere surface complexes at the water/oxide interface. Due to its relatively high adsorption capacity, high selectivity and low cost, this Fe?CZr binary oxide is a very promising candidate for the removal of phosphate ions from wastewater.  相似文献   

13.
The fluxes of N–NO 3 ? , N–NH 4 + , S–SO 4 2? , Na+, K+, Ca2+ and Mg2+ from bulk precipitation to throughfall, stemflow and soil water surface flows were studied during 1999–2003 in planted Norway spruce forest stands of different ages (11, 24, 91 and 116 years in 1999). Also, runoff from the corresponding Potok Dupniański Catchment in the Silesian Beskid Mts was studied. N deposition was above the critical load for coniferous trees. The interception increased with stand age as well as leaf area index and so did the leaching from the canopy of almost all the analysed elements, but especially S–SO 4 2? , H+ and K+. The nutrient fluxes varied with age of the spruce stands. Throughfall showed a high amount of S and of the strong acids (S–SO 4 2? and N–NO 3 ? ) deposited to the soil, especially in older spruce age classes. Decomposition of organic matter caused a rise in water acidity and an increase in the concentrations of all the analysed ions; the leaching of minerals, however, was low (under 1%). The horizontal soil water flow showed an increase in the amount of water and amount of ions and contributed to a further decrease of pH at the soil depth of 20 cm. Element concentrations and their amounts increased with water penetrating vertically and horizontally on the slopes. Considerable amounts of ions, especially S and alkaline cations, were carried beyond the reach of the root system and then left the catchment. In the long term, these mineral losses will adversely affect health and growth of the spruce stands, and the increased acidity with stand age will presumably have negative effects on the runoff water ecosystem.  相似文献   

14.
Natural mats of C. stellaris growing in the subarctic lichen woodlands of northern Québec were treated in a randomized complete block design with solutions of simulated rain at pH 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 5.6. These solutions were acidified by addition of mixtures of sulfuric and nitric acids to give both 2 : 1 and 6 : 1 μequivalent ratios of SO inf4 sup= : NO inf3 sup? . After two years of acidification there was no significant effect of either pH or SO inf4 sup= : NO inf3 sup? ratio on the growth of C. stellaris, but thallus discoloration was evident below pH 3.5. After three years of acidification marginally significant (p = 0.05) but erratic depression of growth occurred under the 6 : 1 but not the 2 : 1 acidification regime, especially at pH 4.5 or less. Acid precipitation therefore only very gradually impairs the growth of C. stellaris, and the deleterious effects of acidification may be partially offset by nitrogen enrichment when precipitation is relatively rich in nitrate compared to sulfate ions.  相似文献   

15.
Published information, both theoretical and experimental, on As chemical behavior in soils is reviewed. Because of many emission sources, As is ubiquitous. Thermodynamic calculations revealed that As(V) species (HAsO 4 2- >H2AsO 4 - at pH 7) are more abundant in soil solutions that are oxidized more than pe+pH>9. Arsenic is expected to be in As(III) form (HAsO 2 0 =H3AsO 3 0 >AsO 2 - =H2AsO 3 - at pH 7) in relatively anoxic soil solutions with pe+pH<7. Adsorption on soil colloids is an important As scavenging mechanism. The adsorption capacity and behavior of these colloids (clay, oxides or hydroxides surfaces of Al, Fe and Mn, calcium carbonates, and/or organic matter) are dependent on ever-changing factors, such as hydration, soil pH, specific adsorption, changes in cation coordination, isomorphous replacement, crystallinity, etc. Because of the altering tendencies of soil colloids properties, adsorption of As has become a complex, empirical, ambiguous, and often a self contradicting process in soils. In general, Fe oxides/hydroxides are the most commonly involved in the adsorption of As in both acidic and alkaline soils. The surfaces of Al oxides/hydroxides and clay may play a role in As adsorption, but only in acidic soils. The carbonate minerals are expected to adsorb As in calcareous soils. The role of Mn oxides and biogenic particles in the As adsorption in soils appears to be limited to acidic soils. Kinetically, As adsorption may reach over 90% completion in terms of hours. Precipitation of a solid phase is another mechanism of As removal from soil solutions. Thermodynamic calculations showed that in the acidic oxic and suboxic soils, Fe-arsenate (Fe3(AsO4)4)2) may control As solubility, whereas in the anoxic soils, sulfides of As(III) may control the concentrations of the dissolved As in soil solutions. In alkaline acidic oxic and suboxic soils, precipitation of both Fe- and Ca-arsenate may limit As concentrations in soil solutions. Field observations suggest that direct precipitation of discrete As solid phases may not occur, except in contaminated soils. Chemisorption of As oxyanions on soil colloid surfaces, especially those of Fe oxide/hydroxides and carbonates, is believed to a common mechanisms for As solid phase formation in soils. It is suggested that As oxyanions gradually concentrate on colloid surfaces to a level high enough to precipitate a discrete or mixed As solid phase. Arsenic volatilization is another As scavenging mechanism operating in soils. Many soil organisms are capable of converting arsenate and arsenite to several reduced forms, largely methylated arsines which are volatile. These organisms may generate different or similar biochemical products. Methylation and volatilization of As can be affected by several biotic (such as type of organisms, ability of organism for methylation, etc.) and abiotic factors (soil pH, temperature, redox conditions, methyl donor, presence of other ions, etc.) factors. Information on the rate of As biotransformations in soils is limited. In comparison to the biologically assisted volatilization, the chemical volatilization of As in soils is negligible.  相似文献   

16.
The reversibility of acidification is being investigated in a full scale catchment manipulation experiment at Lake Gårdsjön on the Swedish west coast using isotopes as environmental tracers. A 6300 m2 roof over the catchment enables researchers to control depositional variables. Stable S isotope values were determined in bulk deposition, throughfall, runoff, groundwater and soil-extracted water during one year prior to and two years of experimental control. Data collected prior to experimental control suggest that the inorganic SO 4 2? pool within the catchment has a homogeneousδ 34S value of about+5.5‰. Sprinkling of water spiked with small amounts of sea-water derived SO 4 2? started in April 1991. Theδ 34S value of this SO 4 2? is around+19.5‰. Since April 1991, the SO 4 2? concentration in runoff has decreased by some 30%, however, theδ 34S value have increased by only 0.5‰. This suggests mixing of sprinkling water S with a large reservoir of S in the catchment. Oxygen isotopes in SO 4 2? suggest that less than one third of the SO 4 2? in runoff is secondary SO 4 2? formed within the soil profile. This is, however, no evidence for net mineralization of S. The SO 4 2? in runoff in the roofed catchment is a mixture of SO 4 2? previously adsorbed in the soil, mineralized organic S and SO 4 2? from the sprinkler water. Calculations based on isotope data indicate that the turnover time of S within the catchment is on the order of decades. Since SO 4 2? facilitates base cation flow, the acidification reversal will take a much longer time than concentration decreases of SO 4 2? would suggest.  相似文献   

17.
Fog water and precipitation were collected and analyzed to study fog and precipitation chemistry. The research was carried out through one year from April 1997 to March 1998 at Mt. Rokko in Kobe. Higher fog occurrence and larger volume of fog water were observed in summer, corresponding to the trend of seasonal variation in precipitation amount. The annual mean pH value of fog water (3.80) was lower by ca. one pH unit than that of precipitation (4.74). The concentration of chemical species in fog water was ca. 7 times that in precipitation. The highest anion and cation concentrations were SO4 2? and NH4 + in fog water and Cl? and Na+ in precipitation, although the Cl?/Na+ equivalent ratio in both fog water and precipitation was almost the same value as that in sea water. It is considered that in the longest fog event, NH4 + and nss-SO4 2? in fog water mainly scavenged as (NH4)2SO4, mainly derived from (NH4)2SO4 (aerosol) in the atmosphere, NH3 was scavenged at the growing stage, and SO2 was also scavenged after the mature stage. NO3 ? in this fog event was mainly absorbed as HNO3.  相似文献   

18.
Precipitation samples in Alberta were collected and analyzed monthly from six Alberta Environment stations. Samples were collected with Sangamo samplers and analyzed for the major ions, pH and acidity. The data were tabulated and analyzed for spatial distribution, seasonal variation, temporal trends, ionic character and wet sulphate deposition. The major ionic species in Alberta precipitation are Ca2+, SO inf4 sup2? , NH inf4 sup+ and N0 inf3 sup? . The spatial distribution shows a slight decrease in pH from southern Alberta (pH 6.0) to northern Alberta (pH 5.4). The seasonal variation shows higher hydrogen ion content in the summer months (pH 5.4 in summer and pH 5.8 in winter). Temporal trends are not apparent over the five year period investigated. The five year average wet sulphate deposition rate in Alberta is 9.1 kg ha?1 yr?1.  相似文献   

19.
We evaluated the differences in the use of a quartz filter and a polytetrafluoroethylene (PTFE) filter as a first (F0)-stage filter in a four-stage filter-pack method. A four-stage filter-pack method can completely collect sulfur species (SO2 and SO 4 2? ), nitrate species (HNO3 and NO 3 ? ), and ammonium species (NH3 and NH 4 + ) with little or no leakage irrespectively of the first-stage filter used. On the other hand, a seasonal variation was observed in the efficiency of collection between the quartz filter and the PTFE filter depending on the material to be collected. There was no seasonal variation in the efficiency of collection in sulfur species; in contrast, a clear seasonal variation was observed for the nitrate and ammonium species. As for NO 3 ? , the PTFE filter was more vulnerable than the quartz filter at air temperatures below 21°C, while the quartz filter was more vulnerable than the PTFE filter at air temperatures exceeding 21°C. A similar vulnerability for air temperature was observed for NH 4 + , although the threshold air temperature was 23°C for NH 4 + . Consequently, the evaporation loss of NO 3 ? would be mainly attributable to the volatilization of NH4NO3, although it is also partially due to the volatilization of NH4Cl.  相似文献   

20.
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.  相似文献   

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