首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Twenty one pore water chemistry profiles were obtained for a range of inorganic solutes from the Chalk unsaturated zone in or adjacent to Black Wood, a 2.4 kM2 mature beech wood in southern England. The depth sampled was normally 10 m, but some boreholes were shallower and one was deeper (30 m). Towards the centre of the wood, average pore water concentrations were: Cl (17–25 mg l-1), SO4 (20–40 mg l-1) and NO3-N (5–10 mg 1-1). In small clearings within the wood, concentrations of Cl (12–20 mg l-1) and SO4 (27–36 mg 1-1) were somewhat lower but the average concentration of nitrate-N was higher (16 mg 1-1). Pore water chloride and nitrate concentrations under a small area of ash were lower than under the beech. There was a significant increase in the concentration of a number of solutes, especially Cl, Na, Mg and SO4, close to the exposed western edge of Black Wood. This ‘edge effect’ decreased exponentially with a half distance of about 9 m. The effect was less consistent at the more sheltered eastern edge. Average pore water concentrations of up to 310 mg 1-1 Cl and 312 mg 1-1 SO4 were found at the western edge. Paradoxically, close to the western edge pore water nitrate concentrations were often very low, frequently less than 1 mg 1-1 NO3-N. Using the parameters derived from a simple exponential model of the Black Wood data, calculations suggested that the edge effect would lead to significantly enhanced Cl and SO4 pore water concentrations in forests of a few hectares, a size typical of many of those currently being planted. The consistently lower moisture content of the Chalk close to the forest edges suggested that groundwater recharge may have been lower there.  相似文献   

2.
Sulphate sorption on to the surface of short‐range ordered minerals and precipitation of Al‐hydroxy sulphate contribute to the acid neutralizing capacity of soils. The correct measurement of total inorganic sulphate is thus essential in soils that are accumulating SO42– anions. We extracted SO42– by various solutions, namely 0.005 m Ca(NO3)2, 0.016 m KH2PO4, 0.5 m NH4F and 0.2 m acidic NH4‐oxalate (pH 3), from Vitric and Eutric Andosols exposed to prolonged deposition of acid and SO2 from an active volcano (Masaya, Nicaragua). We attributed sulphate extractable by KH2PO4 (20–3030 mg kg?1) to anion‐exchangeable SO42–, which was much smaller than NH4F‐ and oxalate‐extractable SO42– (400–9680 and 410–10 480 mg kg?1, respectively). Our results suggest the occurrence of a sparingly soluble Al‐hydroxy‐mineral phase extractable by both NH4F and oxalate. The formation of Al‐hydroxy minerals would result from the combination of enhanced weathering caused by strong acid loading and simultaneous occurrence of large SO42– concentrations in soil solution. Oxalate extracted slightly more inorganic SO42– than did NH4F, this additional amount of SO42– correlating strongly with oxalate‐extractable Si and Fe contents. Preferential occlusion of SO42– by short‐range ordered minerals, especially ferrihydrite, explains this behaviour. If we exclude the contribution of occluded sulphate then oxalate and NH4F mobilize similar amounts of SO42– and are believed to mobilize all of the inorganic SO42– pool.  相似文献   

3.
Rain and snow in Alberta are seldom acid. The S content of snow is so low that the snow pack gives a deposition of less than 1 kg S ha?1, even downwind from large SO2 emission sources. Rainfall contributes at the most 4 kg S ha?1 yearly near SO2 sources, and only about 1 kg S ha?1 in clean areas. However, rain intercepted by forest trees exposed to SO2 emission becomes acid (pH 3.5 to 4.5) and has a S content of 3 to 4 times greater than rain. Soils absorb large amounts of S from emissions (up to 50 kg S ha ?1 annually) but much of the S is found in non-sulphate form. Soils are slowly acidified by the SO2 at a rate estimated at 1 pH unit in 10 to 20 yr. Water surfaces will absorb SO2 emissions at a rate of about 4 to 15 kg S ha?1 annually. Particulates deposit 3 to 4 times as much S as is deposited by rainfall.  相似文献   

4.
Needles of Scots pine (Pinus sylvestris L.) from 25 and 40 sampling plots in southern and northern Finland, respectively, that had earlier been analysed for total sulphur concentration (St) were reanalysed for foliar sulphate sulphur (SO4–S) and total nitrogen (Nt). Organic sulphur content (So) was calculated as the difference between St and SO4–S. Current (c) and previous-year (c+1) needles were collected from southern Finland in December 1989 and c – c+2 needles from northern Finland in September-October 1990/September 1992. The results show that the St concentration and St/Nt ratio in Scots pine needles are good indices of dry deposition of SO2 in general, while SO4–S concentrations and SO4–S/So ratios can be used in areas with low N supply from the soil and/or low wet deposition of N. The normal St concentration in needles of Scots pines growing on a podzol with low N supply is considered to be 500–700 μg g-1 and that of SO4–S 100–200 μg g-1. An increase of 100 μg g-1 in needle St may be attributed to a rise of 1.4 μg m-3 in ambient SO2 concentration in areas with relatively low SO2 concentrations (>15 μg m-3). A critical level of 5 μg m-3 as an annual and growing season mean is proposed for forestry in northern Europe (north of 60°N).  相似文献   

5.
Atmospheric air pollution levels and long-term effects on the environment caused by simultaneous presence of SO2 and oil shale alkaline fly ash during the last five decades (since 1950) were investigated. The annual critical value of SO2 for forest (20 µg m?3) was surpassed in 1% (～35 km2) of the study area where the load was 30–40 µg m?3. No effect of long-term SO2 concentrations of up to 10–11 µg m?3 (0.5-h max up to 270 µg m?3) and simultaneous fly ash loads of up to 95 µg m?3 (1000 µg m?3) on the growth and needle longevity of Pinus sylvestris was established. The yearly deposition (average load up to 20–100 kg S ha?1) was alkaline rather than acidic due to an elevated base cation deposition in 1960–1989. Since 1990, the proportion of SO2 in the balance of components increased: about 70–85% of the total area was affected while the ratio of annual average concentrations of SO2 to fly ash was over 1. The limit values of fly ash for Sphagnum mosses and conifers in the presence of SO2 are recommended.  相似文献   

6.
Total S concentrations of Scots pine (Pinus sylvestris L.) needles studied in the Finnish subarctic (66–70°N, 24–30°E) in 1990/1992 ranged from 573 to 1153 μg g-1. Levels were found to be ≈ 900 μg g-1 (i.e. 1.3–1.8 times the ‘normal’ level of 500–700 μg g-1) in areas where the long-term ambient SO2 concentration was ≈ 2–5 μg m-3, particulate SO4 2- ≈ μg m-3 and total S deposition ≈ 0.5 g m-2. A statistically significant increase in needle total S concentrations was found towards the east, i.e. towards the smelters of the Kola Peninsula in Russia, which emit SO2. The increase in needle total S concentrations to over 900 μg g-1 close to the Russian border is thought to result mainly from exposure to high short-term SO2 concentrations. The results also suggest that wintertime S deposition may have an impact on the needle total S content. It is suggested that the UNECE long-term critical level of 15 μg SO2 m-3 for forestry in boreal and high mountain climates in Europe is too high for the pine forests in the extreme north, where the proportion of dry-deposited S may be 60–80%.  相似文献   

7.
Kang  H.  Freeman  C.  Lock  M.A. 《Water, air, and soil pollution》1998,105(1-2):107-116
Fluxes of methane and nitrous oxide from a wetland were compared to hydrochemistry (NO3 - and SO4 2-) and soil enzyme activities (β-glucosidase) in an attempt to predict gas fluxes using chemical and enzymatic activities in north Wales, UK. In a one-year survey, the enzyme activities ranged from 0.028 to 0.065 µmol g-1 min-1, while NO3 - and SO4 2- concentrations ranged between 0-0.78 and 5-200 mg L-1, respectively. Methane and nitrous oxide emissions varied between 0.32-240 and 0.28-5.48 mg m-1 da-1, respectively. The field survey was followed by laboratory-based manipulation experiments, from which pilot mathematical models were constructed, and related to the field data. The variation of methane emission was attributed to changes in SO4 2- concentration and temperature at the site. In contrast, NO3 - concentration, water table height, and β-glucosidase activity were major controlling factors for nitrous oxide emission. The models explained more than 80 % of the variation observed in the field study.  相似文献   

8.
Sulfate (SO4 2?), nitrate (NO3 ?) and ammonium (NH4 +) concentrations in precipitation as measured at NADP sites within the Ohio River Valley of the Midwestern USA between 1985 and 2002 are quantified and temporal trends attributed to changes/ variations in (i) the precipitation regime, (ii) emission patterns and (iii) air mass trajectories. The results indicate that mean SO4 2? concentrations in precipitation declined by 37–43% between 1985 and 2002, while NO3 ? concentrations decreased by 1–32%, and NH4 + concentrations exhibited declining concentrations at some sites and increasing concentrations at others. The change in SO4 2? concentrations is in broad agreement with estimated reductions in sulfur dioxide emissions. Changes in NO3 ? concentrations appear to be less closely related to variations in emissions of oxides of nitrogen and exhibit a stronger dependence on weekly precipitation volume. Up to one quarter of the variability in log-transformed weekly NO3 ? concentrations in precipitation is explicable by variations in precipitation volume. Trends in annual average log-transformed SO4 2? concentrations exhibit only a relatively small influence of variability in weekly precipitation amount but at each of the sites considered the variance explanation of annual average log-transformed SO4 2? by sampling year was increased by removing the influence of precipitation volume. Annual mean log-transformed ion concentrations detrended for precipitation volume (by week) and emission changes (by year) exhibit positive correlations at all sites, indicating that the residual variability of SO4 2?, NO3 ? and NH4 + may have a common source which is postulated to be linked to synoptic scale variability and air mass trajectories.  相似文献   

9.
A linear gradient field exposure system was modified from one originally described by Shinn et al. (1977) and used to expose field grown soybeans (Glycine max cv Hark) to a concentration gradient of a mixture of two gaseous pollutants: SO2 and 03. Since this technique does not use enclosures, study plants experienced near ambient fluctuations in environmental conditions, including wind, and hence were exposed to widely fluctuating pollutant concentrations. Plants in the gradient system were exposed to both pollutants for 57 h on 12 days during the pod-filling period (31 August–17 September). Mean concentrations during the 57 h of exposure at the ‘high’ end of the gradient were 0.16 and 0.06 µl l?1 (PPM) SO2 and O3, respectively, with 10 h at greater than 0.25 and 0.10 µl?1 SO2 and O3, respectively. Total doses for these plants were estimated to be 9.0 and 3.5 µl?1 · h SO2 and O3, respectively. Comparison with plants exposed to ambient air indicated that exposure to SO2 and O3 reduced total yield per plant and dry mass per bean by as much as 36 and 15 %, respectively. Since concurrent exposure to a much higher dosage of SO2 alone (20.2 µl l?1 · h) was observed in a separate experiment to have no significant effect on yield, 03, although present at moderately low levels, was probably responsible (alone or synergistically with SO2) for the greatest reduction in seed size and yield.  相似文献   

10.
It is mainly SO2 that bring about acid rain in China. Changchun City, which is located in Northeast China, is a typical city that is polluted by SO2 from coal combustion in winter. In winter, the daily mean concentration of atmospheric SO2 is about 0.10mg/m3 and about 5 times as high as in summer, and the daily highest concentration usually appears in daybreak and nightfall. The monitored lowest pH value of rainwater was 4.8 in spring and the range of pH value of rain/snow was 5.2–6.0 in winter, 4.8–5.8 in spring, 5.4–6.4 in summer, 5.6–6.4 in autumn, and the annual mean pH value of rainfalls was 5.8 (1999–2000). Because the alkaline aerosol from soil, meteorological conditions etc., is unfavorable to acid rain formation, even though high SO2 emission intensity existed in winter, the acid rain did not appear obviously. The aerosol character, climate conditions in Northeast China are important factors for the acid rain formation, although SO2 emission is the original cause.  相似文献   

11.
The effect of cadmium(II) on the transformation of ferrihydrite[with Cd(II):Fe(III) ratios ranging from 0 to 5 mole %] in neutral and alkaline media (pH 7-11), combined with the effects of electrolyte type (NO3 -, Cl-, and SO4 -2), was investigated at 20 °C over a period of 1 yr. The presence of Cd(II) strongly retards the conversion of ferrihydrite into hematite and/or goethite at pH 7–10, with decreases in the rate of transformation dependent on the amountof Cd(II). At a Cd(II):Fe(III) mole ratio of 1%, the transformation rate is NO3 - > Cl- > SO4 -2, which correlates with the relative affinitiesof the anions for the ferrihydrite surface. The presence of Cd(II) promotes hematite formation at pH 9 and 10, whereas atpH 11 goethite is almost the sole product. With increasinginitial Cd(II) concentrations, increasing incorporationof Cd(II) into the products is observed. For 5 mole %Cd(II), ～ 2.5 mole % of Cd(II) is included in thetransformation products, principally hematite, while at pH 11, with 1 mole % Cd(II), all of the Cd(II) incorporates into thegoethite lattice. Transmission electron micrographs show that the presence of Cd(II) leads to a reduction in size and promotesthe twinning of goethite crystals, and can result in ellipsoidal-shaped hematite crystals. Leachability of Cd(II) fromfresh and aged coprecipitated Cd(II)-ferrihyrdite is dependent onthe extent of transformation of the ferrihydrite, with 70–90% of the Cd(II) leachable from ferrihydrite, while goethite is ableto incorporate and remove more Cd(II) than hematite.  相似文献   

12.
Woo  J.-H.  Baek  J. M.  Kim  J.-W.  Carmichael  G. R.  Thongboonchoo  N.  Kim  S. T.  An  J. H. 《Water, air, and soil pollution》2003,148(1-4):259-278
Emissions in East Asia for 1993 by administrative units and source types are estimated to support regional emission assessments and transport modeling studies. Total emission of SOx, NOx, soil NOx, N2O, and NH3 are 24 150, 12 610, 1963, 908, and 8263 kton yr-1, respectively.China's emission contribution is the highest for every species.The area sources are the most significant source type for SOx and NOx, but the fraction due to mobile source is highest for NOx. Major LPSs are located from the middle to the east part of China, south and middle-west part of South Korea, and the east part of Japan. The area sources of SOx show a pattern similar to population density, whereas NH3 shows a strong landuse dependency. Detail emissions analysis reveals higher SOx emission `cores' within each province. The estimated emissions are used to estimate sulfur deposition in the regions. The seasonal average sulfur distribution amounts are estimated from the ATMOS2 chemical transport model. The results showed anti-correlation with temperature for sulfur (SO2 + SO4 -2) concentrations and a positive correlation with rainfall for deposition.  相似文献   

13.
Methane (CH4) emission from flooded rice fields was measured hourly over 24 h for rice (Oryza sativa L.) seasons in 2008 and 2009. The objectives of this study were to identify typical diel variation in CH4 emission and to estimate the best time of day for optimum extrapolation of daily CH4 emission. Our results showed distinct diel variation in CH4 emission, which exhibited a maximum at 14:00–15:00 and a minimum at midnight. About 5.2–5.6% of total CH4 emitted per day (110–160 mg CH4 m?2 d?1) was released at 14:00–15:00. The diel pattern of CH4 emission resembled that of air temperature (Ta). The Ta coupled with solar radiation could cause a difference in partial pressure of CH4 (DPPC) through the gas conduit of the plant. The best extrapolation of daily CH4 emission was achieved with data observed at 10:00–11:00. We concluded that DPPC-induced CH4 emission is an important mechanism causing diel variation.  相似文献   

14.
 The effects of salt type and its concentration on nitrification, N mineralization and N2O emission were examined under two levels of moisture content in Yellow soil and Andosol samples as simulated to agriculture under arid/semi-arid conditions and under heavy application of fertilizer in a glass-house, respectively. The salt mixtures were composed of chlorides (NaCl and NH4Cl) or sulphates [Na2SO4 and (NH4)2SO4] and were added at various concentrations (0, 0.1, 0.2, 0.4 and 0.6 M as in the soil solution). These salts were added to non-saline Yellow soil at different moisture contents (45 or 40 and 65% of maximum water-holding capacity; WHC) and their effects on the changes in mineral N (NH4 +-N and NO3 –-N) concentration as well as N2O emission were examined periodically during laboratory incubation. We also measured urease activities to know the effect of salts on N mineralization. Furthermore, Ca(NO3)2 solution was added at various concentrations (0, 0.1, 0.3, 0.5 and 0.8 M as in the soil solution) to a non-saline Andosol taken from the subsurface layer in a glass-house and incubated at different moisture contents (50% and 70% of WHC) to examine their effects on changes in mineral N. Nitrification was inhibited by high, but remained unaffected by low, salt concentrations. These phenomena were shown in both the model experiments. It was considered that the salinity level for inhibition of nitrification was an electric conductivity (1 : 5) of 1 dS m–1. This level was independent of the type of salts or soil, and was not affected by soil moisture content. The critical level of salts for urease activities was about 2 dS m–1. The emission rate of N2O was maximum at the beginning of the incubation period and stabilized at a low level after an initial peak. There was no significant difference in N2O emission among the treatments at different salt concentrations, while higher moisture level enhanced N2O emission remarkably. Received: 29 July 1998  相似文献   

15.
Variations in sulphate (SO4 2-) concentration of porewater and net SO4 2- mobilization were related to differences in water level fluctuations during wet and dry summers in two conifer swamps located in catchments which differed in till depth and seasonality of groundwater flow. Sulphate depletion at the surface and in 20 cm porewater coincided with anoxia and occurred mainly during the summer when water levels were near the peat surface and water flow rates were low in both catchments. There was an inverse relationship between net SO4 2- mobilization and water level elevation relative to the peat surface, explaining variation in SO4 2- dynamics between the swamps during summer drought periods. Aeration of peat to 40 cm and a large net SO4 2- mobilization (10–70 mg SO4 2- m-2 d-1) occurred during a dry summer in which the water level dropped to 60 cm below the surface in the swamp receiving ephemeral groundwater inputs from shallow tills within the catchment. This resulted in high SO4 2- concentrations in the surface water and porewater (30–50 mg L-1), and elevated SO4 2- concentrations remained through the fall and winter. In contrast, within the swamp located in the catchment with greater till depth (> 1 m), continuous groundwater inputs maintained surface saturation during the dry summer, and SO4 2- mobilization and concentrations of SO4 2- in the pore water during the following fall did not increase. Susceptibility to large water table drawdown and mobilization of accumulated SO4 2- is influenced by the occurrence of ephemeral vs. continuous groundwater inputs to valley swamps during dry summer periods in the Canadian Shield landscape. This study reveals that extrapolation of results of SO4 2- cycling from one wetland to another requires knowledge of the hydrogeology of the catchment in which the wetlands are located.  相似文献   

16.
The mineralization of nitrogen from soil organic matter is important when one tries to optimize nitrogen fertilization and assess risks of N losses to the environment, but its measurement is laborious and expensive. We have explored the possibilities for monitoring N mineralization directly using time domain reflectometry (TDR). Net N and S mineralization were monitored over a 101‐day period in two layers (0–30 and 30–60 cm) of a loamy sand soil during aerobic incubation in a laboratory experiment. At the same time electrical conductivity of the bulk soil, σa, was measured by TDR. A series of calibration measurements with different amounts of KNO3 at different soil moisture contents was made with the topsoil to calculate the electrical conductivity, σw, of the soil solution from σa and θ. The actual σw was determined from the conductivity of 1:2 soil:water extracts (σ1:2) with a mass balance approach using measured NO3– concentrations, after correction for ions present prior to the addition of KNO3. The average N mineralization rate in the topsoil was small (0.12 mg N kg?1 day?1), and, as expected, very small in the subsoil (0.023 mg N kg?1 day?1). In the top layer NO3– concentrations calculated from σa determined by TDR slightly underestimated measured concentrations in the first 4 weeks, and in the second half of the incubation there was a significant overestimation of measured NO3–. Using the sum of both measured NO3– and SO42– reduced the overestimation. In the subsoil calculated NO3– concentrations strongly and consistently overestimated measured concentrations, although both followed the same trend. As S mineralization in the subsoil was very small, and initial SO42– concentrations were largely taken into account in the calibration relations, SO42– concentrations could not explain the overestimation. The very small NO3– and SO42– concentrations in the B layer, at the lower limit of the concentrations used in the calibrations, are a possible explanation for the discrepancies. A separate calibration for the subsoil could also be required to improve estimates of NO3– concentrations.  相似文献   

17.
The investigation of SO2, NO2, soot and benzo(a)pyrene (BP) has been performed at the background station on the eastern coast of the Baltic Sea since 1980. A significant decreasing trend has been observed for SO2 and NO2, while soot and BP concentrations were changing insignificantly. The decreasing SO2 and NO2 high concentrations (>10µg·m?3) have been determined in the air masses coming from the Western and Central Europe to Lithuania since 1900. The concentration of SO2 in a range of 0–5µg·m?3 and the concentration of NO2 in a range of 0–10µg·m?3 are characteric of the background atmospheric air.  相似文献   

18.
  相似文献   

19.
In recent decades, SO4 2- concentrations have increased in groundwater and surface water of freshwater wetlands. For many minerotrophic peatlands, S originating from SO4 2--polluted groundwater and surface water is a more significant source of SO4 2- than the actual atmospheric deposition of S compounds. Lowered groundwater tables in wetlands, as a result of either natural or anthropogenic desiccation, may cause acidification because of concomitant geochemical oxidation processes. The impact of the enhanced availability of reduced S compounds, due to preceding SO4 2- pollution, on these processes was tested in a mesocosm experiment, using soil cores including vegetation from a mesotrophic wet meadow. The soils had been maintained in waterlogged condition for seven months, using two environmentally relevant SO4 2- concentrations (2 and 4 mmol L-1). The groundwater table was reduced in two successive steps: 10 cm below soil surface, and complete desiccation. Control pretreated soils did not show a decrease in soil pH during desiccation, due to adequate buffering by bicarbonate. However, both SO4 2--pretreated groups showed a significant drop in pH (from 6.5 to 4.5) caused by additional sulfide oxidation, leading to high SO4 2- concentrations (10 and 16 mmol L-1, respectively). Cation exchange and acidification-related solubilization processes induced the mobiliztation of base cations and potentially phytotoxic metals like Al. Nutrient concentrations in soil moisture were influenced strongly by SO4 2- pretreatment, showing distinct patterns for P, N and K. Therefore, S polluted groundwater and surface water may severely increase the sensitivity of wetlands to desiccation. The results are discussed in relation to wetland management.  相似文献   

20.
Soil-Nitrate Determination with the NO3-sensitive Electrode A NO3-sensitive ion electrode (Orion, No. 92–07) was tested to determine the nitrate concentration in soil extracts. Some analytical problems are to be respected: 2. During a 2–8 week period of measurement the electrode gradually lost its potential (Figure 2). Therefore it is necessary to replace the sensitive elements (ion-exchanger, nitrate concentration and membran of electrode) at a certain level (in this 165 mV with 0.22 ppm NO,-N-solution). 3. Additional problems are from the heterogenity of thes oil(s = 0.10mg NO3-N/100g soil in this experiment). With 4 replications in sampling at given site or date, significant differences in the range of 20 kg NO,-N/ha have been obtained. Observing the before mentioned precautions the correlation between nitrate content 1. The optimal range for measurements can be calculated by application of the Peters-Nernst equation between 1 to 10 ppm NO3-N (Figure 1). This equation is influenced by the used electrode. Because this influence changed, it is necessary, to measure the standard solution before and after the series. determined by the nitrate electrode and conventional method (r = 0.92, Figure 3) was highly significant. The deviation of 0.28 ppm has no influence on the agronomy conclusions based on the nitrate determinations.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号