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1.
High-elevation red spruce-Fraser fir forests in the Southern Appalachian mountains: 1) receive among the highest rates of atmospheric deposition measured in North America, 2) contain old-growth forests, 3) have shown declines in forest health, 4) have sustained high insect-caused fir mortality, and 5) contain poorly buffered soils and stream systems. High rates of nitrogen and sulphur deposition (1900 and 2200 Eq·ha–1·yr–1, respectively) are dominated by dry and cloud deposition processes. Large leaching fluxes of nitrate-nitrogen (100–1400 Eq·ha–1·yr–1) occur within the soil profile. We have expanded the study to the watershed scale with monitoring of: precipitation, throughfall, stream hydrology, and stream chemistry. Two streamlets drain the 17.4 ha Noland Divide Watershed (1676–1920m) located in the Great Smoky Mountains National Park. A network of 50 20x20 m plots is being used to assess stand structure, biomass, and soil nutrient pools. Nitrate is the predominant anion in the streamlets (weighted concentrations: 47 and 54 eq·L–1 NO3 –; 31 and 43 eq·L–1 SO4 2–). Watershed nitrate export is extremely high (1000 Eq·ha–1 yr–1), facilitating significant base cation exports. Stream acid neutralizing capacity values are extremely low (–10 to 20 eq·L–1) and episodic acidifications (pH declines of a full unit in days or weeks time) occur. Annual streamwater sulfate export is on the order of 770 Eq·ha–1yr–1 or about one-third of total annual inputs, indicating there is net watershed sulfate retention. The system is highly nitrogen saturated (Stage 2, Stoddard, 1994) and this condition promotes both chronic and episodic stream acidification.  相似文献   

2.
Sulphate concentrations and 34S ratios were monitored in bulk precipitation, spruce throughfall, and soil water (depth of 30 and 90 cm) at ervená jáma (CER) and Naetín (NAC), two severely polluted sites in the Czech Republic, between December 1992 and September 1994. Throughfall [SO4 2–], up to 80 mg L–1 in winter and as low as 7 mg L–1 in summer, was higher than [SO4 2–] in bulk precipitation (annual average 6 mg L–1). There was a distinct seasonaity in S isotope abundances, with lower 34SBULK in summer (+4 per mil CER, + 6 per mil NAC) and lower 34STF in winter (+3 per mil CER, +4 per mil NAC). Wintertime 34SBULK was around +8 per mil at CER and +10 per mil at NAC, summertime 34STF was close to +7 per mil at both sites. For only a 1- month period in spring, bulk precipitation S became isotopically lighter than throughfall S. Bulk precipitation data from CER were in good agreement with those from the nearby monitoring station Lesná (LES), typically differing by less than 10 mg L–1 and 2 per mil in [SO4 2–] and 34S, respectively. Suction lysimeters (soil depth of 30 and 90 cm) yielded higher sulphate concentrations and lower 34S ratios compared to both bulk and throughfall precipitation. Little seasonality was observed in [SO4 2–] at 30 cm (around 40 mg L–1); at 90 cm [SO4 2–] was higher in winter (70 mg L–1) than in summer (45 mg L–1). 34S at 90 cm was <+5 per=" mil=" in=" 1993=" and=" up=" to=" +7.5=" in=" 1994,=" lower=" in=" the=" first=" year=" and=" higher=" in=" the=" second=" year=" compared=" to=" the=" depth=" of=" 30=" cm.=" sulphur=" fluxes=" at=" cer=" and=" nac=" are=" characterized=" by=" distinct=" isotope=" compositions=" and=" can=" therefore=" be=" used=" to=" trace=" s=" pathways=" and=" transformations=" in=" the=" forest=">  相似文献   

3.
The degree to which floating aquatic plants concentrate Se in tissues was determined for four species grown in solutions containing various levels of Se. Results of this greenhouse study showed that all four plant species, Azolla caroliniana, Eichhornia crassipes, Salvinia rotundi folia, and Lemna minor absorbed Se quickly upon exposure to Se in water as concentrated as 2.5 g Se mL–1, and attained maximum tissue concentrations within 1 to 2 weeks. Azolla absorbed Se to the highest tissue concentration (about 1000 g Se g–1 dry matter) from the 2.5 g Se mL–1 solution, followed by Salvinia (700 g Se g–1), Lemna (500 g Se g–1),and Eichhornia (300 g Se g–1). Plant growth appeared unaffected by solution Se concentrations lower than about 1.25 g mL–1. These results indicate potential for rapid Se movement from water into aquatic food chains, and for use of aquatic plants for Se removal in wastewater treatment systems.  相似文献   

4.
The Lysina catchment in the Czech Republic was studied to investigate the biogeochemical response of Al to high loadings of acidic deposition. The catchment supports Norway spruce plantations and is underlain by granite and podzolic soil. Atmospheric deposition to the site was characterized by high H+ and SO4 2– fluxes in throughfall. The volume-weighted average concentration of total Al (Alt) was 28 mol L–1 in the O horizon soil solution. About 50% of Alt in the O horizon was in the form of potentially-toxic inorganic monomeric Al (Ali). In the E horizon, Alt increased to 71 mol L–1, and Ali comprised 80% of Alt. The concentration of Alt (120 mol L–1) and the fraction of Ali (85%) increased in the lower mineral soil due to increases in Ali and decreases in organic monomeric Al (Alo). Shallow ground water was less acidic and had lower Alt concentration (29 mol L–1). The volume-weighted average concentration of Alt was extremely high in stream water (60 mol L–1) with Ali accounting for about 60% of Alt. The major species of Ali in stream water were fluorocomplexes (Al-F) and aquo Al3+. Soil solutions in the root zone were undersaturated with respect to all Al-bearing mineral phases. However, stream water exhibited Ali concentrations close to solubility with jurbanite. Acidic waters and elevated Al concentrations reflected the limited supply of basic cations on the soil exchange complex and slow weathering, which was unable to neutralize atmospheric inputs of strong acids.  相似文献   

5.
The SO2 emissions from the Kola Peninsula in Arctic Russia (totalling around 600 Gg(SO2) yr–1 at the beginning of the 1990s) produce an atmospheric SO2 concentration gradient to the northernmost Europe. This gradient covers the range from >50 g m–3 in the vicinity of the sources to 1 g m–3 in Finnish Lapland. In the present study, the measured sulphur concentrations in Scots pine needles were compared with the estimated distribution of atmospheric SO2. The total sulphur concentrations in the needles ranged from 741 to 2017 mg kg–1. Strongly elevated concentrations (> 1200 mg kg–1) were found within 40 km from the smelters corresponding to an area where the annual mean atmospheric SO2 concentration exceeded 10 g m–3. The foliar sulphur concentrations (total, organic and inorganic) show a high correlation with the estimated mean SO2 concentration distribution in the air. Consequently the foliar sulphur concentrations reflected the atmospheric sulphur load well. The data presented here show that uptake via stomata is an important deposition pathway also in the arctic conditions with a short growing season.  相似文献   

6.
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7.
Computer assessments of the atmospheric chemistry and air quality of the past, present, and future rely in part on inventories of emissions constructed on appropriate spatial and temporal scales and with appropriate chemical species. Accurate inventories are also of substantial utility to field measurement scientists and the regulatory and policy communities. The production of global emissions inventories is the task of the Global Emissions Inventory Activity (GEIA) of the International Global Atmospheric Chemistry Project (IGAC). This paper presents a summary of recent emissions inventories from GEIA and other programs for reference year 1985, with special attention directed to emissions of the acid-related compounds CO2 (6.2 Pg C yr–1 anthropogenic), SOx (65 Tg S yr–1 anthropogenic and 15 Tg S yr–1 natural), NOx (21 Tg N yr–1 anthropogenic and 15–20 Tg N yr–1 natural), HCl (55 Tg Cl yr–1 total), and NH3 (45 Tg N yr–1 total). The global acid-equivalent flux of about 4.2 Teq H+yr–1 is about equally attributable to SOx and NOx emissions. For some of the acid-related species, historic inventories are available for a century or more; all show dramatic emissions increases over that period. IPCC scenario IS92a is used here as the basis for constructing global acid-related emissions estimates for selected years to 2100; among the results are that acid equivalent emissions are expected to more than double in the coming century.  相似文献   

8.
Summary A 2-year study (1983–1984 to 1984–1985) was conducted to estimate temporal and seasonal changes and the effects of fertiliser on some soil chemical, biochemical and microbiological characteristics. The soil used was a Typic Vitrandept under grazed pasture. Soil samples were taken regularly to a depth of 75 mm from paired unfertilised and fertilised (500 kg ha– 30% potassic superphosphate) plots. Except for organic C, fertiliser had little or no effect on the characteristics measured. Organic C averaged about 9.2% in unfertilised soil and was about 0.3% higher in the fertilised soil. The size of the microbial biomass fluctuated widely in the 1st year (3000 g C g–1 in February to 1300 g C g–1 in September) but there was less variation in the 2nd year (range 1900 g C g–1 to 2500 g C g–1 soil). CO2 production values (10- to 20-day estimates averaged 600 g of CO2-C g–1 soil) were generally higher in spring compared to the rest of the year. Water extractable C increased over winter and declined through spring in both years (range 50 g C g–1 soil to 150 g C g–1 soil). Mineral-N flush values were higher in summer (300 g N g–1 soil) and lower in winter months (200 g N g–1 soil). The pattern of variation of microbial N values was one of gradual accumulation followed by rapid decline. This rapid decline in values occurred in spring and autumn (range 130–220 g N g–1 soil). N mineralisation and bicarbonate-extractable N showed no clear trend; these values ranged from 100–200 and 122–190 g N g–1 soil, respectively. There was a significant correlation (0.1%) between N mineralisation and bicarbonate-extractable N in the late summer-autumn-early winter period (February–August) in both years but not in spring. These results and their relationships to climatic factors and rates of pasture production are discussed.  相似文献   

9.
As part of the Shenandoah National Park: Fish in Sensitive Habitats (SNP:FISH) project, the blacknose dace (Rhinichthys atratulus) was utilized as an indicator species to assess the susceptibility of the ichthyofaunal community of Shenandoah National Park (USA) to acidification. Water chemistry (ANC, conductivity, pH, and concentrations of Ca2+, Mg2+, Na+, K+, Cl–, NO3 –, SO4 2–, and SiO2) was sampled every three months over the course of 3 1/4 years which represents the probable maximum lifetime of R atratulus. Condition factors (K=[g/mm3]*106) were calculated for samples of fish (age class 2+ yr; n=370) from nine montane, second/third order streams representing a range of ANCs. A principle components regression was performed on factor scores from a principle components analysis of the water chemistry variables and fish condition factor. Two factors, one associated with stream water ANC and ion concentrations, and another associated with SO4 2– concentration, collectively explained 84% of the variance in condition factor. The influence of variables other than water chemistry upon R atratulus K is addressed. The results show that environmental chemistry is highly associated with the K of R atratulus.  相似文献   

10.
Summary The influence of the partial pressure of oxygen on denitrification and aerobic respiration was investigated at defined P02 values in a mull rendzina soil. The highest denitrification and respiration rates obtained in remoistened, glucose- and nitrate-amended soil were 43 1 N20 h–1g–1 soil and 130 1 O2 h–1g–1 soil, respectively. At -55 kPa matric water potential, corresponding to 40% water saturation, N20 was produced only below P02 40 hPa. The K m, for O2 was 3.0 x 10–6 M. Formation of N2O and consumption of O2 occurred simultaneously with half maximum rates at P02 6.7–13.3 hPa. Nitrite accumulated in soil below 40 hPa and increased with decreasing pO2. The upper threshold for N20 formation in amended soil was P02 33–40 hPa (39-47 M O2).  相似文献   

11.
Summary We studied the effects of the organophosphorus insecticide methidathion, at concentrations of 10, 50, 100, 200 and 300 g g-1 in an agricultural soil, on fungi, total bacterial populations, aerobic N2-fixing bacteria, denitrifying bacteria, nitrifying bacteria (phases I and II), and nitrogenase activity (acetylene reduction assay). The presence of 10–300 g g-1 of methidathion significantly increased fungal populations (colony-forming units). Denitrifying bacteria, aerobic N2-fixing bacteria and N2 fixation were significantly increased at concentrations of 50–300 g g-1. The total number of bacteria increased significantly at concentrations of 100–300 g g-1. Nitrifying bacteria decreased initially at concentrations of 300 g g-1, but recovered rapidly to levels similar to those in the control soil without the insecticide.  相似文献   

12.
Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl–, NO3 – and SO4 2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.  相似文献   

13.
A pot experiment was conducted in a greenhouse to establish the threshold level of Cd in a light soil planted with cereals. During three consecutive years barley, wheat, rye, and corn were grown in the soil treated with 2.5; 5; 25 g g–1 of Cd applied in sulphate form. The Cd concentration of 5 g g–1 (plus native Cd content of the soil) was considered as the maximum permissible Cd level in a soil for the soil-plant systems studied. Besides the estimation of total Cd concentrations, several forms of Cd in soils (exchangeable, carbonate, Fe-Mn oxides, organic, and residual) were determined by mean of sequential extraction to define the phytoavailable form of Cd in the soil. The Cd concentration in studied plants increased with the doses of this metal in soil but to different extents for various plant species and various plant parts. The highest Cd enrichment ratios (ER) were found for wheat and corn leaves (2 to 3), whereas, the lowest ERs were detected for corn and rye grains (0.05 to 0.2) grown at the treated soils. All samples of the control plants had ER below 1. A close relationship was found between Cd content of plants and the exchangeable form of Cd in soil, which indicates that this form of the element is readily available for plants. The proposed maximum permissible level of Cd (5 g g–1 of added metal plus native Cd content of soils) in light soils proved to be too high for cereal plants. The threshold concentration for light soil should not exceed 3 g g–1.  相似文献   

14.
Growth rate change in earthworms is considered to be a suitable endpoint when determining sublethal effects. In this study we evaluated growth and maturation in the vermicomposting earthworm speciesEudrilus eugeniae as marker of sublethal toxicity of copper and zinc. We also compared routes of uptake. Apart from exposing worms experimentally for 73 days to contaminated food, a series of contact filter paper tests was also performed to determine LD50 for copper and zinc. Both copper and zinc at sublethal concentrations affected growth and maturation in worms exposed to contaminated food. These worms had a copper content of 34.5 g g–1 after 73 days and a zinc content of 184.9 g g–1, showing a differential uptake. Copper was more toxic than zinc. Also in the contact test worms did take up more zinc than copper and the LD50 (48 h) for copper was 0.011 mg cm–2 and for zinc 0.066 mg cm–2, which translated to body burdens of 6 g g–1 for copper and 131 g g–1 for zinc. Indications were that a regulatory mechanism existed for both metals. Both metals were taken up through the body wall at a relatively fast rate. This study indicated that the skin was the major route of metal uptake. This study also showed a poor relation between the two types of tests for purposes of evaluating lethality of zinc and copper.  相似文献   

15.
The flow of new and native plant-derived C in the rhizosphere of an agricultural field during one growing season was tracked, the ratios in different soil C pools were quantified, and the residence times (s) were estimated. For this the natural differences in 13C abundances of: (1) C4 soil (with a history of C4 plant, Miscanthus sinensis, cultivation), (2) C3 soil (history of C3 plant cultivation), and (3) C4/3 soil (C4 soil, planted with a C3 plant, Triticum aestivum) were used. Total amounts and 13C values of total soil C, non-hydrolysable C, light fraction C, water-soluble C, microbial biomass C, and phospholipid fatty acids (PLFA) were determined. Using the 13C values of soil C in a mixing and a 1-box model enabled the quantification of relative contributions of C3 plant and C4 plant C to the total amount of the respective C pools in the C4/3 soil and their s. Compared to early spring (March), the percentage of C3 plant C increased in all pools in June and August, showing the addition of new C to the different soil C fractions. In August the contribution of new C to microbial biomass C and water-soluble C reached 64 and 89%, respectively. The s of these pools were 115 and 147 days. The 13C values of the dominant soil PLFA, 18:17c, cy19:0, 18:19c, 16:0, and 10Me16:0, showed wide ranges (–35.1 to –13.0) suggesting that the microbial community utilized different pools as C sources during the season. The 13C values of PLFA, therefore, enabled the analysis of the metabolically active populations. The majority of 13C values of PLFA from the C4/3 soil were closely related to those of PLFA from the C3 soil when T. aestivum biomass contributions to the soil were high in June and August. Specific populations reacted differently to changes in environmental conditions and supplies of C sources, which reflect the high functional diversity of soil microorganisms.  相似文献   

16.
During 1985–1989 particulate carbon concentrations were determined at suburban and rural sites in Lithuania. The main part of the continuous measurements was conducted at Preila background station (Curonian spit). Daily samples of airborne particulate matter were collected on glass fiber filters or by impactors and analysed for total carbon (TC), benzene extractable organic carbon (BEOC) and elemental carbon (EC) using combustion and optical techniques. Monthly median concentrations of total particulate carbon varied in the range 2–22 g/m3 during the period of measurements. For all the forms of particulate carbon the strong seasonal dependence was observed. The very regular seasonal cycle is characteristic for the ratio EC/TC: 0.10–0.15 and 0.30–0.35 for warm and cold periods respectively. Size distribution measurements shows that the main part of TC is in the sub-micron particle fraction — about 80–90 % in summer and even 92–98 % in winter. The concentrations of TC in size fraction <1.2>m have sharp winter peaks and summer minima. Very low concentrations and summer maxima for TC in the fraction >3.5 m have been observed. The concentrations of EC in precipitation varied from 0.02 to 0.7 mg/l and average wet deposition flux of EC was 5–7 and maximum 15–20 mg/m2 per month.  相似文献   

17.
Summary Physiological and symbiotic characteristics were identified in Rhizobium fredii isolated from subtropical-tropical soils. The generation times of R. fredii Taiwan isolated-SB 357 and -SB 682 were 1.7 and 2.5 h, respectively. These strains were associated with acid production in yeast-extract mannitol medium. They were able to use hexoses, pentose, sucrose, trehalose and raffinose. Strain SB 357 can resist a high concentration of kanamycin (100 g ml–1 and penicillin (400 g ml–1). It can tolerate up to 2.34% NaCl and 1031.3 mosmol kg–1 (23.4 bars). The growth rate of R. fredii SB 357 under the concentration of approximately 450 mosmol kg–1 (10.2 bars) was not affected by salinity, but responded to osmotic pressure. Both strains (SB 357 and SB 682) isolated from subtropical-tropical soils were able to form an effective N2-fixing symbiosis with the US soybean cv Clark lanceolate leaflet.  相似文献   

18.
Field studies using open-top chambers were conducted at USDA-BARC involving the growth of soybeans ('89 & '90), wheat ('91 & '92), and corn ('91), under increased concentrations of atmospheric CO2 and O3. Treatment responses were compared in all cases to plants grown in charcoal-filtered (CF) air (seasonal 7-h mean = 25±3 n mol O3 mol–1) having 350 or 500 mol CO2 mol–1. Elevated seasonal O3 levels for the soybean, wheat, and corn studies averaged 72.2±4, 62.7±2, and 70.2 n mol O3 mol–1, respectively. Results presented were obtained for plants grown in silt loam soil under well-watered conditions. Grain yield increases in response to elevated CO2 in the absence of O3 stress averaged 9.0, 12.0, and 1.0% for soybean, wheat, and corn; respectively. Reductions in grain yields in response to the elevated O3 treatments at 350 mol CO, mol–1 averaged 20.0, 29.0 and 13.0% for soybean, wheat, and corn, respectively. Reductions in grain yields in response to elevated O3 at 500 mol CO2 mol–1 averaged 20.0, 8.0, and 7.0% for soybean, wheat, and corn, respectively. Dry biomass and harvest index in wheat were significantly reduced by O3 stress at 350 mol mol 1 CO2 but not at 500 u mol mol–1 CO2. Seed weight 1000–1 for scybeans and wheat was significantly increased by CO2 enrichment and decreased by O3 stress. Seed weight 1000–1 in corn was increased by O3 stress suggesting that O3 affected pollination resulting in fewer kernels per ear.Scientific Article No. A7784, Contribution No. 9105, Maryland Agric. Exp. Sta., Univ. of MD, College Park, MD 20472  相似文献   

19.
Atmospheric deposition was almost entirely excluded from the forested headwater catchment G1 ROOF, by means of a 7000 m2 plastic roof that prevents rain and throughfall from reaching the ground. Under the roof an irrigation system was installed to simulate a natural precipitation regime. The intercepted throughfall was substituted by the same amount of clean pre-industrial throughfall. The experiment started in April 1991. During the four years of the treatment, 2960 mm (18 600 m3) of sprinkled solution was applied under the roof, which is about 15 times the mean water storage of the catchment. After four years of treatment major changes in runoff chemistry were observed. The exclusion of all non-marine sulphate (SO4 2–) input to the catchment (i.e. ca 75 % of total SO4 2– input excluded) resulted in significant decline of sulphate in runoff through all four years of treatment. During the fourth year, annual volume weighted SO4 2– concentration was 46 % lower than the two years prior to the treatment. Concentrations of inorganic aluminium Al3+ declined 52 % and Mg2+ declined 54 %. No change of H+ concentration was detected. As the treatment proceeds there seems to be a trend towards less negative acid neutralising capacity in runoff.  相似文献   

20.
Chemical Composition of Precipitation in Beijing Area, Northern China   总被引：1，自引：0，他引：1  
Variations of anions (SO4 2-, NO3 -,NO2 -, Cl- and F-),cations (K+,Na+, Ca2+, Mg2+ and +) and pH values in precipitation, througfall and stemflow samples collected overa four-year period (1995–1998) in Beijing (two sitesZhongguancun and Mangshan) are presented. The annualvolume-weighted range of pH values were 6.57–7.11 inprecipitation, 5.46–6.86 in thoughfall and 5.32–6.41 instemflow. The fominant anion was , while Ca+and NH4 + were the main cations in precipitation,throughfall and stemflow. Most of ion concentrations with precipitation, throughfall and stemflow volume showed negative correlation, except for some ones. Significant correlationvalues were also found between ions (SO4 2-,NO3 -, Cl-, F-, Ca2+,Mg2+ andNa+) in precipitation, throughfall and stemflow indicatedthe common sources of these ions such as coal combustion,automobile emission and fertilizers application. Compared toprecipitation, there was an increased ion concentration inthroughfall or in stemflow. Changes of ion concentrations werein Quercus liatungensis Koiz. and Pinus tabulaefornisCarr. throughfall (or stemflow) because of different crown andbark qualities of tree species.  相似文献   

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