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1.
The distribution and seasonal variations of petroleum residues in the Shatt al-Arab water column have been determined spectrofluorometrically. Their concentrations were found to vary between 1.7 to 35.4 μg L?1 Kuwait crude oil equivalents. The results suggested that petroleum hydrocarbons present in this river originated from diverse sources. Hydrocarbon amounts tend to be highest in winter (averaged 17.4 μg L?1) and lowest in summer (averaged 3.1 μg L?1).  相似文献   

2.
Composition and Speciation of Soil Solution collected in a Heavy Metal polluted calcareous Soil Close to a brass foundry, which had emitted heavy metal containing dusts for over 80 years, soil water was collected in the topsoil (18 cm) and in the subsoil (40 cm) of a severely polluted Calcic Fluvisol by means of polyethylen suction cups over a period of 2 years. The total metal content of the topsoil (extracted with 2M HNO3 at 100 °C for 2 hours) was 38 nmol g?1, 24 μmol g?1, and 25 μmol g?1 for Cd, Cu, and Zn, respectively. The mean heavy metal concentrations of the soil solution were 0.5 mol L?1, 300 nmol L?1, and 200 nmol L?1 in the topsoil and 0.6 nmol L?1, 90 nmol L?1, and 30 nmol L?1 in the subsoil for Cd, Cu, and Zn, respectively. Solubility calculations showed that the soil solutions were undersaturated with respect to heavy metal carbonates as well as to hydroxides. It seems that the heavy metal concentration is determined by sorption processes rather than by precipitation. The composition of the soil solution has been shown to be governed by the presence, of calcite, by the soil temperature and by the partial pressure of CO2 in the soil air. The pCO2 in the soil air (in both depths) has been estimated at 2 mbar during the winter term and at 20 mbar during the summer term. A corresponding increase of the concentration of macroelements (Ca, Mg, Na) as well as of total dissolved carbonate and of dissolved organic matter (DOC) has been measured in the summer half year. No significant seasonal variations of the heavy metal concentrations were detected and no correlations with concentrations of other components could be found.  相似文献   

3.
A loam from the Frilsham and one from the Wickham Series were incubated at 50 and 90 per cent of their water contents at saturation with 100 μg NH4NO3-Ng?1 soil in the presence and absence of C2H2 (0.5 per cent, v/v). Acetylene inhibited nitrification in both soils, but had no effect on mineralization of N. No denitrification (measured as the production of N2O in the presence of C2H2) occurred during incubation at 50 per cent saturation. At 90 per cent saturation, denitrification resulted in a loss of 28.4 and 36.7 μg Ng?1 after 48 h from the Frilsham and Wickham soils, respectively. The concurrent inhibition of nitrification had no effect on the extent of denitrification at this time. In the Wickham soil, NO3? was exhausted after 168 h incubation in the presence of C2H2 and denitrification was underestimated by 13 μg Ng?. The data suggested that concurrent inhibition of nitrification during measurement of denitrification using the C2H2 inhibition technique is most likely to affect the estimate of denitrification loss when NO3?supply is limited by the inhibition of nitrification.  相似文献   

4.
The nitrogenase activity (potential nitrogen fixation) of a mixed white clover-grass sward growing on a range of soils containing up to 216 μg g?1 Cd, 30 000μg g?1 Pb and 20 000 μg g?1 Zn was determined using the acetylene-reduction assay. The plants were incubated in situ using an intact soil-core technique. Little change in the rate of C2H2 reduction was observed during the daylight hours although a marked seasonal fluctuation was found, the maximum activity during the spring and declining to 20% of this by the autumn. Some reductions of nodule and plant size, and in nitrogenase activity, was observed in the most heavily contaminated sites. These effects were small; the plants and nodules otherwise appeared healthy. The potential for nitrogen fixation was equally high in all the sites at up to 80 g N ha?1 h?1 in the spring.  相似文献   

5.
The objective was to develop and adapt a versatile analytical method for the quantification of solvent extractable, saturated long‐chain fatty acids in aquatic and terrestrial environments. Fulvic (FA) and humic (HA) acids, dissolved organic matter (DOM) in water, as well as organic matter in whole soils (SOM) of different horizons were investigated. The proposed methodology comprised extraction by dichloromethane/acetone and derivatization with tetramethylammonium hydroxide (TMAH) followed by gas chromatography/mass spectrometry (GC/MS) and library searches. The C10:0 to C34:0 methyl esters of n‐alkyl fatty acids were used as external standards for calibration. The total concentrations of C14:0 to C28:0 n‐alkyl fatty acids were determined in DOM obtained by reverse‐osmosis of Suwannee river water (309.3 μg g—1), in freeze‐dried brown lake water (180.6 μg g—1), its DOM concentrate (93.0 μg g—1), humic acid (43.1 μg g—1), and fulvic acid (42.5 μg g—1). The concentrations of the methylated fatty acids (n‐C16:0 to n‐C28:0) were significantly (r2 = 0.9999) correlated with the proportions of marker signals (% total ion intensity (TII), m/z 256 to m/z 508) in the corresponding pyrolysis‐field ionization (FI) mass spectra. The concentrations of terrestrial C10:0 to C34:0 n‐alkyl fatty acids from four soil samples ranged from 0.02 μg g—1 to 11 μg g—1. The total concentrations of the extractable fatty acids were quantified from a Podzol Bh horizon (26.2 μg g—1), Phaeozem Ap unfertilized (48.1 μg g—1), Phaeozem Ap fertilized (57.7 μg g—1), and Gleysol Ap (66.7 μg g—1). Our results demonstrate that the method is well suited to investigate the role of long‐chain fatty acids in humic fractions, whole soils and their particle‐size fractions and can be serve for the differentiation of plant growth and soil management.  相似文献   

6.
The effect of 50, 100, 150, and 400 μg sodium pentachlorophenate (Na-PCP) per gram soil was studied in nonsterile soil incubated under aerobic and anaerobic conditions, and in sterilized soil inoculated withAzotobacter sp. isolated from the soil. N2 fixation was determined by acetylene reduction. Pentachlorophenate at a concentration of 50 μg g?1 had an inhibitory effect in nonsterile soil incubated aerobically while strong inhibition of dinitrogen fixation in nonsterile soil occurred in the presence of 100 μg g?1 and above. The EC50 values for the inhibition of nitrogenase activity in nonsterile soil incubated aerobically and anaerobically and in sterilized soil inoculated withAzotobacter sp. suspensions were 49.8±1.4 μg Na-PCP g?1, 186.8±2.8 μg Na-PCP g?1, and 660.8±29.3 μg Na-PCP g?1, respectively.  相似文献   

7.
Zinc as ZnSO4 was added to three soils at rates of 0, 10, 100 and 1000 μg Zn g?1 soil. The soils were uniformly treated with 100 μg Ng?1 as nh4cl, incubated at 30°C and NH4+-N and (NO3? + NO2?)-N determined weekly for 7 weeks. Nitrification in all three soils was totally inhibited by 1000 μg Zn g?1. At the 100 μg Zn g?1 rate, nitrification was significantly reduced in two of the three soils during some part of the incubation. This differential effect on nitrification at the 100 μg Zn g?1 rate was related to differences in soil properties. These results imply that, with respect to nitrification, care should-be taken not to apply Zn-containing materials indiscriminately to soils.  相似文献   

8.
Chestnut agro-industrial companies consume a high volume of water for washing and processing fruit, generating a large volume of wastewater. This work studied the biodegradation of chestnut processing wastewater through aerobic assays, varying substrate, and biomass concentrations. In general, this wastewater presents a good biodegradability, especially in experiments with relatively low chemical oxygen demand (COD) (0.4 and 0.6?g O2 L?1) allowing a COD removal of 85?C90?%. The best results were obtained in the reactor initially loaded with 2?g?L?1 of biomass and 0.4 or 0.6?g O2 L?1 of COD. These experiments also showed high COD removal rates: 4.25 and 3.88?g COD g?1 volatile suspended solids (VSS) h?1, respectively. The sedimentation rate, evaluated for different initial values of biomass (1, 2, and 3?g?L?1), always presented higher values in the experiments with 2 and 3?g?L?1 of biomass, regardless of the initial COD value used. After comparing different kinetic models (Monod, Contois, and Haldane), it was observed that the Haldane inhibition model satisfactorily describes the COD biodegradation. AQUASIM software allowed calculating the kinetic constant ranges: K s, 1.59?C6.99?g COD L?1; ?? max, 25?C40?g COD g?1 VSS day?1; and K i values, 0.07?C0.11. These kinetic constants corresponds to maximum rates (??*) between 1.48 and 4.25?g COD g?1 VSS day?1 for substrate concentrations (S*) from 0.38 to 0.88?g COD L?1.  相似文献   

9.
In Plastic Lake, Ontario, stocked rainbow trout (Salmo gairdneri) have failed to survive, one endemic fish species has become extinct and annual fish kills included up to five species, but especially pumpkinseeds (Lepomis gibbosus). The potential toxicity of Plastic Lake water was assessed by holding (hatchery) rainbow trout in the major inlet stream, the outlet, and in a portion of the outlet stream acidified to the pH of inlet No. 1. Stress on rainbow trout was assessed by measuring plasma and muscle concentrations of Na + Cl?, and K+, plus gill A1 concentration. Trout held in Plastic Lake inlet No. 1 showed a rapid loss of plasma Na+ from 138 to 85 meq.L?1and Cl? from 120 to 75 meq.L?1 within 24 hr. Gill A1 concentration increased from 20 to 105 μg.g?1 dry weight. Trout held in the outlet steam showed only slight loss of plasma Na+ and Cl? and no accumulation of Al on the gills. Trout held in the acidified outlet showed a significant loss of ions with plasma Na+ depressed from 140 to 115 meq.L?1 and plasma Cl? from 125 to 95 meq.L?1over 24 hr. Gill Al concentration increased from 18 to 30 μg.g?1 dry weight. The differences in stress response of rainbow trout held in the inlet and acidified outlet are likely due primarily to the difference in Al species concentrations in the two waters.  相似文献   

10.
Toxicity of heavy metals (Zn,Cu, Cd,Pb) to vascular plants   总被引：1，自引：0，他引：1  
The literature on heavy metal toxicity to vascular plants is reviewed. Special attention is given to forest plant species, especially trees, and effects at low metal concentrations, including growth, physiological, biochemical and cytological responses. Interactions between the metals in toxicity are considered and the role of mycorrhizal infection as well. Of the metals reviewed, Zn is the least toxic. Generally plant growth is affected at 1000 μg Zn L?1 or more in a nutrient solution, though 100 to 200 µg L?1 may give cytological disorders. At concentrations of 100 to 200 μg L?1, Cu and Cd disturb metabolic processes and growth, whereas the phytotoxicity of Pb generally is lower. Although a great variation between plant species, critical leaf tissue concentrations affecting growth in most species being 200 to 300 μg Zn g?1 dry weight, 15 to 20 μg Cu g?1 and 8–12 μg Cd g?1. With our present knowledge it is difficult to propose a limit for toxic concentrations of Zn, Cu, Cd and Pb in soils. Besides time of exposure, the degree of toxicity is influenced by biological availability of the metals and interactions with other metals in the soil, nutritional status, age and mycorrhizal infection of the plant.  相似文献   

11.
The effect of adding cobalt, as 60Co, to the food source of the earthworm Eisenia foetida was studied. Cobalt was retained with a half-life of 387 ± 43 (SD) days in the worm. After 172 days more cobalt was concentrated in the gut than the body wall. 60Co was not transmitted from adults to cocoons. Prolonged studies involving the addition of CoCl2 (0, 8.2, 16.5 and 82.5 μg Co g?1) to a food source low in Co indicated that total Co concentrations of 17.6 and 25.9 μg g?1 resulted in significantly increased maximum weights compared to the control worms which were exposed to 9.4 μg Co g?1. The highest Co addition (82.5 μg g?1, total 91.9 μg g?1) caused no increase in maximum weight over controls, but resulted in a statistically significant lag in early growth compared to that of all other groups. Significantly more cocoons were produced by worms fed 17.6 or 25.9 μg Co g?1 compared with those fed 9.4 or 91.9 μg Co?1 Co.  相似文献   

12.
Phosphorus control measures at two major (>10000 people equivalent, p.e.) sewage treatment works (STWs) were installed in the lowland calcareous basin of the River Wensum (England). In-stream phosphorus concentrations were monitored seasonally from subcatchments with different levels of phosphorus impacts, as well as before and after phosphorus control, above and below the two major STWs. Point source effluents raised in-stream soluble reactive phosphorus (SRP) concentrations from 9–15 μg L?1 (agricultural sub-catchments) to 580–3270 μg L?1. This was accompanied by an increase of the SRP relative to total phosphorus from 27% to 80–90%. The phosphorus content of the suspended sediment was high (0.2 to 7.7%). Molybdate unreactive phosphorus (1–29 μg L?1) was surprisingly not affected by point source effluents. The river bed sediment bioavailable phosphorus concentrations were higher (4–18 μg g?1 wet weight) downstream from the main effluents, compared to upstream (2–6 μg g?1 wet weight). Phosphorus control at the STWs in 1999 has allowed to reduce in-stream soluble reactive concentrations to 140–280 μg L?1 but has had no significant impact on bioavailable phosphorus in the sediment by 2001, suggesting that either net sediment desorption did not occur or that it is a much slower, longer term response. The relative contribution of the diffuse sources increased from 10% to 27% of the total phosphorus loads at Fakenham. The management of these rivers is therefore problematic.  相似文献   

13.
A monitoring study was carried out in an alluvial fan area in Tsukui, Central Japan during the study period of 1999–2003, in order to explain selenium (Se) behaviors in ecosystem combined with air, soil and groundwater. Monthly Se concentrations in open bulk precipitation (rainfall+aerosol, gaseous deposition and etc.), soil solution (collected by porous ceramic-cup) and groundwater ranged from 0.1 to 1.4 μg L?1 (volume-weighted average: 0.34 μg L?1), 0.21 to 1.0 μg L?1 (0.48 μg L?1) and 1.6 to 2.4 μg L?1 (2.2 μg L?1), respectively. Se concentration in open bulk precipitation was negatively correlated with the rainfall amount. Se concentration in soil solution significantly increased with DOC concentration in soil solution. Besides, despite atmospheric Se input and rainfall to the grassland study area, Se concentration in soil solution and groundwater received no significant effect from the rainfall amount, pH, Se, DOC, SO4 2?, NO3 ? and EC in rainfall. Even though Se concentrations in groundwater were significantly correlated with soil solution volume, Se, DOC and NO3 ? and groundwater level, the result of multiple regression analyses (MRA) indicated that the groundwater Se was negatively influenced by groundwater level, which depended on groundwater recharge. Se was transported into the groundwater through the groundwater recharge that largely increased in this alluvial fan study area after heavy rain.  相似文献   

14.
The effects of Cu(II) sulfate on sediment respiration were investigated in a 3-phase aquatic microcosm, containing a calcareous, southern Ontario stream sediment. In Cu2+ treated flask-microcosms, with the pH restored to 7.1, both aerobic and anaerobic CO2 evolution were unaffected by 5000 jig Cu g?1 sediment over a 40-day period at 15 °C. Oxygen consumption in sediment was initially unaffected by 5000 μg Cu g?1. However, after 35 to 40 days, a significant reduction of 28% was observed. The added Cu?2+ was removed from the water column and the sediment solution. In microcosms containing 5000 μg g?1 of total Cu, only 1.00 ± 0.76 μg g?1 was water soluble Cu, and the free cupric cation (Cu2+) concentration was below the detection limit of the specific ion electrode (less than 0.01 μg g?1). Maximum Cu retention (98.6%) was observed at 2800 μg Cu g?1, above which fractional retention decreased. In a calcareous, organic rich, sediment of pH 7.1, Cu+ was essentially unvailable to exert a toxic effect on respiration.  相似文献   

15.
Three months after neutralization concentrations of methylmercury (MeHg) were higher in the water of the limed than in the control basin of a small lake. After two years, the concentrations in the limed basin were somewhat lower than in the control (0.056–2.19 ng L?1 and 0.129–2.65 ng L?1, respectively). The highest concentrations were found in the anoxic hypolimnia. The total amount of MeHg in the water mass of the lake varied from 19 to 68 mg, showing a drop after spring and autumn overturns and a maximum during stratification periods. The total Hg concentrations of fish in L. Iso Valkjärvi varied from 0.06 to 0.14 μg g?1 (ww) in whitefish to 0.1 to 0.7 μg g?1 in perch and to 0.2 to 1.4 μg g?1 in pike. The total amount of MeHg bound in the fish of the lake was quite similar to that in the water column, 43 to 59 mg in 1990–1993, 33 to 47 mg of which was in the perch population.  相似文献   

16.
Sodium chloride, at rates up to 100 mg g?1, was added to a Sassafras sandy loam amended with finely-ground alfalfa to determine the effect of NaCl on CO2 evolution, ammonification, and nitrification in a 14-week study. A NaCl concentration of 0.25 mg g?1 significantly reduced CO2 evolution by 16% in unamended soil and 5% in alfalfa-amended soil. Increasing NaCl progressively reduced CO2 evolution, with no CO2 evolved from the soil receiving 100 mg NaCl g?1. A 0.50 mg NaCl g?1 rate was required before a significant reduction in decomposition of the alfalfa occurred. The NO?2-N + NO?3-N content of the soil was significantly reduced from 40 to 37 μg g?1 at 0 and 0.25 mg NaCl g?1, respectively in the unamended soil. In the alfalfa amended soil, nitrification was significantly reduced at 5 mg NaCl g?1. At 10 mg NaCl g?1, nitrification was completely inhibited, there being only 6 and 2 μg NO?2-N + NO?3-N g?1 in the alfalfa amended and unamended soil, respectively. In the alfalfa amended soil NH+4-N accumulated from 6 μg g?1 at the 0 NaCl rate to a maximum of 54 μg g?1 with 25 mg NaCl g?1. These higher NH+4-N values resulted in a 0.5 unit increase in the pHw over that of the 0 NaCl rate in the alfalfa amended soil. At NaCl concentrations above 25 mg g?1 there was a reduction in NH+4-N. The addition of alfalfa to the soil helped to alleviate the adverse affects of NaCl on CO2 evolution and nitrification.  相似文献   

17.
In the course of a series of studies conducted to investigate the long-term behavior of 129I (which has a half-life of 16 million years) in the environment, the concentration of stable iodine (127I) in precipitation, irrigation water and soil water to a depth of 2.5 m in a forest plot, an upland field and a paddy field in the upland area of Tsukuba, Japan, was determined. In the forest plot, the mean iodine concentrations in soil water at all the depths ranged from 0.13 to 0.21 μg L?1, about one-tenth of the values recorded in precipitation (weighted mean 2.1 μg L?1). This finding suggests that the major part of iodine in precipitation was sorbed onto the surface soil horizon under oxidative conditions. In the upland field, the mean iodine concentration in soil water was 2.2 μg L?1 at a depth of 0.2 m and it decreased to 0.34–0.44 μg L?1 at a depth of 0.5 m or more; these concentrations were about one-fifth of that in precipitation. This suggested that the major part of the iodine derived from precipitation was sorbed onto the subsurface soil horizon (at depths between 0.2 and 0.5 m). In the paddy field, during the non-irrigation period, the mean iodine concentrations in soil water at all the depths ranged from 1.8 to 4.8 μg L?1, almost the same values as those recorded in precipitation. During the irrigation period, the mean iodine concentrations at depths of 0.2 and 0.5 m were 18.8 and 16.7 μg L?1, values higher than the 10.9 μg L?1 value recorded in irrigation water and the 11.8 μg L?1 value recorded in ponding water. However, at a depth of 1.0 m or more, the mean iodine concentrations in soil water rapidly decreased from 7.3 to 1.8 μg L?1. These data suggested that a significant amount of iodine flowed out from the paddy field by surface runoff and a considerable amount of iodine that leached to a depth of 0.5 m was retained onto the mildly oxidative soil horizon (2Bw) that lay at depths between 0.5 and 1.0 m. At a depth of 2.5 m in the paddy field, the mean iodine concentration in soil water decreased to 1.8 μg L?1, but this level was much higher than those in the forest plot and upland field at the same depth, which suggested that a significant amount of iodine had leached into the groundwater-bearing layer. There was a negative correlation (r=-0.889) between the Eh of soil and the iodine concentration in soil water (0.2 m depth) of the paddy field. Particularly, when the Eh of soil fell below approximately 150 mV, the iodine concentration rapidly increased to above 10μg L?1. As for the chemical forms of iodine in precipitation, irrigation water, ponding water and soil water during the winter irrigation period in the paddy field with oxidative conditions, 58–82% of iodine consisted of IO? 3 and 17–42% of iodine consisted of I?. In the soil water during the summer irrigation period in the paddy field under reductive conditions, 52–58% of iodine consisted of I?, and 42–47% consisted of IO? 3.  相似文献   

18.
The early life stages of smallmouth bass (Micropterus dolomieui) were exposed to Pb in acute (96 hr) and sub-chronic (90 day) bioassays (water hardness = 152 mg L?1 as CaCO3). After 96-hr static exposures at nominal Pb concentrations up to 15.9 mg L?1, eggs and sac fry showed no increased mortality over that in controls. Swim-up fry (96-hr LC50 = 2.8 mg Pb L?1) were more sensitive to Pb exposure than were fingerlings (96-hr LC50 of 29.0 mg Pb L?1 ). The relation between dissolved Pb and mortality was non-significant for either swim-up fry or fingerlings. Fingerlings were exposed to Pb concentrations as high as 405 μg L?1 for 90 day to evaluate effects on substrate selection, locomotor activity, hematology, and weight. Dark or light substrate selection (cover-seeking) and locomotor activity, weight and hemoglobin concentration in the blood were not significantly altered by any treatment. Hematocrit and leucocrit varied significantly but not in relation to Pb levels. Sub-chronic Pb exposure did not appear to represent a threat to smallmouth bass in waters of medium hardness and above-neutral pH (7.1 to 7.9).  相似文献   

19.
Nitrogen dioxide gas was rapidly absorbed by soil. After a 15 min incubation at 25°C, soil at a moisture content of 16% absorbed 99% of the NO2 introduced into the gas-phase volume of a closed system. The presence of microorganisms hatl no influence on the rate of absorption of the gas by soil. The absorption of NO2 by sandy clay loam soil was not an oxygen- or temperature-dependent process nor did it depend upon the moisture content of the soil. These physical factors acquired significance only in determining the initial rate of absorption of the gas and the rate at which NO2 diffused through the soil. Exposure of soil to NO2 resulted in substantial increases in the levels of NO inf2 sup? N in the soil. Chemical oxidation of the NO inf2 sup? N resulted in an increase in NO inf3 sup? N levels. During a 14-day incubation, NO inf2 sup? N concentrations in sterile soil exposed to an atmosphere containing 100 μg ml?1 of NO2 decreased from 190 μg g?1 of soil to 105 μg g?1 with an accompanying increase in NO inf3 sup? N from 2 μg g? 1 to 63 μg g?1 of soil. Nitrogen dioxide severely inhibited the growth of both aerobic and anaerobic asymbiotic N2-fixing bacteria in soil. After a 48 h incubation at 25°C, soil aggregates exposed to an atmosphere containing 100 μg ml?1 of NO2 contained 88% and 98% fewer aerobic and anaerobic N2-fixing bacteria, respectively. C2H2-reduction measurements showed that nitrogenase synthesis and activity in artificial soil aggregates amended with 2% glucose were inhibited by 20% and 48%, respectively, when exposed to atmospheric concentrations of 35 and 3.5 μg ml?1 of NO2, respectively.  相似文献   

20.
Volume regulation (weight change) correlates with varying salinity — Cu regimes in whole worms. Decapitation removed this correlation. Regulation of volume and Cu ion uptake are not coupled. Whole worms when exposed to Cu levels of 0.15 to 0.45 mg L?1 accumulated Cu which ranged from 48.9 to 145 μg g?1 dry weight within four days. Decapitated worms exposed to similar doses of Cu accumulated from 77.3 to 405.4 μg g?1 dry weight Cu within three days. Volume regulation appears to be both passive and active processes mediated by the nervous system.  相似文献   

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