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1.
The effects of adding a crushed cotton gin compost (CCGC) and poultry manure (PM) on the biological properties of a Typic Xerofluvent soil contaminated with Ni were studied in the laboratory. Urease, BBA-protease, alkaline phosphatase, β-glucosidase and arylsulfatase activities were measured in soils containing seven concentrations (100, 250, 500, 1000, 2500, 5000 and 8000 mg kg−1 soil) of Ni after four incubation times (1 day, 7 days, 15 days and 45 days). The resulting inhibition was compared with that of the enzymatic activities in the same soil containing similar concentrations of the Ni but amended with crushed cotton gin compost and poultry manure. The 50% ecological dose (ED50) values were calculated by the two kinetic models used by Speir et al. [T.W. Speir, H.A. Kettles, A. Parshotam, P.L. Searle, L.N.C. Vlaar, A simple kinetic approach to derive the ecological dose value, ED50, for the assessment of Cr(VI) toxicity to soil biological properties, Soil Biol. Biochem. 27 (1995) 801–810] and by the sigmoidal dose–response model used by Haanstra et al. [L. Haanstra, P. Doelman, J.H. Oude Voshaar, The use of sigmoidal dose response curves in soil ecotoxicological research, Plant Soil 84 (1985) 293–297]. The urease, BBA-protease, β-glucosidase, alkaline phosphatase and arylsulfatase activities were higher in the organic amended soils (76%, >99.7%, >95.7%, >27.6% and >87.2%, respectively) than in the control soil. Also, the enzymatic activities were higher in CCGC-amended soils than in the PM-amended soils (51%, 20%, 11.2%, and 11.3% increase for urease, BBA-protease, β-glucosidase and alkaline phosphatase, respectively). For all soil enzymatic activities and at the end of the period of incubation, the ED50 values were lowest in control soil, followed by PM and CGCC-amended soils. This may have been due to the adsorption capacity of Ni being higher in the humic acid (CGCC) than in the fulvic acid-amended soil (PM).  相似文献   

2.
Organic wastes such as sewage sludge and compost increase the input of carbon and nutrients to the soil. However, sewage sludge-applied heavy metals, and organic pollutants adversely affect soil biochemical properties. Therefore, an incubation experiment lasting 90 days was carried out to evaluate the effect of the addition of two sources of organic C: sewage sludge or composted turf and plant residues to a calcareous soil at three rates (15, 45, and 90 t of dry matter ha–1) on pH, EC, dissolved organic C, humic substances C, organic matter mineralization, microbial biomass C, and metabolic quotient. The mobile fraction of heavy metals (Zn, Cd, Cu, Ni, and Pb) extracted by NH4NO3 was also investigated.The addition of sewage sludge decreased soil pH and increased soil salinity to a greater extent than the addition of compost. Both sewage sludge and compost increased significantly the values of the cumulative C mineralized, dissolved organic C, humic and fulvic acid C, microbial biomass C, and metabolic quotient (qCO2), especially with increasing application rate. Compared to compost, the addition of sewage sludge caused higher increases in the values of these parameters. The values of dissolved organic C, fulvic acid C, microbial biomass C, metabolic quotient, and C/N ratio tended to decrease with time. The soil treated with sewage sludge showed a significant increase in the mobile fractions of Zn, Cd, Cu, and Ni and a significant decrease in the mobile fraction of Pb compared to control. The high application rate of compost resulted in the lowest mobility of Cu, Ni, and Pb. The results suggest that biochemical properties of calcareous soil can be enhanced by both organic wastes. But, the high salinity and extractability of heavy metals, due to the addition of sewage sludge, may limit the application of sewage sludge.  相似文献   

3.
Summary The aim of this study was to provide data to evaluate the short- and long-term effects of heavy metals on arylsulphatase activity in five soils. The effects are fitted on a logistic dose-response model and are presented graphically as the ecological dose (heavy metal concentration corresponding to 50% inhibition; ED50) and ecological dose range (heavy metal concentration range corresponding to 10–90% inhibition; EDR). In 7 out of 22 comparable soil-metal combinations the ED50 decreased significantly over 6 weeks to 18 months of incubation and in two cases the ED50 increased. Toxicity (defined as ED50) was highest in sand and sandy loam and lowest in sandy peat. Cd toxicity in sand, silty loam, and clay varied from 1.08 to 9.04 mmol kg-1. Both Cr and Ni toxicity varied strongly and decreased with time in some soils while increasing in others. The Cu toxicity ranged from 4.51 to 2 mmol kg-1 in sand and silty loam, respectively, but remained fairly constant over time. Pb was the least toxic element (14.5 to 59.9 mmol kg-1). The toxicity of Zn ranged from 5.73 to 148 mmol kg-1 in sand and sandy peat, respectively. At critical concentrations set by the Dutch Soil Protection Act, Cr, Cu, Ni, and Zn inhibited arylsulphatase by 53, 35, 48 and 97%, respectively.  相似文献   

4.
Saviozzi  A.  Levi-Minzi  R.  Cardelli  R.  Biasci  A.  Riffaldi  R. 《Water, air, and soil pollution》2001,128(1-2):13-22
A laboratory experiment was performedto evaluate the suitability of moist olive pomace(MOP) as soil amendment. Moist olive pomace wasobtained from a new olive-oil industrial processcalled the `two-phases method'. Soil samples weremixed with MOP to approximate a field application of40 t ha-1 and incubated under aerobic conditionsat 20 °C and 60% of soil water holdingcapacity. To estimate the effect of different loadingrates and N supply on mineralization, 40, 80, 120 and160 t ha-1 of MOP and 200 ppm of N as(NH4)2SO4 were used. CumulativeCO2-C evolution, total microbial activity andbiomass-C were monitored during a 60-day period.Results indicate that the CO2-C evolution fromMOP depends on soil type and is temporarily inhibitedin acidic soils. Evolution of CO2-C increaseswith incremental addition of MOP, but the percentagesof the added C that were mineralized decreased withincreasing application rates. Mineral N supplementsresult in more efficiency of the mineralizationprocess. Among the kinetic models tested to describethe mineralization dynamics, a first-order exponentialmodel including a constant term provides the best fitto the experimental data. Both amount and activity ofsoil microbial biomass are enhanced by MOP added atthe 40 t ha-1 rate, at least in the first periodof incubation. At higher rates of MOP addition, aconstant increase of biomass C during incubation isobserved, while the biological activity decreases atthe end of incubation. Following application ofmineral N, both amount and activity of microbialbiomass is enhanced.  相似文献   

5.
Soil C balances were calculated in a field experiment started in 1956. Treatments include a fallow and soils receiving different N fertilizers or organic amendments. By assuming the absence of a priming effect, the degree of mineralization of crop residues and organic amendments was calculated. Crop residue mineralization was not affected by a more than 50% decrease in the size of the microbial biomass in soil fertilized with (NH4)2SO4, which had caused the pH of this soil to drop from 6.6 to 4.4. More C had accumulated per unit C input in peat-and sewage sludge-amended soils than in any of the other soils, suggesting that peat and sewage sludge were more resistant to microbial attack. Recalcitrance of substrate C was an adequate explanation for the low ratio of biomass C to soil C in the peat-amended soils, but not in the sewage sludge-amended soil. There was a close linear relationship (r=0.94) between the content of microbial biomass C in the soil measured in 1990 and cumulative C losses from the soil since 1956. Compared to the relationship between soil biomass C and soil organic C concentrations, the linear relationship between microbial C and cumulative C losses suggested that the significantly reduced biomass in the sewage sludge-amended soil was at least partially due to the presence of toxic substances (presumably elevated heavy metal concentrations) in this soil and was probably not affected by the somewhat low pH (5.3) in this soil.  相似文献   

6.
A comparative study was conducted on the toxicity of Cd to alkaline phosphatase activity (ALP) and dehydrogenase activity (DHA) in 18 top soils with contrasting soil properties representative of 14 major soil types in China. Soil pH and carbonate content, soil organic matter, and cation exchange capacity (CEC) largely affected the Cd toxicity on two enzyme activities; with the soil pH having only minor effect on the median ecological dose values based on total Cd concentrations (ED50 T). The values of ED50 T/ED50 W (based on water-soluble Cd content) of alkaline phosphatase and dehydrogenase were strongly influenced by pH and CEC contents, which explained up to 71% of the variation for alkaline phosphatase, 82% of the variation for dehydrogenase, and also were significantly correlated with the parameter KF derived from Freundlich adsorption isotherms. This study suggests that the values of ED50 T/ED50 W could be useful to evaluate the buffer capacity of soils which protects soil enzymes from harmful effects of heavy metal.  相似文献   

7.
The ecological dose (ED50) of Cd on alkaline and acid phosphatase activity and the ATP content of three contrasting forest soils was measured with or without Cu and Zn to assess the additive toxic effects of these two metals. Soils polluted with Cu and/or Zn were treated with increasing Cd concentrations to give the following metal combinations: Cd, Cd+Cu, Cd+Zn and Cd+Cu+Zn. Alkaline and acid phosphatase activities and ATP content of the three soils were analysed 4 h, 7 and 28 days after the metal additions. The ED50 values were obtained by interpolating the enzyme activities or ATP data with a kinetic model and the goodness of fit was satisfactory.Generally, the ED50 values of both acid and alkaline phosphatase activities for Cd were lower (higher toxicity) with than without Cu and Zn and the effect of Cu and Zn was particularly adverse when these two metals were both added to soils. The alkaline phosphatase was more sensitive in the acid and neutral soil whereas the acid phosphatase was more sensitive in the alkaline soil. Both phosphatase activities and the ATP content were more sensitive in the sandy than in the finer textured soils. The ATP content was less sensitive to the additive effects. Increasing toxicity was observed during the incubation.Analysis of 1 M NH4NO3-extractable Cd, Cu and Zn revealed that Cd competed with Zn for the adsorption sites but not with Cu. However, the lower ED50 values for Cd of the two phosphatase activities and of the ATP content in the presence of heavy metal combinations could be not explained by the heavy metal solubility data. It is concluded that the ED50 may be a sensitive tool for assessing additve toxic effects to soil biochemical parameters.  相似文献   

8.
The aim of this study was to provide data to assess the additive effects of soil salinity on the toxicity of Cd to soil alkaline phosphatase (EC 3.1.3.1). Two soils (Langroud acid soil and Shervedan calcareous soil) were artificially salinized with NaCl. The natural and salinized soils were treated with CdSO4 solutions to give a Cd concentration in the range 3–5000 mg kg?1. Soil alkaline phosphatase activity was measured after 3 days of incubation. Salinity enhanced the extractable Cd concentration in both Langroud and Shervedan soils. The percentage of soil alkaline phosphatase activity inhibited by Cd was significantly increased from 27.8 to 45 in the Langroud acid soil as salinity increased from natural levels to 28 dS m?1. An increase in the inhibition percentage was not observed in the Shervedan soil. Lower values for the ecological dose causing 50% inhibition (ED50) under saline conditions in the Shervedan soil supported the hypothesis that Cd may be more toxic to soil alkaline phosphatase when the soil is more saline. We conclude that Cd toxicity to soil alkaline phosphatase is salinity dependent and that higher Cd concentrations under saline conditions are probably responsible for the enhanced Cd toxicity to soil alkaline phosphatase.  相似文献   

9.
Summary The aim of this study was to provide manageable data to help establish permissible limits for the pollution of soil by heavy metals. Therefore the short-and long-term effects of heavy metal pollution on phosphatase activity was studied in five different soil types. The results are presented graphically as logistic dose-response curves. It was possible to construct a curve for sand and silty loam soil but it was more difficult to establish a curve for sandy loam and clay soil and nearly impossible (except for Cu) for peat. The toxicity of the various metals can be compared on the basis of mmol values. In clay soils, for Cd, Cr, Cu, and Zn, the 50% effective ecological dose (ED50) values were comparable (approximately 45 mmol kg–1), but the ED10 values were very different, at 7.4, 41.4, 15.1, and 0.55, respectively. At the ED50 value, toxicity did not decrease with time and, in sandy soils, was approximately 2.6 mmol kg –1 dry soil for Cd, Cu, and Zn. In four out of five soils, the Cd toxicity was higher 1.5 years after the addition of heavy metal salts than after 6 weeks. Toxicity was least in the sandy loam, silty loam, and clay soil, and varied in general between 12 and 88 mmol kg–1. In setting limits, the criteria selected (no-effect level, ED10 or ED50) determine the concentration and also the toxicity of the sequence. It is suggested that the data presented here could be very useful in helping to set permissible limits for heavy metal soil pollution.  相似文献   

10.
We established a field trial to assess the impacts on soil biological properties of application of heavy metal-spiked sewage sludge, with the aim of determining toxicity threshold concentrations of heavy metals in soil. Plots were treated with sludges containing increasing concentrations of Cu, Ni and Zn in order to raise the metal concentrations in the soil by 0-200 mg Cu kg−1, 0-60 mg Ni kg−1 and 0-400 mg Zn kg−1, and were then cultivated and sown in ryegrass-clover pasture and monitored annually for 6 years. All biological properties measured (soil basal respiration, microbial biomass C, and sulphatase enzyme activities), except phosphatase activity, increased in all plots over the duration of the experiment. Consequently, it was only possible to assess effects of heavy metals across time if, each year, all data for each metal were normalised by expressing them as percentages of the activities measured in an un-sludged control plot. When this was done, no significant effects of increasing heavy-metal concentrations on basal respiration, microbial biomass C or respiratory quotient (qCO2) were observed, although total Cu and soil solution Cu were significantly negatively related to microbial biomass C when it was expressed as a proportion of soil total C. None of the properties measured were affected by increasing Ni concentrations. Phosphatase and sulphatase activities were significantly negatively related to increasing Zn concentrations, but not usually to increasing Cu unless they were expressed as a proportion of total C. A sigmoidal dose-response model was used to calculate EC20 and EC50 values using the normalised data, but generally, the model parameters had very large 95% confidence intervals and/or the fits to the model had small R2 values. The factors primarily responsible for confounding these results were site and sample variations not accounted for by the normalisation process and the absence of any data points at metal concentrations beyond the calculated EC50 values. In the few instances where reasonable EC20 values could be calculated, they were relatively consistent across properties, e.g., EC20 for total Zn and phosphatase (330 mg kg−1), total Zn and sulphatase (310 mg kg−1), and EC20 for total Cu and sulphatase (140 mg kg−1) and total Cu and microbial biomass C (140 mg kg−1), when both sulphatase and microbial biomass C were expressed as a proportion of total C. Our results suggest that Cu and Zn at the upper concentrations used in this experiment were possibly having adverse effects on some soil biological properties. However, much higher metal concentrations will be needed to accurately calculate EC20 and EC50 and this may not be easily achievable without many applications of sewage sludge, even if the sludge is spiked with heavy metals.  相似文献   

11.
《Soil biology & biochemistry》2001,33(4-5):483-489
Two soils of contrasting texture, organic matter content and pH were treated with CdSO4 solutions to give a Cd concentration range of 0–4000 mg kg−1 soil. The content of ATP and dehydrogenase and urease activities of soils were assayed after 3 h, and 7 and 28 days of Cd contamination. The relative ED50 values were calculated by two kinetic models (model 1 and model 2) used by Speir et al. (1995) and by the sigmoidal dose–response model (model 3) employed by Haanstra et al. (1985). Model 1 was the most successful in calculating the ED50 values for the ATP content, urease and dehydrogenase activities when both soils were contaminated by Cd. Similar ED50 values were predicted by model 1 (describing the full inhibition) and model 3 only when the correlation coefficients r2 were higher than 0.9. The ED50 values of ATP calculated by model 1 were markedly higher than those calculated by model 2 (describing partial inhibition) when both models gave correlation coefficients higher than 0.9. This behavior was due to the high asymptote values obtained using model 2. According to model 2, some of the enzyme activities responsible for the ATP synthesis were probably not inhibited at the highest Cd concentrations. The inhibitory effect of Cd on the ATP content and both enzymatic activities was lower in the Castelporziano soil, which had the highest total organic carbon content.  相似文献   

12.
Risk assessment of the nitrification inhibitors (NIs) 3,4-dimethylpyrazole phosphate (DMPP), 4-chloromethylpyrazole (ClMP), and dicyandiamide (DCD) on nontarget microbial activity in soils was determined by measuring dehydrogenase and dimethyl sulfoxide reductase activity (DHA, DRA, respectively) in three differently textured soils under laboratory conditions. Dehydrogenase activity was measured with standard procedure recommended to evaluate side effects of environmental chemicals on general microbial activity in soils. The kinetic of inhibition were obtained by dose–response relationships and used to calculate the no observable effect levels (NOEL values) and the effective doses at 10% and 50% inhibition (ED10 and ED50), respectively. Negative effects on DHA and DRA, respectively, were observed only at rates approximately 40–100 times higher than the concentrations recommended in the field. Both DHA and DRA were affected more in the sandy than in the silty or clayey soil. Consequently, NOEL, ED10, and ED50 values were considerably higher in the clayey than in the silty or sandy soil. The heterocyclic N compounds DMPP and ClMP, respectively, were more effective in inhibiting DHA and DRA than DCD. At application rates used in the field as well as at concentration up to 25 to 90 times higher, the NIs concerned failed to affect general soil microbial activity in soils. Among the three NIs tested, the not marketed ClMP exhibited the strongest negative effects on soil microbial activity. At recommended application rates, the NIs tested should be considered as enviromentally safe.  相似文献   

13.
Sewage sludge produced by the SABESP wastewater treatment plant (Companhia de Saneamento Básico do Estado de São Paulo), located in Barueri, SP, Brazil, may contain high contents of nickel (Ni), increasing the risk of application to agricultural soils. An experiment was carried out under field conditions in Jaboticabal, SP, Brazil, with the objective of evaluating the effects on soil properties and on maize plants of increasing rates of a sewage sludge rich in Ni that had been applied for 6 consecutive years. The experiment was located on a Typic Haplorthox soil, using an experimental design of randomized blocks with four treatments (rates of sewage sludge) and five replications. At the end of the experiment the accumulated amounts of sewage sludge applied were 0.0, 30.0, 60.0 and 67.5 t ha−1. Maize (Zea mays L.) was the test plant. Soil samples were collected 60 d after sowing at depths of 0-20 cm for Ni studies and from 0 to 10 cm and from 10 to 20 cm for urease studies. Sewage sludge did not cause toxicity or micronutrient deficiencies to maize plants and increased grain production. Soil Ni appeared to be associated with the most stable fractions of the soil organic matter and was protected against strong extracting solutions such as concentrated and hot HNO3 and HCl. Ni added to the soil by sewage sludge increased the metal concentration in the shoots, but not in the grain. The Mehlich 3 extractor was not efficient to evaluate Ni phytoavailability to maize plants. Soil urease activity was increased by sewage sludge only in the layer where the residue was applied.  相似文献   

14.
Though engineered covers have been suggested for reducing landfill methane emissions via microbial methane oxidation, little is known about the covers' function at low temperature. This study aimed to determine the methane consumption rates of engineered soil columns at low temperature (4–12°C) and to identify soil characteristics that may enhance methane oxidation in the field. Engineered soils (30 cm thick) were mixtures of sewage sludge compost and de-inking waste, amended with sand (SDS soil) or bark chips (SDB soil). At 4–6°C, we achieved rates of 0.09 gCH4 kgTS?1d?1 (0.02 m3 m?2d?1) and 0.06 gCH4 kgTS?1d?1 (0.009 m3 m?2d?1) with SDS and SDB soils, respectively. With SDS, good movement and exchange of oxygen in porous soil moderated the slowdown of microbial activity so that the rate dropped only by half as temperature declined from 21–23°C to 4–6°C. In SDB, wet bark chips reduced the soil's air-filled porosity and intensified non-methanotrophic microbial activity, thus reducing the methane consumption rate at 4–6°C to one fourth of that at 21–23°C. In conclusion, soil characteristics such as air-filled porosity, water holding capacity, quantity and stabilization of organic amendments that affect the movement and exchange of oxygen are important variables in designing engineered covers for high methane oxidation at low temperature.  相似文献   

15.
The common soil protozoan Colpoda steinii was used to study the toxicity of sulphate solutions of Ni, Cd, Cu, and Zn. The growth of C. steinii was reduced by 50% in the presence of 0.10, 0.22, 0.25, and 0.85 mg litre-1 of Ni, Cd, Cu and Zn, respectively, during 24 h of incubation at 25°C, as calculated from a regression analysis of probit-transformed data. The same growth assay was used to assess the toxicity of soil solution extracted by centrifugation from soil samples of field plots of a grass/clover ley on a sandy loam treated with sewage sludge spiked with additional Cd, Cu, Cr, Ni, Pb, or Zn at concentrations either equivalent to or twice the limits for heavy metals recommended in recent EC guidelines (Commission of European Communities directive 86/278/EEC). The toxicity of these soil solutions varied with the season of the year. None of the soil solutions extracted in winter (February 1991) inhibited the growth of C. steinii. In summer (July 1991), the growth was reduced in solutions extracted from plots that were amended with sludge plus additional Zn or Ni at twice the maxima recommended by the EC. The changes in toxicity to C. steinii of the soil solutions between February and July were positively correlated with increases in heavy metal concentrations of Zn and Ni between winter and summer. These preliminary results suggest that regular protozoan bioassays may be used to monitor the biological availability of heavy metals in soils, especially when combined with other microbial assays and with chemical analyses of soil solutions.  相似文献   

16.
The fixation of radioactive C was used to mesaure the toxicity of Pb(NO3)2 to five species of freshwater algae. Portions of unialgal cultures were inoculated into low salt medium and were used to test all species at 10, 20 and 30 ppm Pb. This medium approximated the salt concentrations of natural aquatic environments. Three different cell weights were used for each concentration of Pb and for the control to determine a relationship between cell weight and toxicity. The concentration of Pb causing a 50% reduction of14CO2 fixation as compared to the control was called the ED50 (median effective dose). These values were extrapolated from graphs of ppm Pb vs dpm mg?1 dry cell weight. The ED50 for three of the species tested (Anabaena, Chlamydomonas andNavicula) was between 15 and 18 ppm Pb. A desmid,Cosmarium, had an ED50 of 5 ppm. This species has a higher surface: volume ratio than the other species tested and this may account for its increased sensitivity. An ED50 forOchromonas was not obtained. Throughout this experiment the fixation of14CO2 increased with increasing Pb concentrations and is not readily explained.  相似文献   

17.
Tea (Camellia sinensis) is a globally important crop and is unusual because it both requires an acid soil and acidifies soil. Tea stands tend to be extremely heavily fertilized in order to improve yield and quality, resulting in a great potential for diffuse pollution. The microbial ecology of tea soils remains poorly understood; an improved understanding is necessary as processes affecting nutrient availability and loss pathways are microbially mediated. We therefore examined the relationships between soil characteristics (pH, organic C, total N, total P, available P, exchangeable Al), the soil microbial biomass (biomass C, biomass ninhydrin-N, ATP, phospholipid fatty acids—PLFAs) and its activities (respiration, net mineralization and nitrification). At the Tea Research Institute, Hangzhou (TRI), we compared fields of different productivity levels (low, medium and high) and at Hongjiashan village (HJS) we compared fields of different stand age (9, 50 and 90 years). At both sites tea soils were compared with adjacent forest soils. At both sites, soil pH was highest in the forest soil and decreased with increasing productivity and age of the tea stand. Soil microbial biomass C and biomass ninhydrin-N were significantly affected by tea production. At TRI, microbial biomass C declined in the order forest>low>high>middle production and at HJS in the order stand age 50>age 9>forest>age 90. Soil pH had a strong influence on the microbial biomass, demonstrated by positive linear correlations with: microbial biomass C, microbial biomass ninhydrin-N, the microbial biomass C:organic C ratio, the microbial biomass ninhydrin-N:total N ratio, the respiration rate and specific respiration rate. Above pH(KCl) 3.5 there was net N mineralization and nitrification, and below this threshold some samples showed net immobilization of N. A principal component (PC) analysis of PLFA data showed a consistent shift in the community composition with productivity level and stand age. The ratio of fungal:bacterial PLFA biomarkers was negatively and linearly correlated with specific respiration in the soils from HJS (r2=0.93, p=0.03). Our results demonstrate that tea cultivation intensity and duration have a strong impact on the microbial community structure, biomass and its functioning, likely through soil acidification and fertilizer addition.  相似文献   

18.
 This study focuses on a comparison of the microbial toxicity of nine metals, including As as a metalloid and two species of Cr. A loess soil [Ap horizon, clay 15.2%, organic C 1.12%, pH(CaCl2) 7.02] was spiked with 8–12 geometrically increasing doses of the metals. The dehydrogenase assay (2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazoliumchloride method) was combined with sorption and solubility experiments. The resulting dose-response curves and sorption isotherms were used to derive total doses that caused definite percentage inhibitions [i.e. effective doses (ED) causing a 10–90% reduction in dehydrogenase activity (dha)] as well as the corresponding toxic solution concentrations causing the same reductions in dha (i.e. effective concentrations; EC10–EC90). Based on total doses, the toxicity decreased in the following order with ED50 values (mg kg–1) given in brackets: Hg (2.0)>Cu (35)>Cr(VI) (71)>Cr(III) (75)>Cd (90)>Ni (100)>Zn (115)>As (168)>Co (582)>Pb (652). With regard to solution concentrations, toxicity decreased in the order (EC50 in mg l–1): Hg (0.003)>Pb (0.04)>Cu (0.05)>Cd (0.14)>Zn (0.19)>Cr(III) (0.62)>Ni (0.69)>Co (30.6)>As (55.5)>Cr(VI) (78.1). The retention of the metals by the soil differed strongly. Pb, Cu, and Hg exhibited the highest and Ni, As, and Cr(VI) the lowest sorption constants (Freundlich K values: 2455, 724, 348, 93, 13, and 0.06 mg kg–1, respectively). The sorptivity of the metals and their microbial toxicity in the aqueous phase were characteristically related: metals with a strong toxic action in the soil solution were adsorbed by the soil to a high degree and vice versa. Therefore, especially for metals with a high inherent toxicity, sorption is an effective way of immobilizing them and temporarily detoxifying soil. Received: 2 July 1998  相似文献   

19.
Zeolitites (ZTs) are rocks containing more than 50% of zeolite minerals and are known to be a suitable material for agricultural purposes by improving soil physicochemical properties and nitrogen (N) use efficiency. However, little is known about their effects on soil microbial biomass. This study aimed to evaluate short-term effects of different chabazite-rich ZT (CHAZT) amendments on soil microbial biomass and activity. A silty-clay agricultural soil was amended in three different ways, including the addition of natural (5% and 15%) and NH_4~+-enriched (10%) CHAZT. Soil dissolved organic carbon (C), total dissolved N, NH_4~+, NO_3~-, NO_2~-, microbial biomass C and N, and ergosterol were measured periodically over 16 d in a laboratory incubation. To verify the microbial immobilization of the N derived from NH_4~+-enriched CHAZT, a high15N source was used for enriching the mineral to measure the microbial biomass δ15N signature. An increase in the ergosterol content was observed in the soil amended with 5% natural CHAZT. However, no similar result was observed in the soil amended with 15% natural CHAZT, suggesting that the fungal biomass was favored at a lower CHAZT application rate. In the soil amended with NH+ 4-enriched CHAZT, microbial biomass N was related to NO_3~-production over time and inversely related to NH_4~+, suggesting high nitrification process. Isotopic measurements on microbial biomass confirmed immediate assimilation of N derived from NH_4~+-enriched CHAZT. These results suggested that the NH_4~+-enriched CHAZT used in this study supplied an immediately available N pool to the microbial biomass.  相似文献   

20.
The aim of the present study was to determine the influence of light soil fertilization using sewage sludges or composts on soil toxicity for three plant species (Lepidium sativum, Sorgo saccharatum, and Sinapis alba) and crustaceans (Heterocypris incongruens). The results obtained were compared to the polycyclic aromatic hydrocarbon (PAHs) content as a potential toxicity factor. The PAH content in soils fertilized with sludges was proportional to the dose applied. Soil fertilization with the studied materials negatively influenced plant growth and development. The negative influence was clearer in the case of sewage sludges than composts. Both sludges and composts significantly influenced H. incongruens mortality. However, the influence of sludges and composts on H. incongruens growth did not exceed 20%. The EC50 and LC50 values calculated on the basis of toxicity parameters showed that H. incongruens was characterized by a higher sensitivity to sludges and composts than most of the plants. L. sativum was characterized by the lowest EC50 values among all plants. No significant relationships between sewage sludge or compost toxicity and their PAHs content were observed.  相似文献   

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