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 562 毫秒
1.
Degradation of the sulfonanilide herbicide diclosulam was studied on nine soils from three countries to determine the rates and products of aerobic metabolism. Diclosulam was applied to four agricultural soils from the United States, three from Argentina, and two from Brazil at a rate of 0.1 ppm, equivalent to approximately twice the maximum field application rate of 52 g of active ingredient/ha. U.S. and Brazilian soils were incubated in the dark at 25 degrees C at 75% 0.3 bar moisture; Argentinean soils were incubated in the dark at 20 degrees C and 45% moisture holding capacity. Samples were analyzed up to one year after treatment. Two-compartment DT(50) and DT(90) values averaged 28 +/- 12 and 190 +/- 91 days, respectively. Three soil metabolites reached levels of >10% of applied in at least one soil and were identified as the 5-hydroxy analogue of diclosulam (5-OH-diclosulam), aminosulfonyl triazolopyrimidine (ASTP), and the 8-chloro-5-hydroxy analogue of diclosulam (8-Cl-diclosulam). The terminal products of diclosulam soil metabolism were mineralization to CO(2) and bound soil residues. Apparent sorption coefficients (K(d)) were determined on a subset of samples by extraction with a 0. 01 M CaCl(2) solution followed by an acidified acetone extraction. Initial sorption coefficients were similar to those obtained in a batch equilibrium study and averaged 1.1 L/kg for the six soils tested. K(d) coefficients for the metabolites, when available, tended to be slightly lower than that for diclosulam. Sorptivity of diclosulam and degradates increased with time.  相似文献   

2.
Photodegradation of rotenone in soils under environmental conditions   总被引：1，自引：0，他引：1  
An environmental fate study was performed to analyze the effects of soil components on the photochemical behavior of rotenone. Photodegradation experiments were carried out on three types of soil collected in southern Italy, Valenzano (VAL), Turi (TUR), and Conversano (CON), from April to June 2006. Soil thin-layer plates (1 mm thick) were spiked with 1.5 mg/kg of rotenone and exposed under natural conditions of sunlight and temperature. The plates were removed from the sunlight at predetermined intervals of continuous irradiation. Other soil samples, control and sterilized, were kept in the dark to evaluate possible effects of chemical and microbiological degradation during the irradiation experiment. The time for 50% loss of the initially applied rotenone varied from 5 to 7 h, following the order TUR < CON < VAL. In environmental studies, changes in temperature and/or moisture affected the degradation rate and caused deviations from first-order kinetics. The photolysis reaction fit the two compartment or the multiple compartment model pathways better. A fast initial decrease during the first 5 h of rotenone irradiation was followed by a much slower decline, which clearly indicates the rather complex chemical process of rotenone photodegradation on soil surfaces. Also, the degradation was shown to be directly related to the soil concentration of clay and organic matter. Rotenolone (12abeta-hydroxyrotenone) was detected by HPLC/DAD/MS analysis as the only photodegradation byproduct of rotenone in soil thin layers. Results provide additional insights on the rates and the mechanisms of rotenone degradation, aiming to describe more clearly the degradation performance of chemical residues in the environment.  相似文献   

3.
The degradation rate and sorption characteristics of the triazolopyrimidine sulfonanilide herbicide florasulam and its principal degradation product 5-hydroxyflorasulam (5-OH-florasulam) were determined as a function of temperature and moisture in three different soils. The half-life for degradation of florasulam ranged from 1.0 to 8.5 days at 20-25 degrees C and from 6.4 to 85 days at 5 degrees C. The half-life for degradation of 5-OH-florasulam ranged from 8 to 36 days at 20-25 degrees C and from 43 to 78 days at 5 degrees C. The degradation rate of both compounds was strongly influenced by temperature, with activation energies ranging from 57 to 95 kJ/mol for florasulam and from 27 to 74 kJ/mol for 5-OH florasulam. Soil moisture content had negligible impact on the degradation rate. Apparent (nonequilibrium) sorption coefficients for florasulam and 5-OH-florasulam at 0 days after treatment (DAT) were 0.1-0.6 L/kg and increased linearly with time for both florasulam and 5-OH-florasulam (r(2) > 0.90) to levels as high as 12-23 L/kg. Heats of adsorption were calculated on one soil as a function of time. Heat of adsorption values for both florasulam and 5-OH-florasulam increased as incubation time increased and the amount of each compound decreased; values were near 0 kJ/mol initially and increased to a maximum of 91 and 66 kJ/mol for florasulam and 5-OH-florasulam, respectively.  相似文献   

4.
The fates of clomazone [2-(2-chlorophenyl)methyl-4,4-dimethyl-3-isoxazolidinone], molinate (S-ethyl hexahydro-1-H-azepine-1-carbothioate), and thiobencarb {S-[(4-chlorophenyl)methyl]diethylcarbamothioate} applied to rice were studied at two locations in New South Wales (Australia). Rates of dissipation (DT50) from floodwaters and soils were measured. Dissipation of the three herbicides from water and soil can be best explained by a first-order decay process. DT(50) values for clomazone, molinate, and thiobencarb were 7.2, 5.1, and 3.5 days, respectively, in water and 14.6, 23.9, and >46 days, respectively, in surface soil. Maximum measured concentrations of clomazone, molinate, and thiobencarb in floodwaters were 202, 1042, and 148 microg/L, respectively, taking 18.4, 26.4, and 21.4 days to dissipate to concentrations set to protect aquatic ecosystems. A hazard assessment identified clomazone as presenting a low environmental hazard while molinate and thiobencarb presented a medium environmental hazard when used at registered field rates.  相似文献   

5.
Effects of soil pH and soil water content on prosulfuron dissipation   总被引：3，自引：0，他引：3  
The sulfonylurea herbicide prosulfuron, 1-(4-methoxy-6-methyltriazin-2-yl)-3-[2-(3,3,3-trifluoropropyl)phenylsulfonyl]urea, is used for the selective control of broadleaf weeds in corn, sorghum, and cereal grains. To investigate its fate in soils, this study examined the effects of soil pH and water content on the rates of dissipation processes and the products formed under aerobic conditions. Radiometry and chromatography analyses were used to quantify the degradation products and bound residues formed in incubations of 10 different soils. The pH-dependent hydrolysis of the sulfonylurea bridge to form phenyl sulfonamide was the primary transformation process. Significant microbial degradation of prosulfuron occurred in 2 of the 10 soils, yielding (14)CO(2) and desmethyl prosulfuron among the major products. The time required for 50% dissipation of the herbicide (DT(50)) was determined for each soil and water content treatment. At equivalent water contents, prosulfuron DT(50) values were positively correlated with soil pH (P < 0.0001), varying from 6.5 days at pH 5.4 to 122.9 days at pH 7.9. Soil pH and water content strongly influence the fate of sulfonylurea herbicides in agricultural fields. Differences in the effect of soil water content on dissipation kinetics in a comparison of two soils were attributed to differences in soil pH, texture, and the ability of indigenous microorganisms to transform the herbicide.  相似文献   

6.
Biological degradation rates of six pharmaceuticals and personal care products were examined in soil from a land application site and in adjacent soil with no prior history of effluent exposure. Microbial degradation rates were compared over 2 weeks under standing water or saturated conditions and draining conditions after having been saturated for 3 days. Biological degradation of 17??-estradiol exhibited rapid rates of biological degradation under both saturated and draining conditions. Half-lives for 17??-estradiol ranged from 1.5 to 4 days; 66?C97% was lost from the soils. Estriol showed a pattern of biological degradation in both saturated and draining conditions though the half-lives were longer (8.7?C25.9 days) than those observed for 17??-estradiol. Twenty-eight percent to 73% of estriol was lost over the 14 days treatment period. Estrone and 17??-ethinylestradiol exhibited slower rates of biological transformation under saturated and draining conditions. Half-lives for estrone ranged between 27.5 and 56.8 days with loss of at most 21%. 17??-ethinylestradiol exhibited half-lives of 22.6?C207 days. Half-life data for ibuprofen ranged from 30.4 to 1,706.4 days in this experiment. Losses of up to 17% were observed in draining soils. Triclosan loss was at most 10%, and half-lives were 70.9?C398.8 days. In all cases, soils that were draining from saturated conditions exhibited faster degradation rates than soils that remained saturated. Prior exposure of the soil to effluent did not always result in higher biological degradation rates.  相似文献   

7.
The behavior of glyphosate, extracted from four soils using aqueous triethylamine, was investigated at two temperatures. For each soil, and at both temperatures, there was a marked loss in the amount of extractable glyphosate immediately after addition of the herbicide to soil. This rapid loss of glyphosate was ascribed to adsorption of the herbicide into a nonextractable form. For three of the four soils used when incubated at 25 degrees C, the rates of loss of extractable glyphosate were similar to previously measured rates of degradation of this herbicide in these soils. However, loss of extractable glyphosate from the Culgoa clay loam was due not only to substrate degradation but also to slow sorption of glyphosate into the nonextractable form in this soil over the experimental period. For the Rutherglen and Walpeup soils, when incubated at 10 degrees C, the rates of loss of extractable glyphosate were half of the previously measured rate of degradation of this herbicide in these soils. However, there was no measured loss of extractable glyphosate from the Wimmera clay. As previous work has shown glyphosate to decompose readily in these soils at this temperature, these findings suggest that desorption of glyphosate may occur at a rate greater than degradation at this temperature and, hence, that temperature may play a pivotal role in sorption processes. Investigations with these soils when sterilized by gamma-irradiation showed that for the Walpeup, Wimmera, and Rutherglen soils, sorption was complete soon after the addition of the herbicide; however, for the Culgoa soil, further adsorption occurred over the entire experimental period.  相似文献   

8.
Flumioxazin is an herbicide registered for use in soybean and peanut. However, few published papers concerning the soil persistence of flumioxazin are available. Therefore, laboratory studies were initiated to determine the half-life (t(1/2)) of flumioxazin in Greenville sandy clay loam and Tifton loamy sand soils when incubated at 15 and 25 degrees C. Results indicated that temperature had little effect on flumioxazin persistence. The t(1/2) for the Greenville soil was 17.9 and 16.0 days while the Tifton soil was 13.6 and 12.9 days, at 15 and 25 degrees C, respectively. These data correspond to the greater clay content of the Greenville soil (32%) as compared to the Tifton soil (2%). Therefore, the Greenville soil had greater soil adsorption and less flumioxazin was generally available to be degraded by soil microorganisms. In soils that were heat treated to reduce microbe populations, 99% of initial flumioxazin was accounted for after 16 days. Mineralization of flumioxazin, measured as 14CO2 evolution, was also greater in the Tifton soil (2.2% after 64 days) than in the Greenville soil (2.0% after 64 days). From these data, it was concluded that microbes were the most influential factor concerning the degradation of flumioxazin.  相似文献   

9.
The effect storage had on the microbial biomass in two soils (Trevino and Fargo) was compared to the effect storage had on each soil's capacity to degrade metsulfuron-methyl. Soils were collected from the field and used fresh (<3 weeks old) or stored at 20 and 4 degrees C for 3 or 6 months. The phospholipid fatty acid content of the soils was used to monitor changes in the microbial biomass during storage and incubation in a flow-through apparatus. In both soils, [phenyl-U-14C]metsulfuron-methyl was used to monitor changes in the route and rate of degradation along with 14CO2 evolution (mineralization). Total microbial biomasses in both soils were significantly reduced for soils incubated in the flow-through apparatus, whereas only the Trevino soil's microbial biomass was significantly reduced as a result of storage. The microbial communities of both soils were significantly different as a result of storage as shown by discriminant analysis. In both soils, degradation rate, pathway of degradation, and mineralization of metsulfuron-methyl were significantly affected by storage compared to fresh soil. The half-life of metsulfuron-methyl increased significantly (P < 0.05) in the Trevino soil from 45 days (fresh) to 63 days (stored soil), whereas in the Fargo soil half-lives increased significantly (P < 0.05) from 23 days (fresh) to 29 days (soils stored for 6 months). In both soils, mineralization of [14C]metsulfuron-methyl was significantly (P < 0.05) higher in fresh soils compared to stored soils. The degradation pathways of metsulfuron-methyl changed with storage as evidenced by the loss of formation of one biologically derived metabolite (degradate) in stored soils compared to fresh soils.  相似文献   

10.
Biological degradation rates of estrogen compounds and common pharmaceutical and personal care products (PPCPs) were examined in soils with a long history of exposure to these compounds through wastewater effluent and in soil not previously exposed. Biological degradation rates over 14 days were compared under aerobic and anaerobic conditions. Estrogen compounds including estrone, 17??-estradiol, estriol, and 17??-ethinylestradiol exhibited rapid degradation by soil microorganisms in both aerobic and anaerobic conditions. Rapid degradation rates for estrone, estriol, and 17??-ethinylestradiol occurred in pre-exposed soil under aerobic conditions; half-lives calculated under these conditions were 0.6, 0.7, and 0.8 day, respectively. Unexposed soil showed similar or slightly longer half-lives than pre-exposed soil under aerobic conditions. The exception was 17??-estradiol; in all treatments, degradation in unexposed soil resulted in a shorter half-life (2.1 versus 2.3 days). Anaerobic soils exhibited high biological degradation of estrogens as well. Half-lives of all estrogens ranged from 0.7 to 6.3 days in anaerobic soils. Triclosan degraded faster under aerobic conditions with half-lives of 5.9 and 8.9 days in exposed and unexposed soil. Under anaerobic conditions, triclosan half-lives were 15.3 days in unexposed and 28.8 days in exposed soil. Ibuprofen showed the least propensity toward biological degradation than other chemicals tested. Biological degradation of ibuprofen was only observed in unexposed soil; a half-life of 41.2 days was determined under anaerobic conditions and 121.9 days under aerobic conditions. Interestingly, unexposed soil exhibited a greater ability under anaerobic conditions to biologically degrade tested compounds than previously exposed soil.  相似文献   

11.
Biobeds can be used to intercept pesticide-contaminated runoff from the mixing/washdown area, creating optimum conditions for sorption and biodegradation such that the amount of pesticide reaching adjacent water bodies is significantly reduced. The biobed is built on the farm using locally available materials, which include, straw, compost, and topsoil. The topsoil acts as the inoculum for the system and is likely to vary in terms of its physical, chemical, and microbiological characteristics from one farm to another. This study therefore investigated the effects of using different soil types on the degradation and leaching potential from biobeds. Three contrasting topsoils were investigated. Leaching studies were performed using isoproturon, dimethoate, and mecoprop-P, which were applied at simulated disposal rates to 1.5 m deep biobeds. Annual average concentrations were similar for each soil type with leaching losses of even the most mobile (Koc = 12-25) pesticide <1.64% of the applied dose. Greater than 98% of the retained pesticides were degraded in all matrices. Degradation studies investigated the persistence of individual pesticides and pesticide mixtures in the different matrices. DT50 values for isoproturon, chlorothalonil, mecoprop-P, and metsulfuron-methyl applied at 4 times the maximum approved rate were similar across the biomix types and were all less than or equal to reported DT50 values for soil treated at approved rates. When applied as a mixture, DT50 values in each biomix increased, indicating that interactions between pesticides are possible. However, DT90 values of <167 days were obtained in all circumstances, indicating a negligible risk of accumulation. Studies therefore indicate that substrate will have little impact on biobed performance so it should be possible to use local soils in the construction process.  相似文献   

12.
采用长期定位施肥试验土壤（轻壤质黄潮土），研究不同施肥条件下，氯氰菊酯降解变化和对土壤酶活性的影响。结果表明，不同的施肥处理对土壤中氯氰菊酯的降解行为有显著影响，长期施用氮肥，土壤中速效氮含量升高，对氯氰菊酯降解有抑制作用；施用磷肥则促进降解；施用有机肥在提高土壤有机质含量的同时，虽加速了氯氰菊酯降解，但降解延滞期和残留期有所增加。氯氰菊酯在土壤中的降解遵循一级动力学方程，降解半衰期为10．13d（PK）～14．58d（NK）。土壤中加入氯氰菊酯后，脱氢酶、脲酶活性有所升高，施肥处理不同，升高幅度也不一样．均达显著水平。磷酸酶活性变化在不同施肥处理中，表现不一样。培养26d左右，土壤酶活性大多都能恢复到初始水平。研究土壤中农药残留与施肥、土壤酶活性的关系，对于实现农业可持续发展具有重要意义。  相似文献   

13.
Ethion, a highly persistent insecticide in soil, is extensively used in tea cultivation in the tropics. The studies on the environmental impact of ethion in tea soil ecosystems are scanty. Silty loam and sandy loam soils from tea fields of Dooars (Typic Uderthents) and Hill (Typic Dystrudepts), respectively, were investigated for the degradation and effect of ethion application on soil microbial and biochemical variables under controlled laboratory conditions. Ethion degraded faster in the Hill soil than in the Dooars soil. Higher temperature (30°C) aided in faster degradation due to the increased microbial activity in the soils. Ethion application at field rate (FR) had lower half-lives (70 days at 20°C and 42.3 days at 30°C for Dooars soil; 65.4 days at 20°C and 39 days at 30°C for Hill soil) than at ten times FR (10FR; 75.2 days at 20°C and 44.2 days at 30°C for Dooars soil; 70 days at 20°C and 41.8 days at 30°C for Hill soil). Soil microbial biomass carbon, ergosterol content, fluorescein diacetate hydrolyzing and β-glucosidase activities declined in all the treatment combinations up to day 60 for both FR and 10FR doses at 20°C, irrespective of the soil types. At 30°C, the decreasing trend was observed up to day 30 for both the soils. The toxicological effect of ethion on microbiological and biochemical parameters persisted till their corresponding half-lives. The microbial metabolic quotient and microbial respiration quotient were altered, but was short-lived, indicating ethion induced disturbances. The recovery of the depressive action at 10FR ethion spiking on the studied variables was of slightly longer duration than noticed at FR application, although the depressive effect was overcoming after the respective half-lives of ethion. The microbial and biochemical soil parameters were negatively correlated with application of ethion up to day 60 of incubation.  相似文献   

14.
Degradation of ZJ0273, a recently developed pyrimidynyloxybenzoic‐based herbicide, was investigated in five different soils under aerobic conditions. ZJ0273 degradation rate was strongly affected by soil physico‐chemical characteristics and the inoculation of ZJ0273‐degrading bacteria. Greater organic matter (OM) content, neutral pH and inoculation of ZJ0273‐degrading bacteria can increase degradation rate and decrease the half‐life value (DT50). At 30°C the biodegradation rate of ZJ0273 reached 41–85% in natural (unsterilized) soils. It ranged from 69 to 96% at 90 days after treatment (DAT) in five different types of soils after re‐inoculation of Amycolatopsis sp. M3‐1 and DT50 decreased by 34 , 81, 16, 20 and 32 days, respectively, in soils S1, S2, S3, S4 and S5. Furthermore, using the six metabolites (M1–M6) identified six metabolites (M1–M6) by liquid chromatography‐mass spectrometry (LC‐MS) and their behaviour, a biodegradation pathway of ZJ0273 in soils was proposed. New metabolites, M5 and M6, were found in soils. Biodegradation of ZJ0273 involved continuous biocatalytic reactions, such as de‐estering, hydrolysis, acylation, C‐N cleavage, de‐methyl and ether cleavage reactions. Finally, ZJ0273 was bio‐transformed into M4 and M6, which could be degraded and oxidized into CO2 and H2O through the tricarboxylic acid (TCA) cycle.  相似文献   

15.
Glyphosate is a commonly used herbicide in grassland soils and microorganisms control its degradation. We introduce the concept of using the degradation rate as an indicator for ecosystem health. Testing this concept, we used soils with a long history of heavy metal pollution (Cu, Pb, and Zn). We hypothesized lower degradation rates in metal-polluted compared to less polluted soils. The degradation rates were measured by repeated measurements of the parent compound in spiked soil-water slurries incubated at 20 °C over 21 days. Average rates showed no differences comparing among soils. We observed a positive correlation between glyphosate degradation rates and soil metal pollution. Therefore, we concluded that the expected impact of the metals on the bacteria responsible for the herbicide degradation was not established. We discuss the potential influence on biological degradation rates of soil pH and adsorption and implications using the concept of the soil health indicator.  相似文献   

16.
The characteristics of isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] metabolism were investigated in soil taken from two transects within a single field. Along transect 1, complete degradation of the parent compound occurred within 18 days, and over 40% of ring C had been metabolised after 65 days. In these soils, both side chain and ring metabolism had a short lag phase, followed by a period of rapid degradation. Along transect 2, the rate of side chain metabolism was highly variable, and 20% of ring C had been metabolised after 65 days. The dynamics of isoproturon ring C metabolism were typical of cometabolic degradation, even at sites in which enhanced side chain metabolism occurred. Isoproturon degrading organisms were found in similar numbers in soil from the two transects prior to isoproturon application. In soils from transect 1, there was considerable proliferation of degrader organisms during the lag phase, in which 40% of the isoproturon was degraded. In most soils from transect 2, there had been no proliferation of isoproturon metabolising organisms at the point of 40% metabolism. Before enhanced degradation could develop, there was clearly a requirement for the isoproturon metabolising community to reach a threshold size. Immobilisation of isoproturon ring C into the microbial biomass and formation of bound residues was lower in soil from transect 2 relative to soil from transect 1. We conclude that the in-field spatial heterogeneity of isoproturon side chain and ring metabolism, the formation of bound residues and the immobilisation of pesticide residues in the biomass, results from variation in the development and significance of growth linked and cometabolic degradation.  相似文献   

17.
Sorption and degradation rates of hexazinone and simazine on soil were determined in a sandy loam soil incubated, during 44 days, at 25 degrees C with moisture contents ranging from 4% to 18%. Herbicide levels in soil solution were also measured, after extraction of this solution by a centrifugation method. All experiments were conducted with treated soil in plastic columns, and the results showed that this method is suitable for the simultaneous study of pesticide sorption and degradation in soil at different environmental conditions. In general, sorption of both herbicides was higher for aged herbicide residues compared to recently applied herbicides, and soil subjected to drying and rewetting cycles had the highest sorption values. K(f) values ranged from 0.5 to 1.2 for simazine and from 0.2 to 0.4 for hexazinone. Degradation rates increased with soil moisture content for both herbicides, and drying-rewetting of soil yielded degradation rates slower than that obtained at 10% soil moisture content. Hexazinone concentration in soil solution decreased with incubation time faster than simazine.  相似文献   

18.
在对土霉素（OTC）、四环素（TC）和金霉素（CTC）3 种四环素类抗生素的高效液相色谱（HPLC）检测分析方法以及在土壤和堆肥中的提取方法进行改进和优化的基础上,采用该方法进行了 3 种抗生素在土壤中的降解试验。结果表明,选用 Agilent Eclipse XDB-C8（4.6150 mm,5 m）色谱柱,以 0.01 mol/L草酸/乙腈/甲醇（79/10.5/10.5,v/v/v）为流动相,紫外检测波长 268 nm,流速 1.0 mL/min,进样量 5 L,采用外标法定量,可使 3 种四环素类抗生素在 20 min 内全部洗脱并达到基线分离; 在 0~10 mg/L 范围内,抗生素浓度与峰面积呈显著的线性关系,相关系数（r）均 0.999。土壤和堆肥样品中的 OTC、TC 和 CTC可用1 mol/L NaCl/0.5 mol/L 草酸/乙醇（25/25/50,v/v/v）混合溶液提取,其回收率在 76.0%~92.5% 之间。加入到土壤中的抗生素在 25℃下避光培养 49 d 后,在壤土和红土中的降解率分别是 67%~72% 和 36%~46%,对应的半衰期分别为 2630 d 和 4675 d,说明抗生素在壤土中比红土中容易降解。此外,3种抗生素在壤土中的半衰期没有显著性差异,而在红土中 CTC 和 TC 的降解速率显著高于 OTC。  相似文献   

19.
研究了种植紫花苜蓿 (MedicagosativaL )在接种和不接种菌根真菌 (GlomuscaledoniumL )情况下对土壤中苯并 [a]芘 (B[a]P)的降解动态。历经 90天的温室盆栽试验表明 ,较高浓度 (10 0mgkg-1)B[a]P能降低菌根真菌对植物根的侵染率。种植紫花苜蓿和接种菌根真菌能促进土壤中可提取态B[a]P的降解 ,在接种情况下 ,有植物时对三种浓度 (1mgkg-1,10mgkg-1,10 0mgkg-1)B[a]P的降解率分别达 86 2 %、86 6 %、5 7 0 % ;而没有植物时B[a]P的降解率为 5 3 5 %、5 3 0 %、33 0 %。不接菌根真菌时的降解率比接菌根真菌的低得多 ,不接种菌根真菌时 ,有植物的B[a]P降解率分别达 75 9%、77 7%、5 3 4 % ;而不种植物的降解率分别为 5 4 9%、5 2 6 %、34 1% ,低、中浓度 (1mgkg-1,10mgkg-1)两处理的降解率明显地高于高浓度处理(p <0 0 5 )。B[a]P添加对土壤中多酚氧化酶活性有较大的影响 ,特别是高浓度B[a]P处理土壤的酶活性明显地低于其它三个处理 ,接种菌根真菌能够提高土壤中的酶活性 ,从而促进了土壤中B[a]P的降解。  相似文献   

20.
S. PAL  P. MARSCHNER 《土壤圈》2016,26(5):643-651
Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A loamy sandy soil(7% clay) was amended with a clay-rich subsoil(73% clay) at low to high rates to achieve soil mixtures of 12%, 22%, and 30% clay, as compared to a control(sandy soil alone) with no clay addition. The sandy-clay soil mixtures were amended with finely ground plant residues at 10 g kg~(-1): mature wheat(Triticum aestivum L.) straw with a C/N ratio of 68, mature faba bean(Vicia faba L.) straw with a C/N ratio of 39, or their mixtures with different proportions(0%–100%, weight percentage) of each straw. Soil respiration was measured over days 0–45 and microbial biomass C(MBC), available N, and p H on days 0, 15, 30, and 45. Cumulative respiration was not clearly related to the C/N ratio of the residues or their mixtures, but C use efficiency(cumulative respiration per unit of MBC on day 15) was greater with faba bean than with wheat and the differences among the residue mixtures were smaller at the highest clay addition rate. The MBC concentration was lowest in sole wheat and higher in residue mixtures with 50% of wheat and faba bean in the mixture or more faba bean. Soil N availability and soil p H were lower for the soil mixtures of 22% and 30% clay compared to the sandy soil alone. It could be concluded that soil cumulative respiration and MBC concentration were mainly influenced by residue addition, whereas available N and p H were influenced by clay addition to the sandy soil studied.  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