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1.
Retention of the cationic herbicides paraquat (PQ), diquat (DQ), and difenzoquat (DFQ) in two vineyard soils with a different management history and retention capacity was examined. The influence of copper on the ability of the soils to retain the herbicides was determined by comparing the results of adsorption and desorption tests on untreated and Cu-enriched soil samples, and also on soils that were previously treated with EDTA to extract native copper. The three herbicides were strongly adsorbed by both soils. Soil 1 exhibited linear adsorption isotherms for PQ and DFQ with partition coefficients, KD, of 1.28 x 103 and 1.37 x 103 L kg-1, respectively, and a Freundlich-type isotherm for DQ with a linearized partition coefficient, KD*, of 1.01 x 103 L kg-1. On the other hand, soil 2 exhibited curved isotherms and smaller KD* values (viz. 106, 418, and 28 L kg-1 for PQ, DQ, and DFQ, respectively). Using EDTA to extract copper from the soils released new sites for the herbicides to bind. The three herbicides exhibited strong hysteresis in the adsorption-desorption process. Extracting copper decreased the percent desorption of PQ and DQ; on the other hand, it decreased the affinity of DFQ for the resulting vacant adsorption sites. Similarly, competitive adsorption tests with copper and the herbicides revealed that the metal was only capable of displacing DFQ from adsorption sites. The behavior of this herbicide in the soils was consistent with a specific adsorption model. The disparate behavior of the two soils toward the herbicides was a result of the adsorption sites in soil 1 being less extensively occupied than those of soil 2 in the adsorption tests. The effect of copper on the adsorption of DFQ in the two soils was acceptably reproduced by an adsorption model involving Coulombic and specific sorption with competition from the metal.  相似文献   

2.
Atrazine and metolachlor are commonly detected in surface water bodies in southern Louisiana. These herbicides are frequently applied in combination to corn, and atrazine to sugarcane, in this region. A study was conducted on the runoff of atrazine and metolachlor from 0.21 ha plots planted to corn on Commerce silt loam, a Mississippi River alluvial soil. The study, carried out over a three-year period characterized by rainfall close to the 30-year average, provided data on persistence in the surface soil (top 2.5 cm layer) and in the runoff active zone of the soil, as measured by decrease in runoff concentrations with time after application. Regression equations were developed that allow an estimate of the runoff extraction coefficients for each herbicide. Atrazine showed soil half-lives in the range 10.5-17.3 days, and metolachlor exhibited half-lives from 15.8-28.0 days. Concentrations in successive runoff events declined much faster than those in the surface soil layer: Atrazine runoff concentrations decreased over successive runoff events with a half-life from 0.6 to 5.7 days, and metolachlor in runoff was characterized by half-lives of 0.6-6.4 days. That is, half-lives of the two herbicides in the runoff-active zone were one-tenth to one-half as long as the respective half-lives in the surface soil layer. Within years, the half-lives of these herbicides in the runoff active zone varied from two-thirds longer for metolachlor in 1996 to one-fifth longer for atrazine in 1995. The equations relating runoff concentrations of atrazine and metolachlor to soil concentrations contain extraction coefficients of 0.009. Losses in runoff for atrazine were 5.2-10.8% of applied, and for metolachlor they were 3.7-8.0%; atrazine losses in runoff were 20-40% higher than those for metolachlor. These relatively high percent of application losses indicate the importance of practices that reduce runoff of these chemicals from alluvial soils of southern Louisiana.  相似文献   

3.
The addition of organic amendments to soil increases soil organic matter content and stimulates soil microbial activity. Thus, processes affecting herbicide fate in the soil should be affected. The objective of this work was to investigate the effect of olive oil production industry organic waste (alperujo) on soil sorption-desorption, degradation, and leaching of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and terbuthylazine [N2-tert-butyl-6-chloro-N4-ethyl-1,3,5-triazine-2,4-diamine], two herbicides widely used in olive crops. The soils used in this study were a sandy soil and a silty clay soil from two different olive groves. The sandy soil was amended in the laboratory with fresh (uncomposted) alperujo at the rate of 10% w/w, and the silty clay soil was amended in the field with fresh alperujo at the rate of 256 kg per tree during 4 years and in the laboratory with fresh or composted alperujo. Sorption of both herbicides increased in laboratory-amended soils as compared to unamended or field-amended soils, and this process was less reversible in laboratory-amended soils, except for diuron in amended sandy soil. Addition of alperujo to soils increased half-lives of the herbicides in most of the soils. Diuron and terbuthylazine leached through unamended sandy soil, but no herbicide was detected in laboratory-amended soil. Diuron did not leach through amended or unamended silty clay soil, whereas small amounts of terbuthylazine were detected in leachates from unamended soil. Despite their higher sorption capacity, greater amounts of terbuthylazine were found in the leachates from amended silty clay soils. The amounts of dissolved organic matter from alperujo and the degree of humification can affect sorption, degradation, and leaching of these two classes of herbicides in soils. It appears that adding alperujo to soil would not have adverse impacts on the behavior of herbicides in olive production.  相似文献   

4.
The adsorption of herbicides on soil colloids is a major factor determining their mobility, persistence, and activity in soils. Solvent extraction could be a viable option for removing sorbed contaminants in soils. This study evaluated the extractability of three herbicides: 2,4 dichlorophenoxy-acetic acid (2,4-D), 4-chloro-2-methylphenoxypropanoic acid (mecoprop acid or MCPP), and 3,6-dichloro-2-methoxybenzoic acid (dicamba). Three solvents (water, methanol, and iso-propanol) and three methods of extraction (column, batch, and soxhlet) were compared for their efficiencies in removing the herbicides from three soils (loamy sand, silt loam, and silty clay). Both linear and non-linear Freundlich isotherms were used to predict sorption intensity of herbicides on soils subjected to various extraction methods and conditions. High Kdand Kfr, and low N values were obtained for all herbicides in silty clay soil by batch extraction. Methanol was the best solvent removing approximately 97% of all added herbicides from the loamy sand either by column or soxhlet extraction method. Isopropanol ranked second by removing over 90% of all herbicides by soxhelet extraction from all three soils. However, water was ineffective in removing herbicides from any of the soils using any of the three extracting procedures used in this study. In general, the extent of herbicide removal depended on soil type, herbicide concentration, extraction procedure, solvent type and amount, and extraction time.  相似文献   

5.
Amendments are frequently added to agricultural soils to increase organic matter content. In this study, we examined the influence of alperujo, an olive oil mill waste, on the availability of two triazine herbicides, terbuthylazine and atrazine, in two different sandy soils, one from Sevilla, Spain, and the other from Minnesota. The effect of aging on herbicide sorption and bioavailability was also studied. Soils were amended with alperujo at a rate of 3-5% (w:w) in laboratory studies. Apparent sorption coefficients for the triazine herbicides were calculated as the ratio of the concentrations of each herbicide sequentially extracted with water, followed by aqueous methanol, at each sampling time. These data showed greater sorption of terbuthylazine and atrazine in amended soils as compared to nonamended soils, and an increase in the amount of herbicide sorbed with increasing aging time in nonamended soils. The triazine-mineralizing bacterium Pseudomonas sp. strain ADP was used to characterize triazine bioavailability. Less mineralization of the herbicides by Pseudomonas sp. strain ADP was observed in soils amended with alperujo, as compared to the unamended soils, and, despite the increase in sorption with aging in unamended soils, herbicide mineralization also increased in this case. This has been attributed to Pseudomonas sp. strain ADP first using alperujo as a more readily available source of N as compared to the parent triazines. In summary, addition of alperujo to the soils studied was shown to increase triazine herbicides sorption and hence to reduce its availability and potential to leach.  相似文献   

6.
The environmental impacts of herbicides on desirable plants and the soil biota are of public concern. The surfactants that are often used with herbicides are also under scrutiny as potentially harmful to soil biological systems. To address these concerns, we used two soils, a silt loam and a silty, clay loam from south central Missouri, to investigate the impacts of herbicides and surfactants on soil microbial communities using phospholipid fatty acid (PLFA) analysis. The surfactants used in this study were alkylphenol ethoxylate plus alcohol ethoxylate (Activator 90), polyethoxylate (Agri-Dex), and a blend of ammonium sulfate, drift reduction/deposition polymers and anti-foam agent (Thrust). The herbicides were glyphosate, atrazine and bentazon. Surfactants and herbicides were applied to soils at label rate, either alone or combined, to 4000 g soil per pot. The two soils differed in history, texture, some chemical characteristics and several microbial community characteristics. A few of the chemicals altered some of the components of the microbial community after only one application of the chemical at field-rate. The Cole County, MO silt loam showed larger changes in the microbial community with application of treatments. For the Boone County, MO silty clay loam, Activator 90, Agri-Dex and bentazon treatments increased microbial biomass determined by PLFA; Thrust decreased PLFA markers, bacteria to fungi ratio; and Agri-Dex at both rates decreased monounsaturated fatty acids. Changes in the microbial community due to herbicides or surfactants were minimal in this study of a single application of these chemicals, but could be indicators of potential long-term effects. Long-term studies are needed to determine the changes in the microbial community after several years of annual applications of herbicides and surfactants on a wide array of soil types and management practices.  相似文献   

7.
Surfactants in herbicide formulations eventually enter soil and may disrupt various processes. Research examined effects on nutrient uptake in corn caused by surfactants, herbicides, and surfactant-herbicide combinations applied to silt loam and silty clay loam soils in the greenhouse. Surfactants evaluated were Activator 90, Agri-Dex, and Thrust; herbicides were glyphosate, atrazine, and bentazon. Corn was planted in fertilized soils with moisture content maintained for optimum growth. Foliage (V8 growth stage) was collected for elemental analyses. Nutrient uptake differed with soil texture. Nutrient uptake from silty clay loam was more affected by surfactants and/or herbicides than in silt loam. Potassium uptake was significantly (P = 0.05) decreased in silt loam only by Thrust but uptake of phosphorus (P), potassium (K) calcium (Ca), sulfur (S), copper (Cu), and zinc (Zn) decreased by ≤30% in silty clay loam treated with surfactants. Surfactants and/or herbicides may interact with soil texture to affect nutrient uptake. Long-term field studies to validate changes in nutrient uptake and grain yields after annual applications of surfactants plus herbicides are needed.  相似文献   

8.
Experiments were conducted to investigate the impact of commonly used herbicides and surfactants on the activity of acid phosphatase, β-glucosidase, arylsulfatase, β-glucosaminidase, and dehydrogenase, using two soils (silt loam and silty clay loam) from Mid-Missouri, USA. The surfactants used in this study were alkylphenol ethoxylate + alcohol ethoxylate (ACTIVATOR 90), polyethoxylate (Agri-Dex®) and a blend of ammonium sulfate, drift reduction/deposition polymers, and an antifoam agent (THRUST®). The herbicides were glyphosate, atrazine, and bentazon. Surfactants and herbicides were applied to soils at the label rate, either alone or combined. In general, enzyme activity was enhanced more in silt loam soil than in silty clay loam soil. Acid phosphatase displayed the greatest amount of enzymatic activity within soils; dehydrogenase displayed the most inhibition, whilst β-glucosidase and β-glucosaminidase fluctuated based on treatment. ACTIVATOR 90 appeared to have the most inhibitory effect on enzymatic activity within soils compared to the control.  相似文献   

9.
河南省典型淋溶土土系划分研究   总被引：6，自引：0，他引：6  
在河南省选取8个典型土壤剖面,对其进行景观特征、剖面形态学特征的描述及其理化性质的分析,并确定其在土壤系统分类(Chinese Soil Taxonomy)中的归属,结果表明,供试土壤归属于壤质混合型石灰性温性普通简育干润淋溶土、壤质混合型非酸性温性斑纹简育湿润淋溶土、黏壤质混合型温性斑纹钙积干润淋溶土、黏壤质混合型温性普通钙积干润淋溶土、壤质混合型石灰性温性普通简育湿润淋溶土和壤质混合型非酸性温性普通简育湿润淋溶土等6个土族;并在此土族基础上,根据土系划分规则和河南地区淋溶土诊断特征及构型特征,尝试提出"土系对比检索逻辑图"以阐述土系参比划分的逻辑过程。通过对比,可将8个典型土壤剖面划分为7个土系:汤阴系、汲水系、神沟系、尚庄系、侯集系、枣林系和尚店系。  相似文献   

10.
The degradation of 2, 4-D, 2, 4, 5-T, and picloram in two Philippine soils was investigated under upland and flooded (submerged) conditions. These herbicides degraded in both upland and flooded Maahas clay and Luisiana clay soils. The rate of degradation of the herbicides was more rapid in the Maahas clay soil than in the Luisiana clay soil. Among the three herbicides, 2, 4-D was the least persistent and picloram was the most persistent in both soils under both submerged and upland conditions. 2, 4, 5-T degraded more actively in the two Philippine soils in this study than studies previously reported in the available literature. The fact that both the 2, 4-D and 2, 4, 5-T did not degrade in sterilized soils during the incubation period suggests that the degradation is due to the microbial activity in the soils.  相似文献   

11.
Influence of herbicides on nitrogen fixation and respiration activity of microorganisms in arable soils The influence of pesticides on nitrogen fixation (acetylene reduction test) as well on respiration activity was determined in model experiments. The following soils were used: Chernozem from loess (Boroll), Luvisol from loess (Boralfs), Rendsina (Lithic Rendoll), Pelosol (Fine textured Cambisol) and Humic Podzol (Humod). The tested soils differed considerably in both parameters. The rendsina showed remarkably low fixation rates whereas the podsol reduced acetylene only at higher water contents. The soil herbicides chlortoluron, terbutryne, metabenzthiazuron and chloridazon did not affect the course and the magnitude of the tested parameters even not at higher doses. Only the leaf herbicide dinosebacetate revealed a distinct inhibition of nitrogenase activity in the podsol and in the luvisol from loess. The fungicide carbendazime caused a strong stimulation of the nitrogenase activity in all soils. The respiration activity could not been influenced significantly.  相似文献   

12.
The influence of 5 and 50 mg active ingredient kg-1 soil of nine preemergence and nine postemergence herbicides on transformations of urea N in soil was studied in samples of two coarse-textured and two fine-textured soils incubated aerobically at 20°C. The effects of each herbicide on soil urea transformations was measured by determining the amounts of urea hydrolyzed and the amounts of NO inf3 sup- and NO inf2 sup- produced at various times after treatment with urea. Applied at the rate of 5 mg active ingredient kg-1 soil, none of the herbicides retarded urea hydrolysis in the four soils used, but four of the postemergence herbicides (acifluorfen, diclofop methyl, fenoxaprop ethyl) retarded urea hydrolysis in the two coarse-textured soils. All the herbicides tested except siduron retarded nitrification in the two coarse-textured soils when applied at 50 mg of urea N active ingredient kg-1 soil, and fenoxaprop ethyl and tridiphane markedly retarded nitrification of urea N in all four of the soils when applied at this rate. One-way analysis of variance and correlation analyses indicated that the inhibitory effects of the 18 herbicides tested on nitrification of urea N in soil increased with a decrease in the organic-matter content and an increase in the sand content of the soil. Present address: Department of Soil and Environmental Sciences, University of California, Riverside, CA 92521, USA  相似文献   

13.
Adequate silicon nutrition in plants has shown positive effects on the growth and yield of the crop and physico-chemical properties of the soil. Hence, this study was initiated to survey the plant-available silicon in the agricultural soils of different parishes of Louisiana. Soil samples were collected from 212 representative agricultural fields of 27 agrarian parishes of Louisiana. Poor correlations between deionized water, calcium chloride, and other extractants suggest that the unbuffered calcium chloride extraction may reflect only a transient status of soil soluble silicon similar to deionized water extraction procedure. Also, acetic acid-2 extraction procedure may reflect the net effects of the sorption/desorption reactions by extracting the readily as well as the slowly releasable silicon that control solubility, thus giving a true measure of current availability. Compared to the previously established critical soil silicon levels, several agricultural fields of Louisiana were deemed to be low in plant-available silicon.  相似文献   

14.
Effects of diatomite on soil physical properties   总被引：1，自引：0，他引：1  
Organic and inorganic soil amendments are commonly added to soil for improving its physical and chemical characteristics which promote plant growth. Although many inorganic amendments are extensively used for this purpose, diatomite (DE) is not commonly used. This study was conducted to determine effects of diatomite applications (10, 20, and 30% v/v) on physical characteristics of soils with different textures (Sandy Loam, Loam, and Clay), under laboratory conditions. The results indicated that diatomite application protects large aggregate (> 6.4 mm) formation in clay-textured soils, however it reduced the mean weight diameter in sand-textured soil. 30% diatomite reduced mean weight diameter in sand-textured soils from 1.74 to 1.49 mm. Diatomite applications significantly increased aggregate stability of all the experimental soils in all aggregate size fractions. In overall, aggregate stability increased from 28.04% to 45.70% with the application rate of 30%. Diatomite application also significantly increased soil moisture content at field capacity in SL textured soil. 30% diatomite increased field capacity in sand-textured soil in the percent of 43.78 as compared with control. Therefore it is suggested that diatomite may be considered as a soil amendment agent for improving soil physical characteristics. However, its effectiveness in enhancing soil properties depends on initial soil factors and texture. Moreover, since its protective effect against large aggregate (> 6.4 mm) formation and reducing effect on soil penetration resistance in clay textured soils, diatomite might be an alternative soil amendment agent in soil tillage practices and seedling.  相似文献   

15.
In this study, the potential groundwater pollution of 12 substituted phenylurea herbicides (chlorbromuron, chlorotoluron, diuron, fenuron, fluometuron, isoproturon, linuron, metobromuron, metoxuron, monolinuron, Monuron, and neburon) was investigated under laboratory conditions. For this purpose, leaching studies were conducted using disturbed soil columns filled with two different agricultural soils, one hypercalcic calcisol (HC) and the other endoleptic phaeozem (EP). In the case of the HC, all of the studied herbicides were found in leachates, while for the EP only, chlorbromuron, chlorotoluron, isoproturon, monolinuron, and, especially, fenuron were recovered. For both soils, the groundwater ubiquity score (GUS) index was calculated for each herbicide on the basis of its persistence (as t(1/2)) and mobility (as K(OC)). The half-lives obtained were markedly higher in the EP (217-518 days) than in the HC (71-178 days). As a consequence, higher values of GUS indexes were observed for EP. The ratio of the GUS between the EP and the HC was about 1.3.  相似文献   

16.
Sorption-desorption interactions of pesticides with soil determine the availability of pesticides in soil for transport, plant uptake, and microbial degradation. These interactions are affected by the physical and chemical properties of the pesticide and soil, and for some pesticides, their residence time in the soil. The objective of this study was to characterize sorption-desorption of two sulfonylaminocarbonyltriazolinone herbicides incubated in soils at different soil moisture potentials. The chemicals were incubated in clay loam and loamy sand soils for up to 12 wks at -33 kPa and at water contents equivalent to 50 and 75% of that at -33 kPa. Chemicals were extracted sequentially with 0.01 N CaCl(2) and aqueous acetonitrile, and sorption coefficients were calculated. Sufficient sulfonylaminocarbonyltriazolinone herbicides remained (>40% of that applied) during incubation to allow calculation of sorption coefficients. Aging significantly increased sorption as indicated by increased sorption coefficients. For instance, for sulfonylaminocarbonyltriazolinone remaining after a 12-wk incubation at -33 kPa, K(d) increased by a factor of 4.5 in the clay loam soils and by 6.6 in the loamy sand as compared to freshly treated soils. There was no effect of moisture potential on sorption K(d) values. These data show the importance of characterization of sorption-desorption in aged herbicide residues in soil, particularly in the case of prediction of herbicide transport in soil. In this case, potential transport of sulfonylaminocarbonyltriazolinone herbicides would be over-predicted if freshly treated soil K(d) values were used to predict transport.  相似文献   

17.
Pressurized fluid extraction (PFE) is a new sample extraction method operated at elevated temperatures and pressures with liquid solvents. The use of PFE was investigated for the extraction of four Hawaiian clayey soils fortified with the selected chloroacetanilide and nitrogen heterocyclic herbicides Alachlor, Bromacil, Hexazinone, Metribuzin, and Tebuthiuron. The effects of operation temperature, pressure, flush volume, and static cycles on PFE performance were studied. Water was the most effective modifier of PFE for quantitative recoveries of the five herbicides in soils. The simple extraction method required pretreatment of the soil with 37.6% water and subsequent two-static-cycle extraction with a total of 32 mL of acetone at 1500 psi and 100 degrees C. Average recoveries of Alachlor, Bromacil, Hexazinone, Metribuzin, and Tebuthiuron ranged from 93 to 103% by the water-assisted PFE, compared with only 68-83% recoveries of the corresponding chemicals when no water was used. The extraction time and total organic solvent consumption were reduced from 18 h and 300 mL by Soxhlet to 22 min or less and 80 mL or less of organic solvent by PFE.  相似文献   

18.
Adsorption of the chloroacetanilide herbicides acetochlor, alachlor, metolachlor, and propachlor was determined on soils and soil components, and their structural differences were used to explain their sorptivity orders. On all soils and soil humic acids, adsorption decreased in the order: metolachlor > acetochlor > propachlor > alachlor. On Ca(2+)-saturated montmorillonite, the order changed to metolachlor > acetochlor > alachlor > propachlor. FT-IR differential spectra of herbicide-clay or herbicide-humic acid-clay showed possible formation of hydrogen bonds and charge-transfer bonds between herbicides and adsorbents. The different substitutions and their spatial arrangement in the herbicide molecule were found to affect the relative sorptivity of these herbicides by influencing the reactivity of functional groups participating in these bond interactions. It was further suggested that structural characteristics of pesticides from the same class could be used to improve prediction of pesticide adsorption on soil.  相似文献   

19.
The rates of degradation of the thiocarbamate herbicides diallate and triallate were determined in a single agricultural soil which had been manipulated through C-starvation or C-amendment to contain different quantities of metabolically-active microorganisms. In all soils, and for both herbicides, the rates of degradation were directly related to the microbial biomass. Qualitative differences in the biomasses, roughly evaluated by examination of shifts in fungal populations that could be isolated by the soil washing technique from the C-starved soils, had no apparent influence on the degradation rates.  相似文献   

20.
The impact of two tillage systems, plow tillage (PT) and no-tillage (NT), on microbial activity and the fate of pesticides in the 0–5 cm soil layer were studied. The insecticides carbofuran and diazinon, and the herbicides atrazine and metolachlor were used in the study, which included the incubation and leaching of pesticides from untreated soils and soils in which microorganisms had been inhibited. The mineralization of ring14C labeled pesticides was studied. The study differentiated between biotic and abiotic processes that determine the fate of pesticides in the soil. Higher leaching rates of pesticides from PT soils are explaned by the relative importance of each of these processes. In NT soils, higher microbial populations and activity were associated with higher mineralization rates of atrazine, diazinon and carbofuran. Enhanced transformation rates played an important role in minimizing the leaching of metolachlor and carbofuran from NT soils. The role of abiotic adsorption/retention was important in minimizing the leaching of metolachlor, carbofuran and atrazine from NT soils. The role of fungi and bacteria in the biodegradation process was studied by selective inhibition techniques. Synergistic effects between fungi and bacteria in the degradation of atrazine and diazinon were observed. Carbofuran was also degraded in the soils where fungi were selectively inhibited. Possible mechanisms for enhanced biodegradation and decreased mobility of these pesticides in the upper layer of NT soils are discussed.  相似文献   

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