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1.
Long-term sorption of diuron and isoproturon by a clay loam soil was investigated for nine weeks at two herbicide doses (0·6 or 3 mg kg−1) and two soil moisture contents (35 or 62% w/w, i.e. 3·16 or 1 kPa) by measuring changes in herbicide concentrations in the soil solution sampled by means of glass microfibre filters in presence of sodium azide (200 mg litre−1) which inhibited biodegradation for more than four weeks. After the first day equilibration period, where adsorption mainly occurred (>70% adsorbed), herbicide concentrations in the soil solution decreased (about 50% for diuron; up to 38% for isoproturon) for two weeks but equilibration required about one month. Small amounts of herbicides were sorbed during this process (<10% of the initial (24-h) adsorption). These were similar for both herbicides, although diuron was initially more adsorbed. Values of the partition coefficients of herbicides between soil and soil solution were increased (75–125% for diuron; 29–67% for isoproturon). High soil moisture enhanced sorption speed for both herbicides and increased final sorption only for diuron. Sodium azide inhibited long-term sorption of the more stable diuron and this effect was reversed by low temperature only at the low soil moisture. Sodium azide action might be complex (competition, effect on soil micro-organisms) and was not elucidated.  相似文献   

2.
Studies were conducted to investigate the desorption of diuron and isoproturon adsorbed on undispersed clay loam soil, and the influence of residence time in soil on desorption. The soil was treated at 0·6 or 3 mg kg-1, at 70% moisture content and in the presence of sodium azide to prevent degradation. Measurement of herbicide concentrations in soil solution sampled by means of glass microfibre filters showed that adsorption mainly occurred for one day but long-term sorption proceeded for >two weeks. After a one-day or three-week residence time, soil solution was partly replaced (28%). Measurement of concentrations in solution showed rapid desorption, with equilibria being achieved within 1 h (diuron) or a few hours (isoproturon). After 16 successive desorptions done at 30-min or 12-h intervals, equilibration times tended to be longer. For the short residence time, desorption and long-term sorption could occur simultaneously and equilibration might be faster. Residence time had no significant effect on desorption kinetics nor on the small hysteresis observed for diuron. The aging effect, involving long-term sorption only, decreased the proportion of diuron removed from the soil by successive desorptions but, for isoproturon, desorption frequency and desorption kinetics were more important. © 1997 SCI  相似文献   

3.
BACKGROUND: The diuron‐mineralising ability of the microbiota of a Mediterranean vineyard soil exposed each year to this herbicide was measured. The impact of soil moisture and temperature on this microbial activity was assessed. RESULTS: The soil microbiota was shown to mineralise diuron. This mineralising activity was positively correlated with soil moisture content, being negligible at 5% and more than 30% at 20% soil moisture content. According to a double Gaussian model applied to fit the dataset, the optimum temperature/soil moisture conditions were 27.9 °C/19.3% for maximum mineralisation rate and 21.9 °C/18.3% for maximum percentage mineralisation. The impact of temperature and soil moisture content variations on diuron mineralisation was estimated. A simulated drought period had a suppressive effect on subsequent diuron mineralisation. This drought effect was more marked when higher temperatures were used to dry (40 °C versus 28 °C) or incubate (28 °C versus 20 °C) the soil. The diuron kinetic parameters measured after drought conditions were no longer in accordance with those estimated by the Gaussian model. CONCLUSION: Although soil microbiota can adapt to diuron mineralisation, its activity is strongly dependent on climatic conditions. It suggests that diuron is not rapidly degraded under Mediterranean climate, and that arable Mediterranean soils are likely to accumulate diuron residues. Copyright © 2010 Society of Chemical Industry  相似文献   

4.
We investigated the sorption of five widely used sterol biosynthesis inhibitor fungicides (SBIs: flusilazole, propiconazole, epoxiconazole, fenpropimorph and prochloraz) on a loam soil to assess availability of the SBI residues that are usually left in soil after crop treatments. We focused particularly on the soil moisture content effect, which is poorly documented and is difficult to investigate under realistic conditions. SBI sorption was determined (using diuron as a reference) at two soil moisture contents (26.1% and 46.6% w/w) over a period of 3 weeks using a direct soil solution sampling method. After 24 h of contact, <1% of each applied fungicide was recovered in the soil solution. Despite their low availability in the liquid phase, long‐term sorption was observed for all the compounds, reducing concentrations in the soil solution and doubling the value of the partition coefficient. Significant effects of soil moisture on long‐term sorption were observed, depending on the properties of the chemicals and the sorption mechanisms. Wershaw's humus model (humic substances have a membrane‐like structure) was adapted to fit our observations. Low soil moisture content is assumed to modify the structure of humic substances and to generate hydrophobic surfaces, which favour sorption of hydrophobic fungicides (flusilazole, propiconazole and epoxiconazole). This effect is likely to decrease with the increase in the hydrophobic character of non‐ionic pesticides. It becomes adverse for the more hydrophilic compounds (diuron), which are more sorbed at high soil moisture content due to their higher affinity for hydrophilic regions of humus and to diffusion. Soil moisture effects are more complex when compounds are likely to be protonated in soil. Weakly basic compounds (prochloraz) may partition rapidly into the liquid‐like interior of humus at low soil moisture content but increased diffusion at high soil moisture content may cause additional sorption by ion exchange at colloid surfaces. Strongly basic compounds (fenpropimorph) may essentially adsorb due to ionic interactions with colloids, and their sorption is enhanced at high soil moisture content due to diffusion. Consequences for environmental fate and biological activity of pesticides are briefly discussed. © 2000 Society of Chemical Industry  相似文献   

5.
Retention by a glass fibre filter of the liquid phase of a clay loam soil treated with 14C-diuron provides a novel method for analysis of the herbicide in soil solution. At 26.3% (w/w) soil moisture content, less than 10% of the applied diuron was found in solution, and this percentage decreased slightly with diuron dose. The herbicide was rapidly adsorbed on soil during the first day, but adsorption continued and the concentration of diuron in solution could be further reduced by 36–50% during the following 6 days. Drying the soil after treatment, with possible crystallization of herbicide applied at high doses, tended to fix the solution concentrations. Ethanol (3% v/v) in soil water favoured herbicide dissolution. Increasing soil moisture to 36.3% (w/w) slightly decreased the concentration of the herbicide in solution, but increased the percentage held in solution. Frost and a drying-rewetting cycle had little or no subsequent effect on diuron concentration in soil solution.  相似文献   

6.
Rates of degradation of isoproturon, diuron and metsulfuron-methyl were measured in two soils incubated at two temperatures (5 and 25 °C) with soil moisture at a matric potential of ?5 kPa. Rates of change in soil solution concentration were also measured after extraction of water from the soil using a centrifugation technique. The data, in general, indicated a more rapid rate of decline in aqueous-phase concentrations of herbicide than in total soil concentrations, and hence a progressive increase in partition coefficient in favour of the adsorbed phase. In all of the incubations, however, adsorption of the herbicide was initially less than that measured using standard equilibration techniques that involved shaking with large volumes of solution relative to weights of soil. This may be explained by the ready availability of more adsorption sites in the shaken systems. With isoproturon and diuron, the changes in adsorption with time were similar at the two incubation temperatures. This indicates that the apparent changes in adsorption with these two compounds were not caused by preferential degradation in the soil solution, but by a slow equilibration with adsorption sites. The results with the weakly adsorbed compound metsulfuron-methyl, however, suggested the possibility of preferential degradation in the solution phase because, when degradation was slow, the absolute amounts adsorbed remained constant or increased slightly, even although solution concentrations declined. Implications of the results for pesticide behaviour in soils in the field are discussed.  相似文献   

7.
R. J. HANCE 《Weed Research》1965,5(2):108-114
Summary. A series of adsorption experiments was carried out in order to determine if there was significant competition for adsorption sites between diuron and water. Adsorption of diuron was much lower on hydrophilic materials such as cellulose, chitin, aluminium oxide and a soil mineral fraction than on the less hydrophilic ion exchange resins, lignin, carbon and a soil organic fraction. Methylation with methanolic HCL or diazomethane increased adsorption by the soil organic material, but methylation with dimethyl sulphate did not.
The soil mineral fraction adsorbed considerably more diuron from petroleum spirit solution than from aqueous solution, but the organic matter preparation adsorbed more from aqueous than from petroleum solution.
It was concluded that there is competition between water and diuron for adsorption sites and that diuron is a more effective competitor at soil organic matter surfaces than at soil mineral matter surfaces.
Observations sur la relation entre l'adsorption du diuron el la nature de l'adsorbant  相似文献   

8.
Flumioxazin adsorption kinetics were described using a Greenville sandy clay loam soil. Adsorption kinetics experiments showed that 72% of total herbicide was absorbed after 1 h of continuous shaking and continued to increase to 78% after 72 h. Flumioxazin adsorption was then tested on seven agriculturally important soils throughout the southern USA. Adsorption isotherms for all soils had K(f) (Freundlich distribution coefficient) values that ranged from 8.8 to 0.4, with many near 1.5. Soil organic matter content was the parameter most highly correlated with flumioxazin adsorption (r(2) = 0.95, P < 0.001). Sorption to clay minerals had K(f) values ranging from 50 for bentonite to 4.7 for kaolinite. However, normalizing K(f) for sorbent surface area revealed that aluminum hydroxide (gibbsite) possessed the greatest flumioxazin sorption per unit area. Sorption to anionic exchange resin (K(f) 676) was greater than cationic exchange resin (K(f) 42). Molecular model calculations were performed to elucidate why sorption was greater to anionic exchangers. These calculations indicated that a region of dense electronegativity exists on the 3-dione moiety of the molecule. This would lead to greater flumioxazin sorption by positively charged surface sites. Desorption isotherms from soil exhibited no effect of hysteresis. Desorption from clay minerals was very rapid and flumioxazin in solution was undetectable after three desorption steps. From these data it was concluded that flumioxazin can become readily available in soil solution with increase in soil water content.  相似文献   

9.
Root pullout property of plants was of key importance to the soil reinforcement and the improvement of slope stability. To investigate the influence of soil moisture on root pullout resistance and failure modes in soil reinforcement process, we conducted pullout tests on alfalfa (Medicago sativa L.) roots at five levels (40, 30, 20, 10 and 6 kPa) of soil matric suction, corresponding to respectively 7.84%, 9.66%, 13.02%, 19.35% and 27.06% gravimetric soil moisture contents. Results showed that the maximal root pullout force of M. sativa decreased in a power function with increasing soil moisture content from 7.84% to 27.06%. Root slippage rate increased and breakage rate decreased with increasing soil moisture content. At 9.66% soil moisture content, root slippage rate and breakage rate was 56.41% and 43.58%, respectively. The threshold value of soil moisture content was about 9.00% for alfalfa roots in the loess soil. The maximal pullout force of M. sativa increased with root diameter in a power function. The threshold value of root diameter was 1.15 mm, because root slipping force was greater than root breaking force when diameter >1.15 mm, while diameter ≤1.15 mm, root slipping force tended to be less than root breaking force. No significant difference in pullout forces was observed between slipping roots and breaking roots when they had similar diameters. More easily obtained root tensile force (strength) is suggested to be used in root reinforcement models under the condition that the effect of root diameter is excluded as the pullout force of breaking roots measured in pullout tests is similar to the root tensile force obtained by tensile tests.  相似文献   

10.
耕作方式对黑土耕层孔隙分布和水分特征的影响   总被引：10，自引：0，他引：10  
为探索耕作方式对黑土孔隙度分布和土壤水分特征的影响,以2010年吉林省德惠市中层黑土上进行了9年的田间定位试验小区土壤为研究对象,对免耕和秋翻两种耕作处理下耕层土壤孔隙度和土壤水分特征曲线进行分析。结果表明不同耕作处理对黑土孔隙度影响较大。与秋翻相比,免耕减小了土壤总孔隙度,增大了0～5cm和20～30cm10%～16%的>100μm大孔隙,减小了耕层5～20cm的100～30μm次大孔隙,两种处理不同深度的中孔隙和微孔隙数量相近。不同耕作方式对土壤水分特征的影响存在较大差异,免耕0～5cm和20～30cm的持水能力高于秋翻,而5～20cm表现出相反的变化趋势。实施免耕后,改变了土壤孔隙分布和持水性能,对土壤通气透水和作物根系发育具有重要作用。  相似文献   

11.
The surface run-off of a number of pesticides (diuron, isoproturon, atrazine, alachlor, aclonifen, trifluralin, lindane and simazine), chosen for their range of adsorption behaviours, was studied using simulated rainfall applied to small plots over a short time (one hour). Pesticides were applied together onto bare soil using two different sandy loam soils from Jaillière and Coet Dan sites. The surface run-off samples were collected throughout the running of the event and concentrations of pesticides were measured in both liquid and solid phases. Sorption isotherms for isoproturon and diuron on Jaillière soil as well as eroded particles were measured under equilibrium conditions and compared to their partitioning during surface run-off. At the rainfall intensity used, both soils generated a large load of eroded particles. The average run-off flow rate increased with time for the Jalliére soil, while it remained relatively constant at a higher level for the Coet Dan soil. The concentrations of each pesticide in the run-off samples decreased as the experiments proceeded. The pesticides were classified into two types by their partitioning between the solid and liquid phases. Atrazine, simazine, diuron, isoproturon and alachlor were mainly transported in surface run-off water. By contrast, 90% of trifluralin and aclonifen was adsorbed onto eroded particles. Lindane was intermediate, with a 37% adsorption level. When the contribution of eroded particles was minor, the agrochemical concentrations were inversely proportional to the water flow rate. We have proposed a model that describes the mass of chemicals extracted from soil into surface water during a surface run-off event of a given average duration and flow rate. This model takes into account the dilution of the soil solution and the desorption of chemicals through two parameters called, respectively, the dilution factor and the extraction retardation factor. The desorption kinetic was the limiting step in the surface run-off of weakly sorbed chemicals, such as isoproturon. © 1999 Society of Chemical Industry  相似文献   

12.
有机质对黄土善土持水性与水肥效应的影响   总被引：1，自引：0，他引：1  
黄土高原南部台塬地区有机质对土壤含水量的影响试验研究表明土壤水势相等时,随着土壤有机质含量提高,土壤水分含量增加。土壤水分能量(土壤水势)水平不同,有机质对土壤水分含量的效应值不同,在土壤水势为-40～-50kPa时,有机质对土壤水分含量的效应值最大,土壤水势大于-40kPa小于-50kPa,有机质对土壤水分含量的效应值逐渐变小;在不同土壤含水量条件下,土壤肥力(土壤有机质含量)与水势呈显著负相关,其直线斜率值能更好反映土壤水肥效应状况,并随着土壤含水量的降低,土壤水肥效应值增大,在低肥力土壤中,增施有机肥土壤水肥效应值增加最为显著。  相似文献   

13.
The inhibitory effect of the herbicide diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] on microbial activity in red Latosol soil was followed using microcalorimetry. The activity of the micro-organisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate under 35% controlled humidity at 298.15 (+/- 0.02) K. This activity was determined by power-time curves that were recorded for increasing amounts of diuron, varying from zero to 333.33 micrograms g-1 soil. An increase in the amount of diuron in soil caused a decrease of the original thermal effect, to reach a null value above 333.33 micrograms g-1 of herbicide. The power-time curve showed that the lag-phase period and peak time increased with added herbicide. The decrease of the thermal effect evolved by micro-organisms and the increase of the lag-phase period are associated with the death of microbial populations caused by diuron, which strongly affects soil microbial communities.  相似文献   

14.
2009年在黑龙江省鹤山农场进行6个土壤水分水平控制的大豆盆栽试验,土壤水分分别是:15%、18%、24%、30%、40%、48%.结果表明:土壤水分和大豆产量有很好的二次曲线关系,决定系数R<'2>达到0.97,大豆产量在田间持水量条件下达到峰值,低干、高于田间持水量时,大豆均减产,田间持水量80%～133%减产幅度...  相似文献   

15.
黄土高原退耕还林措施对深层土壤含水率的影响   总被引：3，自引：0，他引：3  
深层土壤水分分布状况对于黄土高原植被恢复和农业可持续发展意义重大。对陕北黄土区不同退耕还林措施(1979年种植的侧柏林、油松林和苹果林)及农地(对照)20 m深土壤剖面的土壤水分、根系分布状况及土壤粘粒含量进行了取样分析。结果表明:退耕还林措施显著降低了土壤含水率,总体表现为农地(11.30%)苹果林(6.66%)≈油松林(6.48%)≈侧柏林(5.92%)。深层土壤含水率同时受植物根系和土壤质地的影响,植物根系是影响4~10 m土壤含水率的主要因素,根系通过吸水作用降低了土壤含水率,但随着深度的增加,根系对土壤含水率的影响逐渐减弱,土壤质地对土壤含水率的影响逐渐增强,土壤含水率与土壤粘粒含量之间呈正相关关系。侧柏人工林根系影响土壤水分深度可达18 m,油松林的影响深度为16 m,35 a树龄的苹果林耗水深度为19 m左右。  相似文献   

16.
Metalaxyl and tricyclazole are two fungicides widely used in Spain in vineyard and rice crops respectively. In this study an investigation has been made of the effect of three organic amendments [two commercial amendments, solid fertiormont (SF) and liquid fertiormont (LF), and a residue from the olive oil production industry, alperujo (OW)] on fungicide fate in soils. Changes in soil porosity on amendment were studied by mercury intrusion porosimetry, sorption-desorption studies were performed by the batch equilibration method, dissipation of metalaxyl and tricyclazole in the soil was studied at - 33 kPa moisture content and 20 degrees C and leaching was studied in hand-packed soil columns. Amendments with SF and LF reduced soil porosity, while OW increased porosity through an increase in pore volume in the highest range studied. Tricyclazole sorbed to soils to a much higher extent than metalaxyl. With some exceptions, sorption of both fungicides increased on amendment, especially in the case of SF-amended soils, which rendered the highest K(oc) values. In soils amended with the liquid amendment LF, sorption either remained unaffected or decreased, and this decrease was much higher in the case of metalaxyl and a soil with 70% clay. In this clay soil, amendment with OW, of very high soluble organic matter content, also decreased metalaxyl sorption. Tricyclazole is more persistent in soil than metalaxyl, and both fungicides were found to be more persistent in amended soils than in unamended soils. Leaching of metalaxyl and tricyclazole in soil columns was inversely related to sorption capacity. The low recoveries of tricyclazole in leachates and in soil columns when compared with metalaxyl, a less persistent fungicide, were attributed to diffusion into micropores and to increase in sorption with residence time in the soil, both processes favoured by the low mobility of tricyclazole.  相似文献   

17.
日光温室不同水分条件下盆栽黄瓜产量和土壤微生物数量   总被引：4，自引：0，他引：4  
在日光温室内盆栽条件下,研究土壤水分对黄瓜产量和土壤微生物数量的影响,结果表明(1)土壤水分含量初花期和初瓜期为田间持水量的80%～90%、盛瓜期90%～100%、生育后期70%～80%的处理黄瓜产量最高,为389.65g/株;其次为初花期土壤水分为田间持水量的90%～100%、初瓜期80%～90%、盛瓜期70%～80%、生育后期90%～100%的处理,产量为351.49g/株;初花期土壤水分为田间持水量的80%～90%、初瓜期90%～100%、盛瓜期70%～80%、生育后期80%～90%的处理产量最低,为257.54g/株。(2)不同水分处理土壤微生物的数量变化不同黄瓜初花期,土壤水分为田间持水量80%～90%的处理土壤细菌数量最多,土壤水分为田间持水量70%～80%的处理和90%～100%的处理土壤细菌数量少,且二者差异不大。黄瓜初瓜期和盛瓜期当土壤水分由低变高时细菌数量增加,相反细菌数量减少,黄瓜生育后期当土壤水分从高变低时细菌数量增加,水分稳定不变或从高变为中等水平或从低变为中等水平时细菌数量减少。土壤真菌数量在土壤水分含量低时和土壤水分相对稳定的情况下增加,否则减少。各处理土壤放线菌在黄瓜初花期和初瓜期数量差异不大,盛瓜期各处理土壤放线菌的数量增加,生育后期多数处理土壤放线菌的数量有所下降。  相似文献   

18.
The release of [14C]triticonazole from coated maize seeds into soil, and its incorporation in maize, were studied under laboratory conditions over seven days in two soils at two different water contents (equivalent to a matrix potential of −3 kPa and −1580 kPa). The behaviour of a commercial coating formulation was compared to that of the same formulation supplemented with a pellicle to improve coated seed handling. Triticonazole released into soil, remaining in the integument and incorporated in different parts of the plant (stem, root, albumen) was measured. The triticonazole released into the soil corresponded to 25% of the initial applied amount on the seed under the best conditions (sandy soil, matrix potential of −3 kPa, set without pellicle). In these conditions, 13% of applied triticonazole was incorporated into roots and stems after seven days. The presence of an additional pellicle to improve the coating decreased the quantity of triticonazole released into soil and consequently the quantity of triticonazole incorporated into the plant. In all cases, the diffusion of triticonazole from the seed to the soil was not limited by the water solubility of triticonazole. Instead, the sorption of triticonazole on soil appears to be the key process governing its fate in soil. © 2000 Society of Chemical Industry  相似文献   

19.
针对旱区土壤板结严重和耕层深度变浅等问题，于2021年在宁夏暖泉农场开展大田试验，以传统旋耕为对照(CK),设置不同粉垄耕作深度30 cm(FL30)、40 cm(FL40)、50 cm(FL50)和60 cm(FL60),探究粉垄耕作对玉米田土壤关键物理性质的影响。结果表明：与传统旋耕相比，粉垄耕作能够有效降低土壤容重且提高土壤孔隙度，FL50处理表层土壤(0～20 cm)容重降低11.55%、孔隙度提升12.17%,FL40处理中层土壤(20～40 cm)容重降低8.57%、孔隙度提升9.14%,FL60处理深层土壤(40～60 cm)容重降低11.61%、孔隙度提升12.75%;粉垄耕作对玉米各生育期土壤蓄水量具有显著影响，FL40处理土壤蓄水量提升24.86%,土壤机械稳定性团聚体数量(0.25～5 mm)提高9.63%;较传统旋耕，粉垄耕作可达到疏松土壤与提高土壤蓄水保墒能力的效果，粉垄耕作通过改善玉米的生长条件和土壤环境提高了籽粒产量，其中FL60、FL50、FL30处理分别较CK处理增产57.14%、15.48%、8.79%。研究成果可为改善旱区土壤多年板结及水土资源可持...  相似文献   

20.
The herbicide isoproturon was degraded rapidly in a sandy loam soil under laboratory conditions (incubation temperature, 15°C; soil moisture potential, -33 kPa). Degradation was inhibited following treatment of the soil with the antibiotic chloramphenicol, but unaffected by treatment with cycloheximide, thus indicating an involvement of soil bacteria. Rapid degradation was not observed with other phenylurea herbicides, such as diuron, linuron, monuron or metoxuron incubated in the same soil under the same experimental conditions. Three successive applications of isoproturon to ten soils differing in their physicochemical properties and previous cropping history induced rapid degradation of the herbicide in most of them under laboratory conditions. There were, however, no apparent differences in ease of induction of rapid degradation between soils which had been treated with isoproturon for the last five years in the field and those with no pre-treatment history. A mixed bacterial culture able to degrade isoproturon in liquid culture was isolated from a soil in which the herbicide degraded rapidly.  相似文献   

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