جستجوی مقالات مرتبط با کلیدواژه « آفت کش » در نشریات گروه « آب و خاک »

Since water and soil are important components of the ecosystem ‎and their quality reduction affects the environment and agriculture, it is necessary to determine ‎the effects of pesticides on soil and water resources and determine their residual concentration ‎levels in the land. Agriculture, especially paddy fields, should be controlled and managed. ‎Therefore, the purpose of this study is to determine and evaluate the level of residual ‎concentrations of organophosphate pesticides in soil and water samples of Rudbar County and to ‎investigate their ecotoxicological status.‎

In this study, the multiplicity of 12 stations was determined using a ‎systematic random method in the paddy lands of Rudbar County. In total, 24 samples including ‎‎12 water samples and 12 soil samples were collected. Water sampling was performed in 1-liter ‎dark-colored bottles and soil sampling was performed from the surface layer according to the ‎standard method. All samples were transferred to a laboratory in a freezer containing dry ice. ‎Organophosphate pesticides were measured using the EPA 8041b standard method. All analyzes ‎were performed by gas chromatography with the mass detector in Aria Shimi Sharif Company. To ‎study the ecotoxicological status of pesticides, two databases named National Pesticide ‎Information Center and Pesticide Properties Database were used. The two databases are affiliated ‎with Oregon State University, the US Environmental Protection Agency, and the University of ‎Hertfordshire. Statistical analysis of the data included analysis of variance using one-way ‎ANOVA test, comparison of means using Duncan's test, correlation using Pearson's method, and ‎analysis of principal components using the covariance method.‎

Based on the results, 11 organophosphate pesticides were identified in water and soil ‎samples of Rudbar paddy fields. Ethion in soil and Diazinon in the water had the highest residual ‎concentrations. Sheikh Ali Tues 1 and 2 and Mirzagolband 1 stations with the values of 4.55, ‎‎3.99 and 3.49 ug/kg had the highest amount of Ethion toxin residues in the soil. In addition, ‎Sheikh Ali Tues 2, Mirzagolband 1, and Halimeh-Jan stations with 3.96, 1.71, and 1.68 ug/L, ‎respectively, had the highest amount of Diazinon pesticide in water samples. The results showed ‎that the downstream lands in the area of Imamzadeh-Hashem compared to the upstream lands in ‎Rudbar city have a higher concentration and load of pollution. The mean concentration remaining ‎in soil samples (0.987 ug/kg) was higher than in water samples (0.304 ug/L). Based on the results ‎of pesticides Diazinon, Methyl Parathion, Azinphos Methyl, Malathion, and Ethion in the studied ‎stations showed a significant difference. A comparison of the mean residual concentrations of ‎pesticides with their physicochemical and ecotoxicological properties showed that in terms of ‎potential risk and toxicity for aquatic organisms, the concentrations of BetaMevinephos, ‎Malathion, and Azinphos Methyl pesticides were 0.043, 0.573, and 0.272 ug/kg, respectively. Has ‎been very high, which has put these pesticides in a situation of high and toxic danger to aquatic ‎organisms in the region.‎

Extreme use of pesticides on agricultural land has caused environmental problems. ‎As a result, monitoring and evaluation of pesticide residues in paddy fields are very important ‎because contaminated effluents are discharged directly from rice fields into rivers, depending on ‎several factors. Due to the high levels of residual concentrations of some organophosphate ‎pesticides in the region, it is necessary to hold training courses on farmers' familiarity with the ‎dangers of pesticides to prevent, control, and reduce pollution under the supervision of experts. ‎Also, to fight non-chemically against pests, it is suggested to use the Trichogramma bee in the ‎form of Trichocart to fight the rice stem-eating worm, colored traps, and attractants in paddy ‎fields.‎

The excessive use of pesticides in recent years and their continuation in the future may have harmful effects on the microbial population of the soil, as an indicator of soil health and one of the main components of the environment. The purpose of this study was to investigate the effect of three mostly used insecticides (Diazinon, Chlorpyrifos and Imidacloprid) on ec-ophysiological and chemical indices of soil. The experiment was conducted as a factorial in a completely randomized design which included the pesticide factor at four levels (three insecticides plus control soil) and time factor at three levels (before, three months and six months after pesticide application). Concentrations of insecticides (0.1, 1 and 0.67) mg per kilogram of soil were used for imidacloprid, diazinon, and chlorpyrifos, respectively. Some biological and ec-ophysiological indices of the soil were measured at the beginning of the experiment, three and six months after the beginning of the experiment. The results showed that, the application effect of insecticides after three months affected the biological indices including dehydrogenase enzyme activity, metabolic quotient, basal respiration, substrate-induced respiration and also organic carbon decreased compared to the control -92.2%, -46.7%, -24.7%, 15.8% and -7.61%, respectively and urease enzymes activity, microbial biomass carbon, microbial biomass nitrogen, carbon to nitrogen ratio and soil microbial quotient increased compared to control 6.67%, 32.1%, 15.6%, 16.5% and 58.9. Also, the results showed that among the insecticides Chlorpyrifos and Diazinon had the highest and the least negative effect on the indices, respectively. The application of insecticides Diazinon, Chlorpyrifos and Imidacloprid at least in the short term, had a negative effect on soil ecophysiological indices and the most sensitive indices for determining the negative impact of insecticides on the soil microbial community were the dehydrogenase enzyme activity, metabolic quotient, substrate-induced respiration and basal respiration.

This study aimed to investigate the effect of five herbicides (Tribenuron-methyl, Metribuzin, Trifluoralin, Haloxyfop-methyl, and 2, 4-D (on the soil dehydrogenase and urease activities.

The experiment was conducted as a completely randomized design with five herbicides and a control with three replicates for six months and the enzyme activities were measured at beginning of the experiment, and after three and six months. The concentration of herbicides was 0.27, 0.67, 0.67, 0.67, and 0.1 mg/kg soil for Haloxyfop-methyl, Metribuzin, Trifluoralin, 2, 4-D, and Tribenuron-methyl, respectively.

The results showed that the effect of herbicides on the enzyme activities was significantly different (p0.01). After 3 months, the herbicides decreased the urease activity in comparison to the control (34.9 µgN.g-1). The most reduction was related to Trifluoralin (24.8 µgN.g-1) which was 28.9% lower than the control. Urease activity increased after six months compared to three months, and this increase was 41.5% for Trifluoralin herbicides (35.1 µgN.g-1). Urease activity in control treatment in six months was not significant compared to the three months. All of the herbicides significantly reduced the dehydrogenase activity after three months compared to the control (0.6 µgTPF.g-1), so that the dehydrogenase activity was observed in Haloxyfop treatment with 0.01 µgTPF.g-1, which was 98% lower than the control. In all treatments, dehydrogenase activity after six months was significantly higher than that in the three months, so that the highest dehydrogenase activity was observed in 2,4-D treatment (1.44 µgTPF.g-1), which was significantly higher than the control.

The results show that the herbicides significantly decreased the activity of the enzymes compared to the control during the three months. After six months the enzyme activities recovered to the level before herbicides application. Probably this was due to a short lifetime of herbicide in the soil which was less than six months.

The intensive and inappropriate use of pesticides caused environment to be contaminated. Quantifying the fate of applied herbicides in the soil is essential for minimizing their mobility in the soil and environmental pollution. The leaching and degradation of the metribuzin herbicide in three soils were investigated under laboratory conditions. Metribuzin was mobile in the soils when tested using non-aged and aged soil columns. The mobility of herbicide in the soil is related to the adsorption phenomenon in the same soil. It was found that the mobility of metribuzin in the soils 7 and 5 (with less organic carbon) was more than the one in the soil 1. The difference in the adsorption affinity of metribuzin in different soils appears to be due to differences in soil properties, such as clay content, organic matter content and pH value. The calculated half-life values in sterile and non-sterile conditions ranged from 37.92 to 105.74 days. Metribuzin persistent in the soil was corresponded to columns 1, 5 and 7 respectively.

The effects of dissolved organic matter (DOM), derived from compost, on the sorption of simazine by soils were studied using a batch equilibrium technique. Six soils with different organic carbon contents were investigated in this study. Simazine sorption isotherms on soils were described by the linear equation, and the distribution coefficients without DOM (Kd) or with DOM (Kd*) were obtained. Generally, the values of Kd*/Kd were initially increased and then decreased with raising DOM concentrations of 0-65 mg DOC·L in the soil-solution system form. Critical concentrations of DOM (DOMnp) were obtained, and the value of Kd* was equal to Kd. The presence of DOM with concentrations lower than DOMnp promoted simazine sorption on the soils (Kd* > Kd), whereas the presence of DOM with concentrations higher than DOMnp tended to inhibit the simazine sorption (Kd* < Kd). Interestingly, DOMnp for the tested soils was negatively correlated to the soil organic carbon content, and the maximum of Kd*/Kd (Kmax) was correlated positively with the maximum of DOM sorption on the soil (Xmax). Further investigations also showed that the presence of the hydrophobic fraction of DOM evidently promoted the simazine sorption on soils, whereas the presence of hydrophilic DOM fraction obviously tended to inhibit the simazine sorption.

Soil pollution, i.e. elevated concentration of undesirable organic and inorganic matter such as trace elements higher than natural background concentration can be a consequence of indirect or intentional human activities. Evaluation of the effect of the agricultural operations and particularly using the wastewater on soil trace element concentrations is useful and required to manage the land and reduce the health risks of the food products. The aims of this study were: [1] The estimation of the mean concentration and max limit of the background concentration for Cd, Cr, Ni, Pb, Co and Hg in the surface soil samples of Boroujen-Faradonbeh plain; and [2] Evaluation of the effect of agricultural operation and farming by non-conventional water on background concentration and on accumulation, distribution and pollution load of the soil of this plain.
Boroujen-Faradonbeh is an agricultural plain loaced in the Chaharmahal and Bakhtiari mountainous province of Iran. Two hundered surface soil samples (0-20 cm) were taken from three types of land: never-uncultivated soil (20 samples), freshwater-irrigated (90 samples) and wastewater-irrigated (90 samples) soils. The total sampled area was about 2340 hectares. The exact position of the samples were recoded using a GPS device. The total concentrations of Pb, Co, Ni, Cd, Cr and Hg in the samples, and the background and upper limit concentrations were determined. In addition, pollution loading index (PLI) for the whole plain determined and delineated. To separate the affects of agricultural practices and wastewater application the analysis of variance of StatSoft Statistica 12 was used. Maping, and related operations were conducted inside ArcGIS 9.3.
Background concentrations of Ni, Cd, Cr, Hg, Co, and Pb, were determined as 1.13, 0.16, 1.56, 0.09, 0.80, and 1.52 mg/kg, respectively; while upper limit concentrations for the mentioned trace elements were respectively 1.3, 0.28, 1.6, 0.16, 0.9, 1.7 mg/kg. Conventional farming (application of fertilizer but not wastewater) increased the soil accumulation factor of Cd and Pb to 1.7 and 1.9 (p

The environment is contaminated through intensive or inappropriate use of herbicides. Quantifying the fate of applied herbicides in the soil is essential for minimizing their mobility in the soil and environmental pollution. The adsorption behavior of the soil-applied herbicides is one of the most important factors governing its environmental impacts such as degradation, transition and leaching. To date, No studiy has been conducted to investigate the effects of DOM on the sorption of metribuzin by soils. The objective of this study was to investigate the impacts of DOM on metribuzin sorption by two defferent soils.
In this research, DOM (0, 10, 20, 40, 80 and 160 mg of OC/L) adsorption in two different soil samples was assayed under laboratory conditions at constant temperature. The effect of pH and DOM concentrations (0, 10, 40 and 160 mg/L) on metribuzin (1.5, 2, 3, 4, 5 and 6 mg/kg) adsorption was also studied. Soil samples were selected and collected from surface layers (0–20 cm). The soil samples were air-dried and passed through a 2-mm sieve. The DOM sorption in both soils was performed by adding 10 ml DOM solution with a series of initial concentrations in each 15 ml glass tube containing 1.00 g soil. All the DOM solutions contained 0.01 mol/L CaCl2 and 0.01 mol/L thymol, and the pH of the solutions were adjusted to 9.0 (about the pH of the initial extracted DOM solution) with 0.1 mol/L HCl or 0.1 mol/L Ca(OH)2. The tubes were shaken at 140 rpm for 24 h at 22°C. After centrifugation at 4,500 rpm for 15 min, the DOM concentrations in solutions (presented as OC) were measured using a total organic carbon analyzer. Sorbed organic carbon was calculated from the difference between the OC content of the DOM solution, which was initially added, and that found in equilibrium solution with the soil, of which the amount of native DOM released from the air-dried soil samples was subtracted. DOM solutions (10 ml) with different concentrations were added to the soils in 15 ml glass tubes with PTFE lined screw caps. The solid-to-solution ratios were adjusted to attain 20–80 percentage of the initially added metribuzin adsorption by the soils. All the DOM solutions contained 0.01 mol/L CaCl2 to maintain a constant ionic strength and 0.01 mol/L thymol to inhibit potential microbial activities, and the pH values of the solutions were adjusted to 9.0 with 0.1 mol/L HCl or 0.1 mol/L Ca(OH)2. Metribuzin was mixed at high concentration in acetonitrile before being added to the DOM solutions. Acetonitrile concentrations were always less than 0.1 percentage of the total solution volume to avoid the cosolvent effect. The tubes were shaken at 140 rpm for 24 h at 25°C. Preliminary studies showed that sorption equilibrium was approached within this time period. After mixing, the tubes were centrifuged at 4,500 rpm for 15 min, and 1.0 ml of the supernatant was removed into a sampling vial for analysis. All sorption samples were conducted in triplicate. The sorption experiments were conducted at different pH values in the absence of DOM by addition of HCl and Ca(OH)2 as required to solutions containing 0.01 mol/L CaCl2 and 0.01 mol/L thymol. The investigated pH values ranged from 4 to 9.5. The initially added concentration of metribuzin was 5 mg/L. After shaking and centrifugation, the pH values of the supernatants were measured using a pH meter. The samples were analyzed by gas chromatography equipped with a mass (6890N, Agilent, USA). Metribuzin sorption was calculated from the difference between the total amount of metribuzin initially added to the solution and the amount remained in the solution at equilibrium.
Dissolved organic matter (DOM) was adsorbed on the soils and the experimental data was better fitted to the Freundlich isotherm (R>0.999). The KF parameter amount of DOM sorbed on the soils were 3.82 and 0.95 L/kg for the soils of 1 and 2, respectively which suggested that the soils have low affinity to metribuzin . In the presence of DOM, the sorption behaviors of metribuzin by the soils were different. The effects of DOM on metribuzin sorption were dependent on the characteristics of soils and the concentrations of present DOM. Metribuzin sorption by soil 1 and soil 2 was inhibited in the presence of DOM. Metribuzin sorption was quantified by comparing the apparent distribution coefficient of metribuzin in the presence of DOM (Kd*) and the absence of DOM (Kd). The sorption was promoted when the ratio of Kd*/Kd was more than 1, and was inhibited when the ratio of Kd*/Kd was less than 1. The aqueous solubility, sorption, and bioavailability of metribuzin are pH dependent. The effects of pH on the metribuzin sorption by soils showed when pH increased from 4 to 9, metribuzin sorbtion by soils was decreased. When the pH was higher than 6.0, it was clear that the amount of sorbed metribuzin decreased as the solution pH increased in each soil in the absence of DOM. Metribuzin was present in both molecular and ionic forms owing to the ionization in the pH range examined in the study. As the solution pH increases, the protonic form decreases. Therefore, the sorption of metribuzin protonic form and the negatively charged surface of soils become more pronounced and the amount of metribuzin partitioned to soil decreases. In addition, an increasing pH may enhance the release of native organic matter from the soils into the solution that results in the decrease of metribuzin sorption. At the same pH, the amount of metribuzin sorbed by soil 2 was lower than soil 1 which was probably owing to the different organic matter content of the soils.
The effects of DOM on metribuzin sorption were dependent on the characteristics of soils and the concentrations of present DOM. In general, metribuzin sorption by the soils was inhibited in the presence of DOM. Metribuzin sorption by the soils also decreased with increasing the solution pH in the absence and present of DOM. The results of the study will be useful for the better understanding of the behavior of metribuzin in soils and its ecological risks.