Adsorption-Desorption Characteristics of Chlorimuron-Ethyl in Soils

The adsorption-desorption characteristics of chlorimuron-ethyl in soils were investigated to provide the basic data for evaluating the safety in field and the risk to water resource. The adsorption-desorption experiment was conducted by the batch equilibration and HPLC techniques; furthermore, data were analyzed with 5 mathematic models to describe the characteristics and mechanism of adsorption-desorption and translocation of the herbicide in soils. The results showed that the adsorption-desorption isotherms of chlorimuron-ethyl fitted for the Freundlich model well, and the physical reaction presents the main contribution during the adsorption-desorption process. The adsorption values （Kads-f） of chlorimuron-ethyl in 8 types of soil ranged from 0.798 to 6.891. The isotherms of 2# （Jiangxi clay） and 3# （Jiangxi sand loam） soils belong to the S-type curve, while the isotherms of another 6 type soils belong to the L-type isotherm. The results of desorption indicated that the hysteresis phenomena appeared during the desorption process, and the hysteresis coefficients （H） of the herbicides in 8 soils varied from 0.259-0.980. Furthermore, Kads-f and desorption values （Kads-f） increased with the OM （%） and the clay content increasing, while the values decreased with the soils pH increasing. The H values decreased with the OM and the clay content increasing, and increased with the soils pH increasing. It can be concluded that the low adsorption abilities of chlorimuron-ethyl in test soils and un-reversible adsorption existed in the process, which will induce the great translocation of the herbicide after application in field. It can be transported to ground or groundwater causing risk to environments. The physical and chemical properties of soils, including the OM, the clay content, and the pH of soil were the dominating factors during the adsorption-desorption.     

pH和有机质对三种不同土壤镁吸附特性的影响

选取黄壤、紫色土和石灰性土3种土壤为研究对象,采用一次平衡吸附法,研究了pH、有机质对镁吸附的影响.结果表明,不同pH和有机质条件下,土壤对镁的最大吸附量有较大差异,黄壤和紫色土受pH影响较明显,在pH3.5～7.5这个范围,黄壤对镁的最大吸附量变化在1 336.25g～2 054.77 mg/kg,紫色土在1 417.04～2 025.38 mg/kg,石灰性土变化不大.去有机质后,黄壤、紫色土和石灰性土对镁的吸附能力下降,最大吸附量分别减少363.31,148.72,120.00 mg/kg.Langmuir方程能很好的拟合土壤对镁的吸附过程.

Abstract：

The effects of pH and organic matter on adsorption of magnesium in yellow soil, purple soil and calcareous soil were studied in a batch adsorption experiment. Considerable differences were observed among the three soils in their maximum Mg adsorption under different pH and organic matter conditions.The adsorption of magnesium was mainly related to the changes in pH in yellow soil and purple soil. In the pH range of 3.5-7.5, the maximum magnesium adsorption varied from 1 336.25 to 2 054.77 mg · kg-1 in the yellow soil and from 1 417.04 to 2 025.38 mg · kg-1 in the purple soil, while little change was detected in the calcareous soil. The ability of Mg adsorption decreased after the removal of organic matter in the above three soils and the maximum Mg adsorption decreased by 363.31 mg· kg-1 , 148.72 mg · kg-1 and 120.00 mg · kg-1, respectively. Magnesium adsorption in soils was well fitted with the Langmuir equation.     

Influences of Charcoal Amendment on Adsorption-Desorption of Isoproturon in Soils

In order to prevent pesticide leaching from soil, the effects of charcoal amendment on adsorption-desorption of isoproturon in soils were studied and the mechanisms in reducing the loss of isoproturon from soils were suggested. Adsorption-desorption of isoproturon in five different particle sizes of charcoals and three different soils were studied using batch equilibration technique. The results showed that the experimental data were well fitted by the Freundlich empirical equation. Charcoal had a great adsorption capacity for isoproturon, and the smaller the particle size of charcoal, the more the adsorption of isoproturon. The amendment with charcoal could greatly improve the adsorption of isoproturon in soils. The adsorption of isoproturon in soils increased with the rate of charcoal amended （r= 0.9568＊＊, P 〈 0.01）. Desorption of isoproturon from charcoals and soils showed significant hystersis which was shown by the higher adsorption slope （1/nsds） compared to the desorption slope （1/ndes. The hysteresis effects of charcoal on desorption of isoproturon were closely correlated with the content of charcoal in the soils, and the hysteresis index （H） increased with the rate of charcoal amended. Observation of environmental scanning electron microscopy （ESEM） exhibitted the fine pore structure and special surface characteristics of the tested charcoal. Analysis of Fourier transform infrared spectra （FTIR） of isoproturon adsorbed on charcoal suggested probable bonding interactions between isoproturon and charcoal. This research suggests that charcoal amendment may be an effective management practice for controlling pesticide desorption and leaching in soils.     

Effect of Crop-Straw Derived Biochars on Pb(Ⅱ) Adsorption in Two Variable Charge Soils

Two variable charge soils were incubated with biochars derived from straws of peanut, soybean, canola, and rice to investigate the effect of the biochars on their chemical properties and Pb（II） adsorption using batch experiments. The results showed soil cation exchange capacity （CEC） and pH significantly increased after 30 d of incubation with the biochars added. The incorporation of the biochars markedly increased the adsorption of Pb（II）, and both the electrostatic and non-electrostatic adsorption mechanisms contributed to Pb（II） adsorption by the variable charge soils. Adsorption isotherms illustrated legume- straw derived biochars more greatly increased Pb（II） adsorption on soils through the non-electrostatic mechanism via the formation of surface complexes between Pb（II） and acid functional groups of the biochars than did non-legume straw biochars. The adsorption capacity of Pb（II） increased, while the desorption amount slightly decreased with the increasing suspension pH for the studied soils, especially in a high suspension pH, indicating that precipitation also plays an important role in immobilizing Pb（II） to the soils.     

Adsor ption and Degradation of Bensu—lfuron—methylin Paddy Field

This paper studied adsorption and deyradation of bensulfuron-methyl(BSM) by bioassay method.The results showed that adsorption rate of BSM increased with increasing organic matter content.Degradation velocity of BSM changed fast with pH increasing and temperature decreasing.There were different degradation of BSM between in water and soil.BSM was degraded rapidly in initial period.Afterward the degradation of BSM was slow dow.With increasing organic matter content deyradation of BSM in water was faster than that in soil.     

Influence of Organic Amendments on Adsorption, Desorption and Leaching of Methiopyrisulfuron in Soils

Methiopyrisulfuron is a novel sulfonylurea herbicide with good activity for annual broadleaf and gramineal weeds control. Present study was to investigate the effects of organic amendments （including peat （PE）, sewage sludge （SS）, and humic acid （HA）） on adsorption, desorption and leaching of methiopyrisulfuron in soils. The batch equilibration technique was applied for adsorption-desorption experiments and the leaching was tested through soil column simulated experiments under laboratory conditions. The Freundlich model may well describe adsorption-desorption of methiopyrisulfuron on organic amendments, the natural soil, and amended soils. Organic amendments could not only greatly increase the adsorption capacity of methiopyrisulfuron, but also significantly enhance the hysteresis of desorption of methiopyrisulfuron. The correlations between K_f-ads and organic matter content of amended soils were significant, and the correlations between H and soil organic matter in amended soils with PE, SS, and HA were significant too. The results of soil column experiments indicated that organic amendments greatly decreased leaching of methiopyrisulfuron. This study suggested that PE, SS, and HA could greatly influence environmental behavior of methiopyrisulfuron in soils. Use of organic amendments might be an effective management practice for controlling potential pollution of methiopyrisulfuron to environment.     

Effect of Distances from Different Trees Species on the Properties of Mollic Horizon

The study area is located in Duhok province-Kurdistan region-Northern Iraq and including two locations the first location is situated in Galbook village and the vegetation cover is trees of （Quercus aegilops L.）, the second location is situated in Koradeer village that covered with threes of Prunus dulcis （Mill.） Webb.. Disturbed surface soil samples at depth 0-30 cm were collected at four different distances （1, 5, 10 and 15 m） from the tree with randomized selection three trees in each study location. Soil organic matter decreases with increasing distances from tree in both locations under two different trees species, which is attributed to the effect of tree crown. Ordinarily, organic matter content in both locations correspond to the requirements of Mollisols. Statistical analysis of data showed significant differences in organic matter content between locations. Cation exchange capacity is high under tree crown and decreasing with distances from tree in both locations, as a result of decreasing organic matter and increasing calcium carbonate with distances. Commonly soil pH is slightly increased with increasing distances from tree because of increasing calcium carbonate with distances and decreasing organic matter content. Calcium was not uniform with distances and Mg decreasing with distances in both locations. The values of fine clay/coarse clay and fine clay/total clay of soil samples confirm development of the soils under study. Porosity percentage under tree crown is high and decreasing with distances. Soil bulk density was increased with distances in both locations, as a result of decreasing organic matter content with distances. This study aims to explain the effect of tree distances and species on the mollic horizon properties.     

Study the Physical,Chemical, Mineralogical,and Geo-technical Properties of Soils Used in Pottery Industries,Kurdistan-lraq

The study area is located in Duhok and Sulaimania province in Kurdistan region, lraq. Study soils developed from parent material that has derived from limestone. Randomize, composed and disturbed surface soil samples were collected. The bulk soils were air dried, crushed and passed through 2 mm sieve. Standard methods were used for chemical, physical, geotechnical and mineralogical analyses of soil samples. The results indicated that the study soils texture were clay to loam clay, this texture was considered as suitable for ceramic and pottery industries as a result of increasing clay contents that ranged between 301 g/kg and 676 g/kg. Soil consistence depending on geotechnical properties increased the ability of study soils for resistance rapture and deformation. Existence the high amount of cementing agents in study soils such as organic matter, iron oxides and particularly total carbonate （247.2-308.8 g/kg） act to reduce the bad effect of the smectite minerals group （high shrinkage） in soils of study locations through increasing the resistance of these soils for rupture and deformation. The existing of Kaolinite, palygorskite and chlorite allows clay to be dried in ceramic and pottery industries without cracking from shrinkage. Study soils were different in their colors as a result of existence, different pigmentation materials that led to coloring soils with different colors in turn caused coloring of pottery and ceramic materials. Since, there are no available academic studies or researches about this subject in Kurdistan region in addition the clay pottery and ceramic sector still has a good market at the same time using this type of soils for arts, therefore, this study was conducted.     

Effects of Glucose Addition on N Transformations in Paddy Soils with a Gradient of Organic C Content in Subtropical China

To better understand the interaction of N transformation and exogenous C source and manage N fertilization, the effects of glucose addition on N transformation were determined in paddy soils with a gradient of soil organic C content. Changes in N mineralization, nitrification and denitrification, as well as their response to glucose addition were measured by incubation experiments in paddy soils derived from Quaternary red clay in subtropical China. Mineralization and denitrification were changed in order of increasing soil fertilities： high 〉 middle 〉 low. During the first week of incubation, net N mineralization and denitrification rates in paddy soil with high fertility were 1.9 and 1.1 times of those in soil with middle fertility and 5.3 and 2.9 times of those in soil with low fertility, respectively. Addition of glucose decreased net N mineralization by approximately 78.8, 109.2 and 177.4% in soils with high, middle and low fertility, respectively. However, denitrification rates in soils with middle and low fertility were increased by 14.4 and 166.2% respectively. The highest nitrate content among the paddy soils tested was 0.62 mg kg-1 and the highest nitrification ratio was 0.33%. Addition of glucose had no obvious effects on nitrate content and nitrification ratio. It was suggested that the intensity of mineralization and denitrification was quite different in soils with different fertility, and increased with increasing soil organic C content. Addition of glucose decreased mineralization, but increased denitrification, and the shifts were greater in soil with low than in soil with high organic C content. Neither addition of glucose nor inherent soil organic C had obvious effects on nitrification in paddy soils tested.     

Dissipation and Adsorption Behavior of the Insecticide Ethiprole on Various Cultivated Soils in China

In this study, the hydrolysis of the insecticide ethiprole in buffered solutions at pH 4.0, 7.0 and 9.0, respectively, and the degradation and adsorption-desorption behaviors of ethiprole in ifve agricultural soil samples from China were investigated. The half-lives under anaerobic conditions were faster than that in the aerobic experiment. Ethiprole was relatively stable under both acidic and neutral conditions while it was readily hydrolyzed under alkaling condition. The sorption of ethiprole on ifve soils was well described by the linear and Freundlich equation and mainly governed by soil organic matter. The exothermic process of ethiprole adsorption can also be well explained by physical adsorption. A weak adsorption capacity was observed in all soils, which could readily lead to leaching problems.