不同利用方式土壤中磷的吸附与解吸特性

研究不同利用方式土壤对磷的吸附解吸特性及其影响因素。采用室内恒温培养法研究了湖南典型土壤(红壤、潮土和紫色土)的不同利用方式(旱地、水田)土壤对P的吸附和解吸过程。土壤对磷的吸附解吸过程是分阶段进行的,用Langmuir方程拟合程度比Freundlich方程高,相关系数均在0.90(P<0.05)以上;从最大吸附量(Qm)、吸附反应常数(K)和最大缓冲容量(MBC)3项吸附参数综合考虑,旱地对P的吸附无论在强度还是容量方面均大于同母质的水田土壤;解吸率随着吸附量的增加而增大,其大小为旱地<水田。Qm与<0.002 mm粘粒及无定形铁含量呈正相关,相关系数分别为0.95和0.94(P<0.05)。不同利用方式土壤P吸附解吸特性差别较大,针对不同土壤应采取不同的磷素管理措施以实现作物增产和保护环境的双重效益。     

A comparison of five pesticides adsorption and desorption processes in thirteen contrasting field soils

Batch adsorption and desorption experiments were performed using thirteen agricultural soil samples and five pesticides. Experimental data indicated a gradient in pesticide adsorption on soil: trifluralin > 2,4-D > isoproturon> atrazine > bentazone. Atrazine, isoproturon and trifluralin adsorption were correlated to soil organic matter content (r2 = 0.7, 0.82, 0.79 respectively). Conversely, bentazone adsorption was governed by soil pH (r2 = 0.68) while insignificant effect has been shown in the case of 2,4-D. Multiple linear regressions were used to combine relationships between the various soil parameters and the Freundlich adsorption coefficient (K(f)) of each pesticide. Then desorption was assessed since it may reflect some of the interactions involved between the pesticides and the soil components. Adsorbed molecules were released into aqueous solution in the following order: bentazone > atrazine> isoproturon> 2,4-D > trifluralin. The occurrence of hysteresis did not allow an accurate interpretation of the pesticide desorption data because of the possible interplay of several processes.     

Effect of four alcohols on adsorption, desorption, and movement of cadmium, nickel, and zinc through soils

Miscible-displacement experiments were conducted to compare the effects of aqueous soil solutions with ethyl alcohol, ethylene glycol, diethylene glycol, and triethylene glycol on the movement of metals through soils. Aqueous or alcohol solutions containing 1 mM each Cd, Ni, and Zn and 5 mM Ca were perfused through columns containing River Sand, Canelo loam (Canelo 1) or Mohave sandy clay loam (Mohave scl) until effluent metal concentrations (C) equaled influent concentrations (C₀) or CC₀⁻¹ = 1. In general, the order of sorption was Zn > Ni > Cd in aqueous-perfused columns, while in alcohol-perfused columns sorption of Ni Cd ≥ Zn. In comparison to aqueous solutions, alcohols reduced total metal sorption by at least 25%. Metal sorption was best correlated to cation exchange capacity of the soil, sorption of metals being greatest in the Mohave scl and least in the River Sand. After CC₀⁻¹ = 1 was reached, columns were leached with deionized water. While leaching did not affect the sorption of metals in columns which had been perfused with aqueous solvents, sorption behavior of metals changed significantly in columns which had been perfused with alcohol solvents. Leaching caused desorption of 5 to 30% of the sorbed Ni. In general, Cd was desorbed (up to 45%) from the soils tested. The exceptions were River Sand columns perfused with diethylene and triethylene glycol in which additional Cd was sorbed to the soil from the soil solution. Additional Zn was sorbed in all columns tested with the exception of the Canelo 1 column perfused with ethyl alcohol.     

Assessment and distribution of antimony in soils around three coal mines, Anhui, China

Thirty-three soil samples were collected from the Luling, Liuer, and Zhangji coal mines in the Huaibei and Huainan areas of Anhui Province, China. The samples were analyzed for antimony (Sb) by inductively coupled plasma-optical emission spectrometry (ICP-OES) method. The average Sb content in the 33 samples was 4 mg kg(-1), which is lower than in coals from this region (6.2 mg kg(-1)). More than 75% of the soils sampled showed a significant degree of Sb pollution (enrichment factors [EFs] 5-20). The soils collected near the gob pile and coal preparation plant were higher in Sb content than those collected from residential areas near the mines. The gob pile and tailings from the preparation plant were high in mineral matter content and high in Sb. They are the sources of Sb pollution in surface soils in the vicinity of coal mines. The spatial dispersion of Sb in surface soil in the mine region shows that Sb pollution could reach out as far as 350 m into the local environment conditions. Crops in rice paddies may adsorb some Sb and reduce the Sb content in soils from paddyfields. Vertical distribution of Sb in two soil profiles indicates that Sb is normally relatively immobile in soils.     

Adsorption, desorption, and mobility of permethrin in Malaysian soils

The adsorption, desorption, and mobility of permethrin in six tropical soils was determined under laboratory and greenhouse conditions. The six soils were selected from vegetable growing areas in Malaysia. Soil organic matter (OM) was positively correlated (r2 = 0.97) with the adsorption of permethrin. The two soils, namely, Teringkap 1 and Lating series with the highest OM (3.2 and 2.9%) released 32.5 and 30.8% of the adsorbed permethrin after four consecutive repetitions of the desorption process, respectively, compared to approximately 75.4% of the Gunung Berinchang soil with the lowest OM (1.0%) under the same conditions. The mobility of permethrin down the soil column was inversely correlated to the organic matter content of the soil. Permethrin residue penetrated only to the 10-15 cm zone in the Teringkap 1 soil with 3.2% OM but penetrated to a depth of more than 20 cm in the other soils. The Berinchang series soil with the lowest OM (1.0%) yielded leachate with 14.8% permethrin, the highest level in leachates from all the soils tested. Therefore, the possibility for permethrin to contaminate underground water may be greater in the presence of low organic matter content, which subsequently allows a higher percentage of permethrin to move downwards through the soil column.     

A sensitivity analysis of adsorption and degradation parameters in the modeling of pesticide transport in soils

The increasing use of deterministic models in predicting the movement of pesticides in soils, has focused attention on the evaluation of major parameters which represent attenuation factors of organics in the subsurface. These parameters are the degradation rate constant and the adsorption constant for the pesticide. In view of the large in situ variability of these parameters and of the difficulty in obtaining accurate field data, there is a high degree of uncertainty associated with the results obtained from deterministic models. A sensitivity analysis is performed here to quantify the impact of such variation in each of these input parameters on the output results of an unsaturated zone transport model (PRZM). Results show that variations in these parameters about their respective mean values greatly affect the predicted concentration distributions, obtained after three years, of the pesticide aldicarb in all the soil profile. A 15–22% variation in the degradation constant, or a 24% variation in the adsorption constant, lead to a 100% uncertainty in the various simulation results defined as the cumulative quantity of aldicarb or the dissolved aldicarb concentration leached below the root zone (or the unsaturated zone) of the soil. Such a deterministic model presents a high degree of sensitivity to these input parameters. Accurate field data are then needed to obtain reliable model results in predicting pesticide movement inthe unsaturated zone.     

Polybrominated diphenyl ethers in soils of the modern Yellow River Delta, China: occurrence, distribution and inventory

The Yellow River is the second largest river in China. In this study, the levels of polybrominated diphenyl ethers (PBDEs) in the modern Yellow River Delta (mYRD) were firstly reported. Twenty PBDE congeners in soil/sediment samples from mYRD were measured. The total PBDE concentrations ranged from non-detectable to 18 257 ng kg⁻¹ with a mean value of 836 ng kg⁻¹. BDE-209 was the dominant congener, accounting for ∼86.1-99.5% of the total PBDEs. The congener profiles of PBDEs with higher abundances of BDE-153 and BDE-183 were similar to those in sediment of the Bohai Sea, indicating that they shared similar sources. The concentrations and congener patterns varied among different regions. Higher levels of PBDEs were found in the middle area (MA), and more complicated congener compositions were also observed in the MA, whereas lower levels of PBDEs were found in the modern course (MC) and the old course (OC). Much more PBDEs were detected in the top layer (TL) soil where more congeners were also held compared to lower soil layers, implying that more PBDEs were emitted into this area in recent years/decades. Organic matter controlled the PBDE distribution in the soil. Soil in this area might be a source of BDE209 for the Bohai Sea.     

Comparison of batch, stirred flow chamber, and column experiments to study adsorption, desorption and transport of carbofuran within two acidic soils

Different methods (batch, column and stirred flow chamber experiments) used for adsorption and desorption of carbofuran studies were compared. All tested methods showed that the carbofuran adsorption was higher in the soil with the higher organic matter content, whereas the opposite behaviour was observed for the percentage of carbofuran desorbed. However, different methods have revealed some discrepancies in carbofuran adsorption/desorption kinetics. Although batch method showed interesting data on equilibrium experiments, such as a low heterogeneity for the carbofuran adsorption sites independent of soil organic matter content, it had some disadvantages for carbofuran adsorption/desorption kinetic studies. The disadvantages were related with the excessive limitations of this method on kinetics, i.e., no difference could be detected between different soils. However, with column and stirred flow chamber methods the carbofuran adsorption/desorption kinetics of different soils could be compared. Moreover, the absolute values of carbofuran adsorption/desorption and its rate were higher in the stirred flow chamber than in the batch and column experiments. Using stirred flow chamber experiments the carbofuran desorption was significantly faster than its adsorption, whereas carbofuran using column experiments they were similar. These discrepancies should be considered when the results obtained only with one method is discussed.     

Paraquat adsorption, degradation, and remobilization in tropical soils of Thailand

Paraquat adsorption, degradation, and remobilization were investigated in representative tropical soils of Yom River Basin, Thailand. Adsorption of paraquat in eight soil samples using batch equilibration techniques indicated that adsorption depended on soil characteristics, including exchangeable basic cations and iron content. Multiple regression analysis indicated significant contribution of exchangeable calcium percentage (ECP), total iron content (TFe) and exchangeable sodium percentage (ESP) to paraquat sorption (Q). ESP and TFe were significant at all adsorption stages, whereas ESP was significant only at the initial stage of paraquat adsorption. Adsorption studies using two soils representing clay and sandy loam textures showed that paraquat adsorption followed the Freundlich model, exhibiting a nonlinear sorption curve. Paraquat adsorption was higher in the clay soil compared to the sandy loam soil with Kf values of 787 and 18, respectively. Desorption was low with 0.04 to 0.17% and 0.80 to 5.83% desorbed in clay and sandy loam soil, respectively, indicating some hysteresis effect. Time-dependent paraquat adsorption fitted to the Elovich kinetic model indicated that diffusion was a rate-limiting process. Paraquat mobility and degradation studies conducted using both field and laboratory soil column experiments with clay soil showed low mobility of paraquat with accumulation only in the surface 0-5 cm layer under field conditions and in the 0-1 cm layer in a laboratory soil column experiment. Degradation of paraquat in soil was faster under field conditions than at ambient laboratory conditions. The degradation rate followed a first-order kinetic model with the DT50 at 36-46 days and DT90 around 119-152 days.     

Difference between selenite and selenate in selenium transformation and the regulation of cadmium accumulation in Brassica chinensis

Environmental Science and Pollution Research - Se can regulate Cd accumulation and translocation in plants; however, such effects can be controversial because of the differences in plant species...     

新疆某矿冶区周边土壤重金属生物有效性与生态风险评价

矿业活动对土壤系统良性运转带来较大的环境负荷,矿区周边土壤重金属污染风险评估是土壤污染防治和资源可持续开发的关键。在应用单因子污染指数法、潜在生态风险指数法、风险评价编码法(RAC),并结合空间分析和冗余分析手段的基础上,对新疆某矿冶区周边土壤重金属生物有效性和生态风险进行了系统研究。结果表明：研究区土壤As、Cu、Mn和Cd超标率分别为88%、38%、49%和24%;土壤Mn、Zn、As和Cd弱酸可溶态高值区主要集中在尾砂库和收砷房的附近区域。单因子污染指数评价揭示As和Cu污染累积较为严重。潜在生态风险评价显示,As、Cd和Cu生态风险较高,Mn为低生态风险。风险编码法(RAC)评价结果进一步揭示Mn和Cd具有显著的土壤迁移风险。冗余分析结果显示,空间异质性是影响土壤重金属弱酸可溶态含量变异的主要因素。土壤pH和重金属弱酸可溶态是影响潜在生态风险指数(RI)的2个重要因素。综合风险评价手段与多尺度分析方法的联合应用有助于提高区域风险评价的准确性。     

Oxalate and root exudates enhance the desorption of p,p'-DDT from soils

The abiotic desorption of p,p'-DDT from seven Chinese soils spiked with p,p'-DDT and the effects of oxalate at 0.001-0.1M and the root exudates of maize, wheat, and ryegrass were evaluated using batch experiments. Soil organic carbon played a predominant role in the retention of DDT. Oxalate significantly increased the desorption of p,p'-DDT, with the largest increments ranging from 11% to 54% for different soils. Oxalate addition also resulted in the increased release of dissolved organic carbon and inorganic ions from soils. Root exudates had similar effects to those of oxalate. Root exudates significantly increased DDT desorption from the soils, and the general trend was similar among the plant species studied for all the soils (p > 0.05). Low molecular weight dissolved organic carbon amendments caused partial dissolution of the soil structure, such as the organo-mineral linkages, resulting in the release of organic carbon and metal ions and thus the subsequent enhanced desorption of DDT from the soils. The enhancing effects of oxalate and root exudates on DDT desorption were influenced by the contents of soil organic carbon and dissolved organic carbon in soils.     

Sorption and desorption of the diketonitrile metabolite of isoxaflutole in soils

Isoxaflutole is a new pre-emergence corn herbicide that undergoes rapid conversion to a diketonitrile derivative (DKN) in soils. Sorption-desorption studies were conducted in five different soils varying in physical and chemical properties. A batch equilibration technique was used with total initial aqueous solution concentrations of DKN at 0.25, 0.75, 2.0, 8.0, 25, 75, 150, and 250 mg l(-1). After the sorption process, two subsequent desorptions were conducted with an equilibration period of 7 days. A high correlation existed between the desorption coefficient, K(Fd) and the organic matter content of soils (r(2)=0.844 for the first desorption and r(2)=0.861 for the second desorption), while the clay content did not greatly influence the desorption of DKN. Although the sorption of DKN was generally reversible, a sorption-desorption hysteresis was apparent in all soils. The site energy distribution curves emphasized the fact that DKN binds tightly to soils with higher organic matter content and greater proportion of DKN was retained by those soils     

Sorption and desorption kinetics of diuron,fluometuron, prometryn and pyrithiobac sodium in soils

Abstract

The sorption and desorption characteristics of four herbicides (diuron, fluometuron, prometryn and pyrithiobac‐sodium) in three different cotton growing soils of Australia was investigated. Kinetics and equilibrium sorption and desorption isotherms were determined using the batch equilibrium technique. Sorption was rapid (> 80% in 2 h) and sorption equilibrium was achieved within a short period of time (ca 4 h) for all herbicides. Sorption isotherms of the four herbicides were described by Freundlich equation with an r² value > 0.98. The herbicide sorption as measured by the distribution coefficient (K_d) values ranged from 3.24 to 5.71 L/kg for diuron, 0.44 to 1.13 L/kg for fluometuron, 1.78 to 6.04 L/kg for prometryn and 0.22 to 0.59 L/kg for pyrithiobac‐sodium. Sorption of herbicides was higher in the Moree soil than in Narrabri and Wee Waa soils. When the K_d values were normalised to organic carbon content of the soils (K_oC), it suggested that the affinity of the herbicides to the organic carbon increased in the order: pyrithiobac‐sodium < fluometuron < prometryn < diuron. The desorption isotherms were also adequately described by the Freundlich equation. For desorption, all herbicides exhibited hysteresis and the hysteresis was stronger for highly sorbed herbicides (diuron and prometryn) than the weakly sorbed herbicides (fluometuron and pyrithiobac‐sodium). Hysteresis was also quantified as the percentage of sorbed herbicides which is not released during the desorption step ω = [n_ad / n_de ‐1] x 100). Soil type and initial concentration had significant effect on ω. The effect of sorption and desorption properties of these four herbicides on the off‐site transport to contaminate surface and groundwater are also discussed in this paper.     

Sorption and desorption kinetics of diuron, fluometuron, prometryn and pyrithiobac sodium in soils

The sorption and desorption characteristics of four herbicides (diuron, fluometuron, prometryn and pyrithiobac-sodium) in three different cotton growing soils of Australia was investigated. Kinetics and equilibrium sorption and desorption isotherms were determined using the batch equilibrium technique. Sorption was rapid (> 80% in 2 h) and sorption equilibrium was achieved within a short period of time (ca 4 h) for all herbicides. Sorption isotherms of the four herbicides were described by Freundlich equation with an r2 value > 0.98. The herbicide sorption as measured by the distribution coefficient (Kd) values ranged from 3.24 to 5.71 L/kg for diuron, 0.44 to 1.13 L/kg for fluometuron, 1.78 to 6.04 L/kg for prometryn and 0.22 to 0.59 L/kg for pyrithiobac-sodium. Sorption of herbicides was higher in the Moree soil than in Narrabri and Wee Waa soils. When the Kd values were normalised to organic carbon content of the soils (Koc), it suggested that the affinity of the herbicides to the organic carbon increased in the order: pyrithiobac-sodium < fluometuron < prometryn < or = diuron. The desorption isotherms were also adequately described by the Freundlich equation. For desorption, all herbicides exhibited hysteresis and the hysteresis was stronger for highly sorbed herbicides (diuron and prometryn) than the weakly sorbed herbicides (fluometuron and pyrithiobac-sodium). Hysteresis was also quantified as the percentage of sorbed herbicides which is not released during the desorption step (omega = [nad/nde - 1] x 100). Soil type and initial concentration had significant effect on omega. The effect of sorption and desorption properties of these four herbicides on the off-site transport to contaminate surface and groundwater are also discussed in this paper.     

Adsorption of arsenate on soils. Part 2: modeling the relationship between adsorption capacity and soil physiochemical properties using 16 Chinese soils

An attempt has been made to elucidate the effects of soil properties on arsenate adsorption by modeling the relationships between adsorption capacity and the properties of 16 Chinese soils. The model produced was validated against three Australian and three American soils. The results showed that nearly 93.8% of the variability in arsenate adsorption on the low-energy surface could be described by citrate-dithionite extractable Fe (Fe(CD)), clay content, organic matter content (OM) and dissolved organic carbon (DOC); nearly 87.6% of the variability in arsenate adsorption on the high-energy surface could be described by Fe(CD), DOC and total arsenic in soils. Fe(CD) exhibited the most important positive influence on arsenate adsorption. Oxalate extractable Al (Al(OX)), citrate-dithionite extractable Al (Al(CD)), extractable P and soil pH appeared relatively unimportant for adsorption of arsenate by soils.     

Effects of pH, organic acids, and competitive cations on mercury desorption in soils

The effects of pH, organic acids, and competitive cations on Hg(2+) desorption were studied. Three representative soils for rice production in China, locally referred to as a yellowish red soil (YRS), purplish clayey soil (PCS), and silty loam soil (SLS) and classified as Gleyi-Stagnic Anthrosols in FAO/UNESCO nomenclature, were, respectively, collected from Jiaxin County, Deqing County, and Xiasha District of Hangzhou City, Zhejiang Province. Most of the added Hg(2+) was adsorbed at low initial concentrations (<2 mg l(-1)). Desorption of the adsorbed Hg(2+) in 0.01M KCl (simulating soil solution) was minimal, but was significantly enhanced by the change of pH, and the presence of organic acids or competitive cations. The desorption of Hg(2+) in the soils decreased with pH from 3.0 to 5.0, leveled off at pH 5.0-8.0, but increased with pH from 7.0 to 9.0. The presence of organic ligands enhanced Hg(2+) desorption in the soils except for YRS, in which the addition of tartaric, malic, or oxalic acid reduced Hg(2+) desorption at low concentrations (<10(-4)M), but Hg(2+) desorption generally increased with organic acid concentration. Citric acid was most effective in increasing Hg(2+) desorption, followed by tartaric acid and malic acid; and oxalic acid was the least effective. Desorption of adsorbed Hg(2+) increased with increasing concentrations of added Cu(2+) or Zn(2+). Applied Cu(2+) increased Hg(2+) desorption more than Zn(2+) at the same loading rate. CAPSULE: The effects of organic acids and competitive cations on Hg desorption in soil-water system are related to their concentrations, basic chemical properties, and soil properties.     

Technological applications of organo-montmorillonites in the removal of pyrimethanil from water: adsorption/desorption and flocculation studies

Environmental Science and Pollution Research - Pyrimethanil (2-aniline-4, 6-dimethylpyrimidine, PRM) is used in fruit packing plants to control fungal infections and diseases. The effluents greatly...     

Polybrominated diphenyl ethers in background surface soils from the Yangtze River Delta (YRD), China: occurrence,sources, and inventory

Purposes  

Very few data for polybrominated diphenyl ethers (PBDEs) were available in the Yangtze River Delta (YRD), one of the most developed and urbanized region in China. In this study, Chongming Island, located at the estuary of the Yangtze River, was selected as background area to investigate the occurrence, sources, and inventory of PBDEs.     

Adsorption,desorption, potential and selective distribution op heavy metals in selected soils of japan

Abstract

Adsorption, desorption, potential and selective distribution of Cu, Zn, Cd, Pb and Ni were investigated in three typical soils of Japan under flooded condition.

The results indicate that the sorption of all heavy metals was linear upto the maximum concentration (500 μg/g soil) employed in the present studies in all the soils. The magnitude of sorption in general was in the order of Pb > Cu > Zn > Cd > Ni. The adsorption coefficients showed wide variations among different soils as well as metal ions. The hysteresis of sorption and desorption by KNO₃ was well pronounced for both the metal ions and the soils. The desorption rate was greater than the fixation rate indicating the predominance of the chemosorption over physical processes. The major portion of sorbed metals were retained in the unextractable form, which over all accounted for more than 50% of the sorbed metals.