微囊藻毒素MC-RR在农田土壤中吸附行为研究

采用批处理实验研究了典型微囊藻毒素MC-RR(10~400μg·L-1)在农田土壤(水稻土、赤红壤和咸田土)中的吸附动力学和热力学特征,并探讨土壤理化性质对其吸附行为的影响.结果表明,MC-RR在农田土壤中的吸附均于4 h内达到平衡,吸附动力学均符合拟二级动力学方程(R20.994),液膜扩散是主要控速过程;各温度下(15、25、35℃)MC-RR吸附等温线均符合Langmuir方程(R20.827).水稻土吸附MC-RR主要为自发放热的物理吸附过程,其吸附能力随温度升高而降低;赤红壤和咸田土吸附MC-RR主要为自发吸热的化学吸附过程,其吸附能力随温度升高而增强.土壤粘粒矿物和有机质含量显著影响其对MC-RR的吸附能力,粘粒矿物含量越高,有机质含量越低,MC-RR吸附能力越强.MC-RR在有机质含量较高的水稻土中难吸附,而在有机质含量较低的赤红壤和粘土含量较高的咸田土中易吸附.     

工业腐殖酸提纯前后对泰乐菌素的吸附特性

本文采用稀碱法对购买的工业腐殖酸进行了提纯,研究了腐殖酸提纯前后对泰乐菌素的吸附特性,并对其吸附机制进行了初步的探讨.研究结果表明:在对腐殖酸提纯之后,其C、H、O、N、S的含量明显增加,灰分含量显著减小.腐殖酸经提纯后对泰乐菌素的吸附明显增强,在24h可以完全达到吸附平衡,其吸附动力学曲线可以用拉格朗日二级动力学方程和颗粒扩散模型较好的拟合;吸附等温线可以用线性吸附模型和Freundlich吸附模型较好的拟合;且提纯后的腐殖酸对泰乐菌素的吸附随着溶液的p H值和离子强度增加而逐渐减小.综上,推测腐殖酸对泰乐菌素的吸附机制可能以疏水性分配、氢键作用和离子交换作用为主.     

Nature of the action of a compost from olive mill wastewater on Cu sorption by soils

The reaction of two soils that have received composted OMW as manure with Cu solutions is studied. The data were fitted into a multi‐reaction model which considers both reversible and irreversible adsorption sites, and an ‘instantaneous’ fraction. The presence of composted OMW caused a strong increase in the distribution coefficient describing the instantaneous fraction, and the disappearance of the irreversible fraction. This behaviour was attributed to blocking of some sorbing surfaces by the organics, and to new surfaces present in the compost. These effects can have some environmental significance from the viewpoint of Cu mobility.     

黑碳对土壤中农药呋喃丹吸附与解吸行为的影响

为了考察黑碳对土壤中呋喃丹吸附与解吸行为的影响,选取小麦秸秆,分别在250℃、450℃和850℃下制备黑碳,测定了黑碳的比表面积和孔体积;采用批处理振荡法测定了呋喃丹在人工添加黑碳土壤中的吸附-解吸行为.结果表明,随制备温度升高,黑碳的比表面积、孔体积和微孔率增大;人工添加黑碳的土壤对呋喃丹的吸附容量和吸附强度随黑碳添加量增加而逐步增加,吸附和解吸等温线的非线性也逐步明显.添加高温制备黑碳的土壤比添加低温制备黑碳的土壤吸附容量、吸附和解吸的非线性均增加.吸附农药的解吸迟滞作用与土壤中黑碳的质量分数密切相关,添加高温制备黑碳的土壤解吸迟滞现象明显.因此,土壤中添加黑碳在一定程度上保证了土壤使用的安全性.     

Al-CTMAB复合膨润土同时吸附处理水中菲和磷酸根

用AlCl₃和溴化十六烷基三甲基铵(CTMAB)共同改性制得无机-有机复合膨润土Al-CTMAB-Bent,并研究其同时吸附处理水中菲和PO₄^3-的性能.结果表明,在菲和PO₄^3-的初始浓度分别为1 mg/L和5 mg/L(以P计)、水土比为800∶1时,Al-CTMAB-Bent对菲和PO₄^3-的去除率分别为96.3%和90.2%.Al-CTMAB-Bent沉降性能良好,沉降1 h后剩余浊度比相应的有机膨润土下降81.4%,为解决实际污水处理中有机膨润土固-液分离难题提供依据.     

天然土壤有机质中菲的分配行为

天然土壤吸附不同初始浓度的菲后,提取胡敏酸组分(包括胡敏酸和富里酸),通过计算得到胡敏素组份所吸附的菲,用以研究菲在2种组份中的动态吸附/分配行为,以及初始浓度的影响,并利用Freundlich式进行拟合.结果表明:天然土壤中菲的吸附/分配过程表现出分阶段特征:从最初的快吸附至48 h左右达到转折点,然后进入慢吸附过程.在快吸附至转折点阶段,胡敏酸组分中菲的吸附比例(吸附量与初始量之比)出现先升后降的波动,可归因于初始时段矿物表面吸附、胡敏素竞争吸附的影响.在慢吸附阶段,胡敏酸中菲的吸附比例变化很小,菲初始浓度的影响也不大;而对于胡敏素组份,低初始浓度条件下菲的吸附比例明显大于高初始浓度条件,并呈现逐步增加的趋势,表明胡敏素组份是慢吸附的主要发生域.模型参数拟合结果显示:胡敏酸、全土、胡敏素吸附的非线性程度依次增加,并随时间逐渐加强.在吸附/分配的动力学过程中,胡敏酸和胡敏素分阶段不同的变化特征反映出土壤有机质组分异质性对非线性吸附行为的影响.     

沉积物与水间相互作用的研究进展

本文综述了沉积物／水之间的相互作用的研究进展,主要讨论了污染物在沉积物／水界面间的物质传输：水体中污染物在颗粒物上的吸附作用;与沉积物相关的水质、健康和管理等方面的问题     

Kinetics and isotherm modeling of azoxystrobin and imidacloprid retention in biomixtures

The paper reports the kinetics and adsorption isotherm modeling for imidacloprid (IMIDA) and azoxystrobin (AZOXY) in rice straw (RS)/corn cob (CC) and peat (P)/compost (C) based biomixtures. The pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intraparticle diffusion models were used to describe the kinetics. The adsorption data were subjected to the Langmuir and the Freundlich isotherms. Results (r²_Adj values) suggested that the modified Elovich model was the best suited to explain the kinetics of IMIDA sorption while different models explained AZOXY sorption kinetics in different biomixtures (PFO in RS?+?C and RS?+?P; PSO in CC?+?P and Elovich in CC?+?C). Biomixtures varied in their capacity to adsorb both pesticides and the adsorption coefficient (K_d) values were 116.8–369.24 (AZOXY) and 24.2–293.4 (IMIDA). The Freundlich isotherm better explained the sorption of both pesticides. Comparison analysis of linear and nonlinear method for estimating the Freundlich adsorption constants was made. In general, r²_Adj values were higher for the nonlinear fit (AZOXY?=?0.938–0.982; IMIDA?=?0.91–0.970) than the linear fit (AZOXY?=?0.886–0.993; IMIDA?=?0.870–0.974) suggesting that the nonlinear Freundlich equation better explained the sorption. The rice straw-based biomixtures performed better in adsorbing both the pesticides and can be used in bio-purification systems.     

Leaching and sorption of neonicotinoid insecticides and fungicides from seed coatings

Seed coatings are a treatment used on a variety of crops to improve production and offer protection against pests and fungal outbreaks. The leaching of the active ingredients associated with the seed coatings and the sorption to soil was evaluated under laboratory conditions using commercially available corn and soybean seeds to study the fate and transport of these pesticides under controlled conditions. The active ingredients (AI) included one neonicotinoid insecticide (thiamethoxam) and five fungicides (azoxystrobin, fludioxonil, metalaxyl, sedaxane thiabendazole). An aqueous leaching experiment was conducted with treated corn and soybean seeds. Leaching potential was a function of solubility and seed type. The leaching of fludioxonil, was dependent on seed type with a shorter time to equilibrium on the corn compared to the soybean seeds. Sorption experiments with the treated seeds and a solution of the AIs were conducted using three different soil types. Sorption behavior was a function of soil organic matter as well as seed type. For most AIs, a negative relationship was observed between the aqueous concentration and the log K_oc. Sorption to all soils tested was limited for the hydrophilic pesticides thiamethoxam and metalaxyl. However, partitioning for the more hydrophobic fungicides was dependent on both seed type and soil properties. The mobility of fludioxonil in the sorption experiment varied by seed type indicating that the adjuvants associated with the seed coating could potentially play a role in the environmental fate of fludioxonil. This is the first study to assess, under laboratory conditions, the fate of pesticides associated with seed coatings using commercially available treated seeds. This information can be used to understand how alterations in agricultural practices (e.g., increasing use of seed treatments) can impact the exposure (concentration and duration) and potential effects of these chemicals to aquatic and terrestrial organisms.