微塑料对水中铜离子和四环素的吸附行为

微塑料作为载体可与水中重金属、抗生素结合进而形成复合污染,这改变了污染物原有的环境行为与危害性.微塑料与重金属及抗生素间的作用途径与机制是评价其环境风险及毒理学机制的前提.目前有关微塑料与重金属及抗生素间的相互作用机制尚不清晰.以高密度聚乙烯(HDPE)和通用级聚苯乙烯(GPPS)颗粒作为代表,研究了微塑料在单一体系和复合体系中对Cu~(2+)和四环素的吸附行为,并就相关机制进行了探讨.结果表明,单一体系中,GPPS和HDPE分别对TC和Cu~(2+)表现出更大的平衡吸附量;复合体系中,GPPS对Cu~(2+)和TC的平衡吸附量均大于HDPE,且2种微塑料的吸附能力均较单一体系有所提高.准二级动力学模型对微塑料吸附过程的描述更为合理,吸附过程可划分为表面吸附和孔内扩散2个阶段.Langmuir等温吸附模型较Freundlich等温吸附模型更符合实验情形.单一体系中,GPPS和HDPE对Cu~(2+)和TC的饱和吸附量分别为0.178、 0.257、 0.334和0.194μmol·g~(-1),而在复合体系中,相应的饱和吸附量则分别增大至0.529、 0.411、 0.471和0.341μmol·g~(-1).表面形态特征及化学官能团的不同是导致GPPS和HDPE吸附行为差异的主要原因.体系pH影响微塑料和吸附对象的存在形态及表面电性,继而影响平衡吸附量.环境温度在15～35℃范围时,提高温度不利于微塑料的吸附.Cu~(2+)和TC在共存条件下可产生协同效应,络合物的形成及相互间的桥接作用使得二者更易于被微塑料吸附.     

三种萘系物在改性泥炭上的低温吸附与解吸特性

研究了柴油污染场地地下水中3种典型多环芳烃污染物萘、1-甲基萘、2-甲基萘在改性泥炭上的吸附与解吸行为。结果表明:10℃低温条件下,Freundlich模型能够较好的描述萘、1-甲基萘、2-甲基萘在改性泥炭上吸附与解吸行为,并呈现明显的非线性特征。萘系物Koc、Kf大小顺序为2-甲基萘>1-甲基萘>萘,且均随着污染物Kow增大而增大;萘系物在改性泥炭上均存在明显解吸滞后现象(HI>0.21),解吸滞后程度大小顺序为2-甲基萘>1-甲基萘>萘。研究结果表明:随着萘环上甲基数量增加或α、β碳位序变化,萘系物在泥炭上分配及吸附能力变大,相应,解吸速率降低,解吸滞后程度变大。     

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.     

Tylosin Sorption to Silty Clay Loam Soils,Swine Manure,and Sand

The objectives of this study were to assess sorption and desorption of tylosin, a macrolide antimicrobial chemical used in swine, cattle, and poultry production, in three silty clay loam soils of South Dakota and compare soil sorption to sand and manure sorption. The silty clay loam soils, from a toposequence in eastern South Dakota, standardized sand samples, and swine manure were used in 24-h batch sorption studies with tylosin concentrations ranging from 25 to 232 μ mole/L. Desorption from soil was conducted over a four-day period. Partition coefficients, based on the Freundlich isotherm (K _f ) or K _d values, were calculated. K _f values for the silty clay loams were similar, not influenced by landscape position, and averaged 1350 with isotherm slopes ranging from 0.85 to 0.93. K _f values for sand were dependent on solution/sand ratios and pH, ranging from 1.4 to 25.1. K _d values of manure were dependent on the solution type and ranged from 840 L/kg with urine to about 175 L/kg when sorbed from water. Desorption of tylosin from each soil over the four-day period was < 0.2% of the amount added. The soils' high K _f values and low desorption amounts suggest that once tylosin is in these soils, leaching to lower depths may not occur. However, this does not preclude runoff with soil eroded particles. If tylosin reaches a sand aquifer, through bypass flow or other mechanism(s), movement in the aquifer most likely would occur.     

原煤及富碳沉积物对疏水性有机污染物吸附解吸研究进展

疏水性有机污染物（HOCs）是环境中具有较大的辛醇/水分配系数(〖WTBX〗Kow〖WTBZ〗)的一类持久性有机污染物（POPs），吸附解吸过程是环境中HOCs迁移转化的重要途径之一。煤是近年来发现的在土壤及沉积物中非线性吸附特征的重要吸附剂之一，通过阐述原煤及富碳沉积物对HOCs吸附解吸机理，并重点分析影响原煤及富碳沉积物对HOCs吸附解吸过程的因素，包括吸附剂和吸附质本身，pH值、盐度和离子强度等环境因子，试途探究煤对HOCs吸附解吸的本质。由于煤的有机质含量、有机碳组成和空间结构等物理化学性质都明显不同于天然土壤和沉积物，因而对HOCs的吸附解吸过程也具有特殊性（如吸附过程一般为非线性，解吸过程的滞后性）。有关煤对HOCs的吸附解吸机理在微观分子角度的探讨、煤与吸附解吸过程中其他影响因子对反应体系的影响、煤对HOCs降解的环境风险评价等的研究还较少，今后需加强对这些方面的研究     

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.     

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.