菲在渤海湾入海河流与河口沉积物上的吸附-解吸行为

采用批量实验方法,研究了菲(Phe)在渤海湾入海河流与河口沉积物上的吸附-解吸过程,以及吸附参数与沉积物有机质性质之间的相关关系.结果表明,Phe在所有沉积物上的吸附和解吸等温线均能由线性分配模型和Freundlich模型很好地拟合.其中,线性分配系数KD值变化在58～743L·kg-1之间,与TOC、TN、DOC、Phe、C/N和DOC/TOC之间呈现显著正相关关系.Freundlich吸附能力参数KF和KFOC值分别在75～367μg1-N·kg-1·LN和2253～34743μg1-N·kg-1·LN之间,均与DOC/TOC呈现显著负相关关系,而与其它有机质参数之间相关性不显著.相比较而言,大多数沉积物的解吸等温线用Freundlich模型拟合的效果更好,并且具有明显的解吸滞后现象.有机质的含量和性质均是影响Phe在沉积物上吸附-解吸的重要因素.对于频繁受到人类活动影响的河流沉积物,溶解性有机质的影响就更为重要.     

海河沉积物对菲的吸附解吸行为研究

采用北运河坝河断面、海河干流邓善沽断面及葛沽镇断面表层沉积物及南开花园土为吸附剂,以菲为吸附质进行一系列吸附动力学和吸附-解吸平衡实验研究。结果表明,菲在各颗粒物上的吸附动力学过程,在0-4h内基本可达吸附平衡,刚开始吸附速率很快,然后迅速降低,并逐渐稳定;菲在各颗粒物上的等温平衡吸附可用线性等温线方程及Freundlich方程较好的拟合;不同来源颗粒物对菲的吸附能力随颗粒物中有机质含量增加而增强;葛沽镇颗粒物经高温灼烧处理后,其吸附能力明显降低;各天然颗粒物及不同温度灼烧处理的颗粒物对菲的解吸行为存在不同程度的滞后,灼烧颗粒物的滞后性远远大于原颗粒物,颗粒物中的有机质组分及性质对菲的解吸滞后有重要影响     

Sorption–desorption of imidacloprid onto a lacustrine Egyptian soil and its clay and humic acid fractions

Sorption–desorption of the insecticide imidacloprid 1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine onto a lacustrine sandy clay loam Egyptian soil and its clay and humic acid (HA) fractions was investigated in 24-h batch equilibrium experiments. Imidacloprid (IMDA) sorption–desorption isotherms onto the three sorbents were found to belong to a non-linear L-type and were best described by the Freundlich model. The value of the IMDA adsorption distribution coefficient, Kd_ads, varied according to its initial concentration and was ranged 40–84 for HA, 14–58 for clay and 1.85–4.15 for bulk soil. Freundlich sorption coefficient, Kf_ads, values were 63.0, 39.7 and 4.0 for HA, clay and bulk soil, respectively. The normalized soil Koc value for imidacloprid sorption was ～800 indicating its slight mobility in soils. Nonlinear sorption isotherms were indicated by 1/n_ads values <1 for all sorbents. Values of the hysteresis index (H) were <1, indicating the irreversibility of imidacloprid sorption process with all tested sorbents. Gibbs free energy (ΔG) values indicated a spontaneous and physicosorption process for IMDA and a more favorable sorption to HA than clay and soil. In conclusion, although the humic acid fraction showed the highest capacity and affinity for imidacloprid sorption, the clay fraction contributed to approximately 95% of soil-sorbed insecticide. Clay and humic acid fractions were found to be the major two factors controlling IMDA sorption in soils. The slight mobility of IMDA in soils and the hysteresis phenomenon associated with the irreversibility of its sorption onto, mainly, clay and organic matter of soils make its leachability unlikely to occur.     

Effect of lipids on sorption/desorption hysteresis in natural organic matter

The chemical composition and physical conformation of natural organic matter (NOM) play a major role in regulating its capacity to retain hydrophobic organic compounds. Naphthalene and phenanthrene were used to study the correlations between sorption/desorption isotherm nonlinearity and compositional data obtained from quantitative ¹³C solid-state DPMAS NMR spectroscopy for soil and peat organic matter with or without lipids. Sorption experiments were conducted using a batch equilibration method. Desorption experiments were carried out immediately following the sorption experiments by three successive decant-refill cycles. Hysteresis was observed in all samples. Nonlinear sorption behavior was increased by removal of lipids from the NOM. The hysteresis index, obtained from the ratio of the Freundlich exponents (N values) for the desorption and sorption isotherms, was lower in the lipid-extracted NOM samples than in the same samples without lipid extraction. The relationship between the extent of hysteresis and the characteristics of the ¹³C DPMAS NMR spectra indicates that altering NOM composition through lipid extraction not only increased the proportion of aromatic-C content, but also increased sorption/desorption hysteresis. Our data also suggest that the hysteresis index is negatively related to aromaticity.     

动态膜压法测定江、污混合水体中有机物含量的探讨

用双驱动动态膜压仪测定江、污混合水中有机物含量。通过测定白龙港污水和长江水混合后的膜压和滞回环面积，用它们与相应的经典法CODCr作图，获得了滞回环面积和CODCr之间良好地线性关系，表明用动态膜压法可快速测定混合水中的有机物含量，不须加任何试剂，不会产生二次污染。同时，对实验结果进行了初步的机理探讨。     

Effects of β-cyclodextrin on adsorption and desorption of carbofuran in soils of divergent texture

Laboratory studies were conducted to determine the adsorption/desorption equilibrium of carbofuran between four divergently textured soils and distilled water and an aqueous solution of 0.01?mol?L^?1 β-cyclodextrin using a batch equilibrium technique. The determined adsorption isotherms for silt loam soils were of L-shaped, for sandy loam soil S-shaped, in agreement with a Freundlich isotherm. In the presence of β-cyclodextrin, the adsorption of carbofuran to the four soils was lower than with distilled water. Positive hysteresis was observed in all soils with distilled water, negative hysteresis when using a solution of β-cyclodextrin as desorbent. The results indicate the potential use of β-cyclodextrin for remediation of pesticide-contaminated soils.     

Sorption and desorption hysteresis of organic contaminants by kerogen in a sandy aquifer material

Sorption and desorption hysteresis of 1,2-dichlorobenzene, 1,3,5-trichlorobenzene, naphthalene, and phenanthrene were investigated for the Borden aquifer material with total organic carbon of 0.021% and the isolated natural organic matter (NOM). The isolated NOM is a kerogen type of organic matter with relatively low maturation degree and contained many different types of organic matters including vitrinite particles. The modified Freundlich sorption capacities (logK^′_f and logK^′_foc) are very close for the sorption of the four solutes by the isolated NOM and the original sand, respectively. Isotherm non-linearity (n value) and hysteric behaviors are related to solute molecular properties (e.g. K_ow and molecular size). Kerogen encapsulated by inorganic matrices in the original aquifer may not be accessed fully by solutes. The larger the hydrophobic organic chemical (HOC) (hydrophobic organic contaminant) molecule is, the lower accessibility of the HOC to kerogen. This study disputes widely held hypothesis that sorption to mineral surfaces may play a major role in the overall sorption by low TOC (e.g. 0.1% by mass) geomaterials such as Borden sand. It also demonstrates the importance of the condensed NOM domain, even at very low contents, in the sorption and desorption hysteresis of HOCs in groundwater systems.     

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。     

Comparative sorption,desorption and leaching potential of aminocyclopyrachlor and picloram

Sorption and desorption of aminocyclopyrachlor (6-amino-5-chloro-2-cyclopropylpyrimidine-4-carboxylic acid) were compared to that of the structurally similar herbicide picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) in three soils of differing origin and composition to determine if picloram data is representative of aminocyclopyrachlor behavior in soil. Aminocyclopyrachlor and picloram batch sorption data fit the Freundlich equation and was independent of concentration for aminocyclopyrachlor (1/n = 1), but not for picloram (1/n = 0.80–0.90). Freundlich sorption coefficients (K _f) for aminocyclopyrachlor were lowest in the eroded and depositional Minnesota soils (0.04 and 0.12 μmol ^(1–1/n) L^1/n kg^?1) and the highest in Molokai soil (0.31 μmol ^(1–1/n) L^1/n kg^?1). For picloram, K _f was lower in the eroded (0.28 μmol ^(1–1/n) L^1/n kg^?1) as compared to the depositional Minnesota soil (0.75 μmol ^(1–1/n) L^1/n kg^?1). Comparing soil to soil, K _f for picloram was consistently higher than those found for aminocyclopyrachlor. Desorption of aminocyclopyrachlor and picloram was hysteretic on all three soils. With regard to the theoretical leaching potential based on groundwater ubiquity score (GUS), leaching potential of both herbicides was considered to be similar. Aminocyclopyrachlor would be ranked as leacher in all three soils if t_1/2 was > 12.7 days. To be ranked as non-leacher in all three soils, aminocyclopyrachlor t_1/2 would have to be <3.3 days. Calculated half-life that would rank picloram as leacher was calculated to be ～15.6 d. Using the current information for aminocycloprachlor, or using picloram data as representative of aminocycloprachlor behavior, scientists can now more accurately predict the potential for offsite transport of aminocycloprachlor.     

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.