~(14)C-红霉素在土壤中的吸附解吸和淋溶特性

为探究抗生素在土壤中的吸附、解吸及其淋溶迁移行为,采用振荡平衡法和土柱淋溶法分别研究了~(14)C-红霉素在7种不同类型土壤中的吸附、解吸和淋溶特性。吸附试验结果表明,红霉素在7种土壤中的等温吸附-解吸规律满足Freundlich、Langmiur和线性模型,相关系数R~2为0.9810~0.9999。土壤性质对红霉素的吸附性能有显著影响,7种土壤中吸附常数Kf值依次为S_6S_3S_7S_5S_2S_4S_1。相关性分析表明,Kf值与土壤有机质含量呈正相关(r=0.956,P0.01),而与土壤pH值、阳离子交换量、粘粒含量无显著相关性。红霉素在7种土壤中的吸附自由能变化均小于40 k J·mol~(-1),表明其在土壤中的吸附机制主要为物理吸附。红霉素在7种土壤中的解吸均存在明显的滞后现象。土柱淋溶试验结果表明,红霉素在7种土壤中淋溶性均较弱,66.86%~92.53%的量集中在0~5 cm表层土壤中。总体上红霉素在土壤S_1、S_2和S_4中的淋溶能力最强,其次为S_3、S_5和S_7,在S_6中最不易淋溶,与吸附试验结果相一致。综合红霉素在土壤中的吸附、解吸和淋溶特性,红霉素在土壤中较难淋溶,使其可能在土壤介质中积累,存在一定的环境污染风险。本研究结果对评估环境安全性具有重要意义。     

丁吡吗啉在土壤中的吸附及淋溶特性

化学农药在土壤中的吸附和淋溶特性是评价其环境行为的重要指标,也是新农药登记必须提供的环境影响资料。本文分别采用振荡平衡法、土壤薄层层析法和土柱淋溶法研究了丁吡吗啉在不同土壤中的吸附和淋溶特性。结果表明,丁吡吗啉在3种供试土壤上的吸附规律可以较好地用FreundLich方程描述,吸附常数Kd在10.42~37.72mL.g-1之间,在砂土中较难被吸附,在壤土和粘土中属中等吸附。丁吡吗啉在3种供试土壤中不易移动或不移动,3种土柱淋溶试验的结论均为难淋溶。根据综合试验结果,对相关影响因素进行了讨论,认为影响丁吡吗啉在土壤中吸附性的主要因素为土壤有机质含量和土壤粘粒含量,影响淋溶特性的主要因素为土壤吸附和丁吡吗啉在水中的溶解度。     

2,4-D丁酯的水解与光解特性研究

通过室内模拟试验,研究2,4-D丁酯在不同pH值和温度下的水解动态和在有机溶剂中的光解特性。结果表明,2,4-D丁酯的水解与光解均符合一级动力学方程。在pH7以下的缓冲溶液中,2,4-D丁酯的水解反应十分缓慢,但在碱性溶液中其水解速率加快。25℃下2,4-D丁酯在pH5、7和9的缓冲溶液中的水解半衰期分别为23.5、5.8d和10.7min。2,4-D丁酯的水解速率随温度升高而增加,在温度为15、25℃和35℃的pH7缓冲溶液中的水解半衰期分别为21.5、5.8、3.9d,平均温度效应系数为2.57。2,4-D丁酯水解反应的活化能与温度之间无明显相关性,而活化熵与温度呈显著相关性。2,4-D丁酯的水解主要由活化熵所驱动。采用GC-MS技术对2,4-D丁酯水解产物进行鉴定,确定水解产物主要是2,4-二氯苯氧乙酸和2,4-二氯苯酚。2,4-D丁酯在正己烷中光解速率比在甲醇中快,在丙酮中几乎不发生光解,其光解速率随浓度的升高而减慢。     

2,4-D 对铜在乌栅土胶体和红壤胶体上吸附的影响

应用批平衡法研究了农药2,4-D对Cu在乌栅土胶体和红壤胶体上吸附的影响。结果表明,Cu在两种土壤胶体上的吸附等温线均符合Langmuir方程,Cu在乌栅土胶体上的吸附量较其在红壤胶体上的吸附量要高;在pH3.0～6.7范围内,两种土壤胶体对Cu的吸附量均随溶液pH的升高而升高。2,4-D增加了Cu在土壤胶体上的吸附,2,4-D的浓度越高,Cu的吸附量越大,这主要是由于2,4-D的存在显著增加了平衡液的pH,从而增加了土壤胶体表面所带负电荷量。     

土霉素在土壤中的垂直迁移及其影响因素研究

采用土柱淋溶法,研究了土霉素在土壤中的垂直迁移特性,探讨了不同土壤类型、淋溶体积、淋溶液pH值、施药量等因素对土霉素在土壤中淋溶迁移的影响。结果表明,在红壤、黑钙土、赤红壤3种不同类型的土样中,土霉素的迁移深度为：赤红壤〉红壤〉黑钙土;土霉素主要富集在土壤表层,其含量随土壤深度增加而明显降低;同一深度的土壤中土霉素含量随着淋溶液体积的增加而增大,随pH值增大而减小;土霉素在土层中的含量分布、淋溶深度与其施药量均呈正相关;当淋溶液中含有一定量的土霉素溶液时,土霉素在土壤中的迁移深度明显增加。     

新农药哌虫啶在三种典型土壤中的吸附与淋溶研究

应用振荡平衡法和柱淋洗法研究了哌虫啶在红壤、棕壤和黑土3种典型土壤中的吸附和淋溶特性,并探讨了3种土壤改良剂对其淋溶的影响。结果表明:哌虫啶在黑土、红壤和棕壤中的吸附平衡时间分别为12、12和9 h,分配系数Kd分别为23.16、11.24和4.68,吸附常数Kf分别为22.03、11.69和5.05,KOC值分别为1 619、2 094和495,吸附自由能值分别为-16.96、-17.59和-14.02 k J mol-1,Freundlich和线性等温吸附模型均能较好地描述哌虫啶在土壤中的吸附过程,其吸附能力顺序分别为黑龙江黑土福建红壤山东棕壤。哌虫啶在3种供试土壤中淋溶性存在差异,在棕壤中迁移性最强,随着施药量的增加,其淋出率也略有提高,但3个不同水平施药量差异不显著。在黑土中迁移性最弱,红壤和黑土中的哌虫啶残留量随着土壤深度的增加逐渐降低。土壤中添加0.5%的活性炭、腐殖酸和草炭能显著地降低农药哌虫啶在土壤中的淋溶性,减少对地下水的污染风险。     

异丙隆在土壤中的淋溶迁移及其影响因素研究

采用室内土壤淋洗柱法,以黄褐土、砂姜黑土和水稻土为供试土壤,研究了异丙隆在土壤中的淋溶迁移行为,探讨了淋溶水量、淋溶水pH值、施药量和添加外源木炭等因素对异丙隆在土壤中淋溶迁移的影响。结果表明,不同土壤中异丙隆淋出率为黄褐土〉砂姜黑土〉水稻土;淋溶水量与异丙隆的淋出率呈正相关,且对淋溶后异丙隆在土层中的分布有明显影响;用不同pH值的淋溶水时,异丙隆的淋出率为pH5〉pH9〉pH7;施加不同药量时,异丙隆的淋出率为10mg〉5mg〉20mg;异丙隆的淋出率随外源木炭添加量的增大而减小,而异丙隆在土壤柱中的滞留量则随着木炭添加量增大而增大,提示添加外源木炭可明显减少异丙隆在土壤中的淋出率,降低异丙隆在土壤中的淋溶深度。     

温度对土壤吸附有机肥中可溶性有机碳、氮的影响

可溶性有机碳、氮(Soluble organic carbon or nitrogen,SOC和SON)可被土壤吸附.土壤可溶性有机碳、氮组分复杂,土壤对可溶性有机物吸附的不均一性会导致可溶性有机物组分的变化,大部分疏水性化合物被吸附,而亲水性化合物被释放进入溶液中[1].因此,可溶性有机碳、氮在土壤中的吸附,直接影响其在土壤-水系统中的迁移和行为[2-3].林地土壤中含有相当数量的可溶性有机养分,因此,关于林地土壤对可溶性有机养分的吸附特性,国外研究者已开展了不少研究.研究表明,可溶性有机碳吸附特性与土壤性质如pH、表面积、有机碳、铁铝氧化物和黏粒含量等因素有关[4-5].关于农业土壤对可溶性有机碳的吸附特性的影响,国内也开展了一些研究,主要集中在pH、铁铝氧化物含量等对吸附影响方面[6-9].     

非饱和土壤中氟离子迁移规律实验研究

采用实验室土柱法,在3种pH(4.0,5.5,7.5)淹灌和降雨条件下,研究了非饱和土壤中氟离子的迁移转化。结果表明:不同pH降雨、淹灌条件下,随着淋洗时间的增加,淋滤液中的可溶性氟含量逐渐增大,特别是pH5.5和pH7.5淋滤液中氟的变化规律明显。淹灌条件下淋滤液中氟含量低于降雨条件下淋滤液的氟含量。淋溶前后土壤表层的氟含量变化明显,淋滤后表层土壤表现为淋溶状态。土壤pH值是影响土壤氟存在形态的重要因素之一,对土壤可溶性氟有着重要的影响。     

不同土壤对Cr吸附的动力学特征

该文采用振荡平衡法比较了来自中国15个省区16种土壤对Cr(Ⅵ)的吸附及其动力学特性,并探讨了土壤pH值、阳离了交换量、黏粒含量和有机质对Cr(Ⅵ)吸附及其动力学参数的影响.结果表明:具有较低土壤pH值和较高物理黏粒含量的土壤对Cr(Ⅵ)具有较人的表观吸附量,而土壤阳离子交换量和有机质因素对土壤Cr(Ⅵ)的表观吸附量影响较小.酸性土壤对Cr(Ⅵ)吸附能力较强,可以采用一级动力学方程和抛物线方程描述Cr(Ⅵ)在酸性土壤中的动力学行为,且土壤的表观吸附速率和平衡时的吸附量与土壤的pH值呈显著(p<0.05)负相关关系,而与物理黏粒含量旱显著(p<0.01)正相关关系;而碱性土壤对Cr(Ⅵ)吸附能力较小,很难用动力学方程描述其吸附动力学特性.可见,土壤pH值不仅影响土壤对Cr(Ⅵ)的表观吸附量,并且对Cr(Ⅵ)表观吸附动力学特征产生了较大影响.     

毒死蜱有毒代谢物3,5,6-TCP在土壤中的吸附-解吸研究

应用OECD106批平衡方法,研究了毒死蜱的有毒代谢物3,5,6-TCP在6种典型土壤中的吸附-解吸行为。结果表明：Elovich方程、双常数方程和抛物线扩散方程能较好地拟合3,5,6-TCP在第四纪红土、黑土、黄壤和褐土中的吸附动力学过程,而对紫色土和潮沙土的拟合度较低（拟合相关系数小于0.85）;应用Freundlich方程和线性方程拟合第四纪红土、黑土、黄壤和褐土的经验常数nfads均小于1（非线性吸附）,而紫色土和潮沙土的nfads值则接近于1（线性吸附）;3,5,6-TCP在6种土壤中解吸的滞后系数H值均大于1,即解吸速率大于吸附速率。6种土壤对3,5,6-TCP的吸附常数Kfads从1.37-6.74μg1-n·fmLn·fg^-1,吸附系数Kd值从0.50-1.30mL·g^-1,其中第四纪红土和黑土对其吸持力较强（Kd〉1）,因而更应注意环境安全;其他4种土壤的Kd值则均小于1,淋溶风险较大。     

磺胺嘧啶在黑土及其不同粒径组分中的吸附行为研究

采用批平衡吸附试验法,研究了磺胺嘧啶在黑土及其不同粒径中的吸附行为。结果表明,磺胺嘧啶的吸附不同程度地偏离线性模型,但均可用Freundlich模型和Langmuir模型进行良好地线性拟合。黑土（〈0.2mm）及其不同粒径（粘粒：〈0.002mm、粉粒：0.002~0.02mm、砂粒：0.02~0.2mm）的Freundlich容量因子Kf值分别为29.6、53.1、32.9L.kg-1和21.6L.kg-1,说明磺胺嘧啶在黑土及其不同粒径中的吸附行为存在差异。将吸附参数Kf进行碳标化处理后,Koc值除粉粒外,其他基本一致。随着溶液pH的持续增加（1.0~10.0）,黑土及其不同粒径中的磺胺嘧啶的吸附参数lgKf呈现先急剧降低然后稍微回升的趋势,由此推测,阳离子交换作用可能是磺胺嘧啶土壤吸附的重要机制。过氧化氢处理去除土壤有机质后,黑土的Kd值从1.92L.kg-1降为1.22L.kg-1,磺胺嘧啶的吸附量由16.5mg.kg-1降低到11.2mg.kg-1,说明有机质含量也是影响磺胺嘧啶吸附行为的重要因素。     

Natural soil colloids To retard simazine and 2,4-D leaching in soil

Natural or synthetic sorbents for pesticides can be used to reduce contamination of soils and natural waters. The sorption of simazine and 2,4-D on montmorillonite minerals has been studied and their potential use to retard pesticide leaching in soil evaluated. Simazine and 2,4-D did not sorb on high-layer charge montmorillonite, whereas sorption on the lower layer charge montmorillonite SWy varied depending on the saturating cation. Simazine sorption increased in the order Ca(2+)SWy < K(+)SWy < Fe(3+)SWy. Simazine molecules sorb on hydrophobic microsites of the montmorillonite. Once protonated, further sorption through cation exchange takes place in the interlamellar space of the montmorillonite, as corroborated by X-ray diffraction and FT-IR studies. 2,4-D does not sorb on K(+)SWy or Ca(2+)SWy, but does sorb on Fe(3+)SWy, because the acidic character of this sorbent allows the molecular form of 2, 4-D to sorb by hydrogen bonding and/or by hydrophobic interactions. Leaching experiments in hand-packed soil columns indicate that simazine and 2,4-D application as a complex with FeSWy renders later breakthrough and lower maximum concentration peaks, and the total herbicide leached is lower than when applied as the pure analytical grade compound. These results suggest the possible use of natural soil colloids as sorbents for herbicides such as simazine and 2,4-D to retard pesticide leaching in soil, thus reducing their ground water contamination potential.     

Degradation of [carboxyl-14C] 2,4-D and [ring-U-14C] 2,4-D in 114 agricultural soils as affected by soil organic carbon content

This study compared the degradation of [carboxyl-¹⁴C] 2,4-dichlorophenoxyacetic acid (2,4-D) (C2,4-D) and [ring-U-¹⁴C] 2,4-D (R2,4-D) in 114 agricultural soils (0–15 cm) as affected by 2,4-D sorption and soil properties (organic carbon content, pH, clay content, carbonate content, cation exchange capacity, total microbial activity). The sample area was confined to Alberta, Canada, located 49–60° north longitude and 110–120° west latitude and soils were grouped by soil organic carbon content (SOC) (0–0.99%, 1–1.99%, 2–2.99%, 3–3.99% and >4% SOC). Degradation rates of C2,4-D and R2,4-D followed first-order kinetics in all soils. Although total microbial activity increased with increasing SOC, degradation rates and total degradation of C2,4-D and R2,4-D decreased with increasing SOC because of increased sorption of 2,4-D by soil and reduced bioavailability of 2,4-D and its metabolites. Rates of R2,4-D degradation were more limited by sorption than rates of C2,4-D degradation, possibly because of greater sorption and formation of bound residues of 2,4-D metabolites relative to the 2,4-D parent molecule. Based on the sorption and degradation parameters quantified, there were two distinct groups of soils, those with less than 1% SOC and those with greater than 1% SOC. Specifically, soils with less than 1% SOC had, on average, 2.4 times smaller soil organic carbon sorption coefficients and 1.4 times smaller 2,4-D half-lives than soils with more than 1% SOC. In regional scale model simulations of pesticide leaching to groundwater, covering many soils, input parameters for each pesticide include a single soil organic carbon sorption coefficient and single half-life value. Our results imply, however, that the approach to these regional scale assessments could be improved by adjusting the values of these two input parameters according to SOC. Specifically, this study indicates that for 2,4-D and Alberta soils containing less than 1% SOC, the 2,4-D pesticide parameters obtained from generic databases should be divided by 2.5 (soil organic carbon sorption coefficient) and 1.5 (half-life value).     

海泡石对典型水稻土镉吸附能力的影响

通过吸附解吸实验研究了添加海泡石后典型水稻土对Cd的吸附解吸特性及其对吸附溶液pH值变化的响应。结果表明,Freundlich方程可以较好地拟合红黄泥、黄泥田和红沙泥3种典型水稻土对Cd的等温吸附过程（R2〉0.962）。在溶液初始Cd浓度相同的情况下,添加海泡石可使3种水稻土对Cd的吸附量增加20%以上,增强土壤对Cd的吸附强度,有效降低吸附Cd的解吸率,其效果随海泡石添加量的增大而增强。3种水稻土吸附Cd的解吸率均高于70%,而且都随吸附量的增加而上升。溶液的pH值是影响土壤吸附Cd的一个重要因素,在低pH值的条件下（pH〈4）,随着溶液pH值的降低,土壤对Cd的吸附量迅速降低,当溶液pH值高于5时,pH值的变化对吸附量的影响较小。在溶液初始pH值2-8范围内,添加海泡石均能有效提高3种水稻土对Cd的吸附能力。     

Capacity of selected Illinois soils to remove lead from aqueous solution

Abstract

Lead is being added to the environment in automotive exhausts and as an industrial pollutant. To understand its fate in the environment, it is necessary that factors affecting the capacity of soils to sorb Fb be determined.

The capacity of soils to sorb Fb from aqueous solutions vas measured for selected Illinois soils via column leaching experiments and adsorption isotherms. A regression equation was determined that predicted the capacity of a soil to sorb Fb based on its C.E.C., pH and soluble F level. Results of the regression analysis indicated that soil properties associated with increasing C.E.C., i.e. higher organic matter content, higher surface area, and higher clay content have a greater effect on Fb sorption than soil pH, and that soil pH has a greater effect than soluble P.     

Influence of molecular structure on sorption of phenoxyalkanoic herbicides on soil and its particle size fractions

The sorption and desorption behaviors of four phenoxyalkanoic acid herbicides and their metabolites on four agricultural soils and soil particle size fractions were examined. Generally, there was a trend of increasing adsorption and decreasing desorption in the order mecoprop < MCPA < dichlorprop < 2,4-D. The significant increase in adsorption of the phenolic metabolites can be explained by their lower polarity and enhanced partition in the organic soil matrix. Estimation of sorption distribution coefficients from particle size fraction adsorption data was possible for a sandy soil and a silty Cambisol soil only. It is suggested that increasing steric demand, for example, molecular volume, and slight changes in the polarity of the compounds affect their adsorption properties. Comparison of adsorption and desorption data of structurally similar compounds obtained from a variety of soils allows investigation of structure-induced differences in sorption strength.     

Factors influencing degradation of pesticides in soil

Degradation and sorption of six acidic pesticides (2,4-D, dicamba, fluroxypyr, fluazifop-P, metsulfuron-methyl, and flupyrsulfuron-methyl) and four basic pesticides (metribuzin, terbutryn, pirimicarb, and fenpropimorph) were determined in nine temperate soils. Results were submitted to statistical analyses against a wide range of soil and pesticide properties to (i) identify any commonalities in factors influencing rate of degradation and (ii) determine whether there was any link between sorption and degradation processes for the compounds and soils studied. There were some marked differences between the soils in their ability to degrade the different pesticides. The parameters selected to explain variations in degradation rates depended on the soil-pesticide combination. The lack of consistent behavior renders a global approach to prediction of degradation unrealistic. The soil organic carbon content generally had a positive influence on degradation. The relationship between pH and degradation rates depended on the dominant mode of degradation for each pesticide. There were positive relationships between sorption and rate of degradation for metsulfuron-methyl, pirimicarb, and all acidic pesticides considered together (all P < 0.001) and for dicamba and all bases considered together (P < 0.05). No relationship between these processes was observed for the remaining seven individual pesticides.