Electrokinetic movement of multiple chlorobenzenes in contaminated soils in the presence of β-cyclodextrin

This study investigated the electrokinetic (EK) behavior of multiple chlorobenzenes, including 1,2,3,4-tetrachlorobenzene (TeCB), 1,2,4,5-tetrachlorobenzene (i-TeCB), and 1,2,3-trichlorobenzene (TCB) in contaminated clayed soils. The effect of β-cyclodextrin (β-CD) on the EK removal of the chlorobenzenes was studied. The largest removal was obtained when Na2CO3/NaHCO3 buffer was used as anodic purging solution without β-CD. The removal efficiencies were related to the aqueous solubilities of chlorobenzenes. With the same cumulative electroosmotic flow, greater solubility led to higher removal efficiency. The addition of β-CD inhibited the EK removal efficiency of all chlorobenzenes. The inhibition increased with the increase of β-CD concentration. With the same β-CD concentration, the inhibition increased with the rise of electric potential. It was found that the inclusion compounds between β-CD and chlorobenzenzes were less soluble than chlorobenzenes. The formation of the less soluble inclusion compounds reduced the aqueous solubility of chlorobenzenes and led to the partial immobilization of the chlorobenzenes that desorbed from soil. It was feasible to use the EK technology to remove chlorobenzenes in contaminated soils using water as the anodic flushing solution. The addition of β-CD was not recommended for the EK removal of chlorobenzenes.     

Effect of sorbed and desorbed Zn(Ⅱ) on the growth of a green alga (Chlorella pyrenoidosa)

Toxic effect of Zn(Ⅱ) on a green alga (Chlorella pyrenoidasa) in the presence of sepiolite and kaolinite was investigated.The Zn-free clays were found to have a negative impact on the growth of C.pyrenoidosa in comparison with control samples (without adding any clay or Zn(Ⅱ)).When Zn(Ⅱ) was added,the algae in the presence of clays could be better survived than the control samples,which was actually caused by a decrease in Zn(Ⅱ) concentration in the solution owing to the adsorption of Zn(Ⅱ) on the clays.When the solution system was diluted,the growth of algae could be further inhibited as compared to that in a system which had the same initial Zn(Ⅱ) concentration as in the diluted system.This in fact resulted from desorption of Zn(Ⅱ) from the zinc-contaminated clays,although the effect varied according to the different desorption capabilities of sepiolite and kaolinite.Therefore the adsorption and desorption processes of Zn(Ⅱ) played an important part in its toxicity,and adsorption and desorption of pollutants on soils/sediments should be well considered in natural eco-environmental systems before their risk of toxicity to aquatic organisms was assessed objectively.     

Chemical reclamation of crude-oil-inundated soils from Niger Delta, Nigeria

Crude-oil-inundated soils were collected from the Agbada oil field in the Niger Delta region of Nigeria 2 months after the recorded incidence of oil spillage. The soils were taken on the second day of reconnaissance from three replicate quadrats, at surface (0-15 cm) and subsurface (15-30 cm) depths, using the grid sampling technique. The total extractable hydrocarbon content (THC) of the polluted soils ranged from 1.24 × 10² to 3.86 × 10⁴ mg/kg at surface and subsurface depths (no overlap in standard errors at a 95% confidence level). Greenhouse trials for possible reclamation were later carried out using 10-100 g of (NH₄)₂SO₄, KH₂PO₄ and KCl (NPK) fertilizer as nutrient supplements. Nitrogen as NO₃-N and potassium were optimally enhanced at 2% (w/w) and 3% (w/w) of the NPK supplementation, respectively. Phosphorus, which was inherently more enhanced in the soils than the other nutrients, maintained the same level of impact after treatment with 20 g of NPK fertilizer. Total organic carbon (%TOC), total organic matter (%TOM), pH, and percentage moisture content all provided evidence of enhanced mineralization in the fertilizer-treated soils. If reclamation of the crude-oil-inundated soils is construed as the return to normal levels of metabolic activities of the soils, then the application of the inorganic fertilizers at such prescribed levels would duly accelerate the remediation process. However, this would be limited to levels of pollution empirically defined by such THC values obtained in this study.     

SOIL-MOISTURE EFFECTS OF CONVERSION OF SAGEBRUSH COVER TO BUNCHGRASS COVER1

Precipitation, soil moisture, runoff, and vegetation were measured on two, 5- to 10-acre, big sagebrush (Artemisia tridentata) watersheds and two, equally small, beardless bluebunch wheatgrass (Agrophron inerme) watersheds that were converted from big sagebrush in 1967. The watersheds are located near Wolcott, Colorado, at an elevation of 7,200 feet, and are mantled with 2 to 3 feet of silty clay soils. Annual precipitation was about 13.5 inches; about 9 inches occurred as rain or snow from April through October and about 4.5 inches accumulated as a snowpack from November through March. Evapotranspiration was about 2 inches greater in 1968 and 1 inch greater in 1969 from the sagebrush watersheds than from the grass watersheds. With a mature stand of grass in 1970 and 1971 the differences in evapotranspiration were within the range of differences measured during the 3-year calibration period when all four watersheds were sagebrush. Water use was similar in the top 1 foot of soil but slightly more water was used by the grass in the 1- to 2-foot zone and more water being used by the sagebrush below 2 feet. Soil-water potential data indicated that only the big sagebrush used a small amount of water from the fractured shale at depths below 40 inches. Sagebrush used more water in August and September than the grass.     

Determination of Background Concentrations of Inorganics in Soils and Sediments at Hazardous Waste Sites

Hazardous waste sites may pose a threat to human health and the environment when toxic substances are released. However, the contaminants present at a waste site may have originated on-site (i.e., resulting from releases attributable to site activities) or off-site (i.e., resulting from sources not on-site). Off-site substances may result either from natural sources (e.g., erosion of naturally occurring mineral deposits) or anthropogenic sources (e.g., widespread contamination from automobile exhaust in urban areas). To determine the appropriate action to take at a hazardous waste site, the U.S. Environmental Protection Agency (EPA) must distinguish between substances directly attributable to the hazardous waste site (i.e., site contaminants) and those attributable to natural background concentrations. The most important factor to consider when determining background concentrations is to ensure that the physical, chemical, and biological aspects of the media to be sampled at both the contaminated site and the background site are as similar as possible. Inorganics, in particular metals, are addressed. Radionuclides are not specifically addressed; however, metals with radioactive isotopes that may be encountered at hazardous waste sites are included. There are references and data included in this paper that provide average concentrations and reference values for selected soils and sediments in the United States. Suggested sampling and monitoring design approaches that could be used by scientists and engineers faced with how to determine background concentrations are identified. The issues discussed include the selection of background sampling locations, considerations in the selection of sampling procedures, and statistical analyses for determining whether contaminant levels are significantly different on a potential waste site compared with a background site.     

贵阳中心区土壤氟的地球化学特征及其环境质量评价

为摸清土壤氟异常对生态环境的影响,利用贵州省多目标区域地球化学调查（1:250 000）项目成果,对贵阳中心区土壤氟的地球化学特征进行了深入研究,并采用全氟指数法对土壤环境质量及其生态环境效应进行初步评价.结果表明:①贵阳中心区土壤氟含量较高,表层、深层土壤氟含量平均值分别为1 143、1 438 mg/kg,且空间分布变化较大;氟含量随土层深度的增加而升高. ②不同类型土壤中氟含量变化较大,其中紫色土中含量（1 306 mg/kg）最高,水稻土次之,石灰土、粗骨土、黄壤等差别较小,其含量范围在1 099~1 167 mg/kg之间. ③土壤氟含量与其母岩呈显著正相关性,且土壤中氟含量较母岩更高,表明风化成土过程中存在一定富集,土壤氟与成土母岩之间具有一定继承性. ④土壤氟环境质量评价结果表明,研究区土壤存在局部氟污染（异常）,污染区、警戒区、安全区和清洁区所占比例分别为13.6%、62.2%、19.2%和5.0%. ⑤生态环境效应初步调查结果显示,局部土壤受氟污染区的油菜和稻谷样品中氟含量范围分别为1.86~2.68和10.40~13.50 mg/kg,同时地下水也受到一定程度的氟污染.因此,贵阳中心区土壤氟含量较高,局部土壤已受到氟污染,可能会对农产品质量、饮水安全及人体健康产生一定影响,建议政府部门及科研工作者予以高度重视.      

牛骨炭与伊/蒙黏土组配改良剂对土壤中Cd的钝化效果

农田土壤Cd污染是我国最为突出的环境问题之一,开展新型钝化修复Cd污染土壤材料的研究和技术开发对保障农产品安全及保护人体健康具有重要意义.以北京某蔬菜生产基地设施大棚Cd污染土壤为试验对象,温室条件下采用盆栽试验,研究牛骨炭与伊/蒙黏土复合组配的改良剂对Cd污染土壤的钝化效果,探讨不同配比的组配改良剂对土壤Cd有效态含量以及小白菜Cd吸收量的影响.结果表明:在污染土壤中添加1%、2%和5%的组配改良剂,可明显降低土壤有效态Cd含量及小白菜对Cd的吸收,土壤有效态Cd含量降幅最大值达42.3%,小白菜地上部分Cd含量降幅最大值达22.7%,组配改良剂中骨炭成分比例越高,钝化效果越好,尤其以添加5%组配改良剂（添加组配改良剂中牛骨炭含量为50%）对Cd的稳定化效果最佳,且不同组配改良剂处理均不会对小白菜生长产生不良影响,表明牛骨炭与伊/蒙黏土组配的改良剂在修复Cd污染土壤上具有较好的应用潜力.研究显示,牛骨炭与伊/蒙黏土组配的改良剂符合绿色修复技术的发展要求,可作为钝化修复农田重金属污染土壤的环保新材料.      

Effects of urbanization on heavy metal accumulation in surface soils, Beijing

Urbanization processes affect the accumulation of heavy metals in urban soils. Effects of urbanization on heavy metal accumulation in soils were studied using Beijing as an example. It has been suggested that the ecological function of vegetation covers shifting from natural to agricultural settings and then to urban greenbelts could increase the zinc(Zn) concentrations of soils successively. The Zn concentration of urban soils was significantly correlated to the percentage of the impervious land surface at the500 m × 500 m spatial scale. For urban parks, the age or years since the development accounted for 80% of the variances of cadmium(Cd) and Zn in soils. The population density,however, did not affect the heavy metal distributions in urban soils. To conclude, the urban age turned out to be a notable factor in quantifying heavy metal accumulation in urban soils.     

基于油提取的土壤与沉积物中微塑料的分离方法

微塑料作为一种全球性新兴污染物受到学界与社会的广泛关注.由于土壤和沉积物中的微塑料难以分离提取,目前关于微塑料的研究主要集中于水体中,而关于土壤与沉积物中微塑料的丰度、分布与环境行为尚不清楚,迫切需要一种经济、快速、可靠的前处理手段将微塑料从土壤或沉积物中分离出来进而开展检测与监测工作.油提取法不同于传统密度浮选法,其利用塑料的亲油性,使用植物油代替密度液分离土壤与沉积物中的微塑料.通过油提取法在砂土（二长花岗岩风化层残坡积物）、壤土（菜地黄棕壤）、黏土（稻田水稻土）、泥质湖泊沉积物中获得的总加标回收率分别为88.3%±6.29%、88.3%±3.82%、90.0%±2.50%、90.8%±1.44%.其中,对于密度浮选法较难提取的聚氯乙烯（PVC）、聚对苯二甲酸乙二醇酯（PET）,其回收率分别为93.3%±11.6%（壤土）、96.7%±5.77%（壤土）.植物油的加入会对后续微塑料的光谱表征识别产生影响,但可通过无水乙醇冲洗去除,与拉曼光谱仍具有良好的兼容性.利用该方法开展的实地研究获得黄冈市残坡积物（砂土）、武汉市菜地（壤土）、武汉市水稻田（黏土）、武汉市东湖泥质湖泊沉积物中的微塑料丰度分别为1 679、1 612、1 766、7 629个/kg.研究显示,油提取是当下密度浮选技术的可替代方案.      

IMPACTS OF RECREATION ON RIPARIAN SOILS AND VEGETATION1

ABSTRACT: The seemingly magnetic attraction of water resources for recreation has direct implications for proximate land resources which are needed to provide access and support facilities. This paper reviews and synthesizes the literature dealing with the impacts of recreation use on riparian soils and vegetation. Part one of the paper sets forth the major negative impacts of recreation use on soils and vegetation. A seven-step soil impact cycle is identified, beginning with the scuffing away of leaf litter and other organic material and working through the soil erosion and sedimentation process. Four major kinds of impacts of recreation use on vegetation are then outlined, and the‘Vicious circle” relationship between impacts on soil and vegetation is demonstrated through a Soil/Vegetation Impact Diagram. Part two identifies several spatial and temporal patterns of environmental impact caused by recreation use. The node and linkage pattern of recreation use, campground and trail expansion, ground cover response and succession, rates of soil compaction, and resource response to various intensities of recreation use are important aspects. The final part of the paper deals with measuring environmental impacts caused by recreation use. Management implications of the research findings are considered throughout the paper.