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71.
NEERA SINGH 《Journal of environmental science and health. Part. B》2013,48(1):17-29
The study aims to prepare the organoclay complexes of metolachlor and metribuzin so as to reduce their downward mobility in soil profile. The organoclays were preadsorbed with phenyltrimethylammonium (PTMA) (50% of cation exchange capacity [CEC]) and hexadecyltrimethylammonium (HDTMA) (100% of CEC). Four metolachlor formulations, two for each organoclay, were prepared having 1% and 2% load of herbicide and were called PTMA-Metol-1%, PTMA-Metol-2%, HDTMA-Metol-1% and HDTMA-Metol-2%. Two metribuzin formulations were prepared and were called PTMA-Metri-1% and HDTMA-Metri-1%. Soil column leaching experiment showed that compared to their commercially available formulations, organoclay complexes were effective in reducing the downward mobility of both herbicides. Organoclay complexes of metolachlor and metribuzin prepared using PTMA-Montmorillonite performed better than the HDTMA-Montmorillonite complexes. 相似文献
72.
施用不同磷肥对植烟土壤中磷的淋失和有效磷的影响 总被引:1,自引:0,他引:1
采用土柱淋溶模拟试验和室内培养试验,研究不同磷肥施入土壤后磷的淋失和有效磷的变化.结果表明,在施磷量为35 mg/kg条件下,整个淋洗期间,钙镁磷肥、磷酸二氢钙、磷酸一氧铵、磷酸二氢铵、磷酸二氢钾5种肥料磷的淋失率很低;各处理从上而下各层土壤的Olsen-P质量比略有增加.施磷量为60 mg/kg、110 mg/kg、170mg/kg、230 mg/kg时.潮砂田肥料磷的淋失率分别为0.26%、0.74%、2.12%和3.17%;灰泥田肥料磷的淋失率分别为0.79%、1.31%、1.60%和1.94%.钙镁磷肥施人各种土壤后,随着培养时间的延长,土壤有效磷质量比逐渐增加,80 d后达到峰值并趋于稳定;磷酸二氢钾、磷酸二氧铵、磷酸一氢铵和磷酸二氢钙施人上壤后,土壤有效磷质量比逐渐降低,至培育60 d后.变化趋于平缓.不同土壤类型对磷的吸附固定率从大到小为潮砂田、灰泥田. 相似文献
73.
Emo Chiellini Andrea Corti Salvatore D’Antone Norman C. Billingham 《Journal of Polymers and the Environment》2007,15(3):169-178
Most of the standardized biodegradation tests used to assess the ultimate biodegradation of environmentally degradable polymers
are based solely on the determination of net evolved carbon dioxide. However, under aerobic conditions, it has to be considered
that heterotrophic microbial consortia metabolize carbon substrates both to carbon dioxide and in the production of new cell
biomass. It is generally accepted that in the relatively short term, 50% of the carbon content of most organic substrates
is converted to CO2, with the remaining carbon being assimilated as biomass or incorporated into humus. The latter is particularly important
when the metabolism of the organic matter occurs in a soil environment. A straightforward relationship between the free-energy
content of a carbon substrate (expressed as the standard free-energy of combustion) and its propensity for conversion to new
microbial biomass rather than mineralization to CO2 has been established. This can potentially lead to underestimation of biodegradation levels of test compounds, especially
when they consist of carbon in a fairly low formal oxidation state and relatively high free-energy content. In the present
work, the metabolism of different kind of carbon substrates, especially in soil, is reviewed and compared with our own experimental
results from respirometric tests. The results show that conversion of highly oxidized materials, such as the commonly used
reference materials, cellulose or starch, to CO2 may be significantly overestimated. The addition of glucosidic material to soil leads to greatly increased respiration and
is accompanied by a very low conversion to biomass or humic substances. In contrast, relatively less oxidized substrates metabolize
more slowly to give both CO2 and biomass to an extent which may be significantly underestimated if glucosidic materials are used as the reference. The
need for an overall carbon balance taking into account both the carbon immobilized as biomass and that volatized as CO2 must be considered in standard respirometric procedures for assessing the biodegradability of slowly degrading macromolecules. 相似文献
74.
通过室内土柱出流实验,分析了重金属离子铜在饱和砂质壤土中的运移行为,发现高浓度的入流液有利于铜离子的运移。同时借助于软件包CXTFIT,用确定性平衡模型和非平衡两区模型对铜离子的出流动态进行了拟合,并预测了土柱不同深度处铜离子浓度随时间的变化过程。结果表明,室内饱和均质条件下,应用确定性平衡模型拟合参数模拟精度要高于非平衡两区模型,可以不用考虑不动水体对铜离子运移的影响。 相似文献
75.
为探究不同淋洗方式下螯合型表面活性剂LED3A(N-十二酰基乙二胺三乙酸钠盐)对重金属污染土壤的淋洗效果,采用室内土柱淋洗法研究了LED3A在不同流速条件下对Pb、Zn单一污染砂土的淋洗效果,并通过优化的BCR法分析了淋洗前、后土柱中不同深度处Pb、Zn的形态变化特征.结果表明:LED3A对Pb、Zn单一污染砂土的淋洗规律基本类似,淋出液中ρ(Pb)、ρ(Zn)随淋洗液累积孔隙体积数目的增加呈现急剧增大、达到峰值后逐渐降低的趋势;Pb、Zn的淋洗曲线中均存在不同程度的拖尾现象,且对称性较差;淋出液中ρ(Pb)、ρ(Zn)峰值和Pb、Zn最大累积去除率均随流速的增大而减小.随着淋洗深度和流速的增加,各形态Pb、Zn的去除率均呈现减小的趋势,LED3A对酸可提取态Pb、Zn的去除效果最为显著,去除率均大于50%;对氧化物结合态、有机结合态和残渣态Pb、Zn的去除率大小顺序与淋洗深度和流速有关;对比淋洗前、后土柱中重金属的形态分布可知,最易释放和被生物利用的酸可提取态的占比明显减少,不易或不能被生物利用的氧化物结合态、有机结合态和残渣态的占比明显增加.研究显示,LED3A低流速淋洗不仅能够去除一定量的土壤重金属,同时可有效降低残留重金属对环境的潜在风险. 相似文献
76.
Renal abnormalities are some of the commonest and most easily detectable anomalies on ultrasound. Many are an isolated finding but the prognosis may be altered considerably by the detection of other anomalies which could indicate a genetic disorder or syndrome. It is often easier to detect presupposed anomalies and the purpose of this article is to introduce and discuss those syndromes that may present with a renal abnormality on ultrasound. Common renal findings are presented with the range of additional anomalies that should be sought and suggested diagnostic tests. It should be remembered that although for many genetic conditions specific mutation analysis is now available, this usually requires pre‒pregnancy investigations. Furthermore, in some cases the definitive diagnosis may not be suspected until post mortem. By this time it may be too late to establish a cell line to confirm the suspicion using laboratory methods. It is therefore important to take tissue samples antenatally where possible, or at delivery, as postnatal samples may have a high culture failure rate. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
77.
Impact of mining activities on soils in a semi-arid environment: Sierra Almagrera district, SE Spain
Andres Navarro Diego Collado Montserrat Carbonell Juan A. Sanchez 《Environmental geochemistry and health》2004,26(3-4):383-393
Field and laboratory-column studies were undertaken in order to investigate soil contamination derived from past mining activity in the Sierra Almagrera (SA) district in southeast Spain. The tailings, soil and sediment samples that were collected showed high concentrations of Ag, As, Ba, Cu, Pb, Sb and Zn when analyzed. The mean concentrations of these elements in the tailings were 29.8, 285.4, 54000, 57.7, 2687.5, 179.0 and 2269.0 ppm, respectively. In the soil samples these decreased to 14.3, 96.9, 24700, 37.5, 1859.1, 168.5 and 815.7 ppm, respectively. Geochemical analyses demonstrated high levels of As, Pb and Zn which were above the intervention values set forth in the Andalusian Regulations for Contaminated Soils for As (>50 ppm), Pb (>500 ppm) and Zn (>2000 ppm). Column experiments and mineralogical studies suggest that the dissolution of sulfates and other secondary phases, accumulated in soils and waste-sites during the dry season, acts to control the mobility of metals. The elution curves obtained from column experiments showed a mobilization of Ba, Cu, Pb and Zn, while a low mobility was seen for Ag, As and Sb. 相似文献
78.
Douglas A. Wolfe K. John Scott John R. Clayton Jr. John Lunz James R. Payne Timothy A. Thompson 《Chemistry and Ecology》1995,10(1):137-156
Standardized tests were applied to aromatic and polar fractions of sediment extracts to determine whether polar constituents or oxidative degradation products contributed significantly to the toxicity of sediments oiled by the Exxon Valdez spill. Intertidal sediment and pore-water samples were collected in September 1990 from two heavily oiled sites and an unoiled site in Prince William Sound (PWS). Methylene chloride extracts from these samples were fractionated by liquid chromatography into aliphatic, aromatic and polar fractions, and the aromatic and polar fractions were tested for toxicity using the MicrotoxR test, bivalve larval mortality and development (Mytilus); several measures of genotoxicity in Mytilus, including SOS ChromotestR, anaphase aberrations and sister chromatid exchange; and survival, anaphase aberrations and teratogenicity in coho salmon (Onchorhynchus kisutch). MicrotoxR and SOS ChromotestR protocols were applied in a screening mode to all samples, whereas other tests were applied only to selected fractions from two sites. Samples from Bay of Isles (oiled) were consistently more toxic (usually only 2 to 5-fold) than the Mooselips Bay (unoiled) samples, which gave very low responses in all tests. for both sites, however, responses to polar and aromatic fractions were about the same in most tests, suggesting that while the overall toxicity of the oil was low in these samples, at least part of that toxicity was derived from polar constituents. Compared to the parent hydrocarbons, polar oxidation products partition preferentially into pore-water and are more rapidly diluted and dispersed in the water column. These results suggest that polar oxidation products of petroleum hydrocarbons pose little risk to marine organisms, except possibly for infauna continuously exposed to pore-water in heavily oiled sediments. Independent surveys showed that sediment toxicity in PWS declined during 1989-1991 to near background levels, in accord with previous understanding of oil weathering and toxicity. 相似文献
79.
水溶性有机物在土壤剖面中的分馏及对Cu迁移的作用 总被引:4,自引:0,他引:4
通过室内土柱试验研究了DOM在土壤剖面中的“分馏”作用,DOM在纵向运移过程中的穿透行为及对污染的红壤和潮土中重金属Cu溶出效果的影响.结果表明,绿肥和猪粪DOM经过土柱后极性都有所降低,在潮土上的降低幅度较大,分别为11.4%和10.72%;DOM能够明显地增加污染土壤中Cu的溶出,且这种作用效果与DOM及土壤的性质有关,绿肥DOM的作用效果比猪粪DOM的强,整个淋洗过程中潮土上Cu的平均溶出量是红壤上的4.37倍(绿肥DOM)和3.03倍(猪粪DOM);由于微生物对DOM的分解作用,降低了DOM对土壤中Cu的溶出效果. 相似文献
80.
南京及邻近地区新近沉积土的动剪切模量和阻尼比的试验研究 总被引:1,自引:0,他引:1
通过对南京及其邻近地区漫滩相成因的粘土、粉质粘土、淤泥质粉质粘土、粉质粘土与粉砂互层土、粉土、粉细砂等 6类新近沉积土的自振柱试验 ,详细探讨了围压大小、剪应变水平、土的颗粒组成和结构性对这 6类新近沉积土的剪切模量G及阻尼比λ的影响。通过与Seed和Idriss建议的砂土G/Gmax~γ和λ~γ曲线变化范围的对比 ,结果表明 ,不能将粉质粘土与粉砂互层土简单地当作砂土或粉质粘土对待。通过试验和理论分析 ,给出了南京及其邻近地区 6类新近沉积土动剪切模量和阻尼比随剪应变变化的平均曲线的拟合曲线、包络线及其参数的推荐值 ,对实际工程具有一定的借鉴作用 相似文献