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121.
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
122.
成都平原蔬菜生产中灌溉水对农药渗漏的影响研究 总被引:9,自引:0,他引:9
针对成都平原蔬菜生产中大量施用农药、大量灌水的特点,首次在国内应用欧洲官方成熟的农药评估模型——PEARL模型,研究评估了成都平原当前蔬菜生产中的灌溉方式对两种不同特性农药的渗漏的影响。杀毒矾(土壤吸附力(KOM)为0 L/kg,半衰期(DT50)为80 d)在没有灌溉条件下,其渗出土体时的最大质量浓度是190μg.L-1,而有灌溉条件下其渗出质量浓度则可达523μg.L-1,是没有灌溉条件下的2.75倍。三唑磷(KOM为200 L.kg-1,DT50为60 d)在没有灌溉条件下,其渗出土体时的最大质量浓度是0.025μg.L-1,而有灌溉条件下其渗出质量浓度为0.13μg.L-1,比没有灌溉时提高了4.2倍。不管有没有灌溉三唑磷在该地区对地下水的污染风险都很小,而杀毒矾的风险则很高。因此,农药的化学特性是影响农药渗漏的最重要的因子。在蔬菜生产中应尽量选用被土壤吸附力强、半衰期短的农药,例如:三唑磷;农药在土壤中的移动载体是土壤水,不合理的灌溉会大大地加大农药淋溶,应当多使用微喷、滴灌等节水灌溉措施,减少使用漫灌等耗水多的原始灌溉方式。 相似文献
123.
David T. Welsh 《Chemistry and Ecology》2003,19(5):321-342
Benthic macrofaunal populations through their feeding, bioturbation, burrow construction and sediment irrigation activities have profound influences on organic matter inputs to marine sediments (biodeposition) and on the vertical distribution of deposited organic matter within the sediment. These effects in turn influence the rates and pathways of organic matter mineralisation, and element cycles. Similarly, bioturbation, burrow construction and burrow irrigation are major determinants of sediment-water column fluxes of oxygen and nutrients.
In this review, I discuss the influences of the different benthic macrofaunal feeding (functional) groups on mineralisation processes and sediment-water column fluxes of particulate and dissolved nutrients. How these effects influence diagenic processes, the balance between aerobic and anaerobic processes, and the redox status of the surficial sediments. Finally, I discuss some of the limitations of the predominantly laboratory techniques which have been used to study “macrofaunal effects” and how this hinders the inclusion of the effects in quantitative sediment biogeochemical models. 相似文献
In this review, I discuss the influences of the different benthic macrofaunal feeding (functional) groups on mineralisation processes and sediment-water column fluxes of particulate and dissolved nutrients. How these effects influence diagenic processes, the balance between aerobic and anaerobic processes, and the redox status of the surficial sediments. Finally, I discuss some of the limitations of the predominantly laboratory techniques which have been used to study “macrofaunal effects” and how this hinders the inclusion of the effects in quantitative sediment biogeochemical models. 相似文献
124.
X.J. Xie W. Ran Q.R. Shen C.Y. Yang J.J. Yang Z.H. Cao 《Environmental geochemistry and health》2004,26(2):237-243
Field experiments were done in two sites, Yixing and Changshu, Jiangsu province, China, to study P movement and leaching in flooded paddy soils. P movement in soil was investigated by using the KH2
32PO4 tracker method, and the amount of P leached from the soil layer in different depths was estimated by measuring P concentrations in the soil solution and saturated hydraulic conductivities in field. Determination was done about one month after P application. There was 46% and 42% of total 32P retained in the 0–5cm layer of soil in the Yixing site and in the Changshu site respectively. The 32P retained in the 25–30 cm layer was only about 1–2% of the total 32P added. Furthermore, 8.01% of 32P in the soil of Yixing site and 16.8% of 32P in the soil of Changshu site was lost from the layer 0–30cm soil. The seasonal amounts of P leached from the top soil layer and from bottom layer are about 4.5–5.8% and 1.6–2.1% of the total P application, respectively. Changes of total P concentrations in soil solutions during rice growth showed that the fertilizer P applied before flooding of the paddy fields suffered a flash leaching loss and a slow leaching loss. We concluded that the fertilizer P could quickly move in the flooded paddy rice field and parts of it can enter into surface water and ground water. Unless the P application is well managed the risk of P loss and consequently environmental pollution exist. 相似文献
125.
本文主要介绍在含酸及其相应盐的废液中分离酸和盐的一种方法。将含酸及其相应盐的废液,通过装有强碱性阴离子交换树脂柱,其中的酸受到阻滞,而相应的盐能顺利通过,然后用水洗脱,则流出的是含酸的溶液,使酸和相应的盐得到了分离。经FeSO4-H2SO4和ZnSO4-H2SO4两组废液的试验,均能使酸和金属得到回收。分离后的废水,可达标排放,废液得到了处理。酸阻滞法简单易行,易于投产使用,不受规模大小的限制。 相似文献
126.
This study delineated the mathematical forms for the reactions involved in the mass balance of As in cropland soils. Even
mathematically simplified, many model parameters are required to define the reactive processes involved. Example simulations
were conducted based on the range of parameter values and initial conditions derived from published literature. The outcomes
showed that the As inputs due to fertilizers and irrigation water caused total As content of the root zone to gradually increase
over time. The plant uptake and leaching were equally important as pathways for removal of the added As. In turn, the dissolution
kinetics of the mineral phase and the distribution coefficient of the adsorbed phase affected the availability of the As for
plant uptake and leaching. Parameters based on laboratory-derived data on the dissolution of As mineral phase, mineralization
and oxidation of As(III), and the As plant uptake however appeared to overestimate the As transformations in soils. While
the development of mathematical model was a straightforward process, its application to realistic situations was hindered
by difficulties of defining model parameter values with confidence. Current knowledge on the processes and reactions of As
transformation in the soil–plant system is inadequate to calibrate or validate the model. Studies are needed to understand
the kinetics of soil As mineral dissolution and precipitation and the dynamics of root growth and As uptake by plant in soils. 相似文献
127.
应用HYDRUS-1D模型模拟农田土壤水渗漏及硝态氮淋失特征 总被引:1,自引:0,他引:1
在定位试验基础上,应用HYDRUS-1D模型对黄淮海平原典型土壤(黄潮土)中土壤水渗漏及硝态氮淋失动态进行了模拟分析。结果表明:在传统水氮管理模式下,黄潮土2m土体深处的土壤水渗漏和硝态氮淋失非常严重,2个轮作期内,土壤水渗漏总量占地表总入水量的23.7%,硝态氮淋失总量占总输入N量的15.9%,冬小麦生长季的硝态氮淋失量大于夏玉米生长季;改良灌溉和改良施肥模式下产生的硝态氮淋失量比传统灌溉和传统施肥模式减少74.7%,节约灌溉水211.5mm、节省施N423.5kg·hm-2。 相似文献
128.
主要原材料为高炉矿渣的碱矿渣胶凝材料(HAS)、掺3%沸石的HAS、掺5%沸石的HAS、水泥等4种固化材料被用来固化人工合成含铅、镉、铬等重金属的污泥。污泥固化体中污泥与固化材的掺和比例为4:1。实验结果表明,HAS固化剂对重金属污泥的固化效果要好于水泥,其污泥固化体的无侧限抗压强度高于水泥固化体,同时其固化体的重金属浸出量明显低于水泥。沸石的掺入使HAS固化体的重金属浸出量减小,且随着沸石掺加量的增大,HAS固化体的重金属浸出量相应的减少。 相似文献
129.
本文研究了利用毛细管柱分离、测定水样中的苯系物。该方法用二硫化碳萃取水样中的苯系物,细口径毛细管柱分离,FID测定。在分流比为100∶1的条件下,方法最低检出浓度在0025~0047mg/L之间,低于填充柱法。该方法适用于地表水、地下水和废水中微量苯系物的测定。 相似文献
130.