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1.
`土壤-地下水耦合数值模拟是定量刻画水流和溶质运移的主要手段。现有大范围场地尺度的研究受到数据采集难度及模拟计算量的限制,多是将土壤和地下水分成两个系统,这种方式不利于模型之间的计算反馈,易出现计算误差,因此将土壤和地下水作为整体系统研究具有重要意义。为精确刻画实际场地土壤-地下水系统中污染物迁移规律,揭示变饱和反应溶质迁移模型的参数敏感性,以某铬污染场地为研究对象,基于现场试验及前人研究所获数据,采用Galerkin有限元法建立三维土壤-地下水模型,定量描述六价铬在土壤-地下水中的迁移规律。在此基础上,通过改变补给条件,研究潜水面在土壤-地下水系统中的波动。并讨论阻滞系数和反应常数对溶质运移的影响。结果表明:在土壤中,污染物最大水平迁移距离为场地东南侧300 m;地下水中污染晕最大分布面积约为1.632 km2;垂向上土壤中的六价铬仅需15.6 h即可下渗至潜水面,第6天贯穿含水层。当潜水面随着补给量变化而波动时,地下水中六价铬会随水流进入土壤,影响土壤中污染分布。对溶质运移参数的讨论显示,当反应常数由0增大至10?6 s-1时,迁移出场区边界时地下水中污染物浓度约减少2000 mg/L,较难迁移至涟水河。基于FEFLOW的数值模型,能够解决各系统之间交互性差的问题,提供较为精确的模拟结果。 相似文献
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水及溶质在有大孔隙的土壤中运移的研究(Ⅱ):数值模拟 总被引：1，自引：0，他引：1
本文根据CT扫描得到的土壤大孔隙分布、离心机法测得的土壤水分特征曲线以及计算得到的土壤大孔隙和基质的饱和水力传导度和弥散度,采用新的数值方法模拟了水及溴离子在原状土中的运移,分析比较了模拟结果,得到了原状土溴离子在各时刻的运移图,定量分析了大孔隙的存在对水及溶质运移的影响和对地下水造成的污染。 相似文献
3.
针对位于干旱-半干旱气候带的我国西北部矿区生态修复过程中重构层状土壤水分运移规律不清等问题,通过设置不同层状结构土壤进行水分运移入渗试验,监测土壤剖面水分变化,采用Hydrus-1D模拟降雨入渗过程,从土壤水分、水势和水通量3个方面揭示层状土壤水分运移特征,并基于优化后的模型进行情景模拟,探究夹层特征对浅层土壤水分运移的影响。研究结果表明,夹层明显改变了土壤水分的分配与运移过程,土壤水势在夹层界面连续分布,而土壤水分在夹层界面发生突变;虽然黄土夹层和风化砂岩夹层都阻滞了土壤水分的下渗,但其阻滞原理不同,前者表现为黏质夹层渗透性能差导致夹层以上土壤水分滞留,后者归因于粗质夹层土壤基质势小造成水分持留在上部黏质土壤中;根据不同夹层属性的情景模拟结果,提出在风积沙40 cm深度处设置20 cm厚的黄土夹层有利于提高夹层以上土壤水分以供植被利用。研究探明了风积沙区充填黄土对土壤水分运动的影响,并为土壤类型以风积沙和黄土为主的我国西北部矿区在生态修复中的土壤重构方式提供了参考依据。 相似文献
4.
土壤中水分和溶质运移一直是土壤-水环境系统中的研究热点,也是目前仍未得到很好解决的问题.将分形理论应用于土壤水分溶质运移机制的研究,探讨其领域中的众多复杂问题,是一种全新的思路和方法.在对土壤结构定量化的分形表征进行简要阐述的基础上,重点介绍了分形理论在水分特征曲线和水力传导度等土壤水分运动基本参数的分形模型、土壤水分运移过程模拟、土壤溶质运移的非费克现象、弥散度的尺度效应以及溶质运移机制研究方面所取得的一系列成果,并就分形理论今后在土壤水分、溶质运移研究中的应用作了展望. 相似文献
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地下多组分反应溶质运移数值模拟:地质资源和环境研究的新方法 总被引：1，自引：0，他引：1
地下多组分反应溶质运移数值模拟(RTM)是解释地球系统中的耦合过程和不同时空尺度对其影响的重要工具。RTM是研究地球科学基础理论、地质资源和环境等复杂地球化学过程的一个新方法,可用于如废物处置安全性评估、地下水污染研究、二氧化碳地质储存、金属矿床的地浸开采等的研究中。笔者首先回顾了反应溶质溶质运移模拟的发展历史,然后总结了反应溶质运移模拟的发展现状,再从耦合过程、空间尺度、裂隙和非均质介质处理角度说明了反应溶质运移模拟所面临的挑战。结合地下水质的演化、生物降解、CO2地质储存等具体实例讨论了反应溶质运移模拟的广泛应用前景,探讨了反应溶质运移模拟的未来发展方向。 相似文献
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地下热水运移中自然对流的研究 总被引：9，自引：0，他引：9
本文研究了自然对流在地下热运移中的作用和规律，并给出了数值模拟方法。计算结果显示，含水层水温愈高，试验时间愈长，则自然对流作用愈显著。通常情况下模拟地下热水运移时，不应忽略自然对流作用。 相似文献
8.
有效地管理地下水系统需要论述和预测该系统中污染质的运移和消亡情况,以便能更好地运用数学模型准确地描述系统的物理现象。影响许多有机污染物运移的最明显现象是在固(土壤)和液(地下水)两相之间的分配现象。污染物的分配趋势大体可以用对辛醇的基本性质的测量值进行估计,即取决于污染物的水分配系数和土壤的有机碳含量。这个粗略估计是定性评价的基础,但对系统的定量描述就不行,特别是所考虑的问题是非线性平衡吸附问题,分配取决于动力条件或是不可逆的,或者滞后相的分布现象等。准确地进行溶质运移模拟常常需要结合动力学参数和非线性吸附方法才能正确地确定质量守恒方程中的溶质运移现象。实验的方法可以用来确定重要的吸附因子,有机溶质和土壤系统的动力学性质及平衡分配关系。因此利用这种方法能够更准确地模拟污染质的迁移情况。 相似文献
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海河流域滹沱河冲洪积扇地下水中农药污染及分布特征 总被引：1，自引：0，他引：1
地下水是海河流域滹沱河冲洪积扇重要的饮用水水源,农业种植过程中施用的农药会导致地下水污染,该地区地下水中农药的污染调查工作相对匮乏。为了研究滹沱河冲洪积扇地下水中农药的污染及分布特征,本文利用气相色谱-质谱联用技术分析了30组地下水样品中75种农药组分,用统计学方法对结果进行分析。结果显示:30个采样点中均有农药检出,检测的75种农药中检出40种,有机氯、有机磷、有机氮三类均有检出。检出率最高的为3-羟基呋喃丹(93.3%)、敌杀磷(90.0%)、地茂散(90.0%),30个样品检出浓度之和最大的为呋喃丹(4860.6ng/L)。研究区内三类农药平均检出浓度有机氯(70.8ng/L)有机磷(392.7ng/L)有机氮(580.9ng/L),这主要与三类农药的使用历程和性质相关:有机氯类农药由于其高毒、难降解等特性在1983年被禁用;21世纪初,相对高效、易降解的有机磷类和有机氮类农药应用广泛。三类农药的空间分布特征为从冲洪积扇顶部到中部,农药含量逐渐减少,这主要受冲洪积扇水文地质特征的影响。研究区内HCHs来源为近期林丹使用或HCHs工业降解,DDTs来源为新DDT源的释放或历史上的使用。研究结果可为我国地下水农药的污染监测和地下水相关标准制定提供数据支撑。 相似文献
12.
Abdelhafid Fekkoul Yassine Zarhloule Mimoun Boughriba Alae-eddine Barkaoui Abdelhakim Jilali Salem Bouri 《Arabian Journal of Geosciences》2013,6(12):4917-4924
Located at the northeastern part of Morocco, the plain of Triffa is characterized by a semi-arid climate where water resources are rather fragile and influenced by a highly irregular rainfall distribution, both in time (annual and inter-annual distribution) and in space. The mean annual rainfall does not exceed 240 mm. In the Triffa plain, the impact of anthropogenic activities on the groundwater resources is reflected both by (a) the decrease in the piezometric level due to the over exploitation and droughts and (b) the deterioration of the chemical quality of water. Currently, this situation is felt mainly by the farmers. The unconfined aquifer is under stress due to the increase of the pollution rate, especially by nitrates that are above the WHO standards, and salinity. Organochlorine pesticides are ubiquitous and persistent organic pollutants used widely in agriculture. Due to their extensive use in agriculture, organic environment contaminants such as hexachlorocyclohexane, DDT, and DDD along organochlorine pesticides are distributed globally by transport through water. Pesticides such as aldrin, lindane, and heptachlor have also been detected and were considered as indicators showing the need to inform and to train farmers on the pesticides and fertilizers use in order to reduce the threat of groundwater contamination. 相似文献
13.
农药降解菌及其基因工程研究进展 总被引：4，自引：0，他引：4
农药的使用对农业的发展有着重要作用,但同时也造成了严重的环境污染。微生物对环境中残留农药的降解起着重要作用,能减少农药对环境安全的影响。研究者已分离得到一批降解性能不同的农药降解菌,并鉴定了其中一些降解酶及降解基因。通过构建基因工程菌可以增强微生物的环境适应性,提高农药的降解效率,农药降解酶制剂及其固定化技术则为解决降解菌实际工程应用中的生态安全问题提供了可行的路径。本文介绍了农药降解菌的筛选、降解特性、降解途径与降解酶的研究,阐述了农药降解基因工程菌的构建策略、研究概况和应用进展。 相似文献
14.
Khadija Semhi Joëlle Duplay Gwenaël Imfeld René Boutin 《Arabian Journal of Geosciences》2018,11(19):590
The main objective of this study is to investigate the distribution of rare earth elements (REEs) in Lolium perenne L. plant species which has been grown on vineyard soils treated with pesticide commonly used in the study area. These plants have been grown on two types of soils: (1) brown calcareous soils developed on loess and (2) brown to calcic brown soils developed on conglomerates. The significant correlation observed between the concentrations of phosphorus and the total amount of REEs, in addition to the enrichment in middle REEs (MREEs), suggests the complexation of REEs with phosphates and organic matter. The soils were enriched in REEs due to pesticide application but the plants were depleted. The ratio of REEs in plant over REEs in soil before application of pesticides is higher than that after application of pesticides. Application of pesticides to crops did not affect the fractionation of REEs neither in leaves nor in roots. No selectivity in uptake of REEs occurred because of pesticides except for Ce and Eu which show a negative anomaly relative to the other REEs. 相似文献
15.
Jehangir Shah Abdur Rahman Mumtaz Khan Khan 《中国地球化学学报》2006,25(B08):187-188
Tobacco is an important cash crop in Pakistan. It is a sensitive plant prone to many bacterial, fungal, and viral diseases. It is also attacked by several species of worms, beetles and moths. Therefore high levels of pesticides are used to grow tobacco. The obvious benefits from the use of the pesticides are so spectacular that some of the problems associated with their use are not recognized. However, many of these pesticides are highly toxic and have impacts on tobacco workers, especially occupational exposures, which are the direct victims of pesticides poisoning. The victims include many children, pregnant women and elders who all participate in tobacco production. Pesticides either cause or exacerbate a number of illnesses in farmers and farm workers when they are exposed to them. So, occupational exposure is probably one of the most important impacts on tobacco farmers, since they and their families are exposed constantly to a large amount of pesticides. This exposure can lead to many serious problems. No study has been done to identify the effects of tobacco pesticides on human health especially on farmers health in Pakistan. The objective of this paper is to establish a correlation of pesticides application on tobacco crop with cancer incidence in the tobacco growing districts of NWFP- Pakistan. 相似文献
16.
苏南典型地区土壤中有机氯农药残留的空间分布及来源分析 总被引：1，自引：0，他引：1
本文研究了江苏张家港市土壤中有机氯农药六六六(HCH)和滴滴涕(DDT)的残留状况,用空间插值和GIS技术分析了其空间分布规律,探讨了潜在来源。结果表明,547个采样点中有21.94%的表层土壤样品中检出HCH,而DDT的检出率为96.16%。HCH在土壤表层的残留均低于《土壤环境质量标准》(GB 15618-1995)的二级标准(500 ng/g),超过一级标准(50ng/g)的也仅占1.46%,DDT则有0.55%的样品超过二级标准。HCH和DDT不同异构体的比值指示土壤中可能有新的来源,但主要还是与历史上的农药施用有关。空间上HCH在南部人为土区的含量要显著高于北部的雏形土区,DDT则相反,这一空间分布格局主要与不同地区的种植历史有关,HCH在人为土区的较高残留可能与历史上水稻种植有关,DDT在北部雏形土区的较高残留则与棉花种植关系较密切。 相似文献
17.
Estuaries receive large quantities of suspended sediments following the first major storm of the water year. The first-flush events transport the majority of suspended sediments in any given year, and because of their relative freshness in the hydrologic system, these sediments may carry a significant amount of the sediment-associated pesticide load transported into estuaries. To characterize sediment-associated pesticides during a first-flush event, water and suspended sediment samples were collected at the head of the San Francisco Bay during the peak in suspended sediment concentration that followed the first major storm of the 1996 hydrologic year. Samples were analyzed for a variety of parameters as well as 19 pesticides and degradation products that span a wide range of hydrophobicity. Tidal mixing at the head of the estuary mixed relatively fresh suspended sediment transported down the rivers with suspended sediments in estuary waters. Segregation of the samples into groups with similar degrees of mixing between river and estuary water revealed that transport of suspended sediments from the Sacramento-San Joaquin drainage basin strongly influenced the concentration and distribution of sediment-associated pesticides entering the San Francisco Bay. The less-mixed suspended sediment contained a different distribution of pesticides than the sediments exposed to greater mixing. Temporal trends were evident in pesticide content after samples were segregated according to mixing history. These results indicate sampling strategies that collect at a low frequency or do not compare samples with similar mixing histories will not elucidate basin processes. Despite the considerable influence of mixing, a large number of pesticides were found associated with the suspended sediments. Few pesticides were found in the concurrent water samples and in concentrations much lower than predicted from equilibrium partitioning between the aqueous and sedimentary phases. The observed sediment-associated pesticide concentrations may reflect disequilibria between sedimentary and aqueous phases resulting from long equilibration times at locations where pesticides were applied, and relatively short transit times over which re-equilibration may occur. 相似文献
18.
Impact of major organophosphate pesticides used in agriculture to surface water and sediment quality (Southern Caspian Sea basin,Haraz River) 总被引：3，自引：3，他引：0
Touraj Nasrabadi Gholamreza Nabi Bidhendi Abdolreza Karbassi Peter Grathwohl Nasser Mehrdadi 《Environmental Earth Sciences》2011,63(4):873-883
Organophosphate pesticides are compounds that are not only toxic to both humans and wildlife but also difficult to degrade
under natural environmental conditions. In Iran, agricultural practices are strongly dependent on the use of pesticides due
to climatic and soil conditions, thus posing a potential risk to groundwater quality standards. Evaluating the concentration
of organophosphate pesticides namely diazinon, fenitrothion, dichlorvos, ethion, profenofos, malathion and azinphos methyl
in water samples in May (low precipitation rate), December (high precipitation rate) as well as the concentration in sediments
along the Haraz River is taken into consideration in this study. Generally the pesticides concentration in water samples are
relatively higher in May in comparison with that in December; this fact may be due to two major reasons: the first reason
is attributed to the prompt raining after the treatment period of most orchards and dry farming lands that will terminate
in more wash out of such pesticides towards the branches and main river channel, while the second reason may be considered
as the less river water dilution rate in May because of lower precipitation rate. Furthermore, the relatively higher concentrations
in downstream stations may be contributed to more intensified agricultural (specially rice paddies), urban and rural land
uses in this region in comparison with upstream areas which contain mainly dry farming, grazing lands and orchards with relatively
lower loads of pesticides. Additionally, as the Henry’s law constant of all pesticides considered in this study are relatively
low, volatilization may not be regarded as an important route of dissipation. Diazinon, azinphos methyl and dichlorvos showed
the highest water concentrations in comparison with other pesticides that may be justified by their extended use within the
basin during last decades. Based on the chemical properties as well as remarkably higher values in sediment samples in comparison
with water ones, it is concluded that the two pesticides, ethion and fenitrothion, persist in the environment due to non-degradable
tendencies. Although the concentration of mentioned pesticides is not so high in the water samples, more precautions must
be considered in their future use. Regarding the sorption coefficient variation alongside the river, the higher values in
upstream and central parts may be attributed to the higher potential of different types of erosion regarding deeper slopes
and also sand, gravel and carbonate mining activities at the banks and also river bed in such regions which is considered
as an anthropogenic disturbance. In case of central parts, in addition to mentioned reasons, the existence of coal outcrops
in the geologic texture of the study area may also be considered as a key role in augmentation of the sorption coefficient.
Finally, the dominant clayey and loamy soils containing more organics may be attributed as the major reason of sorption tendency
in downstream. 相似文献
19.
Meththika Vithanage Anushka Upamali Rajapaksha Hasintha Wijesekara N. Weerarathne Yong Sik Ok 《Environmental Earth Sciences》2014,71(2):837-847
Inorganic arsenic (As) pesticides have been widely used for decades in many countries. However, insufficient data are available on the chemical speciation of inorganic arsenicals in tropical paddy soils. Inorganic As-containing pesticides were used in tropical countries, a few decades ago, however, their fate have not been studied. Hence, the objective of this study was to determine fractionation of inorganic arsenicals and to assess As lability with/without fertilizer application using a static incubation experiment. Eight soils from wet and dry regions of Sri Lanka were amended with 1,000 mg/kg arsenate for this purpose. The FT-IR and XRF results suggested that soils in the wet region were rich in Fe/Al-oxides. Paddy soils in the dry zone showed high As lability. These low-humic gley soils have low Fe/Al oxyhydroxide and alkaline pH. In contrast, the wet zone had soils with higher As retention capacity, high amounts of Fe/Al oxyhydroxide, and acidic pH. Arsenic lability increased considerably 30 days after fertilizer application. Overall, As lability was mainly influenced by soil mineralogical and chemical properties, i.e., Fe/Al oxyhydroxide, pH, organic matter, and fertilizer application. 相似文献
20.
Caetano Luiz Beber Rafael da Rosa Couto Paulo Emílio Lovato Jean-Philippe Guillemin Bernard Nicolardot Ricardo Bergamo Schenato Jucinei José Comin 《Environmental Earth Sciences》2018,77(14):532
The green revolution laid the foundations of modern agriculture, by using science and technology to produce more from same resources. The pesticides contributed to agricultural output in the last decades; however, their use has resulted in environmental pollution, health problems, soil and water contamination and negative impact on biota. The impacts of agricultural activities to the environment depended on the practices adopted during the production process. Measurement tools to assess the impacts of those practices are necessary to improve agricultural systems and must be evaluated in different ecosystems. Different soils, climates and crops impose many phytosanitary arrangements. This complex network and the fact that most of the indicators and measurement tools are developed for temperate climates makes it difficult to quantify the environmental impacts under subtropical regions. The I-Phy index is a predictive indicator that assesses the risks of pesticide usage in agriculture and identifies as to which practices generate the main environmental impacts of pesticides. The objective of this study was to test the suitability of the I-Phy index for subtropical conditions and, if suitable, compare the pesticide risk between two regions. Five crops were assessed under three different cropping systems: no-tillage, minimal tillage and conventional tillage. The I-Phy index was sensitive in both regions and capable of identifying that no-tillage generally presented risks of environmental pollution slightly lower than the other tillage systems. The results of I-Phy index showed that high environmental vulnerability of the fields and the numerous applications of active ingredients with high risks resulted in high risks of general contamination. The application of I-Phy on these two case studies showed the indicator can be useful as a support tool to farmers, research and extension institutions pursuing management practices with lower impact on the environment. 相似文献