生活垃圾填埋场渗滤液对潜层地下水污染的实验模拟分析——以北京北天堂垃圾填埋场为例

通过对北京市西郊南部北天堂垃圾填埋场渗滤污染组分在含水介质中运移的室内模拟实验分析，揭示了有机污染物等污染组分在含水介质中的运移转化规律，即有机污染物等污染组分在微生物的作用下得到降解；通过阻滞因子和水化学迁移率的计算，得出该含水介质对污染组分的阻滞能力较好。可用水化学迁移率粗略预测不同污染质锋面达到指定地点的时间，为垃圾填埋场地底部防渗层的设计和渗滤液对地下水污染程度的预报提供依据。     

黄河下游平原地下水有机污染特征分析

以大量的地下水测试数据为基础,从污染源分布及水文地质条件入手,对黄河下游平原地下水中有机污染物类型及污染程度进行了深入研究。黄河下游平原地下水普遍受到有机物污染并形成多个典型有机污染区,有机物总检出率为35．5％,检出的有机污染物种类达29种,单个样品检出的有机物种类最多达19种,部分有机物含量超过地下水饮用标准,致使地下水质量恶化。地下水污染区的分布及污染程度与污染源的种类和分布具有很好的相关性。     

山东平原地区浅层地下水有机污染特征分析

山东平原地区浅层地下水普遍受到有机物污染并形成多个有机污染区,检出的有机污染物达29种之多,个别地区有机物含量超过地下水饮用限量标准,致使地下水质量恶化。该文以水文地质条件分析及地下水污染物组分测试为手段,对山东平原区浅层地下水中有机污染种类及污染程度进行了研究,目的在于评价地下水安全性,保护宝贵的地下水资源。     

胜利油田陆上采油区浅层地下水与土壤有机污染特征研究

本文在对胜利油田陆上采油区水文地质条件和污染源现状分析的基础上,对浅层地下水和包气带土壤进行了样品采集、污染物组分测试及污染程度研究,分析研究结果表明:胜利油田陆上采油区浅层地下水和土壤已普遍受有机物污染并形成多个有机污染区,检出的有机污染物达16种之多,个别有机物含量还很高.浅层地下水污染程度受到油田采油井数量、采油...     

鲁北平原浅层地下水有机污染特征及污染来源分析

本文在对鲁北平原水文地质条件及污染源现状分析的基础上,对浅层地下水进行了高密度的样品采集、高精度的污染物组分测试及污染程度研究,分析研究结果表明:鲁北平原浅层地下水在部分地区受到有机物污染,污染程度总体较低,个别地区出现中度污染和重度污染。检出的有机污染物共13种,个别有机物含量高。浅层地下水污染区的分布及污染程度,与油田采油区位置及石油化工企业的分布具有相关性。     

石油碳氢化合物污染含水层的快速氧化还原进程

搜集的六年地下水化学数据显示，经过一段时间后。被石油类碳氢化合物污染的浅含水层的污染物的分布和氧化还原进程已发生了快速的变化。在1990年发生石油泄漏后不久，大量的苯存在于污染源地区，在受污染的地区，地下水中的溶解氧被消耗掉。截止到1994年，Fe(Ⅲ)和硫酸盐的减少是显著的晚期电子接收过程。非常有意义的是，1994年的溶解甲烷在测量下限以下。这暗示了缺乏有意义的甲烷群。然而，到1996年，含水层沉积物中固相Fe(Ⅲ)的氢氧化物的消耗和地下水中溶解硫酸盐的消耗导致了甲醇类的大量繁殖。在1996年—2000年期间，水化学数据显示甲醇类的新陈代谢更加普遍了，对沉积物的萃取物16s-rDNA进行分子分析，显示了更加多元化的甲醇类的存在，相对于污染羽中心的外面，它和水化学数据反映的变化是一致的。该快速氧化还原过程反映了几种因素，包括大量污染物，相对快速的地下水流动(0．3m／day)(1foot／day)和原始存在于含水层沉积物中的可由细菌引起减少的低浓度Fe(Ⅲ)氢氧化物(1umol／g)。这些结果表明，在一定水文条件下受石油碳氢化合物污染含水层中的氧化还原条件。在时间和空间上能快速发生变化，并且有效的固相Fe(Ⅲ)的氢氧化物影响了变化的速度。     

煤矸石浸泡污染物溶解释放规律研究--阜新市新邱露天煤矿不同风化煤矸石在不同固液比条件下浸泡实验

论文对新邱露天矿不同风化程度的煤矸石在不同固液比条件下溶解释放污染物的规律进行了浸泡实验研究。结果表明:煤矸石溶解释放的主要污染物为总硬度(CaCO3)、硫酸盐(SO42-)、钠(Na )、总溶解性固体(TDS)、氟化物(F-)、耗氧量(OC)和总铁(Fe)等,氯化物(Cl-)、锰(Mn)、锌(Zn)等少量,其它重金属和砷等微量。pH值接近中性。煤矸石风化程度越高,溶解释放的无机盐类污染物量越多,新鲜混合煤矸石溶解释放出较高的氟化物(F-)、耗氧量(OC)和总铁(Fe);固液比对煤矸石中污染物的溶解释放有重要影响。固液比越小,浸泡液中污染物浓度越低,越有利于煤矸石中污染物的溶解释放,单位质量煤矸石溶解释放的污染物量越多,煤矸石中污染物的溶解释放规律受扩散控制;在同一固液比条件下,各污染物浓度变化与浸泡时间成对数曲线关系,即Ct=a bLogt。     

基于GMS的广西平果铝赤泥堆场岩溶含水层溶质运移模拟

广西平果铝赤泥堆场在生产氧化铝时会产生碱性比较高的赤泥淋滤液,同时也会产生硫酸盐、氟化物、铝等污染物。赤泥淋虑液下渗到地下水污染比较敏感的岩溶区会对地下水岩溶含水层造成污染。运用GMS软件模拟赤泥淋滤液在岩溶含水系统的运移情况,找出污染物的运移规律、来预测赤泥堆场的建设对地下含水层的污染,确定污染物的范围和浓度的分布。模拟结果表明:堆场离南部的岩溶管道有一定的距离,下渗的赤泥淋滤液不能很快的流入岩溶管道中,污染物主要是在裂隙和孔隙的岩体介质中运移,主要以分子扩散的形式运动,运动的速度十分缓慢。污染晕大致呈圆形向四周扩散,30 a后扩散带向东北向扩散的最远距离才645 m,堆场的建设不会对附近的岩溶含水层造成污染。     

山东昌邑市地表水及浅层地下水有机污染分布特征研究

昌邑市城区及相关产业园都坐落于潍河冲洪积扇上。2014-2015年进行的昌邑市地下水环境调查项目在该区采集了53组地表水、地下水样品,检测有机污染物90项,地表水中检出的有机污染组分24种,占检测总种类的26. 67%;地下水中检出的有机污染组分14种,占检测总种类的15. 5%;二者均未发现有机物超标现象。地表水有机污染物主要来源于当地企业排污,污水经污水处理厂处理后,有机物种类急剧降低,但很难根除,在远离排污口,有机物的检出种类减少。低强度的污染源对地下水的污染小,地下水的有机污染检出呈点状,具分散性;强度较高且持续的污染会使进入地下水中的有机物呈片状分布,有机物类型为难以降解的三氯甲烷等为主。此项研究能为昌邑市及类似地区产业布局调整、污水排放处理提供科学支撑。     

非平衡吸附模型在研究渗滤液对土壤污染影响中的应用

分析了有机污染物在土壤中的迁移转化机理，建立了非平衡吸附作用下渗滤液中有机污染物在土壤中迁移转化的动力学模型，给出了模型的数值解法，模拟出渗滤液在非平衡吸附作用下的污染过程；同时还探讨了模型参数降雨量p，垃圾土土层的厚度h，含水率θ等对有机污染物运移的影响。结果表明：在总的污染源一定的情况下，降雨量的增大和污染土层厚度的增大会使得下层土壤中有机物的浓度降低，为定量研究有机污染物在土壤-水环境系统中分配与归宿提供理论依据，同时也可为监测、治理和恢复地下水污染提供一定的科学根据。     

Redox evolution in glacial drift aquifers: role of diamicton units in reduction of Fe(III)

High iron concentrations create water quality problems for municipal use in glacial drift aquifer units. The chemical evolution of oxic groundwater in shallow aquifer units to anoxic groundwater in deeper aquifer units, in which soluble Fe(II) is stable, is attributed to coupled reduction of Fe(III) on aquifer solids with oxidation of organic carbon. The objective of this study was to characterize the distribution of organic carbon in aquifer and aquitard sediments to determine the availability of potential electron donors to drive these reactions. To do this, four complete rotasonic cores in a glacial aquifer/aquitard system were sampled at close intervals for analyses of grain-size distribution and organic carbon content. The results indicate significantly higher organic carbon concentrations in diamicton (till) units that function as aquitards, relative to coarse-grained aquifer units. In addition, readily reducible iron content in the diamicton units and lower aquifer unit materials is sufficient to produce far more dissolved iron than is present in the aquifer. Groundwater evolves to the level of iron reduction as a terminal electron-accepting process as it moves downward through aquitard units along flow paths from upland recharge areas to downgradient discharge areas. Deeper aquifer units are therefore unlikely to contain groundwater with low iron concentration.     

Column tests to enhance sulphide precipitation with liquid organic electron donators to remediate AMD-influenced groundwater

Dump groundwaters in the former East-German lignite-mining district are characterized by high amounts of ferrous iron and sulphate. Both the pyrite weathering products endanger the surface water quality when discharged into lakes. Only the precipitation of both contaminants in the subsurface can prevent the further contamination of surface waters. The two-step process of microbial catalyzed sulphate reduction and iron sulphide precipitation is limited by the low availability of natural organic substances as electron donators. Therefore, a new remediation technique is developed based on the injection of a liquid organic electron donator (methanol) into the contaminated aquifer. The saturated aquifer is used as a bioreactor, where iron monosulphides are precipitated in the groundwater-filled pore space. Column experiments were performed under natural pressure and temperature conditions with natural anoxic groundwater and original sediments to test the remediation technology. The test showed that a complete iron removal (4 mmol/l), even under rather acid conditions (pH 3.8), is possible after having established an active sulphate reducer population. The turnover of the added organic substance with sulphate is complete and the amount of the resulting sulphide controls the effluent pH. In addition, intensified microbial activity triggers the turnover of natural organic substances. Also, natural Fe(III) hydroxides react with the sulphide produced. Considering the long natural retention times (decades), artificially enhanced FeS precipitation is spontaneous, although it shows kinetic behaviour in the range of days. In light of the promising results, the development of a field scale application of this technique is considered to be necessary. It will have to focus on the improved precipitation control of the FeS in the subsurface.     

The Differential Geochemical Behavior of Arsenic and Phosphorus in the Water Column and Sediments of the Saguenay Fjord Estuary, Canada

The distribution and partitioning of dissolved andparticulate arsenic and phosphorus in the water columnand sediments of the Saguenay Fjord in Quebec, Canada,are compared. In addition, selective and/or sequentialextractions were carried out on the suspendedparticulate matter (SPM) and solid sediments tocontrast their geochemical behaviors in this naturalaquatic system.Results of our analyses show that both arsenic andsoluble reactive phosphate are actively scavenged fromthe water column by settling particles. Upon theiraccumulation at the sediment-water interface some Asand P may be released to porewaters following thedegradation of organic matter to which they areassociated. The porewater concentrations are, however,limited by their strong affinity for authigenic,amorphous iron oxyhydroxides which accumulate in theoxic sediments near the sediment-water interface.The geochemical behavior of arsenic and phosphorusdiverge most strikingly upon the development of anoxicconditions in the sediments. Following their burial inthe anoxic zone, amorphous iron oxyhydroxides arereduced and dissolved, releasing phosphate and arsenicto the porewaters. We observed, however, thatporewater arsenic concentrations increase at shallowerdepths than phosphate in the sediments. The reductionof arsenate, As(V), to arsenite, As(III), and itsdesorption prior to the reductive dissolution of thecarrier phase(s) may explain this observation.Driven by the strong concentration gradientestablished in the suboxic zone, phosphate diffuses uptowards the oxic layer where it is readsorbed byauthigenic iron oxyhydroxides. In the organic-rich andrapidly accumulating sediments at the head of theFjord, porewater sulfate depletion and the resultingabsence of a sulfide sink for Fe(II), may lead to theformation of vivianite in the fermentation zone, apotential sink for phosphate. Arsenite released to theporewaters in the suboxic and anoxic zones of thesediments diffuses either down, where it is adsorbedto or incorporated with authigenic iron sulfides, orup towards the oxic boundary. Arsenite appears tomigrate well into the oxic zone where it may beoxidized by authigenic manganese oxides before beingadsorbed by iron oxyhydroxides present at the samedepth. Whereas, in the absence of authigenic carbonatefluorapatite precipitation, the ability of oxicsediments to retain mineralized phosphate is afunction of their amorphous iron oxyhydroxide content,arsenic retention may depend on the availability ofmanganese oxides, the thickness of the oxic layer and,its co-precipitation with iron sulfides at depth.     

Occurrence,distribution and source of arsenic in deep groundwater wells in Maydavood area,southwestern Iran

Groundwater in some deep wells of Maydavood aquifer, southwestern Iran, contains relatively high concentrations of arsenic. Detailed hydrochemical analysis of these groundwaters (with ICP-OES instrument) showed that concentrations of iron, manganese, nickel, and vanadium are also high in them and concentrations of total arsenic in 81% of deep wells are greater than World Health Organization’s permissible value (10 ppb). XRF analysis of surrounding geological formations and aquifer sediments proposed that original source of arsenic in aquifer material can be attributed to minerals from Asmari Formation. It appears that a key mechanism for arsenic mobilizing to deep wells is microbial biodegradation of petroleum related organic matters (PROMs), which exist in aquifer sediments and originates from the bedrock of the aquifer (Gachsaran Formation). This process is followed by microbially mediated reductive dissolution of arsenic-bearing iron/manganese oxyhydroxides/oxides and further by nickel and vanadium mobilizing to groundwater. According to hydrogeochemical conditions and cluster analysis, water wells in Maydavood aquifer are divided to four subgroups: the wells with mildly reducing condition (subgroup I), moderately reducing condition (subgroup II), reducing condition (subgroup III), and high reducing condition (subgroup IV). Affected wells to arsenic are belonged to subgroups III and IV.     

Role of organic matter in the accumulation of platinum in oceanic ferromanganese deposits

In order to elucidate possible processes leading to platinum accumulation in ferromanganese deposits, we analyzed published data on the interaction of dissolved platinum species in different valence states with iron and manganese oxyhydroxides under oceanic conditions and experimentally studied the kinetics of sorption of inorganic and organic complexes of platinum (II) and platinum (IV) on synthetic iron and manganese oxyhydroxides and natural materials (marine colloids, and ferromanganese crust samples). The role of dissolved and suspended particulate aquatic organic matter in the sorption accumulation of platinum was evaluated. Possible reasons for the preferential (compared with other noble metals) accumulation of platinum in oceanic ferromanganese deposits were discussed.     

银北平原浅层高砷地下水砷富集水化学特征研究

宁夏银川平原是继河套平原之后,在黄河流域发现的又一个高砷地下水分布区.为了总结其高砷地下水的水化学特征,并探索水化学因素对地下水砷释放和富集的影响机制,本文以银川平原北部（银北平原）作为典型研究区,采取野外水文地质调查、水样采集与测试、砷与水化学组分散点图相关分析及水文地球化学方法进行了综合研究.结果表明,银北平原地下水砷含量在0.2~177 μg/L之间;高砷地下水（大于50 μg/L） pH值多在7.5~8.5,水化学类型主要为HCO3-Na·Ca、Cl·HCO₃-Na及Cl·HCO₃-Na·Ca型,E_h多在-200~-100 mV.银北平原砷含量较高的地下水中COD、NH₄⁺、HCO3^-含量相应也较高,而NO3^-和SO₄^2-含量较低.高砷富有机质的冲-湖积含水层经过长期演化,形成偏碱性的中强还原性地下水环境和特殊的水化学特征,也具备极大的砷释放能力.较高的pH导致砷从铁锰氧化物或氢氧化物等水合物或黏土矿物表面解吸.其次部分铁锰氧化物在高pH、低E_h条件下可被还原为低价态可溶性铁锰,从而使与其结合的砷也得以释放进入地下水中.此外重碳酸根与砷酸根、亚砷酸根的竞争吸附行为促使含水层砷的解吸.     

Arsenic mobilization in shallow aquifers of Datong Basin: Hydrochemical and mineralogical evidences

To better understand the sources and mobilization processes responsible for arsenic enrichment in groundwater in the central part of Datong Basin where serious arsenic poisoning cases have been reported, hydrochemical characteristics of the groundwater and the geochemical and mineralogical features of the aquifer sediments were studied. The aqueous arsenic levels are strongly depth-dependent in the study area and the high arsenic concentrations are found at depths between 15 m and 60 m, with a maximum up to 1820 μg/L. The hydrochemical characteristics of high arsenic groundwater from the Datong Basin indicate that the mobilization of arsenic is related to reductive dissolution of Fe oxides/oxyhydroxides and/or desorption from the Fe oxides/oxyhydroxides at high pH (above 8.0). The bulk chemical results of sediments show the arsenic and iron are moderately correlated, suggesting that arsenic is associated with iron-bearing minerals. Results of sequential-extraction experiment show that solid-phase arsenic is similarly distributed among the different pools of reservoir in the aquifer sediments. Strongly adsorbed arsenic and co-precipitated arsenic are its dominant species in the solid-phase. Geochemical studies using chemical analysis, X-ray diffraction and scanning electron microscopy on magnetically separated fractions demonstrate that iron oxides/oxyhydroxides with residual magnetite and chlorite, illite, iron oxides/oxyhydroxides-coated quartz and feldspar, and ankerite are the dominant carriers of arsenic in the sediments. The major processes of arsenic mobilization are probably linked to desorption of As from Fe oxides/oxyhydroxides and reductive dissolution of Fe-rich phases in the aquifer sediments under reducing and alkaline conditions.     

Coupled Reactive Transport Modeling of Redox Processes in a Nitrate-Polluted Sandy Aquifer

The reactive transport modeling of a complicated suite of reactions apparent in the aquifer during the application of N-containing fertilizers is reported. The unconfined sandy aquifer can be subdivided into an oxic zone which contains groundwater with oxygen and nitrate and an anoxic zone characterized by elevated iron and sulfate concentrations in groundwater. Oxygen and nitrate are being reduced by pyrite and organic matter that commonly apparent in the aquifer. The oxidation of pyrite is modeled using the local equilibrium approach, whereas decomposition of organic matter, with the adoption of kinetic approach. The system is buffered by dissolution of aluminum and iron oxides. The modeling process is a two-step procedure. First, the processes are modeled in the one-dimensional (1D) column using PHREEQC code. Subsequently, the calibrated and verified data were copied and used in two-dimensional (2D) PHAST model. Prior to the performance of reactive transport modeling operations with PHAST, a reliable flow model was executed. Finally, predictions are made for the distribution of water chemistry for the year 2008. Model predicts that sulfate derived from the ongoing pyrite oxidation is reduced by the dissolved organic carbon at the higher depth and forms pyrite by the reaction with iron. The results of this study highlight the importance of understanding the interplay between the transport and chemical reactions that occur during the input of nitrate to the aquifer. Reactive transport modeling incorporating the use of a newly developed code PHAST have proved to be a powerful tool for analyzing and quantifying such interactions.     

四氯乙烯在不同地下水环境的生物共代谢降解

四氯乙烯是地下水中常见的污染物,采用生物方法进行处理的优点是可以实现无害化、无二次污染、处理成本低。四氯乙烯只能在厌氧条件下发生还原脱氯,目前对产甲烷环境下四氯乙烯的降解研究较多,而对较弱还原环境,如反硝化、铁锰还原和硫酸盐还原环境下四氯乙烯的脱氯行为研究甚少。本文采用批实验,研究了在不同地下水环境,包括反硝化、铁还原、硫酸盐还原、混合电子受体和天然地下水环境下四氯乙烯的脱氯性能。结果表明,铁还原环境的四氯乙烯脱氯效果最好,天然地下水环境次之,四氯乙烯的去除率分别达到91.34%和84.71%,四氯乙烯很快转化为三氯乙烯,并可以进一步转化为二氯乙烯,四氯乙烯的降解符合准一级反应动力学方程。在反硝化、硫酸盐还原、混合电子受体环境,四氯乙烯的去除以挥发为主,降解只占很小的比例,且最终的降解产物只有三氯乙烯。地下水中三价铁的存在,对于四氯乙烯脱氯起促进作用;而当地下水中硝酸盐和硫酸盐的浓度较高时,四氯乙烯脱氯受到抑制。     

The origin and isotopic composition of dissolved sulfide in groundwater from carbonate aquifers in Florida and Texas

The δ³⁴S values of dissolved sulfide and the sulfur isotope fractionations between dissolved sulfide and sulfate species in Floridan ground water generally correlate with dissolved sulfate concentrations which are related to flow patterns and residence time within the aquifer. The dissolved sulfide derives from the slow in situ biogenic reduction of sulfate dissolved from sedimentary gypsum in the aquifer. In areas where the water is oldest, the dissolved sulfide has apparently attained isotopic equilibrium with the dissolved sulfate (Δ³⁴S = 65 per mil) at the temperature (28°C) of the system. This approach to equilibrium reflects an extremely slow reduction rate of the dissolved sulfate by bacteria; this slow rate probably results from very low concentrations of organic matter in the aquifer.In the reducing part of the Edwards aquifer, Texas, there is a general down-gradient increase in both dissolved sulfide and sulfate concentrations, but neither the δ³⁴S values of sulfide nor the sulfide-sulfate isotope fractionation correlates with the ground-water flow pattern. The dissolved sulfide species appear to be derived primarily from biogenic reduction of sulfate ions whose source is gypsum dissolution although upgradient diffusion of H₂S gas from deeper oil field brines may be important in places. The sulfur isotope fractionation for sulfide-sulfate (about 38 per mil) is similar to that observed for modern oceanic sediments and probably reflects moderate sulfate reduction in the reducing part of the aquifer owing to the higher temperature and significant amount of organic matter present; contributions of isotopically heavy H₂S from oil field brines are also possible.