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1.
《Applied Geochemistry》2004,19(2):215-230
Sources of As in the Ganges sediments and microbial mechanisms of its release in groundwater were examined in the present study, where the authors have systematically examined the pertinent mineral species present in the sediments using XRD, TEM-EDS and EPMA techniques. The results show several As-bearing minerals in the Ganges sediments, in western Bangladesh. Iron-sulfide minerals consist of near-amorphous and/or crystalline precursors of framboidal pyrite and pyrite both of which contain As. Several types of Fe oxyhydroxides (oxides), which contain variable amounts of As were also found in muddy sediments. The content of As increases from Fe-oxides to the precursors of framboidal pyrite and pyrite. Four different chemical forms of As from the core sediments were determined. The sequentially extracted chemical forms are as follows: (1) acid soluble form (As mainly fixed in carbonates), (2) reducible form (As fixed in Fe- and/or Mn-oxides), (3) organic form, (4) insoluble form (As fixed mainly in sulfide and rarely in silicate minerals). Arsenic is dominantly sorbed on to Fe- and/or Mn-oxides, organic forms and sulfide minerals in most samples, although their relative abundances differ in different samples. Geomicrobial culture experiments were carried out to test the hypothesis that microbial processes play a key role in the release of As in groundwater. Batch culture and circulating water system experiments were designed using the sediments from Bangladesh. In the batch experiments, As was released at low Eh values a few days after adding nutrients containing glucose, polypepton and yeast extract, urea and fertilizer under a dominantly N2 atmosphere. This contrasts with the control experiments without nutrients. Circulating water experiments with sand layer in a N2 atmosphere showed similar results. These results support the hypothesis that microbial processes mediate the release of As into groundwater under reducing conditions. Glucose and polypepton used in the experiments may correspond to C and N sources, respectively. Younger sediments contain abundant organic matter, which is easily used by bacteria. So, the enhanced bacterial activity may correspond to simulation of accelerated natural diagenetic process using organic matter, or some fertilizer/wastewater effects.  相似文献   

2.
桂江流域地下水污染途径及防控措施研究   总被引：1，自引：1，他引：0  
何愿  张颖  朱明 《中国岩溶》2015,34(4):387-394
对桂江流域开展岩溶地下水污染调查发现:流域内地下水污染源分为“三氮”污染源、重金属污染源、有机污染源三类;“三氮”污染源主要包括工业、养殖和生活三类污水、生活垃圾渗滤液、农业施用氮肥等;重金属污染主要来自工矿企业;有机污染来自工业、养殖业。污染途径主要有孤峰平原的分散入渗式、孤峰平原的脚洞灌入式、峰丛洼地的消水洞灌入式、溶丘谷地的入渗式和峰丛峰林谷地的天窗灌入式等五类。并对88组地下水样品测试结果进行多指标地下水污染综合评价,结果表明36.5%的水点为“三氮”污染,多以分散入渗进入地下水,其污染形态呈面状分布;15.3%的水点为重金属污染,主要通过峰丛洼地消水洞灌入式补给和溶丘谷地入渗补给两种途径,呈点状分布于污染场地附近;3.49%的水点为有机污染,主要为分散入渗补给途径,污染呈短线状或点状分布。   相似文献   

3.
The groundwater leve in the Tokyo area had declined to about 60 m below the surface because of excess withdrawal of groundwater from various aquifers. Many construction workers died due to oxygen deficiency at construction sites from 1960 to 1980, the period of decreasing groundwater level. The compressed air in pneumatic foundation construction sites passed easily through the aquifer, and the oxygen in it was consumed by ferrous ions oxidizing to ferric ions. During periods of high barometric pressure, atmospheric air penetrates into the strata and it is deoxygenated there. Suffocation occurred not only at construction sites in underground excavations, but also in residences in Tokyo. Such acidents have become less frequent with recovery of the pore-water pressure in aquifers, which has accompanied the recovery of the groundwater level since 1972.With the recovery of the pore-water pressure and the groundwater level in the aquifer, fires and explosions resulting from gushes of methane have occurred in Tokyo lowlands since 1973. These blow-off gases are classified into two types: Kameido and Asakusa.The gas of the Kameido type originates from the Kazusa Group and migrates into upper alluvial deposits or Pleistocene sediments because of the recovery of pore-water pressure in the Kazusa Group. The gas of the Asakusa type formed from the air that penetrated the aquifers during the period of low groundwater level. Methane was produced by the depletion of oxygen accumulated in alluvial deposits and Pleistocene sediments. This gas blows off through wells in alluvial deposits and Pleistocene sediments at times of low barometric pressure. Accidents of the Asakusa type will not happen when the groundwater level and pore-water pressure in alluvial and Pleistocene sediments is restored to previous levels.  相似文献   

4.
Uranium(VI) adsorption onto aquifer sediments was studied in batch experiments as a function of pH and U(VI) and dissolved carbonate concentrations in artificial groundwater solutions. The sediments were collected from an alluvial aquifer at a location upgradient of contamination from a former uranium mill operation at Naturita, Colorado (USA). The ranges of aqueous chemical conditions used in the U(VI) adsorption experiments (pH 6.9 to 7.9; U(VI) concentration 2.5 · 10−8 to 1 · 10−5 M; partial pressure of carbon dioxide gas 0.05 to 6.8%) were based on the spatial variation in chemical conditions observed in 1999-2000 in the Naturita alluvial aquifer. The major minerals in the sediments were quartz, feldspars, and calcite, with minor amounts of magnetite and clay minerals. Quartz grains commonly exhibited coatings that were greater than 10 nm in thickness and composed of an illite-smectite clay with occluded ferrihydrite and goethite nanoparticles. Chemical extractions of quartz grains removed from the sediments were used to estimate the masses of iron and aluminum present in the coatings. Various surface complexation modeling approaches were compared in terms of the ability to describe the U(VI) experimental data and the data requirements for model application to the sediments. Published models for U(VI) adsorption on reference minerals were applied to predict U(VI) adsorption based on assumptions about the sediment surface composition and physical properties (e.g., surface area and electrical double layer). Predictions from these models were highly variable, with results overpredicting or underpredicting the experimental data, depending on the assumptions used to apply the model. Although the models for reference minerals are supported by detailed experimental studies (and in ideal cases, surface spectroscopy), the results suggest that errors are caused in applying the models directly to the sediments by uncertain knowledge of: 1) the proportion and types of surface functional groups available for adsorption in the surface coatings; 2) the electric field at the mineral-water interface; and 3) surface reactions of major ions in the aqueous phase, such as Ca2+, Mg2+, HCO3−, SO42−, H4SiO4, and organic acids. In contrast, a semi-empirical surface complexation modeling approach can be used to describe the U(VI) experimental data more precisely as a function of aqueous chemical conditions. This approach is useful as a tool to describe the variation in U(VI) retardation as a function of chemical conditions in field-scale reactive transport simulations, and the approach can be used at other field sites. However, the semi-empirical approach is limited by the site-specific nature of the model parameters.  相似文献   

5.
Interplay of S and As in Mekong Delta sediments during redox oscillations   总被引：1，自引：1，他引：0  
The cumulative effects of periodic redox cycling on the mobility of As,Fe,and S from alluvial sediment to groundwater were investigated in bioreactor experiments.Two particular sediments from the alluvial floodplain of the Mekong Delta River were investigated:Matrix A(14 m deep)had a higher pyrite concentration than matrix B(7 m deep)sediments.Gypsum was present in matrix B but absent in matrix A.In the reactors,the sediment suspensions were supplemented with As(Ⅲ)and SO_4~(2-),and were subjected to three full-redox cycles entailing phases of nitrogen/CO_2,compressed air sparging,and cellobiose addition.Major differences in As concentration and speciation were observed upon redox cycling.Evidences support the fact that initial sediment composition is the main factor controlling arsenic release and its speciation during the redox cycles.Indeed,a high pyrite content associated with a low SO_4~(2-)content resulted in an increase in dissolved As concentrations,mainly in the form of As(Ⅲ),after anoxic half-cycles;whereas a decrease in As concentrations mainly in the form of As(Ⅴ),was instead observed after oxic half-cycles.In addition,oxic conditions were found to be responsible for pyrite and arsenian pyrite oxidation,increasing the As pool available for mobilization.The same processes seem to occur in sediment with the presence of gypsum,but,in this case,dissolved As were sequestered by biotic or abiotic redox reactions occurring in the Fe—S system,and by specific physico-chemical condition(e.g.pH).The contrasting results obtained for two sediments sampled from the same core show that many complexes and entangled factors are at work,and further refinement is needed to explain the spatial and temporal variability of As release to groundwater of the Mekong River Delta(Vietnam).  相似文献   

6.
Improved knowledge of processes determining groundwater quality is an important precondition for the solution of various ecological and water management problems. In areas with highly fluctuating groundwater levels, time-limited access, local pollution sources or temporary interactions between surface water and groundwater, a temporary groundwater sampling technique could be of advantage. Furthermore, depth-specific sampling is of high value for investigating groundwater pollution related to seepage or surface water infiltration. A stainless steel core probe has been developed to obtain groundwater samples and to measure the hydraulic head distribution at various defined depths. The sampling technique is applicable only for non-volatile water constituents. An advantage of the core probe is that it can be driven into soil or sediments using ordinary low cost percussion equipment. The probe enables hydraulic head measurements and water sampling over vertical intervals of 0.3 m. Results from field experiments using the stainless steel core probe were in good correspondence with results from groundwater sampling at nearby observation wells. In the upper layer of the aquifer, the intrinsic spatial change in concentrations of sulphate, chloride and other water constituents is a function of distance between observation points and groundwater surface. Results indicate strong effects of a fluctuating groundwater level on groundwater quality at certain depths.  相似文献   

7.
The alluvial aquifer of the Alto Guadalquivir River is one of the most important shallow aquifers in Jaén, Spain. It is located in the central-eastern part of the province, and its groundwater resources are used mainly for crop irrigation in an agriculture-dominated area. Hydrochemical and water-quality data obtained through a 2-year sampling (2004–2006) and analysis program indicate that nitrate pollution is a serious problem affecting groundwater due to the use of nitrogen (N)-fertilizers in agriculture. During the study, 231 water samples were collected from wells and springs to determine water chemistry and the extent of nitrate pollution. The concentration of nitrate in groundwater ranged from 1.25 to 320.88 mg/l. Considerable seasonal fluctuations in groundwater quality were observed as a consequence of agricultural practices and other factors such as annual rainfall distribution and the Guadalquivir River flow regime. The chemical composition of the water is not only influenced by agricultural practices, but also by interaction with the alluvial sediments. The dissolution of evaporites accounts for part of the Na+, K+, Cl−, SO4 2−, Mg2+, and Ca2+, but other processes, such as calcite precipitation and dedolomitization, also contribute to groundwater chemistry.  相似文献   

8.
This work presents results of the hydrogeological and hydrochemical studies on groundwater samples from the alluvial aquifer of Merdja in Tébessa, located in the Western part of this town. Its groundwater resources are used mainly for crop irrigation in an agriculture dominated area. Hydrochemical and water quality data obtained through a sampling period (December 2008) and analysis program indicate that nitrate pollution can be a serious problem affecting groundwater due to the use of nitrogen (N) fertilizers in agriculture. The concentration of nitrate in groundwater ranged from 19 to 281 mg/l. Considerable seasonal fluctuations in groundwater quality were observed as a consequence of agricultural practices and other factors such as annual rainfall distribution and the wadi El Kebir flow regime. The chemical composition of the water is not only influenced by agricultural practices, but also by interaction with the alluvial sediments. The dissolution of evaporites accounts for part of the Na+, K+, Cl?, SO 4 2? , Mg2+, and Ca2+, but other processes, such as calcite precipitation and dedolomitization, also contribute to groundwater chemistry.  相似文献   

9.
石家庄冲积扇含有优质的地下水,是石家庄市区200多万人和工农业用水的主要供水水源.但其地表堆埋了大量的城市垃圾,对地下水源构成严重的污染威胁.通过卫星遥感图像数据解译、现场取样测试等工作,对该地下水源地的环境水文地质条件和垃圾堆放、填埋、分布状况及其对地下水的污染进行了评价,并针对性地提出了应对措施和对策.  相似文献   

10.
Agricultural coastal areas are frequently affected by the superimposition of various processes, with a combination of anthropogenic and natural sources, which degrade groundwater quality. In the coastal multi-aquifer system of Arborea (Italy)—a reclaimed morass area identified as a nitrate vulnerable zone, according to Nitrate Directive 91/676/EEC—intensive agricultural and livestock activities contribute to substantial nitrate contamination. For this reason, the area can be considered a bench test for tuning an appropriate methodology aiming to trace the nitrate contamination in different conditions. An approach combining environmental isotopes, water quality and hydrogeological indicators was therefore used to understand the origins and attenuation mechanisms of nitrate pollution and to define the relationship between contaminant and groundwater flow dynamics through the multi-aquifer characterized by sandy (SHU), alluvial (AHU), and volcanic hydrogeological (VHU) units. Various groundwater chemical pathways were consistent with both different nitrogen sources and groundwater dynamics. Isotope composition suggests a mixed source for nitrate (organic and synthetic fertilizer), especially for the AHU and SHU groundwater. Moreover, marked heterotrophic denitrification and sulfate reduction processes were detected; although, for the contamination related to synthetic fertilizer, the attenuation was inefficient at removing NO3? to less than the human consumption threshold of 50 mg/L. Various factors contributed to control the distribution of the redox processes, such as the availability of carbon sources (organic fertilizer and the presence of lagoon-deposited aquitards), well depth, and groundwater flow paths. The characterization of these processes supports water-resource management plans, future actions, and regulations, particularly in nitrate vulnerable zones.  相似文献   

11.
A depositional model of the lower Pliocene Hagul formation, which is exposed in the East Cairo district (Egypt), is proposed with more than 10 depositional cycles recognized. Field occurrence, detailed petrographic investigation and geochemical analysis revealed that the sediments within each cycle are the result of three sequential sedimentological processes: (1) alluvial sedimentation, (2) calcretization, and (3) precipitation of palustrine carbonate. It was concluded that Hagul formation has been deposited within the distal part of an alluvial plain during three successive climatic conditions: a humid climate during which alluvial sediments were deposited, a semi-arid climate with episodic precipitation which was favorable for pedogenic calcrete development, and a sub-humid climate during which groundwater level was gradually elevated and groundwater calcrete accumulated. Rising groundwater level continued until shallow wetlands covered the area and palustrine limestone was precipitated. Variations in the thickness and the nature of the host sediment, calcrete and palustrine limestone cycle suggest that each of the sedimentation processes varied from cycle to cycle.  相似文献   

12.
Arsenic contamination of groundwater used as drinking water in South Asia poses a serious health threat to the inhabitants living on alluvial plains of the Himalayan foreland of countries like Bangladesh, India, Nepal and Myanmar. Although the geological and geochemical conditions favoring the release of the highly poisonous contaminant from the sediments hosting the groundwater are meanwhile quite well understood, there is still a significant debate about the origin of arsenic. The sediments forming a huge proportion of the Terai (lowlands of Nepal) aquifers are derived from two main sources, (i) sediments deposited by large rivers that erode the upper Himalayan crystalline rocks and (ii) weathered meta-sediments carried by smaller rivers originating in the Siwalik foothills adjacent to the Terai. In this article a so far underestimated source of As is discussed: the peraluminous leucogranites found ubiquitously in the Nepal Himalaya. The relationship between the trace elements analyzed in the groundwater in the Terai and trace elements found in such felsic rocks reflect the origin of the arsenic in the high Himalayas of Nepal. In addition to the high concentration of As, a striking feature is the presence of the lithophile trace elements like Li, B, P, Mn, Br, Sr and U in the groundwater. The mentioned elements point to a felsic initial source like metapelites or leucogranites—all rocks showing a high abundance of especially B, P and As as well as Cd and Pb.  相似文献   

13.
Aquifer sediments from areas of low- and high-As groundwater were characterized mineralogically and geochemically at a field site in the Nadia district of West Bengal, India. Leaching experiments and selective extraction of the sediments were also carried out to understand the release mechanism of As in the sub-surface. The correlation between measured elements (major, minor and trace) from low- and high-As groundwater areas are only significant for As, Fe and Mn. The borehole lithology and percentage of silt and clay fraction demonstrates the dominance of finer sediments in the high-As aquifer. Multivariate analysis of the geochemical parameters showed the presence of four different mineral phases (heavy-mineral fraction, phyllosilicates/biotite/Fe-oxyhydroxides, carbonates and sulphides) in the sediments. Selective extraction of sediment reveals that amorphous Fe-oxyhydroxide acts as a potential sink for As in the sub-surface. The result is consistent with microbially mediated redox reactions, which are controlled in part by the presence of natural organic matter within the aquifer sediments. The occurrences of As-bearing redox traps, primarily formed of Fe- and Mn-oxides/hydroxides, are also important factors that control the release of As into groundwater at the study site.  相似文献   

14.
Mineral assemblages (heavy and light fractions) and sedimentological characteristics of the Quaternary alluvial aquifers were examined in the central Bengal Basin where As concentrations in groundwater are highly variable in space but generally decrease downward. Chemical compositions of sediment samples from two vertical core profiles (2-150 m below ground level, bgl) were analyzed along with groundwater in moderately As-enriched aquifers in central Bangladesh (Manikganj district), and the As mobilization process in the alluvial aquifer is described. Heavy minerals such as biotite, magnetite, amphibole, apatite and authigenic goethite are abundant at shallow (<100 m below ground level (mbgl)) depths but less abundant at greater depths. It is interpreted that principal As-bearing minerals were derived from multiple sources, primarily from ophiolitic belts in the Indus-Tsangpo suture in the northeastern Himalayan and Indo-Burman Mountain ranges. Authigenic and amorphous Fe-(oxy)hydroxide minerals that are generally formed in river channels in the aerobic environment are the major secondary As-carriers in alluvial sediments. Reductive dissolution (mediated by Fe-reducing bacteria) of Fe-(oxy)hydroxide minerals under anoxic chemical conditions is the primary mechanism responsible for releasing As into groundwater. Authigenic siderite that precipitates under reducing environment at greater depths decreases Fe and possibly As concentrations in groundwater. Presence of Fe(III) minerals in aquifers shows that reduction of these minerals is incomplete and this can release more As if further Fe-reduction takes place with increased supplies of organic matter (reactive C). Absence of authigenic pyrite suggests that SO4 reduction (mediated by SO4-reducing bacteria) in Manikganj groundwater is limited in contrast to the southeastern Bengal Basin where precipitation of arsenian pyrite is thought to sequester As from groundwater.  相似文献   

15.
The characterization of river–aquifer connectivity in karst environments is difficult due to the presence of conduits and caves. This work demonstrates how geophysical imaging combined with hydrogeological data can improve the conceptualization of surface-water and groundwater interactions in karst terrains. The objective of this study is to understand the association between the Bell River and karst-alluvial aquifer at Wellington, Australia. River and groundwater levels were continuously monitored, and electrical resistivity imaging and water quality surveys conducted. Two-dimensional resistivity imaging mapped the transition between the alluvium and karst. This is important for highlighting the proximity of the saturated alluvial sediments to the water-filled caves and conduits. In the unsaturated zone the resistivity imaging differentiated between air- and sediment-filled karst features, and in the saturated zone it mapped the location of possible water- and sediment-filled caves. Groundwater levels are dynamic and respond quickly to changes in the river stage, implying that there is a strong hydraulic connection, and that the river is losing and recharging the adjacent aquifer. Groundwater extractions (1,370 ML, megalitres, annually) from the alluvial aquifer can cause the groundwater level to fall by as much as 1.5 m in a year. However, when the Bell River flows after significant rainfall in the upper catchment, river-leakage rapidly recharges the alluvial and karst aquifers. This work demonstrates that in complex hydrogeological settings, the combined use of geophysical imaging, hydrograph analysis and geochemical measurements provide insights on the local karst hydrology and groundwater processes, which will enable better water-resource and karst management.  相似文献   

16.
Our study region is characterized by a varied age detritus Mio-Plio-Quaternary formations. Some training can be an important groundwater sources (alluvial sand, shell, limestone, gravel). Agriculture in the study area is the first socio-economic activity and the largest consumer of water resources. It is therefore necessary to take into account for effective water management. This may causes a risk of pollution of various kinds: agricultural, industrial, and domestic water overlooked the lack of wastewater treatment plants in the region and that all discharges of sewage are dumped into the river are the Rhumel no prior treatment. Wadi Rhumel water pollution factors are multiple and related primarily to the agricultural vocation of the area, the nature of different domestic and industrial discharges. We note that the discharge of wastewater from the town of Tadjenanet and Chelghoum Laid is at wadi Rhumel, the latter during low water turns into open sewer. In times of water shortage, intensive pumping on the outskirts of the wadi locally generates an immigration of a possible pollution load to groundwater. Two major cities in our study area are located along of wadi Rhumel with an estimated population over 100,000 inhabitants. Both towns have uncontrolled landfills where one is located at the upstream of wadi Rhumel. Faced with this alarming environmental situation and the lack of treatment plants, we contribute to the study of the impact of wastewater on the quality of surface and groundwater through a physicochemical analysis interpretation.  相似文献   

17.
潮白河冲洪积扇中上游地区作为北京市最主要地表水和地下水供给区,在城市供水中的作用举足轻重。由于多年连续超采,地下水位持续下降,1999-2013年地下水位下降最大达45 m;应急水源地地区地下水硬度年均上升2.6%,密云十里堡地区地下水硬度和硝酸盐氮超标。通过分析潮白河冲洪积扇区域地下水开发利用、地下水位和水质变化情况以及地下水位变化对地下水水质的影响,认为：超量开采导致的地下水水位下降是引起该区域地下水水质恶化的主要原因之一,控制地下水超量开采和地表水污染,并利用南水北调的水进京之机回灌和停采以涵养地下水,是恢复区域水资源和水环境的良好途径。  相似文献   

18.
Arsenic contamination occurs in groundwater of Bangladesh mainly from the alluvial and deltaic sediments. Arsenic contamination of groundwater in Bangladesh was first detected more than a decade ago and the ’shallow tubewells’ were reported as the main source of arsenic contaminated water. From the nutritional and metabolic points of view, arsenic is likely to adversely affect human health and nutrition. Up to now, several studies have been carried out on this context; however, inadequate knowledge on arsenic sources, mobilization and transport still remains as a constraint due to lack of data, information and technological advances. Thus, a review study has been undertaken on the sources of arsenic, its causes, mobilization, transport, effects on human health, arsenic test procedures and removal methods, in the context of groundwater contamination in Bangladesh, and finally sustainable remedial measures of arsenic have been proposed. This study suggests that laboratory facilities for testing of arsenic and effects of enhanced groundwater pumping, phosphate fertilizer etc., need to be updated, expanded and studied. This review work is significant to further knowledge improvement, as the topic is general and worldwide. It can be concluded that the integration of the proposed remedial measures with the national geographic information system interface database relating to arsenic for analysis, production of hazard maps, and dissemination on television show for the planners, engineers, managers, field supervisors and affected people, can reach at the sustainable solution for mitigating arsenic and associated problems successfully in Bangladesh.  相似文献   

19.
塔城盆地地下水“三氮”污染特征及成因   总被引：1，自引：0，他引：1       下载免费PDF全文
地下水氮元素污染是一个全球性的环境问题,其来源和迁移转化特征是国内外研究的热点。文章以新疆塔城盆地80组地下水样品水化学组分测试结果为依据,研究塔城盆地地下水“三氮”污染特征。结果表明:塔城盆地地下水质量总体较好;对比2017年发布的地下水质量标准,深层承压水“三氮”均未超标;浅层地下水“三氮”污染较轻,“三氮”超标点零星分布于地下水的中下游冲洪积平原区,其中,NO3-N超标率最高,超标率为8.8 %;NO2-N和NH4-N次之,超标率均为1.3 %。沿着地下水流向,从山区到盆地中央的平原区,地下水污染逐渐变重。“三氮”重污染点主要分布在塔城市、额敏县及其周边地区。区内地下水污染点的分布与工矿企业污染源、污水处理厂、垃圾填埋场等大型污染源的分布具有一定的相关性。城市化进程中,生活污水的不合理排放是塔城盆地“三氮”污染的主要来源,而通过排污河流下渗是研究区地下水“三氮”污染的重要途径;氧化还原条件、pH值、包气带岩性结构、补径排条件等是“三氮”迁移转化及其空间分布的主要影响因素。  相似文献   

20.
Hydrogeochemical investigations were carried out in the Dashtestan, the eastern part of Borazjan, with a focus on fluoride content. The study area is underlain by a complex geology that is dominated by three lithological units, namely marl, alluvial sediments, and carbonate rocks. To assess the major geochemical factors controlling the fluoride enrichment in water, 37 groundwater and 12 surface water samples were collected from the three lithological units. Fluoride concentrations ranged up to 3?mg/L, and average concentrations varied from 1.12 (in carbonate aquifers) to 1.73 (in alluvial aquifers) to 1.82?mg/L (in marl aquifers). To study the influence of rocks and soils on groundwater quality, an additional 41 soil and rock samples were also taken and analyzed for fluoride. The order of average fluoride content in both rocks and soils is: marl?>?alluvial sediments?>?limestone, which confirms that marl is a likely source of fluoride.  相似文献   

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