Evaluation of petroleum hydrocarbon biodegradation in shallow groundwater by hydrogeochemical indicators and C, S-isotopes

Biodegradation is one of the main natural attenuation processes in groundwater contaminated with petroleum hydrocarbons. In this work, preliminary studies have been carried out by analyzing the concentrations of total petroleum hydrocarbons (TPH), dissolved inorganic carbon (DIC), dominant terminal electron accepters or donors, as well as δ ¹³C_DIC and δ ³⁴S_SO4, to reveal the biodegradation mechanism of petroleum hydrocarbons in a contaminated site. The results show that along groundwater flow in the central line of the plume, the concentrations of electron acceptors, pH, and E _h increased but TPH and DIC decreased. The δ ¹³C_DIC values of the contaminated groundwater were in the range of ?14.02 to ?22.28 ‰_PDB and ?7.71 to 8.36 ‰_PDB, which reflected a significant depletion and enrichment of ¹³C, respectively. The increase of DIC is believed to result from the non-methanogenic and methanogenic biodegradation of petroleum hydrocarbon in groundwater. Meanwhile, from the contaminated source to the downgradient of the plume, the ³⁴S in the contaminated groundwater became more depleted. The Rayleigh model calculation confirmed the occurrence of bacterial sulfate reduction as a biodegradation pathway of the petroleum hydrocarbon in the contaminated aquifers. It was concluded that stable isotope measurements, combined with other biogeochemical measurements, can be a useful tool to prove the occurrence of the biodegradation process and to identify the dominant terminal electron-accepting process in contaminated aquifers.     

当地下水邂逅DNA:石油类有机污染及其生物降解

地下水科学与工程研究发展到今日,已经成为一门涉及多个领域的综合性学科。地下水污染的控制和修复研究更需要跨学科的技术和知识支持,而生物修复作为一种高效低耗修复的技术成为环境领域的研究热点。微生物因其自身特性及其对污染的降解主导特征对确定有机物污染场地的永续修复具有重要意义。简要地综述了地下水有机污染及其原位修复、有机污染物和地下环境微生物的交互作用,进一步聚焦生物降解机制、生物修复和细菌研究。在此基础上以某石油污染场地地下水为例,进行了地下水中分离微生物菌株及其降解特征的实验研究。结果表明:放线菌降解效果最好,细菌和真菌次之;两两组合降解效果好于单菌,表明存在协同作用;不同菌株混合降解率较低,表明具有拮抗作用。通过动力学实验得出对TPH的降解符合一级反应动力学方程及其降解速度和降解半衰期。就微生物对有机组分降解而言,烷烃和总石油烃降解规律相似;难降解组分降解率低,后期因烷烃转化使其浓度升高;苯浓度变化不大。微生物活性实验表明:活菌总数和脱氢酶活性与降解率呈正相关变化。运用生理生化及分子生物学方法鉴定得出了具体的菌种。     

The effects of petroleum-contaminated soil on photosynthesis of <Emphasis Type="Italic">Amorpha fruticosa</Emphasis> seedlings

A pot experiment was conducted to monitor the dynamic response of photosynthesis of Amorpha fruticosa seedlings to different concentrations of petroleum-contaminated soils from April to September. The results showed that the photosynthetic rates, stomatal conductance and transpiration rate of seedlings significantly decreased in 5–20 g kg^?1 petroleum-contaminated soil during the three given sampling period of July 31 (early), August 30 (mid-term) and September 29 (late). However, the intercellular CO₂ concentration significantly increased in 10 g kg^?1 contaminated soil, while declined in 20 g kg^?1 contaminated soil during the early sampling period as well as in 20 g kg^?1 contaminated soil during the late sampling period. The leaf relative water content of seedlings significantly increased in 20 g kg^?1 contaminated soil during the early sampling period, while it dropped dramatically in 15–20 g kg^?1 contaminated soil during the late sampling period. The contents of chlorophyll a, chlorophyll b and the total chlorophyll of seedlings showed a sharp decline during the three sampling periods in contaminated soil. Comprehensively, considering the negative effects of petroleum on the photosynthesis, growth performance and remediation effect on petroleum of A. fruticosa seedlings, this plant was tolerant of petroleum-contaminated soil and was potentially useful for the phytoremediation of petroleum-contaminated sites in northern Shaanxi, China.     

Isolation of wells contaminated by tannery industries using principal component analysis

The groundwater in the upper Kodaganar basin is contaminated due to the discharge of effluents from tannery industries. The water in the wells, whose physico-chemical characteristics are altered due to the influence of the effluents, is statistically analyzed. The physico-chemical variables such as EC, Na⁺, K⁺, Ca²⁺, Mg²⁺, F^?, Cl^?, HCO₃ ^?,CO₃ ^2?, NO₃ ^?, SO₄ ^2?, pH, and Cr_total were used for this study. An attempt was made to identify the contaminated wells based on suitability for drinking, suitability for industrial requirements, and through principal component analysis (PCA). Classification based on suitability helped in identifying the contaminated wells. However, this resulted in failure when identifying the wells that are contaminated by tanneries. PCA has proved to be effective in the segregation of contaminated wells influenced by tannery industries. The physico-chemical variables that are 13 in number are transformed into two orthogonal components and Eigen values based on the variance. The Eigen values are used to select the first two principal components PC1 (7.26) and PC2 (2.24) that accounted for 73.04% variance in the data. The components of the variables and the wells are plotted in a biplot to isolate the contaminated samples. The contaminated samples are analyzed in the spatial domain in geographic information system and found to be clustered around the tannery belt. The study reveals that 35% of the samples are contaminated due to discharge from tannery industries.     

某石油类污染场地地下水石油烃生物降解的地球化学证据

生物降解地下水石油烃会改变地下水环境的水化学组成,因此可以通过分析污染晕中电子受体、生物降解代谢产物以及重要的地球化学参数量值变化获得生物降解的地球化学证据。本次在对某石油污染场地地质、水文地质条件、污染源污染方式调查基础上,根据地下水样测试结果,详细分析了地下水石油烃污染分布特征、污染晕中指示生物降解作用的电子受体、代谢产物以及重要地球化学参数的空间变化规律,研究结果表明:污染场地内存在氧还原、硝酸盐还原、硫酸盐还原等生物降解作用,其中硫酸盐还原是污染场地地下水石油烃生物降解的优势反应; 在沿地下水流向上,TPH浓度、HCO₃^-浓度和碱度逐渐降低,Eh、电子受体(DO、NO₃^-、SO₄^2-)浓度逐渐升高; 在垂直于地下水流向上,从中心向两侧各组分也呈相似的变化规律。     

Assessment of groundwater quality and contamination problems ascribed to an abandoned uranium mine (Cunha Baixa region,Central Portugal)

The assessment of groundwater quality and its environmental implications in the region of the abandoned Cunha Baixa uranium mine (Central Portugal) was carried out from 1995 to 2004. Shallow groundwater is the major water supply source for irrigation in the neighbourhood of Cunha Baixa village. Water samples from the mine site as well as from private wells were collected in order to identify the mining impact on water composition, the extent of contamination and the seasonal and temporal groundwater quality variations. Some of the sampled private wells contain waters having low pH (<4.5–5) and high values of EC, TDS, SO₄, F, Ca, Mg, Al, Mn, Ni, U, Zn and ²²⁶Ra. The wells located through the ESE–WSE groundwater flow path (1 km down gradient of the mining site) display the most contaminated water. In the summer season, the levels of SO₄, Al, Mn, and U were 50–120 times higher than those registered for uncontaminated waters and exceeded the quality limits for irrigation purposes, presenting soil degradation risks. Nevertheless, this study indicates that groundwater contamination suffered a small decrease from 1999 to 2004. The bioaccumulation of toxic metals such as Al, Mn, and U within the food chain may cause a serious health hazard to the Cunha Baixa village inhabitants.     

Groundwater chemical and fecal contamination assessment of the Jerba unconfined aquifer,southeast of Tunisia

Located in the southeast of Tunisia, on the Mediterranean Sea, Jerba Island has a semiarid climate condition. The surface water scarcity has made groundwater the main source to supply the domestic, touristic, and agricultural water demand. Unconfined aquifer is a vulnerable costal aquifer system that undergoes several phenomena. This work aims at assessing the geochemical and bacteriological groundwater quality, defining groundwater pollution sources and promoting sustainable development and effective management of groundwater resources in Jerba Island. Data were collected after the wet season in 2014 from 79 wells. Electric conductivity, pH, TDS, and major and fecal tracers (total coliforms, thermotolerant coliforms, Escherichia coli, and Salmonella) were analyzed. Geochemical modeling including the relationships between geochemical tracers Na⁺ vs. Cl^?, Ca²⁺ vs. Cl^?, K⁺ vs. Cl^?, representative ionic ratios (Br^?/Cl^?, Na⁺/Cl^?, Mg²⁺/Ca²⁺), and statistical analysis were used to specify major process contributing to groundwater pollution and main factors controlling groundwater mineralization in the island. Groundwater varieties were hydrochemically classified into three types in terms of salinity values: group 1 (8.86%) to fresh water, group 2 (27.84%) to brackish water, and group 3 (63.29%) belongs to saline water. In addition, groundwater quality revealed high concentrations in chemical pollution tracers (Na⁺, Cl^?, SO₄ ^2?, and NO₃ ^?) and fecal tracers. Besides, most of the sampled wells were contaminated with nitrate (50.63%). Also, thermotolerant coliforms and E. coli were detected in all groundwater samples (96.2% of wells). Results indicated that the Jerba shallow aquifer was under serious threat from both natural and anthropogenic contamination. However, the wild discharge of domestic effluents, septic tanks, and sewage were the main origins of underground water contamination in Jerba Island. The reduction of fecal sources, through constructing normalized latrines is thus recommended.     

Use of discriminant statistical analysis to determine the origin of an industrial pollution type in the aquiferous system of the area of Berrahal, Algeria

The continuous increase of industrial activities in the area of Berrahal (northeast of Algeria) resulted in an increase of waste disposal, inducing environmental pollution and contamination of groundwater. Available data on groundwater contamination were used to develop a statistical study for contaminated regions and to identify exposure scenarios of pollution. Chemical analysis of the samples shows that water of most wells and drillings is in bad quality or not drinkable, whereas statistical processing of these data by principal component analysis and discriminant factorial analysis suggests that wastewater coming from companies of the industrial park of Berrahal is very rich in organic pollutants (high percentages of BOD₅ and NO₂ ^?) and has high mineralization (has strong concentration in major elements and high electric conductivity); these constitute the main factors of the deterioration of the quality of this water. The considered exposure pathways were drinking water exploited from wells and drillings implanted in this area and its contact with soil (ingestion and dermal contact) that could threaten either humans or wildlife, on site or off site. In addition, groundwater was considered to be a potential risk pathway, especially for the ecosystem of Lake Fetzara and for the aquiferous system.     

Induced degradation of crude oil mediated by microbial augmentation and bulking agents

Different bacterial and fungal strains, isolated from petroleum hydrocarbon-contaminated soil, were tested, in isolation as well as in combination, for their ability to degrade total petroleum hydrocarbon (TPH) in soil samples spiked with crude oil (2, 5 or 10 %, w/w) for 30 days. The selected combination of bacterial and fungal isolates, i.e., Pseudomonas stutzeri BP10 and Aspergillus niger PS9, exhibited the highest efficiency of TPH degradation (46.7 %) in soil spiked with 2 % crude oil under control condition. Further, when this combination was applied under natural condition in soil spiked with 2 % (w/w) crude oil along with inorganic fertilizers (NPK) and different bulking agents such as rice husk, sugarcane, vermicompost or coconut coir, the percent degradation of TPH was found to be maximum (82.3 %) due to the presence of inorganic fertilizers and rice husk as bulking agent. Further, results showed that the presence of NPK and bulking agents induced the activity of degradative enzymes, such as catalase (0.718 m mol H₂O₂ g^?1), laccase (0.77 µmol g^?1), dehydrogenase (37.5 µg g^?1 h^?1), catechol 1, 2 dioxygenase (276.11 µ mol g^?1) and catechol 2, 3 dioxygenase (15.15 µ mol g^?1) as compared to control (without bioaugmentation). It was inferred that the selected combination microbes along with biostimulants could accentuate the crude oil degradation as evident from the biostimulant-induced enhanced activity of degradative enzymes.     

Groundwater beneath the urban area of Khan Younis City,southern Gaza Strip (Palestine): assessment for multi-domestic purposes

The present study research investigation is aimed to assess the groundwater quality for the urban area in Khan Younis City, southern Gaza Strip, for multi-domestic purposes. The physicochemical analysis of the groundwater wells shows the major ions in the order of Na⁺ > Mg²⁺ > Ca²⁺ > B³⁺ > K⁺ and Cl^? > HCO₃ ^? > SO₄ ^2? > NO₃ ^2? > F^? > PO₄ ^3?. Groundwater quality is classified as very hard-brackish water type. Ninety-five percent of the wells are classified as saline water type with high NO₃ ^2? concentrations. Based on water quality index (WQI), the groundwater falls into one of three categories: fair water (10%), poor water (15%), very poor (45%), and worst (30%). The high WQI values are because of high Na⁺, Cl^?, SO₄ ^2?, and NO₃ ^2? concentrations, while synthetic pollution index (SPI) values indicate that most about 80% of the wells are seriously polluted. Langelier Saturation Index (LSI) indicates that most of data are either slightly scale forming or corrosive water or slightly corrosive but non-scale forming, and 75% of the wells are suitable for construction purposes (have SO₄ ^2? concentrations <300 mg/L). The groundwater reaches alarming situation, where almost chemically unsuitable for drinking purposes and the water to be used after proper treatment such as desalination.     

Natural-abundance radiocarbon as a tracer of assimilation of petroleum carbon by bacteria in salt marsh sediments

The natural abundance of radiocarbon (¹⁴C) provides unique insight into the source and cycling of sedimentary organic matter. Radiocarbon analysis of bacterial phospholipid lipid fatty acids (PLFAs) in salt-marsh sediments of southeast Georgia (USA)—one heavily contaminated by petroleum residues—was used to assess the fate of petroleum-derived carbon in sediments and incorporation of fossil carbon into microbial biomass. PLFAs that are common components of eubacterial cell membranes (e.g., branched C₁₅ and C₁₇, 10-methyl-C₁₆) were depleted in ¹⁴C in the contaminated sediment (mean Δ¹⁴C value of +25 ± 19‰ for bacterial PLFAs) relative to PLFAs in uncontaminated “control” sediment (Δ¹⁴C = +101 ± 12‰). We suggest that the ¹⁴C-depletion in bacterial PLFAs at the contaminated site results from microbial metabolism of petroleum and subsequent incorporation of petroleum-derived carbon into bacterial membrane lipids. A mass balance calculation indicates that 6-10% of the carbon in bacterial PLFAs at the oiled site could derive from petroleum residues. These results demonstrate that even weathered petroleum may contain components of sufficient lability to be a carbon source for biomass production by marsh sediment microorganisms. Furthermore, a small but significant fraction of fossil carbon is assimilated even in the presence of a much larger pool of presumably more-labile and faster-cycling carbon substrates.     

Groundwater and surface-water utilisation using a bank infiltration technique in Malaysia

Bank infiltration (BI) is one of the solutions to providing raw water for public supply in tropical countries. This study in Malaysia explores the use of BI to supplement a polluted surface-water resource with groundwater. Three major factors were investigated: (1) contribution of surface water through BI to the resulting abstraction, (2) input of local groundwater, and (3) water-quality characteristics of the resulting water supply. A geophysical method was employed to define the subsurface geology and hydrogeology, and isotope techniques were performed to identify the source of groundwater recharge and the interaction between surface water and groundwater. The physicochemical and microbiological parameters of the local surface-water bodies and groundwater were analyzed before and during water abstraction. Extracted water revealed a 5–98 % decrease in turbidity, as well as reductions in HCO₃ ^?, Cl^?, SO₄ ^2?, NO₃ ^?, Ca²⁺, Al³⁺ and As concentrations compared with those of Langat River water. In addition, amounts of E. coli, total coliform and Giardia were significantly reduced (99.9 %). However, water samples from test wells during pumping showed high concentrations of Fe²⁺ and Mn²⁺. Pumping test results indicate that the two wells used in the study were able to sustain yields.     

Recovery of groundwater in the Sanriku region contaminated by the tsunami inundation from the 2011 Tohoku earthquake

Many wells in the Sanriku region used as sources for water supply systems were heavily contaminated by the tsunami of the 2011 great Tohoku earthquake on March 11 in 2011. To better understand the nature of the groundwater contamination by the tsunami inundation and to clarify the recovery process of contaminated groundwater at the study wells, groundwater monitoring has been conducted once or twice yearly since early summer in 2011. High and abnormal values of electric conductivity (EC), chloride ion concentration (CIC), Na⁺, Ca⁺, heavy metal ions, and heavier isotopes of the contaminated groundwater were also obtained in April and June 2011. The chemical elements have rapidly and exponentially decreased as a result of effective pumping of the contaminated groundwater from the study wells and because of abundant rainfall in 2011. In April 2015 (about 4 years after the tsunami inundation), the CIC and EC of the contaminated groundwater of two study wells in Minamisanriku town had reached pre-inundation values. The estimated residence times of groundwater of the two study wells were 105–118 days in the full-day pumping stage and 910–1000 days in the daytime-only pumping stage.     

Distribution of total petroleum hydrocarbons in Dezful aquifer,Southwest of Iran

Determination of total petroleum hydrocarbon distribution (TPH) in groundwater of Dezful aquifer was the main purpose of this study. The study area, which is located between latitudes 32°00′ and 32°35′?N and longitudes 48°10′ and 49°35′?E, covers about 1,920 km² in the north of Khuzestan Province, Iran. Hydrocarbon pollutants in the area were being released into the aquifer, from a variety of sources. An oil pipe crash accident, which occurred on 19 Feb. 2009 in the vicinity of the northern part of the study area, released about 6,000 barrels of crude oil to the Karkhe River. Other possible sources of TPH in the region are asphalt factories, gas stations, and the Sabzab oil pump station. Since the main source of drinking water in the Dezful area is groundwater reservoirs, this study would be very crucial, especially when there is considerable agricultural activity in the area as well. In order to determine the presence of TPH and heavy metals in the groundwater, samples were taken from wells with different usage within two periods, i.e., in Nov. 2008 and May 2009. The second sampling operation was carried out to determine the effect of the accident in the water resources. In situ groundwater parameter measurements including pH, dissolved oxygen, temperature, and electrical conductivity were also carried out in the field. Based on the results, there are four zones in the study area which were contaminated with TPH from different origins: (1) southeast of Dezful City, which was contaminated by Shokati gas station; (2) southeast of Shush City, which was contaminated by an asphalt factory; (3) southwest of Dezful City, which was contaminated by Sabzab oil pump station; and (4) the shores of Karkhe River which were contaminated due to the pipeline crash accident. This could be a serious threat to the environment and human health because TPH concentration was higher than the EPA standard in the study area. Heavy metals were not distributed in a uniform pattern in the aquifer. The concentrations were lower than the contamination level based on the EPA drinking standard, and there was no meaningful relation between concentrations of TPH and the heavy metals. It was recommended that a monitoring network should be designed to monitor oil contaminants in the ground and surface water monthly because of importance of the water resources and presence of potential oil contaminant sources.     

Role of geophysical and hydrogeological techniques in EIA studies to identify TSDF site for industrial waste management

This paper deals with the importance of integrated hydrogeological, geological and geophysical applications in identifying suitable site for treatment, storage and disposal facility (TDSF) for industrial waste management. The pollution control authorities (Civic body) have a mandate to provide proper TSDF for the industrial zones. One such zone of 2800 acres, established by State Industries Promotion Corporation of Tamil Nadu (SIPCOT) at Perundurai in southern India, is selected to identify suitable TSDF site. The zone is envisaged to cater 22500 MTA (metric tones per annum) of industrial waste generated by 565 units. Hydrogeological and geological setup forms an important criterion in the process of environmental impact assessment (EIA) to establish proposed activity. Hydrogeological, geophysical and socio-economic/ecological studies were carried out to identify suitable TSDF site. Vertical electrical sounding (VES), multi-electrode resistivity imaging (MERI), ground penetrating radar (GPR) scanning, and infiltration tests were performed within the proposed TSDF site of 50 acres land. An inventory of 54 key wells includes depth to water level (varies from 9.7 to 15 m, below ground level) and water chemistry (pH, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, HCO ₃ ^? , SO ₄ ^2? , NO ₃ ^? and F^?) helped in identifying physical environment around (5 km radius) proposed TSDF site. Geophysical and hydrogeological investigations verified with drillings (at 5 locations) within the proposed TSDF site resulted, shallow hard rock at 4.5 m depth, the absence of groundwater, and low infiltration rate (4.3 cm/hour) of soil in the western side (45 acres) of proposed 50 acres land reveals suitability of TSDF site.     

Hydrogeochemical evaluation of fractured Limestone aquifer by applying a geochemical model in eastern Nile Valley,Egypt

Rock water interactions play an important role in the flow of groundwater. Groundwater samples were collected from deep production wells with depths ranging from 120 to 230 m. Complete chemical analysis of 40 groundwater samples was collected from the fractured limestone aquifer including major cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and major anions (Cl^?, SO₄ ^2?, HCO₃ ^?, CO₃ ^2?). A geochemical modeling (NETPATH Software) was applied for environmental simulate net geochemical mass-balance reactions between initial and final waters along a hydrologic flow path. This program simulates selected evolutionary waters for every possible combination of the plausible phases that account for the composition of a selected set of chemical constraints in the system. The groundwater of the Eocene aquifer mainly belongs to fairly fresh water with salinity contents ranging from 228 to 3595 ppm. The measured groundwater levels range between 8 and 25 m near the river Nile to the limestone plateau (eastwards). Consequently, groundwater flows from east to westward toward the river Nile. Groundwater aquifer in the study area is mainly composed of fractured limestone; the saturated states of the PCO₂, calcite, aragonite, dolomite, siderite, gypsum, anhydrite, hematite, and goethite in addition to H₂ gas were estimated. The undersaturated state of carbon dioxide reflects closed conditions and very low probability of recent recharge, and it reveals also the high tendency of water to precipitates carbonate species. Undersaturation by carbonate minerals is only restricted to some pockets distributed on the different places of the aquifer in the study area. The majority of groundwater samples of Eocene aquifer in the study area indicated that groundwater is not suitable for irrigation with treatment and requires good drainage.     

Isotope Geochemistry of Groundwater from Fractured Dolomite Aquifers in Central Slovenia

The hydrogeochemistry and isotope geochemistry of groundwater from 85 wells in fractured dolomite aquifers of Central Slovenia were investigated. This groundwater represents waters strongly influenced by chemical weathering of dolomite with an average of δ¹³C_CARB value of +2.2 ‰. The major groundwater geochemical composition is HCO₃ ^? > Ca²⁺ > Mg²⁺. Several differences in hydrogeochemical properties among the classes of dolomites were observed when they were divided based on their age and sedimentological properties, with a clear distinction of pure dolomites exhibiting high Mg²⁺/Ca²⁺ ratios and low Na⁺, K⁺ and Si values. Trace element and nutrient concentrations (SO₄ ^2?, NO₃ ^?) were low, implying that karstic and fractured dolomite aquifers are of good quality to be used as tap water. Groundwater was generally slightly oversaturated with respect to calcite and dolomite, and dissolved CO₂ was up to 46 times supersaturated relative to the atmosphere. The isotopic composition of oxygen (δ¹⁸O_H2O), hydrogen (δD_H2O) and tritium ranged from ?10.3 to ?8.4 ‰, from ?68.5 to ?52.7 ‰ and from 3.5 TU to 10.5 TU, respectively. δ¹⁸O and δD values fell between the GMWL (Global Meteoric Water Line) and the MMWL (Mediterranean Meteoric Water Line) and indicate recharge from precipitation with little evaporation. The tritium activity in groundwater suggests that groundwater is generally younger than 50 years. δ¹³C_DIC values ranged from ?14.6 to ?9.3 ‰ and indicated groundwater with a contribution of degraded organic matter/dissolved inorganic carbon in the aquifer. The mass balances for groundwater interacting with carbonate rocks suggested that carbonate dissolution contributes from 43.7 to 65.4 % and degradation of organic matter from 34.6 to 56.3 %.     

Geochemical evaluation of nitrate and fluoride contamination in varied hydrogeological environs of Prakasam district,southern India

Hydrogeochemical controlling factors for high rate of groundwater contamination in stressed aquifer of fractured, consolidated rocks belonging to semi-arid watershed are examined. The groundwater in mid-eastern part of Prakasam district confining to Musi-Gundlakamma sub-basins is heavily contaminated with nitrate and fluoride. Distinct water chemistry is noticed among each group of samples segregated based on concentration of these contaminants. The nitrate is as high as 594 mg/l and 57 % of the samples have it in toxic level as per BIS drinking water standards, so also the fluoride which has reached a maximum of 8.96 mq/l and 43 % of samples are not fit for human consumption. Nitrate contamination is high in shallow aquifers and granitic terrains, whereas fluoride is in excess concentration in deeper zones and meta-sediments among the tested wells, and 25 % of samples suffer from both NO₃ ^? and F^? contamination. Na⁺ among cations and HCO₃ ^? among anions are the dominant species followed by Mg²⁺ and Cl^?. The NO₃ ^?-rich groundwater is of Ca²⁺–Mg²⁺–HCO₃ ^?, Ca²⁺–Mg²⁺–Cl^? and Na⁺–HCO₃ ^? type. The F^?-rich groundwater is dominantly of Na⁺–HCO₃ ^? type and few are of Na⁺–SO₄ ^2? type, whereas the safe waters (without any contaminants) are of Ca²⁺–Mg²⁺–HCO₃ ^?– and Na⁺–HCO₃ ^? types. High molecular percentage of Na⁺, Cl^?, SO₄ ^2? and K^? in NO₃ ^? rich groundwater indicates simultaneous contribution of many elements through domestic sewerage and agriculture activity. It is further confirmed by analogous ratios of commonly associated ions viz NO₃ ^?:Cl^?:SO₄ ^2? and NO₃ ^?:K⁺:Cl^? which are 22:56:22 and 42:10:48, respectively. The F^? rich groundwater is unique by having higher content of Na⁺ (183 %) and HCO₃ ^? (28 %) than safe waters. The K⁺:F^?:Ca²⁺ ratio of 10:5:85 and K⁺:F^?: SO₄ ^2? of 16:7:77 support lithological origin of F^? facilitated by precipitation of CaCO₃ which removes Ca²⁺ from solution. The high concentrations of Na⁺, CO₃ ^? and HCO₃ ^? in these waters act as catalyst allowing more fluorite to dissolve into the groundwater. The indices, ratios and scatter plots indicate that the NO₃ ^? rich groundwater has evolved through silicate weathering-anthropogenic activity-evapotranspiration processes, whereas F^? rich groundwater attained its unique chemistry from mineral dissolution-water–rock interaction-ion exchange. Both the waters are subjected to external infusion of certain elements such as Na⁺, Cl^?, NO₃ ^? which are further aggravated by evaporation processes leading to heavy accumulation of contaminants by raising the water density. Presence of NO₃ ^? rich samples within F^? rich groundwater Group and vice versa authenticates the proposed evolution processes.     

The Water Framework Directive: Can more information be extracted from groundwater data? A case study of Seewinkel,Burgenland, eastern Austria

Water protection is one of the most important goals in environmental protection. The Clean Water Act in the USA and the Water Framework Directive (WFD) in Europe are the legal frameworks to facilitate the achievement of this goal. The question is raised of whether more information can be extracted from WFD-related groundwater data. To answer it, a methodology has been developed that is easy to use and could be implemented into official practice. A case study is presented in which the groundwater data of a sodic area in Austria (Seewinkel) is assessed. Eighteen parameters in groundwater sampled from 23 wells (1991–2011) were analyzed. With basic statistics, trend-, cluster-, Wilks’ λ and spatial sampling density analysis, local phosphorus and boron phenomena were described, along with the determining role of sulphate, groundwater flow, and the oxygen gradient in the area. As a final step, the spatial sampling density was determined. Regarding the current set of parameters, all the sampling sites are necessary and only in the case of certain parameters (Ca²⁺, Mg²⁺, K⁺, NO₃ ^?, pH) could one sampling site be abandoned. The methodology applied brings a new perspective to exploring groundwater data collected according to the requirements of the WFD.     

Ion chemistry of groundwater and the possible controls within Lhasa River Basin,SW Tibetan Plateau

In order to study the major ion chemistry and controls of groundwater, 65 groundwater samples were collected and their major ions measured from wells within Lhasa River Basin. Groundwater has the characteristics of slightly alkaline and moderate total dissolved solid (TDS). TDS concentration ranged from 122.0 to 489.9 mg/L with a median value of 271.2 mg/L. Almost all the groundwater samples suited for drinking and irrigation. The major cations of groundwater are Ca²⁺ and Mg²⁺, accounting for 59.6 and 31.3% of the cations, respectively. Meanwhile, HCO₃^? and SO₄^2? constituted about 56.7 and 36.9% of the anions, respectively, in Lhasa River Basin. The hydrochemical type of groundwater is HCO₃-SO₄-Ca-Mg. The chemical composition of groundwater samples located in the middle of Gibbs model, which indicates that the major chemical process of groundwater is controlled by rock weathering. Carbonate weathering was the dominant hydro-geochemical process controlling the concentration of major ions in groundwater within Lhasa River Basin, but silicate weathering also plays an important role.