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Groundwater Samples (groundwater + sample)
Selected AbstractsGroundwater quality in the semi-arid region of the Chahardouly basin, West IranHYDROLOGICAL PROCESSES, Issue 16 2008A. Taheri Tizro Abstract Chahardouly basin is located in the western part of Iran and is characterized by semi-arid climatic conditions and scarcity in water resources. The main aquifer systems are developed within alluvial deposits. The availability of groundwater is rather erratic owing to the occurrence of hard rock formation and a saline zone in some parts of the area. The aquifer systems of the area show signs of depletion, which have taken place in recent years due to a decline in water levels. Groundwater samples collected from shallow and deep wells were analysed to examine the quality characteristics of groundwater. The major ion chemistry of groundwater is dominated by Ca2+ and HCO3,, while higher values of total dissolved solids (TDS) in groundwater are associated with high concentrations of all major ions. An increase in salinity is recorded in the down-gradient part of the basin. The occurrence of saline groundwater, as witnessed by the high electrical conductivity (EC), may be attributed to the long residence time of water and the dissolution of minerals, as well as evaporation of rainfall and irrigation return flow. Based on SAR values and sodium content (%Na), salinity appears to be responsible for the poor groundwater quality, rendering most of the samples not suitable for irrigation use. Copyright © 2007 John Wiley & Sons, Ltd. [source] Field analyses of RDX and TCE in groundwater during a GCW pilot studyREMEDIATION, Issue 1 2002Andrew C. Elmore Contaminant concentrations in groundwater are typically analyzed using traditional laboratory analytical procedures approved by the Environmental Protection Agency (EPA) or state regulatory agencies. The use of off-site laboratories provides very high-quality water quality data at a relatively high cost in terms of time and money. Yet there are many instances when it is desirable to have water quality data measured in the field. The field methods for measuring water quality typically cost much less than the corresponding laboratory methods. However, the usability of the field data may be uncertain when the results are qualitatively compared to duplicate laboratory results. Groundwater samples collected during a groundwater circulation well pilot study were analyzed using field kits to measure concentrations of trichloroethylene (TCE) and the explosive compound known as RDX. A subset of the samples was split for duplicate laboratory analysis. Linear regression analysis and relative percent difference analysis were performed on the duplicate results to evaluate the comparability of the field and laboratory data. The data analyses were also used to evaluate the concept that the field kits were more accurate for specific concentration ranges, as well as the concept the field kit results would improve as field personnel gained experience with the field analysis procedures. © 2002 Wiley Periodicals, Inc. [source] Gene transcript analysis of assimilatory iron limitation in Geobacteraceae during groundwater bioremediationENVIRONMENTAL MICROBIOLOGY, Issue 5 2008Regina A. O'Neil Summary Limitations on the availability of Fe(III) as an electron acceptor are thought to play an important role in restricting the growth and activity of Geobacter species during bioremediation of contaminated subsurface environments, but the possibility that these organisms might also be limited in the subsurface by the availability of iron for assimilatory purposes was not previously considered because copious quantities of Fe(II) are produced as the result of Fe(III) reduction. Analysis of multiple Geobacteraceae genomes revealed the presence of a three-gene cluster consisting of homologues of two iron-dependent regulators, fur and dtxR (ideR), separated by a homologue of feoB, which encodes an Fe(II) uptake protein. This cluster appears to be conserved among members of the Geobacteraceae and was detected in several environments. Expression of the fur-feoB-ideR cluster decreased as Fe(II) concentrations increased in chemostat cultures. The number of Geobacteraceae feoB transcripts in groundwater samples from a site undergoing in situ uranium bioremediation was relatively high until the concentration of dissolved Fe(II) increased near the end of the field experiment. These results suggest that, because much of the Fe(II) is sequestered in solid phases, Geobacter species, which have a high requirement for iron for iron-sulfur proteins, may be limited by the amount of iron available for assimilatory purposes. These results demonstrate the ability of transcript analysis to reveal previously unsuspected aspects of the in situ physiology of microorganisms in subsurface environments. [source] Molecular diversity and characterization of nitrite reductase gene fragments (nirK and nirS) from nitrate- and uranium-contaminated groundwaterENVIRONMENTAL MICROBIOLOGY, Issue 1 2003Tingfen Yan Summary Nitrate-contaminated groundwater samples were analysed for nirK and nirS gene diversity. The samples differed with respect to nitrate, uranium, heavy metals, organic carbon content, pH and dissolved oxygen levels. A total of 958 nirK and 1162 nirS clones were screened by restriction fragment length polymorphism (RFLP) analysis: 48 and 143 distinct nirK and nirS clones, respectively, were obtained. A single dominant nirK restriction pattern was observed for all six samples and was 83% identical to the Hyphomicrobium zavarzinii nirK gene. A dominant nirS pattern was observed for four of the samples, including the background sample, and was 95% identical to the nirS of Alcaligenes faecalis. Diversity indices for nirK and nirS sequences were not related to any single geochemical characteristic, but results suggested that the diversity of nirK genes was inversely proportional to the diversity of nirS. Principal component analysis (PCA) of the sites based on geochemistry grouped the samples by low, moderate and high nitrate but PCA of the unique operational taxonomic units (OTUs) distributions grouped the samples differently. Many of the sequences were not closely related to previously observed genes and some phylogenetically related sequences were obtained from similar samples. The results indicated that the contaminated groundwater contained novel nirK and nirS sequences, functional diversity of both genes changed in relation to the contaminant gradient, but the nirK and nirS functional diversity was affected differently. [source] Investigation of an onsite wastewater treatment system in sandy soil: Site characterization and fate of anionic and nonionic surfactantsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2002Allen M. Nielsen Abstract This study reports on the fate of linear alkylbenzene sulfonate (LAS), alcohol ethoxylate (AE), and alcohol ether sulfate (AES) surfactants in a home septic system near Jacksonville (FL, USA) that has been used since 1976. The drainfield at this site resides in fine sand (<6% silt and clay) with an unsaturated zone that ranges from 0 to 1.3 m. During the wettest times of the year, it is likely that effluent from the septic system passes directly into the groundwater without exposure to an unsaturated zone of soil. Groundwater was collected during two sampling events, representing seasonal high and low groundwater table levels, and analyzed for the surfactants LAS, AES, and AE. During the wet season, the unsaturated zone was approximately 0.01 m beneath the drainfield. During the dry season, the unsaturated zone was about 0.4 m below the drainfield. Alcohol ethoxylate was not detected in any groundwater samples during either sampling. Alcohol ether sulfate was not found in the dry season sampling, but traces of AES had migrated downgradient about 4.7 m horizontally and 1.8 m vertically in the wet season. Linear alkylbenzene sulfonate was detected in some dry season samples and had moved downgradient some 11.7 m horizontally and 3.7 m vertically in the wet season. These observations demonstrate that these surfactants were removed to a great extent; otherwise, they would have traveled more than 260 m downgradient, which is the calculated distance that a conservative tracer like bromide would have moved downgradient over the life of the system. The most likely removal mechanisms for these surfactants were biodegradation and sorption. Therefore, this study indicates that LAS, AE, and AES are readily removed from groundwater in soils below septic system drainfields even in situations with minimal unsaturated soil zones. [source] Mixed aerobic and anaerobic microbial communities in benzene-contaminated groundwaterJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2009A. Aburto Abstract Aims:, To investigate the factors affecting benzene biodegradation and microbial community composition in a contaminated aquifer. Methods and Results:, We identified the microbial community in groundwater samples from a benzene-contaminated aquifer situated below a petrochemical plant. Eleven out of twelve groundwater samples with in situ dissolved oxygen concentrations between 0 and 2·57 mg l,1 showed benzene degradation in aerobic microcosm experiments, whereas no degradation in anaerobic microcosms was observed. The lack of aerobic degradation in the remaining microcosm could be attributed to a pH of 12·1. Three groundwaters, examined by 16S rRNA gene clone libraries, with low in situ oxygen concentrations and high benzene levels, each had a different dominant aerobic (or denitrifying) population, either Pseudomonas, Polaromonas or Acidovorax species. These groundwaters also had syntrophic organisms, and aceticlastic methanogens were detected in two samples. The alkaline groundwater was dominated by organisms closely related to Hydrogenophaga. Conclusions:, Results show that pH 12·1 is inimical to benzene biodegradation, and that oxygen concentrations below 0·03 mg l,1 can support aerobic benzene-degrading communities. Significance and Impact of the Study:, These findings will help to guide the treatment of contaminated groundwaters, and raise questions about the extent to which aerobes and anaerobes may interact to effect benzene degradation. [source] A new approach to determine method detection limits for compound-specific isotope analysis of volatile organic compoundsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2006Maik A. Jochmann Compound-specific isotope analysis (CSIA) has been established as a useful tool in the field of environmental science, in particular in the assessment of contaminated sites. What limits the use of gas chromatography/isotope ratio mass spectrometry (GC/IRMS) is the low sensitivity of the method compared with GC/MS analysis; however, the development of suitable extraction and enrichment techniques for important groundwater contaminants will extend the fields of application for GC/IRMS. So far, purge and trap (P&T) is the most effective, known preconcentration technique for on-line CSIA with the lowest reported method detection limits (MDLs in the low,µg/L range). With the goal of improving the sensitivity of a fully automated GC/IRMS analysis method, a commercially available P&T system was modified. The method was evaluated for ten monoaromatic compounds (benzene, toluene, para -xylene, ethylbenzene, propylbenzene, isopropylbenzene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, fluorobenzene) and ten halogenated volatile organic compounds (VOCs) (dichloromethane, cis -1,2-dichloroethene, trans -1,2-dichloroethene, carbon tetrachloride, chloroform, 1,2-dichloroethane, trichloroethene, tetrachlorethene, 1,2-dibromoethane, bromoform). The influence of method parameters, including purge gas flow rates and purge times, on ,13C values of target compounds was evaluated. The P&T method showed good reproducibility, high linearity and small isotopic fractionation. MDLs were determined by consecutive calculation of the ,13C mean values. The last concentration for which the ,13C value was within this iterative interval and for which the standard deviation was lower than ±0.5, for triplicate measurements was defined as the MDL. MDLs for monoaromatic compounds between 0.07 and 0.35,µg/L are the lowest values reported so far for continuous-flow isotope ratio measurements using an automated system. MDLs for halogenated hydrocarbons were between 0.76 and 27,µg/L. The environmental applicability of the P&T-GC/IRMS method in the low-µg/L range was demonstrated in a case study on groundwater samples from a former military air field contaminated with VOCs. Copyright © 2006 John Wiley & Sons, Ltd. [source] Arsenic and thallium data in environmental samples: Fact or fiction?REMEDIATION, Issue 4 2010Susan D. Chapnick Matrix effects may increasingly lead to erroneous environmental decisions as regulatory limits or risk-based concentrations of concern for trace metals move lower toward the limits of analytical detection. A U.S. Environmental Protection Agency Office of Technical Standards Alert estimated that environmental data reported using inductively coupled plasma spectrometry (ICP-AES) has a false-positive rate for thallium of 99.9 percent and for arsenic of 25 to 50 percent. Although this does not seem to be widely known in the environmental community, using three case studies, this article presents data in environmental samples that demonstrate severe matrix effects on the accuracy of arsenic and thallium results. Case Study 1 involves soil results with concentrations that approached or exceeded the applicable regulatory soil cleanup objectives of 13 mg/kg for arsenic and 2 mg/kg for thallium. Reanalysis using ICP coupled with a mass spectrometer (ICP-MS) confirmed all thallium results were false positives and all arsenic results were biased high, concluding no action was required for soil remediation. Case Study 2 involves groundwater results for thallium at a Superfund site, where thallium was detected in groundwater up to 21.6 , g/L using ICP-AES. Reanalysis by ICP-MS reported thallium as nondetect below the applicable regulatory level in all samples. ICP-MS is usually a more definitive and accurate method of analysis compared to ICP-AES; however, this is not always the case, as we demonstrate in Case Study 3, using data from groundwater samples at an industrial site. Through a weight-of-evidence approach, it is demonstrated that although method quality control results were acceptable, interferences in some groundwater samples caused biased high results for arsenic using ICP-MS, which were significantly lower when reanalyzed using hydride generation atomic fluorescence spectrometry. Causes of these interference effects and conclusions from the three case studies to obtain accurate metal data for site assessment, risk characterization, and remedy selection are discussed. © 2010 Wiley Periodicals, Inc. [source] | ||||||||||