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1.
The screened auger is a laser-slotted, hollow-stem auger through which a representative sample of ground water is pumped from an aquifer and tested for water-quality parameters by appropriate field-screening methods. Screened auger sampling can be applied to ground water quality remedial investigations, providing:(1) a mechanism for determining a monitoring well's optimal screen placement in a contaminant plume; and (2) data to define the three-dimensional configuration of the contaminant plume.
Screened auger sampling has provided an efficient method for investigating hexavalent chromium and volatile organic compound contamination in two sandy aquifers in Cadillac, Michigan. The aquifers approach 200 feet in thickness and more than 1 square mile in area. A series of screened auger borings and monitoring wells was installed, and ground water was collected at 10-foot intervals as the boreholes were advanced to define the horizontal and vertical distribution of the contaminant plumes. The ability of the screened auger to obtain representative ground water samples was supported by the statistical comparison of field screening results and subsequent laboratory analysis of ground water from installed monitoring wells.  相似文献   

2.
Nolan BT 《Ground water》2001,39(2):290-299
Characteristics of nitrogen loading and aquifer susceptibility to contamination were evaluated to determine their influence on contamination of shallow ground water by nitrate. A set of 13 explanatory variables was derived from these characteristics, and variables that have a significant influence were identified using logistic regression (LR). Multivariate LR models based on more than 900 sampled wells predicted the probability of exceeding 4 mg/L of nitrate in ground water. The final LR model consists of the following variables: (1) nitrogen fertilizer loading (p-value = 0.012); (2) percent cropland-pasture (p < 0.001); (3) natural log of population density (p < 0.001); (4) percent well-drained soils (p = 0.002); (5) depth to the seasonally high water table (p = 0.001); and (6) presence or absence of a fracture zone within an aquifer (p = 0.002). Variables 1-3 were compiled within circular, 500 m radius areas surrounding sampled wells, and variables 4-6 were compiled within larger areas representing targeted land use and aquifers of interest. Fitting criteria indicate that the full logistic-regression model is highly significant (p < 0.001), compared with an intercept-only model that contains none of the explanatory variables. A goodness-of-fit test indicates that the model fits the data well, and observed and predicted probabilities of exceeding 4 mg/L nitrate in ground water are strongly correlated (r2 = 0.971). Based on the multivariate LR model, vulnerability of ground water to contamination by nitrate depends not on any single factor but on the combined, simultaneous influence of factors representing nitrogen loading sources and aquifer susceptibility characteristics.  相似文献   

3.
Approximately 50 percent of the potable, industrial, and agricultural water supply in Venezuela comes from ground water, mined through some 40,000 wells scattered around the country. The majority of the productive aquifers consist of quaternary deposits in mountain valleys and coastal lowlands, all of which are situated in areas with limited or low precipitation. Intensive exploitation of several of these aquifers for the last 30 years has resulted in overdraft conditions and ground water contamination, causing serious socio-economic consequences in various regions of Venezuela. This paper reviews the quality and quantity aspects of overdrafted aquifers in Venezuela, which can he classified into three major categories: (1) aquifers in the coastal lowlands in the stales of Falcon and Zulia of northern Venezuela: (2) the intermontane Carora and Quibor Valley Aquifers: and (3) aquifers in the Lake Valencia Watershed. If current trends of aquifer overexploitation continue, further water deficits and irreversible environmental damage are predicted.  相似文献   

4.
A process-based methodology was used to compare the vulnerability of public supply wells tapping seven study areas in four hydrologically distinct regional aquifers to volatile organic compound (VOC) contamination. This method considers (1) contributing areas and travel times of groundwater flowpaths converging at individual supply wells, (2) the oxic and/or anoxic conditions encountered along each flowpath, and (3) the combined effects of hydrodynamic dispersion and contaminant- and oxic/anoxic-specific biodegradation. Contributing areas and travel times were assessed using particle tracks generated from calibrated regional groundwater flow models. These results were then used to estimate VOC concentrations relative to an unspecified initial concentration (C/C0) at individual public supply wells. The results show that the vulnerability of public supply wells to VOC contamination varies widely between different regional aquifers. Low-recharge rates, long travel times, and the predominantly oxic conditions characteristic of Basin and Range aquifers in the western United States leads to lower vulnerability to VOCs, particularly to petroleum hydrocarbons such as benzene and toluene. On the other hand, high recharge rates and short residence times characteristic of the glacial aquifers of the eastern United States leads to greater vulnerability to VOCs. These differences lead to distinct patterns of C/C0 values estimated for public supply wells characteristic of each aquifer, information that can be used by resource managers to develop monitoring plans based on relative vulnerability, to locate new public supply wells, or to make land-use management decisions.  相似文献   

5.
This paper presents an overview of changes in organic pollution of coastal waters of the Gulf of Gdańsk (Baltic Sea). Toxic pollutants including volatile organic compounds (VOC), volatile organohalogen compounds (VOX), chlorophenols, phenoxyacids, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were determined in seawater from the Gulf of Gdańsk coastal waters in the period 1996-2001. In the case of the Gulf of Gdańsk, non-conservative behaviour of VOC was observed due to random temporal and spatial of inputs along the Vistula estuary and to the dilution of VOC-enriched river water with seawater. The concentrations of VOX in seawater decreased throughout the period and the concentrations of VOX were in the range of few ng dm(-3) up to 250 ng dm(-3), similar to estuaries elsewhere. The average concentrations of chlorophenols and phenoxyacids were between 0.1 and 6.0 and 0.05 and 2.2 microg dm(-3), respectively. However, remarkably high concentrations of 2,4-dichlorophenol (6 microg dm(-3)) were obtained in samples collected from the Vistula River. Generally concentrations of PCBs did not exceed few ng dm(-3) with the exception of 1999, when all samples exhibited elevated concentrations of PCBs. In addition, higher concentrations of PCBs in the open sea compared to river waters suggested localised inputs. Due to the ability of most organic pollutants to bioaccumulate and biomagnify, especially the persistent organic pollutants, continued monitoring is of crucial importance for the health of marine life in the Gulf of Gdańsk.  相似文献   

6.
This paper presents results of a study on the concentration of adsorbable organic halogens (AOX) in water samples of the Oder River and its tributaries collected from 1998 to 2002. The Vistula River water for AOX was analysed in the period 2001–2002. The investigated waters of the Vistula near the mouth (Kiezmark) were more contaminated with AOX than the Oder near the mouth (Widuchowa, Krajnik Dolny). In general, AOX levels in the Polish rivers are comparable to the values found in the European rivers, e.g. the Rhine and the Ton. The research has shown that AOX were correlated with pH, total suspended solids, and the riverine flow. No relation between dissolved oxygen and redox potential and AOX was found out. During the flood period AOX, inorganic halogens (TIX), and mineral substances (sulfates) were analysed.  相似文献   

7.
A preliminary field evaluation of a new application of soil-gas measurement for delineation of subsurface organic contamination is described. The method measures carbon dioxide concentrations in soil gases and is based on the hypothesis that carbon dioxide concentrations from subsurface oxidation of organic compounds will be porportional to the extent of organic contamination. A correlation coefficient (r) of 0.81 (n=6) was observed between ground water dissolved organic carbon ground water concentrations and carbon dioxide concentrations in the overlying soil gases at one site. Soil-gas carbon dioxide concentrations measured ranged from 0.09 percent to 0.45 percent.  相似文献   

8.
Volatile organic compounds delected in ground water from wells at Test Area North (TAN) at the Idaho National Engineering Laboratory (INEL) prompted RCRA facility investigations in 1989 and 1990 and a CERCLA-driven RI/FS in 1992. In order to address ground water treatment feasibility, one of the main objectives, of the 1992 remedial investigation was to determine the vertical extent of ground water contamination, where the principle contaminant, of concern is trichloroethylene (TCE). It was hypothesized that a sedimentary interbed at depth in the fractured basalt aquifer could be inhibiting vertical migration of contaminants to lower aquifers. Due to the high cost of drilling and installation of ground water monitoring wells at this facility (greater than $100,000 per well), a real time method was proposed for obtaining and analyzing ground water samples during drilling to allow accurate placement of well screens in zones of predicted VOC contamination. This method utilized an inflatable pump packer pressure transducer system interfaced with a datalogger and PC at land surface. This arrangement allowed for real lime monitoring of hydraulic head above and below the packer to detect leakage around the packer during pumping and enabled collection of head data during pumping for estimating hydrologic properties. Analytical results were obtained in about an hour from an on-site mobile laboratory equipped with a gas chromalograplvmass spectrometer (GC/MS). With the hydrologic and analytical results in hand, a decision was made to either complete the well or continue drilling to the next test zone. In almost every case, analytical results of ground water samples taken from the newly installed wells closely replicated the water quality of ground water samples obtained through the pump packer system.  相似文献   

9.
Concern about the public health consequences of possible contamination of farmstead wells led to a random statewide survey in Kansas. Results of the analyses showed that 8 percent of tested wells had detectable amounts of pesticides, 2 percent had detectable amounts of volatile organic chemicals, and 37 percent had some inorganic contaminant exceeding the maximum contaminant level (MCL). Nitrate was the most common source of inorganic contamination, exceeding the MCL in 28 percent of the wells. Selenium levels exceeded the MCL in 9 percent of the wells. A multiple regression model for nitrate-N was developed. The factors included the age of the well, land use around the well, and the distance to the closest possible source of organic contamination.  相似文献   

10.
AOX‐formation by the Sonochemical Treatment of Salicylic Acid in Presence of Chloride Ultrasound shows great potential for improving water, wastewater and sludge treatment processes. However, a number of questions exist: for example the influence of suspended solids or salts. In this paper the influence of chloride in view of AOX‐formation should be investigated. As organic model compound salicylic acid (0.05…1 mmol/L) was used. Formation of AOX (adsorbable organically bound halogens) was measured in dependence upon chloride concentrations (1.4…141 mmol/L) and pH 2 and 9. Ultrasound irradiation was performed in glass reactor (500 mL) at 206 kHz and 353 kHz by continuous bubbling argon:oxgen (4:1) at a flow rate of 1 L/min into the solutions. The elimination of salicylic acid and the formation of hydrogen peroxide were not influenced by the presence of chloride (up to 56 mmol/L). The rate of salicylic acid elimination and the formation rate of hydrogen peroxide are at concentrations of mmol/(L min) levels but those of AOX formation of μmol/(L min) levels. The reactions leading to chlorinated by‐products can be seen as minor reaction paths. The yield of AOX depending on frequency, pH and chloride concentration lies between 10 μg/L and 900 μg/L. In acidic medium they were twice as high as in basic medium. Below the ratio chloride : salicylic acid of 2 mol/mol, AOX could not be identified.  相似文献   

11.
A method was developed for the determination of organic halogens in water samples with the aim of minimizing matrix effects and simplifying the sample preparation technique commonly used. The method is based on the adsorption of organic halogens in modified hydrophilic divinylbenzene polymer columns and their elution with methanol. The adsorbent used enables rapid adsorption and desorption due to comparatively high operating flow rates and minimized solvent amounts. Furthermore, no additional reconcentration steps are needed. The methanol extract obtained is combusted with a standard EOX (extractable organic halogen) analyzer and the concentration of organically bound halogens is determined by microcoulometric analysis. The matrix effects are considerably reduced compared to the standard procedure (EN 1485) commonly used. A detection limit of 13 μg/L was established.  相似文献   

12.
Arsenic in glacial aquifers: sources and geochemical controls   总被引：1，自引：0，他引：1  
A total of 176 wells in sand-and-gravel glacial aquifers in central Illinois were sampled for arsenic (As) and other chemical parameters. The results were combined with archived and published data from several hundred well samples to determine potential sources of As and the potential geochemical controls on its solubility and mobility. There was considerable spatial variability in the As concentrations. High concentrations were confined to areas smaller than 1 km in diameter. Arsenic and well depth were uncorrelated. Arsenic solubility appeared to be controlled by oxidation-reduction (redox) conditions, especially the presence of organic matter. Geochemical conditions in the aquifers are typically reducing, but only in the most reducing water does As accumulate in solution. In wells in which total organic carbon (TOC) was below 2 mg/L and sulfate (SO4(2-)) was present, As concentrations were low or below the detection limit (0.5 microg/L). Arsenic concentrations >10 microg/L were almost always found in wells where TOC was >2 mg/L and SO4(2-) was absent or at low concentrations, indicating post-SO4 (2-)reducing conditions. Iron (Fe) is common in the aquifer sediments, and Fe oxide reduction appears to be occurring throughout the aquifers. Arsenic is likely released from the solid phase as Fe oxide is reduced.  相似文献   

13.
In the upper Midwest, USA, elevated arsenic concentrations in public drinking water systems are associated with the lateral extent of northwest provenance late Wisconsin-aged drift. Twelve percent of public water systems located within the footprint of this drift (212 of 1764) exceed 10 microg/L arsenic, which is the U.S. EPA's drinking water standard. Outside of the footprint, only 2.4% of public water systems (52 of 2182) exceed 10 microg/L arsenic. Both glacial drift aquifers and shallow bedrock aquifers overlain by northwest provenance late Wisconsin-aged sediment are affected by arsenic contamination. Evidence suggests that the distinct physical characteristics of northwest provenance late Wisconsin-aged drift--its fine-grained matrix and entrained organic carbon that fosters biological activity--cause the geochemical conditions necessary to mobilize arsenic via reductive mechanisms such as reductive desorption and reductive dissolution of metal oxides. This study highlights an important and often unrecognized phenomenon: high-arsenic sediment is not necessary to cause arsenic-impacted ground water--when "impacted" is now defined as >10 microg/L. This analysis also demonstrates the scientific and economic value of using existing large but imperfect statewide data sets to observe and characterize regional-scale environmental problems.  相似文献   

14.
To assess the vulnerability of ground water to contamination in the karstic Upper Floridan aquifer (UFA), age-dating tracers and selected anthropogenic and naturally occurring compounds were analyzed in multiple water samples from a public supply well (PSW) near Tampa, Florida. Samples also were collected from 28 monitoring wells in the UFA and the overlying surficial aquifer system (SAS) and intermediate confining unit located within the contributing recharge area to the PSW. Age tracer and geochemical data from the earlier stage of the study (2003 through 2005) were combined with new data (2006) on concentrations of sulfur hexafluoride (SF6), tritium (3H), and helium-3, which were consistent with binary mixtures of water for the PSW dominated by young water (less than 7 years). Water samples from the SAS also indicated mostly young water (less than 7 years); however, most water samples from monitoring wells in the UFA had lower SF6 and 3H concentrations than the PSW and SAS, indicating mixtures containing high proportions of older water (more than 60 years). Vulnerability of the PSW to contamination was indicated by predominantly young water and elevated nitrate-N and volatile organic compound concentrations that were similar to those in the SAS. Elevated arsenic (As) concentrations (3 to 19 μg/L) and higher As(V)/As(III) ratios in the PSW than in water from UFA monitoring wells indicate that oxic water from the SAS likely mobilizes As from pyrite in the UFA matrix. Young water found in the PSW also was present in UFA monitoring wells that tap a highly transmissive zone (43- to 53-m depth) in the UFA.  相似文献   

15.
A study designed to evaluate ground water quality changes resulting from spreading oil-field brine on roads for ice and dust control was conducted using a gravel roadbed that received weekly applications of brine eight times during the winter phase and 11 times during the summer phase of the study. A network of 11 monitoring wells and five pressure-vacuum lysimeters was installed to obtain ground water and soil water samples. Thirteen sets of water- quality samples were collected and analyzed for major ions, trace metals, and volatile organic compounds. Two sets of samples were taken prior to brine spreading, four sets during winter-phase spreading, five sets during summer- phase spreading, and two sets during the interim between the winter and summer phases. A brine plume delineated by elevated specific-conductance values and elevated chloride concentrations developed downgradient of the roadbed during both the winter and summer phases. The brine plume caused chloride concentrations in ground water samples to exceed U.S. EPA public drinking-water standards by two-fold during the winter phase and five-fold during the summer phase. No other major ions, trace metals, or volatile organic compounds exceeded the standards during the winter or summer phases. More than 99 percent dilution of the solutes in the brine occurred between the roadbed surface and the local ground water flow system. Further attenuation of calcium, sodium, potassium, and strontium resulted from adsorption, whereas further attenuation of benzene resulted from volatilization and adsorption.  相似文献   

16.
Water samples collected from 26 sites at an abandoned oil refinery in south-central Kansas were analyzed for total organic carbon (TOC) and specific volatile and semivolatile organic compounds by gas-chromatography/mass-spectrometric methods. Results from a Spearman-rho correlation analysis between TOC concentration and the number of compounds (correlation coefficient = 0.71) and TOC concentration and total concentration of compounds identified (correlation coefficient = 0.83) indicate correlations significant at the 0.01 level.
Although TOC data alone would not be sufficient to evaluate hazards posed by oil-refinery wastes, results of the correlation analysis performed using data collected from the site in Kansas indicate that TOC data can be used effectively to delineate petroleum-related ground water contamination and to help identify sources of ground water contaminants. TOC data collected from a large number of temporary sampling points during the initial phases of an investigation will provide an estimate of the extent of hydrocarbon contamination and allow placement of monitoring wells and more detailed sampling in appropriate areas.  相似文献   

17.
Ground water quality data generated during the investigation of 334 hazardous waste disposal sites were used to contrast the Resource Conservation and Recovery Act (RCRA) and Comprehensive Emergency Response, Compensation and Liability Act (CERCLA) monitoring. programs. The minimum RCRA-required network of four wells was equaled or exceeded at 94 percent of the 156 RCRA sites and 70 percent of the 178 CERCLA sites in the data base. A sampling frequency of four events per year or more was used at 60 percent of the RCRA sites compared to only 24 percent at the CERCLA sites. CERCLA records compiled to date indicate that 480 compounds have been detected and another 220 compounds have been tentatively identified in ground water in the vicinity of hazardous waste disposal sites. However, the composite data from 123 RCRA site monitoring programs only indicates the presence of 100 chemical substances. The most significant discrepancy in the RCRA detection monitoring program is that it only generates data on three of the 20 organic contaminants that have been most frequently detected during the CERCLA hazardous waste disposal site investigations. Modification of the current RCRA program to include routine analysis for volatile organic compounds would correct this weakness.  相似文献   

18.
Benzene, toluene and xylenes (BTX) were detected in ground water during a contaminant hydrogeological investigation of a landfill site. The landfill site was situated on approximately 10m (33 ft) of clay and glacial till overburden soils, which were underlain by a shaly limestone bedrock. The top part of the bedrock was the regional aquifer in the study area. Initial thoughts were that the landfill was the source of the BTX. However, the BTX was detected in ground water a considerable distance from the known extent of the leachate plume. Subsequent detailed analysis of rock cores showed the BTX could be leached from bituminous layers of shale that were interbedded in limestone. Rock core testing included gas chromatograph (GC) analysis of organic free reagent water used for leaching tests, flame ionization detection on a solvent used for leaching tests and thermal desorption analysis of the solid rock. The naturally occurring BTX, along with the presence of brackish ground water in the shaly bedrock, made it difficult to identify ground water contamination emanating from the landfill. Thus, the presence of BTX should not be considered definitive evidence of ground water contamination in certain sedimentary rock aquifers.  相似文献   

19.
AGalerkin finite-element model coupled with a particle tracking routine was developed to analyze the flow and transport dynamics near a high-capacity irrigation well. The model was used to compute the head distribution around the pumping well, to determine the area of influence, and to define ground water flowlines during short-term pumping periods typical of those used to collect water quality samples from high-capacity wells. In addition to hypothetical example results, the model was used to qualitatively analyze data obtained from pump-and-sample experiments conducted in an unconfined alluvial aquifer within the Platte River valley of south-central Nebraska where nitrate-nitrogen (NO3-N) contamination is prevalent.
Simulation results of both the hypothetical and field cases suggest that short-term pumping events, impact a limited volume of aquifer. The area of influence and flowlines are affected by aquifer anisotropy, pumping rate, and well construction characteristics). Ground water above or below the screened intervals does not enter a partially penetrating well in anisotropic aquifers. In aquifers where NO3-N concentration varies vertically and horizontally, waler quality samples from an irrigation, or other high-capacity, well provide only limited information about ground water contamination. A numerical model is thus recommended for calculating the area of influence and determining flowlines around high-capacity wells so that information derived from water quality samples collected at the wellhead can be better interpreted.  相似文献   

20.
Gas Works Park, in Seattle, Washington, is located on the site of a coal and oil gasification plant that ceased operation in 1956. During operation, many types of wastes, including coal, tar, and oil, accumulated on-site. The park soil is currently (1986) contaminated with compounds such as polynuclear aromatic hydrocarbons, volatile organic compounds, trace metals, and cyanide. Analyses of water samples from a network of observation wells in the park indicate that these compounds are also present in the ground water.
Polynuclear aromatic hydrocarbons and volatile organic compounds were identified in ground water samples in concentrations as large as 200 mg/L. Concentrations of organic compounds were largest where ground water was in contact with a non-aqueous phase liquid in the soil. Where no non-aqueous phase liquid was present, concentrations were much smaller, even if the ground water was in contact with contaminated soils. This condition is attributed to weathering processes in which soluble, low-molecular-weight organic compounds are preferentially dissolved from the non-aqueous phase liquid into the ground water. Where no non-aqueous phase liquid is present, only stained soils containing relatively insoluble, high-molecular-weight compounds remain. Concentrations of organic contaminants in the soils may still remain large.  相似文献   

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