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1.
Douglas M. Mackay Murray D. Einarson Phil M. Kaiser Mamie Nozawa‐Inoue Sham Goyal Irina Chakraborty Ehsan Rasa Kate M. Scow 《Ground water》2012,50(6):895-907
A tracer plume was created within a thin aquifer by injection for 299 d of two adjacent “sub‐plumes” to represent one type of plume heterogeneity encountered in practice. The plume was monitored by snapshot sampling of transects of fully screened wells. The mass injection rate and total mass injected were known. Using all wells in each transect (0.77 m well spacing, 1.4 points/m2 sampling density), the Theissen Polygon Method (TPM) yielded apparently accurate mass discharge (Md) estimates at three transects for 12 snapshots. When applied to hypothetical sparser transects using subsets of the wells with average spacing and sampling density from 1.55 to 5.39 m and 0.70 to 0.20 points/m2, respectively, the TPM accuracy depended on well spacing and location of the wells in the hypothesized transect with respect to the sub‐plumes. Potential error was relatively low when the well spacing was less than the widths of the sub‐plumes (>0.35 points/m2). Potential error increased for well spacing similar to or greater than the sub‐plume widths, or when less than 1% of the plume area was sampled. For low density sampling of laterally heterogeneous plumes, small changes in groundwater flow direction can lead to wide fluctuations in Md estimates by the TPM. However, sampling conducted when flow is known or likely to be in a preferred direction can potentially allow more useful comparisons of Md over multiyear time frames, such as required for performance evaluation of natural attenuation or engineered remediation systems. 相似文献
2.
动态地幔柱模式被广泛用于讨论地球科学中的一些重要课题,如巨大火成区的成因,冈瓦纳古陆解体的原因,板块内中小尺度动力过程的驱动因素等．但是这个基于实验研究而建立的模式中,忽略了地幔柱尾管特征及其作用．地幔柱尾管内温度和速度分布是研究地幔柱上升过程的必要条件．本文从控制尾管结构的基本方程出发,给出了一个定常轴对称地幔柱温度和速度分布的近似分析解．从而得到尾管结构的基本特征：影响尾管内温度分布的主导因素是地幔柱的热流通量,而尾管内上涌速度的大小则不仅取决于热流通量,主要是取决于地幔粘度随深度的变化方式．结果表明,对弱地幔柱,尾管的热损失可能是不可忽略的,而对强地幔柱,径向质量传递可能是不可忽略的. 相似文献
3.
Barbara A. Bekins Isabelle M. Cozzarelli Melinda L. Erickson Ross A. Steenson Kevin A. Thorn 《Ground water》2016,54(5):681-691
Two groundwater plumes in north central Minnesota with residual crude oil sources have 20 to 50 mg/L of nonvolatile dissolved organic carbon (NVDOC). These values are over 10 times higher than benzene and two to three times higher than Diesel Range Organics in the same wells. On the basis of previous work, most of the NVDOC consists of partial transformation products from the crude oil. Monitoring data from 1988 to 2015 at one of the sites located near Bemidji, MN show that the plume of metabolites is expanding toward a lakeshore located 335 m from the source zone. Other mass balance studies of the site have demonstrated that the plume expansion is driven by the combined effect of continued presence of the residual crude oil source and depletion of the electron accepting capacity of solid phase iron oxide and hydroxides on the aquifer sediments. These plumes of metabolites are not covered by regulatory monitoring and reporting requirements in Minnesota and other states. Yet, a review of toxicology studies indicates that polar metabolites of crude oil may pose a risk to aquatic and mammalian species. Together the results suggest that at sites where residual sources are present, monitoring of NVDOC may be warranted to evaluate the fates of plumes of hydrocarbon transformation products. 相似文献
4.
Nicola Balbarini Majken Frederiksen Vinni Rønde Ingelise Møller Anne T. Sonne Ursula S. McKnight Jørn K. Pedersen Philip J. Binning Poul L. Bjerg 《Ground water》2020,58(2):208-223
A groundwater plume containing high concentrations of pharmaceutical compounds, mainly sulfonamides, barbiturates, and ethyl urethane, in addition to chlorinated ethenes and benzene was investigated. The contamination originating from a former pharmaceutical industry discharges into a multilayered aquifer system and a downgradient stream. In this study, geological and hydrogeological data were integrated into a numerical flow model to examine identified trends using statistical approaches, including principal component analysis and hierarchal cluster analysis. A joint interpretation of the groundwater flow paths and contaminant concentrations in the different compartments (i.e., groundwater and hyporheic zone) provided insight on the transport processes of the different contaminant plumes to the stream. The analysis of historical groundwater concentrations of pharmaceutical compounds at the site suggested these compounds are slowly degrading. The pharmaceutical compounds migrate in both a deep semiconfined aquifer, as well as in the shallow unconfined aquifer, and enter the stream along a 2-km stretch. This contrasted with the chlorinated ethenes, which mainly discharge to the stream as a focused plume from the unconfined aquifer. The integrated approach developed here, combining groundwater flow modeling and statistical analyses of the contaminant concentration data collected in groundwater and the hyporheic zone, lead to an improved understanding of the observed distribution of contaminants in the unconfined and semiconfined aquifers, and thus to their discharge to the stream. This approach is particularly relevant for large and long-lasting contaminant sources and plumes, such as abandoned landfills and industrial production sites, where field investigations may be very expensive. 相似文献
5.
Don A. Vroblesky Matthew D. Petkewich Mark A. Lowery James E. Landmeyer 《Ground Water Monitoring & Remediation》2011,31(4):63-69
Groundwater contamination by tetrachloroethene and its dechlorination products is present in two partially intermingled plumes in the surficial aquifer near a former dry‐cleaning facility at Site 45, Marine Corps Recruit Depot, Parris Island, South Carolina. The northern plume originates from the vicinity of former above‐ground storage tanks. Free‐phase tetrachloroethene from activities in this area entered the groundwater. The southern plume originates at a nearby, new dry‐cleaning facility, but probably was the result of contamination released to the aquifer from a leaking sanitary sewer line from the former dry‐cleaning facility. Discharge of dissolved groundwater contamination is primarily to leaking storm sewers below the water table. The strong influence of sanitary sewers on source distribution and of storm sewers on plume orientation and discharge at this site indicates that groundwater‐contamination investigators should consider the potential influence of sewer systems at their sites. 相似文献
6.
J.A. Warrick P.M. DiGiacomo S.B. Weisberg N.P. Nezlin M. Mengel B.H. Jones J.C. Ohlmann L. Washburn E.J. Terrill K.L. Farnsworth 《Continental Shelf Research》2007
Stormwater river plumes are important vectors of marine contaminants and pathogens in the Southern California Bight. Here we report the results of a multi-institution investigation of the river plumes across eight major river systems of southern California. We use in situ water samples from multi-day cruises in combination with MODIS satellite remote sensing, buoy meteorological observations, drifters, and HF radar current measurements to evaluate the dispersal patterns and dynamics of the freshwater plumes. River discharge was exceptionally episodic, and the majority of storm discharge occurred in a few hours. The combined plume observing techniques revealed that plumes commonly detach from the coast and turn to the left, which is the opposite direction of Coriolis influence. Although initial offshore velocity of the buoyant plumes was ∼50 cm/s and was influenced by river discharge inertia (i.e., the direct momentum of the river flux) and buoyancy, subsequent advection of the plumes was largely observed in an alongshore direction and dominated by local winds. Due to the multiple day upwelling wind conditions that commonly follow discharge events, plumes were observed to flow from their respective river mouths to down-coast waters at rates of 20–40 km/d. Lastly, we note that suspended-sediment concentration and beam-attenuation were poorly correlated with plume salinity across and within the sampled plumes (mean r2=0.12 and 0.25, respectively), while colored dissolved organic matter (CDOM) fluorescence was well correlated (mean r2=0.56), suggesting that CDOM may serve as a good tracer of the discharged freshwater in subsequent remote sensing and monitoring efforts of plumes. 相似文献
7.
Field data at six former manufactured gas plant sites in New Jersey were used to estimate the biodegradation rate constants for the anaerobic processes naturally occurring within the ground water contaminant plumes (primarily iron and sulfate reduction). Those rate constants turned out to be about an order of magnitude smaller than values reported for the same contaminants (primarily benzene and naphthalene) at fuel sites. At four of the sites, there appeared to be sufficient electron acceptor present to eventually degrade the contaminants in the plume. However, the presence of nonaqueous phase liquids tends to offset that capacity by continuing to act as a source of contaminants that can dissolve in the ground water. 相似文献
8.
Terrestrial discharge into the Great Barrier Reef Lagoon: nutrient behavior in coastal waters 总被引：1，自引：0，他引：1
Pollution of coastal regions of the Great Barrier Reef World Heritage Area (GBRWHA) is dominated by river discharge associated with agricultural development of the adjacent catchments. Runoff of sediment, nutrients and pesticides has sharply increased since European settlement. Since 1991 plumes from river discharge entering the GBRWHA have been mapped by aerial mapping of plume edges and concentrations of contaminants in plumes measured. Plume dispersion is governed primarily by wind speed and direction. Most plumes spread in a band up to 50 km from the coast. Particulate material discharged in the plumes is trapped within 10 km of the coast. Dissolved nutrients disperse much further and elevated nutrient concentrations are measurable at distances of hundreds of kilometres from river mouths. This differential transport of particulate versus dissolved nutrients is important for the potential effects of these materials and management of their generation on the Great Barrier Reef catchment. 相似文献
9.
10.
We developed, and applied in two sites, novel methods to measure ground water-borne nitrogen loads to receiving estuaries from plumes resulting from land disposal of waste water treatment plant (WWTP) effluent. In addition, we quantified nitrogen losses from WWTP effluent during transport through watersheds. WWTP load to receiving water was estimated as the difference between total measured ground water-transported nitrogen load and modeled load from major nitrogen sources other than the WWTP. To test estimated WWTP loads, we applied two additional methods. First, we quantified total annual waste water nitrogen load from watersheds based on nitrogen stable isotopic signatures of primary producers in receiving water. Second, we used published data on ground water nitrogen concentrations in an array of wells to estimate dimensions of the plume and quantify the annual mass of nitrogen transported within the plume. Loss of nitrogen during transport through the watershed was estimated as the difference between the annual mass of nitrogen applied to watersheds as treatment plant effluent and the estimated nitrogen load reaching receiving water. In one plume, we corroborated our estimated nitrogen loss in watersheds using data from multiple-level sampling wells to calculate the loss of nitrogen relative to a conservative tracer. The results suggest that nitrogen from the plumes is discharging to the estuaries but that substantial nitrogen loss occurs during transport through the watersheds. The measured vs. modeled and stable isotopic approaches, in comparison to the plume mapping approach, may more reliably quantify ground water-transported WWTP loads to estuaries. 相似文献
11.
Review of Quantitative Surveys of the Length and Stability of MTBE,TBA, and Benzene Plumes in Groundwater at UST Sites 
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下载免费PDF全文 Quantitative information regarding the length and stability condition of groundwater plumes of benzene, methyl tert‐butyl ether (MTBE), and tert‐butyl alcohol (TBA) has been compiled from thousands of underground storage tank (UST) sites in the United States where gasoline fuel releases have occurred. This paper presents a review and summary of 13 published scientific surveys, of which 10 address benzene and/or MTBE plumes only, and 3 address benzene, MTBE, and TBA plumes. These data show the observed lengths of benzene and MTBE plumes to be relatively consistent among various regions and hydrogeologic settings, with median lengths at a delineation limit of 10 µg/L falling into relatively narrow ranges from 101 to 185 feet for benzene and 110 to 178 feet for MTBE. The observed statistical distributions of MTBE and benzene plumes show the two plume types to be of comparable lengths, with 90th percentile MTBE plume lengths moderately exceeding benzene plume lengths by 16% at a 10‐µg/L delineation limit (400 feet vs. 345 feet) and 25% at a 5‐µg/L delineation limit (530 feet vs. 425 feet). Stability analyses for benzene and MTBE plumes found 94 and 93% of these plumes, respectively, to be in a nonexpanding condition, and over 91% of individual monitoring wells to exhibit nonincreasing concentration trends. Three published studies addressing TBA found TBA plumes to be of comparable length to MTBE and benzene plumes, with 86% of wells in one study showing nonincreasing concentration trends. 相似文献
12.
Measurements of perturbations in the atmospheric potential gradient around volcanic plumes at multiple (from two to five) sites, and measurements of the charge-mass ratio of ash particles falling from volcanic plumes, were carried out at Sakurajima Volcano, Japan. Results from 28 and 29 October 1995, show that the nature of the perturbations depends on the intensity of plume activity. Although plume activity was vigorous on 28 October, negative perturbations were predominant. As plume activity peaked, the magnitude of negative perturbations decreased just below the plume and increased at an off-axis site. During the peak period, positively charged ash particles fell out from the plume. This suggests that the active plume dominantly contained negatively charged materials, and that positively and negatively charged materials were added to the lower and upper parts of the plume, respectively, during the peak period. On the other hand, as plume activity became less vigorous on 29 October, the perturbations were characterized by a positive anomaly followed by a negative anomaly. Because wind velocity increased with altitude that day, we infer that positive and negative charges were distributed in the upper and lower parts of the plume, respectively. The differences in perturbations observed on 28 and 29 October suggest that volcanic plumes are generally composed of three parts: an upper part with positively charged gas and aerosol, a middle part with negatively charged fine ash particles, and a lower part with positively charged coarse ash particles. The compilation of present and previous results from Sakurajima and other volcanoes indicates that the effect of the negative charge in the middle part was predominant in most cases, although positive perturbations caused by the upper part were observed around some weak plumes. The effect of positively charged particles in the lower part was observable only when plume activity was sufficiently strong because positively charged coarse particles tended to fall out near the vent. 相似文献
13.
Consumption of aquifer Fe(III) during biodegradation of ground water contaminants may result in expansion of a contaminant plume, changing the outlook for monitored natural attenuation. Data from two research sites contaminated with petroleum hydrocarbons show that toluene and xylenes degrade under methanogenic conditions, but the benzene and ethylbenzene plumes grow as aquifer Fe(III) supplies are depleted. By considering a one-dimensional reaction front in a constant unidirectional flow field, it is possible to derive a simple expression for the growth rate of a benzene plume. The method balances the mass flux of benzene with the Fe(III) content of the aquifer, assuming that the biodegradation reaction is instantaneous. The resulting expression shows that the benzene front migration is retarded relative to the ground water velocity by a factor that depends on the concentrations of hydrocarbon and bioavailable Fe(III). The method provides good agreement with benzene plumes at a crude oil study site in Minnesota and a gasoline site in South Carolina. Compared to the South Carolina site, the Minnesota site has 25% higher benzene flux but eight times the Fe(III), leading to about one-sixth the expansion rate. Although it was developed for benzene, toluene, ethylbenzene, and xylenes, the growth-rate estimation method may have applications to contaminant plumes from other persistent contaminant sources. 相似文献
14.
Gorm Heron John Bierschenk Robin Swift Robert Watson Michael Kominek 《Ground Water Monitoring & Remediation》2016,36(1):26-37
The tetrachloroethene (PCE) source zone at a site in Endicott, New York had caused a dissolved PCE plume. This plume was commingled with a petroleum hydrocarbon plume from an upgradient source of fuel oil. The plume required a system for hydraulic containment, using extraction wells located about 360 m downgradient of the source. The source area was remediated using in situ thermal desorption (ISTD). Approximately 1406 kilograms (kg) of PCE was removed in addition to 4082 kg of commingled petroleum‐related compounds. The ISTD treatment reduced the PCE mass discharge into the plume from an estimated 57 kg/year to 0.07 kg/year, essentially removing the source term. In the 5 years following the completion of the thermal treatment in early 2010, the PCE plume has collapsed, and the concentration of degradation products in the PCE‐series plume area has declined by two to three orders of magnitude. Anaerobic dechlorination is the suspected dominant mechanism, assisted by the presence of a fuel oil smear zone and a petroleum hydrocarbon plume from a separate source area upgradient of the PCE source. Based on the post‐thermal treatment groundwater monitoring data, the hydraulic containment system was reduced in 2014 and discontinued in early 2015. 相似文献
15.
Assuming that Rayleigh-Benard flow occurs within the upper mantle, ascending plumes must undergo horizontal displacement during ascent that can be traced at the surface. It is shown that the Hawaiian-Emperor bend cannot be formed if the convection rate is of the same order of magnitude as the ascent rate of the plumes. The plume patterns obtained by push-pull or lithospheric sliding are similar to that of the Hawaiian-Emperor chain. Hence the present results support the sliding model. 相似文献
16.
A comprehensive numerical study was undertaken to investigate transport of a variable-density, conservative solute plume in an unconfined coastal aquifer subject to high and low frequency oceanic forcing. The model combined variable-density saturated flow for groundwater and solute transport, and wave hydrodynamics from a 2D Navier–Stokes solver. A sinusoidal tidal signal was specified by implementing time-varying heads at the seaward boundary. The solute plume behavior was investigated under different oceanic forcing conditions: no forcing, waves, tide, and combined waves and tide. For each forcing condition, four different injected solute densities (freshwater, brackish water, seawater, brine) were used to investigate the effects of density on the transport of the injected plume beneath and across the beach face. The plume’s low-order spatial moments were computed, viz., mass, centroid, variance and aspect ratio. The results confirmed that both tide- and wave-forcing produce an upper saline plume beneath the beach face in addition to the classical saltwater wedge. For the no-forcing and tide-only cases (during rising tides), an additional small circulation cell below the beach face was observed. Oceanic forcing affects strongly the solute plume’s flow path, residence time and discharge rate across the beach face, as well as its spreading. For the same oceanic forcing, solute plumes with different densities follow different trajectories from the source to the discharge location (beach face). The residence time and plume spreading increased with plume density. It was concluded that simulations that neglect the effect of waves or tides cannot reproduce accurately solute plume dispersion and also, in the case of coasts with small waves or tides, the solute residence time in the aquifer. 相似文献
17.
Reinhard K. Frohlich Patrick J. Barosh Thomas Boving 《Journal of Applied Geophysics》2008,64(1-2):25-36
The Picillo Farm, EPA Superfund Site, in western Rhode Island was an unauthorized disposal site of hazardous organic chemicals. Predominantly organic contaminants have entered an aquifer comprised of layered glacial deposits and fractured bedrock and spread past the site boundaries with groundwater flow. Hydraulic conductivities in the glacial deposits range over two orders of magnitude and fractures and faults in the granitic bedrock further complicate the spreading of contaminants. Monitoring wells delineate two plumes that extend towards a fault-controlled valley with lakes and wetlands; one to the northwest and the other to the southwest. In this investigation we studied the electrical characteristics of both plumes.One dimensional Schlumberger depth soundings were conducted along several profile lines over the plumes and compared to those over non-contaminated sections of the site. With regard to the southwestern plume, high formation factors (ratio of bulk layer to pore water resistivity) between 12 and 45 were observed compared to values between 2.5 and 7.7 measured over the non-contaminated sections. Also, high values (> 5) of vertical electrical anisotropy (ratio of geoelectrically determined depth to high resistivity bedrock to drilled depth to bedrock) were measured over the contaminated part of the site. These values are extremely high compared to other non-contaminated sites (range: 2 to 3) in glacial stream channels of southern Rhode Island. Geoelectric measurements were affected by lateral effects. However, the consistency of high formation factors (11 to 35) and high vertical anisotropies (3 to 5) over the southwestern plume in comparison to low formation factors (3 to 8) and vertical anisotropies (1 to 1.5) over non-contaminated sites represents a marked difference between both sites. Overall, the Schlumberger depth soundings are less susceptible to near-surface lateral inhomogeneities than expected from other geoelectrical methods. Also, the disadvantage of a 1D interpretation was compensated by estimating resistivity and thickness ranges within the concept of non-uniqueness using the Dar Zarrouk parameters (Maillet, R., 1947. The fundamental equations of electrical prospecting. Geophysics, 12(4): 529–556.).The results over the northwestern plume, i.e. an area with higher contaminant concentration than the southwestern plume, were mixed and showed no consistent trends. Predominantly reducing conditions, as indicated by the presence of soluble ferric (FeII) iron hydroxides in ground water samples, increased the electrical conductivity. This is believed to have compensated the effect of high formation factors on the bulk saturated layer resistivity within the affected area. 相似文献
18.
At three industrial sites in Ontario, New Hampshire, and Florida, tetrachloroethylene (PCE) and trichloroethylene (TCE), released decades ago as dense nonaqueous phase liquids (DNAPLs), now form persistent source zones for dissolved contaminant plumes. These zones are suspended below the water table and above the bottoms of their respective, moderately homogeneous, unconfined sandy aquifers. Exceptionally detailed, depth-discrete, ground water sampling was performed using a direct-push sampler along cross sections of the dissolved-phase plumes, immediately downgradient of these DNAPL source zones. The total plume PCE or TCE mass-discharge through each cross section ranged between 15 and 31 kg/year. Vertical ground water sample spacing as small as 15 cm and lateral spacing typically between 1 and 3 m revealed small zones where maximum concentrations were between 1% and 61% of solubility. These local maxima are surrounded by much lower concentration zones. A spacing no larger than 15 to 30 cm was needed at some locations to identify high concentration zones, and aqueous VOC concentrations varied as much as four orders of magnitude across 30 cm vertical intervals. High-resolution sampling at these sites showed that three-quarters of the mass-discharge occurs within 5% to 10% of the plume cross sectional areas. The extreme spatial variability of the mass-discharge occurs even though the sand aquifers are nearly hydraulically homogeneous. Depth-discrete field techniques such as those used in this study are essential for finding the small zones producing most of the mass-discharge, which is important for assessing natural attenuation and designing remedial options. 相似文献
19.
A Comparison of Benzene and Toluene Plume Lengths for Sites Contaminated with Regular vs. Ethanol-Amended Gasoline 总被引：3，自引：0，他引：3
G.M.L Ruiz-Aguilar K. O'Reilly P.J.J. Alvarez 《Ground Water Monitoring & Remediation》2003,23(1):48-53
This article describes various statistical analyses of plume-length data to evaluate the hypothesis that the presence of ethanol in gasoline may hinder the natural attenuation of hydrocarbon releases. Plume dimensions were determined for gasoline-contaminated sites to evaluate the effect of ethanol on benzene and toluene plume lengths. Data from 217 sites in Iowa (without ethanol; set 1) were compared to data from 29 sites in Kansas that were contaminated by ethanol-amended gasoline (10% ethanol by volume; set 2). The data were log-normally distributed, with mean benzene plume lengths (± standard deviation) of 193 ± 135 feet for set 1 and 263 ± 103 feet for set 2 (36% longer). The median lengths were 156 feet and 263 feet (69% longer), respectively. Mean toluene plume lengths were 185± 131 feet for set 1 and 211 ±99 feet for set 2 (14% longer), and the median lengths were 158 feet and 219 feet (39% longer), respectively. Thus, ethanol-containing BTEX plumes were significantly longer for benzene (p < 0.05), but not for toluene. A Wilcoxon signed rank test showed that toluene plumes were generally shorter than benzene plumes, which suggests that toluene was attenuated to a greater extent than benzene. This trend was more pronounced for set 2 (with ethanol), which may reflect that benzene attenuation is more sensitive to the depletion of electron acceptors caused by ethanol degradation. These results support the hypothesis that the presence of ethanol in gasoline can lead to longer benzene plumes. The importance of this effect, however, is probably site-specific, largely depending on the release scenario and the available electron acceptor pool. 相似文献
20.
Falta RW 《Ground water》2008,46(2):272-285
It is often difficult at contaminated sites to decide whether remediation effort should be focused on the contaminant source, the dissolved plume, or on both zones. The decision process at these sites is hampered by a lack of quantitative tools for comparing remediation alternatives. A new screening-level mass balance approach is developed for simulating the transient effects of simultaneous ground water source and plume remediation. The contaminant source model is based on a power function relationship between source mass and source discharge, and it can consider partial source remediation at any time after the initial release. The source model serves as a time-dependent mass flux boundary condition to a new analytical plume model, where flow is assumed to be one dimensional, with three-dimensional dispersion. The plume model simulates first-order sequential decay and production of several species, and the decay rates and parent/daughter yield coefficients are variable functions of time and distance. This new method allows for flexible simulation of natural attenuation or remediation efforts that enhance plume degradation. The plume remediation effort may be temporary or delayed in time, limited in space, and it may have different chemical effects on different contaminant species in the decay chain. 相似文献