Humic acid enhanced remediation of an emplaced diesel source in groundwater. 1. Laboratory-based pilot scale test

The enhanced solubility of petroleum-derived compounds in humic acid solutions is the basis for a new groundwater remediation technology. In this unique pilot-scale test, a stationary contaminant source consisting of diesel fuel was placed below the water table in a model sand aquifer (1.2 x 5.5 x 1.8-m deep) and flushed with water at a flow rate of 2 cm/h over 5 years. At 51 days, laboratory grade humic acid was added to the water and maintained at a level of approximately 0.8 g/l. The addition of humic acid had only a small impact on the aqueous transport of the BTEX components, which were rapidly dissolved from the diesel, but had a large effect on the flushing of PAHs, including methylated naphthalenes (MNs). Binding to aqueous humic acid enhanced the solubilization of MNs two- to tenfold. During aqueous transport, biodegradation of the BTEX and PAHs occurred, limiting the lateral and longitudinal extent of the diesel contaminant plume in the model aquifer. It appears that through enhanced solubilization, the overall biodegradation rate of the MNs was increased. As the various MNs were depleted from the diesel source, the MN plume shrank and then disappeared.     

复合功能吸附树脂对双组分萘系化合物的竞争吸附研究

1-氨基 -2 -萘酚 -4 -磺酸 ( 1,2 ,4-酸 )和 2 -萘酚自不同双组分吸附体系中吸附至复合功能吸附树脂 AL -1上的吸附等温线符合 F reundlich等温模型。1,2 ,4-酸的吸附为吸热过程 ,而 2 -萘酚的吸附为放热过程。固相上的 2 -萘酚几乎不影响 1,2 ,4-酸的吸附 ,而固相上的 1,2 ,4-酸大大削弱了 2 -萘酚的吸附。两种溶质在吸附位点上的竞争为主要作用机制。     

New methodology to investigate potential contaminant mass fluxes at the stream-aquifer interface by combining integral pumping tests and streambed temperatures

The spatial pattern and magnitude of mass fluxes at the stream-aquifer interface have important implications for the fate and transport of contaminants in river basins. Integral pumping tests were performed to quantify average concentrations of chlorinated benzenes in an unconfined aquifer partially penetrated by a stream. Four pumping wells were operated simultaneously for a time period of 5 days and sampled for contaminant concentrations. Streambed temperatures were mapped at multiple depths along a 60m long stream reach to identify the spatial patterns of groundwater discharge and to quantify water fluxes at the stream-aquifer interface. The combined interpretation of the results showed average potential contaminant mass fluxes from the aquifer to the stream of 272microgm(-2)d(-1) MCB and 71microgm(-2)d(-1) DCB, respectively. This methodology combines a large-scale assessment of aquifer contamination with a high-resolution survey of groundwater discharge zones to estimate contaminant mass fluxes between aquifer and stream.     

Fungal hydroxylation of polychlorinated naphthalenes with chlorine migration by wood rotting fungi

Biodegradation of the polychlorinated naphthalenes (PCNs) 1,4-dichloronaphthalene (1,4-DCN), 2,7-dichloronaphthalene (2,7-DCN), and 1,2,3,4-tetrachloronaphthalene (1,2,3,4-TCN), by the white-rot fungus Phlebia lindtneri was investigated. 1,4-DCN was metabolized to form six metabolites by the fungus. It was estimated from GC–MS fragment patterns that the metabolites were four putative hydroxylated and two dihydrodihydroxylated compounds. One of the hydroxylated products was identified as 2,4-dichloro-1-naphthol by GC–MS analysis using an authentic standard. This intermediate indicated chlorine migration in a biological system of P. lindtneri. 2,7-DCN was metabolized to five hydroxylated metabolites and a dihydrodihydroxylated metabolite. Significant inhibition of the degradation of DCNs and formation of their metabolic products was observed in incubation with the cytochrome P-450 monooxygenase inhibitor piperonyl butoxide. The formation of the dihydrodiol-like metabolites, chlorine migration and the experiment with P-450 inhibitor suggested that P. lindtneri provides hydroxyl metabolites via benzene oxide intermediates of DCNs by a cytochrome P450 monooxygenase. In addition, P. lindtneri degraded 1,2,3,4-TCN; two hydroxylated compounds and a dihydrodihydroxylated compound were formed.     

Polychlorinated naphthalenes in sediments from the industrial region of Bitterfeld

Bitterfeld (Germany) was a major site of chemical production in the former German Democratic Republic with chloralkali electrolysis as the basic process. Effluents were dumped via the creek Spittelwasser into the rivers Mulde and Elbe. Despite the fact that the chloralkali industry is known as a possible source of polychlorinated naphthalenes (PCNs), to date no data about PCN pollution in the region of Bitterfeld and downstream regions are available. Therefore, sediments of the creek Spittelwasser were isomer-specifically analysed for penta-, hexa- and heptachlorinated naphthalenes using GC/MS. Concentrations of 880, 543 and 1120 ng/g dry weight were found, respectively. The isomer pattern suggests chloralkali industry as the major source of PCN contamination. Because of their toxicological relevance we suggest to include PCNs into monitoring and risk assessment programs of the rivers Mulde and Elbe downstream of Bitterfeld.     

In situ modification of an aquifer material by a cationic surfactant to enhance retardation of organic contaminants

Sorption of hexadecyltrimethylammonium chloride (HDTMA), a cationic surfactant, on aquifer material from Columbus AFB, Mississippi, U.S.A., was examined. Transport studies using flow-through columns and a box model aquifer showed that an almost stationary zone of HDTMA-modified aquifer material could be produced in situ without a significant decrease in hydraulic conductivity.Perchloroethylene (PCE) and naphthalene sorption isotherms on the HDTMA-modified aquifer material were linear, and sorption coefficients were increased by over two orders of magnitude relative to the unmodified material. The retardation of PCE by insitu emplaced HDTMA zones within a column was examined. Agreement between batch- and column-derived sorption coefficients and breakthrough curve symmetry indicates that local equilibrium was attained. Significant retardation of a naphthalene plume by an in situ emplaced surfactant zone was demonstrated in the box model aquifer system.The experimental results indicate that it is feasible to create in situ a sorbent zone within an aquifer using cationic surfactants. In most situations, the sorbent zone concept needs to be coupled with contaminant degradation processes for sorbent emplacement to be a practical tool in the remediation of groundwater contamination sites. Sorbent zones may be of benefit in the engineering of suitable environments for microbial or abiotic degradation reactions and by providing time slow reactions to occur.     

Sulfate contamination in groundwater from a carbonate-hosted mine

Sulfide oxidation in a carbonate environment produces groundwater contamination with high sulfate making the water unsuitable for drinking supplies. The zinc-lead mines near Shullsburg, Wisconsin are located in the Galena-Platteville Formation, a carbonate aquifer that was dewatered during mining. Sulfate levels have reached as high as 40 nmol/l in some local wells and eleven wells were abandoned.Geochemical modeling of chemical reactions and isotope effects using the USGS computer program PHREEQE showed the importance of dolomite, calcite, CO₂, and siderite or iron hydroxide in controlling the water chemistry. The decrease in sulfate levels with time indicated that dilution by incoming recharge water was an ongoing process. The results of carbon isotope reaction modeling are consistent with dilution of contaminated water. The evidence for localization of contamination and dilution means that area farmers have seen the worst of the contamination. The mechanism of contamination was further examined by microbiological sampling and sulfur isotope determinations, which indicated that bacteria of the Thiobacillus species that thrive under neutral pH conditions may have catalyzed sulfide oxidation.Research into the chemical evolution of contamination in this environment not only explains how sulfide oxidation causes contamination despite buffering by carbonate rocks, but also suggests how oxidation is initiated in the case of acid mine drainage.     

Polychlorinated biphenyls and -naphthalenes in pine needles and soil from Poland--concentrations and patterns in view of long-term environmental monitoring

Pine needles were selected as cost effective and easy collectable matrices suitable for long-term monitoring of the lower troposphere pollution with polychlorinated biphenyls and polychlorinated naphthalenes. The fingerprints of PCNs and PCBs in the top layers of agricultural soils were used for determination of point sources of pollution for terrestrial ecosystems. The new idea based on the use of nona- and decachlorinated isomers fingerprint as an additional tool suitable for the identification of potential point sources of pollution with PCBs, seemed to be a capable tool to identify contamination of soil and ambient air related to former manufacturing and the use of highly chlorinated technical PCB preparations.     

Partitioning microbial respiration between jet fuel and native organic matter in an organic-rich long time-contaminated aquifer

The relative importance of jet fuel biodegradation relative to the respiration of natural organic matter in a contaminated organic-rich aquifer underlying a fire training area at Tyndall Air Force Base, Florida, USA was determined with isotopic measurements. Thirteen wells were sampled and analyzed for BTX (benzene, toluene, xylene), dissolved inorganic carbon (DIC) and CH4 concentrations, and delta13C and 14C of DIC. Results range from non-detectable to 3790 ppb, 1.4-24 mM, 0.2-776 microM, +5.8 per thousand to -22 per thousand, and from 52 to 99 pmc, respectively. Residual fuel was confined to two center wells underlying the fire training area. DIC and CH4 concentrations were elevated down-gradient of the contamination, but also at sites that were not in the apparent flow path of the contaminated groundwater. DIC exhibited greatest delta13C enrichment at highest DIC and CH4 concentrations indicating that CH4 production was an important respiration mode. Radiocarbon-depleted DIC was observed at sites with high hydrocarbon concentrations and down-gradient of the site. The results indicate that while natural attenuation was not rapidly reducing the quantity of free product overlying the aquifer at the site of contamination, it was at least constraining its flow away from the spill site. Apparently under the conditions of this study, BTX was degraded as rapidly as it was dissolved.     

Polychlorinated naphthalenes in sediments from the Venice and Orbetello lagoons, Italy

The purpose of this study was to evaluate the contamination caused by polychlorinated naphthalenes in two polluted Mediterranean lagoons. Surface sediment samples from Venice and Orbetello lagoons were analysed using HRGC-HRMS. The levels of the sum of mono- to octa-CN ranged from 0.03 to 1.51 ng/g. Differences in PCN levels were observed as a function of the sampling site, with levels at the industrial sites exceeding those at the control sites. Although the PCN patterns and profiles resembled one another in different sediment samples, they differed considerably when compared with those in the technical PCN formulation Halowax 1014.     

Immunoassay of red dyes based on the monoclonal antibody of β-naphthol

The objective of the present study was to develop a multi-analyte immunoassay for the determination of eight red dyes in food samples. Two dye intermediates (2-hydroxy-1-naphthoic acid and 1-amino-2-naphthol) were used as the haptens to produce the monoclonal antibodies. The obtained monoclonal antibodies recognized Sudan 1–4, Para red, Sudan red G, Sudan red B and Acid orange II simultaneously. After evaluation of different antibody/coating antigen combinations, a heterologous indirect competitive enzyme linked immunosorbent assay was developed to determine the eight red dyes in food samples (chili oil, chili powder, tomato sauce, hotpot seasoning). The crossreactivities to the eight analytes were in the range of 61%–79% (with β-naphthol as 100%), and the limits of detection were in the range of 1.3–1.9 ng/mL. The recoveries of the eight analytes from the fortified blank samples were in the range of 84.2%–115% with coefficients of variation lower than 18.3%. Therefore, this method could be used as a rapid and simple tool to detect the residues of the eight red dyes in foods.     

Modelling the closure-related geochemical evolution of groundwater at a former uranium mine

A newly developed reactive transport model was used to evaluate the potential effects of mine closure on the geochemical evolution in the aquifer downgradient from a mine site. The simulations were conducted for the K?nigstein uranium mine located in Saxony, Germany. During decades of operation, uranium at the former mine site had been extracted by in situ acid leaching of the ore underground, while the mine was maintained in a dewatered condition. One option for decommissioning is to allow the groundwater level to rise to its natural level, flooding the mine workings. As a result, pore water containing high concentrations of dissolved metals, radionuclides, and sulfate may be released. Additional contamination may arise due to the dissolution of minerals contained in the aquifer downgradient of the mine. On the other hand, dissolved metals may be attenuated by reactions within the aquifer. The geochemical processes and interactions involved are highly non-linear and their impact on the quality of the groundwater and surface water downstream of the mine is not always intuitive. The multicomponent reactive transport model MIN3P, which can describe mineral dissolution-precipitation reactions, aqueous complexation, and oxidation-reduction reactions, is shown to be a powerful tool for investigating these processes. The predictive capabilities of the model are, however, limited by the availability of key geochemical parameters such as the presence and quantities of primary and secondary mineral phases. Under these conditions, the model can provide valuable insight by means of sensitivity analyses.     

Anthropogenic contaminants as tracers in an urbanizing karst aquifer

Karst aquifers are uniquely vulnerable to contamination. In the Barton Springs segment of the karstic Edwards aquifer (Texas, U.S.A.), urban contaminants such as pesticides and volatile organic compounds frequently are detected in spring base flow. To determine whether contaminant concentrations change in response to storms, and if they therefore might act as tracers of focused recharge, samples were collected from Barton Springs at closely spaced intervals following three storms. Two herbicides (atrazine and simazine), two insecticides (carbaryl and diazinon), and a solvent (tetrachloroethene) described breakthrough curves over a 1-week period following one or more storms. The breakthrough curves were decomposed into two to five log-normal subcurves, which were interpreted as representing pulses of contaminants moving through the aquifer. Each subcurve could be used in the same way as an artificial tracer to determine travel time to and recovery at the spring. The contaminants have several advantages over artificial tracers: they represent the actual compounds of interest, they are injected essentially simultaneously at several points, and they are injected under those conditions when transport is of the most interest, i.e., following storms. The response of storm discharge, specific conductance, and contaminant loading at the spring depended on initial aquifer flow conditions, which varied from very low (spring discharge of 0.48 m3/s) to high (spring discharge of 2.7 m3/s): concentrations and recovery were the highest when initial aquifer flow conditions were low. This behavior provides information about aquifer structure and the influence of aquifer flow condition on transport properties.     

Use of tree rings to investigate the onset of contamination of a shallow aquifer by chlorinated hydrocarbons

Oaks (Quercus velutina Lam.) growing over a shallow aquifer contaminated by chlorinated hydrocarbons were studied to determine if it was possible to estimate the approximate year that contamination began. The annual rings of some trees downgradient from the contaminant release site contained elevated concentrations of chloride possibly derived from dechlorination of contaminants. Additionally, a radial-growth decline began in these trees at approximately the same time that chloride became elevated. Growth did not decline in trees that contained smaller concentrations of chloride. The source of elevated chloride and the corresponding reductions in tree growth could not be explained by factors other than contamination. On the basis of tree-ring evidence alone, the release occurred in the late 1960s or early 1970s. Contaminant release at a second location apparently occurred in the mid- to late 1970s, suggesting that the area was used for disposal for at least 5 years and possibly longer.     

A field experiment on cation exchange-affected multicomponent solute transport in a sandy aquifer

A field experiment was performed in an aquifer in order to study multicomponent cation-exchange processes under natural flow conditions. The aquifer is a glacial outwash plain with sandy aquifer material having a cation-exchange capacity (CEC) of 1.0 meg/100 g. A continuous injection of groundwater spiked with sodium and potassium as chlorides was accomplished over 37 days to resemble leachate contamination from landfills. The plume was monitored by sampling in a dense spatial network (length 100 m, width 20 m) over a period of 2.5 years in order to obtain breakthrough curves and spatial contour maps of the chemical compounds. Na and especially K showed a substantial retardation caused by cation-exchange processes despite the low CEC of the aquifer material. The average velocity of K⁺ was only 10% of the velocity of chloride (0.7 m day⁻¹). The relative migration velocity of Na⁺ was not a constant in the plume, but apparently influenced by dilution. Ca²⁺ and Mg²⁺ were expelled from the cation-exchange sites of the aquifer material and subsequently transported with the same velocity as chloride. The breakthrough curves of the various compounds showed multiple peaks and low concentration zones. It was concluded by calculations with PHREEQE that changes in calcite equilibrium may occur in the lower part of the aquifer, while complexation processes seem to be of no importance. Cation exchange is then the most important process in this field experiment, and further evaluation of the data by a geochemical transport model including cation exchange is recommended.     

Partitioning studies of coal-tar constituents in a two-phase contaminated ground-water system

Organic compounds derived from coal-tar wastes in a contaminated aquifer in St. Louis Park, Minnesota, were identified, and their partition coefficients between the tar phase and aqueous phase were determined and compared with the corresponding n-octanol/water partition coefficients. Coal tar contains numerous polycyclic aromatic compounds, many of which are suspected carcinogens or mutagens. Groundwater contamination by these toxic compounds may pose an environmental health hazard in nearby public water-supply wells. Fluid samples from this aquifer developed two phases upon settling: an upper aqueous phase, and a lower oily-tar phase. After separating the phases, polycyclic aromatic compounds in each phase were isolated using complexation with N-methyl-2-pyrrolidone and identified by fused-silica capillary gas chromatography/mass spectrometry. Thirty-one of the polycyclic aromatic compounds were chosen for further study from four different classes: 12 polycyclic aromatic hydrocarbons, 10 nitrogen heterocycles, 5 sulfur heterocycles, and 4 oxygen heterocycles. Within each compound class, the tar/water partition coefficients of these compounds were reasonably comparable with the respective n-octanol/water partition coefficient.     

Contamination potential of nitrogen compounds in the heterogeneous aquifers of the Choushui River alluvial fan, Taiwan

This study aimed to analyze the contamination potential associated with the reactive transport of nitrate-N and ammonium-N in the Choushui River alluvial fan, Taiwan and to evaluate a risk region in developing a groundwater protection policy in 2021. In this area, an aquifer redox sequence provided a good understanding of the spatial distributions of nitrate-N and ammonium-N and of aerobic and anaerobic environments. Equiprobable hydraulic conductivity (K) fields reproduced by geostatistical methods characterized the spatial uncertainty of contaminant transport in the heterogeneous aquifer. Nitrogen contamination potential fronts for high and low threshold concentrations based on a 95% risk probability were used to assess different levels of risk. The simulated result reveals that the spatial uncertainty of highly heterogeneous K fields governs the contamination potential assessment of the nitrogen compounds along the regional flow directions. The contamination potential of nitrate-N is more uncertain than that for ammonium-N. The high nitrate-N concentrations (> or =3 mg/L) are prevalent in the aerobic environment. The low concentration nitrate-N plumes (0.5-3 mg/L) gradually migrate to the mid-fan area and to a maximum distance of 15 km from the aerobic region. The nitrate-N plumes pose a potential human health risk in the aerobic and anaerobic environments. The ammonium-N plumes remain stably confined to the distal-fan and partial mid-fan areas.     

Processes controlling the distribution and natural attenuation of dissolved phenolic compounds in a deep sandstone aquifer

Processes controlling the distribution and natural attenuation (NA) of phenol, cresols and xylenols released from a former coal-tar distillation plant in a deep Triassic sandstone aquifer are evaluated from vertical profiles along the plume centerline at 130 and 350 m from the site. Up to four groups of contaminants (phenols, mineral acids, NaOH, NaCl) form discrete and overlapping plumes in the aquifer. Their distribution reflects changing source history with releases of contaminants from different locations. Organic contaminant distribution in the aquifer is determined more by site source history than degradation. Contaminant degradation at total organic carbon (TOC) concentrations up to 6500 mg l(-1) (7500 mg l(-1) total phenolics) is occurring by aerobic respiration NO3-reduction, Mn(IV)-/Fe(III)-reduction, SO4-reduction, methanogenesis and fermentation, with the accumulation of inorganic carbon, organic metabolites (4-hydroxybenzaldehyde, 4-hydroxybenzoic acid), acetate, Mn(II), Fe(II), S(-II), CH4 and H2 in the plume. Aerobic and NO3-reducing processes are restricted to a 2-m-thick plume fringe but Mn(IV)-/Fe(II)-reduction, SO4-reduction, methanogenesis and fermentation occur concomitantly in the plume. Dissolved H2 concentrations in the plume vary from 0.7 to 110 nM and acetate concentrations reach 200 mg l(-1). The occurrence of a mixed redox system and concomitant terminal electron accepting processes (TEAPs) could be explained with a partial equilibrium model based on the potential in situ free energy (deltaGr) yield for oxidation of H2 by specific TEAPs. Respiratory processes rather than fermentation are rate limiting in determining the distribution of H2 and TEAPs and H2 dynamics in this system. Most (min. 90%) contaminant degradation has occurred by aerobic and NO3-reducing processes at the plume fringe. This potential is determined by the supply of aqueous O2 and NO3 from uncontaminated groundwater, as controlled by transverse mixing, which is limited in this aquifer by low dispersion. Consumption to date of mineral oxides and SO4 is, respectively, <0.15% and 0.4% of the available aquifer capacity, and degradation using these oxidants is <10%. Fermentation is a significant process in contaminant turnover, accounting for 21% of degradation products present in the plume, and indicating that microbial respiration rates are slow in comparison with fermentation. Under present conditions, the potential for degradation in the plume is very low due to inhibitory effects of the contaminant matrix. Degradation products correspond to <22% mass loss over the life of the plume, providing a first-order plume scale half-life >140 years. The phenolic compounds are biodegradable under the range of redox conditions in the aquifer and the aquifer is not oxidant limited, but the plume is likely to be long-lived and to expand. Degradation is likely to increase only after contaminant concentrations are reduced and aqueous oxidant inputs are increased by dispersion of the plume. The results imply that transport processes may exert a greater control on the natural attenuation of this plume than aquifer oxidant availability.     

Groundwater contamination mechanism in a geothermal field: a case study of Balcova, Turkey

The Balcova Geothermal Field (BGF) located in Izmir, Turkey is situated on an east-west directed graben plain within which the hot waters surface from a fault zone that cuts the Mesozoic aged Bornova Flysch. Due to the low permeability and porosity of the Bornova Flysch, the geothermal water cycles along the immediate vicinity of the Agamemnon fault and mixes with cold waters at different depths of this fractured zone. Within the scope of this study, the mixing patterns and the groundwater contamination mechanisms are analyzed by, hydrogeological and hydrogeochemical methods. Based on the results of this research, it has been found out that the hot geothermal water and the cold regional groundwater resources of the surficial aquifer mix within the fractured zone in Bornova Flysch and within the Quaternary alluvium aquifer due to natural and anthropogenic activities including (i) the natural upward movement of geothermal fluid along the fault line, (ii) the accelerated upward seepage of geothermal fluid from faulty constructed boreholes drilled in the area, (iii) the faulty reinjection applications; and, (iv) the uncontrolled discharge of waste geothermal fluid to the natural drainage network. As a result of these activities, the cold groundwater reserves of the alluvial aquifer are contaminated thermally and chemically in such a way that various toxic chemicals including arsenic, antimony and boron are introduced to the heavily used surficial aquifer waters hindering their use for human consumption and agricultural irrigation. Furthermore, the excessive pumping from the surficial aquifer as well as the reduced surface water inflow into BGF due to the dam constructed on Ilica Creek intensify the detrimental effects of this contamination. Based on the results of this study, it can be concluded that the groundwater pollution in BGF will expand and reach to the levels of no return unless a series of preventive measures is taken immediately.     

Certain organochlorine and organobromine contaminants in Swedish human milk in perspective of past 20-30 years

The investigations of organochlorine compounds in breast milk from women living in the Stockholm region started in 1967. The present study summarises the investigations of polychlorinated biphenyls (PCBs), naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), polybrominated diphenyl ethers (PBDEs) and pesticides (DDT, DDE, hexachlorobenzene, dieldrin) as well as methylsulfonyl metabolites of PCBs and DDE in human milk sampled during different periods up to 1997. During the course of 20-30 yr the levels of organochlorine compounds in human milk have decreased to various extent. A decrease to the half of the original concentration was attained in the range of 4-17 yr periods. On the contrary to the organochlorine compounds, the concentrations of PBDEs have increased during the period 1972-1997, indicating a doubling of the levels by 5 yr. The levels reflect the environmental contamination and background levels in the population. The accumulation and ongoing increase in the levels of PBDEs calls for immediate measures to stop the environmental pollution and human exposure to PBDEs.