Organics In Groundwater Research Articles

Anthropogenic Organic Pollutants in Groundwater Increase Releases of Fe and Mn from Aquifer Sediments: Impacts of Pollution Degree, Mineral Content, and pH

In many aquifers around the world, there exists the issue of abnormal concentrations of Fe and Mn in groundwater. Although it has been recognized that the main source of this issue is the release of Fe and Mn from aquifer sediments into groundwater under natural environmental conditions, there lacks enough reliable scientific evidence to illustrate whether the pollutants imported from anthropogenic activities, such as organics, can increase this natural release. On the basis of time series analysis and comparative analysis, the existence of an increasing effect was verified through laboratorial leaching test, and the impacts of aquatic chemical environment conditions, such as pH, on the effect were also identified. The results showed that the increase of organics in groundwater made the release of Fe and Mn more thorough, which was favorable for the increase of groundwater concentrations of Fe and Mn. The higher the contents of Fe- and Mn-bearing minerals in aquifer sediments, the higher the concentrations of Fe and Mn in groundwater after the release reaches kinetic equilibrium. Lower pH can make the leaching more thorough, but the neutral environment also increases the amount of Mn. It can be deduced that the pollutants such as organics imported by anthropogenic activities can indeed increase the releases of Fe and Mn from aquifer sediments into groundwater, thus worsening the issue of groundwater Fe and Mn pollution. The findings provide a deeper insight into the geochemical effects of Fe and Mn in the natural environment, especially in the groundwater system.

Distinguishing Natural from Anthropogenic Sources of Acid Extractable Organics in Groundwater near Oil Sands Tailings Ponds.

Distinguishing between naphthenic acids (NAs) associated with oil sands process-affected water (OSPW) and those found naturally in groundwaters in contact with the bituminous McMurray Formation poses a considerable analytical challenge to environmental research in Canada's oil sands region. Previous work addressing this problem combined high-resolution Orbitrap mass spectrometry with carbon isotope values generated by online pyrolysis (δ13Cpyr) to characterize and quantify the acid extractable organics (AEOs) fraction containing NAs in the subsurface near an oil sands tailings pond. Here, we build upon this work through further development and application of these techniques at two different study sites near two different tailings ponds, in conjunction with the use of an additional isotopic tool-sulfur isotope analysis (δ34S) of AEOs. The combined use of both δ13Cpyr and δ34S allowed for discrimination of AEOs into the three end-members relevant to ascertaining the NA environmental footprint within the region: (1) OSPW; (2) McMurray Formation groundwater (i.e., naturally occurring bitumen), and; (3) naturally occurring non-bitumen. A Bayesian isotopic mixing model was used to determine the relative proportions of these three sources in groundwater at both study sites. Although background levels of OSPW-derived AEOs were generally low, one sample containing 49-99% (95% credibility interval) OSPW-derived AEOs was detected within an inferred preferential flow-path, highlighting the potential for this technique to track tailings pond seepage.

Sunlight mediated passive wastewater treatment technology using photochemical reduction of ferric iron for decontamination of various aqueous contaminants

This paper demonstrates the feasibility of a very simple and novel, “passive” sunlight mediated photochemical process using ferric chloride for degradation of a wide range of organic contaminants. Batch experiments were conducted under natural sunlight to study the degradation of carbamazepine (CBZ), sulfolane and acid extractable organics of oil sands process water (OSPW) in the presence of 100 mg/L of ferric chloride at pH 2.7–3. The efficacy of the process was also evaluated by studying the degradation of the contaminants in actual wastewater and groundwater samples. All three contaminants were resistant to photodegradation under sunlight in the absence of ferric chloride. CBZ in wastewater and pure water was completely degraded in the presence of ferric species under sunlight within 2 h. Kinetics of degradation of CBZ was fastest in groundwater as more than 99.9% of CBZ was degraded within 30 min. Rate of reduction of Fe(III) to Fe(II) was proportional to kinetics of CBZ degradation in aqueous samples. Over an irradiation period of 7 h, more than 50% of TOC was removed by sunlight mediated iron reduction of CBZ in spiked water and secondary treated wastewater. In contrast to CBZ, sulfolane degraded faster in deionised water (4.5 h−1) with more than 50% reduction in TOC. Unaltered rates of increase in Fe(II) concentration in groundwater spiked with sulfolane and CBZ signifies the presence of easily degradable organics in groundwater competing with sulfolane for the reactive species. GC–MS analysis showed more than 60% reduction in acid extractable organics present in OSPW 7 h of sunlight irradiation in the presence of ferric chloride. Overall, photochemical iron reduction shows great promise as highly sustainable treatment process for decontamination of variety of recalcitrant contaminants in their inherent aquatic environments with marginal effects imparted by other aquatic species.

Life cycle of petroleum biodegradation metabolite plumes, and implications for risk management at fuel release sites.

This paper summarizes the results of a 5-y research study of the nature and toxicity of petroleum biodegradation metabolites in groundwater at fuel release sites that are quantified as diesel-range "Total Petroleum Hydrocarbons" (TPH; also known as TPHd, diesel-range organics (DRO), etc.), unless a silica gel cleanup (SGC) step is used on the sample extract prior to the TPH analysis. This issue is important for site risk management in regulatory jurisdictions that use TPH as a metric; the presence of these metabolites may preclude site closure even if all other factors can be considered "low-risk." Previous work has shown that up to 100% of the extractable organics in groundwater at petroleum release sites can be biodegradation metabolites. The metabolites can be separated from the hydrocarbons by incorporating an SGC step; however, regulatory agency acceptance of SGC has been inconsistent because of questions about the nature and toxicity of the metabolites. The present study was conducted to answer these specific questions. Groundwater samples collected from source and downgradient wells at fuel release sites were extracted and subjected to targeted gas chromatography-mass spectrometry (GC-MS) and nontargeted two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-MS) analyses, and the metabolites identified in each sample were classified according to molecular structural classes and assigned an oral reference dose (RfD)-based toxicity ranking. Our work demonstrates that the metabolites identified in groundwater at biodegrading fuel release sites are in classes ranked as low toxicity to humans and are not expected to pose significant risk to human health. The identified metabolites naturally attenuate in a predictable manner, with an overall trend to an increasingly higher proportion of organic acids and esters, and a lower human toxicity profile, and a life cycle that is consistent with the low-risk natural attenuation paradigm adopted by many regulatory agencies for petroleum release sites. Integr Environ Assess Manag 2017;13:714-727. © 2016 The Authors. Integrated Environmental Assessment and Management Published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Health Implications of Organics in Groundwater : Some Management Perspectives

Summary Organic solvents comprise a large group of compounds, with a variety of chemical structures. Their common characteristic, related to their widespread use in many industrial processes, is the ability to dissolve and readily disperse fats, oils, waxes, paints, pigments, varnishes, rubber and many other materials. “Lilis (1990), states that little is known about the natural history and prognostic significance of chronic solvent effects; at least part of the explanation is to be found in the subjective nature of most of the systems and the paucity of studies using objective methods for the assessment of neurological status.” This paper examines the above issue in terms of its management by healthcare authorities and the implications of organics in groundwater. It also attempts to expose the health worker to the dynamics and dangers of organics in groundwater.

Evaluating degradation rates of chlorinated organics in groundwater using analytical models

The persistence and fate of organic contaminants in the environment largely depends on their rate of degradation. Most studies of degradation rate are performed in the lab where chemical conditions can be controlled precisely. Unfortunately, literature values for lab degradation studies often are orders of magnitude higher than for field-generated studies, calling into question the relevance of lab-generated values for characterizing the persistence of organic contaminants in the environment. Complicating analysis of this ostensible disparity between lab and field degradation values, field-generated values often do not account for effects of adsorption. Modeling with a newly derived analytical solution for first-order degradation coupled with advective losses and adsorption to solve for degradation constants is insensitive to uncertainties in field properties. Application to field data shows that accounting for advection and adsorption greatly affects the value of calculated degradation constants compared to disappearance constants, which do not account for these phenomena. In fact, degradation constants, calculated using these analytical solutions and field data, are in the range reported for lab-generated data. Using these analytical solutions, for the sulfate-reducing field conditions documented for this site, perchloroethene, trichloroethene, 1,1,1-trichloroethane, 1,1-dichloroethane, and chloroethane all degraded with half-lives ranging from 5 to 115 d. Consistent with other studies of sulfate-reducing conditions, cis-1,2-dichloroethene did not chemically degrade at a measurable rate. When nonaqueous phase 1,1-dichloroethane is present, down-gradient concentrations vary in an annual sinusoidal pattern, apparently because of seasonal variation in dilution from groundwater recharge.

Analytical Currents: Organics in groundwater

Analytical Currents: Organics in groundwater

96/04427 Natural attenuation of coal tar organics in groundwater

96/04427 Natural attenuation of coal tar organics in groundwater

Characterization of organics in whiteshell research area groundwater and the implications for radionuclide transport

Naturally occurring organics in groundwaters of the Whiteshell Research Area (WRA) of southern Manitoba were investigated to assess their potential role in radionuclide transport within granite fractures of the Canadian Shield. A survey of dissolved organic carbon concentrations, carried out to determine the variability in the organic content of these groundwaters, showed average concentrations of 0.8 ± 0.1 mg/L for Fracture Zone 2, 0.8 ± 0.4 mg/L for near-vertical fractures and 2.3 ± 0.8 mg/L for deeper saline groundwater. The dissolved organic carbon consisted mainly of hydrophilic neutral compounds (60 to 75%), and hydrophobic and hydrophilic acids (23 to 39%), along with very small amounts of hydrophobic bases and neutrals, and hydrophilic bases. Significant contamination from drilling operations and plastics, mostly in the form of hydrophobic neutrals, was observed in some samples. These compounds would not contribute to radionuclide migration in a natural system and are not included in the assessment of the organic complexing capacity of these groundwaters. Based on groundwater concentrations of hydrophobic and hydrophilic acids and on the measured car☐ylic functional group content of these acids, the average complexing capacity of natural organics in Whiteshell Research Area groundwaters was calculated to be 2.9 × 10 −6 eq/L. The ability of these organics to complex radionuclides was tested using conditional stability constants from the literature for humic complex formation with Am(III), Th(IV), and U(VI). The chemistry of U(VI) was predicted to be dominated by inorganic complexes and not significantly affected by organics. The literature contains a wide range in values of stability constants for Am(III) and Th(IV) complexes with humics. The aqueous chemistry of Am(III) and Th(VI) could be affected by complexation with natural organics if the higher stability constant values are valid for WRA groundwaters.

Octadecylthiol-modified surface-enhanced Raman spectroscopy substrates: a new method for the detection of aromatic compounds

A method for detection of aromatic organics in groundwater has been tested. It was found that use of surface-enhanced Raman scattering and an octadecylthiol coating on roughened silver produced a system which could partition the organics out of water into the strongly Raman enhanced region near the silver surface. The selectivity of the method was illustrated with the three isomers of xylene. Sensitivity was tested with benzene and naphthalene. The detection limits are 7.5 and 2.3 ppm for benzene and naphthalene, respectively. It was found that the calibrations followed a Langmuir-type isotherm at low solution concentrations. 22 refs., 8 figs.

Economics of screening in the detection of organics in ground water

Rajagopal, R., 1990. Economics of screening in the detection of organics in ground water. Chemometrics and Intelligent Laboratory Systems, 9: 261–272. Screening may be defined as the use of efficient test procedures to determine and/or to quantify the presence or absence of contaminants in samples. In support of screening, many commercial laboratories offer price-breaks when analysis for only a few compounds are sought instead of a standard scan (such as those required under a governmental regulatory program). Screening is a step-wise or a decision tree approach to sampling and analysis. For a fixed number of compounds in a screen, a model to maximize the total expected number of positive determinations (detections) of organic compounds in ground water samples is developed and evaluated. This model is tested with extensive data on organic measurements obtained from ground-water samples at hazardous waste sites. The economic viability of the model is evaluated within the context of price-breaks in analytical services offered by commercial laboratories. For a set of price-breaks assumptions, screening is shown to be far superior in the detection of pesticide, acid, and base neutral compounds than in the detection of volatile organic compounds in ground water at hazardous waste sites. By incorporating relevant QA/QC costs, it is further shown that screening is a cost-effective alternative for all groups of organic compounds. A few promising avenues for further research are also outlined.

Simulation of biodegradable organic contaminants in groundwater: 2. Plume behavior in uniform and random flow fields

The behavior of dissolved organic contaminants in groundwater is often difficult to interpret in field settings because of the complex interaction of physical, chemical, and biological processes. The organic solute transport model presented by MacQuarrie et al. (this issue) is used to examine plume migration in a shallow aquifer where dissolved oxygen is the sole electron acceptor. In uniform groundwater flow a plume originating from a high‐concentration source will experience more spreading and slower normalized mass loss than a plume from a lower initial concentration source because dissolved oxygen is more quickly depleted. Low background dissolved oxygen concentrations also cause organic mass loss to decrease, while the initial size of the microbial population has little effect. Large groundwater velocities produce increases in the rate of organic solute mass loss because of increased mechanical mixing of the organic plume with oxygenated groundwater. Because sorbed organic mass is unavailable for biodegradation, increasing the retardation factor of an organic solute causes slower mass loss. For easily biodegraded organics the mass loss is only weakly dependent on the kinetic biodegradation parameters because the amount of mixing of the organic and dissolved oxygen controls the biodegradation process. This implies that for these types of compounds the kinetic parameters do not need to be known with precision. For all simulations the rate of mass loss for the organic plumes decreased with time because the concentrations of organic and dissolved oxygen decrease with time. In complex‐structured flow fields caused by heterogeneity, the bulk velocity, position, and rate of spreading of an organic plume is strongly dependent on local‐scale transport parameters such as the groundwater velocity in individual beds. Because an organic plume emanating from a small to moderate sized source does not evolve in a manner similar to a conservative plume in heterogeneous materials due to a decrease in the size of the plume, it is suggested that average transport parameters such as macrodispersivity may not be applicable to such organic plume transport. If this is the case, then reliable predictions concerning the ultimate fate of organics in groundwater exemplifies the need for obtaining knowledge about the bedding features and degree of heterogeneity of the host geologic materials.

Relationships between micelle-water and octanol-water partition constants for hydrophobic organics of environmental interest

The partition constants between micelles of sodium dodecyl sulfate and water for eleven hydrophobic non-polar organics of environmental interest were correlated to their octanol-water partition constants, aqueous solubilities and total molecular surface areas. Octanol-water partition constant was found to be the best correlating parameter. Values of partition constants for micelles formed of dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide surfactants were also correlated to the octanol-water partition constants. A possible practical application of the K m− K ow correlation to determine the micellar-mediated transport of hydrophobic organics in ground-water is illustrated.

Physics, chemistry, and biology of organics in groundwater

The Groundwater Committee of AGU's Hydrology Section sponsored this special session at the 1986 Fall Meeting in San Francisco, Calif. The session was chaired by John L. Wilson of the New Mexico Institute of Mining and Technology (New Mexico Tech, Socorro). At earlier meetings a number of sessions had focused on the mathematical modeling of dissolved organic transport. More recently, AGU sponsored a Chapman Conference on “Microbial Processes in the Transport, Fate, and In Situ Treatment of Subsurface Contaminants.” The fall special session was the first to examine a much wider view of the scientific issues and brought together modelers and experimentalists; chemists, biologists, physicists, and engineers.

A Comparison of Three Sampling Devices for Measuring Volatile Organics in Groundwater

ABSTRACT THREE sampling devices, a polyvinyl chloride bailer, a Teflon bailer, and an Isco Model 2600 portable pump, were used to determine their effects on recovery of three volatile organic compounds (VOCs) in groundwater. The three VOCs used chloroform, benzene, and 1, 2-dichloroethane, were chosen from a list of priority pollutants established by the United States Environmental Protection Agency (EPA). The effect on recovery was determined by varying the lift height at 2, 4 and 6 m and by varying the material, either PVC or stainless steel, which cased the wells. A microextraction procedure was used to prepare samples for analysis by gas chromatography. Statistical analyses were performed to determine significant differences in the percent recovery by comparisons of well casing, lift height, sampling method, well vs. height, well vs. method, and height vs. method. No significant differences for any of these comparisons were found. Comparisons of chemicals, well vs. chemical, height vs. chemical, method vs. chemical, well vs. method vs. chemical and height vs. method vs. chemical, were also performed. Only height vs. chemical and height vs. method vs. chemical showed significant differences in percent recovery. These occurred for benzene at 2 m (96.4% recovery) and 6m (89.7%), for chloroform at 2m (96.7%) and 6m (90.1%), and 1,2-dichloreothane at 2m (97.5%) and 6m (90.8%) for the pump. These significant differences were due to the volatilities of the VOCs and the lift height.

Trace organic compounds in groundwater: a survey of unpolluted groundwater from three major British aquifer systems

ABSTRACT In view of the increased concern about the occurrence and persistence of organic chemicals in the environment, the Water Research Centre instigated a baseline survey of trace organics in groundwater from representative cross-sections of three major British aquifer systems. A total of 32 public and private supply boreholes in selected areas of the Permo-Triassic Sandstone, Chalk, Lincolnshire Limestone and the Great Oolite aquifers have been sampled. The areas have been chosen with the aim of characterising the organic content of ‘clean’ groundwater from the confined and unconfined zones on each cross-section. The survey was designed to encompass groundwaters of varying ages, from recent recharge in outcrop areas through to ancient waters in deep confined sections. In this way, it was expected that any compounds of anthropogenic origin would be detected only in the younger groundwaters. The total organic carbon content of the groundwaters sampled was generally very low, between 0.2 and 1.4 mg/1; low levels of aromatic halogenated hydrocarbons, which are generally taken to be contaminants, were found in many of the samples at levels above 0.01 µg/1; low levels of aromatic hydrocarbons were often detected. Although the number of compounds detected averaged 20 per sample (range: 7 to 52), few were present at concentrations greater than 0.1 µg/1. Over 100 different compounds were detected altogether but only 75 could be identified positively. Of these, nine occurred in more than half of the samples. There were no obvious differences in either compound types or levels between the confined and unconfined zones of any of the aquifers. Uncontaminated groundwater examined in this survey may be typified as having a TOC level below 0.8 mg/1, and no more than four compounds (none of which are chlorinated hydrocarbons) present at levels above 0.1 µg/1.

Transport of Organic Compounds Dissolved in Ground Water

AbstractOrganic compounds, such as trichlomethylene (TCE) and chlorobenzene, that have been found in drinking water supplies are of public concern because they are possibly carcinogenic. These substances can now be routinely detected in trace amounts with gas chromatograph mass spectrometers. There are some polar organic compounds, which are not detectable individually by common methods and therefore little is known about them.The transport of organic compounds is more difficult to predict than the flow of ground water because:Trace amounts of pollutants are difficult to measureTransport is complicated if the compound is partitioned into several phasesThe concentration of organics in ground water may vary due to aquifer heterogeneity and other hydrologic factorsReactions with other organic compounds and reactions with the aquifer material (such as adsorption) may affect the mobility of the organicsBiodegradation may also affect net transport.Adsorption is a factor in the attenuation of non‐polar organics in aquifers with significant organic content (>0.1 percent organic carbon). The organic material adsorbs the non‐polar organic chemicals. The mobility of a pollutant in such an aquifer depends on at least two parameters: the levels of dissolved organic matter and the content of organic carbon in the aquifer material. The partition coefficient of the chemical pollutant between the aquifer and water is commonly calculated as a function of the organic content of the aquifer and the partition coefficient between octanol and water.Field and laboratory results reported in the literature indicate that the following organic compounds may be biodegradable under aerobic conditions: alkyl benzenes and chlorobenzenes. Under anaerobic conditions halogenated aliphatics, alkyl benzenes, several pesticides and phenolic compounds may be biodegradable. Halogenated aliphatics appear not to degrade under aerobic conditions and non‐chlorinated aro‐matics and chlorobenzenes appear not to degrade under anaerobic conditions. Alkyl benzenes biode‐grade more rapidly than their halogenated counterparts.

A Syringe and Cartridge Method for Down‐Hole Sampling for Trace Organics in Ground Water

ABSTRACTA newly developed technique which allows the down‐hole sampling and subsequent analysis of ground water for trace organic contaminants was tested during an investigation of contaminant migration at an inactive landfill site in Burlington, Ontario, Canada. The sampling device, which is lowered down piezometers with a tube, consists of a small cylindrical cartridge of sorbent material attached to a syringe. Vacuum or pressure applied at the surface controls the movement of the plunger in the syringe. The volume of the syringe determines the volume of sample water that passes through the cartridge. The cartridge is removed from the syringe at the surface. One cartridge is used for each sampling; the syringe is reusable. The residual water in the cartridge is removed in the laboratory, and the cartridge is desorbed to a fused silica capillary column for analysis by gas chromatography (GC). The analyses discussed here were performed on a GC/mass spectrometer/data system (GC/MS/DS). Of the many organic compounds that were identified in the samples, three compounds were clearly landfill‐related: 1,1,1‐trichloroethane, chlorobenzene, and para‐dichlorobenzene. The three compounds were found at levels substantially above blank levels in 9, 5, and 5 piezometers, respectively. The average concentrations were 14., 5.3, and 0.88μg/1 (ppb), respectively. The pooled coefficients of variation for the analyses for the three compounds were 27., 6.9, and 6.4%, respectively. The volatility of 1,1,1‐trichloroethane was probably the cause of the greater variability in its analytical data. The main advantages of the technique over most conventional sampling methods include: (1) down‐hole sampling in a manner which minimizes the potential for volatilization losses; (2) avoidance of passage of the sample through long sections of tubing that may contaminate the sample or cause adsorptive losses; (3) convenience of sample handling, storage, and shipping; and (4) high sensitivity.

Health implications of organics in groundwater.

Health implications of organics in groundwater.

Movement of organic contaminants in groundwater: implications for water supply

Contamination of groundwaters in the United States by organic compounds is reviewed in terms of its occurrence, behavior, and treatment. In particular, the sorption, dispersion, advection, and degradation of organics in groundwater are considered.