Emerging Contaminants, Fate and Transport, Organic Contaminants Research Papers (original) (raw)

Emerging organic compounds EOC are substances which have been only recently determined as pollutants, and substances which have been newly developed or discovered in the environment. EOC in groundwater can cause adverse effects on the environment and human health. They enter into the natural environment as a result of various anthropogenic activities. The article provides an overview of emerging organic pollutants that occur in groundwater. These compounds are drug residues, substances originating from personal care products, pesticides, veterinary products, food additives, nanomaterials, industrial and other compounds found in wastewater. The article describes the main sources and the presence of EOC in groundwater, pathways and potential impacts (risks). An overview of EOC detection research in the world is presented. Within the review of Slovenian studies the investigations dealing with the determination of wide spectrum of EOC presence in groundwater, with drug residues in groundwater and waste water, or with the development of analytical methods for these substances were analyzed. From the entire analysis we inferred that we must be aware of the possible presence of EOC risk in groundwater even in small concentrations. To reduce the yet to some extent unknown risks, it is necessary to determine EOC threshold values in groundwater and their impact. In the future it will be necessary to identify new pollutants, to develop new analytical methods to determine their sources and routes, and in particular, to establish monitoring for these substances.

The word contaminant is a general term to describe dissolved constituents, nonaqueous phase liquids (NAPLs), or industrial solvents which, when added to water as a result of human activities, impair groundwater quality. To an important extent, the complexity of a groundwater contamination problem can be determined by whether or not NAPLs are present. Obviously, contaminants related to anthropogenic activities are one of the major threats facing groundwater resources today. Groundwater contamination can have a significant impact on the present and future use of groundwater resources as a source of drinking water for an increasing population living in cities and rural areas.

Despite being one of the most important oil producing provinces in the United States, information on basinal hy-drogeology and fluid flow in the Permian Basin of Texas and New Mexico is lacking. The source and geochemistry of brines from the basin were investigated (Ordovician-to Guadalupian-age reservoirs) by combining previously published data from conventional reservoirs with geochemical results for 39 new produced water samples, with a focus on those from shales. Salinity of the Ca–Cl-type brines in the basin generally increases with depth reaching a maximum in Devonian (median = 154 g/L) reservoirs, followed by decreases in salinity in the Silurian (median = 77 g/L) and Ordovician (median = 70 g/L) reservoirs. Isotopic data for B, O, H, and Sr and ion chemistry indicate three major types of water. Lower salinity fluids (b 70 g/L) of meteoric origin in the middle and upper Permian hydrocarbon reservoirs (1.2–2.5 km depth; Guadalupian and Leonardian age) likely represent meteoric waters that infiltrated through and dissolved halite and anhydrite in the overlying evaporite layer. Saline (N 100 g/L), isotopically heavy (O and H) water in Leonardian [Permian] to Pennsylvanian reservoirs (2–3.2 km depth) is evaporated, Late Permian seawater. Water from the Permian Wolfcamp and Pennsylvanian " Cline " shales, which are isotopically similar but lower in salinity and enriched in alkalis, appear to have developed their composition due to post-illitization diffusion into the shales. Samples from the " Cline " shale are further enriched with NH 4 , Br, I and isotopically light B, sourced from the breakdown of marine kerogen in the unit. Lower salinity waters (b100 g/L) in Devonian and deeper reservoirs (N3 km depth), which plot near the modern local meteoric water line, are distinct from the water in overlying reservoirs. We propose that these deep mete-oric waters are part of a newly identified hydrogeologic unit: the Deep Basin Meteoric Aquifer System. Chemical, isotopic, and pressure data suggest that despite over-pressuring in the Wolfcamp shale, there is little potential for vertical fluid migration to the surface environment via natural conduits. Published by Elsevier B.V. This is an open access article under the CC BY license

s u m m a r y A series of calculations and model predictions were used to evaluate the controls on perched-water conditions and constraints on perching occurrence, persistence, and potential impact on groundwater contamination. These simulations considered perched-water conditions that have been observed in the vadose zone above a fine-grained layer located just a few meters above the water table beneath the B-Complex Tank Farms area at the Hanford Site. The perched water, containing elevated concentrations of uranium and technetium-99, is important to consider in evaluating the future flux of contaminated water into the groundwater. A study was conducted to examine the perched-water conditions and quantitatively evaluate (1) factors that control perching behavior, (2) contaminant flux toward groundwater, and, (3) associated groundwater impact. Based on the current vertical transport pathways and large areal extent of the perched system, the evaluation was conducted using a one-dimensional analysis. Steadystate analytical calculations showed that the perching-layer hydraulic conductivity is likely to be up to two orders of magnitude lower than the value obtained from Hanford site material property estimates. Numerical flow and transport simulations provided both steady-state and transient system estimates of water and contaminant behavior and were used to further refine the range of conditions consistent with current observations of perched water height and to provide estimates of future water and contaminant flux to groundwater. Near-term removal of perched water by pumping can decrease the total contaminant mass that will discharge to the groundwater, but will have only a moderate effect on the nearterm discharge rate and corresponding contaminant concentration in groundwater. Combining pumping with a decrease in the recharge rate will be most effective in minimizing the impact to groundwater. These results provide a framework for constraining the behavior of perched aquifer systems especially related to impacts on contaminant transport.

The performance of the Electro-Fenton (EF) process for contaminant degradation depends on the rate of H2O2 production at the cathode via 2-electron dissolved O2 reduction. However, the low solubility of O2 (≈1 × 10−3 mol dm−3) limits H2O2 production. Herein, a novel and practical strategy that enables the synergistic utilization of O2 from the bulk electrolyte and ambient air for efficient H2O2 production is proposed. Compared with a conventional “submerged” cathode, the H2O2 concentration obtained using the “floating” cathode is 4.3 and 1.5 times higher using porous graphite felt (GF) and reticulated vitreous carbon (RVC) foam electrodes, respectively. This surprising enhancement results from the formation of a three-phase interface inside the porous cathode, where the O2 from ambient air is also utilized for H2O2 production. The contribution of O2 from ambient air varies depending on the cathode material and is calculated to be 76.7% for the GF cathode and 35.6% for the RVC foam cathode. The effects of pH, current, and mixing on H2O2 production are evaluated. Finally, the EF process enhanced by the “floating” cathode degraded 78.3% of the anti-inflammatory drug ibuprofen after 120 min compared to only 25.4% using a conventional “submerged” electrode, without any increase in the cost.

Remediation of contaminated soils is often studied using fine-textured soils rather than low-fertility sandy soils, and few studies focus on recontamination events. This study compared aerobic and anaerobic treatments for remediation of freshly introduced used motor oil on a sandy soil previously phytoremediated and bioacclimated (microorganisms already adapted in the soil environment) with some residual total petroleum hydrocarbon (TPH) contamination. Vegetated and unvegetated conditions to remediate anthropogenic fill containing residual TPH that was spiked with nonaqueous phase liquids (NAPLs) were evaluated in a 90-day greenhouse pot study. Vegetated treatments used switchgrass (Panicum virgatum). The concentration of aerobic bacteria were orders of magnitude higher in vegetated treatments compared to unvegetated. Nevertheless, final TPH concentrations were low in all saturated soil treatments, and high in the presence of switchgrass. Concentrations were also low in unvegetated pots with fertilizer. Acclimated indigenous microbial communities were shown to be more effective in breaking down hydrocarbons than introducing microbes from the addition of plant treatments in sandy soils. Remediation of fresh introduced NAPLs on pre-phytoremediated and bioacclimated soil was most efficient in saturated, anaerobic environments, probably due to the already pre-established microbial associations, easily bioavailable contaminants, and optimized soil conditions for microbial establishment and survival.

The effects of "trace" (environmentally relevant) concentrations of the antimicrobial agent sulfamethoxazole (SMX) on the growth, nitrate reduction activity, and bacterial composition of an enrichment culture prepared with groundwater from a pristine zone of a sandy drinking-water aquifer on Cape Cod, MA, were assessed by laboratory incubations. When the enrichments were grown under heterotrophic denitrifying conditions and exposed to SMX, noticeable differences from the control (no SMX) were observed. Exposure to SMX in concentrations as low as 0.005 μM delayed the initiation of cell growth by up to 1 day and decreased nitrate reduction potential (total amount of nitrate reduced after 19 days) by 47% (p=0.02). Exposure to 1 μM SMX, a concentration below those prescribed for clinical applications but higher than concentrations typically detected in aqueous environments, resulted in additional inhibitions: reduced growth rates (p=5×10(-6)), lower nitrate reduction rate potentials (p=0.01), and decreased overall representation of 16S rRNA gene sequences belonging to the genus Pseudomonas. The reduced abundance of Pseudomonas sequences in the libraries was replaced by sequences representing the genus Variovorax. Results of these growth and nitrate reduction experiments collectively suggest that subtherapeutic concentrations of SMX altered the composition of the enriched nitrate-reducing microcosms and inhibited nitrate reduction capabilities.

- by Ronald Harvey
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- Groundwater Contamination, Groundwater Pollution, Public Health, Water Pollution