Chemicals Of Concern Research Articles

Chemical of concern for raising awareness to Indonesian textile sustainability

It is well known that textiles and textile products may contain hazardous compounds. Formally, all imported textiles and textile products must be registered through the Indonesian Custom. Ideally, the Indonesian Custom has the capability to detect chemicals of concern in textiles or textile products entering Indonesian territory. However, this is not the case, particularly for chemicals listed in the Stockholm Convention. The difficulties arise from the lack of identification regarding substances listed in the Stockholm Convention that might be present in textiles, textile products, and finished products. The Indonesian Government has initiated programs to assess the presence of persistent organic pollutants (POPs) in Indonesian territory. Results of the assessment were elaborated in the National Implementation Plan Document on POPs, which was updated recently. Not all substances listed in the Stockholm Convention can be described in depth. Some POPs such as short-chain chlorinated paraffins (SCCPs) and polychlorinated naphthalenes have not been included in Indonesian regulation, particularly in Indonesian Customs Tariff Book, making it extremely difficult to assess them. Nevertheless, a preliminary assessment of polybrominated diphenyl ethers and SCCPs has been carried out. Using the Tier 1 approach, it was revealed that 2,194 tonnes of SCCPs was imported from India to Indonesia, which was listed under HS code 38249090 that covered CP52 (containing 50–54% chlorinated paraffins). Furthermore, another prominent issue for chemicals of concern (CoC) in textiles was the use of lead-containing dyes, nonylphenols, and nonylphenol ethoxylates. The latter two compounds are known to be used in detergents and surfactants during textile manufacturing processes. At present, nonylphenols and nonylphenol ethoxylates are not listed in Indonesian laws for regulated chemicals in textiles and textile products, as well as in the wastewater quality standard for the textile industry. Therefore, to avoid circular economy obstacles of used textiles and textile products and support sustainable Indonesian textiles, a systematic inventory of CoC in textiles is very important.

A chemical credit framework to predict the removal performance of organic chemicals of concern from water through an ozonation process

Ozonation is an effective barrier for removing a wide spectrum of organic Chemicals of Concern (CoC) in a water treatment process. In this study, bench- and full-scale tests were conducted on a secondary treated effluent at the Eastern Treatment Plant (ETP) of Melbourne Water to probe the performance of ozonation in removing CoC in a wastewater discharge. From the secondary treated effluent as the feed to the ozone process, 58 organic chemicals were measured out of a possible 949 compounds by using the AIQS-DB analytical method. A chemical credit framework for the ozonation process has been established according to the bench-scale results. Chemical classifications based on the chemical structures (aromatics, aliphatic and halogenated aliphatic compounds) and reaction rate constants with O3 (KO3) and the ∙OH radical (K∙OH) and a combined O3/TOC ratio and O3 CT value as operating parameters were confirmed to be useful and important in determining whether a chemical would be removed by ozone. It is shown that an O3/TOC ratio of >0.404 was shown to be necessary to overcome the instantaneous ozone demand (IOD) to guarantee enough ozone to oxidise CoC. For CoC with KO3 >105M − 1s − 1 and K∙OH >109M − 1s − 1, an O3/TOC ratio of ≥0.461 or a measurable O3 CT of ≥0.063 mg min/L can achieve log reduction values (LRVs) of ≥1, these are chemicals with aromatic structures; For CoC with low KO3 and high KOH, a combined O3/TOC ratio and O3 CT value inclusive of a chemical structure classification is indicated as necessary criteria to evaluate the removal. UV254 and TOC were demonstrated to be good online surrogates of ozone barrier performance in the absence of continuous O3/TOC ratio and O3 CT value measurements. Full-scale operational results confirm the effective predictions of the chemical credit framework, which highlights the necessity and importance of monitoring both the O3/TOC ratio and O3 CT values to predict the removal efficiency of a given chemical with a known response to O3 or a known chemical structure.

Regionalized chemical footprint method to identify aquatic ecotoxicity hotspots of hard disk drive rare-earth magnets.

The chemical footprint (ChF), which combines life cycle assessment (LCA) and quantitative risk assessment principles, shows promise for exploring localized toxicity impacts of manufacturing processes, which is not achievable with LCA alone. An updated ChF method was applied to the global annual production of a hard disk drive (HDD) rare-earth element (REE) magnet assembly, assuming a supply chain in East and Southeast Asia. Existing REE magnet assembly LCA inventories were combined with supplier manufacturing locations to create a cradle-to-gate spatial unit process inventory. Emissions from the electricity grid for each manufacturing site were downscaled to hydrobasins of interest using the Global Power Plant Database. The predicted no effect concentration (PNEC) was chosen as the ecotoxicity pollution boundary to determine the threshold for dilution of each chemical of concern (CoC) and to calculate the ChF. Finally, a high-resolution hydrological database provided volumes of the freshwater river reach draining each hydrobasin and was used to calculate the dilution capacity (DC), that is, the volume required to remain at or below the PNEC for each CoC. The total ChF of annual REE magnet assembly production was 6.91E12 m3 , with hotspots in watersheds in China and Thailand where REEs are processed and steel metalworking takes place. Metals were the primary CoCs, with cadmium and chromium(VI) comprising 77% of total ChF. Dilution factors ranged from 5E-09 to 9E + 03 of the DC of the waterbody, reflecting the spatial variability in both emissions and DC. An advanced ChF method was demonstrated for HDD REE magnets. Scoping is a key step required to reduce model complexity. The use of regionalized fate factors and standardized hydrological data sets improves the comparability of ChFs across hydrobasins. Additional work to combine data sets into readily available tools is needed to increase usability and standardization of the ChF method and promote wider adoption. Integr Environ Assess Manag 2023;19:272-283. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Source apportionment and health risk assessment of chemicals of concern in soil, water and sediment at a large strontium slag pile area

Strontium (Sr) is an alkaline earth metal that has adverse effects on bone tissue, but received little attention compared to other often-studied metals. This study analyzed the contents/concentrations of Sr, barium (Ba), sulfate (SO42−), sulfide (S2−), and six common metals in 209 multi-media samples, including slag, soil, groundwater, surface water, and sediment, collected at a large Sr slag pile area. Sr was the dominant chemical of concern (COC) in the soil and groundwater, with contents/concentrations being 35.50–32200 mg/kg and 0.57–152 mg/L, respectively, much higher than those reported in previous research. Contents/concentrations of all COCs in the surface water and sediment were relatively low, except Sr content in the sediment near the slag pile. The LogKd value of Sr was calculated to be lower than those of common metals, indicating relatively high mobility of Sr in the aquatic environment. Contamination assessment using Nemerow index indicated near half of the soil and groundwater sampling locations, especially those within and near the slag pile, were heavily contaminated, and Sr was the dominant COC. The positive matrix factorization model suggested four sources for the COCs in soil, including Sr slag pile/SrCO3 production, agricultural activities, industrial activities, and natural sources, with contribution rates of 66.88%, 5.28%, 7.5%, and 20.34%, respectively. Monte Carlo simulation-based probabilistic health risk assessment revealed that the non-carcinogenic risk of groundwater, and the carcinogenic risk of soil and groundwater, were unacceptable. Notably, Sr was the unique COC posing non-carcinogenic risk among the COCs studied. Our results provide the scientific support needed for managing Sr point source impacted area.

Risk Study of Hydrocarbon Impacted Surficial Soil at the Heavy Duty Diesel Generator Plant in Delta Park University of Port Harcourt, Nigeria

Aim: To analyse the potential risk of hydrocarbon polluted surficial soil, from a heavy-duty generator plant at Delta Campus, University of Port Harcourt, Nigeria.
 Study Design: Conceptual site model (CSM).
 Methodology: A CSM was designed and applied prior to sample collection in order to screen for heavy metals and other chemicals of concern (COCs) from three different high-risk points. The CSM showed a credible source-pathway-receptor chain at three high-risk points. Risk assessment associated with the heavy metals was significantly reduced based on the Department of Petroleum Resources (DPR) – Environmental Guidelines and Standards for the Petroleum Industry In Nigeria (EGASPIN) values after 28 days of bioremediation study.
 Results: The hazard quotient of the target (COCs) namely Arsenic, Cadmium, Chromium and Lead was less than one (< 1). This suggests that the study area does not pose significant risk on both Adults and children.
 Conclusion: The evaluation is essential for the formulation of remedial actions and risk-based management plans geared toward risk reduction. In other words, it is an approach to the determination of imminent risk posed by a pollutant to the environmental proxies. Poor education and sensitization of the public on the causal effect of pollution have been identified as a leading cause of indiscriminate pollution of the environment.

Suspect screening and prioritization of chemicals of concern (COCs) in a forest-water reuse system watershed

Much research has assessed organic chemicals of concern (COCs) in municipal wastewater and receiving waters, but few studies have examined COCs in land treatment systems. Many prior studies have implemented targeted methods that quantify a relatively small fraction of COCs present in wastewater and receiving waters. This study used suspect screening to assess chemical features in ground- and surface waters from a watershed where secondary-treated wastewater is irrigated onto 900 ha of temperate forest, offering a more holistic view of chemicals that contribute to the exposome. Chemical features were prioritized by abundance and ToxPi scoring across seasonal sampling events to determine if the forest-water reuse system contributed to the chemical exposome of ground- and surface waters. The number of chemical features detected in wastewater was usually higher than on- and off-site ground- and surface waters; in wastewater, chemical features trended with precipitation in which greater numbers of features were detected in months with low precipitation. The number of chemical features detected in off- and on-site waters was similar. The lower overlap between chemical features found in wastewater and downstream surface waters, along with the similar numbers of features being detected in upstream and downstream surface waters, suggests that though wastewater may be a source of chemicals to ground and surface waters on-site, dissipation of wastewater-derived features (in number and peak area abundance) likely occurs with limited off-site surface water export by the forested land treatment system. Further, the numbers of features detected on site and the overlap between wastewater and surface waters did not increase during periods of low rainfall, counter to our initial expectations. The chemical features tentatively identified in this watershed appear common to features identified in other studies, warranting further examination on the potential for resulting impacts of these on humans and the environment.

Linking Molecular Structure via Functional Group to Chemical Literature for Establishing a Reaction Lineage for Application to Alternatives Assessment.

The evaluation of potential alternatives for chemicals of concern (CoC) requires an understanding of their potential human health and environmental impacts during the manufacture, use, recycle and disposal life stages. During the manufacturing phase, the processes used to produce a desired chemical are defined based on the sequence of chemical reactions and unit operations required to produce the molecule and separate it from other materials used or produced during its manufacture. This paper introduces and demonstrates a tool that links a chemical's structure to information about its synthesis route and the manufacturing process for that chemical. The structure of the chemical is entered using either a SMILES string or the molecule MOL file, and the molecule is searched to identify functional groups present. Based on those functional groups present, the respective named reactions that can be used in its synthesis routes are identified. This information can be used to identify input and output materials for each named reaction, along with reaction conditions, solvents, and catalysts that participate in the reaction. Additionally, the reaction database contains links to internet references and appropriate reaction-specific keywords, further increasing its comprehensiveness. The tool is designed to facilitate the cataloging and use of the chemical literature in a way that allows user to identify and evaluate information about the reactions, such as alternative solvents, catalysts, reaction conditions and other reaction products which enable the comparison of various reaction pathways for the manufacture of the subject chemical. The chemical manufacturing processing steps can be linked to a chemical process ontology to estimate releases and exposures occurring during the manufacturing phase of a chemical.

Optically based quantification of fluxes of mercury, methyl mercury, and polychlorinated biphenyls (PCBs) at Berry's Creek tidal estuary, New Jersey

AbstractBerry's Creek is an urban tidal estuary of the Hackensack River (New Jersey, U.S.A.), with over 10 km of waterways and over 3 km2 of tidal marsh. More than a century of industrial activity has resulted in elevated contaminant concentrations in sediment, water, and biota. Mercury, methyl mercury, and polychlorinated biphenyls (PCBs) have been identified as the primary chemicals of concern (COCs) due to their persistence and bioaccumulation potential in aquatic and nearshore wildlife. As part of a multi‐phased remedial investigation program, OPTically‐based In‐situ Characterization System (OPTICS) field studies were conducted in Berry's Creek to characterize water column contaminant dynamics, specifically to (1) improve understanding of the interrelationship(s) between surface sediment and water column contaminants and (2) quantify the transport of water column COCs between waterways and marshes. Results from OPTICS monitoring indicated that particulate resuspension from the upper 5 mm of the sediment bed during flood and ebb tides and storm flows is the primary process by which COCs are exchanged from bedded sediment to the water column. Analysis of mass exchange of COCs indicated that COCs associated with resuspended particulates are transported from the waterways to the marshes, where they are retained. Dissolved COC exchange from marshes to the waterways was minor (less than 8% of total COC mass in water). Overall, marshes were observed to be net sinks for COCs.

Impact of exogenous organic carbon on the removal of chemicals of concern in the high rate nitrifying trickling filters

The application of fixed bed high rate nitrifying trickling filters (NTFs) for the removal of track organic chemicals of concern (CoC) is less well known than their application to nutrient removal in water treatment. Particularly, the effect of exogenous organic carbon substrate (sucrose) loading on the performance of NTFs is not well understood. A laboratory-scale NTF system was operated in recirculation mode, with the objective of removing ammonia and CoC simultaneously. The efficiency of a high rate NTF for removal both of low concentration of ammonia (5 mg NH4–N L−1) and different concentrations of CoC in the presence of an exogenous organic carbon substrate (30 mg total organic carbon (TOC) L−1) was investigated. In the presence of exogenous organic carbon, the results demonstrated that the high rate NTF was able to successfully remove most of the CoCs investigated, with the removal ranging from 20.2% to 87.54%. High removal efficiencies were observed for acetaminophen (87.54%), bisphenol A (86.60%), trimethoprim (86.24%) and 17α-ethynylestradiol (80.60%). It was followed by the medium removal efficiency for N, N-diethyl-m-toluamide (61.31%) and atrazine (56.90%). In contrast, the removal of caffeine (28.43%) and benzotriazole (20.20%) was poorer in the presence of exogenous organic carbon. The removal efficiency for CoC was also compared with the results obtained in our previous study in the absence of exogenous organic carbon. The results showed that the addition of exogenous organic carbon was able to improve the removal of some of the CoC. Significant TOC percentage removals (45.68%–84.43%) and ammonia removal rate (mean value of 0.44 mg NH4–N L−1 h−1) were also achieved in this study. The findings from this study provide valuable information for optimising the efficiency of high rate NTF for the removal of ammonia, CoC and TOC.

Food contact substances and chemicals of concern: a comparison of inventories

Food contact materials (FCMs) are intended to be in contact with food during production, handling or storage. They are one possible source of food contamination, because chemicals may migrate from the material into the food. More than 6000 FCM substances appear on regulatory or non-regulatory lists. Some of these substances have been linked to chronic diseases, whilst many others lack (sufficient) toxicological evaluation. The aim of this study was the identification of known FCM substances that are also considered to be chemicals of concern (COCs). The investigation was based on the following three FCM lists: (1) the 2013 Pew Charitable Trusts database of direct and indirect food additives legally used in the United States (or Pew for short), (2) the current European Union-wide positive list for plastic FCMs (or Union for short), and (3) the 2011 non-plastics FCM substances database published by EFSA (or ESCO for short). These three lists of food contact substances (Pew, Union, ESCO lists) were compared with the Substitute It Now! (SIN) list 2.1, which includes chemicals fulfilling the criteria listed in article 57 of Regulation (EC) No. 1907/2006 (REACH), and the TEDX database on endocrine-disrupting chemicals. A total of 175 chemicals used in FCMs were identified as COCs. Fifty-four substances present on the SIN list 2.1 were also found on the Union and/or ESCO lists. Twenty-one of those 54 substances are candidates for Substances of Very High Concern (SVHC), and six of these 21 are listed on Annex XIV and intended for phase-out under REACH. In conclusion, COCs used in FCMs were identified and information about their applications, regulatory status and potential hazards was included.

Risk assessment of manufacturing equipment surfaces contaminated with DDTs and dicofol

Decommissioning of manufacturing plant in the chemical industry includes inspection of the surfaces of production equipment for potential contamination and associated health risks. In the present study wipe-samples were taken from the surfaces of dicofol manufacturing equipment at a chemical factory in north China and analyzed for chemicals of concern (COCs). Occupational hygiene assessment was conducted to assess the risks to demolition workers and health risk assessment was performed to evaluate the risks to demolition and general industrial workers. The concentrations of COCs on the equipment surfaces were found to be 0.54–3.75×104mgDDTsm−2 and 0.15–4.38×103mgdicofolm−2. The average concentration of p,p′-DDT does not represent an unacceptable risk to the demolition workers using occupational hygiene assessment. Under the industrial scenario the carcinogenic risks of COCs ranged from 2.28×10−7 to 1.79×10−2 for p,p′-DDT, 6.18×10−7 to 3.04×10−3 for p,p′-DDD and 1.89×10−6 to 0.16 for p,p′-DDE. The non-carcinogenic hazard indices ranged from 3.86×10−3 to 3.03×102 for p,p′-DDT and 1.16×10−3 to 33.94 for dicofol. Both carcinogenic risk and hazard index of COCs under the industrial scenario were higher than under the demolition scenario. Oral ingestion and dermal contact were the major pathways and accounted for >88% of the total exposure of COCs. Parameter sensitivity analysis shows that equipment surface concentration (Cs), frequency of contact with surface (EV), fraction of dust transferred from surface to skin (FTss) and exposure frequency (EF) were the most sensitive parameters and these should be acquired on a site-specific basis. The accuracy of the risk assessment was controlled largely by the variation in the sensitive parameters and the uncertainty of the exposure model for the inhalation pathway.

Sustainable wind‐driven bioventing at a petroleum hydrocarbon–impacted site

AbstractBioventing—the injection of air into the vadose zone to increase microbial activity—is a commonly used, proven technology for remediating volatile organic compounds present in the vadose zone. Passive systems driven by wind or solar power are both more cost‐effective and sustainable than conventional systems. Such a passive system is being applied successfully to remediate a site impacted with total petroleum hydrocarbons (TPH) and benzene, toluene, ethylbenzene, and xylenes (BTEX) in soil. Bioventing technology was approved by the regulatory agency as an interim remedial action to remove chemicals of concern (COCs) in the vadose zone. A bioventing pilot study was conducted to evaluate the effectiveness of COC removal and collect parameters for full‐scale design and implementation. To evaluate the potential to use wind‐driven bioventing technology, two mobile weather stations were installed at the site and monitored for one month for a wind speed study. Based on the pilot‐test data and wind speed research, 12‐inch diameter funnel/vane 360‐degree wind collectors were designed as passive wind‐driven air‐injection devices and connected to existing monitoring wells. The measured air velocity ranged from 20 to 110 feet per minute during the start‐up and the first three months of operation and maintenance. Monitoring indicated a 20 percent oxygen delivery and greater than 90 percent reduction in COC concentrations, demonstrating a successful sustainable remediation with no power requirement and minimal operation and maintenance. © 2012 Wiley Periodicals, Inc.

Analytical solutions of one-dimensional multispecies reactive transport in a permeable reactive barrier-aquifer system

The permeable reactive barrier (PRB) remediation technology has proven to be more cost-effective than conventional pump-and-treat systems, and has demonstrated the ability to rapidly reduce the concentrations of specific chemicals of concern (COCs) by up to several orders of magnitude in some scenarios. This study derives new steady-state analytical solutions to multispecies reactive transport in a PRB–aquifer (dual domain) system. The advantage of the dual domain model is that it can account for the potential existence of natural degradation in the aquifer, when designing the required PRB thickness. The study focuses primarily on the steady-state analytical solutions of the tetrachloroethene (PCE) serial degradation pathway and secondly on the analytical solutions of the parallel degradation pathway. The solutions in this study can also be applied to other types of dual domain systems with distinct flow and transport properties. The steady-state analytical solutions are shown to be accurate and the numerical program RT3D is selected for comparison. The results of this study are novel in that the solutions provide improved modeling flexibility including: 1) every species can have unique first-order reaction rates and unique retardation factors, and 2) daughter species can be modeled with their individual input concentrations or solely as byproducts of the parent species. The steady-state analytical solutions exhibit a limitation that occurs when interspecies reaction rate factors equal each other, which result in undefined solutions. Excel spreadsheet programs were created to facilitate prompt application of the steady-state analytical solutions, for both the serial and parallel degradation pathways.

Successful application of monitored natural attenuation in a surficial aquifer

AbstractGroundwater investigations conducted since 1988 at a Tennessee Department of Environment and Conservation (TDEC) Voluntary Oversight and Assistance Program (VOAP) site located in Millington, Tennessee, have defined the lateral and vertical extent of site chemicals of concern (COCs) consisting of tetrachloroethene (PCE), trichloroethene (TCE), and associated degradation products. Results of a groundwater remedial investigation determined that aquifer conditions were favorable for anaerobic degradation of COCs through reductive dechlorination. A subsequent groundwater feasibility study determined that monitored natural attenuation (MNA) coupled with long‐term groundwater monitoring was the most effective and suitable remedial option for the site. A Record of Decision was issued by the TDEC VOAP approving MNA and long‐term groundwater monitoring as the remedial option for the site, a first for such a site in Tennessee involving chlorinated organics. A groundwater fate and transport model (the 1998 model) developed during the RI was used as the basis for the MNA remedy. Analytical data from 1998 to 2008 indicate COCs in former high‐concentration areas continue to degrade at rates consistent with or ahead of the 1998 model predictions. Evidence of reductive dechlorination is also supported by the continued presence of breakdown products—specifically, vinyl chloride and ethene (terminal endpoint of PCE breakdown through reductive dechlorination). The continued detection of breakdown products along the flow‐path wells also confirms the effectiveness of the MNA remedy at the site. Current analytical data indicate that COC plumes beneath the site are not migrating and are actually retracting. © 2010 Wiley Periodicals, Inc.

Occurrence of iodinated X-ray contrast media in indirect potable reuse systems

A lack of knowledge of the health and environmental risks associated with chemicals of concern (COCs) and also of their removal by advanced treatment processes, such as micro-filtration (MF) and reverse osmosis (RO), have been major barriers preventing establishment of large water recycling schemes. As part of a larger project monitoring over 300 COCs, iodinated X-ray contrast media compounds (ICM) were analysed in treated secondary wastewater intended for drinking purposes. ICM are the most widely administered intravascular pharmaceuticals and are known to persist in the aquatic environment. A direct injection liquid chromatography tandem mass spectrometry (DI–LC–MS/MS) method was used to monitor secondary treated wastewater from three major wastewater treatment plants in Perth, Western Australia. In addition, tertiary water treated with MF and RO was analysed from a pilot plant that has been built as a first step in trialling the aquifer recharge. Results collected during 2007 demonstrate that MF/RO treatment is capable of removing ICM to below the analytical limits of detection, with average RO rejection calculated to be greater than 92%. A screening health risk assessment indicated negligible human risk at the concentrations observed in wastewater.

Effect of Soil Organic Matter Content and pH on Toxicity of Cadmium to Paronychiurus kimi (Lee) (Collembola)

The heterogeneous physico-chemical properties of soil make it difficult to normalize the toxicological effects of metals in the Collembolan species Paronychiurus kimi (Lee). Furthermore, the physico-chemical properties of soil themselves can function as limiting factors that affect population fitness. In this study, the effects of soil organic matter (OM) and pH on the biological performance of P. kimi were assessed, and the influence of these properties on cadmium toxicity to P. kimi was also assessed at the individual and population levels. The OM and pH were found to significantly influence offspring production. All toxicological values of cadmium to P. kimi showed consistent patterns of increase with increasing OM and pH values, implying a decreased toxicity. The 28-d LC 50 values varied from 34.9 to 115.9 mg/kg, and the 28-d EC 50 and 28-d r i =0 also varied depending on the OM and pH values. These findings indicate that the OM and pH values themselves are important factors in determining not only the biological performance of P. kimi but also the toxicity of cadmium to P. kimi on the individual and population levels. Therefore, when ecological risk assessments are conducted for a certain soil, pre-examinations of the effects of abiotic factors and the selection of an appropriate endpoint must be accomplished before establishing levels of chemicals of concern (COC) for a certain species.

Human Risk Assessment for Heavy Metals and as Contamination in the Abandoned Metal Mine Areas, Korea

Cleanup goals for the contaminated sites are established on the basis of risk assessments and rely on the estimated toxicity of the chemicals of concern (COC). Toxicity estimates are based on bioavailability causing risk of adverse health effects on humans. In this study, bioavailability of As, Cu, Pb and Zn in soil was determined by SBET (Simple Bioavailability Extraction Test), and chemical analysis for groundwater and stream water collected from the abandoned mine areas (Dukeum, Dongil, Dongjung, Myungbong and Songchun mine areas) was conducted. High values of cancer risk for As (1.16x10(-5)) were detected through soil ingestion pathways in the Songchun mine area and assessed through water exposure pathways in the all mines except Dukeum. The hazard index value for As in the Songchun mine area (3.625) exceeded 1.0. The results indicated that the ingestion of As-contaminated soil and water by local inhabitants can pose a potential health threat in these mine areas.

Remedial options for chlorinated volatile organics in a partially anaerobic aquifer

AbstractA laboratory study was conducted for the selection of appropriate remedial technologies for a partially anaerobic aquifer contaminated with chlorinated volatile organics (VOCs). Evaluation of in situ bioremediation demonstrated that the addition of electron donors to anaerobic microcosms enhanced biological reductive dechlorination of tetrachloroethene (PCE), trichloroethene (TCE), and 1,1,1‐trichloroethane (1,1,1‐TCA) with half‐lives of 20, 22, and 41 days, respectively. Nearly complete reductions of PCE, TCE, 1,1,1‐TCA, and the derivative cis‐dichloroethene were accompanied by a corresponding increase in chloride concentrations. Accumulation of vinyl chloride, ethene, and ethane was not observed; however, elevated levels of 14CO2 (from 14C‐TCE spiked) were recovered, indicating the occurrence of anaerobic oxidation. In contrast, very little degradation of 1,2‐dichloropropane (1,2‐DCP) and 1,1‐dichlorethane (1,1‐DCA) was observed in the anaerobic microcosms, but nutrient addition enhanced their degradation in the aerobic biotic microcosms. The aerobic degradation half‐lives for 1,2‐DCP and 1,1‐DCA were 63 and 56 days, respectively. Evaluation of in situ chemical oxidation (ISCO) demonstrated that chelate‐modified Fenton's reagent was effective in degrading aqueous‐phase PCE, TCE, 1,1,1‐TCA, 1,2‐DCP, etc.; however, this approach had minimal effects on solid‐phase contaminants. The observed oxidant demand was 16 g‐H2O2/L‐groundwater. The oxidation reaction rates were not highly sensitive to the molar ratio of H2O2:Fe2+:citrate. A ratio of 60:1:1 resulted in slightly faster removal of chemicals of concern (COCs) than those of 12:1:1 and 300:1:1. This treatment resulted in increases in dissolved metals (Ca, Cr, Mg, K, and Mn) and a minor increase of vinyl chloride. Treatment with zero‐valent iron (ZVI) resulted in complete dechlorination of PCE, and TCE to ethene and ethane. ZVI treatment reduced 1,1,1‐TCA only to 1,1‐DCA and chloroethane (CA) but had little effect on reducing the levels of 1,2‐DCP, 1,1‐DCA, and CA. The longevity test showed that one gram of 325‐mesh iron powder was exhausted in reaction with > 22 mL of groundwater. The short life of ZVI may be a barrier to implementation. The ZVI surface reaction rates (ksa) were 1.2 × 10−2 Lm−2h−1, 2 × 10−3 Lm−2h−1, and 1.2 × 10−3 Lm−2h−1 for 1,1,1‐TCA, TCE, and PCE, respectively. Based upon the results of this study, in situ bioremediation appeared to be more suitable than ISCO and ZVI for effectively treating the groundwater contamination at the site. © 2004 Wiley Periodicals, Inc.

Indoor Air Inhalation Risk Assessment for Volatiles Emanating from Light Nonaqueous Phase Liquids

The indoor air inhalation pathway for volatile contaminants in soil and groundwater has received much attention recently. The risk of exposure may be higher when volatile organic compounds (VOCs) reside as constituents of a free product plume below residential or commercial structures than when dissolved in groundwater or adsorbed on soil. A methodology was developed for assessing the potential for vapor phase migration—and associated risk of indoor air inhalation—of volatile constituents from a light nonaqueous phase liquid (LNAPL) plume on top of the water table. The potential risk from inhalation of VOCs in indoor air emanating from a subsurface Jet Fuel 4 (JP-4) plume by hypothetical residential receptors was assessed at a site. Chemicals of concern (COCs) were identified and evaluated using data from the composition of JP-4 mixtures and published chemical, physical, and toxicological data. The method estimates the equilibrium vapor concentrations of JP-4 constituents using Raoult's Law for partial vapor pressure of mixtures based on assumptions about the mixture composition of JP-4. The maximum allowable vapor concentration at the source (immediately above the LNAPL) corresponding to an indoor air target concentration based on acceptable risk levels are calculated using the Johnson and Ettinger model. The model calculates the attenuation factor caused by the migration of the vapor phase VOCs through the soil column above the JP-4 plume and through subsurface foundation slabs. Finally, the maximum allowable soil gas concentrations above the LNAPL for individual constituents were calculated using this methodology and compared to the calculated equilibrium vapor concentrations of each COC to assess the likelihood of potential risk from the indoor air inhalation pathway.

Risk-Based Zoning Strategy for Soil Remediation at an Industrial Site

After determining at an early stage of the project that the future land use of this New Jersey chemical manufacturing site remain industrial in nature, the site was zoned according to risk. The chemicals of concern (COCs) at the site included relatively low levels of mono- and polynuclear aromatic hydrocarbons, chlorinated aliphatics, as well as other volatile and semivolatile compounds. Direct human exposure scenarios were the key to the mitigation of risks related to soils because the groundwater migration pathway was already interrupted using groundwater recovery. A focused remedial strategy was developed to ensure that the exposure pathways (inhalation, ingestion, and dermal contact) are alleviated and the remedial measures are protective to the workers operating and/or maintaining the site. The risk evaluation process included a preliminary risk assessment (Tier 1) based on a comparison with pertinent soil cleanup criteria, a prioritization analysis to rank zones, chemicals and pathways of concern, and an application of the Risk Based Corrective Action (RBCA) approach (Tier 2) for construction worker exposure scenario. The risk assessment identified selected areas that would benefit from remedial actions. Prioritization Analysis classified the site into five high-priority (comprising 97% of the total health-based risk), three medium-priority (contributing to remaining 2 to 3% of the risk), and adequately protected areas. The boundaries and volumes of affected areas were delineated based on confirmatory soil sampling and statistical analyses. The remedial technologies selected for the site have achieved appropriate reduction in risk to comply with all State regulations and include (in addition to the institutional controls):• Capping the site where only immobilesemivolatile contaminants are present• Excavation and on-site treatment of the soils impacted by volatile organic com pounds through ex situ low temperature desorption, or alternative “biopile” treatment and natural attenuation, and• Excavation and off-site disposal of limited volumes of soilsThis risk-based, integral approach helped identify the real significance of contamination present at the site and facilitated the development of suitable and adequate remedies. Had not it been for this approach, the mere comparison with soil cleanup criteria would have unnecessarily resulted in denoting all areas as nuisance contributors, and thus requiring some actions. New Jersey Department of Environmental Protection (NJDEP) has approved this approach and contributed to its accomplishment.