Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach

A site in mid-western Sweden contaminated with chlorinated solvents originating from a previous dry cleaning facility, was investigated using conventional groundwater analysis combined with compound-specific isotope data of carbon, microbial DNA analysis, and geoelectrical tomography techniques. We show the value of this multidisciplinary approach, as the different results supported each interpretation, and show where natural degradation occurs at the site. The zone where natural degradation occurred was identified in the transition between two geological units, where the change in hydraulic conductivity may have facilitated biofilm formation and microbial activity. This observation was confirmed by all methods and the examination of the impact of geological conditions on the biotransformation process was facilitated by the unique combination of the applied methods. There is thus significant benefit from deploying an extended array of methods for these investigations, with the potential to reduce costs involved in remediation of contaminated sediment and groundwater.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01418-5) contains supplementary material, which is available to authorized users.     

Diamondback terrapins as indicator species of persistent organic pollutants: Using Barnegat Bay, New Jersey as a case study

The diamondback terrapin’s (Malaclemys terrapin) wide geographic distribution, long life span, occurrence in a variety of habitats within the saltmarsh ecosystem, predatory foraging behavior, and high site fidelity make it a useful indicator species for contaminant monitoring in estuarine ecosystems. In this study fat biopsies and plasma samples were collected from males and females from two sites within Barnegat Bay, New Jersey, as well as tissues from a gravid female and blue mussels (Mytilus edulis), which are terrapin prey. Samples were analyzed for persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), chlorinated pesticides, and methyl-triclosan. Terrapins from the northern site, Spizzle Creek, closest to influences from industrial areas, had higher POP concentrations for both tissues than terrapins from the less impacted Forsythe National Wildlife Refuge. Sex differences were observed with males having higher contaminant concentrations in fat and females in plasma. PCB patterns in terrapin fat and plasma were comparable to other wildlife. An atypical PBDE pattern was observed, dominated by PBDEs 153 and 100 instead of PBDEs 47 and 99, which has been documented in only a few other turtle species. The typical PBDE patterns measured in mussels, terrapin prey, suggests that the terrapin may efficiently biotransform or eliminate PBDE 47 and possibly PBDE 99. Plasma contaminant concentrations significantly and positively correlated with those in fat. This study addresses several aspects of using the terrapin as an indicator species for POP monitoring: site and sex differences, tissue sampling choices, maternal transfer, and biomagnification.     

Organochlorine contaminants in coastal marine ecosystems of southern Alaska: inferences from spatial patterns in blue mussels (Mytilus trossulus)

We measured the concentrations and chemical structures of persistent organochlorines (OCs) in blue mussels (Mytilus trossulus) from 44 sites across southwest and southeast Alaska in an effort to determine both the sources of these compounds and the extent to which this region might be contaminated. High PCB concentrations were detected at Amchitka, Adak, and Unalaska Islands (83, 430, and 2800 μg kg⁻¹ dry weight, respectively) in the Aleutians with relatively low concentrations elsewhere (7.1-51 μg kg⁻¹ dry weight). Heavy PCB congener profiles (indicative of localized point sources) characterized the high concentration sites whereas distinctly lighter congener profiles (indicative of atmospheric transport) characterized the lower concentration sites. Elevated PCB concentrations at Adak were restricted to a small area along the island’s eastern shore, suggesting either limited dispersion or rapid dilution of these compounds. More uniform chlorinated pesticide concentrations among the collection sites suggests that these compounds are entering the Aleutian ecosystem from distant sources. Pesticide concentrations correlated significantly with seabird density across the islands we sampled, thus identifying biological transport as a delivery mechanism of these compounds to the Aleutian archipelago. Our findings do not implicate persistent organochlorines as a significant factor in the recent pinniped and sea otter population declines across southwest Alaska.     

The Development of a Prediction Model for the Kinetic Constant of Chlorinated Aliphatic Hydrocarbons

Kinetic constants are important design parameters to determine the degradation of a substrate in biological treatment systems. The objective of this study was to develop a regression model using a quantitative structure–activity relationship technique for the prediction of the first-order rate constants (k) of chlorinated aliphatic hydrocarbons (CAHs). The prediction model showed very good correlations between the measured and calculated rate constants of CAHs. It was likely that the higher-order connectivity indices were important factors for the prediction of the kinetic constants, implying more complicated connectivity indices contributed to the prediction of a biological property. This technique would provide a useful tool to establish the kinetics of other CAHs without costly or time-consuming tests.     

固相萃取-高效液相色谱法测定水中氯酚类化合物

采用固相萃取-高效液相色谱法测定水中7种氯酚类化合物,Waters OASIS WAX柱萃取效率最高,最佳萃取时间和洗脱时间分别为60和5 min。该法的线性范围为1.0~40 mg/L,检出限为0.015~0.5μg/L,精密度为0.558%~2.22%,回收率为83.2%~105%。该法适用于地表水及饮用水中氯酚类化合物的检测。     

A History of the Production and Use of Carbon Tetrachloride,Tetrachloroethylene, Trichloroethylene and 1,1,1-Trichloroethane in the United States: Part 2--Trichloroethylene and 1,1,1-Trichloroethane

Carbon tetrachloride (CTC), tetrachloroethylene (PCE), trichloroethylene (TCE) and 1,1,1-trichloroethane (TCA) were four of the most widely used cleaning and degreasing solvents in the United States. Part 2 of this article describes the history of TCE and TCA. TCE production in the United States began in the early 1920s. TCE was used as a replacement for petroleum distillates in the dry-cleaning industry, and became the solvent of choice for vapor degreasing in the 1930s. TCE's use as a degreaser decreased in the 1960s due to toxicity concerns and the increasing popularity of TCA. Significant TCA use began in the 1950s with the development of suitable stabilizer formulations. In the 1990s, TCA was phased out under the Montreal Protocol due to its role in stratospheric ozone depletion.     

The need for bioaugmentation after thermal treatment of a TCE-contaminated aquifer: Laboratory experiments

A microcosm study was conducted to evaluate the need for bioaugmentation after a thermal treatment to anaerobically dechlorinate trichloroethene (TCE) to ethene. The microcosms were either: heated to 100 degrees C and slowly cooled to simulate thermal remediation while bioaugmenting when the declining temperature reached 10 degrees C; or kept at ambient groundwater temperatures (10 degrees C) and bioaugmented for comparison. Aquifer samples from three sediment locations within a TCE-polluted source zone were investigated in duplicate microcosms. In biostimulated (5 mM lactate) and heated microcosms, no conversion of TCE was observed in 4 out of 6 microcosms, and in the remaining microcosms the dechlorination of TCE was incomplete to cDCE (cis-dichloroethene). By comparison, complete TCE dechlorination to ethene was observed in 4 out of 6 heated microcosms that were bioaugmented with a highly enriched dechlorinating mixed culture, KB-1, but no electron donor, and also in 4 of 6 microcosms that were augmented with KB-1 and an electron donor (5 mM lactate). These data suggest that electron donor released during heating, was capable of promoting complete dechlorination coincident with bioaugmentation. Heated microcosms demonstrated less methanogenesis than unheated microcosms, even with elevated H2 concentrations and addition of KB-1, which contains methanogens. This suggests that the heating process suppressed the native microbial community, which can decrease competition with the bioaugmented culture and increase the effectiveness of dechlorination following a thermal treatment. Specifically, cDCE removal rates were four to six times higher in heated than unheated bioaugmented microcosms. This study confirms the need for bioaugmentation following a laboratory thermal treatment to obtain complete dechlorination of TCE.     

Effect of source variability and transport processes on carbon isotope ratios of TCE and PCE in two sandy aquifers

Chlorinated ethenes often migrate over extended distances in aquifers and may originate from different sources. The aim of this study was to determine whether stable carbon isotope ratios remain constant during dissolution and transport of chlorinated ethenes and whether the ratios can be used to link plumes to their sources. Detailed depth-discrete delineation of the carbon isotope ratio in a tetrachloroethene (PCE) plume and in a trichloroethene (TCE) plume was done along cross-sections orthogonal to groundwater flow in two sandy aquifers in the Province of Ontario, Canada. At the TCE site, TCE concentrations up to solubility were measured in one high concentration zone close to the bottom of the aquifer from where dense non-aqueous phase liquid (DNAPL) was collected. A laboratory experiment using the DNAPL indicated that only very small carbon isotope fractionation occurs during dissolution of TCE (0.26 per thousand), which is consistent with field observations. At most sampling points, the delta(13)C of dissolved TCE was similar to that of the DNAPL except for a few sampling points at the bottom of the aquifer close to the underlying aquitard. At these points, a (13)C enrichment of up to 2.4 per thousand was observed, which was likely due to biodegradation and possibly preferential diffusion of TCE with (12)C into the aquitard. In contrast to the TCE site, several distinct zones of high concentration were observed at the PCE site and from zones to zone, the delta(13)C values varied substantially from -24.3 per thousand to -33.6 per thousand. Comparison of the delta(13)C values in the high concentration zones made it possible to divide the plume in the three different domains, each probably representing a different episode and location of DNAPL release. The three different zones could still be distinguished 220 m from the DNAPL sources. This demonstrates that carbon isotope ratios can be used to differentiate between different zones in chlorinated ethene plumes and to link plume zones to their sources. In addition, subtle variations in delta(13)C at plume fringes provided insight into mechanisms of plume spreading in transverse vertical direction. These variations were identified because of the high-resolution provided by the monitoring network.     

活性炭吸附二苯并呋喃的动力学

采用Norit RB1和Monolith两种活性炭吸附气相中低浓度的二苯并呋喃,测定了二苯并呋喃在2种活性炭上的吸附等温线和吸附动力学曲线,分析了气相主体浓度、温度和二苯并呋喃初始浓度等因素对固相有效扩散系数的影响.结果表明,Langmuir吸附等温线模型能够比较准确地描述二苯并呋喃在Norit-RB1和Monolith活性炭上的吸附相平衡;二苯并呋喃在活性炭上的吸附速率受固相扩散控制;固相有效扩散系数随温度的升高而增大,气相浓度和二苯并呋喃初始浓度对固相有效扩散系数影响较小.     

利用攀钢氯化残渣生产低熟料水泥

较系统地研究了氯化残渣、矿渣、熟料、激发剂等掺量对低熟料水泥强度的影响；找出了利用氯化残渣生产低熟料水泥的最佳条件；并对低熟料水泥性能进行了初步探索。试验表明，利用氯化残渣可生产４２５＾＊低熟料水泥，工业废渣的利用率可达７０％。