Temporal and spatial variation of polychlorinated biphenyls (PCBs) contamination in environmental compartments of highly polluted area in Central Russia

Controllable chemical redox reactions to couple microbial degradation for organic contaminated sites remediation: A review

Global environmental concern over organic contaminated sites has been progressively conspicuous during the process of urbanization and industrial restructuring. While traditional physical or chemical remediation technologies may significantly destroy the soil structure and function, coupling moderate chemical degradation with microbial remediation becomes a potential way for the green, economic, and efficient remediation of contaminated sites. Hence, this work systematically elucidates why and how to couple chemical technology with microbial remediation, mainly focused on the controllable redox reactions of organic contaminants. The rational design of materials structure, selective generation of reactive oxygen species, and estimation of degradation pathway are described for chemical oxidation. Meanwhile, current progress on efficient and selective reductions of organic contaminants (i.e., dechlorination, defluorination, -NO2 reduction) is introduced. Combined with the microbial remediation of contaminated sites, several consideration factors of how to couple chemical and microbial remediation are proposed based on both fundamental and practical points of view. This review will advance the understanding and development of chemical-microbial coupled remediation for organic contaminated sites.

Depositional environments and historical contamination as a framework to reconstruct fluvial sedimentary evolution

In this study, we explore the variability of sedimentation conditions (e.g., grain-size, accumulation rate, contamination) according to fluvial depositional environments. Indeed, sediment cores are commonly used as archives of natural and anthropogenic activities in hydrosystems, but their interpretation is often complex, especially in a fluvial context where many factors may affect the quality, continuity, and resolution of the record. It is therefore critical to thoroughly understand the nature and dynamics of an environment in which a sediment core is sampled to be able to interpret it. To that end, four depositional environments from a bypassed reach of the Rhône River were comparatively investigated through geophysics in order to assess the range of sedimentation conditions: a floodplain, a semi-active secondary channel, an active secondary channel, and a dam reservoir. Sediment cores were retrieved from each environment and thoroughly characterised (e.g., grain-size, Total Organic Carbon, organic contaminants). Robust age-depth models were elaborated for each core based on ¹³⁷Cs, ²¹⁰Pb_ex, and Persistent Organic Pollutants (POPs) trends. The results show that each depositional environment recorded a different time-period, and therefore different contamination levels and trends. In particular, a shift from polychlorinated biphenyls (PCBs) to polybrominated diphenyl ethers (PBDEs) as the predominant POP in the sediments can be observed, the tipping point being set in the 1970s. Two types of infrastructure-induced legacy sediments related to two periods of river engineering in the reach were also identified using grain-size analysis. The combination of geophysical methods (Ground Penetrating Radar) and sediment cores is therefore confirmed as a relevant methodology that should be promoted in fluvial contexts in order to reconstruct the sedimentary evolution of fluvial corridors. The study also highlights the challenges of dating recent fluvial sediments and proposes a multi-proxy dating methodology using POPs contamination trends.

Carcinogenic and teratogenic status of human population and polychlorinated biphenyls contaminations of soils and biota (European pied flycatcher) in a Perm (Western Ural, Russia)

Polychlorinated biphenyls (PCBs) are included in the persistent organic pollutants designated by the Stockholm Convention and are hazardous compounds both for the environment and public health. The aim of this study was to determine the level of environmental pollution of PCBs in the Perm, in soil and biota (European pied flycatcher), and to analyze whether its presence was the cause of cancer and congenital malformations in the population. Soils in the study area had PCB concentrations of 101.87 µg/kg in the Industrialniy District and 27.81 µg/kg in the Leninskiy District of the Perm in 2005. The chemical composition of the individual PCBs and PCB groups were the same in the soils of both regions. The blood of nestlings of the European pied flycatcher raised in the Industrialniy District contained 9.61 ng PCB/ml, while those in the Leninskiy District had 5.64 ng PCB/ml in 2005. A linear correlation was established between the PCB contamination of soils and PCB contamination of pied flycatcher nestling's blood, and inverse linear correlation was established between the content of PCB in the blood of nestlings and the success of breeding of the pied flycatcher in Perm. An epidemiological analysis revealed a high incidence of cancer among the human population of the Industrialniy and Leninskiy districts (371.7 and 376.85 cases per 100,000 population, mean for the 2003-2018, respectively), which exceeded the figure for the whole of Perm (350.77 cases per 100,000 population, mean for the 2003-2018). The incidence rate of congenital malformations in Perm for the study period was 48.51 per 1000 human births. However, a decrease in the concentration of PCBs in soil and biota over a 15-year period (2005-2019) to the less than the detection limit did not lead to a decrease in the incidence of these diseases. Probably, PCB contamination was not the main cause of oncological diseases and congenital malformations in the population of the study area.

Markers of polychlorinated biphenyl (PCB) degradation in highly contaminated soil of Central Russia

The highly polychlorinated biphenyl (PCB)-contaminated historical soil is located in the Serpukhov region (Central Russia). This study evaluates the processes of PCB degradation in the soil under natural conditions. Compositions of industrial mixtures (Sovol, Sovtol, and trichlorodiphenyl) were compared with PCB-contaminated soil from different depths. An increased number of dichlorobiphenyls (6 congeners) were determined in the deeper soil horizons (40-60 cm) in comparison with the surface layer (1 congener). Non-associated with industrial mixture congener, PCB 11 was determined in some soil layers with concentrations reaching 3.6 mg/kg. PCB 11 can be considered as a potential marker of activated degradation processes in highly contaminated soils with industrial mixtures. Aegopodium podagraria reduced total PCB concentrations in the contaminated soil to 25% during pot experiments. Prospective precursors of PCB 11 were significantly depleted (62-88%) after phytoremediation, but this did not increase PCB 11 concentration in the soil.