Chemosphere最新文献

The production and use of polychlorinated naphthalenes (PCNs) were banned several decades ago, but they continue to be detected due to their persistence in surface environments and ongoing emissions from combustion-related sources. This study presents the first nationwide monitoring data for PCNs in soils collected from 61 sites across South Korea. Industrial sites (mean: 127 pg/g, median: 91.4 pg/g) exhibited higher concentrations of Σ₆₃ PCNs than urban (mean: 53.1 pg/g, median: 50.0 pg/g) and suburban (mean: 52.2 pg/g, median: 23.3 pg/g) sites. Tri- and tetra-CNs were the dominant homologues, with CN-14/24 being the most abundant congeners. The majority of PCN contamination at these sites was attributed to combustion sources and historical emissions from Halowax mixtures. Σ₆₃ PCNs and toxic equivalencies (TEQs) were moderately correlated with the number of companies potentially emitting PCNs, industrial electricity usage, and SO₂ concentrations, indicating a significant influence of anthropogenic sources on PCN contamination. The 95th percentile cancer risks for both adults and children across all sites were within the acceptable range (<10^-6) set by the US EPA. However, the higher risks observed for children underscore the importance of ongoing PCN monitoring. This study provides valuable insights into the spatial distribution and human exposure to PCNs in soils across South Korea. Based on these initial nationwide findings, comprehensive monitoring of PCNs and other dioxin-like compounds in industrial areas is recommended.

In the present work, a reduced graphene oxide (rGO) modified-Fe₃O₄ doped bifunctional carbon felt cathode (rGO-Fe₃O₄/CF) that is capable of generating and converting H₂O₂ into hydroxyl radicals (^•OH) on-site was fabricated, thus removing the need for an external catalyst. In addition, an rGO-modified cathode (rGO/CF) with high H₂O₂ production efficiency and a heterogeneous Fenton catalyst (CNT-Fe₃O₄) with magnetic properties were fabricated. The study examined the degradation and mineralization of the cytostatic drug cytarabine (CYT) using two HEF configurations: (i) a bifunctional cathode rGO-Fe₃O₄/CF and (ii) a combination of the rGO/CF cathode with CNT-Fe₃O₄ catalyst. The effects of parameters such as catalyst concentration, initial pH, and applied current were studied. HPLC and ion chromatography analyses were used to identify carboxylic acids and inorganic end-products, respectively. The results show that 0.1 mM CYT was completely degraded within 18 min at an applied current of 300 mA in the HEF system with the rGO-Fe₃O₄/CF bifunctional cathode. Total organic carbon (TOC) analysis revealed that the bifunctional cathode system achieved 98.2% mineralization of CYT after 4 h of treatment at 300 mA. Using the rGO/CF cathode and CNT-Fe₃O₄ catalyst cell, total degradation of 0.1 mM CYT occurred within 7 min, and nearly total mineralization (97.3% TOC removal) was achieved at 300 mA after 4 h.

Companion dogs are exposed to various chemicals. However, our understanding of the sources and pathways of chemical exposure in pets remains limited. In this study, we collected urine samples from 47 dogs and corresponding samples of the food they consumed to analyze the concentrations and dietary exposure to organophosphate flame retardants (OPFRs) and their metabolites (mOPFRs). Triphenyl phosphate (TPHP) and its metabolite, diphenyl phosphate (DHPH), were the predominant compounds detected in dog food and urine samples. The concentration of mOPFRs in urine decreased as body weight increased; however, neither sex nor age significantly influenced mOPFR levels in dog urine. The estimated daily intake of OPFRs (343 ng/kg bw/day) through food consumption (EDI_food) was comparable to the previously reported levels of polycyclic aromatic hydrocarbons (324 ng/kg bw/day) and higher than those of pesticides (214 ng/kg bw/day), parabens (120 ng/kg bw/day), and polychlorinated biphenyls (103 ng/kg bw/day). By calculating the ratio of EDI_food to the cumulative daily intake based on urinary mOPFR concentrations, it was found that dietary sources contributed to 66% of the total TPHP exposure in dogs. This finding was further supported by Spearman's correlation analysis between parent OPFR concentrations in dog food and mOPFR levels in urine (p < 0.01), indicating that dietary intake may be one of the most significant exposure pathways for OPFRs in dogs. To the best of our knowledge, this is the first study to investigate the levels of OPFR exposure in paired dog food and urine samples.

Pine needle, pine bark, and soil samples were collected from various regions in South Korea, considering the suitability of vegetation samples as passive samplers. A total of 27 organochlorine pesticides (OCPs) were analyzed using a gas chromatograph/high-resolution mass spectrometer (GC/HRMS). The total concentrations of OCPs ranged between 650 and 3652 pg/g dw in soil, 215 and 1384 pg/g ww in pine needles, and 456 and 1723 pg/g ww in pine bark. Metabolites such as endosulfan sulfate, p,p'-DDE, and p,p'-DDD were dominant in the soil samples, whereas parent compounds were more prevalent in the pine needles. Diagnostic ratios and compositional profiles suggested that potential OCP sources were primarily related to historical use, atmospheric transport, and unintentional byproducts. OCPs that were never used or registered in South Korea were also detected in all sample types, indicating atmospheric transport from source regions. Sites closer to North Korea and China showed higher concentrations of OCPs, with levels gradually decreasing from west to east in the soil, suggesting long-range atmospheric transport from the source regions. Fugacity fractions indicated net volatilization for most compounds, while net deposition was observed for others, suggesting a dynamic equilibrium. This study concludes that atmospheric transport plays a predominant role in the distribution and fate of OCPs in the environment, with no evidence of current local sources.

Activated carbon adsorption is a widely used technology for the removal of per- and polyfluoroalkyl substances (PFAS). However, the rapid breakthrough of PFAS in activated carbon filters poses a challenge to meet the very low allowable PFAS concentrations in drinking water, leading to high operational costs. In this study, we conducted batch isotherm and kinetic adsorption experiments using nine different types of PFAS molecules at concentrations typically found in water sources used for drinking water production (0.1-100 ng/L). The isotherm experiments at these low concentrations reveal that the maximum adsorption capacity of several PFAS is much lower than reported in literature. The estimated isotherms were included in a dynamic model that includes mass transport based on surface diffusion. This model effectively describes the experimental kinetic data, and the obtained surface diffusion coefficients indicate a very slow PFAS surface mobility. Additionally, our findings indicate that PFAS surface mobility decreases in scenarios with more available adsorption sites. Notably, mesoporous activated carbon, with its higher adsorption capacity, exhibits lower PFAS surface mobility than microporous carbon with lower PFAS adsorption capacity. Moreover, for both carbons, we observed a decrease in PFAS surface mobility at higher carbon loadings when the surface is less saturated with PFAS. Our findings suggest potential inherent limitations in activated carbon technology for PFAS removal under environmentally relevant conditions, as we observed lower adsorption capacities than previously reported at higher concentrations, and a decrease in PFAS surface mobility with more available adsorption sites.

Cyanobacterial blooms are prevalent globally and present a significant threat to water security. Titanium salt coagulants have garnered considerable attention due to their superior coagulation properties and the absence of metal residue risks. This paper explored the influencing factors in the coagulation process of titanium xerogel coagulant (TXC), the alterations in cell activity during floc storage, and the release of cyanobacterial organic matters, thereby determining the application scope of TXC for cyanobacterial water treatment. The findings indicated that at a TXC dosage of 8 mg Ti/L, the removal rate of Microcystis aeruginosa (M. aeruginosa) exceeded 86% across a pH range of 5-9. The coagulation performance with anions HCO₃^-, CO₃^2- and H₂PO₄^-/HPO₄^2- was unsatisfactory at concentrations of 10, 20, and 50 mg/L, with corresponding chlorophyll a (Chl-a) levels of 168, 129, and 196 μg/L, respectively. While the presence of Cl^-, NO₃^-, SO₄^2-, K⁺, NH₄⁺, Ca²⁺ and Mg²⁺ had little influence on the removal efficiency. At sodium alginate (SA) concentration of 6 mg/L, the Chl-a content was 116 μg/L, with humic acid (HA) not affecting M. aeruginosa removal but hindering turbidity reduction, leaving a residual turbidity of 11 NTU. Following TXC treatment, a floc storage study with cyanobacteria-laden surface water showed a decrease in microcystins (MCs) content. The low residual titanium concentration post-TXC coagulation (<0.06 mg/L) and MCs reduction contributed to reduced effluent toxicity, indicating TXC's versatile applicability for treating cyanobacterial-contaminated waters.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). .

Following a decline in the production and use of polychlorinated naphthalenes (PCNs) and the restrictions introduced by the Stockholm Convention, dietary intake represents the most significant pathway of human exposure to these dioxin-like contaminants. PCNs occur ubiquitously in foods, originating from the legacy of historical production that is now globally redistributed, as well as from ongoing industrial and domestic combustion sources which have a stronger influence on occurrence patterns in countries where they were not produced. Recent studies have benefited from a wider set of available PCN reference standards, enabling more accurate reporting of a diverse range of congeners. Combining the available information on food occurrence with relative potency (REP) data, an initial selection of twenty PCN congeners are presented here for monitoring of foodstuffs. The selection is expected to provide a good indication of the overall dioxin-like toxic equivalence (TEQ) associated with food occurrence, particularly in industrialised countries and regions where both, historical production and current combustion processes are significant sources. The selection also appears to be representative of the vast majority of PCN TEQ reported in human tissues despite the limited amount of reliable data. Future studies will benefit from the increasing availability of new PCN standards and provide a broader spectrum of occurrence data in foods and human tissues. They will also support toxicological studies on a wider range of congeners and biological effects, enhancing our understanding of PCN-mediated toxicity. Both these information strands will allow refinement and expansion of the proposed selection of congeners, if required.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). .