Contamination characteristics of polychlorinated naphthalenes in the agricultural soil of two industrial cities in South Korea

Assessment of polychlorinated naphthalenes in Korean foods: Levels, profiles, and dietary intake

Concerns about dioxin-like compounds have increased; however, the monitoring of polychlorinated naphthalenes (PCNs) in food and the assessment of dietary intake remain limited. In this study, various foods were collected from Korean markets and analyzed for PCNs. Fishery products exhibited the highest mean concentration (48.0 pg/g ww) and toxic equivalent (TEQ) (0.0185 pg-TEQ/g ww). Agricultural products were the largest contributors (35.7%) to the total dietary intake of PCNTEQ, followed by livestock products (33.6%), fishery products (20.2%), and processed foods (10.5%). The mean intake of PCNTEQ for the Korean population was 0.901 pg-TEQ/day for males and 0.601 pg-TEQ/day for females. Generally, males and younger groups had higher daily intakes of PCNTEQ, but they did not exceed the tolerable weekly intakes. Nonetheless, it is important to manage potential health risks associated with PCNs and other dioxin-like compounds by identifying major food items contributing to PCN exposure and considering age and gender differences.

Characteristics and degradation mechanisms of polychlorinated naphthalenes in surface soil in Yangtze River Delta, China

Both thermal and environmental processes are significant factors influencing the existing characteristics, e.g., congener distributions, and existing levels, of polychlorinated naphthalenes (PCNs) in the environment. Soil plays an important role in the life cycle of PCNs, but degradation of PCNs in soils has never been reported. In this study, we collected surface soil samples from 13 cities in the Yangtze River Delta, which is one of the most crowded areas of China and analyzed the samples for 75 PCNs. The long-range transportation from polluted areas was the major source for PCNs in remote areas, but the PCN profiles in remote areas reported in our previous studies were different from those in human settlement in this study, indicating there is a transformation of PCNs after emissions from anthropogenic activities. Two experiments were then designed to reveal the degradation mechanisms, including influencing factors, products, and pathways, of PCNs in surface soils. Based on the experiments, we found that the major factor driving the losses of PCNs in surface soils was volatilization, followed by photo irradiation and microbial metabolism. Under photo-irradiation, the PCN structures would be destroyed through a process of dechlorination followed by oxidation. In addition, the dechlorination pathways of PCNs have been established and found to be significantly influenced by the structure-related parameters.

Distributions of PCDD/Fs, PCBs, and PCNs in coastal sediments collected from major industrial bays in South Korea

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs) were assessed in coastal sediments from industrial bays in South Korea to evaluate the pollution levels and their environmental impact. The mean sediment concentrations of Σ17 PCDD/Fs, Σ18 PCBs, and Σ15 PCNs were 198 ± 140, 3427 ± 7037, and 85 ± 336 pg/g dw, respectively. Generally, pollutant concentrations in the inner bay were higher than those in the outer bay, indicating the influence of industrial emissions and harbor activities. The primary sources were identified as steel manufacturing and wastewater treatment plants for PCDD/Fs, harbor and shipbuilding activities for PCBs, and combustion-related sources for PCNs. Notably, PCDD/F concentrations exceeded sediment guideline values. The combined effects of PCDD/Fs and PCBs demonstrated adverse impacts on aquatic organisms. Hence, the release of toxic pollutants into the marine environment could have potential biological effects due to the combined impact of these various compounds.

Spatial and temporal trends in polychlorinated naphthalenes in sediment from Ulsan and Onsan Bays of Korea: Potential sources and ecotoxicological concerns

Few studies have been conducted on spatial and temporal trends in polychlorinated naphthalenes (PCNs) in coastal environments. Here, we describe 18 PCN congeners found in surface and dated sediment samples collected from highly industrialized bays of Korea. Measurable levels of PCN congeners were detected in all sediment samples, suggesting concurrent and historical contamination. The highest PCN concentrations were observed in sediment from rivers, streams, and the inner portions of the bays, which are surrounded by industrial complexes and commercial harbors. CNs 73, 66/67, and 52 were dominant in surface and dated sediment samples. Congener patterns and diagnostic ratios revealed that PCN contamination is originated from combustion processes and the use of polychlorinated biphenyl (PCB) technical mixtures. PCN concentrations in dated sediment increased from the 1980s to the mid-2000s and then decreased to 2015. Although the toxic equivalent (TEQ) levels of PCNs in our study did not exceed sediment quality guidelines proposed by international authorities, the cumulative risks from the TEQ concentrations of polychlorinated dibenzo-p-dioxins, furans, PCBs, and PCNs can be expected for benthic organisms.

Pilot study on the effect of secondary copper smelters on polychlorinated naphthalene contamination in surrounding agricultural areas

Polychlorinated naphthalenes (PCNs) are dioxin-like persistent organic pollutants that are primarily produced unintentionally during industrial thermal processes. These compounds are harmful to the environment and human health. This study investigated the occurrences of all 75 PCN congeners in agricultural areas near secondary copper smelters in China. The PCN concentrations in aquatic foods, eggs, crops, sediments and soils within 10 km of these smelters were higher than those in samples collected 20-30 km away from such facilities. In contrast, the PCN concentrations in compound animal feed samples collected at different distances from the secondary copper smelters were comparable to one another. Similar PCN homologue patterns were found in crop, egg, feed and soil samples collected at different distances from the smelters but the homologue profiles of PCNs in aquatic food and sediment samples collected from different distances varied. Lower chlorinated naphthalenes were the predominant homologues in most samples. The contamination of farm animals and crops with PCNs might result from the emission of these compounds from such sources into the surrounding environment. However, the health risks associated with human exposure to PCNs through food consumption are low for both distances (<10 km and 20-30 km) from secondary copper smelters.

Occurrence of polychlorinated naphthalenes in dairy cow farms in proximity to an iron smelting plant in China: A preliminary study

Animal derived foods are the primary pathway for human exposure to polychlorinated naphthalenes (PCNs), and various foodstuffs have been reported to contain PCNs. However, information on how PCN emission sources affect surrounding animal farms is scarce. The present study determined PCN levels in cow's milk, excrement, feed, plant and soil samples collected from four dairy farms situated within 10 km of an iron smelting plant in China. PCN concentrations in the milk samples from all four farms were in the range from 470 to 797 pg/g lipid weight while the PCN concentrations in the other specimens decreased in the order: plant > soil > excrement > feed. Higher PCN concentrations appeared in silage than in other feedstuffs, and the relationships between PCNs in milk, excrement and feed were closer than those in plant and soil. Human exposure risk to PCNs by consuming milk from this region was relatively higher than in less polluted areas.

PCNs, PCBs, and PCDD/Fs in Soil around a Cement Kiln Co-Processing Municipal Wastes in Northwestern China: Levels, Distribution, and Potential Human Health Risks

To evaluate the impact of the first cement kiln co-processing municipal wastes in northwest China on the surrounding environment, the concentrations of polychlorinated naphthalenes (PCNs), polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in 17 soil samples collected around the plant. The concentration ranges of PCNs, PCBs, and PCDD/Fs were 132-1288, 10.8-59.5, and 2.50-5.95 pg/g, and the ranges of toxic equivalents (TEQ) were 1.98-20.8, 2.36-48.0, and 73.2-418 fg/g, respectively. The concentrations of PCNs, PCBs, and PCDD/Fs in this study were generally lower than those in soil around municipal waste incinerators and industrial parks in other areas. An exponential function equation was applied for the relationship between the concentration of the target compounds and the distance from the cement kiln stack, the results showed that PCN and PCB concentrations declined with the increasing of distance from the stack. Furthermore, it was found that the effect of the cement kiln on surrounding soil contaminations with PCNs and PCBs was stronger than that of PCDD/Fs by comparing the PCN, PCB, and PCDD/F homologue profiles in the fly ash sample from the plant and soil samples at different distances. The total carcinogenic risks (CR) of PCNs, PCBs, and PCDD/Fs for children and adults in soil were 1.65 × 10^-8-8.93 × 10^-8 and 1.70 × 10^-8-9.16 × 10^-8, respectively, which was less than the risk threshold (CR = 1 × 10^-6), and there was no health risk.

Soil microbiomes divergently respond to heavy metals and polycyclic aromatic hydrocarbons in contaminated industrial sites

Contaminated sites from electronic waste (e-waste) dismantling and coking plants feature high concentrations of heavy metals (HMs) and/or polycyclic aromatic hydrocarbons (PAHs) in soil. Mixed contamination (HMs + PAHs) hinders land reclamation and affects the microbial diversity and function of soil microbiomes. In this study, we analyzed HM and PAH contamination from an e-waste dismantling plant and a coking plant and evaluated the influences of HM and PAH contamination on soil microbiomes. It was noticed that HMs and PAHs were found in all sites, although the major contaminants of the e-waste dismantling plant site were HMs (such as Cu at 5,947.58 ± 433.44 mg kg^-1, Zn at 4,961.38 ± 436.51 mg kg^-1, and Mn at 2,379.07 ± 227.46 mg kg^-1), and the major contaminants of the coking plant site were PAHs (such as fluorene at 11,740.06 ± 620.1 mg kg^-1, acenaphthylene at 211.69 ± 7.04 mg kg^-1, and pyrene at 183.14 ± 18.89 mg kg^-1). The microbiomes (diversity and abundance) of all sites were determined via high-throughput sequencing of 16S rRNA genes, and redundancy analysis was conducted to investigate the relations between soil microbiomes and contaminants. The results showed that the microbiomes of the contaminated sites divergently responded to HMs and PAHs. The abundances of the bacterial genera Sulfuritalea, Pseudomonas, and Sphingobium were positively related to PAHs, while the abundances of the bacterial genera Bryobacter, Nitrospira, and Steroidobacter were positively related to HMs. This study promotes an understanding of how soil microbiomes respond to single and mixed contamination with HMs and PAHs.

Insights into the Formation and Profile of Chlorinated Polycyclic Aromatic Hydrocarbons during Chlorobenzene and Chloroethylene Manufacturing Processes

Chlorinated polycyclic aromatic hydrocarbons including chlorinated naphthalenes and congeners with three to five rings are ubiquitous atmospheric pollutants. Congener profiles and formation mechanisms from typical chemical manufacturing have not been researched extensively. We measured the concentrations of 75 chlorinated naphthalenes and 18 chlorinated polycyclic aromatic hydrocarbons in raw materials, intermediates, products, and bottom residues from chemical plants producing monochlorobenzene and chloroethylene by different techniques. The findings confirmed that these chemical manufacturing processes are newly identified sources of atmospheric emissions of these compounds. More-chlorinated naphthalenes were formed from chloroethylene production than from monochlorobenzene production, which could be explained by the higher temperatures in the former process. Successive chlorination appeared to be an important formation pathway of polychlorinated naphthalenes according to their congener profiles and was supported by quantum chemical calculations of electrophilic chlorination on various positions of naphthalene. Chlorinated polycyclic aromatic hydrocarbons were more likely to be formed during the production of monochlorobenzene than chloroethylene. Moreover, we suggested that ring rearrangement and ring coupling are important transformation reactions between polychlorinated naphthalenes and chlorinated polycyclic aromatic hydrocarbons.