Characteristics, Possible Origins, and Health Risk Assessment of Trace Elements in Surface Waters of the Han River Watershed, South Korea.

To safeguard aquatic environments in and around the Han River watershed in South Korea, a multivariate statistical evaluation of trace elements, a trace element concentration analysis and source determination, and a human health risk assessment were conducted on 10 trace elements at 25 sites. The results demonstrated that the Han River watershed was mainly affected by anthropogenic activities (traffic/industrial activity). The range of concentrations was arranged in descending order: Fe (217.13 ± 301.03 µg/L) > Mn (102.36 ± 153.04 µg/L) > Zn (23.33 ± 79.63 µg/L) > Ba (29.05 ± 12.37 µg/L) > Ni (5.14 ± 11.57 µg/L) > Cu (3.80 ± 3.56 µg/L) > Pb (0.46 ± 0.52 µg/L) > Se (0.06 ± 0.04 µg/L) > Cd (0.01 ± 0.01 µg/L) > Ag (0.004 ± 0.013 µg/L). The hazard index values of trace elements in surface water for combined pathways (ingestion and dermal contact) were < 1.0 for both adults and children, indicating no possible human health hazards. The estimated total cancer risk did not exceed the acceptable limit (1 × 10-4) for adults and children. The findings of this study provide data-driven guidelines for water environment policy decisions in the study area.

Occurrence, Potential Sources, and Risk Assessment of Volatile Organic Compounds in the Han River Basin, South Korea.

Increasing public awareness about the aesthetics and safety of water sources has shifted researchers' attention to the adverse effects of volatile organic compounds (VOCs) on humans and aquatic organisms. A total of 17 VOCs, including 10 volatile halogenated hydrocarbons and seven volatile non-halogenated hydrocarbons, were investigated at 36 sites of the Han River Basin, which is the largest and most important drinking water source for residents of the Seoul metropolitan area and Gyeonggi province in South Korea. The VOC concentrations ranged from below detection limits to 1.813 µg L-1. The most frequently detected VOC was 1,2-dichloropropane, with a detection frequency of 80.56%, as it is used as a soil fumigant, chemical intermediate, and industrial solvent. In terms of geographical trends, the sampling sites that were under the influence of sewage and industrial wastewater treatment plants were more polluted with VOCs than other areas. This observation was also supported by the results of the principal component analysis. In the present study, the detected concentrations of VOCs were much lower than that of the predicted no-effect concentrations, suggesting low ecological risk in the Han River. However, a lack of available ecotoxicity data and limited comparable studies warrants further studies on these compounds.

Temporal-spatial variation and environmental risk assessment of pharmaceuticals in tributaries of the Han River watershed, South Korea.

Eight compounds from three categories of pharmaceuticals [5 antibiotics, 2 non-steroidal anti-inflammatory drugs, and 1 anti-epileptics] were monitored at 24 sites in the tributaries of the Han River watershed in South Korea, 2016. The seasonal occurrence, temporal-spatial variation, potential compound source(s), and a risk assessment of this watershed, which is the largest drinking water source in the country, were investigated. Clarithromycin was detected most frequently (72.2%) with the greatest median concentration (0.151 ± 0.072 µg L-1), followed by carbamazepine and sulfamethoxazole. The seasonality of the pharmaceuticals was observed, with higher concentrations and detection frequencies in spring than in summer and autumn; this was possibly caused by lower levels of microbial activities associated with lower water temperatures than other seasons. In terms of geographical variation, urban areas had higher pharmaceutical concentrations than rural areas, which was attributed to the former's high population density and largest wastewater treatment plants (WWTPs) regardless of season. The total concentration and detection frequency of WWTPs were 12.4 and 2.5 times higher in downstream sites than upstream sites, thereby conveying that WWTPs were the main source for the presence of pharmaceuticals in tributaries. According to the results produced from calculations of the risk quotient (RQ) of aquatic organisms, clarithromycin and sulfamethazine were identified as posing relatively high ecological risk (RQ > 1) during the spring that was identified for this study. This study can provide policymakers with scientific support for prioritizing pollutant management and collections of global data on emerging pollutants.