Spatio-Temporal Distribution and Influencing Factors of Human and Veterinary Pharmaceuticals in the Tributary Surface Waters of the Han River Watershed, South Korea.

Human and veterinary pharmaceuticals are being increasingly used for disease treatment; hence, their distribution and factors influencing them in the aquatic environment need to be investigated. This study observed the effect of human and animal populations, usage, purchasing criteria (prescription vs. non-prescription), and land use to identify the spatio-temporal distribution of eight pharmaceuticals at twenty-four sites of the tributaries of the Han River watershed. In rural areas, the mean concentration (detection frequency) of non-prescription pharmaceuticals (NPPs) was higher (lower) compared to that of prescription pharmaceuticals (PPs); in urban areas, a reverse trend was observed. Pharmaceutical concentrations in urban and rural areas were mainly affected by wastewater treatment plants (WWTPs) and non-point sources, respectively; concentrations were higher downstream (4.9 times) than upstream of the WWTPs. The concentration distribution (according to the target) was as follows: human-veterinary > human > veterinary. Correlation between total concentration and total usage of the pharmaceuticals was high, except for NPPs. Most livestock and land use (except cropland) were significantly positively correlated with pharmaceutical concentrations. Concentrations were mainly higher (1.5 times) during cold seasons than during warm seasons. The results of this study can assist policymakers in managing pharmaceutical pollutants while prioritizing emerging pollutants.

Influence of Zooplankton and Environmental Factors on Clear-Water Phase in Lake Paldang, South Korea.

Lake Paldang is a complex water system with both fluvial and lacustrine characteristics and the largest artificial dam lake in South Korea. In this study, the different occurrence patterns and causes of the clear-water phase (CWP) were investigated using water quality and hydrological factors at four sites in Lake Paldang. Among the environmental and other factors associated with CWP occurrence, secchi depth and turbidity exhibited significant correlations with precipitation, hydraulic retention time (HRT), and individual and relative abundance (RA) of zooplankton (Cladocera) (p < 0.01). Hence, a change in the HRT because of precipitation could alter the CWP. The Cladocera individuals and RA showed significant correlations with the water temperature, indicating that the emergence of Cladocera in spring as the water temperature rises could cause the CWP. Sensitivity assessments conducted using Bayesian models demonstrated different CWP occurrence sensitivity relationships for the river-type, lake-type, and shallow and deep sites. Turbidity, secchi depth, and zooplankton factors also showed sensitive relationships with CWP occurrence for all sites. The sensitivity to precipitation and HRT was higher in the river-type sites. The lake-type sites, with common Cladocera emergence and long HRT, favored CWP occurrence. Thus, CWP occurrence was dependent on the site characteristics and climate conditions.

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.

Pharmaceutical compounds in tributaries of the Han River watershed, South Korea.

The Han River watershed is the largest and most important source of drinking water for the residents of the Seoul metropolitan area and the Gyeonggi province in South Korea. The tributaries of the watershed are vulnerable to contamination by effluents from nearby wastewater treatment plants (WWTPs) and non-point sources. In this study, a one-year monitoring study was performed to investigate the occurrence of 13 pharmaceuticals in 24 tributaries of the Han River watershed in October 2015. From the 13 pharmaceuticals, 12 were found in at least one sample, with the exception of chlortetracycline, which was not detected. The three most frequently detected compounds were clarithromycin (95.8%), carbamazepine (66.7%), and lincomycin (62.5%). Compounds found in high concentrations included clarithromycin (5.2675 µg L-1), ibuprofen (1.9646 µg L-1), and carbamazepine (1.1009 µg L-1). The total concentration of 12 pharmaceuticals in the Seoul metropolitan area (0.7128 µg L-1) was higher than that in the Gyeonggi area (0.3177 µg L-1) possibly due to the large-scale WWTPs located upstream. However, in IHR-3, which is located at the very upstream of the tributary and is not impacted by a WWTP, pharmaceuticals were not detected. This can be explained by the fact that most pharmaceuticals derived from WWTPs are related to human activity. The risk quotients (RQs) for the target pharmaceuticals were calculated on the basis of their presence in tributaries, and all pharmaceuticals presented RQs < 0.01, indicating that potential environmental impacts should be low. These results will be useful to monitor and assess the potential environmental risks of pharmaceuticals in the surface water.

Development of freshwater sediment management standards for organic matters, nutrients, and metals in Korea.

Korean water quality managers are required to promptly develop national assessment standards for freshwater sediment quality due to the Four Major River Restoration Project in Korea in 2009. We conducted this study to develop sediment management standards (SMSs), determining obviously and severely polluted sediment, which could have adverse impacts on water quality and aquatic ecosystem. The SMSs values were derived from the 95th percentile of concentration distribution for organic matter and nutrients in sediment quality database. For the SMSs of metals, foreign sediment quality guidelines (SQGs) were adopted. As a result, 13% for loss on ignition (LOI), 1,600 mg/kg for total phosphorus (TP), and 5,600 mg/kg for total nitrogen (TN) were set as the SMSs for freshwater sediment in Korea. These values were higher than the range of heavily polluted sediment from USEPA Region 5 guideline derived by the similar approaches for the Great Lakes harbor sediments, and similar or lower than the severe effect level (SEL) from provincial sediment quality guideline (PSQG) of Ontario, Canada by screening level concentration (SLC) approach. However, SMSs in the present study are appropriate considering the concentration ranges and the Korean SMSs' definition for freshwater sediments in Korea. The Puget Sound marine sediment cleanup screening level (CSL) in Washington State, USA were adopted as the Korean SMSs for As (93 mg/kg), Cd (6.7 mg/kg), Cr (270 mg/kg), Cu (390 mg/kg), Pb (530 mg/kg), and Zn (960 mg/kg) in freshwater sediments. Hg concentration (0.59 mg/kg) of CSL was too low to determine the polluted freshwater sediments in Korea, and the SEL of Ontario, Canada for mercury concentration (2 mg/kg) was selected as the SMS for Hg. These values were found reasonable through the assessment of applicability with the datasets from locations directly affected by obvious point sources. These results indicate that SMSs for organic matter, nutrient, and metals derived within the present study can successfully determine obviously and severely polluted sediment in Korea. However, the SMSs have limits to specifically determine the effects of polluted sediment on water quality and aquatic ecosystem in Korea. Thus, we will revise and specify SMSs considering those effects and further sediment quality assessment framework in the near future.

Effect of a seasonal diffuse pollution migration on natural organic matter behavior in a stratified dam reservoir.

This article aims to describe the influence of diffuse pollution on the temporal and spatial characteristics of natural organic matter (NOM) in a stratified dam reservoir, the Daecheong Dam, on the basis of intensive observation results and the dynamic water quality simulation using CE-QUAL-W2. Turbidity is regarded as a comprehensive representation of allochothonous organic matter from diffuse sources in storm season because the turbidity concentration showed reasonable significance in a statistical correlation with the UV absorbance at 254 nm and total phosphorus. CE-QUAL-W2 simulation results showed good consistency with the observed data in terms of dissolved organic matter (DOM) including refractory dissolved organic carbon (RDOC) and labile DOC and also well explained the internal movement of constituents and stratification phenomenon in the reservoir. Instead turbidity and NOM were related well in the upper region of the reservoir according to flow distance, gradually as changing to dissolved form of organic matter, RDOM affected organic matter concentration of reservoir water quality compared to turbidity. To control the increase of soluble organic matters in the dam reservoir, appropriate dam water discharge gate operation provided effective measurement. Because of the gate operation let avoid the accumulation of organic matter within a dam reservoir by shorten of turbid regime retention time.