The effects of heavy rain on the fate of urban and agricultural pollutants in the riverside area around weirs using multi-isotope, microbial data and numerical simulation.

The increase in extreme heavy rain due to climate change is a critical factor in the fate of urban and agricultural pollutants in aquatic system. Nutrients, including NO3- and PO43-, are transported with surface and seepage waters into rivers, lakes and aquifers and can eventually lead to algal blooms. δ15N-NO3-, δ18O-NO3-, and δ11B combined with hydrogeochemical and microbial data for groundwater and surface water samples were interpreted to evaluate the fate of nutrients in a riverside area around weirs in Daegu, South Korea. Most of the ions showed similar concentrations in the groundwater samples before and after heavy rain while concentrations of major ions in surface water samples were diluted after heavy rain. However, Si, PO43-, Zn, Ce, La, Pb, Cu and a number of waterborne pathogens increased in surface water after heavy rain. The interpretation of δ11B, δ15N-NO3-, and δ18O-NO3- values using a Bayesian mixing model revealed that sewage and synthetic fertilizers were the main sources of contaminants in the groundwater and surface water samples. δ18O and SiO2 interpreted using the Bayesian mixing model indicated that the groundwater component in the surface water increased from 4.4 % to 17.9 % during the wet season. This is consistent with numerical simulation results indicating that the direct surface runoff and the groundwater baseflow contributions to the river system had also increased 6.4 times during the wet season. The increase in proteobacteria and decrease of actinobacteria in the surface water samples after heavy rain were also consistent with an increase of surface runoff and an increased groundwater component in the surface water. This study suggests that source apportionment based on chemical and multi-isotope data combined with numerical modeling approaches can be useful for identifying main hydrological and geochemical processes in riverside areas around weirs and can inform suggestions of effective methods for water quality management.

Maternal, infant, and perinatal mortality statistics and trends in Korea between 2009 and 2017.

OBJECTIVE: To provide updates on maternal, infant, and perinatal mortality using the national population data of South Korea between 2009 and 2017 and describe the mortality rate by target groups, timing, or causes of events to provide a basis for detecting vulnerable populations and ensuring timely medical and political interventions. METHODS: Pregnancy-related mortality in women, as well as deaths of infants, in South Korea was identified using population data from Statistics Korea. Records from death certificates, cremation reports on infant and fetal deaths, and the complementary cause-of-death investigation system were reviewed for the 2009-2017 period. RESULTS: A total of 461 maternal deaths, 11,717 infant deaths, and 12,249 perinatal deaths, including fetal deaths over 28 gestational weeks, were identified from 3,945,159 live births between 2009 and 2017. The maternal mortality ratio was 13.5 deaths per 100,000 live births in 2009 and decreased to 7.8 in 2017. Only the rate of deaths related to hypertensive disorders showed an increasing tendency. Both the infant and perinatal mortality rates improved (from 3.2 deaths per 1,000 live births in 2009 to 2.8 in 2017 and from 3.5 to 2.7, respectively). Among the external causes of infant mortality, assaults including homicides accounted for 25% (n=150), and this proportion was constant throughout the study period. CONCLUSION: Overall improvements were observed in all maternal, infant, and perinatal mortality measures. In-depth analysis and interventions with respect to certain causes, such as hypertensive disorders in mothers or assaults in infants, should be considered priority issues.

Relations of As concentrations among groundwater, soil, and bedrock in Chungnam, Korea: implications for As mobilization in groundwater according to the As-hosting mineral change.

Arsenic (As) concentrations and As-bearing minerals in bedrock and soil, and their relations with groundwater concentrations were investigated in a small agricultural area of Korea. The As concentration of the bedrock shows a wide variation (<0.5-3990 mg/kg) and is well correlated with that in the contacting groundwaters (23-178 µg/L). Soils, the weathering product of bedrock, show the lower and more dispersed As concentrations (8.8-387 mg/kg) than the bedrock. But the soil As concentrations are very high relative to those reported from other areas. The As concentrations in the shallow groundwaters are comparatively low (<20 µg/L) and are independent of the soil concentration. Arsenopyrite is the major As-bearing mineral in the bedrock and its oxidation controls the As levels in deep groundwater. In contrast, As mostly resides in soil as Fe-(hydr)oxide-bound forms. Due to low pH and oxidizing redox condition, the release of As from Fe-(hydr)oxides is largely suppressed, and the shallow groundwater shows low As concentrations generally satisfying the drinking water limit. However, it is suggested that the disturbance of soil geochemical conditions by land use changes would cause a serious As contamination of the shallow groundwaters.