@article {2860,
	title = {High dissolved organic radiocarbon in precipitation during winter and its implication on the carbon cycle},
	journal = {Science of The Total Environment},
	volume = {742},
	year = {2020},
	month = {Jan-11-2020},
	pages = {140246},
	abstract = {Radiocarbon (14C) analysis is a powerful tool for tracing carbon in the global carbon cycle. Precipitation is a component of the global carbon cycle through which dissolved organic carbon (DOC) enters terrestrial and aquatic ecosystems from the atmosphere. In previous studies, the Δ14C of DOC in rain or snow was negative indicating an input of relatively old organic carbon including fossil fuels, with only a few positive values up to +108{\textperthousand} showing the signal of recent photosynthesis. However, here we report surprisingly high Δ14C-DOC in bulk precipitation, more than 1000{\textperthousand} in Seoul, South Korea, especially when the Northwesterly wind blows during winter. In contrast, Δ14C of particulate organic carbon (POC) in bulk precipitation was negative, indicating that the sources of POC and DOC were different. Although the sources of the high Δ14C-DOC are not clear and future studies on them are required, the relatively high Δ14C-DOC in a nearby headwater stream suggests that precipitation DOC has the potential to affect the local carbon cycle, and that stream DOC derived from terrestrial ecosystems could be older than previously thought. The analysis of Δ14C-DOC of precipitation in many other locations is necessary to understand how long carbon stays in terrestrial ecosystems.},
	issn = {00489697},
	doi = {10.1016/j.scitotenv.2020.140246},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0048969720337670},
	author = {Cha, Ji-Yeon and Lee, Seung-Cheol and Lee, Eun-Ju and Go, Minjung and Dasari, Kishore Babu and Yim, Yong-Hyeon and Oh, Neung-Hwan}
}
@article {2859,
	title = {Longitudinal discontinuities in riverine greenhouse gas dynamics generated by dams and urban wastewater},
	journal = {Biogeosciences},
	volume = {15},
	year = {2018},
	month = {Jan-01-2018},
	pages = {6349 - 6369},
	abstract = {Surface water concentrations of CO2, CH4, and N2O have rarely been measured simultaneously in river systems modified by human activities, contributing to large uncertainties in estimating global riverine emissions of greenhouse gases (GHGs). Basin-wide surveys of the three GHGs were combined with a small number of measurements of C isotope ratios in dissolved organic matter (DOM), CO2, and CH4 in the Han River basin, South Korea, to examine how longitudinal patterns of the three gases and DOM are affected by four cascade dams along a middle section of the North Han River (hereafter termed {\textquotedblleft}middle reach{\textquotedblright}) and treated wastewater discharged to the lower Han River ({\textquotedblleft}lower reach{\textquotedblright}) traversing the Seoul metropolitan area. Monthly monitoring and two-season comparison were conducted at 6 and 15 sites, respectively, to measure surface water gas concentrations and ancillary water quality parameters including concentrations of dissolved organic carbon (DOC) and optical properties of DOM. The basin-wide surveys were complemented with a sampling cruise along the lower reach and synoptic samplings along an urban tributary delivering effluents from a large wastewater treatment plant (WWTP) to the lower reach. The levels of pCO2 were relatively low in the middle reach (51{\textendash}2465 {\textmu}atm), particularly at the four dam sites (51{\textendash}761 {\textmu}atm), compared with those found in the largely forested upper basin with scattered patches of croplands (163{\textendash}2539 {\textmu}atm), the lower reach (78{\textendash}11298 {\textmu}atm), and three urban tributaries (2120{\textendash}11970 {\textmu}atm). The upper and middle reaches displayed generally low concentration ranges of CH4 and N2O, with some local peaks influenced by agricultural runoff and impoundments. By comparison, the lower reach exhibited exceptionally high concentrations of CH4 (1.2{\textendash}15766 nmol L-1) and N2O (7.5{\textendash}1396 nmol L-1), which were significantly correlated with different sets of variables such as DO and PO3-4 for CH4 and NH+4 and NO-3 for N2O. Downriver increases in the levels of DOC and optical properties such as fluorescence index (FI) and protein-like fluorescence indicated an increasing DOM fraction of anthropogenic and microbial origin. The concentrations of the three GHGs and DOC were similar in magnitude and temporal variation at a WWTP discharge and the receiving tributary, indicating a disproportionate contribution of the WWTP effluents to the tributary gas and DOC exports to the lower reach. The values of δ13C in surface water CO2 and CH4 measured during the sampling cruise along the lower reach, combined with δ13C and Δ14C in DOM sampled across the basin, implied a strong influence of the wastewater-derived gases and aged DOM delivered by the urban tributaries. The downstream enrichment of 13C in CO2 and CH4 suggested that the spatial distribution of these gases across the eutrophic lower reach may also be constrained by multiple concomitant processes including outgassing, photosynthesis, and CH4 oxidation. The overall results suggest that dams and urban wastewater may create longitudinal discontinuities in riverine metabolic processes leading to large spatial variations in the three GHGs correlating with different combinations of DOM properties and nutrients. Further research is required to evaluate the relative contributions of anthropogenic and in-stream sources of the three gases and DOM in eutrophic urbanized river systems and constrain key factors for the contrasting impoundment effects such as autotrophy-driven decreases in pCO2 and in-lake production of CH4 and N2O.},
	doi = {10.5194/bg-15-6349-2018},
	url = {https://bg.copernicus.org/articles/15/6349/2018/},
	author = {Jin, Hyojin and Yoon, Tae Kyung and Begum, Most Shirina and Lee, Eun-Ju and Oh, Neung-Hwan and Kang, Namgoo and Park, Ji-Hyung}
}
