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Environ Int. 2019 Sep 10;133(Pt A):105126. doi: 10.1016/j.envint.2019.105126. [Epub ahead of print]

Temporal variation in riverine organic carbon concentrations and fluxes in two contrasting estuary systems: Geum and Seomjin, South Korea.

Author information

1
Hanyang University ERICA, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan-si, Gyeonggi-do 15588, South Korea.
2
KOPRI Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 21990, South Korea. Electronic address: jhkim123@kopri.re.kr.
3
Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon 34134, Republic of Korea.
4
Department of Earth and Environmental Sciences, Pukyong National University, Busan 48513, Republic of Korea.
5
Division of Ecosystem Assessment, National Institute of Ecology, Seocheon 33657, Republic of Korea.
6
Hanyang University ERICA, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan-si, Gyeonggi-do 15588, South Korea. Electronic address: shinkh@hanyang.ac.kr.

Abstract

In this study, surface water samples were collected at sites located in the lowest reaches of closed (Geum) (i.e. with an estuary dam at the river mouth) and open (Seomjin) estuary systems between May 2016 and May 2018. We analyzed concentrations and stable isotopes of particulate organic carbon (POC) and dissolved organic carbon (DOC) to assess OC sources, to estimate fluxes of riverine OC, and to assess some of the factors driving OC exports in these two contrasting Korean estuary systems. Our geochemical results suggest that the contribution of the phytoplankton-derived POC to the total POC pool was larger in the Geum River than in the Seomjin River. Notably, a heavy riverine algae bloom occurred in the Geum River in August 2016, resulting in a high carbon isotopic composition (-19.4‰) together with low POC/PN ratio (<10) and POC/Chl-a ratio (<100). In contrast, potential DOC sources in both the Geum River and the Seomjin River were a mixture of C3-derived forest soils and cropland organic matter. During the study period, the catchment area-normalized fluxes of POC and DOC were 0.40 × 10-3 tC/km2/yr and 6.5 × 10-2 tC/km2/yr in the Geum River and 5.2 × 10-4 tC/km2/yr and 8.6 × 10-4 tC/km2/yr in the Seomjin River, respectively. It appears that the POC flux was more weakly associated with the water discharge in the Geum River than in the Seomjin River, but the DOC fluxes were in general controlled by the water discharges in both rivers. Accordingly, the estuary dam of the Geum River might be one of the most strongly influencing factors on seasonal patterns in POC fluxes into the adjacent coastal seas, strongly modifying water residence times and thus biogeochemical processes.

KEYWORDS:

Estuary dam; Geum River; Riverine organic carbon; Seomjin River

PMID:
31518934
DOI:
10.1016/j.envint.2019.105126
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