Neung-Hwan Oh

Chemical weathering of silicates and carbonates is essential in the global cycles of many elements, including carbon. Chemical weathering affects regional and global carbon budgets through the export of bicarbonate, much of which can originate from the atmosphere. Agricultural practices may accelerate chemical weathering from the Mississippi River basin directly or indirectly. Here we investigated one of the direct effects of agricultural practices, liming, on stream bicarbonate export and the c

Abstract Soil acidification is a very important process in the functioning of earth's ecosystems. A major source of soil acidity is CO 2 , derived from the respiration of plant roots and microbes, which forms carbonic acid in soil waters. Because elevated atmospheric CO 2 often stimulates respiration of soil biota in experiments that test ecosystem effects of elevated atmospheric CO 2 , we hypothesize that rising atmospheric CO 2 (which has increased from ∼200 ppm since the interglacial and may

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

About 10% of the CO2 in the above-ground atmosphere is annually recycled back to the atmosphere from the soil. Soil respiration (the sum of root and microbial respiration) increases soil CO2 concentrations by 10- to 100-fold or more than that in the above-ground atmosphere, and such elevated concentrations have a variety of significant effects on soil systems. Because increased soil respiration is expected to result from future global climates, due both to elevated atmospheric CO2 and temperatur

Abstract The effects of tree species on soil organic carbon (SOC) content have been evaluated in many studies, but only with a relatively small number of sample plots, resulting in ambiguous conclusions. Here we used a total of 595 forest plots in South Korea to investigate the role of four grouped tree species—pines, oaks, other conifers, and other deciduous trees—in the forest SOC content in both forest floors and mineral soils. Significant differences were observed in SOC content among the gr

Abstract. High-frequency continuous measurements of the partial pressure of CO2 (pCO2) are crucial for constraining the spatiotemporal dynamics of CO2 emissions from inland water systems. However, direct measurements of pCO2 are scarce, and no systematic comparisons have been conducted on the suitability of the widely used measurement systems for continuous underway or long-term deployment in various field conditions. We compared spray- and marble-type equilibrators and a membrane-enclosed CO2 s

Abstract A principal driver of biogeochemical weathering of the Earth's crust is soil CO 2 , produced mainly by plant roots and soil heterotrophs, a water‐soluble gas that forms carbonic acid which reacts with soil minerals via cation exchange and mineral dissolution. We examined effects of elevated atmospheric CO 2 (ambient + 200 ppmv) in a young pine forest on belowground carbonic acid chemistry of soil water. Soil water was collected every 2–3 weeks over a 5‐year period from O horizons and at

Tracking the sources of organic carbon (OC) is critical not only for understanding riverine carbon dynamics but also for providing management options to improve water quality. We collected water samples from upland forest streams to the mainstream Geumho River (GHR) of South Korea, which included a variety of wastewater treatment plants (WWTP) effluents. We analyzed the concentrations, optical properties, and dual carbon isotope ratios of these samples to identify the sources of OC. Dissolved or

Abstract Dissolved organic carbon (DOC) in throughfall plays a vital role in providing carbon and energy to organisms in forests. We utilized carbon isotope analysis to allocate the sources of throughfall DOC, including leaching from plant tissues, PM 2.5 deposition on plant foliage, and precipitation. Rainwater, PM 2.5 , and throughfall samples were collected from pine and oak forests between March and November 2021. The mean concentration of throughfall DOC was 7.9 mg L −1 , approximately six