Kyoung-Woong Kim’s research while affiliated with Gwangju Institute of Science and Technology and other places

The accumulation of heavy metals (i.e., As, Cu, Ni, Pb, and Zn) in soils and native plant species near copper, nickel, and pyrite mines in Vietnam was assessed. The highest soil As, Cu, Ni, Pb, and Zn concentrations recorded in mine soils were 42.3, 1570, 9870, 128, and 462 mg/kg, and those in agricultural soils were 11.4, 453, 94.9, 34.4, and 147 mg/kg, respectively. Pollution index (PI) values indicated heavy pollution (PI = 3.99–13.0) for mine soils, and unpolluted to severely polluted (PI = 0.65–2.84) for agricultural soils. Soil enrichment factors had a wide range, from minimal to extreme enrichment of heavy metals (EF = 0.03–91.4). Arsenic minerals may be the main source of high As concentrations in sulfide mines. The As, Cu, Ni, Pb, and Zn concentrations of 20 native plant species near three mines were in the ranges of 0.05–1150, 3.17–123, 0.47–291, 0.08–6.34, and 6.87–168 mg/kg (dry weight, DW), respectively. Based on the recorded hyperaccumulation levels (1150 mg/kg, DW), bioaccumulation factors (BAF = 2.4–90.0), biomass, and rapid growth, Pteris vittata L. is considered a promising plant for phytoextraction of As in soils. Bidens pilosa L. has potential for phytostabilization of sulfide-bearing soils, given its low concentrations of heavy metals in plant shoots, BAF values of <1, high biomass, and wide distribution. Integrated phytoremediation and phytomanagement are applicable to metal-contaminated soils. Phytomining, energy crops, and vegetation cover should be investigated for the phytomanagement of metal-contaminated soils in mining areas. Graphical Abstract

Groundwater is widely used for domestic purposes, especially as a reliable source of drinking water in rural areas of the Lao People’s Democratic Republic (Lao PDR). This preliminary study aims to examine heavy metal(loid)s contamination leading to human health risks while also focusing on a method that can improve drinking water quality in floodplain areas along the Mekong River in Lao PDR. Groundwater and surface water samples were collected during the monsoon season in 2022 in Attapeu and Champasak provinces. Heavy metal(loid)s concentrations and human health risks were investigated using inductively coupled plasma mass spectrometry (ICP-MS) and the USEPA method, respectively. A nanofiltration membrane technique was introduced to optimize the quality of groundwater. Results showed that groundwater quality was significantly poor (p < 0.05), particularly in Attapeu province, with high levels of electrical conductivity, total dissolved solids, and manganese, exceeding WHO standards of 400 µS cm−1, 300 mg L−1, and 80 µg L−1, respectively. With the groundwater ingestion pathway, children were found to be more vulnerable to non-carcinogenic risk than adults (Hazard Quotient, Hazard Index >1), but adults had a higher carcinogenic risk (Incremental Lifetime Cancer Risk >1E-04). The removal of fecal bacteria and heavy metal(loid)s was achieved using the nanofiltration membrane, demonstrating its potential as a practical point-of-use technology to provide cleaner water sources and enhance the health status of Lao residents.

Elevated levels of arsenic in crop plants have been found in various regions worldwide, especially where agricultural soils have been affected by arsenic-enriched aquifers and human activities including mining, smelting, and pesticide application. Given the highly toxic nature of arsenic, remediation should be carried out immediately to reduce this potentially toxic element transport from soil to crop plants. This study focused on the utilization of biofertilizer which is a combination of arsenic-accumulating microorganisms and adsorbent (carrier) in order to achieve high efficiency of arsenic immobilization and ability to apply in the field. Thirty-two bacterial strains were isolated from 9 soil samples collected from the Dongjin and Duckum mining areas in Korea using a nutrient medium amended with 2 mM sodium arsenite. Among isolates, strain DE12 identified as Bacillus megaterium exhibited the greatest arsenic accumulation capacity (0.236 mg/g dry biomass) and ability to resist up to 18 mM arsenite. Among the three agricultural waste adsorbents studied, rice straw was proved to have a higher adsorption capacity (0.104 mg/g) than rice husk and corn husk. Therefore, rice straw was chosen to be the carrier to form biofertilizer together with strain DE12. Inoculation of biofertilizer in soil showed a reduction of arsenic content in the edible part of lettuce, water spinach, and sweet basil by 17.5%, 34.1%, and 34,1%, respectively compared to the control group. The use of biofertilizer may open up the potential application in the field for other food plants.

The forest distribution in relation to mountain slope position and the relationships between forest canopy area and soil physical and chemical properties in Mongolia attract the attention of scientists. In this study, we aimed to determine (1) how the slope aspect affects the forest soil physical and chemical properties, (2) how the soil variables correlate with projected canopy area. For comparative study, we established a total of 18 (20 � 25 m 2 sized) sample plots in upper forest edge (UFE), upper slope of the forest (USF), lower slope of the forest (LSF), lower forest edge (LFE), sparse forest (SF), and degraded forest area (DFA) stand types with three replications. We measured the tree height, diameter and crown projection area of each growing tree in the sample plots, and collected soil samples for further soil physical and chemical analyses in the laboratory. Our results showed a high variation in growing stock (p < 0.0001), stand density and projected canopy area (p < 0.0001) in relation to mountain slope position and land-use management. We found that the slight changes in stand canopy area projection cause a high variation in soil physical and chemical properties. Among studied stand types higher means of soil temperature and bulk density and lower moisture content were observed on SF and DFA stand types. Contrary, relatively higher content of soil moisture and nutrient elements were recorded in USF, LSF, LFE. We conclude that tree canopy area becomes key determinant factor that positively influences forest soil moisture and fertility by increasing organic matter content in Mongolia.

Arsenic contamination in the Mekong River is a well-known environmental issue yet to be resolved due to its transboundary nature which further limits its access and data collection. Other than that, the key mechanisms that controlling the arsenic release in Mekong sub-region groundwater was heterogeneously distributed and can be varied from region to region. The main purpose of this project is to identify the regional arsenic contamination levels in the hope of helping the government integrate regional groundwater arsenic risk reduction policy in their near future planning. Sampling was conducted during May and August 2022 in Cambodia and Laos, respectively. The findings revealed that the topography of certain areas in Cambodia has exposed significantly high concentrations of arsenic in groundwater compared to those in Laos. About 33% of the sampling sites in Cambodia had shown a high arsenic contamination (> 10 µg/L, WHO guideline) with its concentration ranging from 47.7 ± 0.8 to 696.9 ± 5.6 ppb. The physicochemical properties revealed that the arsenic controlling mechanisms were totally different between both study area. More regional and site-specific arsenic contamination research related to climate change and arsenic hydrology at regional levels should be carried out to ensure the water safety plan in specific regions. Further, we believe that the findings of this study will be beneficial to policy and regional water safety plans for the Mekong River, especially in Cambodia.

One byproduct of brewing beer is Brewer’s spent grain (BSG), which is reused in animal feed. However, BSG has valuable potential for other products such as biochar because of its high protein and fiber content. Radioactive waste is one of the biggest concerns in Korea because of the permanent shutdown of the Gori nuclear power plant. In this study, we aimed to use BSG-850, a biochar originating from BSG after pyrolysis at 850 °C, for the adsorption of cobalt (Co) and strontium (Sr), which are two radionuclides that contribute to radioactive waste. The adsorption capacity of Co and Sr was reinforced with increased temperature which are 3.304, 4.659, 5.516 mg/g (Co) and 1.462, 2.54, 3.036 mg/g (Sr) at 298, 308, and 318 K, respectively. The reusability of BSG-850 capacity was 75.3, 47.8, 43.6, 36.2% and 93.6, 84.2, 57.2, and 32.7% after 1, 2, 3, and 4 cycles, for Co and Sr, respectively. In the presence of other competitive ions, the adsorption capacity decreased. The adsorption capacity and properties of BSG-origin biochar for Co and Sr were confirmed and BSG can be a desirable option for solving radioactive waste issue.

Phosphorus (P) is the second most important nutritional element for plant growth and improves the balance of forest soil ecology. In this study, nutrient elements were comparatively evaluated as phosphorus fractions in soil using sequential extraction using a UV-VIS spectrophotometer from typically degraded Hustai and naturally regenerated Udleg, Batsumber. The objective of this study was to assess the effects of different land-use and slope aspects on soil inorganic phosphorus (Pi) and organic phosphorus (Po) fractions with different availabilities. In this study, labile P decreased with decreasing slope in the Udleg plots, whereas nonlabile P and calcium-bound phosphorus (Ca-P) increased with decreasing slope in the Udleg plots. Furthermore, aluminum-bound phosphorus (Al-P) and Ca-P showed no changes by the slopes in the Hustai plots. The contents of nonlabile Po and moderately labile Po in Hustai and Udleg were higher than those of labile Po. The content of nonlabile Po in Udleg soil was significantly higher (t-test, p < 0.001) than in Hustai, which indicates that humic acid-bound P (humic-P) was derived from plants. A high Ca-P content was recorded at the lower forest edge of Hustai.Low-labile Po was derived from organic residues in Hustai and plant residues in Udleg, which were easily mineralized by soil microbes. The incorporation of organic and plant residues in Hustai and Udleg, respectively, increased soil pH, contributing to P availability for plant uptake. Further studies are needed to determine the nutritional elements in plants, evaluate their relationship with the soil, and evaluate their ecological significance.