Hyuck Soo Kim

An integrated approach to safer plant production on metal contaminated soils using species selection and chemical immobilization

In order to examine the species specific accumulation of heavy metals in medicinal crops, seven different common medicinal plants were cultivated on a Cd (55mgkg(-1)) and Pb (1283mgkg(-1)) contaminated soil. Subsequently, the effect of various immobilizing agents, applied in isolation and in combination, on Cd and Pb uptake by two medicinal plant species was examined. Cadmium and Pb root concentrations in medicinal plants grown in the control soil varied between 0.5 and 2.6mgkg(-1) for Cd and 3.2 and 36.4mgkg(-1) for Pb. The highest accumulation occurred in Osterici Radix (Ostericum koreanum) and Ginger (Zingiber officinale) and the lowest in Yam (Dioscorea batatas). Application of immobilizing agents significantly reduced both Cd and Pb concentrations in all medicinal plants examined, where the most effective single immobilizing agent was lime fertilizer (LF). Application of combination treatments involving sorption agents such as compost together with lime further decreased Cd and Pb concentrations from 1.3 and 25.3mgkg(-1) to 0.2 and 4.3mgkg(-1), respectively, which was well below the corresponding WHO guidelines. Thus appropriate immobilizing agents in combination with species selection can be practically used for safer medicinal plant production.

Adsorptive Removal of Trichloroethylene in Water by Crop Residue Biochars Pyrolyzed at Contrasting Temperatures: Continuous Fixed-Bed Experiments

Biochar (BC) has attracted great attention as an alternative sorbent to activated carbon (AC). Objective of this study was to determine trichloroethylene (TCE) removal by soybean stover BC pyrolyzed at 300 (BC300) and 700°C (BC700) in continuous fixed-bed column. Columns packed with BC300, BC700, and AC reached breakthrough time in 1.1, 27.0, and 50.7 h, respectively. BC700 had higher TCE adsorption capacity than BC300 due to its higher surface area, nonpolarity, and aromaticity. The sorption capacities of AC (774.0 mg g−1) and BC700 (515.1 mg g−1) were 21.6 and 14.4 times higher than that of BC300 (35.9 mg g−1). The lower desorption rate of TCE from BC300 than BC700 and AC may be attributed to the strong binding/partition of TCE to the noncarbonized part of BC. Thomas model also adequately described the adsorption data indicating interphase mass transfer. Overall, AC showed best efficiency for removing TCE from water in column experiments. However, although sorption and desorption capabilities of BC700 were a little lower than AC, it is still a good alternative for AC to remove organic contaminants such as TCE from water due to its cost-effectiveness.

Distribution of Cd and Pb Accumulated in Medicinal Plant Roots and Their Cultivation Soils

In general, plant roots accumulate more heavy metals than the above ground organs such as leaf, stem, and fruit. This implies that root medicinal plants would be an issue with excessive heavy metal accumulation. Therefore, the current study was carried out to investigate the distribution of heavy metal (focused on Cd and Pb) concentrations in soils and medicinal plant roots grown in different region of Korea. Total 293 samples for each soil and plant were collected along the national wide. Soil pH, total and phytoavailable metal concentrations (1 M NH₄NO₃ extracted) in soils were determined and heavy metal concentrations in root of the medicinal plants were analyzed. Heavy metal concentrations of the soil samples studied were not exceeded standard limits legislated in ‘Soil Environmental Conservation Act’, except 2 samples for Cu. However, substantial amount of Cd was accumulated in medicinal plant roots with 29% samples exceeding the standard limit legislated in ‘Pharmaceutical Affairs Act’ while all plant samples were lower than the standard limit value for Pb. Also the current study demonstrated that cadmium concentrations in the roots were governed by the phytoavailable Cd in soils, which decreased as soil pH increased. From this result, application of heavy metal immobilization technique using a pH change-induced immobilizing agents can be suggested for safer root medicinal plant production.

A DOC coagulant, gypsum treatment can simultaneously reduce As, Cd and Pb uptake by medicinal plants grown in contaminated soil

The efficiency of gypsum, as a dissolved organic carbon (DOC) coagulator, for the simultaneous immobilization of two heavy metals (Cd and Pb) and one metalloid (As) in agricultural soils near an abandoned mining site was examined. The agricultural soil was defined as long-term contaminated as As (1540mgkg-1), Cd (55mgkg-1) and Pb (1283mgkg-1) concentrations exceeded the Korean guideline values for As (25mgkg-1), Cd (4mgkg-1), and Pb (200mgkg-1). Gypsum was incorporated into the contaminated soil at 3% (w/w). In comparison two commonly using immobilizing agents (lime and compost), together with a mixture (lime+gypsum) were also included in the pot trial for the cultivation of two medical plants (A. gigas and A. macrocephala) and to evaluate the effectiveness of gypsum on As, Cd and Pb immobilization. The results showed that even though pH change-induced immobilizing agents such as lime were more effective than gypsum at immobilizing Cd and Pb, addition of gypsum also effectively reduced heavy metal phytoavailability as indicated by decreases in the concentration of Cd and Pb in medicinal plants. Furthermore, gypsum and gypsum+ lime were also most effective in reducing As concentrations in both plants studied. This was mainly attributed to significant decreases in soil DOC (48-64%) when gypsum and gypsum+lime were applied to the soil. Consequently, it was concluded that enhanced DOC coagulation with gypsum, could be considered as a promising technique for the immobilization of both metals (Cd and Pb) and metalloids (As) in agricultural soils.

Application of Practical Immobilizing Agents for Declining Heavy Metal (loid)s Accumulation by Agricultural Crop (Allium wakegi Araki)

Received: August 7, 2017 Revised: August 25, 2017 Accepted: August 27, 2017 In order to reduce the accumulation of toxic metals (As, Cd and Pb) in the chives, various immobilizing agents such as a soil pH change-inducing immobilizing agent (lime), sorption agent (compost, spent mushroom compost), soil pH change and sorption agent (biochar) and, dissolved organic carbon (DOC) coagulator (gypsum) and uncontaminated soil were applied to the contaminated soils in isolation and in combination. Then chives were grown and determined for As, Cd and Pb concentrations accumulated in the edible part at harvest. The Cd and Pb concentrations of the chive plant grown in the contaminated soil (no treatment) exceeded the legislated Korean guideline values (Cd: 0.05 mg kg-1, Pb 0.1 mg kg-1) and As concentration (21 mg kg-1) was 1,000 times higher than chives plant grown in uncontaminated environment in Korea. Application of lime and gypsum significantly reduced As, Cd and Pb concentrations in all chives examined, due to the increased soil pH and decreased soil DOC. Also, application of combination treatments involving DOC coagulator such as gypsum together with lime decreased As, Cd and Pb concentrations from 21, 1.3 and 9.7 mg kg-1 to 2.1, 0.1 and 1.1 mg kg-1, respectively. Consequently, it was concluded that pH change-inducing immobilizing agent (lime) which was already well known and DOC coagulator such as gypsum could be used as a promising immobilizing agent for safer chives plant production.