Taek-Kyum Kim

Analysis of Pesticide residues in brown rice using modified QuEChERS multiresidue method combined with electrospray ionization-liquid chromatography-tandem mass spectrometric detection

An efficient and modified Quick Easy Cheap Effective Rugged and Safe (QuEChERS) method combined with liquid chromatography-electrospray ionization with tandem mass spectrometric detection were evaluated for the analysis of residues of 72 pesticides in brown rice including acidic sulfonylurea herbicides. For extraction of pesticides and clean-up of the extract, 1% formic acid in acetonitrile and dispersive solid phase extraction were used, respectively. Two fortified spikes at 50 and 200 μg L−1 levels were performed for recovery test. Mean recoveries of majority of pesticides at two spike levels ranged from 90 to 110% with standard error (Coefficient of Variation) less than 10%. The limits of detection and quantification ranged from 0.24 to 19.92 μg L−1 and 0.79 to 65.74 μg L−1, respectively. Good linearity of calibration curves were achieved with R2>0.9943 within the observed concentration range (from 20 to 400 μg L−1). The modified method also provided satisfactory results for sulfonylurea herbicides, which could not be determined properly with previously reported methods. This method was applied to determine residues of target pesticides in real samples. A total of 22 pesticides in 31 out of 40 tested samples were observed. The highest concentration was observed for tricyclazole at 1.17 mg L−1. This pesticide found in two brown rice samples exceeded its MRL regulated for rice in Republic of Korea. Except this pesticide, concentrations of all observed pesticides were lower than their MRLs. The results reveal that the method is applicable for routine analysis of residues of target pesticides in brown rice.

Effect of household processing on pesticide residues in field-sprayed tomatoes

Tomatoes sprayed with chlorothalonil, oxadixyl, and thiophanate-methyl in a greenhouse were cooked to juice and puree using washing, blanching, peeling, and boiling. Washing reduced amounts of chlorothalonil, oxadixyl, and thiophanate-methyl pesticide residues by 92, 52, and 84%, respectively. A concentration of 3.66% chlorothalonil remained in peeled tomatoes, 0.32% in juice, with no detection in puree. Oxadixyl remained at a concentration of 40% in peeled tomatoes, 54% in juice, and 77% in puree, and the remaining concentration of thiophanate-methyl was 6.2% in peeled tomatoes, 8.7% in juice, and 16.2% in puree. Non-systemic pesticide residues on tomato surfaces could be largely removed through washing and peeling. Reductions in levels of systemic pesticides in tomato pulp during boiling were dependent on the physico-chemical characteristics of pesticides.

Aqueous Degradation of Imidacloprid and Fenothiocarb using Contact Glow Discharge Electrolysis: Degradation Behavior and Kinetics

Degradation of the pesticides fenothiocarb and imidacloprid in water using contact glow discharge electrolysis (CGDE) achieved rates of 57.8 and 43.2% respectively. Degradation was enhanced using citric or hydrochloric acid to lower the pH to 3.0. Both acids enhanced both the degradation rate and the amount. Fenothiocarb degradation was 77.14% at pH 3 with citric acid, and 100% with HCl. Degradation of imidacloprid at pH 3 was 70.18% with citric acid and 93.02% with HCl. Acidic conditions favor either production of ·OH radicals or enhancement of the degradation of organic compounds by ·OH. Both the degradation rates and amounts for fenothiocarb and imidacloprid were reduced in the presence of methanol due to competition between pesticides and MeOH for ·OH. Degradation of pesticides was not completely inhibited by MeOH. Degradation of both fenothiocarb and imidacloprid using CGDE obeys a first-order rate law with high regression coefficient values (R2>0.99).

Optimum Salinity Concentration and Nitrogen Fertilization for Salicornia herbaecea Growth in Reclaimed Land

Now in Korea, halophytes such as Salicornia herbacea and Spergularia marina are being cultivated as new income crops in southwestern coastal regions. So basis studies on halophytes’ growth characteristics is needed for developing a standard cultural practices of them. This study was carried out to investigate on cultivation of Salicornia herbacea, representative halophytes at new reclaimed land. First, in order to examine the characteristics of Salicornia herbacea germination by salinity (NaCl concentration 0 ~ 3%), germination tests were carried out. At the low-temperature 10C, germination of Salicornia herbacea was slow but lasted for 15 days at all salinities, and final germination rates were of 78 ~ 90%. At higher than 20C, maximum germination rate was showed within four days. Germination inhibition by salt was showed at NaCl concentration 3% and 30C. The second, to investigate on the growth characteristics of Salicornia herbacea by nitrogen fertilization, port experiments were conducted at the greenhouse. Salicornia herbacea’s buds began to be found after five days after sowing. Salicornia herbacea growth such as plant height, number of braches, etc. increased with increasing nitrogen fertilization. In order to investigate the growth characteristics by salinities, cultivation test of Salicornia herbacea was conducted in nutriculture with different salinities. In the plot without NaCl, the growth of Salicornia herbacea was very low, and it began to wither within one month. In plots with NaCl, the growth of Salicornia herbacea was well until concentrations of NaCl 500mM, and optimum NaCl concentration was 200mM for growth of Salicornia herbacea. Field verification experiments about the effect of nitrogen fertilization on transplanted Salicornia herbacea were conducted at the Saemangeum reclaimed land in Korea. There was a tendency to increase number of branches and plant length with increasing nitrogen fertilization. Amount of P2O5 and mineral element such as CaO, Na2O, K2O and MgO tended to increase with increasing nitrogen fertilization. However, there was no statistically significant difference.

Effects of Nitrogen Fertilization Increment on Forage Crops Cultivation in Saemangum Reclaimed Land

This study was conducted to find out the optimum cropping system for the stable production of forage crops in the newly reclaimed land located at Gwanghwal region of Saemangum reclaimed land in which the soil is sandy loam (Munpo series). There were two treatments of nitrogen fertilization 20% increment based on the standard fertilization of 150, . Whole crop barley as the winter crop sowed on 27 October. After the whole crop barley was harvested at the end of May. Corn and sorghumsudangrass as the summer crop sowed at the early of June successively on the same field. Emergence rate the whole crop barley was high while the summer crops were low. Soil salinity was increased during cultivation of summer crops. However, corn and sorghumsudangrass were not damaged by salt. Increase of nitrogen fertilization made the growth of cultivation crops good, stem and leaf tended to have a lot of the mineral nutrients at heading stage and silking stage. After experiment, among soil chemical properties pH, content of exchangeable sodium were decreased and content of organic matter, available phosphate were increased. Dry matter yield were showed whole crop barley and sorghumsudangrass by increment of nitrogen fertilization. Therefore, to improve the product and nutrient balance of reclaimed saline land comprehensive soil management should be considered.

Establishment on Fertilizer Recommendation and Soil Characteristics of Rice Paddy with Environment-friendly Cultivation

Environment-friendly agriculture (EFA) are aimed to reduce use of chemical inputs as possible the recycling of resources and the environment while preserving the local resources in the long term to ensure a constant productivity and profitability for producing safe food. This study was conducted to investigate characteristics on soil environment at paddy field of environment-friendly agriculture regions (EFARs) in Honam area. Survey point of EFARs Chungnam, Jeonbuk and Jeonnam, rice bran farming method in two districts, rice bran + snail farming method in eight districts, snail farming method in five districts and ducks farming method in three districts a total of 18 districts were selected. Annual of farming method, friendly-environment certification, amount of applied fertilizer, and history of cultivation to the farm household were surveyed. The content of available phosphate and silicate among the soil chemical properties in EFA paddy field were a little lower than optimum level, and those of agricultural methods fertilized with rice bran were a little lower than those of others. Hardness among the soil physical properties in EFA paddy field were a little lower than conventional practices, and that of agricultural methods fertilized with rice bran were a little lower than those of others. We showed fertilizer recommendation dose about soil nutritional shortages according to fertilization prescriptions index by crops.

Nitrogen Fertilization on the Growth of Rape (Brassica napus L.) in Newly Reclaimed Land in Korea

This study was conducted to find out the optimum nitrogen application rate for the stable production of rape in the newly reclaimed land located at Gangwhal region of Saemangum reclaimed land in which the soil is sandy loam (Munpo series). There were five treatments of nitrogen fertilization from zero to 60% increment based on the standard fertilization of . The growth of rape (Sunmang) was not affected by salt content while soil salinity was increased at blossoming season of rape. Compared to yield of standard fertilization the yield and the content of oleic acid of rape were increased by 4~26% with the increasing additional nitrogen fertilizer. The results obtained from the growth and yield of rape in this study indicated that it was possible to cultivate rape in a newly reclaimed land if soil salinity was kept below .