Jessie Gutierrez

Heavy Metal Contamination of Arable Soil and Corn Plant in the Vicinity of a Zinc Smelting Factory and Stabilization by Liming

The heavy metal contamination in soils and cultivated corn plants affected by zinc smelting activities in the vicinity of a zinc smelting factory in Korea was studied. Soils and corn plants were sampled at the harvesting stage and analyzed for cadmium (Cd) and zinc (Zn) concentration, as well as Cd and Zn fraction and other chemical properties of soils. Cd and Zn were highly accumulated in the surface soils (0–20 cm), at levels higher than the Korean warning criteria (Cd, 1.5; Zn, 300 mg kg−1), with corresponding mean values of 1.7 and 407 mg kg−1, respectively, but these metals decreased significantly with increasing soil depth and distance from the factory, implying that contaminants may come from the factory through aerosol dynamics (Hong et al., Kor J Environ Agr 26(3):204–209, 2007a; Environ Contam Toxicol 52:496–502, 2007b) and not from geological sources. The leaf part had higher Cd and Zn concentrations, with values of 9.5 and 1733 mg kg−1, compared to the stem (1.6 and 547 mg kg−1) and grain (0.18 and 61 mg kg−1) parts, respectively. Cd and Zn were higher in the oxidizable fraction, at 38.5% and 46.9% of the total Cd (2.6 mg kg−1) and Zn (407 mg kg−1), but the exchangeable + acidic fraction of Cd and Zn as the bioavailable phases was low, 0.2 and 50 mg kg−1, respectively. To study the reduction of plant Cd and Zn uptake by liming, radish (Raphanus sativa L.) was cultivated in one representative field among the sites investigated, and Ca(OH)2 was applied at rates of 0, 2, 4, and 8 mg ha−1. Plant Cd and Zn concentrations and NH4OAc extractable Cd and Zn concentrations of soil decreased significantly with increasing Ca(OH)2 rate, since it markedly increases the cation exchange capacity of soil induced by increased pH. As a result, liming in this kind of soil could be an effective countermeasure in reducing the phytoextractability of Cd and Zn.

Effect of Intermittent Drainage on Methane and Nitrous Oxide Emissions under Different Fertilization in a Temperate Paddy Soil During Rice Cultivation

Although intermittent drainage is regarded as a key factor to reduce methane (CH4) emission from paddy soil during rice cultivation, it also could increase nitrous oxide (N2O) emission. However, the effects of intermittent drainage on CH4 and N2O emissions with different global warming potential (GWP) values have not been well examined. In the present study, the effect of a 26-day intermittent drainage from the 34th day after transplanting (DAT) to the 60th DAT on two greenhouse gas (GHG) fluxes and yield properties were compared with those of a continuous flooding system under different fertilization (NPK as control, PK, and NPK+straw) during rice cultivation. The effect of intermittent drainage on changing two GHG emissions was compared using the GWP value, calculated as CO2 equivalents by multiplying 25 and 298 to the seasonal CH4 and N2O fluxes, respectively. Under the same irrigation condition, addition of nitrogen to PK significantly increased seasonal CH4 and N2O fluxes, and addition of straw to NPK increased CH4 and N2O. Irrespective with fertilization background, the intermittent drainage significantly reduced the total GWP by ca. 41–70% as affected by the big reduction of seasonal CH4 fluxes by ca. 43–53% to that of the continuous flooding even with an increase of seasonal N2O emissions by ca. 16–43%. Rice productivity was not significantly different between the two different irrigation systems under same fertilization background. As a result, total GWP per grain yield was significantly lower in all fertilization treatments with intermittent drainage compared with continuous flooding.

Importance of rice root oxidation potential as a regulator of CH4 production under waterlogged conditions

One of the most important characteristics of a rice cultivar controlling methane (CH4) production can be the root oxidation potential because a cultivar with a high oxygen (O2)-releasing capacity can create an oxidized root area in the rhizosphere and this can oxidize CH4 during rice cultivation. The root oxidation potential of six Korean rice cultivars grown in a minirhizotron was measured by digital image analysis of the oxidized root areas and compared with the conventional method (root oxidase activity by using α-napthylamine as a substrate). In addition, pmoA gene copy numbers of the rhizosphere of the cultivars, indicating soil methanotrophic bacterial population and measured by qPCR assays, were compared. Oxidized root area and pmoA gene copy numbers differed significantly among cultivars (P < 0.05), but not the root oxidase activity. Oxidized root area was significantly and negatively correlated with rhizospheric dissolved CH4-C and mean CH4 emission rate by plants and significantly and positively correlated with the rhizospheric dissolved carbon dioxide (CO2)-C and pmoA gene copy number as well as with some of selected plant growth parameters such as root biomass and root volume. The Dongjin cultivar had a high root oxidation potential, while Nampyeong, Chuchung, and Samkwang had a low root oxidation potential under a flooded paddy soil environment. In addition, the characterization of oxidized root area by digital image analysis rather than the α-napthylamine oxidation method was more effective in differentiating root oxidation potential among different lowland rice cultivars.

Effect of Irrigation Water Salinization on Salt Accumulation of Plastic Film House Soil around Sumjin River Estuary

The causes of salt accumulation in soils of plastic film houses nearby Sumjin river estuary in Mokdo-ri(), Hadong, Gyeongnam, Korea were investigated in 2006. With chemical properties soils and water analyzed and fertilization status monitored, the study showed that mean salt concentration of soil was much higher at EC than the Korean average (EC ) in 2000s for plastic film houses soil with exchangeable Na and water-soluble Cl , and then might result to salt damage in sensitive crop plants. Salt concentration of ground water used as main irrigation water source contained very high EC with corresponding value of . Particularly, increase of EC value was directly proportional with the increased pumping of ground water used as a water-covering system in order to protect the temperature inside plastic film houses from the early winter season. High Na and Cl portion of ions in water might had contributed to the specific ion damage in the crops. Secondly, heavy inputs of chemicals and composts significantly increased the accumulated salts in soil. Conclusively, salt accumulation might had been accelerated by use of salted-groundwater irrigation and heavy fertilization rate. To minimize this problem, ensuring good quality of irrigation water is essential as well as reducing fertilization level.

Evaluation of rice root oxidizing potential using digital image analysis

Abstract The aerenchymal transport of oxygen to rice roots has significantly influenced the anaerobic root zone of flooded paddy soils. Therefore, the visualization of redox dynamics may be useful to characterize rice root oxidation potentials and the dynamics of redox-influenced ions in the root zone of paddy soils. In order to investigate the interaction between root oxidation potential and Fe uptake of (a) six different rice cultivars (Oryza sativa L.; Chuchung, Dongjin, Ilmi, Junam, Nampyeong, and Samkwang) were monitored in a flooded paddy soil with the aid of rhizotron experiment throughout the vegetation period, (b) digital images of the root zone were taken at the important growing stages, and (c) rice Fe uptake was characterized simultaneously. The images were processed by image analysis to display the reduction and oxidation areas in the root zones, and the distinct areas which were colorized due to varying soil redox changes were localized and quantified. Oxidized areas were mainly observed in the surrounding active roots and in a distinct layer on the soil surface. The selected rice cultivars have shown significantly different root-oxidized areas at the same rice growing stage. Root-oxidized area was significantly and positively correlated with total Fe content of rice root, but negatively correlated with the inner root Fe content. Rice cultivars having higher root oxidation potential precipitated more Fe on the outer root surface in the form of Fe plaques. In conclusion, digital image analysis is an effective tool for evaluating the oxidizing potential of rice root under anaerobic soil condition.

Effect of seedling transplanting date on methane emission from rice paddy soil during cultivation

In most temperate mono-rice cultivation systems like Korea, the local recommended transplanting date of rice (Oryza sativa L.) seedlings is proposed by the government agency considering climate, rice cultivar, rice productivity and quality, etc. Recently the transplanting of rice seedlings earlier than the recommended transplanting date (RTD) has been adopted by the local farmers to get high yield and to harvest earlier for higher market value. Earlier transplanting than RTD might influence methane (CH4) emission due to the prolonged cultivation period, but its effect was not evaluated well so far. In this study, the effects of seedling transplanting date on CH4 emission and rice productivity were investigated for two years in a general paddy soil. The 30-day old seedlings were transplanted on the local RTD (every June 15) as the control, and at 30 and 15 days before and 15 days after the RTD for comparison. There was no difference on CH4 flux pattern among the treatments, but the earlier transplanting before the RTD significantly (P  ≤ 0.05) increased total CH4 emissions during rice cultivation due to the extended soil flooding period and improved plant growth. Rice grain yield was increased by earlier transplanting, but the values were not significantly different from those of transplanting practices on RTD and 15 days before RTD. Therefore, among all the treatments, the lowest total CH4 emission per grain yield was observed in the RTD treatment. Conclusively, rice transplanting following the RTD, rather than early or late transplanting, could be more effective to minimize CH4 emission without significantly decreasing the rice productivity.

Determination of Cadmium and Zinc Contamination Source in Arable Soil in the Vicinity of a Zinc Smelting Factory

Agricultural area in the vicinity of the smelting factory in Kyeongbuk province, the third △△ largest zinc smelting factory in the world, was contaminated by high concentration of heavy metals. However, the heavy metals source was not yet directly traced and thus, resulted to a conflict between the factory and residents within its vicinity. In order to determine the level of heavy metal contamination in the arable lands located at the north eastern part of the factory, soils were sampled systematically. To find out the major reason for the occurrence of this problem, waters and aerosols were sampled with constant intervals to the upward and downward direction from the factory and were analyzed to find out the heavy metal concent- rations. Cadmium (Cd) and zinc (Zn) of the heavy metals were highly accumulated more than the Korean warning criteria (Cd 1.5, Zn 300 mg kg -1 ) with mean values 1.7 and 407 mg kg -1 , respectively, at the surface soils (0-20 cm), and heavy metal concentration significantly decreased with increasing soil depth. In addition, the concentration of both metals slightly decreased with increasing distance from the factory to the surface soils. Cadmium and Zn were detected in the upward stream water with low concentration and concentrations increased significantly in the downstream after passing across the factory. Aerosol samples also showed traces of Cd and Zn which could be attributed to the contamination of the water system and the surface soils. Conclusively, Cd and Zn emitted from the smelting factory moved with the aerosol in the atmosphere △△ and thus, contaminated the agricultural areas and the water system within its vicinity.

Cadmium and Zinc Uptake Characteristics of Corn Plant in Arable Soil Contaminated by Smelting Factory Source

The cadmium (Cd) and zinc (Zn) contamination of soils and cultivated crop plants by zinc smelting activities was studied. In the study area of the vicinity of zinc smelting factory in Korea, soils and corn plants were sampled at corn harvesting stage and analyzed Cd and Zn concentration as well as Cd and Zn fraction and chemical properties in soils. At 600 m radius of studied area, Cd and Zn were highly accumulated in the surface soils (0 - 20 cm) showed greater than the Korean warning criteria (Cd 1.5, Zn 300 mg ) with corresponding values 1.7 and 407 mg , respectively. The leaf part gave higher Cd concentration with the corresponding value of 9.5 mg as compared to the stem and grains pare (1.6 and 0.18 mg ), respectively. Higher Zn concentration was also obtained from the leaf part of the corn plant which gave the value of 1,733 mg . The stem and grain part gave corresponding values of 547 and 61 mg . The order of the mean Cd concentration in fractions is F3 (oxidizable fraction) > F2 (reducible fraction) > F4 (residual fraction) > F1 (exchangeable + acidic fraction). A highly positive correlation is observed between F2 and concentration of Cd and Zn in both plant pare, leaf and grain. Highly positive correlations are shown in the pH exchangeable Ca and Mg, and CEC when correlated with Cd and Zn bound to F4 fractions. To reduce Cd and Zn uptake by corn plant in an arable land heavily contaminated with Cd and Zn as affected by smelting factory, an efficient and effective soil management to increase soil pH and CEC is thus recommended.