Distribution and relation between cadmium and zinc in soils, Mae Ku floodplain, Mae Sot district, Tak province

During 1999-2003, International Water Management Institute and Department of Agriculture found that cadmium (Cd) concentration in rice grain, soil and sediment samples from Mae Tao area were exceeded the standard level. Since then, the area has been recognized to be the Cd contaminated area. Mae Ku is an area located nearby Mae Tao. Both area Mae Tao and Mae Ku are located in Mae Moei river basin. Tributaries from upland area where zinc (Zn) mining located run pass through Mae Toa lowland directly where some creeks run through Mae Ku flood plain area. Therefore, Mae Ku is an area to be concern for Cd contamination. However, the details amount of Mae Ku is limited. The objectives of this study were to investigate Cd distribution in soil of Mae Ku flood plain and to study the relationship between Cd and Zn in soils. Therefore, soil samples in Mae Ku floodplain were collected using grid system. The samples were determined both total and available Cd and Zn concentrations by ICP-OES. Total Cd and Zn concentrations in samples range between 0.42 to 101.69 and 29.34 to 2,347.74 mg/kg with a mean value of 4.93 and 209.94 mg/kg, respectively. Almost of total Cd concentration in samples (-75%) less than 3 mg/ kg. The site anomalies were found in 2 samples which the total Cd concentrations were more than 80 mg /kg. These samples are located in east part of study area. Total Cd and Zn concentrations in soil samples show a significant positive linear relationship. Moreover, available Cd and Zn concentrations range between 0.03 to 63.78 and 2.04 to 1,033.92 mg/kg with a mean value of 2.48 and 55.46 mg/kg, respectively. The ratio of available fraction and total Cd and Zn concentrations are 0.4 and 0.02, respectively. These indicated that Mae Ku area has been facing the Cd contaminated in soils. The major source of Cd contamination may be from anthropogenic activities, particularly zinc mines. Runoff from high land where zinc mines are located, is the importance carrier which conveys the sediment from high land to floodplain area. This sediment was deposited into soil and then lead to the contamination of Cd in Mae Ku area.