Equilibrium partitioning approach for metal toxicity assessment in tropical estuarine sediment of Bandon Bay, Thailand.

An equilibrium partitioning approach (EqPA) was employed to evaluate the metal toxicity and define sediment quality guidelines (SQGs) for arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), and mercury (Hg) in the cockle cultivated areas located in Bandon Bay, Thailand. An assessment of metal toxicity using the [∑SEM]-[AVS] and [∑SEM]-[AVS]/foc models indicated no adverse effect on benthic organisms. The normalized total metal concentrations in this area were below the established SQG values for As, Cd, Cu, Ni, Pb, Zn, and Hg, namely respectively 21.3, 0.8, 84.6, 36.0, 34.6, 440.9 mg/kg dry weight, and 49.3 µg/kg dry weight on sand and calcium carbonate free with 1 % total organic carbon basis, suggesting low metal toxicity. This study provides locality adapted SQG values for supporting sediment quality management specifically in Bandon Bay, potentially serving as a model for other coastal areas.

Presence and Health Risks of Obsolete and Emerging Pesticides in Paddy Rice and Soil from Thailand and China.

Organochlorine (OCPs) and organophosphorus pesticides (OPPs) have been intensively applied in rice paddy field farming to control pest infestation and increase the yield. In this study, we investigated the presence of organochlorine and organophosphorus pesticides in paddy rice and soil from rice plantations in Thailand and China. According to concentration and distribution of OCPs, the most abundant OCPs residues in rice and soil from Thailand and China were dichlorodiphenyltrichloroethane and hexachlorocyclohexanes. The OPPs of methidathion, carbophenothion, chlorpyrifos, and diazinon were common to Thailand and China in both types of samples. The detection frequency of multiple types of these pesticides was greater than 50% of total samples. The relative concentration of some OPPs residues in rice and soil from Thailand and China were significantly different from each other (p < 0.0083), whereas, no significant difference was observed for the relative concentration of OCPs residues in rice and soil from both countries, except for HCHs (p < 0.05). Bioaccumulation factors of OCPs between rice and soil samples indicated that OCPs and OPPs in soil could accumulate in rice. The carcinogenic and non- carcinogenic risks of OCPs and OPPs seem to be in the safe range as recommended by the European Union.