Significant cadmium (Cd) contamination In soil and rice has been discovered in Mae Sot, Tak province, Thailand where the rice-based agricultural systems are established in the vicinity of a zinc mine. The prolonged consumption of Cd contaminated rice has potential risks to public health and health impacts of Cd exposed populations in Mae Sot have been demonstrated. The Thai government has prohibited rice cultivation in the area as an effort to prevent further exposure. Phytoextraction, the use of plants to remove contaminants from soil, is a potential option to manage Cd-contaminated areas. However, successful phytoextraction depends on first identifying effective hyperaccumulator plants appropriate for local climatic conditions. Five sampling sites at Padaeng Zinc mine, Tak province were selected to collect plant and soil samples. Total Cd and Zn concentrations in sediments or soils were approximately 596 and 20,673 mg kg(-1) in tailing pond area, 543 and 20,272 mg kg(-1) in open pit area, 894 and 31,319 mg kg(-1) in stockpile area, 1458 and 57,012 mg kg(-1) in forest area and 64 and 2733 mg kg(-1) in Cd contaminated rice field. Among a total of 36 plant species from 16 families, four species (Chromolaena odoratum, Gynura pseudochina, Impatiens violaeflora and Justicia procumbens) could be considered as Cd hyperaccumulators since their shoot Cd concentrations exceeded 100 mg Cd kg(-1) dry mass and they showed a translocation factor >1. Only Justicia procumbens could be considered as a Zn hyperaccumulator (Zn concentration in its shoot more than 10,000 mg Zn kg(-1) dry mass with the translocation factor >1).

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Sexual dimorphism is the condition where individuals of different sex in the same species exhibit different characteristics beyond the differences in their sexual organs. In this study, individuals of a viviparid species Filopaludina martensi from the Kwai Yai River in Kanchanaburi Province (Thailand) were examined for eight shell and operculum characteristics. Sexual differences were observed in size of shell and operculum, with females being larger than males. The results indicated that morphometric analyses are useful to detect subtle differences between sexes in this species.

Heavy metal pollution in the water supply is a serious environmental problem that affects human health around the world. The goal of this study was to investigate the adsorption behaviour of sugarcane bagasse (SB) and corn stalk (CS) biomass for Pb(II) and Cd(II) removal from metal-contaminated water. When the doses of biomass were increased in solutions containing Pb(II) and Cd(II), the SB and CS showed a trend of increasing metal removal efficiency. The removal efficiency of biomass for Pb(II) decreased as the pH of the solution increased from 5.0 to 7.0, with an optimum pH range of 5 to 6. However, pH has little influence on the removal efficiency of biomass for Cd(II). Adsorption equilibrium is reached in about 15 min. Adsorption for at least four cycles improves Pb(II) removal efficiency (up to 98 %) in solutions containing only Pb(II). The best fitness of the adsorption isotherm to Freundlich suggests multilayer adsorption of metal ions onto CS. Higher qmax and Kf suggest that SB and CS have a greater affinity for Pb(II) than for Cd(II). Pb(II) adsorption potential was found in biomass derived from SB and CS, but it was less effective as a Cd(II) adsorbent. For application in environmental clean-up, we suggest further study on the structural modification of biomass to enhance its metal removal capacity, the regeneration of biomass for better results, and field trials for practical application. HIGHLIGHTS The adsorption behaviour of sugarcane bagasse and corn stalk biomass for Pb(II) and Cd(II) removal from metal-contaminated water was studied The removal efficiency of Pb(II) increases with increased doses of biomass and decreases with increased solution pH and metal initial concentrations Adsorption for at least four cycles improves metal removal efficiency in the case of Pb(II) Freundlich’s isotherm suggests multilayer adsorption of Pb(II) and Cd(II) onto corn stalk biomass Higher qmax and Kf values suggest that sugarcane bagasse and corn stalk have a higher affinity for Pb(II) than Cd(II)