Heavy metal contamination and bioaccumulation in Khorat snail-eating turtles (Malayemys khoratensis) from an e-waste recycling activity site in Thailand

Turtles, as a long-lived reptile, have been used as important tools to study heavy metal contamination because the accumulation of pollutants in the turtles is indicative of human health and ecological risks. The purpose of this study was to examine 10 heavy metals, including Fe, Mn, Zn, Cu, Cr, Ni, As, Pb, Cd and Hg, in the surface waters, sediments, gastropods, and Khorat snail-eating turtle (Malayemys khoratensis) blood and to investigate the bioaccumulation factor (BAF) influenced by the heavy metal e-waste recycling activities in the area. Heavy metals were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). The mean concentrations of heavy metals were Fe > Mn > Zn > As > Ni > Pb > Hg in the surface waters, Fe > Mn > Zn > Cr > Pb > Ni > Cu > As > Hg in the sediments, Fe > Mn > Zn > Cu > Cr > Ni > As = Pb > Cd = Hg in gastropods and Fe > Zn > Cu > Ni > Cr > Hg > Pb in turtle blood. Noteworthy, the highest concentration of toxic heavy metal in surface water was As (0.0020 +/- 0.0006 mg/L) while Cr was highest in sediments (10.6320 +/- 2.3711 mg/kg), gastropods (0.9563 +/- 0.3426 mg/kg) and turtle bloods (0.0706 +/- 0.0131 mg/L). Zn had the highest BAF concentration in turtle blood (7,958.4240 +/- 6,798.5850 L/kg) and significant bioaccumulation potential. This study presented that heavy metal pollution from e-waste recycling sites can accumulate in freshwater turtles and implies that the rice field ecosystems around the e-waste recycling activity site were contaminated with toxic heavy metals. Therefore, the local people and wildlife inhabiting the areas were exposed to toxicity risks from toxic heavy metals from unsafe recycling activities.