Evaluation of heavy metal contents and Pb isotopic compositions in the Chao Phraya River sediments: Implication for anthropogenic inputs from urbanized areas, Bangkok

In order to elucidate the sources of metals in urbanized areas, heavy metal contents and Pb isotope ratios were determined in the Chao Phraya River sediments. The sediment samples were leached using 1% HNO3 and metal concentrations (Cd, Cu, Cr, Pb, and Zn) and Pb isotopic ratios (208Pb/206Pb and 207Pb/206Pb) in the solutions were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The highest ranking of potential pollutant evaluations of Cd, Cu, Cr, Pb, and Zn contents was found from samples that were located near to the center of Bangkok. Pb isotope ratios (208Pb/206Pb: 2.075–2.113 and 207Pb/206Pb: 0.834–0.868) in the Chao Phraya River sediments near to the center of Bangkok agreed well to those in the Bangkok road side dust and pond sediments suggesting that river sediments may be contributed from road-side dust and pond sediments. Moreover, Pb isotope ratios confirmed that the polluted sediments were contributed as Pb products of fly ashes (municipal waste combustors) in Bangkok (208Pb/206Pb: 2.100–2.120 and 207Pb/206Pb: 0.867–0.870).

► We determined metal contents and Pb isotopes in the Chao Phraya River sediments.
► The highest of metal concentrations were found at 40 km from the river mouth.
► Lead pollution at 40 km is related with Bangkok road-side dust and pond sediments.
► It is contaminated by Pb product of fly ashes.