Pb/Ca in Thailand Coral Determined by LA-ICP-MS: Anthropogenic Pb Input of River Run-off into a Coral Reef from Urbanised Areas

In order to monitor lead pollution from urban areas to coral reefs in the Gulf of Thailand, linear and two-dimensional distributions of Pb in corals from Khang Khao Island, Thailand and Rukan-sho, Okinawa, were analysed with high resolution. Laser ablation inductively coupled plasma mass spectrometry was applied to measure Pb content in coral skeletons using synthetic Pb standards in a CaCO3 matrix as calibration materials. Linear and two-dimensional ablation schemes were applied to determine the Pb content in corals collected from Khang Khao Island, Thailand and Rukan-sho, Okinawa. The coral skeleton was ablated by Nd:YAG laser (wavelength of 266 nm, beam diameter of 155 mu m, scanning speed of 10 mu m s(-1) and frequency of 10 Hz) along the growth axis, and ion counts for Pb-208 were normalised to Ca-42. Lead content in the corals was determined using a calibration curve obtained from the synthetic Pb standards (0-141 mu g g(-1)). The linear ablation track of the sample from Khang Khao showed over 30 peaks of Pb with an average value of 3.55 mu g g(-1), while Pb content in the coral from Rukan-sho showed relatively small variation with an average value of 0.132 mu g g(-1). Two-dimensional imaging of Pb in the coral skeletons was also carried out for an area of 7x20 mm on the sample from Khang Khao. The distribution patterns of Pb and Ba in the Thailand coral co-varied. These observations from the linear and imaging analyses suggest discontinuous inputs of anthropogenic Pb from rivers to the Gulf of Thailand.