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

摘要

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 CaCO_3 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,rnbeam diameter of 155 μm, scanning speed of 10 μm s~(-1) and frequency of 10 Hz) along the growth axis, and ion counts for ~(208)Pb were normalised to ~(42)Ca. Lead content in the corals was determined using a calibration curve obtained from the synthetic Pb standards (0-141 μg 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 μg g~(-1) while Pb content in the coral from Rukan-sho showed relatively small variation with an average value of 0.132 μg g~(-1). Two-dimensional imaging of Pb in the coral skeletons was also carried out for an area of 7 × 20 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.