Department chief Wichien Jungrungruang said yesterday the latest lab tests on sea water samples collected from 12 of Koh Samet's beaches this month showed that levels of cadmium, mercury and arsenic, as well as Polycyclic Aromatic Hydrocarbons (PAHs), were in line with safety standards. But TPH is still above safety guidelines of one microgram per litre (mg/l), he said.
During Aug 12-22, the department collected sea water samples from the top, middle and bottom end of Ao Phrao. Test results showed that the level of TPH was 0.65 mg/l at the top, 2.60 mg/l in the middle and 0.12 at the bottom end of the beach. A second batch of samples was collected on Aug 27 and produced results showing 0.54 mg/l, 2.7 mg/l and 3.3 mg/l respectively.
"It means there is still oil in the sea. But the TPH level has sharply decreased from 531 mg/l when the oil first hit the island on [July 27]," Mr Wichien said.
He said the TPH level would likely fall within safety standards in one or two months.
The department also collected sea water samples from nine other locations in Rayong province early and in the middle of this month and found that TPH exceeded safety standards at Suan Rukachart (1.4 mg/l), Pak Klong Kreang (1.17 mg/l) and in Ban Phe port areas (1.5 mg/l).
Meanwhile, samples collected early this month showed excessive levels of mercury at Suan Rukachart (0.17 mg/l), Mae Pim cliff (1.6 mg/l), Payoon beach (0.17 mg/l), the Rayong River mouth (1 mg/l) and at Ram Phueng beach (0.7 mg/l). The safety standard for mercury is below 0.1 mg/l.
Tests conducted in these areas in the middle of the month also showed excess mercury readings.
Mr Wichien said blame for the excess amounts of TPH and mercury might not solely lie with the oil spill on July 27 since other human activity such as waste water release could be another cause.
Meanwhile, the cabinet has approved a 6 million baht budget for the department to examine lead-contaminated sediment at Klity Creek in Kanchanaburi province, as a part of a rehabilitation programme ordered by the Supreme Administrative Court in January.
Mr Wichien said the department will survey the 28-kilometre creek for lead-contaminated sediment accumulation and find a safe place to dispose of it.
The department has found lead contamination in animals living in the creek - 734.7 milligrammes per kilogramme in shellfish, 320.2 in crabs and 12.5 in shrimps.