Downstream from Bangkok, the Chao Phraya River has been contaminated with heavy metals from
industrial discharges.4 In the Gulf of Thailand, just below the mouth of the Chao Phraya, for example, the
dissolved mercury content ranges from 0.7 to 4.0 ppb (parts per billion). Concentrations of mercury in nonpolluted
water are less than 0.1 ppb.