Seasonal variations and distribution characteristics of petroleum hydrocarbons in northern Yellow Sea

An investigation on concentrations of dissolved petroleum hydrocarbons (DPH) in the surface water of northern Yellow Sea of China has been conducted in spring, summer, autumn, and winter during Jun. 2006~Oct. 2007. Based on the acquired data, the seasonal variations and distribution characteristics were analyzed. The results showed that the annual mean concentration of DPH in the surveyed area was 0.050 mg/L, within the concentration limit of Grade I (Ⅱ) according to National Seawater Standard. The seawater was slightly contaminated and the concentrations of DPH varied seasonally. The highest average concentration (0.099 mg/L) appeared in summer, which was classified as Grade Ⅲ seawater. The average values in spring (0.022 mg/L) and autumn (0.027 mg/L) were much lower, within the concentration limit of the Grade I (Ⅱ) seawater. The average value in winter (0.051 mg/L) was slightly beyond the concentration limit of Grade I (Ⅱ) seawater. Based on the data of the seasonal variation and distribution characteristics, it was concluded that the concentrations of DPH in Bohai Strait, ports and the northernern Yellow Sea were relatively higher, and those near Changshan Islands were lower.