Land-Ocean Exchange Mechanism of Chlorinated Paraffins and Polycyclic Aromatic Hydrocarbons with Diverse Sources in a Coastal Zone Boundary Area, North China: The Role of Regional Atmospheric Transmission

The marine environment is regarded as a crucial sink of numerous land-origin pollutants. As typical boundary regions, the coastal and offshore areas are used to evaluate the dominating transfer process and land-ocean exchange mechanism of semivolatile organic compounds. In air samples collected from a coastal area in North China over a whole year, chlorinated paraffins (CPs), including short-chain CPs and medium-chain CPs, and prior control 16 polycyclic aromatic hydrocarbons (PAHs) were determined, with mean concentrations of 25.8 and 94.7 ng/m3, respectively. Results of different gas-particle partitioning models indicated that the steady-state hypothesis provides a better description of the possible land-ocean exchange molecular mechanism. The source-sink influences for CPs and PAHs were affected by the predominant atmospheric motion, which alternated between gaseous diffusion and particulate sedimentation in different seasons. Source apportionment results indicated that different transfer characteristics contributed to the source divergence of ambient CPs and PAHs within 12 nautical miles in the same area. Coal/biomass combustion and diesel/natural gas combustion were the main PAH sources in the coast site (43.1%) and sea site (35.3%), respectively. Similar industrial sources CP-52 and CP-42 were the main CP sources in the coast site (41.4%) and sea site (40.8%), respectively.

Automated summary

The marine environment is an important sink for many land-origin pollutants, and coastal and offshore areas are used to study the transfer process and exchange mechanism of organic compounds. A year-long study in a coastal area of North China found high concentrations of chlorinated paraffins (CPs) and polycyclic aromatic hydrocarbons (PAHs) in air samples. Different gas-particle partitioning models suggest that the steady-state hypothesis provides a better explanation for land-ocean exchange. The source-sink influences of CPs and PAHs are affected by atmospheric motion, alternating between gaseous diffusion and particulate sedimentation in different seasons. Source apportionment results show different transfer characteristics contribute to the source divergence of CPs and PAHs within a 12 nautical mile radius in the same area.