POC fluxes from euphotic zone estimated from ^(234)Th deficiency in winter in the northwestern North Pacific Ocean

Dissolved and particulate 234 Th, particulate organic carbon(PON), nitrogen, and chlorophyll-a concentrations in the upper 200 m of water columns from seven stations in the northwestern North Pacific Ocean were determined in the winter of 1997.The dissolved, particulate, and total 234 Th activities (dissolved plus particulate)show a pronounced deficiency with respect to its parent 238 U in the euphotic zone whereas the total 234 Th shows a near-equilibrium at the depth greater than 100 m.The 234 Th data are used to derive the mean residence time, export fluxes of 234 Th, and fluxes of particulate organic carbon and nitrogen out of the euphotic zone. In the Subarctic Current area, the residence time of dissolved 234 Th with respect to its removal onto particles is 40 ~50 d while the residence time of dissolved 234Th in the subtropical area is about 20 d due to the Kuroshio's influence.The particulate organic carbon(POC)and particulate organic nitroge(PON)fluxes in winter range over 3.8～8.2 and 0.50～0.98 mmol/(m2 ·d), respectively, and are higher in the west region than in the east, and higher in the south than in the north. The co-influence of Kuroshio-Oyashio Currents with supply of nutrient substances from the coastal area and the light condition are two factors determining the horizontal distribution of POC fluxes in winter.The depth distribution of the chlorophyll-a as well as the consistence of the ratio of POC to PON with the Redfield ratio suggest that phytoplankton is the main contributor to the export of POC in this area in winter.The POC fluxes in the northwestern North Pacific Ocean in winter are comparable to some areas in the world oceans in spring and summer seasons.

Persistent organic pollutants PCNs and PBDEs in sediments from coastal waters of Qingdao,Shandong Peninsula

Thirty-one congeners of polychlorinated naphthalenes (PCNs) and 21 congeners of polybrominated diphenylethers(PBDEs)in surface sediments at 5 stations and one mussel sample from Qingdao coastal waters were analyzed. The maximum contents occur at the station near the Haibo River mouth. The total PCNs contents are in the range of 212-1209 pg/g dw, dominated by tri-Cl CN. The total PBDEs contents are in the range of 117-5510 pg/g dw,dominated by tri- to hexa-BrBDEs. The local sources of PCNs are likely from combustion processes such as incinerations and coal burnings. The sources of PBDEs are molecular diffusion from the materials containing them. Except for the area near the river mouth where is affected by the sewage sludges, an important source of PCNs and PBDEs in this area is believed to be the atmospheric deposition. Mussels enrich PCNs and PBDEs relative to the sediments. The total TEQs of PCNs in mussels are lower than the total TEQs of PCBs.