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Contamination of persistent organochlorines (OCs) such as PCBs (polychlorinated biphenyls), DDT and its metabolites (DDTs), HCH (hexachlorocyclohexane) isomers (HCHs), chlordane compounds (CHLs), and HCB (hexachlorobenzene) were examined in mussels collected from coastal waters of Asian countries such as Cambodia, China, Hong Kong, India, Indonesia, Japan, Korea, Malaysia, Philippines, Far East Russia, Singapore, and Vietnam in 1994, 1997, 1998, 1999, and 2001 to elucidate the contamination status, distribution and possible pollution sources and to assess the risks on aquatic organisms and human. OCs were detected in all mussels collected from all the sampling sites investigated. Considerable residue levels of p,p(')-DDT and alpha-HCH were found in mussels and the concentrations of DDTs and HCHs found in mussels from Asian developing countries were higher than those in developed nations suggesting present usage of DDTs and HCHs along the coastal waters of Asian developing countries. On the other hand, lower concentrations of PCBs detected in mussels from Asian developing countries than those in developed countries indicate that PCBs contamination in mussels is strongly related to industrial and activities. To our knowledge, this is a first comprehensive report on monitoring OCs pollution in the Asia-Pacific region.

The anthropogenic radionuclides, 90 Sr, 137 Cs and 239+240 Pu, were measured in the water column of the Japan Sea/East Sea during 1997–2000. The vertical profiles of radionuclide concentrations showed: exponential decrease with depth for 90 Sr and 137 Cs, and surface minimum/subsurface maximum for 239+240 Pu. These results do not differ substantially from results reported previously. The area-averaged concentrations of radionuclides in the Japan Sea are higher than those found in the Northwest Pacific Ocean below surface layer showing the accumulation of the radionuclides in the deep waters in the Japan Sea. Concerning spatial distributions, the area of high 137 Cs inventory extends from the Japan Basin into the Yamato Basin. It is suggested that wintertime convection of water, occurring mainly in the Japan Basin, causes the radionuclides to sink. The nuclides then advect into the Yamato Basin after detouring around the Yamato Rise.

The concentrations of 239+240 Pu and 137 Cs in zooplankton and nekton in the Northwest Pacific and Southern Oceans were measured during the period 1993–1996. The object of the sampling was to assess the potential impacts of existing submerged anthropogenic-radioactive materials in the western North Pacific as well as the East China Sea. Samples from the Bransfield Strait of the Antarctic Ocean provided a control source impacted by only atmospheric bomb fallout. No particularly elevated levels of 239+240 Pu were found in zooplankton samples from the Northwest Pacific, although significantly lower levels of 239+240 Pu were found in three mixed zooplankton samples from the Bransfield Strait. The body burden of 239+240 Pu in zooplankton appears to reflect concentrations in ambient seawater with some variation. Some additional measurements of 137 Cs in fish are also reported here to complement existing databases and for future reference in the regional marine environmental radioactivity monitoring effort.

A comprehensive investigation of radionuclide distributions in seawater and bottom sediments of Peter the Great bay was conducted in September–October 1994. Sampling sites were chosen close to potential radioactivity sources as well as in fishing and recreational areas. The results have shown that the main sources of radionuclides in Peter the Great bay are still global atmospheric fallout and the discharge of freshwater and suspended sediments from river runoff. Activities of 137 Cs and 90 Sr in seawater were in the ranges 1.7–5.7 and 1.7–6.6 Bq m−3, respectively, with activities of 137 Cs in bottom sediments 60 Co was found in bottom sediments of Strelok bay (close to Chazhma bay entrance, up to 150 Bq kg−1) and in a limited area in Ussuriysky bay (up to 21.6 Bq kg−1). Further studies in 1996 and 1997 also did not reveal any radionuclide sources connected with the navy facilities except for the consequences of the Chazhma bay accident.

Over the past decade there has been growing concern over dumping of radioactive waste in the East Sea (Sea of Japan) proper and adjacent coastal waters. Here we show that the evolution of activity concentrations of 137Cs and 239+240Pu in the East Sea, and existing levels of radioactive contamination in waters, sediments and biota from Peter the Great Bay (Russia) can be largely attributed to global fallout deposition. The former sequence of data includes results from the AWARES cruise (Active Watch of Artificial Radionuclides in the East Sea) conducted between 26 October and 1 November 1993 about ten days after 14 GBq of liquid radioactive waste was dumped into the East Sea. The activity concentration of 137Cs and 239+240Pu in surface waters ranged between 2.7–3.5 Bq m−3 and 3.5–20.8 mBq m−3, respectively, and were not different to levels observed during August 1993 prior to the Russian dumping operation in October. Isotopic ratios also indicate the absence of any significant anthropogenic radioactive contamination in the region other than from global fallout deposition.

Assessment of contamination of anthropogenic radionuclides from past dumping of radioactive waste in areas of the Okhotsk Sea, NW Pacific Ocean and the Sea of Japan/East Sea has been performed. Two joint Japanese-Korean-Russian scientific expeditions were carried out in 1994-1995, where seawater and seabed sediments were samples from 22 sites. Results of sediment analysis are reported here, where concentrations of 90 Sr, 137 Cs, 238 Pu, 239,240 Pu and 241 Am in surface layer and bulk sediments showed on large spatial variations, ranging between < 0.04 and 0.75 Bq kg 1 dry wt., < 0.2 and 7.2 Bq kg -1 dry wt., < 0.001 and 0.08 Bq kg -1 dry wt., 0.006 and 2.0 Bq kg -1 dry wt., 0.03 and 1.8 Bq kg -1 dry wt., respectively. However, the concentrations are comparable with those found in reference sites outside the dumping areas and they generally fall within ranges previously reported for non-dumping areas of the investigated seas. Estimates of sediment inventories indicated differences in radionuclide load between shelf/slope and basin type sediments as well as dependence on water depth. Except for the shallow areas, most of the inventories of 90 Sr, 137 Cs and Pu isotopes are still to be found in the water column. Total inventories (in water + sediment) show a surplus of 137 Cs and Pu-isotopes compared to expected integrated global fall-out deposition, which is consistent with previous observations in non-dumping areas in the seas investigated. Analysis of sediment 238 Pu/ 239,240 Pu activity ratios showed values in accord with that of global fall-out. Analysis of radionuclide depth distributions in core samples from areas of the Sea of Okhotsk showed sedimentation rates of 0.2-0.4 g cm -2 year -1 and 0.03 g cm -2 year -1 for shelf and basin areas respectively, which is similar to values found in the Sea of Japan/East Sea. Depth profiles of 90 Sr, 137 Cs and Pu isotopes in cores of the basin area indicate a typical delay compared to the input records of global fall-out.

Measurements of anthropogenic radionuclides in seawater samples near dumping sites of the East Sea/Japan Sea were conducted, as the first-stage Japanese–Korean–Russian Joint Expedition, in March–April 1994, to assess radioactive contamination of the East Sea/Japan Sea after the dumping of radioactive wastes by the former Soviet Union and Russian Federation. Concentrations of 137 Cs, 90 Sr and 239,240 Pu in surface waters of the East Sea/Japan Sea near dumping sites were in the ranges of 2.8–3.6,1.6–2.0, and 8–25 Bq kg -1 , respectively. Surface 137 Cs and 90 Sr concentrations were the same order of magnitude as those observed in the North Pacific, whereas surface 239,240 Pu concentration was significantly higher than those observed in the North Pacific. Vertical profiles of 137 Cs and 90 Sr, with surface maxima and decreasing with depth, showed higher depth gradients than those observed in the North Pacific, reflecting deep convection in the north central East Sea/Japan Sea. The higher 239,240 Pu concentration in the surface waters of the north central East Sea/Japan Sea may reflect rapid recycling of deep Pu. The results revealed that most of the recent radioactivity observed in the north central East Sea/Japan Sea was of global fallout origin from atmospheric nuclear testing and partly the Chernobyl fallout. In this survey, there was no clear evidence of an increase in radionuclide concentrations due to the dumping of radioactive wastes by the former Soviet Union and Russian Federation.

New data on trace metal distribution in bottom sediments of Peter the Great Bay (the Sea of Japan) are presented. Much higher concentrations were detected near the most likely anthropogenic sources of trace metal inputs (waste water discharges from Vladivostok and Nakhodka, and the Vladivostok coastal landfill). Sediments in these contaminated areas were up to 700 ppm in Zn, 530 ppm in Pb, 7 ppm in Cd and 3 ppm in Hg. River runoff is of minor importance as a metal source in the investigated areas. The spatial distribution of trace metals outside the areas directly influenced by sewage discharges is regulated by natural processes such as sediment sorting by grain size. Based on radiometric dating of sediment cores, increases in the trace metal content of bottom sediments near Vladivostok begun in approximately 1945.

A summary of the distribution of trace metals, petroleum and chlorinated hydrocarbons, anionic detergents and nutrients in the coastal zone around Vladivostok is presented. Very high loads of suspended solids, nutrients and pollutants enter with waste waters which might be the main reason for negative changes in the pelagic and benthos biocenoses. Phytoplankton productivity has doubled during the last decade. ‘Red tides’ in the coastal zone became usual. The structure and productivity of bottom communities also changed drastically.

Data on the distribution of anionic detergents and petroleum hydrocarbons in the northwest Pacific surface waters are presented. Higher concentrations of these pollutants were observed in the Sea of Japan and in the Kuroshio region. The average content of total non-polar petroleum hydrocarbons, measured by IR spectrophotometry, was decreased from 26 ppb in 1980–1982 to 15 ppb in 1986–1988.

Data on distribution of chlorinated hydrocarbons in coastal bottom sediments of different areas of the Japan Sea are presented. Results obtained during the autumn 1994 expedition in Peter-the-Great Bay were compared with the data of previous surveys in the D.P.R. Korea coastal zone and Tatarsky Strait (Sakhalin Island). Concentrations of DDT metabolites and HCH isomers appear to be related mainly to pesticide usage in agriculture. Mean concentrations of total DDTs decreased from 12.5 ng g(-1) in the D.P.R.K. coastal zone to 2.2 ng g(-1) at Sakhalin Island shelf, whereas total HCH concentrations decreased from 3.4 to 0.4 ng g(-1). Differences in chemical composition of pesticides used in the D.P.R.K. and Russia were evident. The importance of further monitoring of persistent organochlorines in bottom sediments and the need for regulation of wastewater discharges is stressed.