September 6, 2004
The Ministry of the Environment (MoE) compiled results of marine environment monitoring conducted in FY 2002. The purpose of this survey is to apprehend status of marine pollution by surveying impacts on water quality and bottom sediment by pollution from land-based sources, quantity of marine litter, concentration of pollutants accumulated in marine organisms, etc at fixed monitoring points in the sea areas surrounding Japan.
The samples of water, bottom sediment and marine organisms were collected from water off Tokyo Bay and Toyama Bay between November and December 2002 and analyzed pollutants of them. Compared to the past survey no drastic changes in marine environment were observed. The MoE will continue the survey to grasp yearly changes of marine environment and to have comprehensive analysis.
The MoE has been implementing "Marine Environment Monitoring Survey" since FY 1998, when the United Nations Convention on the Law of the Sea came into effect. The survey conducted in the past had covered water quality and bottom sediment and was enhanced to the current survey by adding marine ecosystem as subject. This survey is conducted on the basis of the result obtained from the "Investigation of Pollution in the Adjacent Seas of Japan," conducted from FY 1975 to FY 1994. The present survey is planned so that monitoring will have a tour of sea areas surrounding Japan within 3 to 5 years.
<Summary of survey results>
||Water quality, bottom sediment, drifting plastics
||Off Tokyo Bay
||Off Toyama Bay
||Marine organisms (3~5 kinds including blue mussels)(Fig.2)
||Oyashio Current area
||Kuroshio Current area
||East China Sea area
||Japan Sea area
The major purpose of this survey is to grasp the impact of land-based pollution sources to the marine environment. The status of the impacts could be assessed as follows.
Among the substances analyzed in this survey, environmental quality standards (EQSs) have been set for six substances (cadmium, lead, total mercury, PCBs, nitrate and nitrite nitrogen and dioxins) in sea water. The measurement values of them were lower than the EQSs.
The impact of land-based pollution was suggested for polychlorinated biphenyls (PCBs), dioxins, and hydrocarbon.
Measurement values were higher in inner section than the offing both in Tokyo Bay and Toyama Bay.
||Dioxins and hydrocarbon
Measurement values were generally low except Tokyo Bay where concentration at the inner section was higher than the offing. On the contrast, values in Toyama Bay were constantly low in all sampling points.
Among the substances analyzed, provisional removal standards are set for mercury and PCBs in the bottom sediment and EQS is set for dioxins. The values obtained in the survey were assessed to be lower than these standards. (For provisional removal standards for mercury in bottom sediment, standard values were obtained from the coastline where the sampling points were set.)
The impact of land-based pollution was also suggested for some heavy metals including lead and cadmium, PCBs, and dioxins.
Measurement values of cadmium and lead were higher in costal area than the offing in both Tokyo Bay and Toyama Bay. Total mercury was higher in coastline than the offing in Tokyo Bay, but values in Toyama Bay were constantly low from coast to the offing.
||PCBs, dioxins, and benzo(a)pyrene
Measurement values were higher in coastal area compared to the offing in both Tokyo Bay and Toyama Bay.
Measurement values in coastal area were higher than the offing in Tokyo Bay. On the other hand, values were low in all the sampling points in Toyama Bay.
||Linear alkylbenzene and coprostanol
These two substances are found in sewage and night soil and were surveyed to determine the impact of sewage and night soil on marine environment. These two substances were detected in all sampling points. The measurement values of the offing were same as the value taken at ocean dumping point. In this respect, data shall be further collected and analyzed to determine whether these values indicate the impact of ocean dumping or land-based pollution, or natural background.
||Concentration in marine organisms
Blue mussels, benthic sharks, cuttlefish and pacific cods were surveyed from FY 1998 to FY 2002 and crustacea were surveyed from FY 2000 to FY 2002. From these surveys, obvious yearly changes were not observed. The survey shall be continued to accumulate more data to analyze the status.
Marine litter was collected from sea surface by net. In Tokyo Bay, quantity of collected floating plastics was highest at the sampling point located outside the bay. In Toyama Bay, marine litter was most frequently observed in the sampling points closer to the coast. Although the average quantity was smaller compared to the results obtained at the same sampling points in 1999, this may be caused by unfavorable conditions happening during sampling. Comparison between sampling points were possible but yearly fluctuation could not be assessed.
There is possibility of continued pollution and increasing load of pollution by pollutants surveyed in the monitoring, but on the other hand natural decrease by dispersion may be possible which makes the future assumption difficult. Therefore, it is important to grasp the yearly changes by continuing monitoring in planned manner.
In order to apprehend comprehensive marine environment of sea area in Japan's jurisdiction, it is necessary to grasp status of marine pollution originating from vessels as well as pollution from land-based sources.
Regarding ocean dumping of land originated wastes, the Law Relating to the Prevention of Marine Pollution and Maritime Disaster was partially amended complying with 1996 Protocol to the London Convention. With this amendment, ocean dumping of wastes shall be under license system by May 2007 and environmental impact assessment to the marine environment shall be required for filing application for a license. In order to have precise enforcement of this system, it is indispensable to apprehend the changes in marine environment. In this respect, it is especially essential to construct a system to monitor regularly the environment of the sea area where marine dumping takes place.