China has initiated a program to evaluate the ecological impact of the Songhua River water pollution and put forward countermeasures, a senior environmental official said in Beijing on Tuesday.

The evaluation program is "an urgent and arduous job" that needs the joint efforts of related departments, Zhu Guangyao, deputy director general of the State Environmental Protection Administration (SEPA), said.

More than 100 researchers from 20 institutions including the Chinese Academy of Environmental Sciences (CAES) and the prestigious Tsinghua University have been sent by the State Council, China's cabinet, to Jiamusi, a city downstream of the Songhua River in northeast China's Heilongjiang Province.

The program, initiated by SEPA, is composed of 14 task forces that have been ordered to prepare plans to deal with issues such as the movement and chemical breakdown of pollutants, the absorption of pollutants after freezing, the stagnation of the pollutants, and their impact on the environment, drinking water and fishery security, Liu Zhengtao, chief researcher of the CAES, said.

Liu said that they are mainly using stalk and straw for absorbing pollutants due to the high cost of activated carbon.

"Experiments have proven that stalk and straw contain a large amount of organic carbon and are very good for the absorption of nitrobenzene," he said.

Continuous monitoring has shown that the nitrobenzene density in the Songhua River has dropped by a large margin, Zhu said, who is also deputy head of the investigation team designated by the State Council to deal with the pollution crisis.

Explosions in a chemical plant on November 13 in Jilin Province spilled about 100 tons of nitrobenzene into the Songhua River, forcing the city of Harbin to cut off its water supply for five days.

SEPA reported on Tuesday that the nitrobenzene density has continued to drop at Jiamusi, some 244 km upstream from the city of Tongjiang, where the river joins the Heilongjiang River and flows into Russia.

The investigation team, formed on December 6, is looking into the cause of the chemical plant blast and why the plant's safety mechanisms failed to prevent the benzene from being discharged in to the river.

It will also find out who should be held accountable for the accident.

The chemical plant operates under the Jilin subsidiary of China National Petroleum Corporation.

(Xinhua News Agency December 14, 2005)