The pollutant density in the Songhua River, northeast China, has lowered sharply as the pollution slick passes through Jiamusi, the second largest city on the river's lower reaches, top environment official Zhou Shengxian said Saturday.

Zhou, the newly appointed director of the State Environmental Protection Administration, oversaw the monitoring work at the Dalai post in the upstream of Jiamusi City Saturday morning.

Nitrobenzene density at the Dalai monitoring post measured 0.261 mg per liter Saturday morning, sharply down from 0.581 mg per liter reported at the Sujiatun post further upstream.

As of 8:00 AM, the maximum nitrobenzene density at the Jiamusi post measured 0.173 mg per liter and in a while reduced to 0.162 mg per liter. The local environment watchdog said the density will continue to fall when the pollution belt arrives at the downstream city of Tongjiang, where the Songhua River joins the Heilongjiang River that flows into Russia.

Zhou has urged the local environmental protection departments to continue water quality surveillance in order to ensure safety of drinking water. "We should also start appraising the impact of the pollutants on the ecosystem and work to minimize such impact."