Land Ministry to map the extent of soil contamination by heavy metals

The Ministry of Land and Resources is compiling a nationwide "pollution map" to gauge the level of heavy-metal contamination in soil due to human activities, according to Xinhua.

This undertaking includes collecting soil samples from across the country and testing levels of 78 chemical elements found in both topsoil - less than 25cm deep - and in samples from at least a metre underground, the report said, citing the ministry and its affiliated China Geological Survey.

No timetable for the survey was given, nor did the report say whether the map would be publicly released amid mounting concerns over food safety due to soil contamination. Recent reports said that almost half of the rice in Guangzhou was found to be tainted with cadmium, a heavy metal that can damage kidneys and bones.

Thus far, researchers have found that soil collected in parts of the mid- and lower reaches of the Yangtze River contained high levels of cadmium, mercury, lead and arsenic. The report also said that some cities were found to have "abnormal levels of radiation", without elaborating.

Meanwhile, heavy-metal pollution in soil has been expanding in densely populated eastern China, compared with samples collected in the 1990s, according to Xinhua.

But some analysts have voiced doubts about the new survey. Mainland authorities have kept under wraps the soil-pollution data gathered during a five-year nationwide investigation, dubbing the information a "state secret".