In a country already plagued by widespread air and water pollution, an investigation by China's environment ministry has found that as much as 16 percent of soil contains higher-than-permitted levels of pollution.
The survey tested soil samples taken across 6.3 million square kilometers (2.4 million square miles) of China's territory, roughly two-thirds of the total, the Ministry of Environmental Protection said in a statement on its website on Thursday.
"The survey results show that [the outlook for] the national soil environment is not optimistic," the ministry said.
"There is heavy soil pollution in some areas, while the environmental quality of cultivated soil is worrying, in particular, the issue of environmental issues from mining and industrial waste," the statement said.
But environmental campaigners said they remain suspicious of government pollution figures.
"These figures aren't accurate, because at least two thirds of China's agricultural land is polluted," environmental activist Zhang Changjian told RFA's Mandarin Service.
"All of the major rivers are polluted, and a lot of agricultural land uses that water for irrigation, which means it must also be polluted," Zhang said, in response to the ministry's report.
Biggest culprit
Zhang said the chemical industry is the biggest culprit in water and soil pollution, but also pointed the finger at waste produced by humans going about their daily business.
"The main pollution comes from factories, as well as sewage and trash disposal," he said. "There is very serious pollution coming from residential waste now."
According to the report, more than 19 percent of agricultural soil samples had pollution levels exceeding permitted limits, compared with 10 percent of samples taken from forests, and 10.4 percent of those taken from grasslands.
Soil across China is contaminated with cadmium, mercury, arsenic, copper, lead, chromium, zinc and nickel, the report found, with 82.8 percent of samples containing traces of these pollutants.
"Soil contamination and excessive pollution is mainly caused by mining and industry, agricultural production and other human activities," the ministry statement said.
'Step forward'
Beijing-based rights lawyer Dong Zhengwei welcomed the report, which comes after he made a formal information request for the government to publicize the results of the survey, which began in 2005.
"For them to make this public is a definite step forward, although the figures are really only preliminary ones," Dong told RFA.
"But I don't think this step forward means that the environmental situation will see any major improvement."
He also said he has doubts about the overall figures of 16.1 percent.
"Judging from the situation over the past few years, I think the problem is much more serious than that," Dong said.
The ruling Chinese Communist Party is currently working on a raft of measures to tackle the problem, and will accelerate new legislation, the ministry of environmental protection said.
Transparency
Last May, authorities in the southern province of Guangdong named and shamed rice producers whose products contained "excessive amounts" of cadmium, amid growing public pressure for transparency over the scandal.
Of 18 batches of rice tested during quarterly spot-checks, eight were found to contain excessive amounts of the carcinogenic heavy metal, media reports said at the time.
However, expert studies revealed as early as 2011 excessive cadmium levels in around 10 percent of rice sold across China.
Campaigners say that China already has an exemplary set of environmental protection laws, but that close ties between business and officials mean that it is rarely enforced at a local level.
Zhang said levels of public awareness remain low.
"On the one hand, local residents don't have much environmental awareness; it's terrible, while on the other, the government doesn't do enough environmental work to improve things," he said.
Reported by Yang Fan for RFA's Mandarin Service. Translated and written in English by Luisetta Mudie.