The results showed that the radioactivity levels of each nuclide in Yangtze River water system were still lower than that of background, and did not cause contamination.
结果表明，各核素均未对长江造成污染，长江水系放射性浓度仍在本底水平。
2
The results showed that the raioac-tivity levels of each nuclide in Yangtze River water system were still lower than that of background, and did not cause contamination.
结果表明，各核素均未对长江造成污染，长江水系放射性浓度仍在本底水平。
3
We monitored some background DNA in faecal DNA, and discussed potential risks from background DNA contamination, such as genomes of bacteria, virus, parasites and prey.