In library, the contaminations can be divided into four parts: i. e. chemical contamination, physical contamination, biological contamination and radioactive contamination.

前言： 图书馆内污染物按性质分为化学性污染物、物理性污染物、 生物性污染物和放射性污染物。

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The bean sprout crop that was the source of the outbreak requires a warm and humid environment to grow, which increases the risk of contamination by E. coli and other disease-causing bacteria.

豆芽菜的生长需要温暖潮湿的环境，这正好也适应大肠杆菌的生长，增加了被污染的风险。

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The test is used to detect surface iron contamination, i. e., iron salt residue from pickling, iron tool scratches on the stainless steel surface, iron deposits at weld areas, and iron oxides.

该检测用于检测表面的铁的污染，如浸酸中铁盐残留，不锈钢表面的铁制工具的刮痕，焊接区的铁沉积以及铁的氧化物。

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At least one school district has already warned parents that food served in its cafeterias was recalled because of possible E. coli contamination.

WSJ: Recalled frozen food may have ended up in schools

Rich Products two weeks ago announced a voluntary recall of certain Farm Rich and Market Day brand products because of the possible E. coli contamination.

WSJ: Recalled frozen food may have ended up in schools

On Tuesday, Hudson recalled 20, 000 pounds -- 80, 000 frozen hamburger patties -- after 16 Colorado consumers became sick from grilled burgers linked to E. coli contamination.

CNN: Recall of frozen hamburger patties doubles