So far, three tests exist for the system. One looks for nickel, which can be an environmental pollutant.

到目前为止，这个系统已经有三种测试了。第一种是寻找镍元素，这可以用来进行环境污染检测。

Most electricity is created by burning fossil fuels such as coal, which releases many environmental pollutants, including mercury.

大多数电力是通过燃烧煤炭等化石燃料产生的，煤炭会释放许多环境污染物，包括汞。