These are amounts of substances, or pollutants, within something.

它们是某物内物质或污染物的含量。

He means amounts of substances, pollutants, found in something, which here is the air.

他指的是在某物中发现的大量物质，污染物，这里是指空气中。

An " atom" (atom) is the smallest amount of substance that can exist by itself.

一个“原子”（atom）是可以单独存在的最小量的物质。

He said it was one way to reduce concentrations-he means amounts of substances, pollutants, found in something, which here is the air.

他说这是减少浓度的一种方式——他指的是某些东西中发现的物质、污染物的量，这里指的是空气。

I first need to be able to convert the atomic mass of this sugar, into a standard amount of substance.

我首先需要能够将这种糖的原子质量转换为标准量的物质。

You may know how human genes are transferred to host bacterial cells, which then produce large amounts of substances humans require, such as hormones like insulin.

你可能知道人类基因是如何转移到宿主细菌细胞中的，然后细菌细胞产生大量人类需要的物质，比如胰岛素等激素。