VOA慢速英语:Study: Mississippi River Overwhelmed by Agricultural Chemicals

短语讲解：

1. As the algae dies, it sinks to the bottom of the river where it breaks down or decomposes.

break down 失败; 划分（以便分析）; 损坏; 衰弱下来
例句：Cellulose is hard to break down.
纤维素是很难分解的。

2. Farmers say these chemicals must be used to produce enough food for a growing world population.

be used to 可用于
例句：A stopwatch is used to obtain the optimum procedure. 
秋表用来控制最佳工作进程。 

3. He says farmers may be able to better control the amount of nitrate fertilizer they put on fields.

be able to 能，会; 能够
例句：How soon will china be able to clean up its air?
中国能在多短时间内将空气变清洁？

4. There is really a question here: can you maybe [reduce the amount] and get close to the same level of yield without having such a negative impact?

get close to 接近; 附; 迫临
例句：We should seize every opportunity to get close to the masses. 
我们要抓住一切机会来接近群众。