Dianchi Lake in China is very polluted. Scientists studied the phosphorus and nitrogen in the lake's sediments. They found that most of the phosphorus in the sediments is in a form that can be used by plants. They also discovered a type of phosphorus that can easily move into the water. This phosphorus can contribute to the lake's pollution. Additionally, the sediments in the lake contain a lot of nitrogen that can also add to the water's pollution.