The study looked at how different soils in China absorb mercury and how adding organic matter affects this process. They tested 26 soils and found that the amount of mercury absorbed varied based on soil properties like organic matter, cation exchange capacity, nitrogen, and sulfur. When they added organic matter from wheat straw or swine manure, the soils absorbed less mercury. In most cases, swine manure had a bigger impact on reducing mercury absorption than wheat straw. Soils with low or high pH, less organic matter, low cation exchange capacity, and less free iron/aluminum oxide are at higher risk of mercury contamination when organic matter is added.