Ultra-fine coatings on sediment grains influence nitrate and sulphate storage in soil
Tiny sediment grains are covered with a very fine-grained, complex mixture of minerals in an open fabric that results in a large surface area in contact with water between the grains. Scientists at the U.S. Geological Survey (USGS) are studying this microscopic layer and finding that the mineral composition of these coatings on sediment grains in the unsaturated zone (i.e., between land surface and the water table) can have a substantial effect on the retention of nitrate and sulphate. Their findings are particularly important for evaluating the long-term effects of agriculture on water quality, as the storage of these common components of fertiliser in the unsaturated zone can affect the quality of shallow groundwater for many years after fertiliser application ceases...