Sand is a rocky substance composed of grains that range in size from.0063 to 2 millimeters. Smaller particles are known as silt and larger particles are gravel. It is a natural material and is formed from grains of whatever rocks and materials are present in the local area. The grains form from natural erosion over time. Coastal and marine sand are formed from the skeletal remains of marine life, and have different compositions from sands found in inland areas.
The main component of sand is silicon dioxide in the form of quartz. Sand also contains several minerals, including feldspar, tourmaline, olivine and even gemstones. The actual composition of sand is largely dependent on its environment. Volcaniclastic sands are formed from volcanic rocks, quartzose sands contain mostly quartz, sedimenticlastic sands are formed from sedimentary rocks and marine sands are mostly composed of limestone from decayed corals, shells and marine rocks. Sand also contains decayed matter from the flora and fauna that occupy the area, as well as atmospheric gases.
Nitrogen gets deposited into sand through natural means, such as through the biological activity of bacteria on organic matter present in the sand granules. Trees and shrubs that grow in the sand also cause deposition of atmospheric nitrogen through their normal biological processes. Atmospheric nitrogen is also deposited in sand in wet, dry and gaseous means as nitrogen is a component of air. Sea birds and local wildlife also introduce nitrogen into sand through their droppings, which contain ammonia (NH3).
Nitrogen deposition in sand is considered a polluting factor. According to the Centre for Hydrology and Ecology, it is thought to be a major factor in the decline of some species in studied sand dune ecologies. Nitrogen is an important nutrient for plants and affects plant growth rates in sandy ecosystems. Nitrogen deposited in sand may eventually end up in marine life, such as phytoplankton, and affect marine ecosystems.