Soil-Borne Particles and Their Impact on Environment and Human Health

Abstract

Dust particles can consist of either natural soil-borne particles or of particulate matter from human activities, or both of them. Particulate matter is a complex mixture of extremely small particles and liquid droplets consisting of soil or dust particles, metals, organic chemicals, and acids. Naturally generated particles consist of weathered rock materials, dryland soil and sediment materials, biogenic fibres and residues from forest fires, and ash developed during volcanic eruptions. World dust emissions from drylands amount to about 5 billion Mg per year. Dominant dust sources around the world are almost wholly in or adjacent to the great drylands of the northern hemisphere. The greatest of these includes a large belt from the western Sahara to the Yellow Sea, across North Africa, the Middle East, northwest India, and central and eastern Asia. Saharan dust, driven by the northeast trade winds, takes about a week to cross the Atlantic Ocean, reaching northeastern South America the Caribbean, Central America, and the southeastern USA. The mid latitude deserts of Asia are a source of substantial airborne dust, especially during spring and early summer. Mongolia and the Tarim Basin-Taklamakan Desert are the two major dust sources of China. They are also of worldwide importance, as fine dusts from these regions have been traced to North America, Greenland and Europe. Other notable sources of dusts include the Great Basin of the USA and, in the southern hemisphere, central and northern Argentina, parts of southern Africa and East-central Australia. Former lake basins are major sources of fine, readily wind-entrained mineral dusts, which may include salts and elevated levels of toxic elements. For example, the Bodele depression in Chad (North Africa) and the numerous lake depressions in central Asia (e.g. Aral Sea region) and northern China are major dust sources of global significance. Sea spray produces aerosols containing particles that are commonly of salt, but can also contain radionuclides.