ABSTRACT
It is common practice to accept, as an operational definition, that particulate matter (PM) refers to particles greater than 0.45 µm. By this definition dissolved matter includes particles finer than 0.45 µm, including colloids. Particulate matter is derived primarily from rock weathering processes, both physical and chemical, and may be further modified by soil-forming processes. Erosion subsequently transfers the sediments or soil particles from their point of origin into freshwater systems. During transport, the sediment is sorted into different size ranges and associated mineral fractions until it is deposited on the bottom of the receiving water body. Sediment may then be resuspended, and transported further afield, by intermittent storm activity until it comes to its ultimate resting point or sink, where active sediment accumulation occurs. Modification of the composition of sediments may occur as a result of the input of autochthonous organic and inorganic particles (e.g. calcite, iron hydroxides) generated in the water column and by chemical alterations, especially during periods of deposition.
