Dissolved load

Dissolved load is the portion of a stream's total sediment load that is carried in solution, especially ions from chemical weathering. It is a major contributor to the total amount of material removed from a river's drainage basin, along with suspended load and bed load. The amount of material carried as dissolved load is typically much smaller than the suspended load, though this is not always the case, particularly when the available river flow is mostly harnessed for purposes such as irrigation or industrial uses. Dissolved load comprises a significant portion of the total material flux out of a landscape, and its composition is important in regulating the chemistry and biology of the stream water. The dissolved load is primarily controlled by the rate of chemical weathering, which depends on climate and weather conditions such as moisture and temperature. Dissolved load has many useful applications within the field of geology, including erosion, denudation, and reconstructing climate in the past. Dissolved load is typically measured by taking samples of water from a river and running various scientific tests on them. First, the pH, conductivity, and bicarbonate alkalinity of the sample are measured. Next, samples are filtered to remove any suspended sediments and preserved with chloroform to prevent growth of microorganisms, while the others are acidified with hydrochloric acid added to keep dissolved ions from precipitating out of solution. Then, various chemical tests are applied to determine the concentration of each solute. For example, the concentrations of sodium and potassium ions can be determined by flame photometry, while the calcium and magnesium ion concentrations can be determined by atomic absorption spectrophotometry. Dissolved load can provide valuable information about the rate of soil formation and other processes of chemical erosion. In particular, the mass balance between the dissolved load and solid phase is helpful in determining surface dynamics.