Abstract
To examine the behavior of organic matter and elements derived from terrestrial ecosystems as a result of river becoming estuarine, a model experiment was conducted by mixing suspensions of peat, litter, paddy soil, and manure samples with several concentrations of sea water. Elements were fractionated into a free form and three bound forms with water soluble organic matter including colloids difficult to precipitate (WSOM), insoluble organic matter (TOM), and clay particles (CP). The decrease in organic C after mixing with sea water was largest for the peat sample (> 90%) and smallest for the manure sample (7%>). Large percentages of P, which mainly existed in the bound forms with IOM and WSOM, and Fe, which mainly existed in the bound forms with CP, precipitated at 5% sea water. The percentage precipitation of elements were also larger for the peat sample and smaller for the manure sample. The percentage of possibility that these elements were precipitated oncewith the succeeding the free form was larger with Mn and Zn than with the other elements, and further increased with the increase in mixing ratio of sea water for some of samples, suggesting the possibility that these elements have been precipitated and are subsequently exchanged by ion exchange. The potential to supply bioelements in soluble form to coastal areas was greater for the paddy soil sample and smaller for the litter sample. Thus, it was considered that the concentration and the form of elements in estuarine water vary depending on the land use forms in watershed areas.
