Abstract
The present study was carried out to elucidate the effects of storage (freezing and thawing) of polluted water samples on concentration of nutrients and organic matters.
Water sample was collected on 17th May, 1978 at Nogawa River and filtered by Whatman GF/C filters. Concentration of nutrients and organic constituents was immediately analysed for a part of the filtered sample and the residue was stored in a deep-freezer at -20°C. When the frozen sample was thawed at room temperature, suspended particles were observed in the thawed sample. Chemical constituents were determined for filtered and unfiltered samples. The process of freezing and thawing was repeated three times during a series of the present study.
Little differences in concentration of nutrients were observed in unfrozen and frozen samples. It is considered that there is no effect of suspended particles formed during freezing and thawing on determination of nutrient concentration. The amount of suspended organic particles formed during these processes was about 4 mgC/l.
Changes in molecular weight distribution of dissolved organic matter were observed during the process of freezing and thawing. The amount of low-molecular weight fractions (molecular weight less than 500) did not change remarkably and constituted about 20% of the total dissolved organic carbon. However, macromolecular organic fractions (molecular weight greater than 100000), especially proteinaceous materials, were found to decrease after the process of freezing and thawing. Thus, it is considered that high molecular weight fractions are major constituents of suspended particles formed during freezing and thawing processes.
