Seasonal Variation Mechanism of PHC Content in the Surface and at the Bottom

Based on the survey data of Jiaozhou Bay in 1992, the vertical distribution and seasonal variation of PHC in surface and bottom waters of Jiaozhou Bay were studied, and the seasonal distribution, variation range and horizontal distribution trend of PHC content in the surface and bottom waters were determined. The results showed that PHC content in the surface and at the bottom of the whole water body from central Jiaozhou Bay to the northern part of the bay mouth of Jiaozhou Bay in May ranged from 0.006mg/L to 0.070mg/L, which constituted a slight pollution there. In August and October, PHC content in the surface of the water body of Jiaozhou Bay ranged from 0.019mg/L to 0.075mg/L, which didn't constitute pollution; PHC content at the bottom of the water body of Jiaozhou Bay ranged from 0.007mg/L to 0.047 mg/L, which didn't constitute pollution. From May to October, the level of PHC content in the surface of the water body of Jiaozhou Bay from low to high respectively appeared in the summer, the spring and the autumn; The level of PHC content in the bottom waters of Jiaozhou Bay from low to high respectively appeared in the summer, the autumn and the spring. The seasonal variation mechanism of PHC content showed that the PHC content in the surface was not subject to season but PHC content in the sources, and PHC content at the bottom was not subject to season but the accumulation and dilution effect of the PHC descending from the surface to the bottom. In terms of the scale of variation, the variation range of PHC content in surface and at the bottom of the waters in Jiaozhou Bay in May, August and October were basically the same. Moreover, the level of PHC content in the surface was relatively high and that at corresponding bottom was relatively high; the level of PHC content in the surface was relatively low and that at corresponding bottom was relatively low. In terms of the spatial scale, the horizontal distribution trend of PHC content respectively in the surface and at the bottom of the whole water body from central Jiaozhou Bay to the northern part of the bay mouth of Jiaozhou Bay in May, August and October were same. Moreover, the horizontal distribution trend of PHC in the surface and at the bottom were same when there was transportation of PHC from any source.