The water along its coast is of the open-water type and the range of depth is from 3 to 6 meters. The sediment of the southern part of this area is mud-sand and that of the northern part is mud-gravel.
The results showed that the concentrations of TOC and TN in bottom sediment were increased with pond age, polluting depth were 20-30 cm for clay soil, were 40 cm for silt. The pollution of surface sediment is more serious than that of deep sediment, and pollution of surface sediment of clay soil is more serious than that of silt soil.
Oil concentration in water was determined by two factors. The first was the concentration of the sediment in runoff and the second was the oil pollution intensity of the sediment. Under the experiment conditions, the oil concentration ranged from 1.56 to 5.19 mg/L which could cause serious pollution in runoff.
The reason is likely to the fact that intensive shell aquaculture resulted in organic pollution in sediment, consequently, the abnormal benthic environment promoted the growth and metabolism of microorganisms.
The content of NH4+- N increased with an increase in depth of sediment. On the other hand, the NO3- - N level decreased with increase in sediment depth with invariable NO2- ~ N level.
The sediment energies were 0.71MJ~1.38MJ,which accounted for 3.66%~8.61% of the output energies respectively. The average sediment energy in the polyculture systems was 20.14% less than in the monoculture,whose sediment energy was 1.65MJ.
The variables studied were transport of sand, underlying surface roughness, windblown sediment, wind-sand flow structure, soil mechanical composition and amount of wind erosion.
At a height of 0-20 cm, the height increased while the sediment discharge percent of sand flux decreased; there were significant differences in the sand flow formation under different land-use types.
At the same time, better correlative relationship between runoff and sediment production and rainfall and rainfall intensity were testified by multiple regression, but the correlation decreased gradually with the increase of canopy density of forest.