Effects of PHC on Water Quality of Jiaozhou Bay Ⅳ.Sedim entation Process

Based on the investigation data of PHC content in Jiaozhou Bay, China during 1980 -1981, the distribution of PHC content in the bottom water of Jiaozhou Bay was analyzed. The results showed that PHC content in the bottom water of Jiaozhou Bay varied from 0.028 to 0.147 mg/L. from April to November （except for May） during 1980 -1981, indicating that the bottom water was polluted slightly by PHC. PHC content was affect- ed by the vertical water body effect, so that the minimum of PHC content in the bottom water changed stably. In addition, there were no obvious seasonal variations in PHC content in the bottom water. It reveals that PHC brought by human activity was more than that transported by rivers, so PHC pollution caused by human activity was serious. From the inside water to the outside water, PHC content decreased gradually in April and Au- gust but increased in November, showing the sedimentation process of PHC. The sedimentation process of PHC showed the migration paths of PHC in Jiaozhou Bay in time and space.

The Origin and Preservation of Suspended Barites near the 90°E Ridge in the Northeastern Indian Ocean

Suspended particulate barite crystals were detected in the water columns at four different stations near the 90°E ridge in the Indian Ocean.Four distinct morphological types of marine barites were distinguished:euhedral-subhedral crystals,oval or round crystals,rhombic crystals,and irregular crystals.The barite crystals in the study area are typically fine,with a dominant size of 1–3μm.The vertical distribution of barites is significantly affected by the formation and sedimentation processes.Barites begin to appear at a depth of 30 m and are formed primarily from the surface to the depth of 2000m with a concentration peak at the depth of 200m,where particles are coarser than those in the other layers.The barites begin to settle and dissolve once formed in the water column,resulting in finer barite particles and lower particle concentrations.The formation of barite crystals is related to biological processes associated with the decomposition of barium-rich skeletons in the microenvironment of decaying organic matter that is affected by the primary productivity and dissolved oxygen content in the water column.The dissolving process of barite crystals showed similar variation with the concentration of dissolved barium in ocean water,and the substitution of strontium for barite in crystals promotes the selective dissolution of barite and exerts an important impact on its morphology.It is approximately 33%of barites in the amount and 22%in the concentration to settle to the bottom of the water column compared to that observed in the main barite formation zone.

Non-capacity transport of non-uniform bed load sediment in alluvial rivers

Rivers often witness non-uniform bed load sedim ent transport. For a long tim e, non-uniform bed load transport has been assum ed to be at capacity regime determined exclusively by local flow. Yet whether the capacity assumption for non-uniform bed load transport is justified remains poorly understood. Here, the relative time scale of non-uniform bed load transport is evaluated and non-capacity and capacity models are compared for both aggradation and degradation cases with observed data. As characterized by its relative time scale, the adaptation of non-uniform bed load to capacity regime should be fulfilled quickly. However, changes in the flow and sedim ent inputs from upstream or tributaries hinder the adaptation. Also, the adaptation to capacity regime is size dependent, the finer the sediment size the slower the adaptation is, and vice versa. It is shown that the capacity model may entail considerable errors compared to the non-capacity model. For modelling of non-uniform bed load, non-capacity modelling is recommended, in which the temporal and spatial scales required for adaptation are explicitly appreciated.