Based on the seismic profile, analogue modeling and discrete element modeling method were carried out to study the deep genetic mechanism of the gravity instability structure and evolution process of the salt diapirs in the contractional zone of central Lower Congo Basin in the passive continental margin of Angola in West Africa. The effect of salt diapir activity on the migration of the sedimentary center of the mini-basin between the diapirs was further studied. The results show that the evolution process of salt diapirs in the contractional domain of central Lower Congo Basin is related to the stress conditions. In the early stage, it was mainly controlled by the effect of gravity spreading, and in the later stage, it was controlled by the effect of squeezing. According to the comparison between the results of analogue modeling and discrete element modeling and the seismic sections, the evolution process of salt diapir can be divided into the following three stages: 1) The early stage, the extended reactive diapir stage; 2) The mid stage, the passive diapir stage; 3) The late stage, squeezed active diapir stage. The sedimentary center of the mini-basin between the salt diapirs migrated to the diapirs with strong activities during the same period.

This study takes the Shenzhen Bay Basin as the research object, based on the combined model of rainfall runoff pollution, overflow from sewer interception system and hydrodynamic water quality in the bay, the temporal and spatial variation of overflow pollution and its effect on water quality in the bay were analyzed. The results show that in the whole year, the main pollution sources of the basin are the pollution of the wastewater treatment plant and the overflow pollution. The overflow pollution accounts for about 30% of the total pollution load, rises to about 50% in the rainy season, and becames the main pollution source in the rainy season in Shenzhen Bay Basin. The overflow pollution load in rainy season accounts for more than 85% of the total overflow pollution load in the whole year. The pollution load of overflow increases with the rainfall. When the rainfall intensity is similar, the longer the dry time before rain, the greater the overflow pollution load. In terms of water quality in the bay, the water quality in the Inner Bay is worse than that in the Outer Bay and the fluctuation is more obvious, In rainy season, the water quality in Inner Bay and Middle Bay is worse and fluctuates more than that in dry season. In the event of rain, the water quality fluctuation in the inner bay was most seriously affected by the impact of overflow pollution, while the middle and outer bays was mainly affected by the tidal action. When the return period of rainfall is 0.25 to 0.5 years, the water quality in Shenzhen Bay exceeds the standard most obviously, and the duration of water quality affected by overflow pollution is 12 to 20 days.