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A recent slow-moving landslide occurred on September 27, 2020, in Chang Nong Village (24°21′ 25” N, 109°09′ 27″ E), Guangxi Province, China. The precursor activity of the landslide started approximately 5 months before landslides with cut slope construction work at the toe part of a mountain. Given this precursor, engineers set a counterweight berm at the slope’s toe for expanding toe weight to avoid further deformation. However, the measure had a negative effect on the stability of landslides, as the stabilizing berm blocked off natural groundwater channels located at the slope toe, leading to further deformation of landslides. Fortunately, monitoring of the creeping downslope movements of the landslide mass began, and an early warning was issued before the event. Thus, no casualties were caused by the slow-moving landslide; however, 72 houses were destroyed. In order to deduce the Chang Nong Village landslide failure mechanism, the geological characteristics, slope excavation schemes, rainfall data statistics, and landslide deformation patterns were systematically investigated based on unmanned aerial vehicle (UAV) photography, field investigation, displacement monitoring, and laboratory testing. The results show that colluvial stratigraphic structures and poor rock mass properties are the internal factors that induced landslides. The combined effects of prolonged heavy rainfall and the repeated fluctuation of groundwater caused by improper activities, including toe excavation and counterweight filling, are external factors that directly triggered the landslide. This case discusses how improper engineering treatment influences groundwater changes in landslide areas and supports the importance of prevention measures for colluvium landslides.

Toxic heavy metal containing Cr(VI) species is a serious threat for ecological environment and human beings. In this work, a new mussel-inspired polydopamine microsphere (PDA-sphere) is prepared through in situ oxidative polymerization at air condition with controllable sizes. The adsorption of Cr(VI) ions onto PDA-sphere is highly pH dependent with the optimal pH ranging from 2.5 to 3.8. A rapid Cr(VI) removal can approach in 8 min for equilibrium. More importantly, the prepared materials exhibit a remarkable sorption selectivity, coexisting SO 4 2− , NO 3 − and Cl − ions at high levels; The applicability model further proves its effective performances with treated capacity of 42,000 kg/kg sorbent, and the effluent can be reduced from 2000 ppb to below 50 ppb, which meets the drinking water criterions recommended by WHO. 1 kg sorbent can also purify approximately 100 t Cr(VI) contaminated wastewaters basing on the wastewater discharges of China. Such capacity for application ranks the top level for Cr(VI) removal. Additionally, the exhausted materials can be well regenerated by binary alkaline and salts mixtures. Such efficient adsorption can be ascribed to the well-dispersed morphology as well as the strong affinity between Cr(VI) and catechol or amine groups by XPS investigation. All the results suggest that polydopamine microspheres may be ideal materials for Cr(VI) treatment in waters.

In this work, we successfully prepared the mussel-inspired polydopamine microspheres (PDA-Ms) with controllable sizes, through a facile self-oxidative polymerization method. The prepared PDA-M biomaterial with environmentally benign properties exhibits efficient lead(II) sequestration against high salts of competitive Ca(II), Mg(II), or Na(I) ions. It reveals 30 times greater than the commercial ion-exchanger 001x7 by selectivity evaluation. Kinetic results show that an exceedingly rapid lead(II) uptake can be achieved below 1 min. More attractively, the prepared PDA-Ms further exhibit the distinguished application ability with superior treated capacity of ∼42000 kg contaminated water/kg sorbent, and the effluents can be reduced from 1000 μg/L to below 10 μg/L, reaching the drinking water standard (WHO), which is equal to 200 times greater than commercial ion exchanger resin (∼210 kg) and granular activated carbon (∼120 kg). In addition, the exhaust PDA-M material can be well regenerated and repeated use ...