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Accurate dynamic modeling of landslides could help understand the movement mechanisms and guide disaster mitigation and prevention. Discontinuous deformation analysis (DDA) is an effective approach for investigating landslides. However, DDA fails to accurately capture the degradation in shear strength of rock joints commonly observed in high-speed landslides. In this study, DDA is modified by incorporating simplified joint shear strength degradation. Based on the modified DDA, the kinematics of the Baige landslide that occurred along the Jinsha River in China on 10 October 2018 are reproduced. The violent starting velocity of the landslide is considered explicitly. Three cases with different violent starting velocities are investigated to show their effect on the landslide movement process. Subsequently, the landslide movement process and the final accumulation characteristics are analyzed from multiple perspectives. The results show that the violent starting velocity affects the landslide motion characteristics, which is found to be about 4 m/s in the Baige landslide. The movement process of the Baige landslide involves four stages: initiation, high-speed sliding, impact-climbing, low-speed motion and accumulation. The accumulation states of sliding masses in different zones are different, which essentially corresponds to reality. The research results suggest that the modified DDA is applicable to similar high-level rock landslides. [ABSTRACT FROM AUTHOR]

Comprehensive assessment of heavy metals and environmental factors on soil bacterial communities in YRD are still limited. In this study, the heavy metals and bacterial community compositions of soil samples from different land use types in YRD were analyzed. The EF, Igeo and PLI assessment results indicated that severe heavy metal pollution was observed in crude oil contaminated soil samples. Moreover, the highest bacterial community richness was observed in soil samples of cotton field, while the richness was lowest for soils around a chemical factory. The bacterial community composition and structure were different among different land use types in YRD, which was consistent with beta-diversity indices. Results showed that the dominant bacterial phyla in YRD soils were Proteobacteria, Chloroflexi, Actinobacteria and Acidobacteria. Redundancy analysis (RDA) showed that the nutrients (SOM, TC, TN and TK) and heavy metals (Cd, Zn, Cu and As) had important effects on soil bacterial communities. Furthermore, the resistant bacteria strains may have great potential for remediation of contaminated soils. Therefore, the present study contributes to a deeper insight into the crucial influencing factors on bacterial community structure in soil samples of YRD, which may provide early warnings of environmental pollution and ecological destruction of ecosystems. [ABSTRACT FROM AUTHOR]

Rapid development of industry and agriculture over the past decades have caused serious environmental impacts on the local environment. However, the spatial distribution, sources and risk assessment of seldom monitored trace elements (SMTEs) in the surface soils of Yellow River Delta (YRD) have rarely been reported. In this study, thirty surface soil samples in YRD were collected, analyzed to determine concentrations of 17 SMTEs, and evaluated based on enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF) and pollution load index (PLI). Spatial distribution results indicated that relatively high contents of SMTEs in YRD mainly occurred in the western part and oil field pumping units, which was very likely related to petroleum exploitation and refining industries. In line with spatial distributions, the assessment results using EF, Igeo, CF and PLI observed potential contamination for sampling site f4, f5, f8, f13, f14, f18, f23, f30, f32, f36, f37 and f38, and reported obvious enrichment of Cs, Sn, Th, Tl and U for the surface soils of YRD. According to the multivariate statistical analysis results, 17 kinds of SMTEs could be divided into three clusters and the origins of SMTEs may differ for different clusters. Our results indicated that PC1 scores could be regarded as an "anthropogenic impact factor" and an important proxy to represent possible contamination from SMTEs in YRD. This study provides important information for the contamination status of SMTEs in the surface soils of YRD. [ABSTRACT FROM AUTHOR]

The reactivation of coüuviai Landslides in reservoir banks poses a serious threat to the safety of hydropower projects and nearby towns. This study aims to research the morphological evolution of this type of landslides under the action of reservoir water and the impact of morphological evolution on landslide stability. The study focused on the Yulinerzu landslide, a large reactivated colluvial landslide in the Xiluodu Reservoir, China. Field surveys were conducted to analyze the geological structure of the landslide. In situ monitoring and surveys were used to obtain the deformation characteristics and morphological evolution of the landslide. A combined seepage-slope stability analysis was conducted to reveal the deformation mechanism. The results show that the reactivation of the Yulinerzu landslide is dominated by reservoir water fluctuations rather than rainfall. The underlying geological condition of the colluvial landslide is its hydrogeological structure, which causes the landslide to deform in a step-like manner during reservoir operation. With the accumulation of displacement and morphology evolution, the landslide displayed self-stabilizing characteristics. Therefore, in the stability analysis and risk assessment of large deformation landslides, it is essential to take into account not only the hydraulic effects of reservoir fluctuation but also the evolution of landslide morphology. [ABSTRACT FROM AUTHOR]

The distribution of polycyclic aromatic hydrocarbons (PAHs) and halogenated PAHs (HPAHs) in surface soils from the petroleum industrial area of the Yellow River Delta (YRD) in China were investigated. The total concentrations of 16 PAHs ranged from 19.6 to 1560 ng/g, while 22 HPAHs ranged from 2.44 to 14.9 ng/g. Moreover, a high degree of spatial distribution heterogeneity was observed for both PAHs and HPAHs, which is likely attributed to the distinct industrial activities in studied area. The combustion of biomass and petroleum were identified as primary sources of soil PAHs and HPAHs in the YRD. Furthermore, benzo[ b ]fluoranthene, benzo[ k ]fluoranthene, and benzo[ g , h , i ]perylene exhibited high ecological risks (with risk quotients of 1.47, 1.44, and 1.02, respectively) in specific sites within the YRD. Considering the high toxicity of HPAHs and their potential joint environmental effects with PAHs, continuous attention should be directed towards the environmental risks associated with both PAHs and HPAHs. [Display omitted] • Co-occurrence of PAHs and HPAHs was found in soil in Yellow River Delta. • Industrial activities resulted in spatial heterogeneity of PAHs and HPAHs in soil. • Biomass and petroleum combustion are primary sources of soil PAHs and HPAHs. • Benzo[ b ]fluoranthene poses high ecological risks in studied areas. [ABSTRACT FROM AUTHOR]

The Yellow River Delta (YRD) is the second largest petrochemical base in China and the impact of human activities has been continuously increasing in recent decades, however, the contamination status of seldom monitored trace elements (SMTEs) in YRD has rarely been reported. This study evaluated the levels, vertical distributions, contamination status and sources of SMTEs in soil samples of three different land use types in YRD. The results indicated that the vertical distributions of SMTEs contents showed a gradually upward increasing trend for the soil profiles of black locust forest, while the SMTEs contents displayed a gradually upward decreasing trend for the soil profiles of cotton field. However, the SMTEs contents in the oil field area showed no significant difference among different depths. The vertical distributions of SMTEs were very likely related to the anthropogenic disturbance in the later stage. The environmental pollution status assessment of SMTEs showed obvious enrichment of Cs, Sn, and U in the soils of YRD. Moreover, the potential source analysis based on multivariate statistical methods indicated that Ga, Rb, Cs, Sc, Sn, Tl, Be, Bi, Ca and Mo were clustered together and positively correlated with Al, Fe, Mg and K, and may be mainly associated with geochemical weathering process, while the Ce, La, Th, U, Nb, Ta, and Hf may be impacted by both natural process and human activities. Though the SMTEs pollution status was not very serious, our results highlighted the non-negligible influence of anthropogenic activities on vertical distributions of SMTEs in three different land use types from YRD. Our results provide valuable information for understanding the vertical distribution and pollution status of SMTEs in YRD. • Non-negligible influence of anthropogenic activities on vertical distributions of SMTEs in YRD • SMTEs displayed an upward decreasing trend for the soil profiles of cotton field. • Obvious enrichment of Sn, Cs and U was observed in YRD soils. • Sources of most SMTEs are mainly related to the geochemical weathering process. [ABSTRACT FROM AUTHOR]