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Public transport improves mobility and well-being for the rapidly aging population. However, few planning interventions have addressed the urban–rural disparity in bus usage among older adults. Using data from Zhongshan, China, this study adopts the eXtreme Gradient Boosting (XGBoost) model to examine urban–rural differences in the nonlinear relationship between built environment and daily bus usage among elderly adults. The results indicate nonlinearities across all built environment variables and stronger effects of the built environment in rural areas. Distance to transit contributes the most in urban neighborhoods but least in rural ones. Furthermore, dwelling unit density and green space accessibility play the biggest roles in the rural context. Additionally, the most effective ranges of intersection density, land use mixture, and CBD accessibility are greater in rural areas. The findings facilitate fine-grained and diversified planning interventions to facilitate bus usage among older adults in both urban and rural areas. [ABSTRACT FROM AUTHOR]

Human–environment interactions across historical periods in China have been well reconstructed over the past decade; however, few studies have focused on southern China, particularly Hainan Island. This study investigated two sediment cores (cores X1 and X2) collected from the continental shelf off Hainan Island in the northern South China Sea. Combined with geochemical compositions (Al, Ni, Cu, Zn, Cd, and Pb), Sr-Nd isotopes, grain size, and AMS 14C ages, our results showed that Cd and Cu in core X1 and Cd and Pb in core X2 have been mainly influenced by anthropogenic activities since ~4.0 kyr BP. The enrichment factors showed obvious increases starting at ~4.0 kyr BP and were in good accordance with the appearance of abundant archeological sites on Hainan Island. Significant climatic changes (i.e. decreases in the East Asian summer monsoon and increases in El Niño–Southern Oscillation activities) at ~4.0 kyr BP likely promoted more intense, localized human activities, which in turn enhanced heavy metal accumulation in the continental shelf sediments. These results provide new insights into the history of human activities on Hainan Island and indicate that the geochemical compositions of continental shelf sediments have the potential for broadening our knowledge of the human activities and cultural development in tropical areas. [ABSTRACT FROM AUTHOR]

Selected trace elements (As, Cr, Zn, Cu, Cd, Co, Pb and Ni) in 76 surface sediment samples collected from the rivers and the intertidal zone of Jiaozhou Bay (JZB) were evaluated to assess their environmental background values in the JZB catchment. Overall, the sediment quality in the area meets the China Marine Sediment Quality criteria. The background values (ranges) of the elements As, Cr, Zn, Cu, Cd, Co, Pb and Ni were, respectively, 8.28 (4.10–12.46), 67.96 (38.40–97.52), 56.80 (16.42–196.51), 19.13 (5.71–64.06), 0.10 (0.02–0.42), 6.51 (2.08–20.40), 17.97 (12.26–55.84) and 20.69 (10.43–30.95) mg/kg. The background values of most of the trace elements were lower than those in Chinese soil, the upper continental crust, global shales and global preindustrial sediments. The results may assist in defining future coastal and river management measures specifically targeted at monitoring trace element contamination in the JZB catchment. [ABSTRACT FROM AUTHOR]

The heavy metals in surface sediments of the continental shelf of the South Yellow Sea (SYS) and the East China Sea (ECS) collected in 2016 were analyzed to assess the heavy metal distributions, contamination status, and likely sources. The metal concentrations generally met the China Marine Sediment Quality criteria. However, the enrichment factor and geoaccumulation index values clearly showed elevated Cd and Pb concentrations in the region. Cd and Pb contamination occurred mostly to the southwest of the Changjiang River mouth and to the east of the Shandong Peninsula because of rapid economic and industrial development. The results are likely to be useful for authorities responsible for sustainable coastal zone management. [ABSTRACT FROM AUTHOR]

Introduction: Walking plays a crucial role in promoting physical activity among older adults. Understanding how the built environment influences older adults' walking behavior is vital for promoting physical activity and healthy aging. Among voluminous literature investigating the environmental correlates of walking behaviors of older adults, few have focused on walking duration across different age groups and life stages, let alone examined the potential nonlinearities and thresholds of the built environment., Methods: This study employs travel diary from Zhongshan, China and the gradient boosting decision trees (GBDT) approach to disentangle the age and retirement status differences in the nonlinear and threshold effects of the built environment on older adults' walking duration., Results: The results showed built environment attributes collectively contribute 57.37% for predicting older adults' walking duration, with a higher predicting power for the old-old (70+ years) or the retired. The most influencing built environment attribute for the young-old (60-70 years) is bus stop density, whereas the relative importance of population density, bus stop density, and accessibility to green space or commercial facilities is close for the old-old. The retired tend to walk longer in denser-populated neighborhoods with better bus service, but the non-retired are more active in walking in mixed-developed environments with accessible commercial facilities. The thresholds of bus stop density to encourage walking among the young-old is 7.8 counts/km 2 , comparing to 6 counts/km 2 among the old-old. Regarding the green space accessibility, the effective range for the non-retired (4 to 30%) is smaller than that of the retired (12 to 45%)., Discussion: Overall, the findings provide nuanced and diverse interventions for creating walking-friendly neighborhoods to promote walking across different sub-groups of older adults., Competing Interests: LZ was employed by the JSTI Group. SY was employed by the Shanghai Municipal Engineering Design Institute (Group) Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wu, Li, Zhu, Liu, Peng, Wang, Yuan and Zhang.)