During the past decades, heavy metal pollution in agricultural soil and its impact on human health have been becoming one of the most important global environmental problems. In this research, heavy metal (Cu, Pb, Zn, Cr, Cd, Ni, As, Hg) concentrations were measured for four hundred and two soil samples collected from agricultural area within the Guangzhou-Foshan urban zone. Soil heavy metal pollution was evaluated used geoaccumulation index and potential ecological risk index. The dose response model proposed by the USEPA was used to estimate the potential health risk caused by heavy metals in agricultural soil. The results showed that: 1) Cd and Hg were the main heavy metal pollutants in agricultural soil of the study area. 89.1% and 93.3% of total soil samples suffered medium to heavy potential ecological risk caused by Cd and Hg, respectively. 2) The THI and TCR were respectively greater than 1.0 and 1.0×10⁻⁴, indicating that heavy metals in agricultural soil were likely to constitute non-carcinogenic and carcinogenic risks, both of which were mainly brought by product consumption, to the public in the study area. The non-carcinogenic risks were mainly caused by Cr and As, while the carcinogenic risks were mainly from Cr, Cd, and As.

South China Sea (SCS) sediments can provide important paleoclimate records because of their generally high deposition rates and strong regional influence of East Asian summer monsoon (EASM) variations. However, interpretation of sedimentary records from the northwestern SCS slope is complicated because sedimentation is sensitive to sea level and provenance variations. We seek to develop a paleoclimatic record of SCS sediments by analyzing sediment magnetic properties over the past ∼36 kyr from core PC338. The dominant magnetic minerals are magnetite and hematite in most parts of the core. The hematite concentration increased profoundly over the ∼15–32 kyr B.P. period when sea level was lower than −90 m below the present level. This suggests that Red River inputs were enhanced significantly in this period. Moreover, increased coarse magnetite contents were recorded in association with an enhanced East Asian winter monsoon (EAWM) during the Last Glacial Maximum and Heinrich event 1. Low‐field and frequency‐dependent magnetic susceptibility variations were coeval with EASM‐controlled climate change recorded in South China and the SCS over the past 15 kyr, probably because regional terrestrial weathering and erosion of iron‐bearing minerals, and their transportation are dominated by climate. Rhythmic coarsening of Holocene magnetic mineral concentrations coincided with global cooling events, which indicates that core PC338 also contains signals of enhanced EAWM variations. The study demonstrates that magnetic proxies are indicative of sediment supply and deposition variations on the SCS continental slope that are useful for understanding the effects of sea level and climate change on SCS sediments.

As a primary sink of pollutants, urban soil heavy metal pollution and its influence on urban residents and ecosystems has been becoming one of the most important environmental problems. In the present study, four indices, the Geoaccumulation index (I_geo), improved Nemerow index (I_MN), degree of contamination (mC_d), and contamination security index (CSI), as well as potential ecological risk (RI), were used to evaluate individual or integrated heavy metal pollution and its ecological risk for soil samples collected from city parks, the vicinity of a landfill, and an industrial area within the city of Guangzhou. The results indicated that the improved Nemerow index (I_MN) calculated from the Geoaccumulation index was suitable for heavy metal pollution assessment of soils within landfills and industrial areas. As for soils collected from city parks, degree of contamination (mC_d) was more suitable than I_MN. Heavy metals Cd, Hg, Zn, and As were the main pollution elements in urban soils of Guangzhou. Potential ecological risks were mainly caused by Cd and Hg in urban soil of Guangzhou. Soil samples collected from city parks and the vicinity of the industrial area were moderately to highly and even extremely seriously polluted by heavy metals. Differing from the traditional cognition of the public, the ecological impact of heavy metal in soil in the vicinity of the landfill was similar to or even better than that within city parks.

Previous studies indicated serious soil arsenic (As) pollution of large spatial extent related to tungsten mining. We performed systematic analyses of magnetic parameters and As contents of a slag covered soil profile close to the abandoned tungsten mine in southern China, in order to discuss the feasibility of using sensitive, non-destructive, and cost-effective magnetic methods for monitoring the soil arsenic content in such arsenic pollution areas. The results indicate that arsenic sulfide entered from slags into the underlying soil and changed to iron arsenate and moveable arsenic ion. The arsenic ions were transported from the upper to the lower part of the soil profile, leading to more serious arsenic pollution at lower levels of the section. Pedogenesis and oxidation of the entered iron and arsenic sulfide resulted in coexistence of magnetite/maghemite and hematite, with different contributions at depths of 125–195 cm, 60–125 cm, and 0–60 cm. The arsenic content is significant positively correlated with the hematite concentration given by the magnetic parameter HIRM and negatively correlated with the S₋₃₀₀ ratio that measures the relative contributions of magnetite(+maghemite) and hematite. The S₋₃₀₀ ratio is effective for semi-quantification of soil arsenic content, and may be also used for soil arsenic pollution assessment and monitoring in similar settings of tungsten mining.