Trace metal pollution and ecological risk assessment in agricultural soil in Dexing Pb/Zn mining area, China.

Surface agricultural soil samples obtained from Dexing Pb/Zn mining area in Jiangxi province were analyzed for trace metals to assess their pollution status and potential ecological risk. The spatial distributions and the major trace metals pollution sources were described and identified with the combination of chemical measures and geographic information systems technology. The level of pollution in seven metals is decreasing in the following order: zinc (Zn 128.9 mg/kg) > chromium (Cr 64.1 mg/kg) > lead (Pb 58.4 mg/kg) > arsenic (As 45.3 mg/kg) > copper (Cu 41.9 mg/kg) > nickel (Ni 31.3 mg/kg) > cadmium (Cd 1.5 mg/kg). Trace metal spatial distribution maps established by geographic information system techniques displayed two high-pollution zones around mining sites in the study area. Multivariate statistical analyses were also applied, and the results demonstrated that Cd, As, Pb, Cu and Zn in the soils originated from mining activities, whereas Cr and Ni primarily originated from natural sources. The values of pollution index ranged from 4.79 to 71.59, and the values of modified pollution index ranged from 1.98 to 24.69. Moreover, the potential ecological risk values ranged from 264.0 to 3263.5, which indicated considerable ecological risk to very high ecological risk. The potential ecological risk values and other soil contamination indices showed similar patterns that the high-risk areas were around Dexing Pb/Zn mining site. The surface agricultural soil in study area is heavily to extremely polluted , with Cd that made the most dominant contribution.

The effects of extracellular algicidal compounds of Bacillus sp. B1 on Heterosigma akashiwo: a metabolomics approach.

Heterosigma akashiwo (H. akashiwo), a harmful algal species, has been a global environmental problem. Extracellular algicidal compounds (EACs) extracted from Bacillus sp. B1 exhibited algicidal effects against H. akashiwo. However, little is known about the algicidal mechanism and metabolic process. In this study, metabolomics and physiological analyses were combined to investigate the cellular responses of H. akashiwo when treated with EACs. The results indicated that EACs at 10% (vEACs/vsample) showed more than 90% inhibition of H. akashiwo. EAC treatment resulted in excessive reactive oxygen species (ROS) production in algal cells, causing stress responses such as inhibition of photosynthetic pigment synthesis, reduction of sugar synthesis, imbalance of osmotic pressure in the cell membrane, disruption of cell size and morphology, and eventual cell death. The results reveal the underlying mechanism of the algicidal process and provide new insights into algae-bacteria interactions and the application of metabolomics to algal research.