[Distribution Characteristics and Ecological Risk Assessment of Soil Heavy Metals in Baiyangdian Lake].

To understand the spatial distribution characteristics and potential ecological risk of heavy metals in soil of Baiyangdian Lake, 55 soil samples were collected and the contents of eight heavy metals (Mn, Cr, Cu, Zn, As, Cd, Pb, and Ni) were detected. The spatial variation structure and distribution pattern were analyzed using geostatistical methods (Moran index and semi-variance model). The degree of heavy metal pollution and its risk were assessed using the geoaccumulation index (Igeo) and potential ecological risk index (Eri and RI). The results showed that the average of ω(Mn), ω(Cr), ω(Cu), ω(Zn), ω(As), ω(Cd), ω(Pb), and ω(Ni) were 467.75, 43.59, 28.57, 89.04, 12.32, 0.18, 19.26, and 30.56 mg·kg-1, respectively, all of which were lower than the screening values of soil pollution risk in agricultural land. However, the contents of Cu, Zn, and Cd were significantly higher than their background values, with two highly variable elements of Cu (48.65%) and Cd (37.52%). The Moran index indicated that Mn, Cu, Cd, and Pb showed weak spatial autocorrelation. Nugget coefficients of both of Cd and Pb shown by the semi-variance model were 100%, suggesting random variation as a main spatial variation driven by anthropogenic factors. High values of soil heavy metals were mainly distributed in the southwest of Baiyangdian Lake with a significant correlation between the heavy metals. The Igeo of soil heavy metals from high to low was Cd>Cu>Zn>Ni>As>Pb>Mn>Cr. Cd pollution was the most common, in which 67.27% of the samples were lightly polluted. Ecological risk assessment revealed that the average Eri of Cd was 58.81, belonging to the middle ecological risk level, and the rest were at light ecological risk. As a whole, the RI of soil heavy metal pollution in Baiyangdian Lake was at a light ecological risk level (87.81), with the highest contribution rate of Cd to RI (66.39%). Thus, it is necessary to strengthen the control of soil heavy metal Cd pollution in Baiyangdian Lake in the future.

MiR-26a functions as a tumor suppressor in ambient particulate matter-bound metal-triggered lung cancer cell metastasis by targeting LIN28B-IL6-STAT3 axis.

Exposure to ambient particulate matter (PM) has been linked to the increasing incidence and mortality of lung cancer, but the principal toxic components and molecular mechanism remain to be further elucidated. In this study, human lung adenocarcinoma A549 cells were treated with serial concentrations of water-extracted PM10 (WE-PM10) collected from Beijing, China. Our results showed that exposure to 25 and 50 µg/ml of WE-PM10 for 48 h significantly suppressed miR-26a to upregulate lin-28 homolog B (LIN28B), and in turn activated interleukin 6 (IL6) and signal transducer and activator of transcription 3 (STAT3) in A549 cells, subsequently contributing to enhanced epithelial-mesenchymal transition and accelerated migration and invasion. In vivo pulmonary colonization assay further indicated that WE-PM10 enhanced the metastatic ability of A549 cells. In addition, luciferase reporter assay demonstrated that 3' untranslated region of LIN28B was a direct target of miR-26a. Last but not the least, the key toxic contribution of metals in WE-PM10 was confirmed by the finding that removal of metals through chelation significantly rescued WE-PM10-mediated inflammatory, carcinogenic and metastatic responses. Taken together, miR-26a could act as the tumor suppressor in PM10-related lung cancer, and PM10-bound metals promoted lung cancer cell metastasis through downregulation of miR-26a that directly mediated LIN28B expression.