RESUMO
To understand the enrichment factors and pollution levels of heavy metals in agricultural soils in the semi-arid region of Hainan island, 1818 surface soil samples were collected in Gancheng Town and analyzed for their heavy metal contents and physicochemical composition. Correlation analysis was used to determine the heavy metal enrichment factors. The geo-accumulation index (Igeo), comprehensive ecological risk index (RI), and hazard index (HI), as well as carcinogenic risk (CR), were used to assess the degree of pollution and health risk. Positive matrix factorization (PMF) was used to determine the primary sources of pollution and priority sources. The average values of heavy metal contents in the topsoil were 22.7, 0.128, 33.4, 14.5, 0.032, 9.32, 32.5, and 43.3 mg·kg-1 for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, respectively. With the exception of Zn, the concentrations of other heavy metals in the topsoil were higher than the soil background values of Hainan, showing different degrees of heavy metal accumulation effect. The Igeo revealed that the major pollutant element in soils was As, followed by Cd and Cu. The RI showed that the proportion of soil samples that were high-risk level or worse was 29.4% of the total number of samples, among which As was the major source of risk. The health risk assessment results indicated that As, Cr, and Ni exposure presented carcinogenic risk for children with high CR values. Based on PMF, four major sources of heavy metals were identified in the study area. Hg was derived mainly from industrial sources, and As was closely associated with agricultural activities. Ni, Cu, Cr, and Zn were related to soil parent materials. Pb and Cd were associated with agricultural activities and traffic emissions. The PMF models combined with correlation analysis were useful for estimating the source apportionment of heavy metals in soils.
Assuntos
Mercúrio , Metais Pesados , Poluentes do Solo , Cádmio/análise , Carcinógenos/análise , Criança , China , Monitoramento Ambiental/métodos , Humanos , Chumbo/análise , Mercúrio/análise , Metais Pesados/análise , Medição de Risco , Solo/química , Poluentes do Solo/análiseRESUMO
The epithelial-to-mesenchymal transition (EMT) is important for the development of cancer metastases and organ fibrosis, conditions prevalent in aging. Because sirtuins affect the pathology of aging, we tested the effect of SirT1 on EMT. Reduced SIRT1 levels in HMLER breast cancer cells led to increased metastases in nude mice, and the loss of SIRT1 in kidney tubular epithelial cells exacerbated injury-induced kidney fibrosis. SIRT1 reduces EMT in cancer and fibrosis by deacetylating Smad4 and repressing the effect of TGF-ß signaling on MMP7, a Smad4 target gene. Consequently, less E-cadherin is cleaved from the cell surface and ß-catenin remains bound to E-cadherin at the cell-cell junctions. Our findings suggest that the SIRT1/Smad4/ß-catenin axis may be a target for diseases driven by EMT.