Davidsenkramer0817

It can also be used to quantify the importance of variables and identify potential control factors in heavy metal bioaccumulation in soil-crop ecosystems. Low pH and aluminum (Al)-toxicity often coexist in acidic soils. Citrus sinensis seedlings were treated with nutrient solution at a pH of 2.5, 3.0, 3.5 or 4.0 and an Al concentration of 0 or 1 mM for 18 weeks. Thereafter, malate, citrate, isocitrate, acid-metabolizing enzymes, and nonstructural carbohydrates in roots and leaves, and release of malate and citrate from roots were measured. Al concentration in roots and leaves increased under Al-toxicity, but it declined with elevating nutrient solution pH. Al-toxicity increased the levels of glucose, fructose, sucrose and total soluble sugars in leaves and roots at each given pH except for a similar sucrose level at pH 2.5-3.0, but it reduced or did not alter the levels of starch and total nonstructural carbohydrates (TNC) in leaves and roots with the exception that Al improved TNC level in roots at pH 4.0. Levels of nonstructural carbohydrates in roots and leaves rose with reducing pH with a few exceptions with or without Al-toxicity. A potential model for the possible role of root organic acid (OA) metabolism (anions) in C. sinensis Al-tolerance was proposed. With Al-toxicity, the elevated pH upregulated the OA metabolism, and increased the flow of carbon to OA metabolism, and the accumulation of malate and citrate in roots and subsequent release of them, thus reducing root and leaf Al and hence eliminating Al-toxicity. Without Al-toxicity, low pH stimulated the exudation of malate and citrate, an adaptive response of Citrus to low pH. The interactive effects of pH and pH on OA metabolism were different between roots and leaves. Organic matter (OM) acts as a source of carbon and is strongly implicated in biogeochemical processes, such as metal complexation and redox reactions. To illustrate the effects of OM on As mobilization in aquifers, this study characterized fluorescence features and hydrochemical properties of OM in sediments and groundwater from an As-affected field site located in the Datong Basin. Fluorescence analysis showed sediment and groundwater OM are dominated by oxidized and reduced quinone-like compounds; shorter emission wavelengths observed in groundwater indicated more labile and protein-like organic substances than in sediments. Dissolved As concentrations were positively correlated with dissolved Fe and HCO3- concentrations in middle and deep groundwater, suggesting labile OM degradation promotes the release of As and Fe from sediments into the groundwater. This result also demonstrated more bioavailable OM occurs in groundwater and that labile OM degradation promotes As release. Grain size distribution results indicated sedimentary As, Fe and OM are associated with fine-grained fractions. Sedimentary As content was significantly and positively correlated with Fe2O3 and OM content, suggesting the potential existence of As-Fe-OM ternary complexation; this was further supported by the results of Fourier-transform infrared (FTIR) spectra and extraction experiments. In addition, the ratio of dissolved reduced quinone-like compounds to oxidized quinone-like compounds was positively correlated with both dissolved As and HCO3- concentrations, implying quinone-like compounds participate in the complexation and influence As mobilization. In the reducing environment, labile OM served as the electron donor to maintain microbial respiration and mediated reductive dissolution of Fe minerals. As-Fe-OM ternary complexation in sediments and microbial reduction have a potentially strong impact on As enrichment in groundwater, and therefore are important considerations for regulating As contamination. Although several studies have linked PM2.5 (particulate matter with a diameter less than 2.5 μm) to ocular surface diseases such as keratitis and conjunctivitis, very few studies have previously addressed its effect on the retina. Therefore, the aim of this study was to evaluate the effect of PM2.5 on epithelial-mesenchymal transition (EMT), a process involved in disorders of the retinal pigment epithelial (RPE) on APRE-19 cells. PM2.5 changed the phenotype of RPE cells from epithelial to fibroblast-like mesenchymal, and increased cell migration. Exposure to PM2.5 markedly increased the expression of mesenchymal markers, but reduced the levels of epithelial markers. Moreover, PM2.5 promoted the phosphorylation of MAPKs and the expression of transforming growth factor-β (TGF-β)-mediated nuclear transcriptional factors. However, these PM2.5-mediated changes were completely reversed by LY2109761, a small molecule inhibitor of the TGF-β receptor type I/II kinases, and N-acetyl-L-cysteine (NAC), a reactive oxygen species (ROS) scavenger. Interestingly, NAC, but not LY2109761, effectively restored the PM2.5-induced mitochondrial defects, including increased ROS, decreased mitochondrial activity, and mitochondrial membrane potential disruption. Collectively, our findings indicate that the TGF-β/Smad/ERK/p38 MAPK signaling pathway is activated downstream of cellular ROS during PM2.5-induced EMT. The present study provides the first evidence that EMT of RPE may be one of the mechanisms of PM2.5-induced retinal dysfunction. As an important component of organic carbon (OC), brown carbon (BrC) plays a significant role in radiative forcing in the atmosphere. Water-insoluble OC (WIOC) generally has higher light absorption ability than water-soluble OC (WSOC). selleck chemical The mass absorption cross-section (MAC) of WIOC is normally investigated by dissolving OC in methanol. However, all the current methods have shortcomings due to neglecting the methanol insoluble particulate carbon that is detached from the filter and suspended in methanol extracts, which results in MAC uncertainties of the methanol-soluble BrC and its climate warming estimation. In this study, by investigating typical biomass combustion sourced aerosols from the Tibetan Plateau and ambient aerosols from rural and urban areas in China, we evaluated the light absorption of extractable OC fraction for the existing methods. Moreover, a new method was developed to overcome the methanol insoluble particulate carbon detachment problem to achieve more reliable MAC values. We found that OC can be dissolved in methanol in a short time (e.