Size-resolved organic speciation of wintertime aerosols in California's Central Valley

A new mechanism by which environmental hazardous substances enhance their toxicities to plants

The coexistence of hazardous substances enhances their toxicities to plants, but its mechanism is still unclear due to the unknown cytochemical behavior of hazardous substance in plants. In this study, by using interdisciplinary methods, we observed the cytochemical behavior of coexisting hazardous substances {terbium [Tb(III)], benzo(a)pyrene (BaP) and cadmium [Cd(II)] in environments} in plants and thus identified a new mechanism by which coexisting hazardous substances in environments enhance their toxicities to plants. First, Tb(III) at environmental exposure level (1.70 × 10^-10 g/L) breaks the inert rule of clathrin-mediated endocytosis (CME) in leaf cells. Specifically, Tb(III) binds to its receptor [FASCICLIN-like arabinogalactan protein 17 (FLA17)] on the plasma membrane of leaf cells and then docks to an intracellular adaptor protein [adaptor protein 2 (AP2)] to form ternary complex [Tb(III)-FLA17-AP2], which finally initiates CME pathway in leaf cells. Second, coexisting Tb(III), BaP and Cd(II) in environments are simultaneously transported into leaf cells via Tb(III)-initiated CME pathway, leading to the accumulation of them in leaf cells. Finally, these accumulated hazardous substances simultaneously poison plant leaf cells. These results provide theoretical and experimental bases for elucidating the mechanisms of hazardous substances in environments poisoning plants, evaluating their risks, and protecting ecosystems.

Sources of carbohydrates on bulk deposition in South-Western of Europe

Scarce information is available concerning the presence of carbohydrates in rainwater. The existence of carbohydrates in bulk deposition at the town of Estarreja (Portugal), at industrial (I) and background (BG) locals, in winter and spring seasons 2016, was assessed. Seventeen carbohydrates and related compounds were identified: monosaccharides (ribose, arabinose, xylose, glucose, galactose, fructose), disaccharides (sucrose, trehalose, maltose, cellobiose), polyols (arabinitol, xylitol, myo-inositol, mannitol, glucitol, maltitol), and the anhydromonosaccharide levoglucosan. Higher content of carbohydrates was observed in spring (BG: 670 nM; I: 249 nM) than in winter (BG: 168 nM; I: 195 nM), and fructose was the carbohydrate with the highest contribution in both seasons (spring: 32%/44% (I/BG); winter: 24% (at both sites)). Fructose, myo-inositol, glucose and sucrose showed higher volume-weighted averages (VWA) concentrations in spring than in winter, possibly due to biogenic emissions typical of spring, such as pollen, and fungal spores for myo-inositol. Fructose may have derived from isomerization of glucose in biomass burning, namely in winter. Levoglucosan and galactose presented higher VWA concentration in winter than in spring, suggesting a seasonal effect related with the biomass combustion. The carbohydrates VWA concentrations were similar for samples associated with maritime and terrestrial air masses, indicating that local sources were their main contributors. Source assessment of carbohydrates by factor analysis suggested: biogenic sources for the arabinitol, myo-inositol, glucose, fructose and sucrose; soil dust for the trehalose; and anthropogenic sources from biomass burning for the galactose, arabinose and levoglucosan. The bulk deposition showed to be fundamental on removing carbohydrates from the atmosphere.

Biomass burning contributions to urban aerosols in a coastal Mediterranean city

Mean annual biomass burning contributions to the bulk particulate matter (PM(X)) load were quantified in a southern-European urban environment (Barcelona, Spain) with special attention to typical Mediterranean winter and summer conditions. In spite of the complexity of the local air pollution cocktail and the expected low contribution of biomass burning emissions to PM levels in Southern Europe, the impact of these emissions was detected at an urban background site by means of tracers such as levoglucosan, K(+) and organic carbon (OC). The significant correlation between levoglucosan and OC (r(2)=0.77) and K(+) (r(2)=0.65), as well as a marked day/night variability of the levoglucosan levels and levoglucosan/OC ratios was indicative of the contribution from regional scale biomass burning emissions during night-time transported by land breezes. In addition, on specific days (21-22 March), the contribution from long-range transported biomass burning aerosols was detected. Quantification of the contribution of biomass burning aerosols to PM levels on an annual basis was possible by means of the Multilinear Engine (ME). Biomass burning emissions accounted for 3% of PM(10) and PM(2.5) (annual mean), while this percentage increased up to 5% of PM(1). During the winter period, regional-scale biomass burning emissions (agricultural waste burning) were estimated to contribute with 7±4% of PM(2.5) aerosols during night-time (period when emissions were clearly detected). Long-range transported biomass burning aerosols (possibly from forest fires and/or agricultural waste burning) accounted for 5±2% of PM(2.5) during specific episodes. Annually, biomass burning emissions accounted for 19%-21% of OC levels in PM(10), PM(2.5) and PM(1). The contribution of this source to K(+) ranged between 48% for PM(10) and 97% for PM(1) (annual mean). Results for K(+) from biomass burning evidenced that this tracer is mostly emitted in the fine fraction, and thus coarse K(+) could not be taken as an appropriate tracer of biomass burning.