Cadmium (Cd) is an abiotic stressor negatively affecting plant growth and reducing crop productivity. The effects of Cd (25 mu M) and of pre-soaking seeds with salicylic acid (SA) (500 mu M) on morphological, physiological, and glycerolipid changes in two cultivars of wheat (Triticum aestivum L. 'Tosunbey' and 'Cumhuriyet') were explored. Parameters measured were length, fresh and dry biomass, Cd concentration, osmotic potential (psi), lipid peroxidation, and polar lipid species in roots and leaves, as well as leaf chlorophyll a, carotenoids, and fv/fm. Fresh biomass of roots and leaves and leaf length were strongly depressed by Cd treatment compared to the control, but significantly increased with SA + Cd compared to Cd alone. Cd reduced leaf levels of chlorophyll a, carotenoids, and fv/fm, compared to controls. Treatment with SA + Cd increased pigment levels and fv/fm compared to Cd alone. Cd treatment led to a decrease in DW of total membrane lipids in leaves and depressed levels of monogalactosyldiacylglycerol and phosphatidic acid in leaves and roots of both cultivars. The effects of SA priming and SA + Cd treatment on lipid content and composition were cultivar-specific, suggesting that lipid metabolism may not be a primary target underlying SA remediation of the damaging effects of Cd on wheat growth and development.

Pesticide application is used in horticulture to reduce plant damage from organisms such as insects and mites. Systemic insecticides are highly ef fi cacious and readily taken up by plant tissues. However, pesticide -treated plants may impose risks to nontarget insects or other organisms within ecosystems. In this study, insecticide residues in nectar, leaves, and fl ower petals of the horticulturally signi fi cant herbaceous annual snapdragon, Antirrhinum majus (Lamiales: Plantaginaceae), were assessed at two locations over several weeks following foliar and drench treatment with fi ve systemic insecticides. Concentrations of the insecticides were determined by liquid chromatography - mass spectrometry. The independent effects Application Method , Application Rate , and Time were statistically signi fi cant among all active ingredients in the three matrices in both sites in California (CA) and New Jersey (NJ). The interaction effects were also generally statistically signi fi cant in the CA site but less consistently so in the NJ site, dependent on the active ingredient and matrix. Post hoc analyses found the highest residue concentrations in leaves and the lowest in nectar, a trend generally consistent over time regardless of active ingredient for both the CA and NJ sites. The results of this study are discussed in the context of conserving pollinators and other bene fi cial insects. It is recommended that similar studies should be implemented in different geographical regions and climates, along with multiyear studies for perennial ornamental plants.

The addition of coating to the black carbon (BC) enhances its absorption as more light is focused by the coating lens. The absorption enhancement factor (E-abs) of BC is difficult to quantify due to an inadequate representation of its mixing structure and the interaction with radiation. Here, by tracking the evolution of the fresh BC particles in the ambient, we found a transitional stage of the particle E-abs with the non-BC-to-BC mass ratio (R-BC) at similar to 2, below which there were insufficient coating materials to encapsulate the BC core and the absorption enhancement was not significant (similar to 14%). When the R-BC >similar to 2, obvious absorption enhancement occurred as the BC cores were fully covered. Secondary inorganic species played the most critical role in the coating materials to enhance the lensing effect. We suppose the particle-resolved core-shell Mie model can be applied in the E-abs prediction for most cases.

Light absorbing organic carbon, a.k.a., brown carbon (BrC) is an important contributor to air quality deterioration and global radiative forcing. This work studied optical, chemical properties and sources of BrC in fine particles (PM2.5) collected in Yangzhou, China. The light absorption coefficient at 365 nm of methanol-soluble organics (Abs(365,WSOC)) and water-soluble organics (Abs(365,WSOC)) were 13.50 +/- 7.03 M/m and 6.08 +/- 4.30 M/m, respectively. Mass absorption efficiency at 365 nm (MAE(365)) of methanol-soluble BrC (1.12 +/- 0.35 m(2)/gC) was also higher than water-soluble BrC (0.75 +/- 0.29 m(2)/g C). For water-soluble BrC, both Abs(365) and MAE(365) generally decreased with increases of its oxygen-to-carbon (O/C) ratios and oxidation states (OSc), indicative of photo-bleaching upon chemical ageing. Positive responses of Abs(365,WSOC) and MAE(365,WSOC) to nitrogento-carbon (N/C) ratios and water-soluble organic nitrogen (ON) contents reveal that ON species are important BrC chromophores. A multiple linear regression model was applied to apportion Abs(365,WSOC) to contributions of different factors resolved from positive matrix factorization on water-soluble organic aerosols (OA), and obtained MAE(365) values of different OA factors. Overall, primary OA sources including traffic (18.9%), biomass burning (23.7%), and cooking-related OA (10.5%) together dominated the AbS(365,WSOC) despite their total mass contribution was only about one third (31.9%). The largest single contributor of Abs(365,WSOC) however, was the less-oxidized secondary OA (33.8%); the more-oxidized secondary OA factor dominated water-soluble OA mass (50.8%), yet its light absorptivity was the weakest and contributed only 13.1% of Abs(365,WSOC).

Recent studies have revealed the abundance of dissolved organic matter (DOM) in snow/glaciers of the Tibetan Plateau (TP). Here, we present a comprehensive study on the chemical compositions of snowpit samples collected from widely distributed eight glaciers in the western China (six from the TP) to investigate the spatial variation of deposited atmospheric aerosols. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was used to chemically characterize the DOM in snow samples which can offer chemical properties of DOM. Highest mass concentration of dissolved species mass was observed in Tienshan Baishui No 1 glacier (TS, 6.55 +/- 0.85 mg/L) close to Takalamagan Desert, whereas lowest (0.89 +/- 0.18 mg/L) was observed in Zadang Glacier (ZD) in the central TP. DOM (8-40%) and calcium as well as magnesium (9-67%) were generally the most abundant chemical species. Average DOM concentration in the TP glaciers among the investigated sites were comparable. DOM was found highly oxidized with an oxygen to carbon ratio (O/C ratio) ranging from 0.82 to 1.03. Highly oxidized DOM could have related with aerosol aqueous processes as illustrated by observed organic acids. This study provides insights into the spatial variations of the DOM and dissolved inorganic matter, as well as oxidized organic aerosol, were most likely due to local and regional contribution. (C) 2019 Elsevier B.V. All rights reserved.

Brown carbon is a hotspot in the field of atmospheric carbonaceous aerosol research. It has significant influence on regional radiative forcing and exerts climatic effects due to its apparent absorbance in the near ultraviolet-visible region. Brown carbon is mainly derived from incomplete combustion of biomass or coal, as well as secondary sources, such as a series of atmospheric photochemical reactions from volatile organic compounds. Although the composition of brown carbon is complex, high-resolution mass spectrometry, with its ultra-high mass resolution and precision, enables elucidation of the characteristics of the organic components of brown carbon at the molecular level. Here, high-resolution mass spectrometry combined with traditional analytical methods was used for the study of brown carbon. The development of high-resolution mass spectrometry for brown carbon separation is reviewed, as well as compositional analysis, source apportionment, and formation mechanism of brown carbon based on high-resolution data. In addition, the issues and prospects for the application of high-resolution mass spectrometry to evaluate brown carbon are discussed.