A shortened version of Quick, Easy, Cheap, Effective, Rugged, and Safe method (QuEChERS) for determining the dissipation and residue of imidacloprid present in Zizania latifolia and purple sweet potato was established by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The average recoveries of imidacloprid in the two crops ranged from 82.12 to 113.79%, with relative standard deviation (RSD) of <7.32%. The dissipation dynamics of imidacloprid in Z. latifolia plants and purple sweet potato plants followed first-order kinetics, with half-lives of 3.2–5.5?days in each of sampling locations. The terminal imidacloprid residues in Z. latifolia and purple sweet potato at each of location were <0.005–0.120?mg kg?1. According to the risk assessment results, both the acute dietary risk quotient and chronic dietary risk quotient values were <1, indicating that imidacloprid is unlikely to pose health risks to humans with normal recommended use. The present study may serve as a valuable reference for the safe and reasonable use of imidacloprid in Z. latifolia and purple sweet potato fields. 相似文献
The uptake, translocation, and human bioaccessibility of metals originating from atmospheric fine particulate matters (PM) after foliar exposure is not well understood. Lettuce (Lactuca sativa L.) plants were exposed to micronic PbO, CuO, and CdO particulate matters (PMs) by the foliar pathway and mature plants (6 weeks old) were analyzed in terms of: (1) metal accumulation and localization on plant leaf surface, and metal translocation factor (TF) and global enrichment factor (GEF) in the plants; (2) shoot growth, plant dry weight (DW), net photosynthesis (Pn), stomatal conductance (Gs), and fatty acid ratio; (3) metal bioaccessibility in the plants and soil; and (4) the hazard quotient (HQ) associated with consumption of contaminated plants. Substantial levels of metals were observed in the directly exposed edible leaves and newly formed leaves of lettuce, highlighting both the possible metal transfers throughout the plant and the potential for human exposure after plant ingestion. No significant changes were observed in plant biomass after exposure to PbO, CuO, and CdO-PMs. The Gs and fatty acid ratio were increased in leaves after metal exposure. A dilution effect after foliar uptake was suggested which could alleviate metal phytotoxicity to some degree. However, plant shoot growth and Pn were inhibited when the plants are exposed to PbO, and necrosis enriched with Cd was observed on the leaf surface. Gastric bioaccessibility of plant leaves is ranked: Cd?>?Cu?>?Pb. Our results highlight a serious health risk of PbO, CuO, and CdO-PMs associated with consumption of vegetables exposed to these metals, even in newly formed leaves in the case of PbO and CdO exposure. Finally, the study highlights the fate and toxicity of metal rich-PMs, especially in the highly populated urban areas which are increasingly cultivated to promote local food.
A Pd/Sn bimetallic nanoparticles resin (nano-Pd/Sn/resin) was successfully synthesized for reductive transformation of aqueous trichloroethylene (TCE). The physicochemical properties of the prepared resin were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, N(2) isothermal sorption at and X-ray photospectroscopy. The surface-area-normalized rate constants (k(SA)) of Sn particles in the nanoscale range (50-100 nm) were 4.5 times larger than the k(SA) for powdered Sn (0.04 mm). After depositing 1 wt% Pd onto nano-Sn surface, k(SA) was further enhanced by about a factor of 2. Groundwater constituents such as sulfide nitrate and dissolved oxygen had significant negative effects on the rate of TCE degradation by the nano-Pd/Sn/resin. A wet-chemical method regeneration method was observed to effectively restore the reactivity of the poisoned nano-Pd/Sn/resin after dipping in sulfide solution for 2d. In all cases, less than 0.5% of the degraded TCE appeared as chlorinated byproducts including the three dichloroethene isomers. The nano-Pd/Sn/resin technique performs well in transforming TCE into nontoxic hydrocarbons, as compared with other published methods. 相似文献
Outliers in urban soil geochemical databases may imply potential contaminated land. Different methodologies which can be easily implemented for the identification of global and spatial outliers were applied for Pb concentrations in urban soils of Galway City in Ireland. Due to its strongly skewed probability feature, a Box–Cox transformation was performed prior to further analyses. The graphic methods of histogram and box-and-whisker plot were effective in identification of global outliers at the original scale of the dataset. Spatial outliers could be identified by a local indicator of spatial association of local Moran's I, cross-validation of kriging, and a geographically weighted regression. The spatial locations of outliers were visualised using a geographical information system. Different methods showed generally consistent results, but differences existed. It is suggested that outliers identified by statistical methods should be confirmed and justified using scientific knowledge before they are properly dealt with. 相似文献