College of Natural Resources and Environment; State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation , Northwest A & F University , Yangling 712100 , China.
College of Environmental Science and Engineering , Donghua University , Shanghai 201620 , China.
Environ Sci Technol. 2019 Sep 3;53(17):10120-10130. doi: 10.1021/acs.est.9b03453. Epub 2019 Aug 23.
Environmentally persistent free radicals (EPFRs) are emerging contaminants occurring in combustion-borne particulates and atmospheric particulate matter, but information on their formation and behavior on fly ash from municipal solid waste (MSW) incinerators is scarce. Here, we have found that MSW-associated fly ash samples contain an EPFR concentration of 3-10 × 10 spins g, a line width (Δ) of ∼8.6 G, and a -factor of 2.0032-2.0038. These EPFRs are proposed to be mixtures of carbon-centered and oxygen-centered free radicals. Fractionation of the fly ash-associated EPFRs into solvent-extracted and nonextractable radicals suggests that the solvent-extracted part accounts for ∼45-73% of the total amount of EPFRs. Spin densities of solvent-extracted EPFRs correlate positively with the concentrations of Fe, Cu, Mn, Ti, and Zn, whereas similar correlations are comparatively insignificant for nonextractable EPFRs. Under natural conditions, these two types of EPFRs exhibit different stabilization that solvent-extracted EPFRs are relatively unstable, whereas the nonextractable fraction possesses a long life span. Significant correlations between concentrations of solvent-extracted EPFRs and generation of hydroxyl and superoxide radicals are found. Overall, our results suggest that the fractionated solvent-extracted and nonextractable EPFRs may experience different formation and stabilization processes and health effects.
环境持久性自由基（EPFRs）是在燃烧产生的颗粒物和大气颗粒物中出现的新兴污染物，但有关它们在城市固体废物（MSW）焚烧炉飞灰上的形成和行为的信息却很少。在这里，我们发现 MSW 相关的飞灰样品中含有 3-10×10 自旋 g 的 EPFR 浓度、约 8.6 G 的线宽（Δ）和 2.0032-2.0038 的因子。这些 EPFR 被认为是碳中心和氧中心自由基的混合物。将飞灰相关的 EPFR 分为溶剂萃取和不可萃取自由基表明，溶剂萃取部分占 EPFR 总量的约 45-73%。溶剂萃取的 EPFR 的自旋密度与 Fe、Cu、Mn、Ti 和 Zn 的浓度呈正相关，而对于不可萃取的 EPFR 则没有类似的相关性。在自然条件下，这两种类型的 EPFR 表现出不同的稳定性，溶剂萃取的 EPFR 相对不稳定，而不可萃取的部分则具有较长的寿命。还发现溶剂萃取的 EPFR 浓度与羟基和超氧自由基的生成之间存在显著相关性。总的来说，我们的结果表明，分馏的溶剂萃取和不可萃取的 EPFR 可能经历不同的形成和稳定化过程以及健康影响。
