Formation and Stabilization of Environmentally Persistent Free Radicals Induced by the Interaction of Anthracene with Fe(III)-Modified Clays

Abstract

Environmentally persistent free radicals (EPFRs) are occasionally detected in Superfund sites but the formation of EPFRs induced by polycyclic aromatic hydrocarbons (PAHs) is not well understood. In the present work, the formation of EPFRs on anthracene-contaminated clay minerals was quantitatively monitored via electron paramagnetic resonance (EPR) spectroscopy, and surface/interface-related environmental influential factors were systematically explored. The obtained results suggest that EPFRs are more readily formed on anthracene-contaminated Fe(III)-montmorillonite than in other tested systems. Depending on the reaction condition, more than one type of organic radicals including anthracene-based radical cations with g-factors of 2.0028-2.0030 and oxygenic carbon-centered radicals featured by g-factors of 2.0032-2.0038 were identified. The formed EPFRs are stabilized by their interaction with interlayer surfaces, and such surface-bound EPFRs exhibit slow decay with 1/e-lifetime of 38.46 days. Transformation pathway and possible mechanism are proposed on the basis of experimental results and quantum mechanical simulations. Overall, the formation of EPFRs involves single-electron-transfer from anthracene to Fe(III) initially, followed by H2O addition on formed aromatic radical cation. Because of their potential exposure in soil and atmosphere, such clay surface-associated EPFRs might induce more serious toxicity than PAHs and exerts significant impacts on human health.

Reactive Oxygen Species Formed by Secondary Organic Aerosols in Water and Surrogate Lung Fluid

“…This indicates that EPFR have a longer lifetime under dry conditions, and they may decompose upon interaction with water. This result is consistent with the study by Jia et al, 33 which showed a fast decay of anthracene source EPFR even under 8% RH. Figure 2 also includes EPR measurements with a spintrapping technique for SOA water extracts mixed with BMPO (pink lines).…”

High contribution of hydrocarbon transformation during the removal of polycyclic aromatic hydrocarbons from soils, humin and clay by thermal treatment at 100–200 °C

“…These interactions either promote or inhibit PAH removal. For instance, montmorillonite promotes benzo[a]pyrene removal, with a high decrease of concentration to 0.111 mg/g at 200 °C, in agreement with our previous report on the impact of clays (Jia et al 2016). On the contrary, results show that humin, a major organic component, inhibits benzo[a]pyrene removal, with a concentration almost unchanged (0.494 mg/g) versus initial concentration (0.503 mg/g), at 100 °C for 60 min.…”

“…The clay influence is also supported by the clay content of our soil samples, of 26 wt% for the bauxite soil, 18.2 wt% for the fluvo-aquic soil and 19.3 wt% for the chernozem soil. These observations are supported by our previous studies showing that benzo [a] pyrene interacts with the clay surface via cation-π complexation, then promotes electron transfer followed by oxidation (Jia and Wang 2013;Jia et al 2016). Alternatively, transformation of benzo[a]pyrene may be triggered by oxidative degradation in the presence of manganese and iron oxide in soil during heating (Umeh et al 2018), as suggested by the presence of Mn and Fe in our soil samples (Table S1).…”

Reactive oxygen species formed in aqueous mixtures of secondary organic aerosols and mineral dust influencing cloud chemistry and public health in the Anthropocene

“…[28][29][30] Furthermore, combustion-generated particles such as soot contain environmentally persistent free radicals (EPFRs), which are most likely semiquinone radicals. 31,32 Ambient particles can release a variety of ROS upon interactions with water, 33 amplifying ultrane particle mediated cellular oxidative stress and cytotoxicity. 34,35 Substantial amounts of particle-bound ROS are found on biogenic SOA.…”