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Nitroaromatic explosives, such as 2,4,6-trinitrotoluene, are representative aromatic compounds, which are generally highly toxic.

Lipid peroxidation (LPO) in cellular membranes can cause severe membrane damage and potential cell death. Although oxidized phospholipids have been proved to lead to great changes in the structures and properties of membranes, effects of low-level LPO on membrane permeability have not yet been fully understood. Here, we explored the molecular mechanism of low-level LPO changing the permeability of nitroaromatic molecules across a lipid bilayer by all-atom molecular dynamics simulations. The results reveal that the enhanced passive transport of nitroaromatic molecules lies in the size of defects (i.e., water "finger" and "cone"), which is further dependent on the extent of LPO and the structural feature of solutes. In detail, if the solute can form more hydrogen bonds with water, which stabilizes the water into a large-size cone, there is a greater permeability coefficient (P). Otherwise, a small-size finger only results in a small increase of P. For example, the presence of 15% oxidized lipids could result in an increase of 2,4,6-trinitrotoluene (TNT's) P by more than 2 orders of magnitude (from 1.7 × 10 −2 to 2.39 cm•s −1 ). The result suggests that the membrane permeability can be greatly promoted in the physiologically relevant environment with low-level LPO, and more importantly, clarifies the contributions of both the hydrophobicity of the membrane interior and the structural feature of solutes to such enhanced permeability. This work may provide significant insight into the toxic effects of nitroaromatic molecules and the pharmaceutical characteristics of tissues with oxidative damage.

The Sanitation Districts of Los Angeles County (Districts) have been using ferrous chloride (FeCl 2 ) to control the hydrogen sulfide (H 2 S) concentration in digester gas at the Joint Water Pollution Control Plant (JWPCP) for over 30 years. Although FeCl 2 has been very effective in controlling digester H 2 S levels, the cost of this chemical has increased significantly in the last few years. Consequently, the Districts initiated a study to investigate the use of biotrickling filters (BTFs) to control digester gas H 2 S. Two pilot-scale biotrickling filters were tested under slightly aerobic and anoxic conditions. Two types of filter media, lava rock and plastic rings, were tested in the aerobic filter, and lava rock was tested in the anoxic filter. Concentrated H 2 S was spiked into the digester gas to simulate elevated H 2 S levels characteristic of lower FeCl 2 doses. For H 2 S levels between 200 and 400 ppm, the aerobic BTF with a plastic ring media was able to reduce H 2 S to below the regulatory limit of 40 ppm at empty bed retention times (EBRT) of 20 to 37 seconds. The aerobic lava rock BTF experienced a clogging problem, and the anoxic lava rock BTF was not able to reduce 200 ppm of H 2 S to below the regulatory limit at an EBRT of 50 seconds.

No abstract