Review of experimental biodegradation data on pharmaceuticals and comparison with predictive BIOWIN models

Occurrence of volatile and semi-volatile organic compounds in solid waste landfills and their pollution risk to groundwater

The occurrence characteristics of volatile and semi-volatile organic compounds (VOCs/SVOCs) in landfills and the mechanisms driving their migration into groundwater remain unclear. The composition and concentration of VOCs/SVOCs in 14 landfill sites and surrounding groundwater in China were analyzed to explore the distribution characteristics, sources and migration patterns of VOCs/SVOCs in landfills in China. The results showed that, a total of 81 VOCs/SVOCs from nine categories were identified, including monocyclic aromatic hydrocarbons (MAHs), phthalate acid esters and polycyclic aromatic hydrocarbons (PAHs), and which originated mainly from organic solvents and plasticizers. Among the MAHs, ethylbenzene, toluene, m,p-xylene, and o-xylene (BTEX compounds) were measured at 240.0 mg/kg, 147.6 mg/kg, 179.9 mg/kg, and 75.7 mg/kg, respectively. Bis(2-ethylhexyl) phthalate had the highest detection rate (34.4 %), and 19 PAHs were detected, with concentrations ranging from 0.1 to 31.4 mg/kg. Landfills along the eastern coast exhibited a greater variety of VOCs/SVOCs than inland landfills, and the detection concentrations and rates of VOCs/SVOCs in the middle layer of the landfill were higher. The VOCs were more prone to groundwater migration than the SVOCs, with the order of phenols > anilines > halogenated aromatic and chlorinated aliphatic hydrocarbons > MAHs > PAHs. For the first time, the occurrence characteristics of 81 VOCs/SVOCs in solid waste and their potential influence on groundwater were systematically investigated. This study systematically reveals the pollution risk of VOCs/SVOCs in landfill waste to groundwater and provides a scientific basis for the formulation of pollution control measures.

High biodegradability of microbially-derived dissolved organic matter facilitates arsenic enrichment in groundwater: Evidence from molecular compositions and structures

Although biodegradation of organic matter is well-known to trigger enrichment of arsenic (As) in groundwater, the effects of DOM sources and biodegradability on As enrichment remain elusive. In this study, groundwater samples were collected from the Hetao basin to identify DOM source and evaluate biodegradability by using spectral and molecular techniques. Results showed that in the alluvial fan, DOM was mainly sourced from terrestrially derived OM, while DOM in the flat plain was more originated from microbially derived OM. Compared to terrestrially derived DOMs, microbially derived DOMs in groundwater, which had relatively higher H/Cwa ratios, NOSC values and more biodegradable molecules, exhibited higher biodegradability. In the flat plain, microbially derived DOMs with higher biodegradability encountered stronger biodegradation, facilitating the reductive dissolution of Fe(III)/Mn oxides and As enrichment in groundwater. Moreover, the enrichment of As depended on the biodegradable molecules that was preferentially utilized for primary biodegradation. Our study highlights that the enrichment of dissolved As in the aquifers was closely associated with microbially derived DOM with high biodegradability and high ability for primary biodegradation.

The prediction of hydrolysis and biodegradation of organophosphorus-based chemical warfare agents (G-series and V-series) using toxicology in silico methods

Nerve agents (G- and V-series) are a group of extremely toxic organophosphorus chemical warfare agents that we have had the opportunity to encounter many times on a massive scale (Matsumoto City, Tokyo subway and Gulf War). The threat of using nerve agents in terrorist attacks or military operations is still present, even with establishing the Chemical Weapons Convention as the legal framework. Understanding their environmental sustainability and health risks is critical to social security. Due to the risk of contact with dangerous nerve agents and animal welfare considerations, in silico methods were used to assess hydrolysis and biodegradation safely. The environmental fate of the examined nerve agents was elucidated using QSAR models. The results indicate that the investigated compounds released into the environment hydrolyse at a different rate, from extremely fast (<1 day) to very slow (over a year); V-agents undergo slower hydrolysis compared to G-agents. V-agents turned out to be relatively challenging to biodegrade, the ultimate biodegradation time frame of which was predicted as weeks to months, while for G-agents, the overwhelming majority was classified as weeks. In silico methods for predicting various parameters are critical to preparing for the forthcoming application of nerve agents.