Metabolomic analysis to define and compare the effects of PAHs and oxygenated PAHs in developing zebrafish.

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives are ubiquitously present in diesel exhaust, atmospheric particulate matter and soils sampled in urban areas. Therefore, inhalation or non-dietary ingestion of both PAHs and oxy-PAHs are major routes of exposure for people; especially young children living in these localities. While there has been extensive research on the parent PAHs, limited studies exist on the biological effects of oxy-PAHs which have been shown to be more soluble and more mobile in the environment. Additionally, investigations comparing the metabolic responses resulting from parent PAHs and oxy-PAHs exposures have not been reported. To address these current gaps, an untargeted metabolomics approach was conducted to examine the in vivo metabolomic profiles of developing zebrafish (Danio rerio) exposed to 4 µM of benz[a]anthracene (BAA) or benz[a]anthracene-7,12-dione (BAQ). By integrating multivariate, univariate and pathway analyses, a total of 63 metabolites were significantly altered after 5 days of exposure. The marked perturbations revealed that both BAA and BAQ affect protein biosynthesis, mitochondrial function, neural development, vascular development and cardiac function. Our previous transcriptomic and genomic data were incorporated in this metabolomics study to provide a more comprehensive view of the relationship between PAH and oxy-PAH exposures on vertebrate development.

Transport stability of pesticides and PAHs sequestered in polyethylene passive sampling devices.

Research using low-density polyethylene (LDPE) passive samplers has steadily increased over the past two decades. However, such research efforts remain hampered because of strict guidelines, requiring that these samplers be quickly transported in airtight metal or glass containers or foil wrapped on ice. We investigate the transport stability of model pesticides and polycyclic aromatic hydrocarbons (PAHs) with varying physicochemical properties using polytetrafluoroethylene (PTFE) bags instead. Transport scenarios were simulated with transport times up to 14 days with temperatures ranging between -20 and 35 °C. Our findings show that concentrations of all model compounds examined were stable for all transport conditions tested, with mean recoveries ranging from 88 to 113 %. Furthermore, PTFE bags proved beneficial as reusable, lightweight, low-volume, low-cost alternatives to conventional containers. This documentation of stability will allow for more flexible transportation of LDPE passive samplers in an expanding range of research applications while maintaining experimental rigor.

Application of a magnesium/co-solvent system for the degradation of polycyclic aromatic hydrocarbons and their oxygenated derivatives in a spiked soil.

This study evaluates the capability, efficacy and practicality of a combined approach based on solvent extraction and chemical reduction to simultaneously degrade polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives (OPAHs) in spiked soil. The spiked soil was washed using a composite organic solvent consisting of ethanol and ethyl lactate (1:1, v/v) and then degradation of the extracted contaminants using zero-valent magnesium. The extraction conditions were optimized at 25 °C with solvent-soil ratio of 2:1 (v/w) and the ensuing degradation efficiency ranged from 79% to 88% for the OPAHs, and 66% to 87% for the PAHs after 24 h of reaction at pH of 6.1. The reductive degradation of the spiked contaminants followed pseudo-first-order kinetics; however, comparing the kinetic results of this study to soil-free studies, the degradation rates are significantly reduced. It can be inferred that extracted organic or inorganic components from the soil medium hinder the degradation process, possibly by reducing the reactivity of the activated metal. Furthermore, to our understanding, this study is the first report on the simultaneous degradation of these priority pollutants and their oxygenated derivatives. The experimental results encourage the application of this magnesium/co-solvent system for future pilot-scale remediation studies.

Multivariate evaluation and optimization of an activated-magnesium/co-solvent system for the reductive degradation of polycyclic aromatic hydrocarbons.

The present study evaluates the capability of an activated-magnesium metal and protic co-solvents to promote the reductive degradation of three different polycyclic aromatic hydrocarbons, specifically pyrene, benzo[k]fluoranthene and benzo[g,h,i]perylene. Multivariate analyses demonstrated that the kinetics of degradation was affected by several experimental factors such as magnesium loading, acid addition and solubility of the compounds. It was determined that an acid activator is needed for the degradation reaction to proceed and it is also noted that the use of a 1:1 ethanol/ethyl lactate co-solvent is ideal for the complete dissolution of all three compounds with concentrations varying from 200 to 275mgL(-1). The experimental results also indicate that, at room temperature conditions, only 0.05-0.1g of magnesium is required in order to achieve greater than 93% degradation efficiency after 24h of reaction. This methodology is attractive and may allow for the development of an economic and environmentally friendly field application for the remediation of other polycyclic aromatic hydrocarbons.

Reductive degradation of oxygenated polycyclic aromatic hydrocarbons using an activated magnesium/co-solvent system.

This study evaluates the capability of zero-valent magnesium and a protic co-solvent to promote the degradation of oxygenated polycyclic aromatic hydrocarbons compounds, specifically 9-fluorenone, 9,10-anthraquinone, 7,12-benz(a)anthraquionone, and 7H-benz(de)anthracene-7-one. At room temperature conditions, greater than 86% degradation efficiency is observed after 24h of reaction time for a mixture containing 0.05 g of magnesium and four selected oxygenated aromatic hydrocarbons with 250 mg L(-1) concentrations. It is noted that glacial acetic acid is needed as an activator for the degradation reaction to proceed. It is also presumed that the acid removes oxide and hydroxide species from the magnesium surface. With the GC-MS analysis of the reaction products, possible reductive pathways are suggested. Furthermore, this study is the first report on the degradation of these emerging contaminants and it is proposed that the magnesium-powder/protic-solvent system is a promising low-cost reagent and may allow for the future development of an economic and environmentally-friendly remediation application.

Reduction of benzo[a]pyrene with acid-activated magnesium metal in ethanol: a possible application for environmental remediation.

Persistent organic pollutants (POPs) are a well-known threat to the environment. Substances such as polycyclic aromatic hydrocarbons (PAHs) in contaminated soils and sediments can have severe and long-term effects on human and environmental health. There is an urgent need for the development of safe technologies for their effective degradation. Here we present a new technique using ball-milled magnesium powder and ethanol solvent as a convenient electron transfer/proton source for the partial reduction of PAHs under ambient conditions. The rates of degradation were determined while evaluating the influences of acetic acid and type of ball-milled magnesium added to the reaction mixture. The results of these triplicate studies indicate that with the use of acetic acid as an activator and ball-milled magnesium carbon (Mg/C), this reducing system (Mg-EtOH) is able to achieve a 94% conversion of 250 µg/mL of toxic benzo[a]pyrene into a mixture of less toxic and partially hydrogenated polycyclic compounds within 24h. This methodology can be used as a combined process involving ethanol washing followed by reduction reaction and it can also be considered as an easy handling and efficient alternative process to the catalytic hydrogenation of PAHs.