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As technological advances allow the development of new products, the number of synthetic chemical compounds released into the soil, surface water and groundwater increases, posing a threat to the environment. Therefore, treatability studies to improve bioremediation strategies (biostimulation and bioaugmentation) were applied to samples of soil containing nitro and chlorinated aromatic compounds from a former chemical manufacturing site in Brazil. Native microorganisms were stimulated to degrade compounds including dichloroanilines, dichloronitrobenzenes, 2-chloronitrobenzene, and 1,2-chlorobenzene, through oxygen exposure and pH (6.0-8.4) and moisture content (13-23%) adjustments. For the inoculation of soil samples, a culture enriched from site groundwater was developed. The aeration alone stimulated the indigenous microbes to degrade some of the compounds. However, reinoculation with an enriched culture and moisture content adjustment increased the attenuation rates by 3.6 and 1.4 times, respectively. The pH values in the range of 7.6 and 8.4 seem not to harm microbes' activity and moisture content higher than 16% is recommended to enhance biodegradation. Based on the findings, it is likely that natural attenuation is happening in aerobic zones at the site. Results indicate both bioremediation strategies (biostimulation and bioaugmentation through reinoculation with enriched culture mainly composed of organisms from the Diaphorobacter genus) are promising strategies to enhance bioremediation. However, considering the applicability of the strategies on a field scale, further experiments will broaden the understanding of biodegradability of compounds, such as their inhibitory effects when in higher concentration (>150 mg/kg), individually or combined.

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Compound specific isotope analysis (CSIA) is an established tool to demonstrate in situ degradation of traditional groundwater contaminants at heavily contaminated sites, usually at mg/L range aqueous concentrations. Currently, an efficient preconcentration method is lacking to expand CSIA to low aqueous concentration environmental samples. This work demonstrated the compatibility of polar organic chemical integrative sampler (POCIS) with CSIA of C, H, and N isotopes for four NH2- and NO¬2-substituted chlorobenzenes at low μg/L. Diffusion and sorption showed insignificant carbon isotope fractionation (<0.7‰) in laboratory experiment, except for a reproducible shift of 1.6‰ for 3,4-dichloronitrobenzene. A similar constant reproducible shift of 0.8-2‰ was evident for N-CSIA. Whereas, the compatibility of POCIS for H-CSIA seems to be analyte specific possibly reflecting the adsorption mechanism to POCIS by H-bonding. Performance of the POCIS-CSIA method was evaluated in a pilot constructed wetland where comparable C- and N-CSIA results were obtained from grab sampling and POCIS. This work opens the potential of CSIA application to the low concentration polar emerging contaminants in the environment, such as pesticides, pharmaceuticals, and flame-retardants.

2,4-Dinitroanisole (DNAN) is a toxic compound increasingly used by the military that can be released into the environment on the soil of training fields and in the wastewater of manufacturing plants. DNAN's nitro groups are anaerobically reduced to amino groups by microorganisms when electron donors are available. Using anaerobic sludge as the inoculum, we tested different electron donors for DNAN bioreduction at 20 and 30 °C: acetate, ethanol, pyruvate, hydrogen, and hydrogen + pyruvate. Biotic controls without external electron donors and abiotic controls with heat-killed sludge were also assayed. No DNAN conversion was observed in the abiotic controls. In all biotic treatments, DNAN was reduced to 2-methoxy-5-nitroaniline (MENA), which was further reduced to 2,4-diaminoanisole (DAAN). Ethanol or acetate did not increase DNAN reduction rate compared to the endogenous control. The electron donors that caused the fastest DNAN reductions were (rates at 30 °C): H2 and pyruvate combined (311.28 ± 10.02 μM·d−1·gSSV−1), followed by H2 only (207.19 ± 5.95 μM·d−1·gSSV−1), and pyruvate only (36.35 ± 2.95 μM·d−1·gSSV−1). Raising the temperature to 30 °C improved DNAN reduction rates when pyruvate, H2, or H2 + pyruvate were used as electrons donors. Our results can be applied to optimize the anaerobic treatment of DNAN-containing wastewater.