Soil and groundwater contamination and remediation

Microbial consortia capable of completely removing and defluorinating two persistent fluorinated fungicides, epoxiconazole (EPO) and fludioxonil (FLU), were enriched from an estuarine sediment and an agriculture soil. The enrichments were conducted along 6 months, during which the fungicides were supplemented individually to the cultures every 21 days at 5 mgL-1, using sodium acetate as a co-metabolite (fed twice a week at 400 mgL-1). Biodegradation of EPO and FLU was detected early on the enrichment phase and a gradual increase on their performances was observed throughout this period. After ca. 5 months, the complete removal and defluorination of EPO and FLU was observed for all cultures in a period of 10-15 days. These biodegradation efficiencies were found to be similar in the absence of a co-metabolite. The two pesticides were efficiently biodegraded at concentrations up to 10 mgL-1. By estimating the biodegradation kinetics of the enriched consortia, it was possible to determine half-life values significantly lower than those reported in the literature for these pesticides, rendering EPO and FLU as non-recalcitrant under these experimental conditions. 16S rDNA analysis showed that these consortia harbor bacteria belonging to the Proteobacteria phylum. Current work is focused on the optimization of the degrading consortia and on the elucidation of the metabolic pathways of these pesticides.

Geochemical modelling is an essential tool to understand the water-rock interaction processes. In this work has been used the reaction path modelling to investigate the release and fate of geogenic Cr in ophiolitic Italian areas. During the water-rock interaction the geogenic trivalent Cr hosted in Cr-bearing minerals (serpentine minerals, spinels, pyroxene, etc.) of serpentinites rocks is oxidized in Cr (VI) highly toxic, resulting largely dangerous for environment and human health. This geochemical modelling was performed varying Fe2O3/(FeO+Fe2O3) weight ratios considering the trivalent Fe the main oxidant present in suitable amounts in serpentinite rock. The reaction paths reproduces the analytical concentrations of relevant solutes, including Cr(VI), in the Mg-HCO3 groundwaters hosted in the ophiolitic aquifers of Italy.

PFAS compounds are ubiquitous in the environment and in consumer products. Unlike other emergent contaminants this is a family of compounds with, literally, thousands members. Our knowledge of toxicological and environmental fate and transport properties is an evolving field. On the other hand, regulatory limits (when they exist) are extremely low and address only a limited handful of compounds. Because of their physical-chemical properties there are unconventional migration pathways, such as sewer exfiltration and biosolids residuals, that complicate site assessment and site closure. Surveys to date in Greece are fragmented and very limited in scope and focus. The objective of this study is to discuss how professional judgement should be used to collect appropriate data to both define the nature and extent of impact and to assess whether receptors may be adversely impacted and how to select an appropriate remedy, if mitigation of those impacts is warranted.

Per - and polyfluoroalkyl substances (PFAS) are a group of environmental contaminants, that are dispersed throughout the world. A number of areas have been affected by their persistence and biomagnification. PFAS remediation of contaminated material requires extensive knowledge of the species involved. A method to simplify the study of the thermal degradation of PFAS is presented in this paper, providing a solution to experimental and analytical challenges. A three-zone furnace allowed manipulation of both reaction temperature and gas flowrate (and consequently residence time). The PFAS compound could be charged and vaporised in a separate zone. Adopting this experimental methodology, a kinetic model describing the decomposition of the PFAS can be devised. When reacting under an inert nitrogen atmosphere, perfluorooctanoic acid (PFOA) degraded at temperatures above 450 °C. The products observed were found to be hydrofluoric acid (HF) and carbon dioxide (CO2), along with a perfluoro-1-heptene species. Additional products of 1H-perfluorohexane or 1H-perfluoroheptane were also observed when residence times were increased. The effect of water vapour was also investigated, with similar behaviour to pyrolysis being observed, where a significantly higher concentration of HF was detected under otherwise similar reaction conditions. These preliminary results suggest water vapour accelerates the rate of PFAS decomposition.

As a big agricultural country，China has a relatively high pesticide usage in unit area , which is three times higher than developed countries. About 80% of pesticides directly enter the soil and the water through leaching or surface runoff during the usage of pesticides. In particular, some of the polar compounds are easier to migrate than other compounds, causing pollution of surface water and groundwater. The groundwater samples in Hebei Province, a major agriculture province in China, were screened by multi-residue liquid chromatography-tandem mass spectrometry for two consecutive years in 2014 and 2015. The results showed that among 44 polar compounds, 27 pesticides were detected in 2014 and 19 in 2015. Atrazine-desethyl-desisopropyl, 2,4-D and fomesafen were 434.3 ng/L, 711.5 ng/L and 508.2 ng/L respectively, which were significantly higher than those in other provinces in China. Atrazine and its metabolites were detected in both years. Except for Atrazine-desethyl-desisopropyl, other components were detected in high concentration in 2014. The detected concentrations of bentazone, hexaconazole, triadimenol, and triazolone were similar in the two years. Pesticides such as methomyl, isopropyl, diniconazole and imazethapyr were detected in 2014, but not in 2015, which is presumably related to the actual use of pesticides.