Accumulation of six PFAS compounds by woody and herbaceous plants: potential for phytoextraction.

Per and polyfluoroalkyl substances (PFAS) consist of a large group of compounds used to make products more resistant to stains, grease, and water and for fire suppression. They have been widely detected in the environment and exposure has been linked to adverse human health effects. Phytoremediation could be used to remediate PFAS-impacted sites, but there is little information on herbaceous and woody plant species uptake of PFAS compounds from soil. A greenhouse study evaluated the potential for eight herbaceous and seven woody plant species to absorb PFAS compounds. Six PFAS compounds: PFPeA, PFHxA, PFOA, PFBS, PFHxS, and PFOS were added weekly to irrigation water, and the plants grown for up to 14 weeks after an initial establishment period. Significant accumulation of all PFAS compounds occurred in at least one plant species. Mass recovery in above-ground tissue by the best performing plant ranged from a low of 3.8% for PFOS by Festuca rubra to a high of 42% for PFPeA by Schedonorus arundinaceus. Hyperaccumulation, defined as tissue/soil concentrations >10/1, was observed for all six PFAS compounds in at least one plant species. These results demonstrate the potential use of phytoremediation as a tool for remediating PFAS-contaminated sites.

Release of Electron Donors during Thermal Treatment of Soils.

Thermal treatment of soil and groundwater may provide an in situ source of soluble organic compounds and hydrogen (H2) that could stimulate microbial reductive dechlorination (MRD) at sites impacted by chlorinated solvents. The objectives of this study were to identify and quantify the release of electron donors and fermentable precursors during soil heating and to estimate availability of these compounds following thermal treatment. Fourteen solid materials containing <0.01 to 63.81 wt % organic carbon (OC) were incubated at 30, 60, or 90 °C for up to 180 d, leading to the release of direct electron donors (i.e., H2 and acetate) and fermentable volatile fatty acids (VFAs). Total VFA release ranged from 5 ± 0 × 10-9 carbon per gram solid (mol C/gs) during 30 °C incubation of quartz sand to 820 ± 50 × 10-6 mol C/gs during 90 °C incubation of humic acid, and was positively impacted by incubation time, temperature, and solid-phase OC content. H2 gas was detected at a maximum of 180 ± 50 × 10-9 mol H2/gs, accounting for less than 0.3% of reducing equivalents associated with VFAs released under the same conditions. These findings will allow for more reliable prediction of substrate release during thermal treatment, supporting the implementation of coupled thermal and biological remediation strategies.

Sediment pollution in an urban water supply lake in southern Brazil.

Urbanization and anthropogenic activities create many environmental issues in urban water supply reservoirs, especially in metropolitan regions. Thus, this study was carried out aiming to evaluate the variance in the physical-chemical characteristics of bottom sediment along the Lake Guaíba, Brazil. Lake Guaíba is a freshwater lake situated in a metropolitan region in southern Brazil, being the main water supply to the region. Surface sediment was evaluated to pH, electrical conductivity, particle-size, total organic carbon and nitrogen, metals and inorganic elements (Fe, Al, Ca, Ba, Sr, Co, Tl, Zn, Cu, Cr, Ni, Pb, Cd, and Hg), and organic compounds. The sediments in the Lake Guaíba show a wide range in the physical-chemical characteristics. Metals Zn, Cu, Cr, and Ni appear in higher concentrations near to the margin of southern Porto Alegre, where there was also more clay plus silt. Sediments of Lake Guaíba have physical-chemical variability by the settle tendency and water flow from the riverine to lacustrine areas. The sediment in Lake Guaíba had a median of: Zn, 132; Cu, 78; Cr, 42; Ni, 28; Pb, 33; Cd, 0.3; and Hg, 0.07 µg/g. Bed sediments of Lake Guaíba are polluted with Zn, Cu, Cr, and Ni, major in the east margin (near to Porto Alegre). The potential toxic metals and organic compounds found in Lake Guaíba are commonly reported in urban regions around the world. Those elements and compounds derive from many anthropic activities, as industries, sewage, and vehicles. With diffuse sources in the region, the pollution control in Lake Guaíba is very complex.

Eucalyptus urograndis and Pinus taeda enhance removal of chlorobenzene and benzene in sand culture: A greenhouse study.

Contamination of soils and groundwater by chlorobenzene and benzene is a common problem at industrial sites worldwide. Since chemical remediation techniques are rarely completely effective, remnants of these contaminants often persist at levels that can still influence ecosystem health. We evaluated the potential of Pinus taeda and Eucalyptus urograndis to accelerate the removal of these compounds from sand/water systems using a completely randomized block greenhouse experiment with a no-plant control. At 2-day intervals, we added a solution containing both chlorobenzene and benzene with the same concentration of 50 mg L(-1) (25 mg pot(-1)), and we monitored leachate concentrations daily. The planted treatments showed greater decrease of contaminants over time. In the absence of plants, the contaminant mass decreased 50-60% during each 2-day cycle; whereas, in the planted treatments the contaminant mass decreased 91-98%. At the end of the experiment the plant roots, leaves, and the sand-substrate each contained less than 1 mg kg(-1) of contaminants, which is ∼1% of the total contaminant mass added. In addition, we observed no tree mortality even at concentrations exceeding the aqueous solubility limit of both compounds. Our results suggest both trees are good candidates for remediating chlorobenzene and benzene in soils and groundwater.

Patterns of development and abnormalities among tadpoles in a constructed wetland receiving treated wastewater.

Constructed wetlands are promoted for effectiveness at treating wastewater and potential value as wildlife habitat; however, wildlife performance studies in treated wastewater wetlands are limited. We used repeated surveys of larval amphibians along three wetland systems and four reference sites to test the hypothesis that bullfrog tadpoles exposed to direct inputs of treated wastewater develop slower, show a higher frequency of abnormalities, and are smaller at metamorphosis compared to tadpoles from reference ponds. Bullfrog tadpoles from wastewater wetlands were similar in size at metamorphosis compared to tadpoles from reference sites; however, they did show a much higher frequency of abnormalities including severe edema, scoliosis, and extreme calcinosis of soft tissues. Calcinosis was novel to the literature on amphibian abnormalities, the most frequent abnormality, and restricted exclusively to treatment wetlands. Within the constructed wetlands, tadpole development was slower and the frequency of scoliosis and calcinosis was higher in those cells receiving direct inputs of treated wastewater. Our results suggest that portions of constructed wetlands that directly receive treated wastewater may be poor amphibian habitat.