Treatment of PFAS-containing landfill leachate using an enhanced contact plasma reactor.

A bench-scale plasma reactor was used to degrade poly- and perfluoroalkyl substances (PFAS) in landfill leachate samples obtained from three different locations. In the leachate samples before treatment, five long-chain, six short-chain perfluoroalkyl acids (PFAAs) and eight PFAA precursors were detected in a wide concentration range (~102 to 105 ng/L; total oxidizable precursors (TOP) ~106 ng/L). The concentration of perfluorooctane sulfonate (PFOS) plus perfluorooctanoic acid (PFOA) ranged between 2000 and 3000 ng/L. Plasma-based water treatment of 500 mL samples resulted in faster removal rates for longer-chain than shorter chain length PFAAs. Both PFOS and PFOA were removed to below United States Environmental Protection Agency's (USEPA's) health advisory concentration level (HAL) concentrations (<70 ng/L) in 10-75 min; 90% PFOA and PFOS removal was achieved in 10 min. Long-chain and short-chain PFAAs were removed by >99.9% and 10-99.9%, respectively. The removal rate constant (kPFOA+PFOS) for combined PFOA and PFOS ranged between 0.20 and 0.34 min-1. Overall, 60 ± 2% of the TOP concentration and 34 ± 2% of the TOC were removed. No effect of non-PFAS co-contaminants (e.g., total initial organic carbon concentration ~2000 mg/L) on the degradation efficiency was observed. Short-chain PFAA removal efficacy was enhanced by adding a cationic surfactant (cetrimonium bromide). Overall, the results indicate that plasma-based technology may be a viable technology for the treatment of PFAS-contaminated landfill leachates.

Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor.

"High-concentration" and "low-concentration" bench-scale batch plasma reactors were used to effectively degrade per- and polyfluoroalkyl substances (PFAS) at a high concentration (∼100 mg/L) and a low concentration (<1 µg/L), respectively, in ion exchange (IX) regenerant still bottom (SB) solutions. In the SBs, numerous PFAS were detected with a wide concentration range (∼0.01 to 100 mg/L; total oxidizable precursors (TOP) ∼4000 to 10000 mg/L). In the "high-concentration" plasma reactor, the concentrations of PFAS precursors and long-chain perfluoroalkyl acids (PFAAs) (≥6C for PFSAs and ≥8C for perfluorocarboxylic acids (PFCAs)) were decreased by >99.9% in 2 h, and short-chain PFAAs (<6C for perfluorocarboxylic acids (PFSAs) and <8C PFCAs) were decreased by >99% in 6 h of treatment. Subsequently, a "low concentration" plasma reactor was used to remove additional PFAAs. In this reactor, the addition of CTAB (cetrimonium bromide, a cationic surfactant) caused short-chain PFAAs, other than PFBA, to be removed to below detection limits in 90 min of treatment time. Overall, >99% of the TOP present in SBs was removed during the treatment. Fluorine recovery of 47 to 117% was obtained in six SB samples. Energy requirement (EE/O) for the treatment of PFOA and PFOS from SBs ranged from 380 to 830 kWh/m3.

Rapid Removal of Poly- and Perfluorinated Compounds from Investigation-Derived Waste (IDW) in a Pilot-Scale Plasma Reactor.

A pilot-scale plasma reactor installed into an 8 × 20 ft2 mobile trailer was used to rapidly and effectively degrade poly- and perfluoroalkyl substances (PFAS) from liquid investigation-derived waste (IDW; development and purge water from monitoring wells) obtained from 13 different site investigations at Air Force installations. In the raw water, numerous PFAS were detected in a wide concentration range (∼10-105 ng/L; total oxidizable precursors (TOP) ∼102-105 ng/L, total fluorine by combustion ion chromatography ∼102 to 5 × 106 ng F/L). The concentration of total PFAS (12 perfluorocarboxylic acids (PFCAs) and perfluoroalkyl sulfonates (PFSAs)) in the 13 samples ranged between 2.7 and 1440 µg/L and the concentration of perfluorooctane sulfonate (PFOS) plus perfluorooctanoic acid (PFOA) ranged between 365 and 73700 ng/L. Plasma-based water treatment resulted in rapid perfluoroalkyl acids (PFAAs) removal from 4 L individual IDW samples with faster rates for longer-chain PFCAs (C ≥ 8) and PFSAs (C ≥ 6) than for PFCAs and PFSAs of shorter chain length. In 9 of the 13 IDW samples, both PFOS and PFOA were removed to below United States Environmental Protection Agency's (USEPA's) health advisory concentration level (HAL) concentrations in <1 min, whereas longer treatment times (up to 50 min) were required for the remaining four IDW samples due to either extremely high solution electrical conductivity, which decreased the plasma-liquid contact area (one IDW sample) or high concentrations of PFAAs and their precursors; the latter was found to be converted to PFAAs during the treatment. Overall, 36-99% of the TOP concentration present in the IDWs was removed during the treatment. There was no effect of non-PFAS co-contaminants on the degradation efficiency. Overall, the results indicate that plasma-based water treatment is a viable technology for the treatment of PFAS-contaminated IDW.

Breakdown Products from Perfluorinated Alkyl Substances (PFAS) Degradation in a Plasma-Based Water Treatment Process.

Byproducts produced when treating perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) in water using a plasma treatment process intentionally operated to treat these compounds slowly to allow for byproduct accumulation were quantified. Several linear chain perfluoroalkyl carboxylic acids (PFCAs) (C4 to C7) were identified as byproducts of both PFOA and PFOS treatment. PFOA, perfluorohexanesulfonate (PFHxS), and perfluorobutanesulfonate (PFBS) were also found to be byproducts from PFOS degradation. Significant concentrations of fluoride ions, inorganic carbon, and smaller organic acids (trifluoroacetic acid, acetic acid, and formic acid) were also identified. In addition to PFCAs, PFHxS, and PFBS, trace amounts of 43 PFOA-related and 35 PFOS-related byproducts were also identified using a screening and search-based algorithm. Minor concentrations of gas-phase byproducts were also identified (<2.5% of the F originally associated with the parent molecules) some of which are reported for the first time in perfluoroalkyl substance degradation experiments including cyclic perfluoroalkanes (C4F8, C5F10, C6F12, C7F14, and C8F16). The short chain PFCAs detected suggest the occurrence of a stepwise reduction of the parent perfluoroalkyl substances (PFAS) molecule, followed by oxidation of intermediates, perfluoroalkyl radicals, and perfluoro alcohols/ketones. Using a fluorine mass balance, 77% of the fluorine associated with the parent PFOA and 58% of the fluorine associated with the parent PFOS were identified. The bulk of the remaining fluorine was determined to be sorbed to reactor walls and tubing using sorption experiments in which plasma was not generated.

Seasonal variation of the dominant allergenic fungal aerosols - One year study from southern Indian region.

Quantitative estimations of fungal aerosols are important to understand their role in causing respiratory diseases to humans especially in the developing and highly populated countries. In this study we sampled and quantified the three most dominantly found allergenic airborne fungi, Aspergillus fumigatus, Cladosporium cladosporioides, and Alternaria alternata from ambient PM10 samples using the quantitative PCR (qPCR) technique in a southern tropical Indian region, for one full year. Highest concentrations of A. fumigatus and C. cladosporioides were observed during monsoon whereas A. alternata displayed an elevated concentration in winter. The meteorological parameters such as temperature, relative humidity, wind speed, and precipitation exhibited a substantial influence on the atmospheric concentrations of allergenic fungal aerosols. The morphological features of various allergenic fungal spores present in the PM10 were investigated and the spores were found to possess distinct structural features. In a maiden attempt over this region we correlate the ambient fungal concentrations with the epidemiological allergy occurrence to obtain firsthand and preliminary information about the causative fungal allergen to the inhabitants exposed to bioaerosols. Our findings may serve as an important reference to atmospheric scientists, aero-biologists, doctors, and general public.

Removal of 2,4-dichlorophenoxyacetic acid in aqueous solution by pulsed corona discharge treatment: Effect of different water constituents, degradation pathway and toxicity assay.

A multiple pin-plane corona discharge reactor was used to generate plasma for the degradation of 2,4 dichlorophenoxyacetic acid (2,4-D) from the aqueous solution. The 2,4-D of concentration 1 mg/L was completely removed within 6 min of plasma treatment. Almost complete mineralization was achieved after the treatment time of 14 min for a 2,4-D concentration of 10 mg/L. Effects of different water constituents such as carbonates, nitrate, sulphate, chloride ions, natural organic matter (humic acids) and pH on 2,4-D degradation was studied. A significant antagonistic effect of carbonate and humic acid was observed, whereas, the effects of other ions were insignificant. A higher first order rate constant of 1.73 min-1 was observed, which was significantly decreased in the presence of carbonate ions and humic acids. Also, a higher degradation of 2,4-D was observed in acidic pH conditions. Different 2,4-D intermediates were detected and the degradation pathway of 2,4-D in plasma treatment process was suggested. The toxicity of 10 mg/L 2,4-D was completely eradicated after 10 min of plasma treatment.

Rapid degradation, mineralization and detoxification of pharmaceutically active compounds in aqueous solution during pulsed corona discharge treatment.

In the present study, plasma generated by pulsed corona discharge was used for the degradation of diclofenac, carbamazepine and ciprofloxacin. Pollutants in aqueous solution were plasma treated under two categories: single and mixed pollutant condition. Mixed pollutant condition showed an antagonistic behaviour and thus the degradation time was higher for mixed condition compared to the single condition. At different voltage and frequencies, degradation efficiency followed the trend, diclofenac>carbamazepine>ciprofloxacin. Acidic pH slightly favoured the degradation process whereas in presence of radical scavengers (HCO3-, CO32- and humic acid) the degradation yield was significantly decreased. With an input power of 101.5 W, complete degradation was achieved within 4-16 min of plasma treatment for pharmaceutical's concentrations of 1-10 mg/L. As the pollutant concentration increased from 1 to 10 mg/L, the pseudo first order rate constant decreased, while yield increased. Complete degradation pathway of diclofenac, carbamazepine and ciprofloxacin in plasma treatment process are proposed by identifying the intermediates using LC-MS analysis. TOC analysis confirmed 80% mineralization within 10 min of plasma treatment for higher pharmaceutical's concentrations of 10 mg/L. The microalgae ecotoxicity study and disc diffusion test confirmed the complete detoxification of PACs that took place after 6 min of plasma treatment.

Terrestrial Macrofungal Diversity from the Tropical Dry Evergreen Biome of Southern India and Its Potential Role in Aerobiology.

Macrofungi have long been investigated for various scientific purposes including their food and medicinal characteristics. Their role in aerobiology as a fraction of the primary biological aerosol particles (PBAPs), however, has been poorly studied. In this study, we present a source of macrofungi with two different but interdependent objectives: (i) to characterize the macrofungi from a tropical dry evergreen biome in southern India using advanced molecular techniques to enrich the database from this region, and (ii) to assess whether identified species of macrofungi are a potential source of atmospheric PBAPs. From the DNA analysis, we report the diversity of the terrestrial macrofungi from a tropical dry evergreen biome robustly supported by the statistical analyses for diversity conclusions. A total of 113 macrofungal species belonging to 54 genera and 23 families were recorded, with Basidiomycota and Ascomycota constituting 96% and 4% of the species, respectively. The highest species richness was found in the family Agaricaceae (25.3%) followed by Polyporaceae (15.3%) and Marasmiaceae (10.8%). The difference in the distribution of commonly observed macrofungal families over this location was compared with other locations in India (Karnataka, Kerala, Maharashtra, and West Bengal) using two statistical tests. The distributions of the terrestrial macrofungi were distinctly different in each ecosystem. We further attempted to demonstrate the potential role of terrestrial macrofungi as a source of PBAPs in ambient air. In our opinion, the findings from this ecosystem of India will enhance our understanding of the distribution, diversity, ecology, and biological prospects of terrestrial macrofungi as well as their potential to contribute to airborne fungal aerosols.