Further Insight into Extractable (Organo)fluorine Mass Balance Analysis of Tap Water from Shanghai, China.

The ubiquitous occurrence of per- and polyfluoroalkyl substances (PFAS) and the detection of unexplained extractable organofluorine (EOF) in drinking water have raised growing concerns. A recent study reported the detection of inorganic fluorinated anions in German river systems, and therefore, in some samples, EOF may include some inorganic fluorinated anions. Thus, it might be more appropriate to use the term "extractable fluorine (EF) analysis" instead of the term EOF analysis. In this study, tap water samples (n = 39) from Shanghai were collected to assess the levels of EF/EOF, 35 target PFAS, two inorganic fluorinated anions (tetrafluoroborate (BF4-) and hexafluorophosphate (PF6-)), and novel PFAS through suspect screening and potential oxidizable precursors through oxidative conversion. The results showed that ultra-short PFAS were the largest contributors to target PFAS, accounting for up to 97% of ΣPFAS. To the best of our knowledge, this was the first time that bis(trifluoromethanesulfonyl)imide (NTf2) was reported in drinking water from China, and p-perfluorous nonenoxybenzenesulfonate (OBS) was also identified through suspect screening. Small amounts of precursors that can be oxidatively converted to PFCAs were noted after oxidative conversion. EF mass balance analysis revealed that target PFAS could only explain less than 36% of EF. However, the amounts of unexplained extractable fluorine were greatly reduced when BF4- and PF6- were included. These compounds further explained more than 44% of the EF, indicating the role of inorganic fluorinated anions in the mass balance analysis.

Electrochemical degradation of per- and poly-fluoroalkyl substances using boron-doped diamond electrodes.

Electrochemical degradation using boron-doped diamond (BDD) electrodes has been proven to be a promising technique for the treatment of water contaminated with per- and poly-fluoroalkyl substances (PFAS). Various studies have demonstrated that the extent of PFAS degradation is influenced by the composition of samples and electrochemical conditions. This study evaluated the significance of several factors, such as the current density, initial concentration of PFAS, concentration of electrolyte, treatment time, and their interactions on the degradation of PFAS. A 24 factorial design was applied to determine the effects of the investigated factors on the degradation of perfluorooctanoic acid (PFOA) and generation of fluoride in spiked water. The best-performing conditions were then applied to the degradation of PFAS in wastewater samples. The results revealed that current density and time were the most important factors for PFOA degradation. In contrast, a high initial concentration of electrolyte had no significant impact on the degradation of PFOA, whereas it decreased the generation of F-. The experimental design model indicated that the treatment of spiked water under a current density higher than 14 mA cm-2 for 3-4 h could degrade PFOA with an efficiency of up to 100% and generate an F- fraction of approximately 40-50%. The observed high PFOA degradation and a low concentration of PFAS degradation products indicated that the mineralization of PFOA was effective. Under the obtained best conditions, the degradation of PFOA in wastewater samples was 44-70%. The degradation efficiency for other PFAS in these samples was 65-80% for perfluorooctane sulfonic acid (PFOS) and 42-52% for 6-2 fluorotelomer sulfonate (6-2 FTSA). The presence of high total organic carbon (TOC) and chloride contents was found to be an important factor affecting the efficiency of PFAS electrochemical degradation in wastewater samples. The current study indicates that the tested method can effectively degrade PFAS in both water and wastewater and suggests that increasing the treatment time is needed to account for the presence of other oxidizable matrices.

Occurrence and leachability of polycyclic aromatic compounds in contaminated soils: Chemical and bioanalytical characterization.

An important concern regarding sites contaminated with polycyclic aromatic compounds (PACs) is the risk of groundwater contamination by release of the compounds from soils. The goal of this study was to investigate the occurrence and leachability of 77 PACs including polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic compounds (NSO-PACs) among total aryl hydrocarbon receptor (AhR) agonists in soils from historical contaminated sites. A novel approach combining chemical and bioanalytical methods in combination with characterization of leachability by use of a column leaching test was used. Similar profiles of relative concentrations of PACs were observed in all soils, with parent PAHs accounting for 71 to 90% of total concentrations in soils. Contribution of oxy-PAHs, alkyl-PAHs and N-PACs ranged from 2 to 9%, 3 to 9% and 1 to 14%, respectively. Although the contributions of groups of PACs were small, some compounds were found in similar or greater concentrations than parent PAHs. Leachable fractions of 77 PACs from soils were small and ranged from 0.002 to 0.54%. Polar PACs were shown to be more leachable than parent PAHs. The contribution of analyzed PACS to overall AhR-mediated activities in soils and leachates suggests presence of other AhR agonists in soils, and a potential risk. Only a small fraction of AhR agonists was available in soils, indicating an overestimation of the risk if only total initial concentrations in soils would be considered in risk assessment. The results of the study strongly support that focus on 16US EPA PAHs may result in inadequate assessment of risk and hazard of PACs in complex environmental samples.

Re-cycling of remediated soil--evaluation of leaching tests as tools for characterization.

In Sweden, leaching tests with deionized water (D.W.) are utilized in risk assessment of materials entering landfills, but implementation of these results to evaluate the risk of spreading of pollutants in the environment is difficult. One problem is that most leaching procedures only consider heavy metals release, whereas organic pollutants are left out. The aim of the present study was to assess the possible pollutant mitigation in four remediated soils, three with heavy metals and one with polycyclic aromatic hydrocarbons (PAH) contamination. The mitigation was evaluated by standardized batch and column leaching tests utilizing three different leaching solutions: D.W., a weak ionic solution (0.001 M CaCl(2)) and an artificially made soil water (ASW). In general, batch leaching tests implied larger contaminant removal than column leaching test, possibly due to the more rough treatment of the soil particles, and guidelines would at times be exceeded by the batch leaching test but not by column leaching tests. Utilization of CaCl(2) was found to release less heavy metal than D.W., whereas the metals mobilized by ASW were removed from solution by the filtration of soil leachates. Low molecular weight PAH was most efficiently mobilized by CaCl(2), while D.W. worked better for high molecular weight PAH. Despite very low initial PAH-concentrations, tap- and groundwater criteria were exceeded by all leaching solutions.

Remediation of heavy metal contaminated soil washing residues with amino polycarboxylic acids.

Removal of Cu, Pb, and Zn by the action of the two biodegradable chelating agents [S,S]-ethylenediaminedisuccinic acid (EDDS) and methylglycinediacetic acid (MGDA), as well as citric acid, was tested. Three soil samples, which had previously been treated by conventional soil washing (water), were utilized in the leaching tests. Experiments were performed in batches (0.3 kg-scale) and with a WTC-mixer system (Water Treatment Construction, 10 kg-scale). EDDS and MGDA were most often equally efficient in removing Cu, Pb, and Zn after 10-60 min. Nonetheless, after 10d, there were occasionally significant differences in extraction efficiencies. Extraction with citric acid was generally less efficient, however equal for Zn (mainly) after 10d. Metal removal was similar in batch and WTC-mixer systems, which indicates that a dynamic mixer system could be used in full-scale. Use of biodegradable amino polycarboxylic acids for metal removal, as a second step after soil washing, would release most remaining metals (Cu, Pb and Zn) from the present soils, however only after long leaching time. Thus, a full-scale procedure, based on enhanced metal leaching by amino polycarboxylic acids from soil of the present kind, would require a pre-leaching step lasting several days in order to be efficient.

Laboratory and pilot scale soil washing of PAH and arsenic from a wood preservation site: changes in concentration and toxicity.

Soil washing of a soil with a mixture of both polycyclic aromatic hydrocarbons (PAH) and As was evaluated in laboratory and pilot scale, utilizing both single and mixtures of different additives. The highest level of decontamination was achieved with a combination of 0.213 M of the chelating agent MGDA and 3.2 x CMC* of a non-ionic, alkyl glucoside surfactant at pH 12 (Ca(OH)(2)). This combination managed to reach Swedish threshold values within 1 0 min of treatment when performed at elevated temperature (50 degrees C), with initial contaminant concentrations of As=105+/-4 mg/kg and US-EPA PAH(16)=46.0+/-2.3mg/kg. The main mechanisms behind the removal were the pH effect for As and a combination of SOM ionization as a result of high pH and micellar solubilization for PAHs. Implementation of the laboratory results utilizing a pilot scale equipment did not improve the performance, which may be due to the shorter contact time between the washing solution and the particles, or changes in physical characteristics of the leaching solution due to the elevated pressure utilized. The ecotoxicological evaluation, Microtox, demonstrated that all soil washing treatments increased the toxicity of soil leachates, possibly due to increased availability of contaminants and toxicity of soil washing solutions to the test organism.

Copper(II) binding to dissolved organic matter fractions in municipal solid waste incinerator bottom ash leachate.

Information on Cu speciation in municipal solid waste incineration (MSWI) bottom ash leachate is needed for Cu leaching predictions and toxicity estimates. The complexation of Cu with dissolved organic matter (DOM) in leachates from a stored MSWI bottom ash was studied potentiometrically using a Cu-ion selective electrode. More than 95% of the copper was bound to DOM in the hydrophilic fraction of the leachate, indicating that the hydrophilic acids contribute to Cu complex formation. The hydrophilic acids constituted 58% of the dissolved organic carbon in the ash leachate. Comparisons between experimental results and speciation calculations with the NICA-Donnan model and the Stockholm humic model indicated differences between the ash DOM and the natural DOM for which the models have been calibrated. The ratio of carboxylic binding sites to phenolic binding sites was 2 times larger in ash DOM, and the Cu-binding affinity of the former was stronger than accounted for by the generic Cu-binding parameters. The Cu-binding affinity of the phenolic sites, on the other hand, was weaker. When these parameters were adjusted, a good description of the experimental data was obtained.

Oxalate and ferricrocin exudation by the extramatrical mycelium of an ectomycorrhizal fungus in symbiosis with Pinus sylvestris.

Accurate estimates of mycelial exudation in time and space are crucial for the assessment of ectomycorrhizal involvement in biogeochemical processes. Knowledge of exudation from mycelia of ectomycorrhizal fungi is still limited, especially for fungi in symbiosis with a host. Pinus sylvestris seedlings colonized by Hebeloma crustuliniforme were grown in aseptic multicompartment dishes. This novel system enabled identification of exudates originating only from extramatrical mycelium. At harvest, hyphal density and numbers were estimated using microscopic imaging. A fractal geometric approach was adopted for calculation of exudation rates. The main compounds identified were oxalate and ferricrocin. The exudation rate for oxalate was 19 +/- 3 fmol per hyphal tip h(-1) (mean +/- standard error of the mean) or 488 +/- 95 fmol hyphal mm(-2) h(-1). Ferricrocin rates were approx. 10 000 times lower. The fractal dimension (D) of the mycelia was 1.4 +/- 0.1, suggesting an explorative growth. Potassium nutrition was a significant regulatory factor for ferricrocin but not oxalate. The results suggest that hyphal exudation may alter the chemical conditions of soil microsites and affect mineral dissolution. Calculations also indicated that oxalate exudation may be a significant carbon sink.