Chaojie Zhang

Quantitative characterization of short- and long-chain perfluorinated acids in solid matrices in Shanghai, China.

Perfluorinated acids (PFAs) have been recognized as emerging environmental pollutants because of their widespread occurrences, persistence, and bioaccumulative and toxicological effects. PFAs have been detected in aquatic environment and biota in China, but the occurrences of these chemicals have not been reported in solid matrices in China. In the present study, short- and long-chain PFAs (C2-C14) have been quantitatively determined in solid matrices including sediments, soils and sludge collected in Shanghai, China. The results indicate that sludge contains more PFAs than sediments and soils, and the total PFAs concentrations in sediments, soil and sludge are 62.5-276 ng g(-1), 141-237 ng g(-1) and 413-755 ng g(-1), respectively. In most cases, trifluoroacetic acid was the major PFA and accounted for 22-90% of the total PFAs. Although the levels of perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) were not only lower than trifluoroacetic acid, but also lower than some short-chain PFCAs (<C8) in some individual cases, PFOA and PFOS were still the major pollution compounds in most cases and they constituted 2-34% and 1-9% of the total PFAs, respectively. Meanwhile, unlike previous studies, PFOS levels were not always higher than PFOA in solids collected in Shanghai, China. Given that some short-chain PFAs such as trifluoroacetic acid are mildly phytotoxic and their higher levels in solid matrices were collected in Shanghai, China, these chemicals should be included in future environmental monitoring efforts.

Perfluoroalkyl acids in municipal landfill leachates from China: Occurrence, fate during leachate treatment and potential impact on groundwater

Raw and treated landfill leachate samples were collected from 5 municipal landfill sites in China to measure the concentrations and contamination profile of perfluoroalkyl acids (PFAAs) in leachate during different steps of treatment. The total concentration of PFAAs (∑PFAAs) ranged from 7280 to 292,000 ng L(-1) in raw leachate and from 98.4 to 282,000 ng L(-1) in treated leachate. The dominant compounds measured were PFOA (mean contribution 28.8% and 36.8% in raw and treated leachate, respectively) and PFBS (26.1% and 40.8% in raw and treated leachate, respectively). A calculation of mass flows during the leachate treatment processes showed that the fate of individual PFAAs was substance and treatment-specific. The Chinese national leakage of ∑PFAAs to groundwater from landfill leachate was estimated to be 3110 kg year(-1), which is a significant environmental release that is potentially threatening the sustainable use of groundwater as a drinking water source.

Short- and long-chain perfluorinated acids in sewage sludge from Shanghai, China.

Perfluorinated acids (PFAs) are the subject of increasingly intense environmental research. In this study, sewage sludge samples were collected from 25 wastewater treatment plants (WWTPs) in Shanghai, China to evaluate the levels and profile of C3-C14 PFAs. The results showed a ubiquitous PFAs contamination of sewage sludge in Shanghai with the total PFAs (∑PFAs) range of 126-809 ng g(-1)dw. Perfluorooctanoic acid (PFOA) was found to be the dominant PFA pollutant and its concentration ranged from 23.2 to 298 ng g(-1)dw, much higher than the levels in other countries. Moreover, concentrations of short-chain PFAs (<C6) in sewage sludge were considerable. Following sludge application in agricultural land, the concentrations of PFOA, and perfluorooctane sulfonate (PFOS) are predicted to be 1.08 and 7.53 ng g(-1)dw, respectively, much lower than the corresponding US EPA standards. Nevertheless, further studies are needed to explore the fate of PFAs in sludge-amended soils due to the persistence and bioaccumulation potential of these compounds.

Occurrence of perfluorinated alkyl substances in sediment from estuarine and coastal areas of the East China Sea

Perfluorinated alkyl substances (PFAS) have drawn much attention due to their environmental persistence, ubiquitous existence, and bioaccumulation potential. The occurrence and spatial variation of PFAS were investigated through collection of riverine and marine sediments from estuarine and coastal areas of the East China Sea. Among them, perfluorooctanesulfonic acid (PFOS), perfluoroheptanoic acid (PFHpA), and perfluorooctanoic acid (PFOA) were the three predominant PFAS with the highest detection frequencies in the sediment. PFOS up to 32.4xa0ngxa0g−1 dw and ∑PFAS up to 34.8xa0ngxa0g−1 dw were detected. Compared to other studies, high levels of PFOS were found in sediments from the East China Sea. PFHpA was also detected at higher frequency and concentration than those of other studies, which suggests point sources in this area. Concentrations of PFAS in riverine sediments were much higher than in marine sediments. Analysis of spatial variations presented overall decreasing trends of PFAS from inshore to offshore areas.

Effect of Alkaline Pre-Treatment on Waste Activated Sludge Solubilization and Anaerobic Digestion

In order to enhance the efficiency of anaerobic digestion, the effect of alkaline pre-treatment has been studied on waste activated sludge(WAS) from a wastewater treatment plant(WWTP) in Shanghai, China. The results indicated that sodium hydroxide strongly influenced the solubilization of sludge and subsequent anaerobic digestion. The COD and protein solubilization was most effective when sludge was pretreated at high pH value. At pH=12, COD solubilization achieved about 50%, which induced 40 times increase in SCOD from 200 mg/l to 8000 mg/l. But at low pH(pH les9), the degree of COD and protein solubilization was not significant. The subsequent anaerobic digestion was also improved by alkaline pre-treatment. WAS at higher pH resulted in a better removal of COD, further degradation of VS and larger production of methane. However, in the beginning of anaerobic digestion under condition pH=12, a inhibition period of one week occurred. Possible mechanisms of alkaline pre-treatment were also discussed.

Determination and Elimination of Matrix Effect in Analysis of Perfluorinated Acids Using High Performance Liquid Chromatography-Negative Electrospray Tandem Mass Spectrometry

Matrix effects, ionization enhancement or suppression, are always possible with the electrospray ionization technique and can significantly hamper the analysis of PFAs in complex environmental matrixes. The objective of this study is to determine and eliminate the matrix effects in analysis of sewage using high performance liquid chromatography-negative electrospray tandem mass spectrometry (HPLC-negative ESI-MS/MS). Standard addition, which involves spiking successive known quantities of a standard into the sample extracts and reanalyzing, are used for determination of the matrix effects, while correction using isotopically labeled internal standards and clean-up of sample extracts using dispersive carbon sorbent are used for elimination of matrix effects. The results indicate that ultra-short- (C2-3) and long-chain PFCAs (>C10) suffer ionization suppression, while medium-chain PFCAs (C4-10) and PFBS experience ionization enhancement; however, PFHxS and PFOS do not suffer significant matrix effects. Although internal standards, MPFOA and MPFOS, can effectively negate matrix effects for medium-chain PFCAs (C7-10), they are not suitable for some short- ( C10 PFCAs), which are eluted significantly earlier or later than their retention times, respectively. However, matrix effects of all analytes are significantly naegated by dispersive carbon sorbent because it can effectively remove the co-eluting interference compounds from SPE elution but not affect PFAs.

Feasibility Study on Adsorption of PFOA from Reuse Water by Powdered Activated Carbon

The feasibility of powdered activated carbon (PAC) as an adsorbent to eliminate the perfluorooctanoic acid (PFOA) in the water for reuse has been studied. PAC exhibits a high affinity to adsorb PFOA on its surface. More than 95% of PFOA can be adsorbed onto PAC surface at the first hour. For common reuse water, the most optical PAC concentration was 0.125 g/L. As illustrated by IR spectra, PAC is an economical and effective adsorbent in treatment and reuse of wastewater containing PFOA. The results obtained in the study helped in developing a new process in the water reuse system to eliminate PFOA, which established a theoretical foundation for PFOA physical removal technology.

Influence Factors of Nitrogenous Heterocyclic Compound-Pyridine Degradation under Anoxic Conditions

The anoxic degradation and removal of nitrogenous heterocyclic compound-pyridine and the effect of pH, C/N ratio, bio-ferric on degradation of pyridine were studied by flask-shaking tests. The results indicate that pyridine was removed through three steps. They are biosorption-desorption-biodegradation. The optimal range of pH was 7~9. The C/ N ratio was not affecting the reduction of pyridine greatly. Bio-ferric process can increase the degradation of pyridine, the best concentrations of bio-ferric was 5 mg/L. pyridine could used as the sole carbon and nitrogen sources for biodegradation.

Study on Influence Factors of Nitrogenous Heterocyclic Compound-Dimethylpyridine Degradation under Anoxic Conditions

The anoxic degradation and removal of nitrogenous heterocyclic compound-dimethlypyridine, and the effect of pH, C/N ratio, bio-ferric on degradation of dimethylpyridine were studied by flask-shaking tests. The results indicate that dimethylpyridine was removed through three steps. They are biosorption-desorption-biodegradation. The optimal range of pH was 7~8. The C/N ratio was not affecting the reduction of dimethylpyridine greatly. Bio-ferric process cannot increase the degradation of dimethylpyridine; Dimethylpyridine could use as the sole carbon and nitrogen sources for biodegradation.

Breakthrough Volumes of Perfluorocarboxylates in Using WAX Cartridges for Analysis of Sewage

Perfluorocarboxylates (PFCAs) are the subject of increasingly intense environmental research due to their persistence, bioaccumulation, toxicity, and global distribution. In order to determine wide chain length PFCAs simultaneously, weak anion exchange (WAX) cartridges have recently been used for solid phase extraction (SPE) in analysis of these chemicals in environmental water samples. However, given the conflicts between the limited ion-exchange capacity of WAX cartridges and the relatively large enrichment coefficient required for analysis of these low pollution level chemicals, it is crucial to select appropriate water sample volumes for specific WAX cartridges in order to ensure the recoveries for all analytes. The objective of this study is to determine the breakthrough volumes of short- and long-chain PFCAs in analysis of sewage using specific WAX cartridges (60 mg, 3 cc) for SPE. The results indicate that the occurrence of breakthrough is dependent on not only the sample volume but also the perfluorocarbon chain length of analytes. The breakthrough volumes for short-chain PFCAs ( C10) in present study. The relatively low recoveries of long- chain PFCAs (>C10) are mainly due to matrix effects rather than breakthrough because internal standard is not suitable for these chemical. Finally, the volume selected for loading on WAX cartridges (60 mg, 3 cc) in analysis of sewage is 200 mL in order to avoid breakthrough for short-chain PFCAs ( C10). Meanwhile, this volume also ensures the quantitation of these chemicals presented in sewage samples because enrichment coefficients are large enough.