Zihan Zhai

Estimating industrial and domestic environmental releases of perfluorooctanoic acid and its salts in China from 2004 to 2012

China has been documented as one of the few remaining producers of perfluorooctanoic acid and its salts (PFOA/PFO) and the worlds major contamination hotspot. However, limited information has been available for evaluating their environmental releases in China and the contribution to global PFOA/PFO burden. Here we present the first source-specific inventory for environmental releases of PFOA/PFO in China from 2004 to 2012, using a bottom-up approach for industrial sources and an inverse approach for domestic sources. Our results show that China became the current worlds largest PFOA/PFO emitter, with cumulative environmental releases reaching 250tonnes (t) over the period of nine years. The eastern region was identified as the hotspot of environmental releases. Most of the national environmental releases were due to the activities of the fluorochemical industry (94.0%) rather than domestic use of PFOA/PFO-related consumer products (6.0%). Fluoropolymer manufacturing and processing, a dominating industrial source, contributed 83.7% of the national environmental releases. In contrast to the general decline trends in annual industrial environmental releases of PFOA/PFO in most industrialized countries, the trend increased in China because of the expansion of production as a result of the global geographical transition in fluorochemical industry. Based on these results, we recommend that the future reduction options are required in industrial sector in China.

Estimated emissions of chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons based on an interspecies correlation method in the Pearl River Delta region, China.

Although many studies have been conducted in recent years on the emissions of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs) at the large regional (such as East Asia) and national scales, relatively few studies have been conducted for cities or metropolitan areas. In this study, 192 air samples were collected in the Pearl River Delta (PRD) region of China in November 2010. The atmospheric mixing ratios of six halocarbons were analyzed, including trichlorofluoromethane (CFC-11, CCl3F), dichlorodifluoromethane (CFC-12, CCl2F2), monochlorodifluoromethane (HCFC-22, CHClF2), 1,1-dichloro-1-fluoroethane (HCFC-141b, CH3CCl2F), 1-dichloro-1,1-fluoroethane (HCFC-142b, CH3CClF2), and 1,1,1,2-tetrafluoroethane (HFC-134a, CH2FCF3), and their emissions were estimated based on an interspecies correlation method using HCFC-22 as the reference species. The results showed no significant change in the regional concentration and emission of CFC in the past 10years, suggesting that the continuous regional emission of CFC has had no significant effect on the CFC regional concentration in the PRD region. Concentrations and emissions of HCFCs and HFCs are significantly higher compared to previous research in the PRD region (P<0.05). The largest emission was for HCFC-22, most likely due to its substitution for CFC-12 in the industrial and commercial refrigeration subsector, and the rapid development of the room air-conditioner and extruded polystyrene subsectors. The PRDs ODP-weighted emissions of the target HCFCs provided 9% (7-12%) of the national emissions for the corresponding species. The PRDs GWP-weighted emissions of the target HCFCs and HFC-134a account for 10% (7-12%) and 8% (7-9%), respectively, of the national emissions for the corresponding species, and thus are important contributions to Chinas total emissions.

A 17-fold increase of trifluoroacetic acid in landscape waters of Beijing, China during the last decade

The concentrations of trifluoroacetic acid (TFA) were measured in urban landscape waters, tap water and snows in Beijing, China in 2012. Compared with the 2002 measurements, a 17-fold increase from 23-98ngL(-1) to 345-828ngL(-1) was observed for TFA concentrations in urban landscape waters, and an obvious increase from not detected (n.d.) to 155ngL(-1) occurred to TFA in tap water. By flux estimation between air and water interface, the remarkable increase of TFA was attributable to dry and wet deposition. The quantitative water-air-sediment interaction (QWASI) model simulated TFAs in various environmental media and showed that, over 99% of TFA distributed in water bodies. Our results recommend that measures are needed to control the increase of TFA in China.

Airborne trifluoroacetic acid and its fraction from the degradation of HFC-134a in Beijing, China.

Trifluoroacetic acid (TFA) has been attracting increasing attention worldwide because of its increased environmental concentrations and high aquatic toxicity. Atmospheric deposition is the major source of aquatic TFA, but only a few studies have reported either air concentrations or deposition fluxes for TFA. This is the first study to report the atmospheric concentrations of TFA in China, where an annular denuder and filter pack collection system were deployed at a highly urbanized site in Beijing. In total, 144 air samples were collected over the course of 1 year (from May 2012 to April 2013) and analyzed directly using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) or following derivatization by gas chromatography-mass spectrometry (GC-MS). The annual mean atmospheric concentration of TFA was 1580 ± 558 pg/m(3), higher than the previously reported annual mean levels in Germany and Canada. For the first time, it was demonstrated that maximum concentrations of TFA were frequently observed in the afternoon, following a diurnal cycle and suggesting that a major source of airborne TFA is likely degradation of volatile precursors. Using a deposition model, the annual TFA deposition flux was estimated to be 619 ± 264 μg m(-2) year(-1). Nevertheless, a box model estimated that the TFA deposition flux from the degradation of HFC-134a contributed only 14% (6-33%) to the total TFA deposition flux in Beijing. Source analysis is quite important for future TFA risk predictions; therefore, future research should focus on identifying additional sources.

Determination of Gaseous and Particulate Trifluoroacetic Acid in Atmosphere Environmental Samples by Gas Chromatography-Mass Spectrometry

Abstract Trifluoroacetic acid (TFA) were determined in air samples by a sampling device composed of annular denuders coupled with a quartz filter, which was efficient for the collection and separation of gaseous and particulate TFA. Gaseous TFA was performed by means of annular denuders coated with alkaline solution, while particulate TFA was absorbed by quartz filters. TFA can be determined by gas chromatography-mass spectrometer after derivatizated with 2,4-difluoroaniline. Calibration curves were linear with correlation coefficients of 0.9991. Detection limit of TFA was 66 ng L −1 , which was 31 pg m −3 when sampling volume was 48 m 3 . Recoveries of the TFA sampling device ranged from 98% to 105% with relative standard deviation (RSD) ≤ 3%. The developed method was applied to the determination of TFA in atmosphere samples collected in Peking University in Beijing in 2012. Total TFA concentrations ranged from 501 to 7447 pg m −3 . Concentrations of gaseous TFA were significantly higher than those of particulate, and the gas-particle partition coefficient of TFA decreased as air temperature rose.

Effects of metal ions on the catalytic degradation of dicofol by cellulase

A new technique whereby cellulase immobilized on aminated silica was applied to catalyze the degradation of dicofol, an organochlorine pesticide. In order to evaluate the performance of free and immobilized cellulase, experiments were carried out to measure the degradation efficiency. The Michaelis constant, Km, of the reaction catalyzed by immobilized cellulase was 9.16 mg/L, and the maximum reaction rate, Vmax, was 0.40 mg/L/min, while that of free cellulase was Km=8.18 mg/L, and Vmax=0.79 mg/L/min, respectively. The kinetic constants of catalytic degradation were calculated to estimate substrate affinity. Considering that metal ions may affect enzyme activity, the effects of different metal ions on the catalytic degradation efficiency were explored. The results showed that the substrate affinity decreased after immobilization. Monovalent metal ions had no effect on the reaction, while divalent metal ions had either positive or inhibitory effects, including activation by Mn2+, reversible competition with Cd2+, and irreversible inhibition by Pb2+. Ca2+ promoted the catalytic degradation of dicofol at low concentrations, but inhibited it at high concentrations. Compared with free cellulase, immobilized cellulase was affected less by metal ions. This work provided a basis for further studies on the co-occurrence of endocrine-disrupting chemicals and heavy metal ions in the environment.

Response to Comment on "Airborne trifluoroacetic acid and its fraction from the degradation of HFC-134a in Beijing, China″.

Fraction from the Degradation of HFC-134a in Beijing, China′′ W thank Dr. Wallington and his esteemed coauthors for taking an interest in this manuscript in which we estimated that, in Beijing, the fraction of airborne trifluoroacetic acid (TFA) coming from the degradation of HFC-134a was only 14% (6−33%). This was a surprising finding that is strengthened by the overall conservative approach that we used. Specifically, for the molar yield of TFA from HFC-134a we adopted the high end (0.36) of the range (0.29−0.36) that Kanakidou et al. presented in their 3-dimensional tropospheric study. Wallington and colleagues have correctly pointed out that, based on some of their own follow-up experimental work in smog chambers, the actual molar yield of TFA from HFC134a may be significantly lower; owing to C−C scission of the CF3CFHO radical when it is formed from exothermic reaction of NO with the corresponding peroxy radical, CF3CFHO2. 4 Therefore, we accept that the true fraction of TFA from HFC-134a is closer to the low end of our estimated range. We furthermore agree that the comment from Wallington et al. strengthens one of the main conclusions and suggestions of our paper, that sources of TFA, other than HFC-134a oxidation, are present in the air over Beijing, and these need to be identified. Jing Wu†,‡ Jonathan W. Martin Zihan Zhai† Keding Lu† Li Li† Xuekun Fang† Hangbiao Jin Jianxin Hu† Jianbo Zhang*,† †State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China ‡China Waterborne Transport Research Institute, Beijing, China Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada

Distribution of trifluoroacetic acid in gas and particulate phases in Beijing from 2013 to 2016

Trifluoroacetic acid (TFA) was measured at an urban site in Beijing from April 2013 to April 2016 and examined its characteristics and particle/gas distributions. The average monthly atmospheric TFA concentration fluctuated significantly and presented marked seasonal variations. The concentration levels of gas-phase TFA were significantly higher in spring and summer than in fall and winter. The PM2.5 mass concentration and ambient temperature were important factors affecting the concentration of particulate-phase TFA. Hence, at higher PM2.5 concentrations and lower temperatures, atmospheric TFA tended to be enriched in particulate matter. Our findings suggest that the percentage of gas-phase TFA in Beijing is higher than that in the steady state; thus, gas-phase TFA can still be transformed to the particulate phase and increase the contribution of TFA to haze formation.