The airborne occurrence, isomer profiles, and phase distribution of perfluoroalkyl acids (PFAAs), including perfluoroalkyl carboxylates (PFCAs) and sulfonates (PFSAs), have received little scientific attention to date. Here we collected gaseous and particulate phase (PM2.5) samples in China, between June and November 2013, using alkalized annular denuders and downstream filters toavoid sampling artefacts associated with traditional air sampling. We analysed the concentrations of 18 linear PFAAs and the branched isomers of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). Concentra- tions of total PFAAs were dominated by PFCAs, with a range of 6.6e610 pg/m3 in the gaseous phase and 2.3e290 pg/m3 in the particulate phase. Concentrations of total PFCAs were higher in summer than winter in both phases. Branched PFOA isomers accounted for 10e22% of total PFOA in the gaseous phase and 13e24% in the particulate phase, which is close to, but slightly lower than, their abundance in the commercial PFOA mixtures manufactured using the electrochemical fluorination (ECF) process. In con- tract, branched PFOS isomers accounted for 26-63% of total PFOS in the gaseous phase and 39-77% in the particulate phase, which is much higher than their abundance in commercial PFOS mixtures manufac- tured by ECF. Most PFCAs had mean particle-associated fractions (F) higher than 0.5. PFHxS had a much higher mean F (0.65) than linear PFOS (0.31). We hypothesise that PFAAs observed in Beijing air may originate from the local water bodies through processes such as aerosol generation, although trans- formation of precursors also contribute.
As the major producer and consumer of hydrofluorocarbons (HFCs), China is obligated to phase-down HFCs to mitigate global warming if China ratifies the Kigali Amendment (KA) to the Montreal Protocol. Based on historical HFCs consumption in each sector, here we estimated historical HFCs emissions with a bottom-up method, and projected the consumption baseline and schedule for HFCs phase-down in China under the KA and the corresponding potential for emission reduction. Results showed that China's HFCs consumption and emissions in 2017 were 164,000 t (311 Mt CO2-eq) and 108 Mt CO2-eq, respectively. HFCs consumption baseline was projected to be (724 ± 18) Mt CO2-eq in 2024, and China should take measures to phase-down HFCs by 2029, at the latest, to meet the requirements of the KA. HFCs consumption in 2050 under KA would reach the level of 2012–2013. Cumulative reduced consumption was estimated at 10.8 (10.1–11.6) Gt CO2-eq, and cumulative reduced emissions were estimated at 5.38 (4.90–5.64) Gt CO2-eq by 2050.
Abstract HFO-1234yf (2,3,3,3-tetrafluoropropene) was proposed as a mobile air conditioners (MACs) refrigerant worldwide. However, its atmospheric degradation product is the highly soluble and phytotoxic trifluoroacetic acid (TFA), which persists in aquatic environments. We used a global 3-D chemical transport model to assess the potential environmental effects resulting from complete future conversion of all MACs to HFO-1234yf in China, the United States and Europe. The annual mean atmospheric concentrations of HFO-1234yf were 2.62, 2.20 and 2.73 pptv, and the mean deposition rates of TFA were 0.96, 0.45 and 0.52 kg km-2 yr-1, in three regions. Regional TFA deposition sources mainly came from emissions within the same region. Annual TFA deposition in the North Pole region was lower than the global average and mainly originated from European emissions. A potential doubling in the future HFO-1234yf emissions in China mainly affected the local TFA depositions. The TFA concentrations in rainwater were strongly affected by the regional precipitation rates. North Africa and the Middle East, regions with scant rainfall had, extremely high TFA concentrations. The rainwater concentrations of TFA during individual rain events can exceed the level considered to be safe, indicating substantial potential regional risks from future HFO-1234yf use.
The ozone layer depletion and its recovery, as well as the climate influence of ozone-depleting substances (ODSs) and their substitutes that influence climate, are of interest to both the scientific community and the public. Here we report on the emissions of ODSs and their substitute from China, which is currently the largest consumer (and emitter) of these substances. We provide, for the first time, a comprehensive information on ODSs and replacement Hydrofluorocarbon (HFC) emissions in China starting from 1980 based on reported production and usage. We also assess the impacts (and costs) of controls on ODS consumption and emissions on the ozone layer (in terms of CFC-11-equivalent) and climate (in CO2-equivalent). In addition, we show that while China’s future ODS emissions are likely to be defined as long as there is full compliance with the Montreal Protocol, its HFC emissions through 2050 are very uncertain. Our findings imply that HFC controls over the next decades that are more stringent than those under the Kigali Amendment to the Montreal Protocol would be beneficial in mitigating global climate change.
Using coupled dynamic substance flow and environmental fate models, CiP-CAFE and BETR-Global, we investigated whether degradation of side-chain fluorotelomer-based polymers (FTPs), mostly in waste stocks (i.e., landfills and dumps), serves as a long-term source of fluorotelomer alcohols (FTOHs) and perfluoroalkyl carboxylates (PFCAs) to the global environment. The modelling results indicate that, in the wake of the worldwide transition from long-chain to short-chain products, in-use stocks of C8 FTPs will peak and decline afterwards while the in-use stocks of C6 FTPs and waste stocks of both FTPs will generally grow. FTP degradation in waste stocks is making an increasing contribution to FTOH generation, the bulk of which readily migrates from waste stocks and degrades into PFCAs in the environment; the remaining part of the generated FTOHs degrade in waste stocks, which makes those stocks reservoirs that slowly release PFCAs into the environment over the long run because of the low leaching rate and extr...
Discrepancies in emission estimates of carbon tetrachloride (CCl 4 , CTC), between bottom-up and top-down methods, have been shown since the 1990s at both the global and regional scale. This study estimates the emissions of China from 1992 to 2014 based on emission functions and aggregated activity information given reasonable uncertainties. The results show that emissions increase from 7.3Gg/yr (5.6–9.1Gg/yr at 95% confidential interval) to 14.0 (9.1–19.5) Gg/yr with a growth rate of 6.7 (1.9–11.4) %/yr during 1992–2002 and then decrease to a minimum of 4.3 (1.9–8.0) Gg/yr in 2011. More than 54% of the emissions during 1992–2009 are from the process agents sector. The estimates are comparable with those of other studies and those in this study based on observations during 2011–2014 using the interspecies correlation method. China's contribution to global emissions increases from 7.5% to 19.5% during 1992–2009, but the contribution is reduced to 9.9% and 8.0% in 2010 and 2011, respectively, indicating the effectiveness of compliance with the Montreal Protocol and its subsequent Amendments and Adjustments, whereby CTC emissions are phased-out. The results of this study are beneficial for narrowing the gap between bottom-up estimates and top-down emission calculations of CTC in China.
Many hydrofluorocarbons (HFCs) that are widely used as substitutes for ozone-depleting substances (now regulated under the Montreal Protocol) are very potent greenhouse gases (GHGs). China's past and future HFC emissions are of great interest because China has emerged as a major producer and consumer of HFCs. Here, we present for the first time a comprehensive inventory estimate of China's HFC emissions during 2005-2013. Results show a rapid increase in HFC production, consumption, and emissions in China during the period and that the emissions of HFC with a relatively high global warming potential (GWP) grew faster than those with a relatively low GWP. The proportions of China's historical HFC CO2-equivalent emissions to China's CO2 emissions or global HFC CO2-equivalent emissions increased rapidly during 2005-2013. Using the "business-as-usual" (BAU) scenario, in which HFCs are used to replace a significant fraction of hydrochlorofluorocarbons (HCFCs) in China (to date, there are no regulations on HFC uses in China), emissions of HFCs are projected to be significant components of China's and global future GHG emissions. However, potentials do exist for minimizing China's HFC emissions (for example, if regulations on HFC uses are established in China). Our findings on China's historical and projected HFC emission trajectories could also apply to other developing countries, with important implications for mitigating global GHG emissions.
There has been ever-increasing international interest in investigating the long-term emissions of chemicals in products (CiPs) throughout their entire life cycle in the anthroposphere. Hexabromocyclododecane (HBCDD) is a contemporary example of special interest due to the recent listing of this hazardous flame retardant in the Stockholm Convention and the consequent need for parties to take appropriate measures to eliminate this compound. Here, we conducted a scenario-based dynamic substance flow analysis, coupled with interval linear programming, to forecast the future HBCDD emissions in China in order to assist with the implementation of the Stockholm Convention in this current world's predominant HBCDD manufacturing and consuming country. Our results indicate that, under a business-as-usual scenario, the cumulative HBCDD production will amount to 238,000聽tonnes before its phase-out, 79% of which will be consumed in domestic market, accumulate as stocks in flame-retarded polystyrene insulation boards, and ultimately end up in demolition waste. While the production is scheduled to end in ca. 2021, emissions of HBCDD would continue until after 2100. For the entire simulation period 2000鈥2100, 44% of total cumulative emissions will arise from the industrial manufacture of HBCDD-associated end-products, whereas 49% will come from the end-of-life disposals of HBCDD-containing waste. The most effective end-of-life disposal option for minimizing emissions we found was, a pre-demolition screening combined with complete incineration. Our study warns of the huge challenges that China would face in its eliminating HBCDD contamination in the following decades, and provides an effective methodology for a wider range of countries to recognize and tackle their long-term emission problems of hazardous CiPs.
As China’s largest CO 2 emission source, power sector has a large scale of power exchange, which results in the issue of interprovincial CO 2 emissions transfer embodied in power transmission. Based on interprovincial detailed power exchange data, a bottom-up method which takes into account the fuel mix of exported electricity is developed to calculate provincial CO 2 emissions embodied in power transmission. Provincial CO 2 emissions from power sector associated in consumption perspective in 2007, 2010 and 2012 are analyzed and compared with those in production based perspective. The calculation shows that total CO 2 emissions embodied in interprovincial power exchange is 532 Tg in 2012, accounting for 14% of total emissions from power sector. The embodied emissions have risen by 94% between 2007 and 2012. The general transfer pathway of embodied CO 2 emissions is from eastern China to western China with long-range power transmission. The disparities between consumption and production based CO 2 emissions are significant in some provinces. The production based CO 2 emissions from power sector of Inner Mongolia are 195 Tg higher than those of the consumption based, while the consumption based emissions of Beijing are 484% larger than those of the production based. This study also reveals an increasing trend of CO 2 emissions from both production and consumption principles for most provinces over the period 2007–2012.
The uncertainties on whether dicofol can be identified as a persistent organic pollutant (POP) in terms of its long-range transport (LRT) potential and global distribution, are always a controversial topic during international regulation deliberations. The lack of monitoring data in remote background regions necessitates a model-based evaluation approach for assessing the global distribution of dicofol. However, few model simulations are available at present, as there is no inventory available for global historical usage of dicofol that has sufficiently high spatial and temporal resolution. To describe the current status of global emission, we first developed an inventory of global dicofol usage for the period of 2000-2012 at 1 degrees x 1 degrees latitude/longitude resolution. We then assessed the LRT potential of dicofol by calculating its Arctic Contamination Potential using the Globo-POP model. In addition, we simulated the global mass distribution and the fate of dicofol in the environment using the BETR-Global model at 15 degrees x 15 degrees latitude/longitude resolution. Our estimated inventory established that over the period of 13 years, a total of 28.2 kilo tonnes (kt) of dicofol was applied and released into the environment. East and Southeast Asia, the Mediterranean Coast, and Northern and Central America were identified as hotspots of usage and release. Dicofol exhibited a higher Arctic Contamination Potential than several confirmed Arctic contaminants, and a larger current volume of consumption than most existing POPs. The results of our BETR-Global simulation suggest that (i) dicofol can indeed be transported northward, most likely driven by both atmospheric and oceanic advections from source regions at midlatitudes, and (ii) dicofol will be enriched in remote background regions. Continuous use of dicofol in source regions will result in exposure both locally and in remote regions, and the examination of the potential for adverse effects is therefore of paramount importance. Proactive restrictions at the international level may be warranted.
Trifluoromethane (CHF3, HFC-23), with a 100-year global warming potential (GWP) of 12400, is regulated under the Kyoto Protocol. HFC-23 emissions in East Asia, especially in China, are currently thought to represent the majority of global HFC-23 emissions. This study provides both a bottom-up emission inventory and the multiannual top-down estimate of HFC-23 emissions in East Asia during 2007-2012. The new bottom-up inventory yields improved simulated HFC-23 mixing ratios compared to previous bottom-up inventories. The top-down estimate uses inverse modeling to further improve the model-measurement agreement. Results show that China contributed 94-98% of all HFC-23 emissions in East Asia. Annual a posteriori emissions from China were around 6.3 Gg/yr during the period 2007-2010 after which they increased to 7.1 +/- 0.7 Gg/yr in 2011 and 8.8 +/- 0.8 Gg/yr in 2012. For the first time, this study also provides a top-down estimate of HFC-23/HCFC-22 (chlorodifluoromethane, CHClF2) coproduction ratios in non-CDM (Clean Development Mechanism) HCFC-22 production plants as well as in all HCFC-22 production plants in China.