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.
This paper investigates how government size affects tax evasion in China. Using matched county-firm data for 1998-2005, we estimate the impact of county government size on the relationship between a firm's reported profit and imputed profit based on the national income accounts. A larger government is found to be correlated with more severe tax evasion, especially for state-owned and collectively-owned firms. Such an effect is stronger when local governance become worse. This paper shows that a large government does not bring about a strong state capacity to enforce tax rules at the local level in China.
Shen X, Zou L, Özsu TM, Chen L, Li Y, Han S, Zhao D. A graph-based RDF triple store, in 31st IEEE International Conference on Data Engineering, ICDE 2015, Seoul, South Korea, April 13-17, 2015.; 2015:1508–1511. [pdf]
A graphene-based vacuum transistor (GVT) with a high ON/OFF current ratio is proposed and experimentally realized by employing electrically biased graphene as the electron emitter. The states of a GVT are switched by tuning the bias voltage applied to the graphene emitter with an ON/OFF current ratio up to 10(6), a subthreshold slope of 120 mV dec(-1) and low working voltages of <10 V, exhibiting switching performances superior to those of previously reported graphene-based solid-state transistors. GVTs are fabricated and integrated using silicon microfabrication technology. A perfectly symmetric ambipolar device is achieved by integrating two GVTs, implying the potential of realizing vacuum integrated circuits based on GVTs. GVTs are expected to find applications in extreme environments such as high temperature and intense irradiation.
The heterogeneous chemistry of glyoxal on sulfuric acid surfaces has been investigated at various acid concentrations and temperatures, utilizing a low-pressure fast flow laminar reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS). The uptake coefficient (gamma) of glyoxal ranges from (1.2 +/- 0.06) x 10(-2) to 2.5 +/- 0.01) x 10(-3) for 60-93 wt % H2SO4, at 253-273 K. The effective Henry's Law constant (H*) ranges from (98.9 +/- 4.9) x 10(5) to (1.6 +/- 0.1) x 10(5) M atm(-1) for 60-93 wt % at 263-273 K. Both the uptake coefficient and Henry's Law constant increase with decreasing acid coneenttation and temperature. Our results reveal a reaction Mechanism of hydration followed by oligomerization for glyoxal on acidic media, indicating an efficient aqueous reaction of glyoxal on hygroscopic particles leading to secondary organic aerosol formation.
Hydrogen peroxide (H2O2) and organic peroxides play important roles in the cycle of oxidants and the formation of secondary aerosols in the atmosphere. Recent field observations have suggested that the budget of peroxyacetic acid (PAA, CH3C(O)OOH) is potentially related to the aerosol phase processes, especially to secondary aerosol formation. Here, we present the first laboratory measurements of the uptake coefficient of gaseous PAA and H2O2 onto ambient fine particulate matter (PM2.5) as a function of relative humidity (RH) at 298 K. The results show that the PM2.5, which was collected in an urban area, can take up PAA and H2O2 at the uptake coefficient (r) of 10-4, and bothg rPAA and rH2O2 increase with increasing RH. The value of rPAA at 90%RH is 5.4±1.9 times that at 3%RH, whereas rH2O2 at 90%RH is 2.4±0.5 times that at 3%RH, which suggests that PAA is more sensitive to the RH variation than H2O2 is. Considering the larger Henry’s law constant of H2O2 than that of PAA, the smaller RH sensitivity of the H2O2 uptake coefficient suggests that the enhanced uptake of peroxide compounds on PM2.5 under humid conditions is dominated by chemical processes rather than dissolution. Considering that mineral dust is one of the main components of PM2.5 in Beijing, we also determined the uptake coefficients of gaseous PAA and H2O2 on authentic Asian Dust storm (ADS) and Arizona Test Dust (ATD) particles. Compared to ambient PM2.5, ADS shows a similar value and RH dependence in its uptake coefficient for PAA and H2O2, while ATD gives a negative dependence on RH. The present study indicates that, in addition to the mineral dust in PM2.5, other components (e.g., soluble inorganic salts) are also important to the uptake of peroxide compounds. When the heterogeneous reaction of PAA on PM2.5 is considered, its atmospheric lifetime is estimated to be 3.0 h on haze days and 7.1 h on non-haze days, values that are in good agreement with the field observations.
Since 1995, 1,1,1,2-tetrafluoroethane (CH2FCF3, HFC-134a) has become the most important substitute of CFC-12 in mobile air conditioning (MAC) in China and MAC sector has dominated all the emissions of HFC-134a. In this study, we developed an accurate, updated and county-level inventory of the HFC-134a emissions from MAC in China for the period of 1995–2030 with an improved bottom-up method. Our estimation indicated that the total HFC-134a emissions kept growing at increase rates of ∼100% per year for 1995–2000 and ∼34% per year for 2001–2010. In 2010, HFC-134a emissions from MAC in China reached 16.7 Gg (10.5–22.7 Gg at 95% confidential interval), equivalent to 21.7 Tg CO2 (CO2-eq). Furthermore, the emissions in China estimated in this study accounted for 9.8% of global HFC-134a emissions and 29.0% of total emissions from Non-Annex_I countries in 2010. Due to the more advanced social-economic conditions and more intensive ownership of automobiles, greater HFC-134a were observed to come from big cities in East China. Under a Business-as-usual (BAU) Scenario, projected emissions will grow to 89.4 (57.9–123.9) Gg (about 75.3–161.1 Tg CO2-eq) in 2030, but under an Alternative Scenario, 88.6% of the projected emissions under BAU scenario could be curbed. Our estimation demonstrates huge emission mitigation potential of HFC-134a in China's MAC sector.
High-harmonic gyrotrons are challenging to generate high interaction efficiency and simultaneously suppress the mode competition. Investigation in this paper reveals that a high-Q cavity is potential to realize high efficiency in a 94-GHz third-harmonic TE02 mode gyrotron. Unfortunately, the high-Q cavity exhibits severe mode competition from the lower harmonic modes. A start-up scenario of active parameter control is employed to suppress the mode competition. The third-harmonic TE02 mode gyrotron finally achieves the steady single-mode operation with efficiency up to 20%. The physical mechanism during the mode formation process is theoretically investigated according to frequency-domain and time-domain nonlinear theories. The theoretical investigation in this paper is of guidance for future developing high-harmonic gyrotrons, especially toward terahertz applications.