[en] Having advantages of low capacitance and low energy threshold, the PC-HPGe (Point-Contact High Purity Germanium) detector has found its application in the direct detection of WIMP (Weak Interaction Massive Particle) in CDEX (China Darkmatter Experiment). The MSE (Multi-Site Event) and SSE(Single-Site Event) discrimination methods of the PC-HPGe detector are introduced in this article, including their physical basis, the electronics system and the algorithms to implement them. Behaviors of the PC-HPGe detector are studied intensively through this research and finally the experimental results of the LE discrimination method are presented. (authors)

[en] Highlights: • Dynamically downscaled Technology Driver Model (TDM) projections are presented. • Widespread decreases in most pollutant concentrations over the U.S. by 2046–2050. • Increases in ozone concentrations due to background CH₄ and NO_x-VOC sensitivity. • Climate changes can either enhance or mitigate O₃ increases, but decrease PM_2.5. • Climate-emissions interplay varies depending on pollutant, season, and U.S. location. In Part II of this work we present the results of the downscaled offline Weather Research and Forecasting/Community Multiscale Air Quality (WRF/CMAQ) model, included in the “Technology Driver Model” (TDM) approach to future U.S. air quality projections (2046–2050) compared to a current-year period (2001–2005), and the interplay between future emission and climate changes. By 2046–2050, there are widespread decreases in future concentrations of carbon monoxide (CO), nitrogen oxides (NO_x = NO + NO₂), volatile organic compounds (VOCs), ammonia (NH₃), sulfur dioxide (SO₂), and particulate matter with an aerodynamic diameter ≤ 2.5 μm (PM_2.5) due mainly to decreasing on-road vehicle (ORV) emissions near urban centers as well as decreases in other transportation modes that include non-road engines (NRE). However, there are widespread increases in daily maximum 8-hr ozone (O₃) across the U.S., which are due to enhanced greenhouse gases (GHG) including methane (CH₄) and carbon dioxide (CO₂) under the Intergovernmental Panel on Climate Change (IPCC) A1B scenario, and isolated areas of larger reduction in transportation emissions of NO_x compared to that of VOCs over regions with VOC-limited O₃ chemistry. Other notable future changes are reduced haze and improved visibility, increased primary organic to elemental carbon ratio, decreases in PM_2.5 and its species, decreases and increases in dry deposition of SO₂ and O₃, respectively, and decreases in total nitrogen (TN) deposition. There is a tendency for transportation emission and CH₄ changes to dominate the increases in O₃, while climate change may either enhance or mitigate these increases in the west or east U.S., respectively. Climate change also decreases PM_2.5 in the future. Other variable changes exhibit stronger susceptibility to either emission (e.g., CO, NO_x, and TN deposition) or climate changes (e.g., VOC, NH₃, SO₂, and total sulfate deposition), which also have a strong dependence on season and specific U.S. regions.

[en] Highlights: • Total Hg released to the environment from coal combustion is estimated to be 38 Gg. • 71% of this Hg was released into the atmosphere, while 31% went to land and water. • Most of the Hg from coal combustion was released in Asia and Europe (32% each). • The fraction of Hg released to the air as elemental Hg has steadily increased. • In the year 2010 about 1 Gg of Hg was released worldwide to all media. Coal combustion is one of the largest contemporary sources of anthropogenic mercury (Hg). It releases geologically sequestered Hg to the atmosphere, and fly ash can contaminate terrestrial and aquatic systems. We estimate that coal combustion has released a cumulative total of 38.0 (14.8–98.9, 80% C.I.) Gg (gigagrams, 10⁹ g or thousand tonnes) of Hg to air, land, and water up to the year 2010, most of which (97%) has occurred since 1850. The rate of release has grown by two orders of magnitude from 0.01 Gg yr⁻¹ in 1850 to 1 Gg yr⁻¹ in 2010. Geographically, Asia and Europe each account for 32% of cumulative releases and an additional 18% is from North America. About 26.3 (10.2–68.3) Gg, 71% of the total, were directly emitted to the atmosphere, mostly from the industrial (45%) and power generation (36%) sectors, while the remainder was disposed of to land and water bodies. While Europe and North America were the major contributing regions until 1950, Asia has surpassed both in recent decades. By 2010, Asia was responsible for 69% of the total releases of Hg from coal combustion to the environment. Control technologies installed on major emitting sources capture mainly particulate and divalent Hg, and therefore the fraction of elemental Hg in emissions from coal combustion has increased over time from 0.46 in 1850 to 0.61 in 2010. About 11.8 (4.6–30.6) Gg of Hg, 31% of the total, have been transferred to land and water bodies through the disposal or utilization of Hg-containing combustion waste and collected fly ash/FGD waste; approximately 8.8 Gg of this Hg have simply been discarded to waste piles or ash ponds or rivers.

[en] When released to the biosphere, mercury (Hg) is very mobile and can take millennia to be returned to a secure, long-term repository. Understanding where and when Hg was released as a result of human activities allows better quantification of present-day reemissions and future trajectories of environmental concentrations. In this work, we estimate the time-varying releases of Hg in seven world regions over the 500 year period, 1510–2010. By our estimation, this comprises 95% of all-time anthropogenic releases. Globally, 1.47 Tg of Hg were released in this period, 23% directly to the atmosphere and 77% to land and water bodies. Cumulative releases have been largest in Europe (427 Gg) and North America (413 Gg). In some world regions (Africa/Middle East and Oceania), almost all (>99%) of the Hg is relatively recent (emitted since 1850), whereas in South America it is mostly of older vintage (63% emitted before 1850). Asia was the greatest-emitting region in 2010, while releases in Europe and North America have declined since the 1970s, as recognition of the risks posed by Hg have led to its phase-out in commercial usage. The continued use of Hg in artisanal and small-scale gold mining means that the Africa/Middle East region is now a major contributor. We estimate that 72% of cumulative Hg emissions to air has been in the form of elemental mercury (Hg⁰), which has a long lifetime in the atmosphere and can therefore be transported long distances. Our results show that 83% of the total Hg has been released to local water bodies, onto land, or quickly deposited from the air in divalent (Hg^II) form. Regionally, this value ranges from 77% in Africa/Middle East and Oceania to 89% in South America. Results from global biogeochemical modeling indicate improved agreement of the refined emission estimates in this study with archival records of Hg accumulation in estuarine and deep ocean sediment. (letter)

[en] Highlights: • The average lifetime of the China passenger vehicle has increased to 12.9 years. • The survival rate pattern is very different among four vehicle types. • The longer lifetime of fuel-inefficient vehicles would increase fuel consumption. -- Abstract: With the rapid growth of passenger vehicle stock, China faces serious environmental and energy security problems. To reduce and remove low-efficiency vehicles on the road in an effort to ensure vehicle safety and fuel efficiency, China updated its compulsory scrappage standard for motor vehicles in 2013. The new standard increases the scrappage VKT (vehicle kilometers traveled) limit from 500,000 km to 600,000 km and removes the upper vehicle age limit of 15 years for passenger vehicles. 2012–2016 National registration data and 1980–2016 annual sales data were used to examine the on-road vehicle age distribution and survival rate of China passenger vehicle. The results showed that the median vehicle lifetime (age at 50% survival rate) had increased by 2.4 years—from 10.5 years in 2012 to 12.9 years in 2016. Vehicle survival rate by vehicle purpose and vehicle type shows that compared to cars and cross passenger cars (mainly minibuses, which are variants of minivans with displacement no more than 1.0L), SUVs and MPVs have higher survival rates. The overall increase in vehicle lifetime and survival rate from 2012 to 2016 will increase total fuel consumption by 2.5%–3.7% in China.

[en] We evaluate the recently increasing tropospheric NO₂ columns in Northern China measured by the Ozone Monitoring Instrument (OMI) with an advanced power-plant NO_x emission inventory and the NASA INTEX-B emission inventory, using a global chemical transport model (GEOS-Chem). In areas with newly built power plants the modeled and OMI-retrieved summertime average tropospheric NO₂ columns increased by 55% and 47%, respectively, between 2005 and 2007. A monthly average increase of 1.79 Gg NO_x emissions is calculated to lead to an increase of 1.0 x 10¹⁵ molecules cm^-2 in the modeled NO₂ columns in the study areas. Good consistency (R² = 0.61, slope = 1.18, n = 14) between the increased modeled and OMI-retrieved summertime average NO₂ columns is found. These results suggest that NO_x emissions from large power plants in Northern China can be identified and quantified using OMI retrievals with confidence. The NASA INTEX-B emission inventory appears to underestimate the NO_x emissions from the industry and transportation sectors, making it more difficult to quantify power-plant emissions when they are co-located with large cities.

[en] Highlights: • Detailed technology-driven transportation emissions are presented for the U.S. • Transportation emissions are projected to decrease by 2046–2050 for the U.S. • On-road vehicles dominate emission changes of CO, NO_x, VOC, and NH₃. • On-road and non-road modes both contribute to SO₂ and particulate emission changes. • Overall good model performance for baseline 2005 WRF/CMAQ simulation. Emissions from the transportation sector are rapidly changing worldwide; however, the interplay of such emission changes in the face of climate change are not as well understood. This two-part study examines the impact of projected emissions from the U.S. transportation sector (Part I) on ambient air quality in the face of climate change (Part II). In Part I of this study, we describe the methodology and results of a novel Technology Driver Model (see graphical abstract) that includes 1) transportation emission projections (including on-road vehicles, non-road engines, aircraft, rail, and ship) derived from a dynamic technology model that accounts for various technology and policy options under an IPCC emission scenario, and 2) the configuration/evaluation of a dynamically downscaled Weather Research and Forecasting/Community Multiscale Air Quality modeling system. By 2046–2050, the annual domain-average transportation emissions of carbon monoxide (CO), nitrogen oxides (NO_x), volatile organic compounds (VOCs), ammonia (NH₃), and sulfur dioxide (SO₂) are projected to decrease over the continental U.S. The decreases in gaseous emissions are mainly due to reduced emissions from on-road vehicles and non-road engines, which exhibit spatial and seasonal variations across the U.S. Although particulate matter (PM) emissions widely decrease, some areas in the U.S. experience relatively large increases due to increases in ship emissions. The on-road vehicle emissions dominate the emission changes for CO, NO_x, VOC, and NH₃, while emissions from both the on-road and non-road modes have strong contributions to PM and SO₂ emission changes. The evaluation of the baseline 2005 WRF simulation indicates that annual biases are close to or within the acceptable criteria for meteorological performance in the literature, and there is an overall good agreement in the 2005 CMAQ simulations of chemical variables against both surface and satellite observations.