This study explores a bibliometric approach to quantitatively assessing current research trends on volatile organic compounds, by using the related literature in the Science Citation Index (SCI) database from 1992 to 2007. The articles acquired from such literature were concentrated on the general analysis by scientific output, the research performances by countries, institutes, and collaborations, and the research trends by the frequency of author keywords, words in title, words in abstract, and keywords plus. Over the past years, there had been a notable growth trend in publication outputs, along with more participation and collaboration of countries and institutes. Research collaborative papers had shifted from the national inter-institutional to the international collaboration. Benzene, toluene, and formaldehyde were the three kinds of VOCs concerned mostly. Detection and removing, especially by adsorption and oxidation, of VOCs were to be the orientation of all VOCs research in the next few years.
Understanding the origin of fine particulate matter is essential to proposing proper strategies for heavy haze mitigation in Shanghai, China. In this study we used the Particulate Matter Source Apportionment Technology in Comprehensive Air Quality Model with Extensions to quantify the impacts of emissions on the concentrations of fine particulate matter (PM 2.5 ) and its important components in Shanghai during heavy haze episodes in late autumn (6-22 November 2010). The factors considered here are regions of Shanghai and its surrounding areas, long-range regional transport, and different local emission categories. The results indicate that industrial process is the dominant local contributor to total PM 2.5 mass in the whole city except that at the urban center vehicle emission contributes slightly more. In addition, industrial process and vehicle emission are the major local contributors for nitrate in Shanghai, although at urban core the contribution from vehicle emission is remarkably larger. Generally, both local contribution and regional transport contribution could dominate a severe haze event in late autumn. However, the dominant contributor could either be local emission or regional transport, usually depending on the meteorological conditions. Therefore, particular attentions should be paid to the emission control in the upwind adjacent provinces, as well as in local areas, for developing effective strategies to reduce PM 2.5 pollution in Shanghai.
Wind erosion in arid and semi-arid areas is an important global environmental issue, and changes in wind speed trends over time play a key role in wind erosion dynamics. In a warming climate, scientists have recently observed a widespread decline in wind speed, termed "stilling". Here, we apply the Revised Wind Erosion Equation Model (RWEQ) to simulate the variability of wind erosion and quantify the impact of wind speed changes on soil degradation dynamics over the eastern agro-pastoral transitional zone of Northern China from 1982 to 2016. Our results show that a significant (i.e., p<0.05) decrease (-0.007 m s-1 year-1) of near-surface wind speed was observed annually, with significant declining trends in spring (-0.010 m s-1 year-1)and autumn (-0.009 m s-1 year-1). At the same time, wind erosion simulations reveal a negative trend for the annual soil loss from wind erosion (-6.20 t hectare-2 year-1 , p<0.05; affecting 99.8% of the study region), with significant declining trends in all seasons, particularly in spring (-3.49 t hectare-2 year-1) and autumn (-1.26 hectare-2 year-1). Further, we isolate the effects of wind variability on wind erosion from 1982 to 2016 by the model variable control method. This shows that wind speed variability strongly weakens wind erosion at-8.14 t hectare-2 year-1 (p<0.05) annually, with the strongest stilling recorded in spring leading to major decreases of wind erosion in spring (-4.77 t hectare-2 year-1 , p<0.05). Meanwhile, the weakest stilling in summer had the opposite influence on wind erosion (+0.40 t hectare-2 year-1 , p<0.10). To summarize, our findings have shown a significant impact of wind stilling on the decline of soil erosion rates in Northern China.
Assessing change in daily maximum wind speed and its likely causes is crucial for many applications such as wind power generation and wind disaster risk governance. Multidecadal variability of observed near-surface daily maximum wind speed (DMWS) from 778 stations over China is analyzed for 1975–2016. A robust homogenization protocol using the R package Climatol was applied to the DMWS observations. The homogenized dataset displayed a significant (p < 0.05) declining trend of −0.038 m s−1 decade−1 for all China annually, with decreases in winter (−0.355 m s−1 decade−1, p < 0.05) and autumn (−0.108 m s−1 decade−1; p < 0.05) and increases in summer (+0.272 m s−1 decade−1, p < 0.05) along with a weak recovery in spring (+0.032 m s−1 decade−1; p > 0.10); that is, DMWS declined during the cold semester (October–March) and increased during the warm semester (April–September). Correlation analysis of the Arctic Oscillation, the Southern Oscillation, and the west Pacific modes exhibited significant correlation with DMWS variability, unveiling their complementarity in modulating DMWS. Further, we explored potential physical processes relating to the atmospheric circulation changes and their impacts on DMWS and found that 1) overall weakened horizontal airflow [large-scale mean horizontal pressure gradient (from −0.24 to +0.02 hPa decade−1) and geostrophic wind speed (from −0.6 to +0.6 m s−1 decade−1)], 2) widely decreased atmospheric vertical momentum transport [atmospheric stratification thermal instability (from −3 to +1.5 decade−1) and vertical wind shear (from −0.4 to +0.2 m s−1 decade−1)], and 3) decreased extratropical cyclones frequency (from −0.3 to 0 month decade−1) are likely causes of DMWS change.
Near-surface (10 m) wind speed (NWS) plays a crucial role in e.g. hydrological cycles, wind energy production and air pollution, but what drives their multi-decadal changes is still unclear. Using reanalysis datasets and Coupled Model Inter-comparison Projection Phase 6 (CMIP6) model simulations, this study investigates recent trends in the annual mean NWS. The results show that the northern hemisphere (NH) terrestrial NWS experienced significant (p<0.1) decreasing trends during 1980–2010, when the southern hemisphere (SH) ocean NWS was characterized by significant (p<0.1) upward trends. However, during 2010–2019, global NWS trends shifted in their sign: NWS trends over the NH land became positive, and trends over the SH tended to be negative. We propose that the strengthening of SH NWS during 1980–2010 was associated with intensified Hadley cell over the SH, while the declining of NH land NWS could have been caused by changes in atmospheric circulation, alteration of vegetation/land-use and the accelerating Arctic warming. The CMIP6 model simulations further demonstrate that the greenhouse gas (GHG) warming plays an important role in triggering the NWS trends over the two hemispheres during 1980–2010 through modulating meridional atmospheric circulation. This study also points at the importance of anthropogenic GHG forcing and the natural Pacific Decadal Oscillation to the long-term trends and multi-decadal variability in global NWS, respectively.
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