6 results on '"Guangyi Xu"'
Search Results
2. The decay of silver nanoparticles in preoxidation process
- Author
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Zhen Yuan, Bojie Yuan, Jingyu Wang, Minghao Sui, Guangyi Xu, and Jie Qin
- Subjects
inorganic chemicals ,Environmental Engineering ,education ,Inorganic chemistry ,02 engineering and technology ,010501 environmental sciences ,01 natural sciences ,Silver nanoparticle ,Metal ,chemistry.chemical_compound ,Environmental Chemistry ,Humic acid ,Hydrogen peroxide ,Waste Management and Disposal ,Dissolution ,health care economics and organizations ,0105 earth and related environmental sciences ,chemistry.chemical_classification ,technology, industry, and agriculture ,respiratory system ,021001 nanoscience & nanotechnology ,Pollution ,Potassium permanganate ,chemistry ,visual_art ,Sodium hypochlorite ,visual_art.visual_art_medium ,Water treatment ,0210 nano-technology - Abstract
To investigate the fate of metal-based nanoparticles in water oxidation treatment processes, the decay of Ag-NPs in the presence of three kinds of water treatment preoxidants, sodium hypochlorite (NaClO), hydrogen peroxide (H2O2) and potassium permanganate (KMnO4), was investigated in this work. Dissolution of Ag-NPs into silver ions (Ag+) was found to occur under exposure to NaClO, H2O2 and KMnO4. The morphology of Ag-NPs changed after reacting with NaClO, H2O2 and KMnO4. Factors affecting the decay of Ag-NPs, i.e., the dosage of oxidants, pH, the presence of humic acid, typical ions in water, and the size of the nanoparticles, were investigated. A higher dosage of oxidants, the presence of calcium ions, and lower size of Ag-NPs promoted the decay of Ag-NPs. The presence of humic acid and sulfide ions inhibited the decay of Ag-NPs. The decay of Ag-NPs under exposure to oxidants was significantly affected by the pH. The mechanism of the Ag-NPs in the presence of oxidants under different environmental conditions is also discussed.
- Published
- 2018
3. Substantial nitrogen oxides emission reduction from China due to COVID-19 and its impact on surface ozone and aerosol pollution
- Author
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Wendell W. Walters, Xuyan Liu, Jiali Shao, Yuepeng Pan, Qianqian Zhang, Qianyin Ni, Yuexin He, Guangyi Xu, and Chunlai Jiang
- Subjects
Pollution ,China ,Environmental Engineering ,Ozone ,010504 meteorology & atmospheric sciences ,Coronavirus disease 2019 (COVID-19) ,media_common.quotation_subject ,Pneumonia, Viral ,Air pollution ,010501 environmental sciences ,medicine.disease_cause ,Atmospheric sciences ,01 natural sciences ,Article ,Control strategy ,Betacoronavirus ,chemistry.chemical_compound ,Air Pollution ,medicine ,Humans ,Environmental Chemistry ,Pandemics ,Waste Management and Disposal ,NOx ,0105 earth and related environmental sciences ,media_common ,Aerosols ,Air Pollutants ,SARS-CoV-2 ,Emission intensity ,Aerosol ,chemistry ,NOx emissions ,Environmental science ,Nitrogen Oxides ,Particulate Matter ,Coronavirus Infections ,Covid-19 ,Environmental Monitoring - Abstract
A top-down approach was employed to estimate the influence of lockdown measures implemented during the COVID-19 pandemic on NOx emissions and subsequent influence on surface PM2.5 and ozone in China. The nation-wide NOx emission reduction of 53.4% due to the lockdown in 2020 quarter one in China may represent the current upper limit of China's NOx emission control. During the Chinese New Year Holiday (P2), NOx emission intensity in China declined by 44.7% compared to the preceding 3 weeks (P1). NOx emission intensity increased by 20.3% during the 4 weeks after P2 (P3), despite the unchanged NO2 column. It recovered to 2019 level at the end of March (P4). The East China (22°N - 42°N, 102°E - 122°E) received greater influence from COVID-19. Overall NOx emission from East China for 2020 first quarter is 40.5% lower than 2019, and in P4 it is still 22.9% below the same period in 2019. The 40.5% decrease of NOx emission in 2020 first quarter in East China lead to 36.5% increase of surface O3 and 12.5% decrease of surface PM2.5. The elevated O3 promotes the secondary aerosol formation through heterogeneous pathways. We recommend that the complicated interaction between PM2.5 and O3 should be considered in the emission control strategy making process in the future., Graphical abstract Unlabelled Image, Highlights • NOx emission in the lockdown period is 53.4% lower than the same period in 2019. • East China experienced greater influence from COVID-19 than national mean level. • NOx decline leads to 36.5% O3 increase and 12.5% PM2.5 decrease over East China. • Elevated O3 enhances secondary aerosols formation through heterogeneous pathway.
- Published
- 2021
4. Foliage/atmosphere exchange of mercury in a subtropical coniferous forest in south China
- Author
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Shuxiao Wang, Jiming Hao, Mariah Taylor, Charles T. Driscoll, Yao Luo, Lei Duan, Guangyi Xu, and Mengshu Shao
- Subjects
Atmospheric Science ,Biogeochemical cycle ,Pinus massoniana ,010504 meteorology & atmospheric sciences ,Meteorology ,Soil Science ,chemistry.chemical_element ,010501 environmental sciences ,Aquatic Science ,01 natural sciences ,0105 earth and related environmental sciences ,Water Science and Technology ,Transpiration ,Tree canopy ,Ecology ,biology ,Paleontology ,Forestry ,biology.organism_classification ,Mercury (element) ,Deposition (aerosol physics) ,chemistry ,Environmental chemistry ,Soil water ,Environmental science ,Terrestrial ecosystem - Abstract
Foliage/atmosphere exchange is an important pathway of deposition and loss in the biogeochemical mercury (Hg) cycle of terrestrial ecosystems. The foliage/atmosphere fluxes of Hg0 were observed over four seasons in a Masson pine (Pinus massoniana) forest in south China. Hg0 exchange showed a bidirectional process but without clear compensation point. Hg0 emissions peaked midday in all four seasons, probably associated with Hg photoreduction on needle surface. Peaks in Hg0 adsorption/deposition often occurred in the morning, especially in spring and autumn. Although current-year needles accumulated Hg at a rate of 19.4 µg m−2 yr−1, they were a net Hg0 source of 1.7 µg m−2 yr−1 to the atmosphere as their release of Hg exceeded inputs. In addition, previous-year needles emitted Hg0 at an average rate of 9.2 µg m−2 yr−1. Based on the mass balance of Hg in the forest canopy, the dry deposition of Hg was estimated 52.5 µg m−2 yr−1, much higher than the wet deposition (to 14.4 µg m−2 yr−1). Although Hg in the atmosphere is considered the main source of Hg in folia, soil water may contribute to Hg0 emission by plant transpiration. These processes should be further studied in the future.
- Published
- 2016
5. Inhibition of mercury release from forest soil by high atmospheric deposition of Ca2+ and SO42
- Author
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Lei Duan, Guangyi Xu, Yao Luo, and Jiming Hao
- Subjects
Environmental Engineering ,Gypsum ,Pinus massoniana ,biology ,Chemistry ,Health, Toxicology and Mutagenesis ,Public Health, Environmental and Occupational Health ,chemistry.chemical_element ,General Medicine ,General Chemistry ,engineering.material ,Particulates ,biology.organism_classification ,complex mixtures ,Pollution ,Flue-gas desulfurization ,Mercury (element) ,chemistry.chemical_compound ,Deposition (aerosol physics) ,Environmental chemistry ,Soil water ,engineering ,Environmental Chemistry ,Sulfur dioxide - Abstract
As one of the most important natural mercury (Hg) sources, soil release (emission to the atmosphere or leaching to soil water) depends on various factors, some of which can be affected by atmospheric deposition. We studied the effect of flue gas desulfurization gypsum (FGDG) addition on soil Hg release in a Masson pine (Pinus massoniana) forest in southwestern China. FGDG addition simulated atmospheric deposition of Ca2+, SO42- and Hg, which are commonly high in China. Results showed that Hg concentration in soil water decreased with the gypsum treatment, suggesting that the mobility of Hg in mineral soil was reduced. Moreover, the application of gypsum also seems to have decreased Hg emission from the soil, shown by the lower Hg contents in leaf tissues of ground vegetation in the treated plots than in the reference. Both Hg mobility in the soil and Hg emission to the atmosphere were decreased despite the additional Hg input from FGDG. The decreased DOC concentration in soil water and the elevated organic sulfur content in the soil Oe & Oa horizons were speculated to result in an enhanced capacity of surface soil to bind Hg, and thus to reduce Hg release from the soil. However, with the increasingly stringent control of particulate matter (PM) and sulfur dioxide (SO2) emissions in China, the deposition of Ca2+ and SO42- is expected to decrease, and their ability to inhibit soil Hg release is likely to decline in the future.
- Published
- 2015
6. Mercury concentrations in forest soils and stream waters in northeast and south China
- Author
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Long Wang, Shuxiao Wang, Guangyi Xu, Yao Luo, Lei Duan, and Jiming Hao
- Subjects
China ,Environmental Engineering ,Soil test ,chemistry.chemical_element ,Mercury ,STREAMS ,Forests ,Spatial distribution ,Pollution ,Mercury (element) ,Soil ,Deposition (aerosol physics) ,Rivers ,chemistry ,Environmental chemistry ,Soil water ,Dissolved organic carbon ,Forest ecology ,Soil Pollutants ,Environmental Chemistry ,Environmental science ,Waste Management and Disposal ,Water Pollutants, Chemical ,Environmental Monitoring - Abstract
Atmospheric deposition of mercury (Hg) is generally higher in China than in North America and Europe. Transport and methylation of Hg deposited in forest ecosystems may cause health risks to humans. We collected water samples from 117 small streams, and soil samples from 25 sites in forested areas in northeast and south China during 2011–2013 to investigate the spatial distribution of Hg. Results showed that Hg concentration in surface soil (0–5 cm in depth) was generally higher in south China (97.8 ± 36.0 μg/kg) than that in the northeast (44.0 ± 14.1 μg/kg). In contrast, the Hg concentration in stream water was higher in northeast China (17.2 ± 11.0 ng/L) than that in the south (6.2 ± 6.4 ng/L). Hg concentrations in surface soil were positively correlated with Hg concentrations in the overlying litter Oe/Oa horizon ( r 2 = 0.84). Hg concentrations in stream water were positively correlated to DOC (dissolved organic carbon) concentrations ( r 2 = 0.43) and to the Hg concentration in the litter Oe/Oa horizon ( r 2 = 0.69). Because the litter Oe/Oa horizon represents Hg accumulated by foliage, the positive correlations indicate that atmospheric Hg deposition was an important factor affecting Hg concentrations in soils and stream water.
- Published
- 2014
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