Activity evolution of landslides and debris flows after the Wenchuan earthquake in the Qipan catchment,Southwest China

The Wenchuan earthquake that occurred on 12 May 2008 induced numerous landslides.Loose landslide materials were deposited on hillslopes,and deep channels were easily remobilized and transformed into debris flows by extreme rainstorms.Twelve years after the Wenchuan earthquake,debris flows were still active in the Qipangou Ravine in the quake-hit area.In this paper,we continuously tracked the spatiotemporal evolution of the landslides and vegetation restoration and evaluated the evolution of debris flow activity in the Qipan catchment with the aid of a GIS platform and field investigations from 2008 to 2019.We observed that the area with active landslides increased sharply immediately following the earthquake,and then decreased with time;however,the total area of landslides continued to increase from 6.93 km^(2)in 2008 to 10.55 km^(2)in 2019.The active landslides shifted towards lower angles and higher elevations after 2013.Since 2009,the vegetation coverage has been gradually increasing and approaching the coverage present before the earthquake as of 2019.The landslide activity was high and the vegetation recovery rates were rapidly rising during the first five years after the earthquake;the recovery rates then slowed over time.Therefore,we divided the evolution that occurred during the post landslide period into an active period(2008-2013),a self-adjustment period(2013-2026)and a stable period(after 2026).We then proposed a quantitative model to determine the trends of landslide activity rates and NDVI values in the catchment,which indicated that the landslide activities and postseismic vegetation restoration rates in this catchment will return to preseismic levels within approximately two decades.We also analysed the runout volumes of the debris flows after the earthquakes(Diexi and Wenchuan)and the standard deviation of the vegetation coverage and predicted that the debris flow activities will last for an additional 50 years or more.

Vertical Profiles of Volatile Organic Compounds in Suburban Shanghai

As Volatile Organic Compounds(VOCs)are one of the precursors of ozone,their distribution and variable concentrations are highly related to local ozone pollution control.In this study,we obtained vertical profiles of VOCs in Shanghai’s Jinshan district on 8 September and 9 September in 2016 to investigate their distribution and impact on local atmospheric oxidation in the near surface layer.Vertical samples were collected from heights between 50 m and 400 m by summa canisters using an unmanned aerial vehicle(UAV).Concentrations of VOCs(VOCs refers to the 52 species measured in this study)varied minimally below 200 m,and decreased by 21.2%from 100 m to 400 m.The concentrations of VOCs above 200 m decreased significantly in comparison to those below 200 m.The proportions of alkanes and aromatics increased from 55.2%and 30.5%to 57.3%and 33.0%,respectively.Additionally,the proportion of alkenes decreased from 13.2%to 8.4%.Toluene and m/p-xylene were the key species in the formation of SOA and ozone.Principal component analysis(PCA)revealed that the VOCs measured in this study mainly originated from industrial emissions.

Exhaust emission inventory of typical construction machinery and its contribution to atmospheric pollutants in Chengdu, China

To study the emission characteristics of typical construction machinery in Chengdu,12 construction machinery (excavators,bulldozers,loaders,and forklifts) under idling mode,moving mode,and working mode,were tested using a portable emission measurement system(PEMS).Under three operating modes,the typical construction machinery in the working mode was higher in the fuel-based average emission factors of PM_(2.5)and NOx,while the fuel-based average emission factors of HC and CO were higher in idling mode.Integrated the results of investigation on ownership and activity levels of construction machinery,an exhaust emission inventory of typical construction machinery of Chengdu in 2018 was established according to the recommendation method.The annual emission of PM_(2.5),NOx,HC,and CO were 1.67×106,1.61×108,3.83×106,and 1.26×107kg,respectively,and the excavator contributed the maximum emissions,accounting for an average proportion of 43.95%.The emission of construction machinery in Chengdu exhibited a clear monthly trend,with the highest from April to October and the lowest from November to March.In addition,the exhaust emissions presented an obvious spot-like characteristics,and the high-value areas were mainly concentrated in the surrounding suburban counties such as Shuangliu Wenjiang etc.To reduce pollution from construction machinery and improve the quality of the atmospheric environment,more effective measures on housing construction and municipal construction should be taken in those districts in Chengdu.

Building Resilience Through Disaster Waste Management——UN Environment's Experiences and Approaches

Integrating disaster waste issue is a critical component of making humanitarian action fit for the future,anticipating global risks and challenges such as increased vulnerability due to climate change and environmental degradation.This requires a fundamental shift towards a model that not only strengthens the response to crises but also learns and adapts in order to anticipate and act before such waste garnered.This article conducted analyses on the characteristics of disasters in the past two decades.Uncertainties confound disaster waste management,including the timing and magnitude of each disaster,and the amounts and types of waste that will be generated.For these reasons alone,disaster waste management must be an integral part of development planning and processes.Making 10 years since the 2008 Wenchuan earthquake,this article highlights that disaster waste management is not only debris clearance or waste management following a disaster,but also includes prevention and pre-disaster preparedness aspects in terms of enhancing resilience of local communities.Such"mainstreaming,"ensures that disaster waste management(DWM)will be treated as a priority issue,on an ongoing basis.Based on UN Environment's experiences and approaches,this paper emphasises that preparedness is the key,and that priority should be accorded to integrating disaster contingency planning in national and city level waste management strategies as well as mainstreaming waste management issues within broader disaster preparedness and response plans and actions.It is envisaged that the issues presented and the gaps identified in this paper will provide a basis for future comprehensive and cohesive research on disaster waste management.In turn,this research can lead to better preparedness and response on disaster waste management.

Investigating the spectral characteristic and humification degree of dissolved organic matter in saline-alkali soil using spectroscopic techniques

Soil samples were collected from the areas surrounding Wuliangsuhai Lake in China. Dissolved organic matter （DOM） was extracted from the samples and characterized by fluorescence and UV-Vis spectra. Spectral properties and humification degree of DOM were studied. The results indicated that both humic- and protein- like fluorophores were present in the DOM spectra, and the former was the dominant component. The analysis of humification （HIX） and r （A, C） indices revealed that the maximum humification degree in three agricultural soils （AAF, ASC, and ASW） was presented in the second soil layer （20-40 cm）. However, the humification degree of the two Halophytes soils （SSE and GKF） decreased with increasing depth. One index, I344/270, showed that humification degree increased gradually with an increasing proportion of humic-like acid. There was a significant positive correlation between humification degree （HIX） and aromaticity （SUVA254）, indicating that a higher aromaticity corresponded to a higher humification degree. Land use was an important factor responsible for the major difference of cation exchange capacity （CEC） in different soils, which led to a higher CEC value in the second soil layer for the three agricultural soils. CEC values and humification degree had the same trend for all five soils. The correlation analysis showed that there was a significant positive correlation between HIX and CEC,and a negative correlation between the r （A, C） index and CEC, indicating that humification degree increases gradually with increasing CEC values.

A preliminary analysis of the surface chemistry of atmospheric aerosol particles in a typical urban area of Beijing

Atmospheric aerosol particle samples were collected using an Ambient Eight Stage（Non-Viable） Cascade Impactor Sampler in a typical urban area of Beijing from 27 th Sep.to 5th Oct.,2009.The surface chemistry of these aerosol particles was analyzed using Static Time of Flight-Secondary Ion Mass Spectrometry（Static TOF-SIMS）.The factors influencing surface compositions were evaluated in conjunction with the air pollution levels,meteorological factors,and air mass transport for the sampling period.The results show that a variety of organic ion groups and inorganic ions/ion groups were accumulated on the surfaces of aerosol particles in urban areas of Beijing;and hydrophobic organic compounds with short-or middle-chain alkyl as well as hydrophilic secondary inorganic compounds were observed.All these compounds have the potential to affect the atmospheric behavior of urban aerosol particles.PM1.1–2.1and PM3.3–4.7had similar elements on their surfaces,but some molecules and ionic groups demonstrated differences in Time of Flight-Secondary Ion Mass Spectrometry spectra.This suggests that the quantities of elements varied between PM1.1–2.1and PM3.3–4.7.In particular,more intense research efforts into fluoride pollution are required,because the fluorides on aerosol surfaces have the potential to harm human health.The levels of air pollution had the most significant influence on the surface compositions of aerosol particles in our study.Hence,heavier air pollution was associated with more complex surface compositions on aerosol particles.In addition,wind,rainfall,and air masses from the south also greatly influenced the surface compositions of these urban aerosol particles.

Effective and selective electrocatalytic nitrate reduction to ammonia on urchin-like and defect-enriched titanium oxide microparticles

This work reported a facile approach to surface oxygen vacancy(O_(v))-enriched urchin-like TiO_(2) microparticles(U-TiO_(2)),which were highly effective and durable in catalyzing selective nitrate reduction to ammonia(NOgRR),Specifically,the U-TiO_(2)delivered a mass activity of 1.15 min^(-1)mg^(-1)calyst.a low yield of toxic NO_(2)^(-)-N intermediate(≤0.4mg/L)and an exceptional high NH_(3)^(-)-N selectivity of 98.1%in treating 22.5 mg/L of NO_(3)^(-)-N under a potential of-0.60V vs.RHE,outperforming most of the reported oxidebased catalysts.When comparing the performance of U-TiO_(2)with that of the solid amorphous TiO_(2) counterpart(A-TiO_(2))that had close particle size but more O_(v) on surfaces,we identified that the O_(v) was the reactive sites,but rather than its content,the NO_(3)RR kinetics were primarily limited by the electron and mass transfer at U-TiO_(2)/water interfaces.Accordingly,the superior performance of U-TiO_(2)to A-TiO_(2)could be ascribed to the hierarchical urchin-like structure in U-TiO_(2).The in-situ DEMS test revealed that the NO_(3)RR on U-TiO_(2)followed a pathway of ^(*)NO_(3)^(-)→^(*)NO_(2)^(-)→^(*)NO→^(*)N→^(*)NH^(-)→^(*)NH_(2)→^(*)NH_(3).We also demonstrated that the U-TiO_(2) could keep its robust performance under a wide NO_(3)^(-)-N concentration range and in the presence of some co-existing ions(such as Ca^(2+),Cl^(-),Mg^(2+)).However,the presence of humic acid and CO_(3)^(2-) in water slowed down the NO_(3)RR on U-TiO_(2).This work provides a more fundamental insight into the O_(v)-driven NO_(3)RR process on TiO_(2),which should benefit for the development of eficient TiO_(2)-based catalvsts.

Atmospheric carbonyls in a heavy ozone pollution episode at a metropolis in Southwest China:Characteristics,health risk assessment,sources analysis

Ambient carbonyls were continuously observed in the field during a heavy ozone pollution episode in Chengdu, China from August 4 to August 19, 2019, and the pollution characteristics, atmospheric photochemical reactivity, human health risk, and sources of carbonyls were analyzed. Fifteen carbonyls were quantified with average total mixing ratios of 20.38 ppbv Formaldehyde(9.86 ppbv), acetone(4.41 ppbv), and acetaldehyde(3.57 ppbv) were the three most abundant carbonyls. During the heavy ozone pollution episode, the concentration of carbonyls was found to be higher on pollution days than on the clean days, and relatively higher in the daytime, especially at noon on the pollution days. This was influenced by the intensity of photochemical reactions and precipitation. The “weekend effect” with the concentration of carbonyls was higher on the weekends than on the weekdays was pointed out. Formaldehyde, acetaldehyde and hexaldehyde were the dominant oxidative species during the observation. The carcinogenic and non-carcinogenic risk values of formaldehyde and acetaldehyde were higher on pollution days than on clean days, and these values were higher compared with those of other cities in China and abroad. Long-term exposure to these compounds should therefore be avoided. Diagnostic ratios and correlation analysis together with backward trajectory analysis showed that primary emission and secondary formation accounted 66%-76% and 24%–34% of carbonyls in Chengdu, respectively, with primary emission being the main sources of carbonyls, and carbonyls from the surrounding cities and emission from natural sources also had a significant contribution to the carbonyls in Chengdu.