Comparison of inorganic chemical compositions of atmospheric TSP,PM10 and PM2.5 in northern and southern Chinese coastal cities

To compare the inorganic chemical compositions of TSP（total suspended paniculate）,PM10（particulate matter with an aerodynamic diameter less than 10 μm） and PM2.5（particulate matter with an aerodynamic diameter less than 2.5 μm） in southern and northern cities in China,atmospheric particles were synchronously collected in Dalian（the northern city）and Xiamen（the southern city） in spring and autumn of 2004.The mass concentrations,twenty-three elements and nine soluble ions were assessed.The results show that in Dalian,the mass concentrations of Mg,Al,Ca,Mn and Fe in spring were 4.0-10.1,2.6-8.0,4.1-12,1.2-3.6 and 2.9-7.9 times higher,respectively,than those in Xiamen.The dust storm influence is more obvious in Dalian in spring.However,in Xiamen,heavy metals accounted for 13.9%-17.9%of TSP,while heavy metals contributed to 5.5%-9.3%of TSP in Dalian.These concentrations suggest that heavy metal pollution in Xiamen was more serious.In addition,the concentrations of Na＋,Cl-,Ca2＋ and Mg2＋ were higher in Dalian due to the influence of marine aerosol,construction activities and soil dust.The NO3-/SO42- ratios in Dalian（0.25-0.49） were lower than those in Xiamen（0.51-0.62）,indicating that the contributions of vehicle emission to particles in Xiamen were higher.Coefficient of divergence values was higher than 0.40,implying that the inorganic chemical composition profiles for the particles of Dalian and Xiamen were quite different from each other.

Fast screening compositions of PM2.5 by ATR-FTIR： Comparison with results from IC and OC/EC analyzers

Chemical speciation of fine particles or PM2.5 collected on filters is still a cosily and time- consuming task. In this study, filter-based PM2.5 samples were collected during November-December 2013 at four sites in Guangzhou, and the major components were fast screened （~ 7 rain per filter sample） by Attenuated Total Reflectance （ATR）-Fourier Transform Infrared Spectroscopic （FTIR） in comparison with that measured by Organic carbon/Element carbon （OC/ EC） analyzer and Ion Chromatography （IC）. The concentrations of nitrate, ammonium, sulfate, primary organic carbon （POC） and secondary organic carbon （SOC） measured by OC/EC and IC analyzers were better correlated with their infrared absorption peak heights at 1320 cm 1 for nitrate, 1435, 3045 and 3215 cm^-1 for ammonium, 615 cm^-1 for sulfate, 690, 760 and 890 cm^-1 for POC and 1640 and 1660 cm^-1 for SOC respectively, during polluted days （PM2.5 〉 75 μg/m^3） than during clean days （PM2.5〈 75 μg/m^3）. With the evolution of a haze episode during our field campaign, the concentrations of the major PM2.5 components displayed consistent variations with their infrared absorption peak heights, suggesting ATR-FTIR could be a fast and useful technique to characterize filter-based PM2.5 compositions particularly during pollution events although cautions should be taken when PM2.5 levels are low. Notably, elevated PM2.5 mass concentrations occurred with enhanced ratios of [NO^-3][SO^2-4] and [NH^＋4]/[SO^2-4], implying that nitrogenous components play vital roles in the PM2.5 pollution events in the study region.

Nanoparticle-free and self-healing amphiphobic membrane for anti-surfactant-wetting membrane distillation

In membrane distillation(MD),complicated feed water with amphiphilic contaminants induces fouling/wetting of the MD membrane and can even lead to process failure.This study reports a facile approach to fabricate robust and self-healing hybrid amphiphobic membranes for anti-surfactant-wetting MD based on the ultra-low surface energy of fluorinated polyhedral oligomeric silsesquioxanes(F-POSS)and its thermal induced motivation and rotation.The thermal treatment makes the membranes achieving amphiphobicity at a very low cost of F-POSS(13.04 wt.%),which is about 1/3 of without thermal treatment.The prepared membrane exhibits excellent amphiphobicity,i.e.ethanol contact angle of 120.3°,without using environmentally toxic fluorinated nanoparticles.Robust MD performance was observed for the amphiphobic membrane in concentrated sodium dodecyl sulfate(SDS)feed solutions.Furthermore,the fabricated membrane exhibited stable amphiphobicity even in extreme environments,including strong acid or alkaline solutions.In the event of a damaged or abraded membrane surface where the F-POSS can be removed,the amphiphobic membrane exhibits self-healing ability with additional thermal treatment.This simple approach without the use of nanoparticles provides an environmentally friendly way for fabrication of amphiphobic membranes for anti-surfactant-wetting membrane distillation.

Annual nonmethane hydrocarbon trends in Beijing from 2000 to 2019

High loads of ground-level ozone have occurred with the implementation of the Air Pollution Prevention and Control Action Plan.However,the long temporal variation in precursor nonmethane hydrocarbons(NMHCs)has rarely been studied.In this study,we examined the evolution of NMHCs in Beijing based on ambient measurements from 2000 to 2019.The results indicated that the annual variation of ambient NMHCs during 2000 and 2019 could be divided into two stages.The mixing ratios of NMHCs rapidly rose during 2000 and 2009(1.76 ppbv/year)but exhibited a downward trend from 2009 to 2019 at rate of 0.80 ppbv/yr.Moreover,the notable decrease in alkenes and aromatics after 2009 led to a sharp decrease in the propylene-equivalent concentration(PEC)(-0.80 ppbv/year).Implementation of emission reduction measures in Beijing have effectively reduced the contribution of vehicle-related sources,but the contribution of solvent usage and fuel consumption increased,which will become the focus of VOC control in Beijing in the future.

Non-Gaussian ocean ambient noise model with certain kurtosis

Based on sampling damped sinusoids uniformly,a non-Gaussian ocean ambient noise sequence with specific spectral characteristics and a specific kurtosis value is generated for the non-Gaussian ocean ambient noise simulation problem.Under the theoretical simulation conditions,it is found that when the kurtosis value is higher than 3.0 better simulation results can be obtained.But when the kurtosis value is less than 3.0,a method of down sampling or reducing the filter order should be adopted for the simulation implementation.A simulation analysis of ambient noise data from four ocean acoustic environments is given,including quiet environment noise data,ship noise data,air gun data and impulse like data,and the results show that under the above scenarios,the non-Gaussian ocean ambient noise with the goal spectrum characteristics as well as statistical characteristics can be produced,and the kurtosis value simulation error is less than 2.4%.