Atmospheric particle-bound mercury in the northern Indo-Gangetic Plain region:Insights into sources from mercury isotope analysis and influencing factors

Lumbini is a world heritage site located in the southern plains region of Nepal, and is regarded as a potential site for evaluating transboundary air pollution due to its proximity to the border with India. In this study, 82 aerosol samples were collected between April 2013 and July 2014 to investigate the levels of particulate-bound mercury(PBM) and the corresponding seasonality, sources, and influencing factors.The PBM concentration in total suspended particulate(TSP) matter ranged from 6.8 pg m^(-3) to351.7 pg m^(-3)(mean of 99.7 ± 92.6 pg m^(-3)), which exceeded the ranges reported for remote and rural sites worldwide. The Hg content(PBM/TSP) ranged from 68.2 ng g^(-1) to 1744.8 ng g^(-1)(mean of 446.9 ±312.7 ng g^(-1)), indicating anthropogenic enrichment. The PBM levels were higher in the dry season(i.e.,winter and the pre-monsoon period) than in the wet season(i.e., the monsoon period). In addition, the δ^(202) Hg signature indicated that waste/coal burning and traffic were the major sources of Hg in Lumbini during the pre-monsoon period. Meanwhile, precipitation occurring during photochemical processes in the atmosphere may have been responsible for the observed Δ^(199) Hg values in the aerosol samples obtained during the monsoon period. The PBM concentration was influenced mostly by the resuspension of polluted dust during dry periods and crop residue burning during the post-monsoon period. The estimated PBM deposition flux at Lumbini was 15.7 lg m^(-2) yr^(-1). This study provides a reference dataset of atmospheric PBM over a year, which can be useful for understanding the geochemical cycling of Hg in this region of limited data.

N-糖链加工影响里氏木霉形态发生并提高木质纤维素降解能力

【背景】烟曲霉α-1,2-甘露糖苷酶Msd S在高尔基体中将N-糖链Man_(8)Glc NAc_(2)加工为成熟分泌糖蛋白的糖型Man_(6)Glc NAc_(2),有研究表明Msd S与烟曲霉的形态发生、细胞壁合成及蛋白质分泌密切相关;与烟曲霉不同的是,里氏木霉的成熟分泌糖蛋白上的N-糖链结构为Man_(8)Glc NAc_(2),细胞却能正常生长,说明丝状真菌N-糖链的加工具有物种特异性,但其生物学意义不明。【目的】为研究N-糖链加工对里氏木霉细胞生长及蛋白质分泌的影响,本研究将烟曲霉Msd S转入里氏木霉中以改变其成熟分泌糖蛋白的糖型。【方法】构建带有烟曲霉msd S基因的重组质粒并转入里氏木霉中,获得msd S表达菌株Tr-Msd S,分析Tr-Msd S菌株的生长表型、N-糖组、蛋白质分泌途径和纤维素酶活性的变化。【结果】在里氏木霉msd S表达菌株Tr-Msd S中,分泌糖蛋白的主要糖型由出发株的Man_(8)Glc NAc_(2)转变为Man_(6)Glc NAc_(2),细胞壁组分发生变化,但细胞壁完整性未受影响;与出发株相比,Tr-Msd S菌株产孢、出芽及分枝增多;另外,Msd S的表达还影响蛋白质分泌,在50°C时降解纤维素和β-葡聚糖的能力分别提高9.9%和32.2%。【结论】研究结果表明,N-糖链的加工可影响里氏木霉蛋白质,尤其是纤维素酶的分泌,干扰N-糖链加工可能是提高里氏木酶纤维素酶产量的新策略。

Atmospheric particle-bound polycyclic aromatic compounds over two distinct sites in Pakistan:Characteristics,sources and health risk assessment

Much attention is drawn to polycyclic aromatic hydrocarbons(PAHs)as an air pollutant due to their toxic,mutagenic and carcinogenic properties.Therefore,to understand the levels,seasonality,sources and potential health risk of PAHs in two distinct geographical locations at Karachi and Mardan in Pakistan,total suspended particle(TSP)samples were collected for over one year period.The average total PAH concentrations were 31.5±24.4 and 199±229 ng/m^(3) in Karachi and Mardan,respectively.The significantly lower concentration in Karachi was attributed to diffusion and dilution of the PAHs by the influence of clean air mass from the Arabian sea and high temperature,enhancing the volatilization of the particle phase PAHs to the gas phase.Conversely,the higher concentration(^(-)6 times)in Mardan was due to large influence from local and regional emission sources.A clear seasonality was observed at both the sites,with the higher values in winter and post-monsoon due to higher emissions and less scavenging,and lower values during monsoon season due to the dilution effect.Diagnostic ratios and principal component analysis indicated that PAHs in both sites originated from traffic and mixed combustion sources(fossil fuels and biomass).The average total Ba P equivalent concentrations(Ba P eq)in Karachi and Mardan were 3.26 and 34 ng/m^(3),respectively,which were much higher than the WHO guideline of 1 ng/m^(3).The average estimates of incremental lifetime cancer risk from exposure to airborne Ba P eq via inhalation indicated a risk to human health from atmospheric PAHs at both sites.

Distribution and transportation of mercury from glacier to lake in the Qiangyong Glacier Basin, southern Tibetan Plateau, China

The Tibetan Plateau is home to the largest aggregate of glaciers outside the Polar Regions and is a source of fresh water to 1.4 billion people. Yet little is known about the transportation and cycling of Hg in high-elevation glacier basins on Tibetan Plateau. In this study, surface snow,glacier melting stream water and lake water samples were collected from the Qiangyong Glacier Basin. The spatiotemporal distribution and transportation of Hg from glacier to lake were investigated. Significant diurnal variations of dissolved Hg（DHg） concentrations were observed in the river water, with low concentrations in the morning（8：00 am–14：00 pm） and high concentrations in the afternoon（16：00 pm–20：00 pm）. The DHg concentrations were exponentially correlated with runoff, which indicated that runoff was the dominant factor affecting DHg concentrations in the river water. Moreover, significant decreases of Hg were observed during transportation from glacier to lake. DHg adsorption onto particulates followed by the sedimentation of particulate-bound Hg（PHg） could be possible as an important Hg removal mechanism during the transportation process. Significant decreases in Hg concentrations were observed downstream of Xiao Qiangyong Lake, which indicated that the high-elevation lake system could significantly affect the distribution and transportation of Hg in the Qiangyong Glacier Basin.

Modification and coupled use of technologies are an essential envisioned need for bioaerosol study - An emerging public health concern

The airborne microbiome is one of the relevant topics in ecology,biogeochemistiy,environment,and human health.Bioaerosols are ubiquitous air pollutants that play a vital role in the linking of the ecosystem with the biosphere,atmosphere,climate,and public health.However,the sources,abundance,composition,properties,and atmospheric transport mechanisms of bioaerosols are not clearly understood.To screen the effects of climate change on aerosol microbial composition and its consequences for human health,it is first essential to develop standards that recognize the existing microbial components and how they vary naturally.Bioaerosol particles can be considered an information-rich unit comprising diverse cellular and protein materials emitted by humans,animals,and plants.Hence,no single standard technique can satisfactorily extract the required information about bioaerosols.To account for these issues,metagenomics,mass spectrometry,and biological and chemical analyses can be combined with climatic studies to understand the physical and biological relationships among bioaerosols.This can be achieved by strengthening interdisciplinary teamwork in biology,chemistry,earth science,and life sciences and by sharing knowledge and expertise globally.Thus,the coupled use of various advanced analytical approaches is the ultimate key to opening up the biological treasure that lies in the environment.

Concentration,sources and wet deposition of dissolved nitrogen and organic carbon in the Northern Indo-Gangetic Plain during monsoon

Precipitation represents an important phenomenon for carbon and nitrogen deposition.Here,the concentrations and fluxes of dissolved organic carbon(DOC)and total dissolved nitrogen(TDN)with their potential sources were analyzed in wet precipitation during summer monsoon from the Northern Indo-Gangetic Plain(IGP),important but neglected area.The volume-weighted mean(VWM)concentration of DOC and TDN were 687.04 and 1210.23μg/L,respectively.Similarly,the VWM concentration of major ions were in a sequence of NH_(4)^(+)>Ca^(2+)>SO_(4)^(2-)>Na^(+)>K^(+)>NO_(3)~->Cl~->Mg^(2+)>F~->NO_(2)~-,suggesting NH_(4)^(+)and Ca^(2+)from agricultural activities and crustal dust played a vital role in precipitation chemistry.Moreover,the wet deposition flux of DOC and TDN were 9.95 and 17.06 kg/(ha year),respectively.The wet deposition flux of inorganic nitrogen species such as NH_(4)^(+)-N and NO_(3)^(-)-N were 14.31 and 0.47 kg/(ha year),respectively,demonstrating the strong influence of emission sources and precipitation volume.Source attribution from different analysis suggested the influence of biomass burning on DOC and anthropogenic activities(agriculture,animal husbandry)on nitrogenous species.The air-mass back trajectory analysis indicated the influence of air masses originating from the Bay of Bengal,which possibly carried marine and anthropogenic pollutants along with the biomass burning emissions to the sampling site.This study bridges the data gap in the less studied part of the northern IGP region and provides new information for policy makers to deal with pollution control.

Nitrogenous and carbonaceous aerosols in PM_(2.5) and TSP during pre-monsoon:Characteristics and sources in the highly polluted mountain valley

This study reports for the first time a comprehensive analysis of nitrogenous and carbona-ceous aerosols in simultaneously collected PM_(2.5) and TSP during pre-monsoon(March-May 2018)from a highly polluted urban Kathmandu Valley(KV)of the Himalayan foothills.The mean mass concentration of PM_(2.5)(129.8 μg/m^(3))was only-25%of TSP mass(558.7 μg/m^(3))indicating the dominance of coarser mode aerosols.However,the mean concentration as well as fractional contributions of water-soluble total nitrogen(WSTN)and carbonaceous species reveal their predominance in find-mode aerosols.The mean mass concentration of WSTN was 17.43±4.70 μg/m^(3)(14%)in PM_(2.5) and 24.64±8.07 μg/m^(3)(5%)in TSP.Moreover,the fractional contribution of total carbonaceous aerosols(TCA)is much higher in PM_(2.5)(~34%)than that in TSP(~20%).The relatively low OC/EC ratio in PM_(2.5)(3.03±1.47)and TSP(4.64±1.73)suggests fossil fuel combustion as the major sources of carbonaceous aerosols with contributions from secondary organic aerosols.Five-day air mass back trajectories sim-ulated with the HYSPLIT model,together with MODIS fire counts indicate the influence of local emissions as well as transported pollutants from the Indo-Gangetic Plain region to the south of the Himalayan foothills.Principal component analysis(PCA)also suggests a mixed contribution from other local anthropogenic,biomass burning,and crustal sources.Our re-sults highlight that it is necessary to control local emissions as well as regional transport while designing mitigation measures to reduce the KV's air pollution.