Batch experiments in the aerobic nutrient medium indicated that P.chrysosporium was involved in medium pH alteration and speciation of Cu at goethite surface. It was observed that pH alteration induced by P.chrysosporium was mineral dependant. The interaction between P.chrysosporium and goethite might shift the equilibrium to releasing more metal into the aqueous phase due to the decrease of pH in medium, sequestration of Cu by mycelium and formation of soluble organic Cu complex. The conversion of weakly bound Cu to aqueous Cu at the first 96 h of incubation was observed while strongly bound Cu remained nearly constant during the whole experimental period. The re-immobilization of Cu at 192 h was occurred in the presence of P.chrysosporium, which could be explained as being the result of both Cu precipitation with the increased pH and complexing of Cu by carboxyl, phenolic and carbonyl groups of the organic phase. In conclusion, P.chrysosporium-mineral interaction can play a key role in the cycling of trace elements in natural systems. A better understanding of fungal-mineral interactions is an urgent need to bioremediate the contaminated soil with fungi.
Abstract. Cyclones are expected to increase the vertical transport of sea spray aerosols (SSAs), which may significantly impact the climate by increasing the population of cloud condensation nuclei (CCN) and the cloud droplet number concentration (Nd). In this study, a high-time-resolution (1 h) aerosol monitoring was carried out in the middle and high Southern Hemisphere from 23 February to 4 March 2018. The characteristics of SSAs during three cyclones were observed during the cruise. The results showed that SSA level in the low atmosphere did not increase with the wind speed during cyclone processes, which was different from the anticipated scenario that SSA concentration would increase with wind speed. However, the size of SSA particles during cyclones was larger than that in the no-cyclone periods. It seems that the generation of SSAs was enhanced during cyclones, but SSA concentration near the sea surface increased scarcely. The upward-transport proportion was calculated according to the wind stress and sea salt flux between cyclone and non-cyclone periods. It indicated that more than 23.4 % of the SSAs were transported upwards by cyclone processes during event 1, and 36.2 % and 38.9 % were transported upwards in event 2 and event 3, respectively. The upward transport of SSAs was the main reason why SSA concentration did not increase in the low atmosphere. The transport of SSAs to the high atmosphere during cyclones may additionally increase the CCN burden in the marine boundary layer, which may affect the regional climate. This study highlights the importance of SSA transport to the high atmosphere by cyclones and extends the knowledge of SSA generation and the impact factor during the cyclone period in marine atmosphere.
Environmental context The ocean-produced dimethyl sulfide (DMS) molecule is thought to affect cloud formation and the solar radiation budget at the Earth’s surface, hence playing an important role in regulating climate. In this study, we calculated the DMS sea-to-air flux across the Southern Ocean, south-east Indian Ocean and north-west Pacific Ocean, and analysed the influence of DMS fluxes on sulfate aerosols. These results improved our understanding of the effects of DMS emissions on sulfate compounds in the atmosphere over the global ocean. Abstract Oceanic dimethyl sulfide (DMS) is the most abundant biogenic sulfur compound emitted into the atmosphere and could indirectly regulate the global climate by impacting end product sulfate aerosols. DMS emissions and their influence on sulfate aerosols, i.e. methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO42–), were investigated over the Atlantic Ocean and Indian Ocean sectors of the Southern Ocean (SO), the south-east Indian Ocean, and the north-west Pacific Ocean from February to April 2014 during the 30th Chinese National Antarctic Research Expedition. We found a strong large-scale DMS source in the marginal sea ice zone from 34 °W to 14 °E of the SO (south of 60 °S), in which the mean flux was 49.0 ± 65.6 μmol m−2 d−1 (0.6–308.3 μmol m−2 d−1, n = 424). We also found a second large-scale DMS source in the South Subtropical Front (~40 °S, up to 50.8 μmol m−2 d−1). An inconsistency between concentrations of atmospheric sulfate compounds and DMS emissions along the cruise track was observed. The horizontal advection of air masses was likely the main reason for this discrepancy. Finally, the biological exposure calculation results also indicated that it is very difficult to observe a straightforward relationship between oceanic biomass and atmospheric MSA.
Fe-loaded adsorbents have received increasing attention for the removal of arsenic in contaminated water or soil. In this study, Fe-loaded biochar was prepared from iron-impregnated corn straw under a pyrolysis temperature of 600°C. The ratio of crystalline Fe oxides including magnetite and natrojarosite to amorphous iron oxyhydroxide in the composite was approximately 2 : 3. Consisting of 24.17% Fe and 27.76% O, the composite exhibited a high adsorption capacity of 14.77 mg g −1 despite low surface areas (4.81 m 2 g −1 ). The pH range of 2.0–8.0 was optimal for arsenate removal and the adsorption process followed the Langmuir isotherms closely. In addition, pseudo-second-order kinetics best fit the As removal data. Fe oxide constituted a major As-adsorbing sink. Based on the X-ray diffraction spectra, saturation indices, and selective chemical extraction, the data suggested three main mechanisms for arsenate removal: sorption of arsenate, strong inner-sphere surface complexes with amorphous iron oxyhydroxide, and partial occlusion of arsenate into the crystalline Fe oxides or carbonized phase. The results indicated that the application of biochar prepared from iron-impregnated corn straw can be an efficient method for the remediation of arsenic contaminated water or soil.
Environmental context Water soluble ions (WSIs) in aerosols, especially in marine secondary aerosols, can participate in the formation of cloud condensation nuclei (CCN) in the marine boundary layer, which can affect global climate. In our study, in-situ gas and aerosol compositions were analysed to explore the formation paths and forms of secondary aerosols in the Southern Ocean (SO) in summer. Our study provided novel data on these formation mechanisms of secondary aerosols in the SO, with potential impacts on our understanding of global climate change. Abstract Water-soluble ions (WSIs) in aerosols, especially marine secondary aerosols, may participate in the formation of cloud condensation nuclei (CCN) in the marine boundary layer and affect the global climate. However, there is still a lack of studies on the background concentrations and the formation mechanisms of marine secondary aerosols in polar areas. High time resolution concentrations of WSIs in aerosols were analysed by an in situ gas and aerosol composition monitoring system in the Southern Ocean (SO) to identify the formation of marine secondary aerosols including methanesulfonic acid (MSA), SO42− and NO3−. The average hourly mass concentration of WSIs was 663 ng m−3 and secondary aerosols accounted for 49.8 ± 20.2 % of the WSIs. SO42− and NO3− were mainly formed by homogeneous reaction, whereas homogeneous and heterogeneous reactions together contributed to the formation of MSA− in aerosols in the SO. The melting of sea ice and the increase of chlorophyll-a (Chl-a) concentration contributed to the formation of MSA−. MSA-Na, MSA-NH4+, MSA-SO42−, MSA-Mg, MSA-K and MSA-Cl existed in marine aerosols. Secondary inorganic aerosols existed mainly in the forms of NH4NO3, (NH4)2SO4, Na2SO4 and MgSO4. The results enrich the data of WSI concentrations and formation mechanisms of secondary aerosols in the SO.
Marine aerosols were measured in real-time by an on-board signal particle aerosol mass spectrometer(SPAMS) over the Southeast China Sea. The chemical compositions and size distribution characteristics of aerosol particles were obtained, and the sources and ion spectra were analyzed. The results showed that particle number concentration decreased with the distance apart from the coastal area. In the coastal area, the aerosol compositions were mainly determined by the emissions of industry, such as vessel, traffic and coal combustion etc. When it was far from the continent, aerosols were mainly affected by the sea sources. Aerosol particles during the observation period disturbed singly with a peak diameter value of 0.5 μm. Most of the particles were in the size range of 0.2 μm to 0.8 μm. High signal intensity of EC with high K+ intensity in the positive spectrum and HSO4- intensity in negative spectrum was present in the marine aerosol over the coastal area. However, the signals of NO3- and NO2- were absent in the negative spectrum. The signal intensity of EC was weak in the marine aerosol over the sea area far from the coastal area. High signal intensity of Na+ and weak Mg+,Ca+ and NaCl+ signals were present in the positive spectrum, while high signal intensity of MSA-,CN-,O- and HSO4- were present in negative spectrum which was considered to be the special ions spectrum of marine biological sources. It indicated that ambient aerosols over the observation area were influenced not only by the anthropogenic emission sources but also affected by the marine aerosol formation.
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