scholarly journals New evidence for atmospheric mercury transformations in the marine boundary layer from stable mercury isotopes

2020 ◽  
Vol 20 (16) ◽  
pp. 9713-9723 ◽  
Author(s):  
Ben Yu ◽  
Lin Yang ◽  
Linlin Wang ◽  
Hongwei Liu ◽  
Cailing Xiao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Volume Effect ◽  
Atmospheric Mercury ◽  
Environmental Behaviors ◽  
Isotopic Compositions ◽  
Mass Independent Fractionation ◽  
Global Transport ◽  
New Evidence ◽  
Transformation Processes

Abstract. The marine boundary layer (MBL) is the largest transport place and reaction vessel of atmospheric mercury (Hg). The transformations of atmospheric Hg in the MBL are crucial for the global transport and deposition of Hg. Herein, Hg isotopic compositions of total gaseous mercury (TGM) and particle-bound Hg (PBM) collected during three cruises to Chinese seas in summer and winter were measured to reveal the transformation processes of atmospheric Hg in the MBL. Unlike the observation results at inland sites, isotopic compositions of TGM in the MBL were affected not only by mixing continental emissions but also largely by the oxidation of Hg0 primarily derived by Br atoms. Δ199Hg values of TGM were significantly positively correlated with air temperature in summer, indicating that processes inducing positive mass-independent fractionation of odd isotopes in TGM could be more active at low temperatures, while the relative processes might be weak in winter. In contrast, the positive Δ199Hg and high ratios of Δ199Hg∕Δ201Hg in PBM indicated that alternative oxidants other than Br or Cl atoms played a major role in the formation of Hg(II) in PBM, likely following the nuclear volume effect. Our results suggest the importance of local Hg environmental behaviors caused by an abundance of highly reactive species and provide new evidence for understanding the complicated transformations of atmospheric Hg in the MBL.

scholarly journals New evidence for atmospheric mercury transformations in the marine boundary layer

2020 ◽  
Author(s):  
Ben Yu ◽  
Lin Yang ◽  
Linlin Wang ◽  
Hongwei Liu ◽  
Cailing Xiao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Volume Effect ◽  
Atmospheric Mercury ◽  
Isotopic Signatures ◽  
Global Transport ◽  
New Evidence ◽  
Transformation Processes ◽  
Cl Atoms ◽  
Observation Results

Abstract. Marine boundary layer (MBL) is the largest transport place and reaction vessel of atmospheric mercury (Hg). The transformations of atmospheric Hg in MBL are crucial for the global transport and deposition of Hg. Herein, Hg isotopic signatures in total gaseous mercury (TGM) and particulate bound Hg (PBM) collected during three cruises to Chinese seas in summer and winter were measured to reveal the transformation processes of atmospheric Hg in the MBL. Unlike the observation results at inland sites, isotopic compositions in TGM from MBL were shaped not only by mixing continental emissions, but also largely by the oxidation of Hg0 primarily derived by Br atoms. Lower air temperature could promote the positive MIF in TGM in summer, while the relative processes might be weak in winter. In contrast, the positive Δ199Hg and high ratios of Δ199Hg / Δ201Hg in PBM indicated that alternative oxidants other than Br or Cl atoms played a major role in the formation of Hg(II) in PBM, likely following the nuclear volume effect. Our results suggested the importance of local Hg environmental behaviours caused by an abundance of highly reactive species, and provided new evidence for understanding the complicated transformations of atmospheric Hg in the MBL.

scholarly journals Experimental studies on particle emissions from cruising ship, their characteristic properties, transformation and atmospheric lifetime in the marine boundary layer

2007 ◽  
Vol 7 (5) ◽  
pp. 15105-15154 ◽  
Author(s):  
A. Petzold ◽  
J. Hasselbach ◽  
P. Lauer ◽  
R. Baumann ◽  
K. Franke ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Number ◽  
Marine Boundary Layer ◽  
Experimental Studies ◽  
Test Bed ◽  
Test Rig ◽  
Particle Emissions ◽  
Airborne Measurements ◽  
Emission Studies ◽  
Transformation Processes

Abstract. Particle emissions from ship engines and their atmospheric transformation in the marine boundary layer (MBL) were investigated in engine test bed studies and in airborne measurements of expanding ship plumes. During the test rig studies, detailed aerosol microphysical and chemical properties were measured in the exhaust gas of a serial MAN B{&amp;}W seven-cylinder four-stroke marine diesel engine under various load conditions. The emission studies were complemented by airborne aerosol transformation studies in the plume of a large container ship in the English Channel using the DLR aircraft Falcon 20 E-5. Observations from emission studies and plume studies combined with a Gaussian plume dispersion model yield a consistent picture of particle transformation processes from emission to atmospheric processing during plume expansion. Particulate matter emission indices obtained from plume measurements are 8.8±1.0×1015(kg fuel)−1 by number for non-volatile particles and 174±43 mg (kg fuel)−1 by mass for Black Carbon (BC). Values determined for test rig conditions between 85 and 110% engine load are of similar magnitude. For the total particle number including volatile compounds no emission index can be derived since the volatile aerosol fraction is subject to rapid transformation processes in the plume. Ship exhaust particles occur in the size range Dp<0.3 μm, showing a bi-modal structure. The combustion particle mode is centred at modal diameters of 0.05 μm for raw emissions to 0.10 μm at a plume age of 1 h. The smaller-sized volatile particle mode is centred at Dp≤0.02 μm. From the decay of ship exhaust particle number concentrations in an expanding plume, a maximum plume life time of approx. 24 h is estimated for a well-mixed marine boundary layer.

scholarly journals Current understanding of the driving mechanisms for spatiotemporal variations of atmospheric speciated mercury: a review

2016 ◽  
Vol 16 (20) ◽  
pp. 12897-12924 ◽  
Author(s):  
Huiting Mao ◽  
Irene Cheng ◽  
Leiming Zhang
Keyword(s):  
Boundary Layer ◽  
Seasonal Variations ◽  
Marine Boundary Layer ◽  
Temporal Variations ◽  
High Elevation ◽  
Atmospheric Mercury ◽  
Future Research ◽  
Spatiotemporal Variations ◽  
Driving Mechanisms ◽  
Diurnal Patterns

Abstract. Atmospheric mercury (Hg) is a global pollutant and thought to be the main source of mercury in oceanic and remote terrestrial systems, where it becomes methylated and bioavailable; hence, atmospheric mercury pollution has global consequences for both human and ecosystem health. Understanding of spatial and temporal variations of atmospheric speciated mercury can advance our knowledge of mercury cycling in various environments. This review summarized spatiotemporal variations of total gaseous mercury or gaseous elemental mercury (TGM/GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM) in various environments including oceans, continents, high elevation, the free troposphere, and low to high latitudes. In the marine boundary layer (MBL), the oxidation of GEM was generally thought to drive the diurnal and seasonal variations of TGM/GEM and GOM in most oceanic regions, leading to lower GEM and higher GOM from noon to afternoon and higher GEM during winter and higher GOM during spring–summer. At continental sites, the driving mechanisms of TGM/GEM diurnal patterns included surface and local emissions, boundary layer dynamics, GEM oxidation, and for high-elevation sites mountain–valley winds, while oxidation of GEM and entrainment of free tropospheric air appeared to control the diurnal patterns of GOM. No pronounced diurnal variation was found for Tekran measured PBM at MBL and continental sites. Seasonal variations in TGM/GEM at continental sites were attributed to increased winter combustion and summertime surface emissions, and monsoons in Asia, while those in GOM were controlled by GEM oxidation, free tropospheric transport, anthropogenic emissions, and wet deposition. Increased PBM at continental sites during winter was primarily due to local/regional coal and wood combustion emissions. Long-term TGM measurements from the MBL and continental sites indicated an overall declining trend. Limited measurements suggested TGM/GEM increasing from the Southern Hemisphere (SH) to the Northern Hemisphere (NH) due largely to the vast majority of mercury emissions in the NH, and the latitudinal gradient was insignificant in summer probably as a result of stronger meridional mixing. Aircraft measurements showed no significant vertical variation in GEM over the field campaign regions; however, depletion of GEM was observed in stratospherically influenced air masses. In examining the remaining questions and issues, recommendations for future research needs were provided, and among them is the most imminent need for GOM speciation measurements and fundamental understanding of multiphase redox kinetics.

scholarly journals Speciated atmospheric mercury in the marine boundary layer of the Bohai Sea and Yellow Sea

2016 ◽  
Vol 131 ◽  
pp. 360-370 ◽  
Author(s):  
Chunjie Wang ◽  
Zhijia Ci ◽  
Zhangwei Wang ◽  
Xiaoshan Zhang ◽  
Jia Guo
Keyword(s):  
Boundary Layer ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Marine Boundary Layer ◽  
Atmospheric Mercury ◽  
The Bohai Sea

scholarly journals Enhanced production of oxidised mercury over the tropical Pacific Ocean: a key missing oxidation pathway

2013 ◽  
Vol 13 (8) ◽  
pp. 21541-21572
Author(s):  
F. Wang ◽  
A. Saiz-Lopez ◽  
A. S. Mahajan ◽  
J. C. Gómez Martín ◽  
D. Armstrong ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Thermal Dissociation ◽  
Oxidation Mechanism ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Mercury Oxidation ◽  
Enhanced Production ◽  
Daily Variability

Abstract. Mercury is a contaminant of global concern. It is transported in the atmosphere primarily as gaseous elemental mercury, but its reactivity and deposition to the surface environment, through which it enters the aquatic food chain, is greatly enhanced following oxidation. Measurements of oxidised mercury in the polar to sub-tropical marine boundary layer have suggested that photolytically produced bromine atoms are the primary oxidant of mercury. We report year-round measurements of elemental and oxidised mercury, along with ozone, halogen oxides (IO and BrO) and nitrogen oxides (NO2), in the marine boundary layer over the Galápagos Islands in the Equatorial Pacific. Elemental mercury concentration remained low throughout the year, while considerable concentrations of oxidised mercury occurred around midday. Our results show that the production of oxidised mercury in the tropical marine boundary layer cannot be accounted for by only bromine oxidation, or by the inclusion of ozone and hydroxyl. A two-step oxidation mechanism where the HgBr intermediate is further oxidised to Hg(II) depends critically on the stability of HgBr. If the current paradigm is considered, another oxidant is needed to explain more than 50% of the observed oxidised mercury. We show that atomic iodine could play the role of the missing oxidant, explaining not only the Hg(II) levels observed, but also the daily variability. However, more recent theoretical calculations indicate that the thermal dissociation rate of HgBr is much faster, by an order of magnitude, than previously reported, which implies that only trace gases at relatively high mixing ratios forming stable complexes with HgBr (such as HO2 and NO2) could compete to generate levels of Hg(II) similar to those observed in our study. Nevertheless, the daily variability of oxidised mercury is not well accounted for by using these new theoretically estimated rates. Furthermore, correlation analysis does not support a major role of NO2 or HO2. We conclude that the key pathway that significantly enhances atmospheric mercury oxidation and deposition to the tropical oceans is missing from the current understanding of atmospheric mercury oxidation.

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