scholarly journals Resolving Atmospheric Mercury Loading and Source Trends from Isotopic Records of Remote North American Lake Sediments

2020 ◽  
Vol 54 (15) ◽  
pp. 9325-9333 ◽  
Author(s):  
Ryan F. Lepak ◽  
Sarah E. Janssen ◽  
Daniel R. Engstrom ◽  
David P. Krabbenhoft ◽  
Michael T. Tate ◽  
...  
Keyword(s):  
Lake Sediments ◽  
North American ◽  
Atmospheric Mercury ◽  
Isotopic Records ◽  
Mercury Loading

scholarly journals Nested-grid simulation of mercury over North America

2012 ◽  
Vol 12 (14) ◽  
pp. 6095-6111 ◽  
Author(s):  
Y. Zhang ◽  
L. Jaeglé ◽  
A. van Donkelaar ◽  
R. V. Martin ◽  
C. D. Holmes ◽  
...  
Keyword(s):  
North America ◽  
North American ◽  
Wet Deposition ◽  
Atmospheric Mercury ◽  
Point Sources ◽  
Anthropogenic Emissions ◽  
Spatial And Temporal Variability ◽  
Nested Model ◽  
The Us ◽  
Nested Grid

Abstract. We have developed a new nested-grid mercury (Hg) simulation over North America with a 1/2° latitude by 2/3° longitude horizontal resolution employing the GEOS-Chem global chemical transport model. Emissions, chemistry, deposition, and meteorology are self-consistent between the global and nested domains. Compared to the global model (4° latitude by 5° longitude), the nested model shows improved skill at capturing the high spatial and temporal variability of Hg wet deposition over North America observed by the Mercury Deposition Network (MDN) in 2008–2009. The nested simulation resolves features such as higher deposition due to orographic precipitation, land/ocean contrast and and predicts more efficient convective rain scavenging of Hg over the southeast United States. However, the nested model overestimates Hg wet deposition over the Ohio River Valley region (ORV) by 27%. We modify anthropogenic emission speciation profiles in the US EPA National Emission Inventory (NEI) to account for the rapid in-plume reduction of reactive to elemental Hg (IPR simulation). This leads to a decrease in the model bias to −2.3% over the ORV region. Over the contiguous US, the correlation coefficient (r) between MDN observations and our IPR simulation increases from 0.60 to 0.78. The IPR nested simulation generally reproduces the seasonal cycle in surface concentrations of speciated Hg from the Atmospheric Mercury Network (AMNet) and Canadian Atmospheric Mercury Network (CAMNet). In the IPR simulation, annual mean gaseous and particulate-bound Hg(II) are within 140% and 11% of observations, respectively. In contrast, the simulation with unmodified anthropogenic Hg speciation profiles overestimates these observations by factors of 4 and 2 for gaseous and particulate-bound Hg(II), respectively. The nested model shows improved skill at capturing the horizontal variability of Hg observed over California during the ARCTAS aircraft campaign. The nested model suggests that North American anthropogenic emissions account for 10–22% of Hg wet deposition flux over the US, depending on the anthropogenic emissions speciation profile assumed. The modeled percent contribution can be as high as 60% near large point sources in ORV. Our results indicate that the North American anthropogenic contribution to dry deposition is 13–20%.

Atmospheric Mercury Depositional Chronology Reconstructed from Lake Sediments and Ice Core in the Himalayas and Tibetan Plateau

2016 ◽  
Vol 50 (6) ◽  
pp. 2859-2869 ◽  
Author(s):  
Shichang Kang ◽  
Jie Huang ◽  
Feiyue Wang ◽  
Qianggong Zhang ◽  
Yulan Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Lake Sediments ◽  
Ice Core ◽  
Atmospheric Mercury

A Holocene record of mercury accumulation in a pristine lake in Southernmost South America (53° S) – climatic and environmental drivers

2011 ◽  
Vol 8 (4) ◽  
pp. 6555-6588 ◽  
Author(s):  
Y.-M. Hermanns ◽  
H. Biester
Keyword(s):  
Lake Sediments ◽  
Environmental Changes ◽  
Atmospheric Mercury ◽  
Environmental Drivers ◽  
Mercury Accumulation ◽  
Natural Processes ◽  
Organic Complexes ◽  
Bedrock Weathering ◽  
Holocene Record

Abstract. Mercury accumulation in lake sediments has been extensively studied with regard to anthropogenic signals, but natural processes controlling mercury accumulation in the past and the influence of environmental and climatic changes are still poorly understood. In this study we present a 17 300 years old record of mercury accumulation in lake sediments in combination with a multi-proxy investigation of climatic and environmental changes in Southernmost Patagonia (53° S). Mercury accumulation in the remote pristine lake has been highly variable (up to a factor of 16), clearly exceeding the anthropogenic forcing of atmospheric mercury fluxes (factor of 3–5). Statistical data evaluation based on Principle Component Analysis reveals that the dominant driver of variations in mercury accumulation along with other organically bound elements (e.g. copper and yttrium) has been leaching of soluble organic complexes from catchment soils. This indicates that changes in precipitation rates and soils leaching are the most important climatic driver for short term variations in mercury in the lake's sediments. In the long term, however, mercury accumulation rates remain relatively constant (29 μg m−2 yr−1). This reflects that mercury accumulation in the catchment soils through atmospheric deposition and bedrock weathering has been fairly constant, too. As carbon storage in the soils and transport into the lake have increased, Hg/C ratios in the soil OM decreased. Fluxes of Hg into the lake are therefore mainly determined by the amount of OM leached into the lake and its Hg/C ratio.

Adaptation of the Connected Speech Test: Rerecording and Passage Equivalency

2020 ◽  
Vol 29 (2) ◽  
pp. 259-264 ◽  
Author(s):  
Hasan K. Saleh ◽  
Paula Folkeard ◽  
Ewan Macpherson ◽  
Susan Scollie
Keyword(s):  
Speech Perception ◽  
North American ◽  
First Language ◽  
Intraclass Correlation ◽  
Normal Hearing ◽  
Connected Speech ◽  
Internal Reliability ◽  
Speech Test ◽  
The Mean ◽  
Unit Standard

Purpose The original Connected Speech Test (CST; Cox et al., 1987) is a well-regarded and often utilized speech perception test. The aim of this study was to develop a new version of the CST using a neutral North American accent and to assess the use of this updated CST on participants with normal hearing. Method A female English speaker was recruited to read the original CST passages, which were recorded as the new CST stimuli. A study was designed to assess the newly recorded CST passages' equivalence and conduct normalization. The study included 19 Western University students (11 females and eight males) with normal hearing and with English as a first language. Results Raw scores for the 48 tested passages were converted to rationalized arcsine units, and average passage scores more than 1 rationalized arcsine unit standard deviation from the mean were excluded. The internal reliability of the 32 remaining passages was assessed, and the two-way random effects intraclass correlation was .944. Conclusion The aim of our study was to create new CST stimuli with a more general North American accent in order to minimize accent effects on the speech perception scores. The study resulted in 32 passages of equivalent difficulty for listeners with normal hearing.

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