Seasonal and diurnal variations of atmospheric mercury across the US determined from AMNet monitoring data

Abstract. Speciated atmospheric mercury observations collected over the period from 2008 to 2010 at the Environmental Protection Agency and National Atmospheric Deposition Program Atmospheric Mercury Network sites (AMNet) were analyzed for its spatial, seasonal, and diurnal characteristics across the US. Median values of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) at 11 different AMNet sites ranged from 148–226 ppqv (1.32–2.02 ng m−3), 0.05–1.4 ppqv (0.47–12.4 pg m−3) and 0.18–1.5 ppqv (1.61–13.7 pg m−3), respectively. Common characteristics of these sites were the similar median levels of GEM as well as its seasonality, with the highest mixing ratios occurring in winter and spring and the lowest in fall. However, discernible differences in monthly average GEM were as large as 30 ppqv, which may be caused by sporadic influence from local emission sources. The largest diurnal variation amplitude of GEM occurred in the summer. Seven rural sites displayed similar GEM summer diurnal patterns, in that the lowest levels appeared in the early morning, and then the GEM mixing ratio increased after sunrise and reached its maxima at noon or in the early afternoon. Unlike GEM, GOM exhibited higher mixing ratios in spring and summer. The largest diurnal variation amplitude of GOM occurred in spring for most AMNet sites. The GOM diurnal minima appeared before sunrise and maxima appeared in the afternoon. The increased GOM mixing ratio in the afternoon indicated a photochemically driven oxidation of GEM resulting in GOM formation. PBM exhibited diurnal fluctuations in summertime. The summertime PBM diurnal pattern displayed daily maxima in the early afternoon and lower mixing ratios at night, implying photochemical production of PBM in summer.

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Seasonal and diurnal variations of atmospheric mercury across the US determined from AMNet monitoring data

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-10845-2012 ◽

2012 ◽

Vol 12 (4) ◽

pp. 10845-10878

Author(s):

X. Lan ◽

R. Talbot ◽

M. Castro ◽

K. Perry ◽

W. Luke

Keyword(s):

Diurnal Variation ◽

Environmental Protection Agency ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Daily Maximum ◽

Mixing Ratio ◽

Mixing Ratios ◽

Early Afternoon ◽

Seasonal And Diurnal Variations ◽

The Us

Abstract. Speciated atmospheric mercury observations collected over the period from 2008 to 2010 at the Environmental Protection Agency and National Atmospheric Deposition Program Atmospheric Mercury Network sites (AMNet) were analyzed for its spatial, seasonal, and diurnal characteristics across the US Median values of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) at 11 different AMNet sites ranged from 148–226 ppqv (1.32–2.02 ng m−3), 0.05–1.4 ppqv (0.47–12.4 pg m−3) and 0.18–1.5 ppqv (1.61–13.7 pg m−3), respectively. Common characteristics of these sites were the similar median levels of GEM as well as its seasonality, with the highest mixing ratios occurring in winter and spring and the lowest in fall. However, discernible differences in monthly average GEM were as large as 30 ppqv, which may be caused by sporadic influence from local emission sources. The largest diurnal variation amplitude of GEM occurred in the summer. Seven rural sites displayed similar GEM summer diurnal patterns, in that the lowest levels appeared in the early morning, and then the GEM mixing ratio increased after sunrise and reached its maxima at noon or in the early afternoon. However, sites in Utah (UT96, UT97) and New York (NY95) showed a distinctly different pattern, with the lowest mixing ratios appearing in the afternoon and the highest mixing ratios at night. Unlike GEM, GOM exhibited higher mixing ratios in spring and summer. The largest diurnal variation amplitude of GOM occurred in spring for most AMNet sites. GOM diurnal minima appeared before sunrise and maxima appeared in the afternoon, and the variation in magnitude for all seasons at most monitoring sites fell in the range of 0 to 2 ppqv, except the Utah sites (up to 5 ppqv). The increased GOM mixing ratio in the afternoon indicated a photochemically driven oxidation of GEM resulting in GOM formation. PBM exhibited diurnal fluctuations in summertime instead of wintertime, although the PBM mixing ratio in summer was not as high as in winter. The summertime PBM diurnal pattern displayed a daily maximum in the early afternoon and lower mixing ratios at night, implying photochemical production of PBM in summer. The marine sea salt aerosol uptake of GEM and GOM was not apparent in the PBM data collected at coastal sites, with PBM being higher at inland sites.

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Comparison of Atmospheric Mercury Speciation at a Coastal and an Urban Site in Southeastern Texas, USA

Atmosphere ◽

10.3390/atmos11010073 ◽

2020 ◽

Vol 11 (1) ◽

pp. 73 ◽

Cited By ~ 3

Author(s):

Travis Griggs ◽

Lei Liu ◽

Robert W. Talbot ◽

Azucena Torres ◽

Xin Lan

Keyword(s):

Northern Hemisphere ◽

Background Level ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Urban Site ◽

Mercury Species ◽

Mixing Ratio ◽

Coastal Site ◽

Mixing Ratios ◽

The Relationship

Sixteen months of continuous measurements and the analysis of atmospheric mercury (gaseous elemental mercury GEM, gaseous oxidized mercury GOM, and particulate bound mercury PBM) under urban and coastal settings were conducted in Southeastern Texas. At the urban site, the GEM mean mixing ratio was 185 ppqv, 5%–10% higher than the Northern Hemisphere GEM background level. GOM and PBM mixing ratios were as much as six times higher than their background level. The coastal site GEM mean mixing ratio was 165 ppqv, higher than other coastal sites located in the Northern Hemisphere. GOM and PBM mean mixing ratios at the coastal site were 0.75 ppqv and 0.58 ppqv. The urban site had a higher frequency of high mercury events (>300 ppqv) compared to the coastal site. The diurnal patterns were found for both sites: In the urban environment, GEM accumulated to the maximum mixing ratio just after sunrise and decreased to the minimum mixing ratio in late afternoon. In the coastal environment, GEM decreased at night reaching its minimum mixing ratio before sunrise. The relationship between atmospheric mercury species and meteorological parameters was investigated. An examination of the relationship between atmospheric mercury species and key trace gases was conducted as well, showing that the concurrence of GEM, CO2, CO, CH4, and SO2 maximum mixing ratios was notable and provided evidence they may originate from the same emission source. The coastal site was at times influenced by polluted air from urban Houston and the cleaner Gulf of Mexico marine air at other times.

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Investigation of processes controlling GEM oxidation at mid-latitudinal marine, coastal, and inland sites

10.5194/acp-2015-829 ◽

2016 ◽

Author(s):

Z. Ye ◽

H. Mao ◽

C.-J. Lin ◽

S. Y. Kim

Keyword(s):

Marine Boundary Layer ◽

State Of The Art ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Chemical Mechanism ◽

Atmospheric Conditions ◽

Gaseous Elemental Mercury ◽

Mixing Ratios ◽

Marine Site ◽

Study Sites

Abstract. A box model incorporating a state-of-the-art chemical mechanism for atmospheric mercury (Hg) cycling was developed to investigate oxidation of gaseous elemental mercury (GEM) at three locations in the northeastern United States: Appledore Island (marine), Thompson Farm (coastal, rural), and Pack Monadnock (inland, rural, elevated). The chemical mechanism improved model's ability to simulate the formation of gaseous oxidized mercury (GOM) at the study sites. At the coastal and inland sites, GEM oxidation was predominated by O3 and OH, contributing 80–99 % of total GOM production during daytime. H2O2 initiated GEM oxidation was significant (~ 33 % of the total GOM) at the inland site during nighttime. In the marine boundary layer (MBL), Br and BrO were dominant GEM oxidants contributing ~ 70 % of the total GOM production during mid-day, while O3 dominated GEM oxidation (50–90 % of GOM production) over the remaining day. Following the production of HgBr from GEM + Br, HgBr was oxidized by BrO, HO2, OH, ClO, and IO to form Hg(II) brominated GOM species. However, under atmospheric conditions, the prevalent GEM oxidants in the MBL could be Br / BrO or O3 / OH depending on Br and BrO mixing ratios. Relative humidity and products of the CH3O2 + BrO reaction possibly affected significantly the mixing ratios of Br or BrO radicals and subsequently GOM formation. Gas-particle partitioning could be potentially important in the production of GOM as well as Br and BrO at the marine site.

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Investigation of processes controlling summertime gaseous elemental mercury oxidation at midlatitudinal marine, coastal, and inland sites

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-8461-2016 ◽

2016 ◽

Vol 16 (13) ◽

pp. 8461-8478 ◽

Cited By ~ 16

Author(s):

Zhuyun Ye ◽

Huiting Mao ◽

Che-Jen Lin ◽

Su Youn Kim

Keyword(s):

Marine Boundary Layer ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Box Model ◽

Chemical Mechanism ◽

Gaseous Elemental Mercury ◽

Diurnal Cycles ◽

Mixing Ratios ◽

Halogen Chemistry ◽

Marine Site

Abstract. A box model incorporating a state-of-the-art chemical mechanism for atmospheric mercury (Hg) cycling was developed to investigate the oxidation of gaseous elemental mercury (GEM) at three locations in the northeastern United States: Appledore Island (AI; marine), Thompson Farm (TF; coastal, rural), and Pack Monadnock (PM; inland, rural, elevated). The chemical mechanism in this box model included the most up-to-date Hg and halogen chemistry. As a result, the box model was able to simulate reasonably the observed diurnal cycles of gaseous oxidized mercury (GOM) and chemical speciation bearing distinct differences between the three sites. In agreement with observations, simulated GOM diurnal cycles at AI and TF showed significant daytime peaks in the afternoon and nighttime minimums compared to flat GOM diurnal cycles at PM. Moreover, significant differences in the magnitude of GOM diurnal amplitude (AI > TF > PM) were captured in modeled results. At the coastal and inland sites, GEM oxidation was predominated by O3 and OH, contributing 80–99 % of total GOM production during daytime. H2O2-initiated GEM oxidation was significant (∼ 33 % of the total GOM) at the inland site during nighttime. In the marine boundary layer (MBL) atmosphere, Br and BrO became dominant GEM oxidants, with mixing ratios reaching 0.1 and 1 pptv, respectively, and contributing ∼ 70 % of the total GOM production during midday, while O3 dominated GEM oxidation (50–90 % of GOM production) over the remaining day when Br and BrO mixing ratios were diminished. The majority of HgBr produced from GEM+Br was oxidized by NO2 and HO2 to form brominated GOM species. Relative humidity and products of the CH3O2+BrO reaction possibly significantly affected the mixing ratios of Br or BrO radicals and subsequently GOM formation. Gas–particle partitioning could potentially be important in the production of GOM as well as Br and BrO at the marine site.

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Seasonal and Diurnal Variations of Ozone near the Mesopause from Observations of the 11.072-GHz Line

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2009jtecha1291.1 ◽

2009 ◽

Vol 26 (10) ◽

pp. 2192-2199 ◽

Cited By ~ 6

Author(s):

A. E. E. Rogers ◽

M. Lekberg ◽

P. Pratap

Keyword(s):

Seasonal Variation ◽

Seasonal Variations ◽

Atomic Hydrogen ◽

Diurnal Variations ◽

Mixing Ratio ◽

Mesopause Region ◽

Mixing Ratios ◽

Rates Of Change ◽

Broadband Emission ◽

Seasonal And Diurnal Variations

Abstract Ground-based observations of the 11.072-GHz line of ozone were made from January 2008 through January 2009. These observations provide an estimate of the diurnal and seasonal variations of ozone in the mesopause region. The 11-GHz line is more sensitive to the ozone at higher altitudes than ground observations of the 142-GHz line, because of the reduced Doppler line width. The observations show an increase in the volume mixing ratio of ozone above 80 km at night by more than a factor of 10 and a seasonal variation of about a factor of 2, which is consistent with the semiannual variations of atomic hydrogen in the mesopause region. The diurnal amplitude and rates of change of the mixing ratios at sunrise and sunset are compared with ground-based observations of the 142-GHz line and the observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite, as well as with a simplified chemical model of the creation and destruction of ozone in the mesopause region.

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Temporal and diurnal variation in social media posts to a suicide support forum

BMC Psychiatry ◽

10.1186/s12888-021-03268-1 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Rina Dutta ◽

George Gkotsis ◽

Sumithra Velupillai ◽

Ioannis Bakolis ◽

Robert Stewart

Keyword(s):

At Risk ◽

Social Media ◽

Diurnal Variation ◽

Suicide Attempts ◽

Early Morning ◽

Time Of Day ◽

Diurnal Rhythms ◽

Similar Time ◽

Subsequent Decrease ◽

Early Afternoon

Abstract Background Rates of suicide attempts and deaths are highest on Mondays and these occur more frequently in the morning or early afternoon, suggesting weekly temporal and diurnal variation in suicidal behaviour. It is unknown whether there are similar time trends on social media, of posts relevant to suicide. We aimed to determine temporal and diurnal variation in posting patterns on the Reddit forum SuicideWatch, an online community for individuals who might be at risk of, or who know someone at risk of suicide. Methods We used time series analysis to compare date and time stamps of 90,518 SuicideWatch posts from 1st December 2008 to 31st August 2015 to (i) 6,616,431 posts on the most commonly subscribed general subreddit, AskReddit and (ii) 66,934 of these AskReddit posts, which were posted by the SuicideWatch authors. Results Mondays showed the highest proportion of posts on SuicideWatch. Clear diurnal variation was observed, with a peak in the early morning (2:00–5:00 h), and a subsequent decrease to a trough in late morning/early afternoon (11:00–14:00 h). Conversely, the highest volume of posts in the control data was between 20:00–23:00 h. Conclusions Posts on SuicideWatch occurred most frequently on Mondays: the day most associated with suicide risk. The early morning peak in SuicideWatch posts precedes the time of day during which suicide attempts and deaths most commonly occur. Further research of these weekly and diurnal rhythms should help target populations with support and suicide prevention interventions when needed most.

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Seasonal and diurnal variations of biogenic volatile organic compounds in highland and lowland ecosystems in southern Kenya

10.5194/acp-2021-445 ◽

2021 ◽

Author(s):

Yang Liu ◽

Simon Schallhart ◽

Ditte Taipale ◽

Toni Tykkä ◽

Matti Räsänen ◽

...

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Atmospheric Chemistry ◽

Daily Maximum ◽

Mixing Ratio ◽

Biogenic Volatile Organic Compounds ◽

Mixing Ratios ◽

Seasonal And Diurnal Variations ◽

Volatile Organic ◽

Dry Seasons

Abstract. The East African lowland and highland areas consist of water-limited and humid ecosystems. The magnitude and seasonality of biogenic volatile organic compounds (BVOCs) emissions from these functionally contrasting ecosystems are limited due to a scarcity of direct observations. We measured mixing ratios of BVOCs from two contrasting ecosystems, humid highlands with agroforestry and dry lowlands with bushland, grassland, and agriculture mosaics, during both the rainy and dry seasons of 2019 in southern Kenya. We present the diurnal and seasonal characteristics of BVOC mixing ratios and their reactivity, and estimated emission factors (EFs) for certain BVOCs from the African lowland ecosystem based on field measurements. The most abundant BVOCs were isoprene and monoterpenoids (MTs), with isoprene contributing > 70 % of the total BVOC mixing ratio during daytime, while MTs accounted for > 50 % of the total BVOC mixing ratio during nighttime at both sites. The contributions of BVOCs to the local atmospheric chemistry were estimated by calculating the reactivity towards the hydroxyl radical (OH), ozone (O3), and the nitrate radical (NO3). Isoprene and MTs contributed the most to the reactivity of OH and NO3, while sesquiterpenes dominated the contribution of organic compounds to the reactivity of O3. The mixing ratio of isoprene measured in this study was lower to that measured in the relevant ecosystems in west and south Africa, while that of monoterpenoids was similar. Isoprene mixing ratios peaked daily between 16:00 and 20:00 with a maximum mixing ratio of 809 parts per trillion by volume (pptv) and 156 pptv in the highlands, and 115 pptv and 25 pptv in the lowlands, during the rainy and dry seasons, respectively. MT mixing ratios reached their daily maximum between midnight and early morning (usually 04:00 to 08:00) with mixing ratios of 254 pptv and 56 pptv in the highlands, and 89 pptv and 7 pptv in the lowlands, in the rainy and dry seasons, respectively. The dominant species within the MT group were limonene, α-pinene, and β-pinene. EFs for isoprene, MTs, and 2-methyl-3-buten-2-ol (MBO) were estimated using an inverse modeling approach. The estimated EFs for isoprene and β-pinene agreed very well with what is currently assumed in the world’s most extensively used biogenic emissions model, the Model of Emissions of Gases and Aerosols from Nature (MEGAN), for warm C4 grass, but the estimated EFs for MBO, α-pinene, and especially limonene, were significantly higher than that assumed in MEGAN for the relevant plant functional type. Additionally, our results indicate that the EF for limonene might be seasonally dependent in savanna ecosystems.

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Corrigendum to: Atmospheric variation of nitrous acid at different sites in Europe

Environmental Chemistry ◽

10.1071/en07023_co ◽

2007 ◽

Vol 4 (5) ◽

pp. 364 ◽

Cited By ~ 3

Author(s):

Karin Acker ◽

Detlev Möller

Keyword(s):

Hydroxyl Radical ◽

Nitrous Acid ◽

Field Experiments ◽

Early Morning ◽

Mixing Ratio ◽

Gas Phase Reactions ◽

Sources And Sinks ◽

Mixing Ratios ◽

Secondary Pollutants ◽

Rural Sites

Environmental context. Nitrous acid (HNO2) is an important source of the hydroxyl radical (OH.), the most important daytime oxidising species that contributes to the formation of ozone as well as of other secondary pollutants in the troposphere. Understanding the sources and sinks of HNO2 is of crucial interest for accurately modelling the chemical composition of the troposphere and predicting future trace gas concentrations. Abstract. Nitrous acid and several other atmospheric components and variables were continuously measured during complex field experiments at seven different suburban and rural sites in Europe. HNO2 is mainly formed by heterogeneous processes and is often accumulated in the nighttime boundary layer. Our results confirm that the photolysis of HNO2 is an important source of the hydroxyl radical, not only in the early morning hours but also throughout the entire day, and is often comparable with the contribution of ozone and formaldehyde photolysis. At all research sites unexpectedly high HNO2 mixing ratios were observed during the daytime (up to several hundred ppt, or pmol mol-1). Moreover, surprisingly, the HNO2 mixing ratio at the three mountain sites often showed a broad maximum or several distinct peaks at midday and lower mixing ratios during the night. Assuming a quickly established photo-equilibrium between the known significant gas phase reactions, only a few ppt HNO2 should be present around noon. The ratio of known sources to sinks indicates a missing daytime HNO2 source of 160-2600 ppt h-1 to make up the balance. Based on these values and on production mechanisms proposed in the literature we hypothesise that the daytime mixing ratio levels may only be explained by a fast electron transfer onto adsorbed NO2.

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Long-Term Changes in Precipitation in Japan

Journal of Disaster Research ◽

10.20965/jdr.2008.p0051 ◽

2008 ◽

Vol 3 (1) ◽

pp. 51-60 ◽

Cited By ~ 6

Author(s):

Fumiaki Fujibe ◽

Keyword(s):

Diurnal Variation ◽

Present Article ◽

Daily Precipitation ◽

Early Morning ◽

Relative Increase ◽

Daily Data ◽

Early Afternoon ◽

Long Term Changes ◽

Precipitation Records

This paper explores features of long-term changes in precipitation in Japan based on recent studies using daily data from 51 stations since 1901, partly updated for the present article. We show that heavy daily precipitation (≧ 200 mm and ≧ 100 mm) has significantly increased during the last century as weak to moderate precipitation (≧ 1 mm to ≧ 10 mm) has decreased. New analysis using hourly precipitation records at over 600 stations on the AMeDAS network has shown an increase in very intense hourly and six-hourly precipitations (≧100 mm/h and ≧300 mm/6h) during the last 28 years. It also shows that the trend in the spatial concentration of precipitation during the last century has been increasing, as have changes in the pattern of diurnal variation of precipitation, characterized by a relative increase in precipitation amounts in early morning and a decrease in early afternoon.

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A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-2969-2012 ◽

2012 ◽

Vol 12 (6) ◽

pp. 2969-2985 ◽

Cited By ~ 21

Author(s):

D. Pino ◽

J. Vilà-Guerau de Arellano ◽

W. Peters ◽

J. Schröter ◽

C. C. van Heerwaarden ◽

...

Keyword(s):

Carbon Dioxide ◽

Boundary Layer ◽

Early Morning ◽

Mixing Ratio ◽

Layer Depth ◽

Free Atmosphere ◽

Convective Boundary ◽

Surface Exchange ◽

Mixing Ratios ◽

Boundary Layer Dynamics

Abstract. Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the mid-day CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we "invert" the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.

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