Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at the two European coastal monitoring stations Mace Head, Ireland, and Zingst, Germany

2005 ◽  
Vol 39 (39) ◽  
pp. 7549-7556 ◽  
Author(s):  
H KOCK ◽  
E BIEBER ◽  
R EBINGHAUS ◽  
T SPAIN ◽  
B THEES
Keyword(s):  
Seasonal Variations ◽  
Atmospheric Mercury ◽  
Coastal Monitoring ◽  
Long Term Trends ◽  
Monitoring Stations

Long-term trend analysis of deep-ocean acoustic noise data

2020 ◽  
Author(s):  
Sei-Him Cheong ◽  
Stephen P Robinson ◽  
Peter M Harris ◽  
Lian S Wang ◽  
Valerie Livina
Keyword(s):  
Trend Analysis ◽  
Sound Pressure ◽  
Functional Model ◽  
Deep Ocean ◽  
Ocean Noise ◽  
Noise Data ◽  
Long Term Trends ◽  
Long Term Trend ◽  
Monitoring Stations

<p>Underwater noise is recognised as a form of marine pollutant and there is evidence that over exposure to excessive levels of noise can have effects on the wellbeing of the marine ecosystem. Consequently, the variation in the ambient sound levels in the deep ocean has been the subject of a number of recent studies, with particular interest in the identification of long-term trends. We describe a statistical method for performing long-term trend analysis and uncertainty evaluation of the estimated trends from deep-ocean noise data. This study has been extended to include  measured data  from four monitoring stations located in the Indian (Cape Leeuwin & Diego Garcia), Pacific (Wake Island) and Southern Atlantic (Ascension Islands) Oceans over periods spanning between 8 to 15 years. The data were obtained from the hydro-acoustic monitoring stations of the Preparatory Commission for the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). The monitoring stations provide information at a sampling frequency of 250 Hz, leading to very large datasets, and at acoustic frequencies up to 105 Hz.</p><p>The analysis method uses a flexible discrete model that incorporates terms that capture seasonal variations in the data together with a moving-average statistical model to describe the serial correlation of residual deviations. The trend analysis is applied to time series representing daily aggregated statistical levels for four frequency bands to obtain estimates for the change in sound pressure level (SPL) over the examined period with associated coverage intervals. The analysis demonstrates that there are statistically significant changes in the levels of deep-ocean noise over periods exceeding a decade. The main features of the approach include (a) using a functional model  with terms  that represent both long-term and seasonal behaviour of deep-ocean noise, (b) using a statistical model to capture the serial correlation of the residual deviations that are not explained by the functional model, (c) using daily aggregation intervals derived from 1-minute  sound pressure level averages, and (d) applying a non-parametric approach to validate the uncertainties of the trend estimates that avoids the need to make an assumption about the distribution of the residual deviations.</p><p>The obtained results show the long term trends vary differently at the four stations. It was observed that low frequency noise generally dominated the significant trends in these oceans. The relative differences between the various statistical levels are remarkably similar for all the frequency bands. Given the complexity of the acoustic environment, it is difficult to identify the main causes of these trends. Some possible explanations for the observed trends are discussed. It was however observed some stations are subjected to strong seasonal variation with a high degree of correlation with climatic factors such as sea surface temperature, Antarctic ice coverage and wind speed. The same seasonal effects is less pronounced in station located closer to the equator.</p>

scholarly journals Ten-year trends of atmospheric mercury in the high Arctic compared to Canadian sub-Arctic and mid-latitude sites

2013 ◽  
Vol 13 (3) ◽  
pp. 1535-1545 ◽  
Author(s):  
A. S. Cole ◽  
A. Steffen ◽  
K. A. Pfaffhuber ◽  
T. Berg ◽  
M. Pilote ◽  
...  
Keyword(s):  
Continuous Monitoring ◽  
High Arctic ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Gaseous Mercury ◽  
Time Period ◽  
Long Term Trends ◽  
Arctic Atmosphere ◽  
Global Emissions

Abstract. Global emissions of mercury continue to change at the same time as the Arctic is experiencing ongoing climatic changes. Continuous monitoring of atmospheric mercury provides important information about long-term trends in the balance between transport, chemistry, and deposition of this pollutant in the Arctic atmosphere. Ten-year records of total gaseous mercury (TGM) from 2000 to 2009 were analyzed from two high Arctic sites at Alert (Nunavut, Canada) and Zeppelin Station (Svalbard, Norway); one sub-Arctic site at Kuujjuarapik (Nunavik, Québec, Canada); and three temperate Canadian sites at St. Anicet (Québec), Kejimkujik (Nova Scotia) and Egbert (Ontario). Five of the six sites examined showed a decreasing trend over this time period. Overall trend estimates at high latitude sites were: −0.9% yr−1 (95% confidence limits: −1.4, 0) at Alert and no trend (−0.5, +0.7) at Zeppelin Station. Faster decreases were observed at the remainder of the sites: −2.1% yr−1 (−3.1, −1.1) at Kuujjuarapik, −1.9% yr−1 (−2.1, −1.8) at St. Anicet, −1.6% yr−1 (−2.4, −1.0) at Kejimkujik and −2.2% yr−1 (−2.8, −1.7) at Egbert. Trends at the sub-Arctic and mid-latitude sites agree with reported decreases in background TGM concentration since 1996 at Mace Head, Ireland, and Cape Point, South Africa, but conflict with estimates showing an increase in global anthropogenic emissions over a similar period. Trends in TGM at the two high Arctic sites were not only less negative (or neutral) overall but much more variable by season. Possible reasons for differences in seasonal and overall trends at the Arctic sites compared to those at lower latitudes are discussed, as well as implications for the Arctic mercury cycle. The first calculations of multi-year trends in reactive gaseous mercury (RGM) and total particulate mercury (TPM) at Alert were also performed, indicating increases from 2002 to 2009 in both RGM and TPM in the spring when concentrations are highest.

scholarly journals <i>Letter to the Editor</i>: Spatial and seasonal variations of the <i>fo</i>F2 long-term trends

1999 ◽  
Vol 17 (9) ◽  
pp. 1239-1243 ◽  
Author(s):  
A. D. Danilov ◽  
A. V. Mikhailov
Keyword(s):  
Seasonal Variations ◽  
Critical Frequency ◽  
Geomagnetic Latitude ◽  
Seasonal Effect ◽  
Ionospheric Disturbances ◽  
Trend Magnitude ◽  
Letter To The Editor ◽  
Critical Frequency Fof2 ◽  
Long Term Trends

Abstract. Using a method suggested by the authors earlier, the long-term trends of the F2-layer critical frequency, foF2 are derived for a set of ionospheric stations with a wide latitudinal and longitudinal coverage. All the trends are found to be negative. A pronounced dependence on geomagnetic latitude is found, the trend magnitude increasing with the latter. No globe scale longitudinal effect in trends is detected. For the majority of the stations there is also a pronounced seasonal effect, the trend magnitude being higher in summer than in winter.Key words. Ionosphere (ionospheric disturbances; mid-latitude ionosphere)

scholarly journals Ten-year trends of atmospheric mercury in the high Arctic compared to Canadian sub-Arctic and mid-latitude sites

2012 ◽  
Vol 12 (8) ◽  
pp. 20209-20237 ◽  
Author(s):  
A. S. Cole ◽  
A. Steffen ◽  
K. Aspmo Pfaffhuber ◽  
T. Berg ◽  
M. Pilote ◽  
...  
Keyword(s):  
Continuous Monitoring ◽  
High Arctic ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Gaseous Mercury ◽  
Time Period ◽  
Long Term Trends ◽  
Arctic Atmosphere ◽  
Global Emissions

Abstract. Global emissions of mercury continue to change at the same time as the Arctic is experiencing ongoing climatic changes. Continuous monitoring of atmospheric mercury provides important information about long-term trends in the balance between transport, chemistry, and deposition of this pollutant in the Arctic atmosphere. Ten-year records of total gaseous mercury (TGM) were analyzed from two high Arctic sites at Alert (Nunavut, Canada) and Zeppelin Station (Svalbard, Norway); one sub-Arctic site at Kuujjuarapik (Nunavik, Québec, Canada); and three temperate Canadian sites at St. Anicet (Québec), Kejimkujik (Nova Scotia) and Egbert (Ontario). Five of the six sites examined show a decreasing trend over this time period. Overall trend estimates at high latitude sites were: −0.9% yr−1 (95% confidence limits: −1.4, 0) at Alert and no trend (−0.5, +0.7) at Zeppelin Station. Faster decreases were observed at the remainder of the sites: −2.1% yr−1 (−3.1, −1.1) at Kuujjuarapik, −1.9% yr−1 (−2.1, −1.8) at St. Anicet, −1.6% yr−1 (−2.4, −1.0) at Kejimkujik and −2.2% yr−1 (−2.8, −1.7) at Egbert. Trends at the sub-Arctic and mid-latitude sites agree with reported decreases in background TGM concentration since 1996 at Mace Head, Ireland, and Cape Point, South Africa, but conflict with estimates showing an increase in global anthropogenic emissions over a similar period. Trends in TGM at the two high Arctic sites were not only less negative (or neutral) overall but much more variable by season. Possible reasons for differences in seasonal and overall trends at the Arctic sites compared to those at lower latitudes are discussed, as well as implications for the Arctic mercury cycle. The first calculations of multi-year trends in reactive gaseous mercury (RGM) and total particulate mercury (TPM) at Alert were also performed, indicating increases from 2002 to 2009 in both RGM and TPM in the spring when concentrations are highest.

scholarly journals Long-term study of atmospheric mercury deposition at monitoring stations in Lithuania

2019 ◽  
Vol 59 (1) ◽  
Author(s):  
Jonas Šakalys ◽  
Kęstutis Kvietkus ◽  
Inga Garbarienė ◽  
Andriejus Urba
Keyword(s):  
Atmospheric Mercury ◽  
Mercury Vapour ◽  
Mercury Deposition ◽  
Bulk Precipitation ◽  
Term Study ◽  
Integrated Monitoring ◽  
Long Term Study ◽  
Mercury Analyzer ◽  
Monitoring Stations

The results of the long-term study of atmospheric mercury concentrations in the rain water carried out at the Aukštaitija and Žemaitija integrated monitoring stations are presented in this work. The bulk precipitation samples at both stations were collected every week during the 2007–2017 period. The mercury measurement method is based on the absorption of radiation by mercury vapour at the 253.7 nm line. The monthly samples of precipitation after preparation were analysed using a mercury analyzer ‘Gardis’ developed at our institution. The average annual concentrations, deposition amounts and trends of mercury in the precipitation over the period of 2007–2017 were analysed. The tendency of average monthly mercury concentrations in the precipitation at the Žemaitija station was continuously increasing before 2011, however, after 2012 it has a decreasing tendency which was contrary to that at the Aukštaitija station. At the same time, the tendencies of average monthly amounts of mercury deposited with precipitation showed decreasing amounts, especially at the Žemaitija station. Explanation of the above-mentioned phenomenon is complicated and the main reason is very changeable air mass trajectories and irregularity of precipitation.

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