An assessment of the atmospheric nitrogen budget on the South African Highveld
Atmospheric reactive nitrogen concentrations on the South African Highveld have become a growing concern, with satellite images indicating very high nitrogen dioxide (NO2) concentrations in the region. This study investigated the nitrogen budget on the Highveld through the analysis of the concentrat...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Academy of Science of South Africa
2010-06-01
|
| Series: | South African Journal of Science |
| Subjects: | |
| Online Access: | http://archive.sajs.co.za/index.php/SAJS/article/view/220 |
| _version_ | 1811220071492616192 |
|---|---|
| author | Kirsten S. Collett Stuart J. Piketh Kristy E. Ross |
| author_facet | Kirsten S. Collett Stuart J. Piketh Kristy E. Ross |
| author_sort | Kirsten S. Collett |
| collection | DOAJ |
| description | Atmospheric reactive nitrogen concentrations on the South African Highveld have become a growing concern, with satellite images indicating very high nitrogen dioxide (NO2) concentrations in the region. This study investigated the nitrogen budget on the Highveld through the analysis of the concentration of the atmospheric nitrogen species on a temporal scale as well as the atmospheric conversion, transport and removal of these species. Data were collected at Eskom’s Elandsfontein ambient air quality monitoring site, which is centrally located on the industrialised Highveld. A year’s dataset from 2005 and 2006 was analysed and it was found that nitrogen oxide (NOx) concentrations were higher in winter as a result of stable atmospheric conditions, as well as prevalent westerly and north-westerly airflow, which transported emissions directly from the nearby power station sources to the monitoring site. Nitrate (NO3) concentrations also peaked during winter, with a distinct biomass burning peak during August 2005. Diurnally, NOx concentrations indicated a tall-stack industrial source, where concentrations peaked at midday. The NO3 concentrations were higher at night than during the day; during the day the NO3 radical is rapidly photolysed and nitrates cannot be produced. Case studies indicated that the conversion rate of nitric oxide (NO) to NO2 was highly variable as a result of varying atmospheric factors, which include time of day, dispersion, stability and regional atmospheric chemistry. These rates ranged from 11% to 59% per hour. Rates of dry deposition of NO, NO2 and NO3 were generally higher during winter as a result of higher atmospheric concentrations and increased atmospheric stability. Nitrogen was predominantly deposited as NO2 throughout the year, except during spring when NO3 deposition dominated. The total annual amount of nitrogen that was deposited to the Mpumalanga Highveld region was in the range of 6.7 kg/ha –13.1 kg/ha per year, which is well below the stipulated critical load value. Such deposition, therefore, should not pose significant threats to the natural environment on the Highveld. Between 4% and 15% of the total emitted nitrogen from power generation on the Highveld was deposited to the surface via wet and dry deposition. The remainder was advected out of the region. |
| first_indexed | 2024-04-12T07:35:37Z |
| format | Article |
| id | doaj.art-41af9f1cf2bf4b7b8787f7261d190a6f |
| institution | Directory Open Access Journal |
| issn | 0038-2353 1996-7489 |
| language | English |
| last_indexed | 2024-04-12T07:35:37Z |
| publishDate | 2010-06-01 |
| publisher | Academy of Science of South Africa |
| record_format | Article |
| series | South African Journal of Science |
| spelling | doaj.art-41af9f1cf2bf4b7b8787f7261d190a6f2022-12-22T03:41:56ZengAcademy of Science of South AfricaSouth African Journal of Science0038-23531996-74892010-06-011065/610.4102/sajs.v106i5/6.220220An assessment of the atmospheric nitrogen budget on the South African HighveldKirsten S. Collett0Stuart J. Piketh1Kristy E. Ross2Climatology Research Group, University of the WitwatersrandClimatology Research Group, University of the WitwatersrandEskom Generation, Megawatt ParkAtmospheric reactive nitrogen concentrations on the South African Highveld have become a growing concern, with satellite images indicating very high nitrogen dioxide (NO2) concentrations in the region. This study investigated the nitrogen budget on the Highveld through the analysis of the concentration of the atmospheric nitrogen species on a temporal scale as well as the atmospheric conversion, transport and removal of these species. Data were collected at Eskom’s Elandsfontein ambient air quality monitoring site, which is centrally located on the industrialised Highveld. A year’s dataset from 2005 and 2006 was analysed and it was found that nitrogen oxide (NOx) concentrations were higher in winter as a result of stable atmospheric conditions, as well as prevalent westerly and north-westerly airflow, which transported emissions directly from the nearby power station sources to the monitoring site. Nitrate (NO3) concentrations also peaked during winter, with a distinct biomass burning peak during August 2005. Diurnally, NOx concentrations indicated a tall-stack industrial source, where concentrations peaked at midday. The NO3 concentrations were higher at night than during the day; during the day the NO3 radical is rapidly photolysed and nitrates cannot be produced. Case studies indicated that the conversion rate of nitric oxide (NO) to NO2 was highly variable as a result of varying atmospheric factors, which include time of day, dispersion, stability and regional atmospheric chemistry. These rates ranged from 11% to 59% per hour. Rates of dry deposition of NO, NO2 and NO3 were generally higher during winter as a result of higher atmospheric concentrations and increased atmospheric stability. Nitrogen was predominantly deposited as NO2 throughout the year, except during spring when NO3 deposition dominated. The total annual amount of nitrogen that was deposited to the Mpumalanga Highveld region was in the range of 6.7 kg/ha –13.1 kg/ha per year, which is well below the stipulated critical load value. Such deposition, therefore, should not pose significant threats to the natural environment on the Highveld. Between 4% and 15% of the total emitted nitrogen from power generation on the Highveld was deposited to the surface via wet and dry deposition. The remainder was advected out of the region.http://archive.sajs.co.za/index.php/SAJS/article/view/220atmospheric conversiondepositiondiurnal variationsnitratenitrogen oxidesseasonal variations |
| spellingShingle | Kirsten S. Collett Stuart J. Piketh Kristy E. Ross An assessment of the atmospheric nitrogen budget on the South African Highveld South African Journal of Science atmospheric conversion deposition diurnal variations nitrate nitrogen oxides seasonal variations |
| title | An assessment of the atmospheric nitrogen budget on the South African Highveld |
| title_full | An assessment of the atmospheric nitrogen budget on the South African Highveld |
| title_fullStr | An assessment of the atmospheric nitrogen budget on the South African Highveld |
| title_full_unstemmed | An assessment of the atmospheric nitrogen budget on the South African Highveld |
| title_short | An assessment of the atmospheric nitrogen budget on the South African Highveld |
| title_sort | assessment of the atmospheric nitrogen budget on the south african highveld |
| topic | atmospheric conversion deposition diurnal variations nitrate nitrogen oxides seasonal variations |
| url | http://archive.sajs.co.za/index.php/SAJS/article/view/220 |
| work_keys_str_mv | AT kirstenscollett anassessmentoftheatmosphericnitrogenbudgetonthesouthafricanhighveld AT stuartjpiketh anassessmentoftheatmosphericnitrogenbudgetonthesouthafricanhighveld AT kristyeross anassessmentoftheatmosphericnitrogenbudgetonthesouthafricanhighveld AT kirstenscollett assessmentoftheatmosphericnitrogenbudgetonthesouthafricanhighveld AT stuartjpiketh assessmentoftheatmosphericnitrogenbudgetonthesouthafricanhighveld AT kristyeross assessmentoftheatmosphericnitrogenbudgetonthesouthafricanhighveld |