ATMOSPHERIC DEPOSITION OF NITROGEN AND SULFUR

1. ATMOSPHERIC DEPOSITION OF NITROGEN AND SULFUR Kuliah Kimia Lingkungan Program Studi Kimia FMIPA ITB Keith, L. H., Energy and Environmental Acid Rain Chemistry, Volume 2, Ann Arbor Science Publisher, USA, 1982. Chapter 8, page 123 - 145

2. Atmospheric precipitation Atmospheric precipitation is comprised of: • Dry components: particulate and gases • Wet components: rain, snow, fog • Factors that affects chemical characteristic • of atmospheric precipitate: • Ocean salts • Gaseous air pollutants • Natural air-borne dust • Rainfall rate, frequency, • Soil particles and distribution

3. Learning Objectives Develop good understandings about: • What is acid rain • How it is formed • What problems might arise if acid rain occurs

4. Rain and acidity • Rain, in its theoretically normal, unpolluted state, is slightly acid, with pH 5.6, due to carbonic acid (H2CO3) which is a product of the dissolution of atmospheric carbon dioxide (CO2) • Acid rain is defined as rain with a pH<5.6

5. Rain and acidity • The oxides of sulfur and nitrogen (SOx and NOx) are oxidized in the atmosphere and form sulfuric and nitric acids (H2SO4 and HNO3) • These acids contribute to rain acidity • Sulfur compounds (and maybe also nitrogen compounds) can be transported several hundred kilometers per day in the atmosphere • Chlorine emission may also result in acidity (hydrochloric acid HCl), but usually only close to emission sources

7. Sources of S and N in atmosphere • Sulfur oxides are primarily emitted from stationary sources, such as utility and industrial coal-burning boilers • Nitrogen oxides are emitted from both stationary and mobile sources, especially automobiles

8. Sources of S and N in atmosphere Data from US EPA (1977): • ~56% of NOx was caused from the burning of fossil fuels by stationary sources • 40% came from transportation-related sources The combustion of fossil fuel in the US results in ~50 million metric tons of SOx and NOx being emitted to the atmosphere per year

9. In 1977: • SOx accounted for 14% (27.4 million metric tons) of the total air pollution • NOx accounted for 12% (13 million metric tons) of the total air pollution → result in acid rain, especially in northeastern US and Scandinavia

10. Ecological effects of acid rain • Degradation of water quality • Decrease in fish productivity • Decrease in forest productivity • Accelerated soil leaching

11. Ecological effects of acid rain Less concern about effect of acid rain is usually caused by: • data unavailability or only few data are available • about chemical characteristic of precipitation • environmental degradation caused by changes of precipitation chemistry • emission of SOx and NOx are thought as only causing less environmental effects

12. Research performed • Objectives: • to monitor both wet and dry components of atmospheric precipitation • to determine the geographical extent and temporal variation of acid rain in certain region • to anticipate some possible ecological effects of acid rain

13. Research performed • Sites to be analyzed? • Sampling methods? Time? • Chemical analysis? Methods and pollutants/compounds to be analyzed? • Ecological analysis? Type of indicators and organism to be investigated? • Statistical methods? • Possible interpretation?

14. The sites • The sites were chosen as a representative of geographical condition, vegetation, and land uses • The sites includes pollution source-areas, and potential receptor-areas where ecological effects may be important • The sites represent a small network, each site being close enough for interpretative purposes, e.g. to infer possible atmospheric transport between source sites and receptor sites

15. Sampling • Separate samples of wet and dry fallout were collected • A two-bucket system with movable lid were used, designed to expose the wet bucket and cover the dry bucket during periods of wet precipitation (and vice versa) • A sensor, mounted on the frame, reacts electrically to the onset of precipitation that causing the lid to move • This equipment (which has been modified to improved performances) is now used by the US National Atmospheric Deposition Program as a standard sampling system

16. Collector used for monitoring wet and dry atmospheric precipitation Sampling and subsequent chemical analysis were performed after each main storm event at the determined sites

17. Chemical analysis • pH of each samples were measured in the field with Corning Digital 112 Research meter, calibrated with buffer ph 4 – 7 • Samples were filtered through 0.45- Millipore prior to all analysis • Chemical digestion were done with boiling nitric acid and hydrogen peroxides • Cations were determined by atomic absorption spectrophotometry using Varian Model AA6

18. Chemical analysis • Chloride was determined using spectrophotometry • Sulfate was determined using barium chlorinated spectrophotometric method • Nitrate was determined by a hydrazine reduction • Ammonium was determined by indophenol • All data were analyzed using SPSS package program (Statistical Programs for Social Sciences)

19. Results and discussions • Acid rain is commonly occurred, pH = 3.71 – 5.20 • Several region closed to cement factory appeared to have relatively high pH values, pH = 6.40 – 6.73. This region is used as agricultural areas. Possibly due to upwind emission of alkaline particulates from the cement factory. • One particular site showed wide range of pH (from 3.71 – 6.29), illustrate the necessity for event monitoring (in contrast to weekly or monthly monitoring – for example), to provide data for interpretative purposes

20. Results and discussions • In some regions, there is a correlation between [H+] with [NO3─] • In one region [SO42─] > [NO3─] • In one other region, there is a correlation between [SO42─] and [H+], where correlation of [H+] and [NO3─] is not significant, suggested the occurrence of different acidity sources • Sulfuric acid in rain may be originated from air pollution from oil fields upwind, or the use of ammonium sulfate fertilizer in agricultural area

21. Results A strong correlation of[H+] with [NO3─] in one particular region

22. Results Ionic concentrations varied widely between storms at a given sites

23. Results and discussions • Fluctuation of [H+], [SO42─], and [NO3─] illustrate that it is difficult to generalize the infer effect from mean data alone • It is also difficult to generalize the relationship between storm frequency or storm volume to the corresponding ionic concentration • It is some evidence that pH of rain was higher 20 years ago

24. Results and discussions • Oceanic salts are carried out inland and deposited both as dry and wet precipitations • Sites which are closed to ocean, receive relatively large amounts of both wet and dry deposition of Na+ and Cl─ • Total ocean salt deposition is dependent upon total rain or snow on the site

27. Results and discussions • These functions are useful tools to predict the contribution of other ionic constituents of rain derived from oceanic sources • In oceanic water, ratio of [Cl─] : [Na+] = 1,17 • Using the Cl─ as a basis, and assuming that all [Cl─] is of oceanic origin, [Na+] can be calculated if [Cl─] is known

28. Results and discussions • Other salts concentration in rain water (such as Ca2+, Mg2+, SO42─, etc.) originated from oceanic water could also be predicted • If the concentration of these ions in rain water at any sites exceeds that of the predicted, than the excess can be reasonably assumed to be due to sources other that ocean

30. Results and discussions • Similar calculations of ion ratios relative to specific elements uniquely derived from known sources also allow the prediction of quantities of different elements • Silica may be a good indicator for soil derived air and rain pollutants • Lead may indicate pollutants from automobile exhaust emissions • These indicators have been extensively used in air pollution studies, but only very limited extent for on rain pollution studies

31. Results and discussions • Close attention should be given to total deposition values as well as concentration values to anticipate different types of ecological effects. For examples: • Plant or fish sensitivity to acidity may be determined by threshold pH • Accelerated soil leaching and rock weathering are more likely to be determined by increases in the total deposition of acidic materials