“Estimated total nitrogen deposition and rainwater composition measured in the Kruger National Park” March 2011 EH Conradie Ph.D student
Outline • Project motivation and objectives • Current measurements • Importance of nitrogen deposition • Results – Gaseous measurements (monthly) – Aerosols (monthly) – Rainwater analyses (monthly) – Total deposition (monthly) – Rainwater (annual) compared to other sites • Conclusions
Project motivation and objectives • KNP project title: “Long-term spatial and temporal deposition of biogeochemically important trace species over southern Africa (DEBITS)” • DEBITS began in 1990 – originally an IGAC task entitled “Composition and Acidity of Asian Precipitation” (CAAP) • Changed to DEBITS in 1994 when African (IDAF) and South American (LBA) networks joined the initiative • The program is driven by scientific questions related to global atmospheric chemistry • DEBITS SA was developed to monitor deposition and potential long-term impact of important trace species emitted in southern Africa • Atmospheric deposition can either be a source of toxic substances, or a source of nutrients for the ecosystem. • Biomass burning, land use changes and industrial activities lead to important emissions. Emissions may result in adverse effects on vegetation/water/soil systems.
Project motivation and objectives • To determine the regional scale atmospheric budgets of key pollutant species • To measure the long term atmospheric removal rates through dry and wet deposition of biogeochemical important trace species • To provide data for an integrated scientific assessment of atmospheric C, S and N cycles at regional scale • To provide data on deposition that can be related to impact studies, with special focus on N and other key species and their impacts on ecosystems and hydrology
Current measurements • Gas concentrations Passive gas sampling (month) for SO 2 , NO 2 , NH 3 , HNO 3 and O 3 • Chemical composition of precipitation Wet-only sampling (events), preservation by a biocide or by freezing US EPA quality criteria + annual analytical laboratory performance (WMO) pH, Conductivity, Inorganic and Organic major ions (Cl - , NO 3 - , SO 4 - , CO 3 2- , Na + , NH 4 + , K + , Mg 2+ , Ca 2+ , 2- , HCO 3 HCOOH, CH 3 COOH, C 2 H 5 COOH) • Chemical composition of aerosols Monthly sampling – PM2.5 and PM10 Inorganic and organic major ions (Cl - , NO 3 - , SO 4 2- , HCO 3 - , CO 3 2- , Na + , NH 4 + , K + , Mg 2+ , Ca 2+ , HCOOH, CH 3 COOH, C 2 H 5 COOH) Particulate carbon (TC, OC and BC)
Importance of nitrogen deposition • Negative effects of nitrogen deposition include acidification (acid rain), eutrophication (algal blooms) and soil leaching • The atmosphere is a critical environment for the nitrogen cycle (cascade effect) • Nitrogen deposition is essential to the function of terrestrial ecosystems – therefore essential in regulating the global carbon cycle • Direct toxicity from wet deposition of N is rare, while dry deposition of NH 3 can damage plants (specifically the stomata) • Literature results show that atmospheric nitrogen fixing ability may vary with age of plants and soil nutrient conditions (S.M. Jacobs et al. , 2007)
Results: Gaseous measurements (monthly) Monthly concentrations at Skukuza for 2009 0.14 0.45 0.4 (HNO 3 values on secondary axis) 0.12 Deposition (kg N / ha / month) 0.35 0.1 0.3 0.08 0.25 0.2 0.06 0.15 0.04 0.1 0.02 0.05 0 0 NH3 NO2 HNO3 2 per. Mov. Avg. (HNO3)
Results: Gaseous measurements (monthly) Monthly concentrations at Skukuza for 2009 0.14 0.45 0.4 (HNO 3 values on secondary axis) 0.12 Deposition (kg N / ha / month) 0.35 0.1 0.3 0.08 0.25 0.2 0.06 0.15 0.04 0.1 0.02 0.05 0 0 NH3 NO2 HNO3 2 per. Mov. Avg. (NH3)
Results: Gaseous measurements (monthly) Monthly concentrations at Skukuza for 2009 0.14 0.45 0.4 (HNO 3 values on secondary axis) 0.12 Deposition (kg N / ha / month) 0.35 0.1 0.3 0.08 0.25 0.2 0.06 0.15 0.04 0.1 0.02 0.05 0 0 NH3 NO2 HNO3 2 per. Mov. Avg. (NO2)
Results: Aerosol measurements (monthly) Skukuza particulate nitrogen (max values) 0.140 Deposition values (kg N / ha / month) 0.120 0.100 0.080 0.060 0.040 0.020 0.000 PM 2.5 NO3- PM 2.5 NH4+ PM 10 NO3- PM 10 NH4+
Results: Rainwater analyses Skukuza rainfall measured by SAWS 90 80 70 Rain gauge reading (mm) 60 50 40 30 20 10 0
Results: Rainwater analyses (monthly) Skukuza wet deposition 0.3 Deposition values ( Kg N / ha / month) 0.25 0.2 0.15 0.1 0.05 0 N in NH4+ N in NO3-
Results: Total deposition (monthly) Monthly total N deposition 1.200 Deposition values (kg N / ha / month) 1.000 0.800 0.600 0.400 0.200 0.000 Gaseous Particulate Raiwater Total
Results: Rainwater (annual) compared to other sites Skukuza 2009 Vaal Pukke 2009 Amersfoort 2009 Louis Trichardt 2009 Wet Deposition Wet Deposition Wet Deposition Wet Deposition Ions kg.ha-1.yr-1 kg.ha-1.yr-1 kg.ha-1.yr-1 kg.ha-1.yr-1 4.75 4.44 4.33 4.61 pH 0.142 0.465 0.390 0.193 H+ 1.715 0.724 3.747 1.663 Na+ 1.243 5.192 2.951 1.089 NH4+ 0.965 4.029 2.290 0.845 (N in NH4+) 0.683 0.728 1.166 0.203 K+ 0.409 3.399 1.202 0.425 Ca2+ 0.209 0.628 0.258 0.217 Mg2+ 4.602 11.647 9.520 3.043 NO3- 1.039 2.630 2.150 0.687 (N in NO3-) 3.149 1.737 6.449 2.926 Cl- 5.585 29.195 22.214 4.890 SO42- 1.861 9.725 7.400 1.629 (S in SO42-) 0.999 4.172 1.679 2.235 HCOO- 0.032 0.453 0.438 0.086 CH3COO- 39 76 51 26 Nr of events 604.50 857.50 708.00 840.00 Total rainfall (mm)
Closing comments • Monthly total nitrogen deposition ranges between a minimum of 0.151 kg N / ha / month at the end of the dry season, to a maximum value of 0.968 kg N / ha / month at the beginning of summer (during wet season) • Gasous deposition and wet deposition contributes the most to the total annual nitrogen deposition, while particulates are significantly less. • Total nitrogen deposition in the KNP was calculated to be around 5.343 kg N / ha / yr for 2009 • Rainwater comparisons showed that total wet nitrogen deposition are highest in the Vaal Triangle, followed by the Highveld, Skukuza and Louis Trichardt
Acknowledgements
Recommend
More recommend
