Estimated total nitrogen deposition and rainwater composition - - PowerPoint PPT Presentation

EH Conradie

Ph.D student

“Estimated total nitrogen deposition and rainwater composition measured in the Kruger National Park” March 2011

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

Passive gas sampling (month) for SO2, NO2, NH3, HNO3 and O3

• Gas concentrations

pH, Conductivity, Inorganic and Organic major ions (Cl- , NO3

• , SO4

2-, HCO3

• , CO3

2-, Na+ , NH4 +, K+, Mg 2+ , Ca 2+,

HCOOH, CH3COOH, C2H5COOH) Wet-only sampling (events), preservation by a biocide or by freezing US EPA quality criteria + annual analytical laboratory performance (WMO)

• Chemical composition of precipitation

Monthly sampling – PM2.5 and PM10 Inorganic and organic major ions (Cl-, NO3

• , SO4

2-, HCO3

• , CO3

2-, Na+, NH4 +, K+, Mg 2+, Ca2+,

HCOOH, CH3COOH, C2H5COOH) Particulate carbon (TC, OC and BC)

• Chemical composition of aerosols

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

NH3 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)

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Deposition (kg N / ha / month) (HNO3 values on secondary axis)

Monthly concentrations at Skukuza for 2009

NH3 NO2 HNO3 2 per. Mov. Avg. (HNO3)

Results: Gaseous measurements (monthly)

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Deposition (kg N / ha / month) (HNO3 values on secondary axis)

Monthly concentrations at Skukuza for 2009

NH3 NO2 HNO3 2 per. Mov. Avg. (NH3)

Results: Gaseous measurements (monthly)

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Deposition (kg N / ha / month) (HNO3 values on secondary axis)

Monthly concentrations at Skukuza for 2009

NH3 NO2 HNO3 2 per. Mov. Avg. (NO2)

Results: Aerosol measurements (monthly)

0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140

Deposition values (kg N / ha / month)

Skukuza particulate nitrogen (max values)

PM 2.5 NO3- PM 2.5 NH4+ PM 10 NO3- PM 10 NH4+

Results: Rainwater analyses

10 20 30 40 50 60 70 80 90

Rain gauge reading (mm)

Skukuza rainfall measured by SAWS

Results: Rainwater analyses (monthly)

0.05 0.1 0.15 0.2 0.25 0.3

Deposition values ( Kg N / ha / month)

Skukuza wet deposition

N in NH4+ N in NO3-

Results: Total deposition (monthly)

0.000 0.200 0.400 0.600 0.800 1.000 1.200

Deposition values (kg N / ha / month)

Monthly total N deposition

Gaseous Particulate Raiwater Total

Results: Rainwater (annual) compared to

• ther 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 pH

4.75 4.44 4.33 4.61

H+

0.142 0.465 0.390 0.193

Na+

1.715 0.724 3.747 1.663

NH4+

1.243 5.192 2.951 1.089

(N in NH4+)

0.965 4.029 2.290 0.845

K+

0.683 0.728 1.166 0.203

Ca2+

0.409 3.399 1.202 0.425

Mg2+

0.209 0.628 0.258 0.217

NO3-

4.602 11.647 9.520 3.043

(N in NO3-)

1.039 2.630 2.150 0.687

Cl-

3.149 1.737 6.449 2.926

SO42-

5.585 29.195 22.214 4.890

(S in SO42-)

1.861 9.725 7.400 1.629

HCOO-

0.999 4.172 1.679 2.235

CH3COO-

0.032 0.453 0.438 0.086

Nr of events

39 76 51 26

Total rainfall (mm)

604.50 857.50 708.00 840.00

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