Reduction in Acid rain and Climate change are disguising abatement effects

Transcription

1 Reduction in Acid rain and Climate change are disguising abatement effects EUTROPIA Final conference Prof. Rolf D. Vogt PhD stud.: Chr. W. Mohr., A. Engebretsen Master stud.: S.S. Weldehawaria, M.S. Shekobe, N.A. Parekh, Y.K. Gebreslasse, K.A.J. Opland, Y. Desta Visiting scholars: L.G. Gener, K. Lukawska, P. Junquet and A. Baxter

2 Phosphate sources DNOM-P Particulate P and PO 4 Blankenberg et al

3 Phosphate sources DNOM-P 48% of the P input to the lake originates from agricultural areas Particulate P and PO 4 Blankenberg et al

4 Phosphate sources Particulate P and PO 48% of the P input to the lake originates 4 from agricultural areas P is mainly transported in the rivers adsorbed to silt and clay particles (Particulate P) DNOM-P Blankenberg et al

5 Phosphate sources DNOM-P 48% of the P input to the lake originates from agricultural areas P is mainly transported in the rivers adsorbed to silt and clay particles (Particulate P) Particulate P and PO 4 Blankenberg et al The natural background flux of P accounts for 39% of the P flux Mainly in the form of dissolved natural organic matter (DNOM-P)

6 Reduction in acid rain Sulphate in precipitation has decreased by 75 91% Decrease in the conc. of sulphate in surface waters in Norway by 44 81% µeq/l Non-marine Sulphate Avg. decrease in 78 lakes in Norway Skjelkvåle (ed.), 2012

7 Reduction in acid rain Sulphate in precipitation has decreased by 75 91% Decrease in the conc. of sulphate in surface waters in Norway by 44 81% Most pronounced in South-eastern Norway µeq/l Non-marine Sulphate Avg. decrease in South-Eastern Norway Skjelkvåle (ed.), 2012

8 Effect of reduction in acid rain 1. Decreased leaching of labile Aluminium (Ali) 2. Increased leaching of Dissolved Natural Organic Mater (DNOM) Most pronounced effect on the leaching from acid forested catchments, comprising 80% of the watershed µg/l mg/l Labile Aluminium Total organic carbon Skjelkvåle (ed.), of 23

9 Stream water studies 9 streams draining into western Vansjø Morsa

10 Stream water studies 9 streams draining into western Vansjø Agriculture Forest Land-use vary from only agriculture to 100% forest

11 Distribution of PO 4 fractions Clear distribution depending on land use and discharge o Particulate-P dominate in runoff from Agricultural land o DNOM-P dominate in discharge from forested catchments ohigh conc. of Particulate P esp. during discharge Episodes (E) Parekh, 2012

12 Forest soil chemistry Soil acidity and P pools were studied on 38 forest soil samples collected from generic horizons on ridge, slope and valley-bottom from 8 sites in the Morsa watershed 7 of 23

13 Acid sensitive forest soils 10µM Ali 7,00 Ridge Slope Valley Bog ph(h2o) 6,50 6,00 5,50 5,00 4,50 Average Max Min Median Most of the soils are strongly acidic with a ph in which Ali is soluble in significant concentrations 4,00 3,50 3,00 O A E B O A E B C O A B C H C Number of samples Soil Horizons Desta, 2013

14 Acid sensitive forest soils 100 Ridge Slope Valley Bog Half of the soil samples had Base Saturation (BS) <30% %BS comparable to sites with high Ali conc. during the acid rain period BS % Average Max Min Median 10 0 O A E B O A E B C O A B C H C Number of samples Soil Horizons Desta, 2013

15 Distribution of land-use Most watercourses drain forests areas and passes agricultural land downstream before entering the lake

16 Mixing experiment Runoff from agricultural land Runoff from forested catchment

17 100 Removal of PO Between 60 80% of PO 4 in agricultural runoff becomes particulate P upon mixing with Ali rich forest runoff % PO 4 removed Ali/PO 4 1,3 1,0 0,8 0,6 0,6 0,6 0,6 0,4 0,4 0, Minutes after mixing Shekobe, 2012

18 Precipitation of PO 4 with Aluminium Labile aluminium that was leached out of acid sensitive forests drained down into agricultural land where it mixed with PO 4 rich seepage with higher ph Skjelkvåle et al., 2007 Al(OH) 3 precipitated and co-precipitated PO 4 With the decline in acid rain we have lost an important mechanism for PO 4 removal Al AA 3+ + PP OO AA 1.4 PP 4 OO 1.2 (s) OH - PO 4 3- Al(OH) 3 Al 1.4 PO 4 (OH) 1.2

19 What does this amount to? SO 4 Ali The avg. sea-salt corr. sulphate conc. in this region was 5 times higher during the acid rain period (Skjelkvåle (ed), 2012) An assumption is that the volume weighted average Ali concentration in the streams draining forested headwaters in the Morsa watershed during the acid rain period was around 3 x 5 µm = 15 µm 13 of 23

20 What does this amount to? The runoff from forest is 5 times greater than from agricultural land 1 mol of Al removes 0,7 mol PO 4 15 µm x 5 x 0,7~ 50µM Al leaching of Ali could theoretically have lowered the conc. of PO 4 by about 50µM The PO 4 conc. in the streams are usually less than 2.5 µm 14 of 23

21 40 What happens with particle bound PO 4? ug P/L Agriculture 430 Totalfosfor (µg/l) juni-september Forest Partikulært P PO4 Løst organisk P Tot-P in the lake varies between μg P/L april-oktober År 80% 50 0 STØ1 ØRE HUG VAS ÅRV SPE AUG GUT DALEN Lake There is low total-p concentrations in the lake compared to what comes with the streams.. Is it possible that Particle bound P does not contribute so much to the total-p in the lake as it is just sedimented?

22 40 What happens with particle bound PO 4? ug P/L ug P/L Agriculture 70 Totalfosfor (µg/l) juni-september Forest Partikulært PO4P PO4 Løst organisk Løst organisk P P Tot-P in the lake varies between μg P/L april-oktober År 80% 0 STØ1 ØRE HUG VAS ÅRV SPE AUG GUT DALEN So if this is the case.. Then the background flux of humic bound PO 4 (DNOM-P) from forests will play a major role

23 Transport of PO 4 with DNOM mg/l PO 4 is in natural systems transported with DNOM Ron Vaz et al., 1992 Skjelkvåle (ed.), PO4 Løst organisk P ug P/L STØ1 ØRE HUG VAS ÅRV SPE AUG GUT DALEN

24 Transport of PO 4 with DNOM mg/l PO 4 is in natural systems transported with DNOM There has been a doubling in the concentrations of DNOM The 40% background flux of DNOM-P has thus likely doubled Skjelkvåle (ed.), PO4 Løst organisk P ug P/L STØ1 ØRE HUG VAS ÅRV SPE AUG GUT DALEN

25 Changes in climate during the last 20+ years The amount of precipitation and the frequency of heavy precipitation events have increased and been above the norm during the past 20 years Precipitation in % of norm Precipitation in % Winter of temperature norm deviation from norm Met.no

26 Changes in climate during the last 20+ years The amount of precipitation and the frequency of heavy precipitation events have increased and been above the norm during the past 20 years Generates more surface runoff and flooded soils Precipitation in % Winter of temperature norm deviation from norm Precipitation 20 years Met.no

27 Changes in climate during the last 20+ years The amount of precipitation and the frequency of heavy precipitation events have increased and been above the norm during the past 20 years Generates more surface runoff and flooded soils Average winter temperature has been 2ºC over the norm during the past 25 years Winter temperature deviation from norm Met.no

28 Changes in climate during the last 20+ years The amount of precipitation and the frequency of heavy precipitation events have increased and been above the norm during the past 20 years Generates more surface runoff and flooded soils Average winter temperature has been 2ºC over the norm during the past 25 years Leads to more frequent thaw periods on barren and frozen soils 30 Januar 31 Januar Erosjon: kg ha -1 Winter temperature Foto: Øygarden, years Met.no

29 Andre endringer i klilma Vår temperatur Sommer nedbør Våren er varmere Raskere snøsmelting Sommerene er våtere Mer kraftig regn Hyppigere oversvømmelser

30 What is the relevance of Increased surface runoff?

31 What is the relevance of Increased surface runoff? Large amounts of inorganic and organic bound P in the plough layer (Ap) and in the forest floor (O) Agriculture - Forest - Podzol Soil Horizon O AE B C O AE B C H AB C Ridge Slope Valley Inorg-P Org-P Opland, 2011 H C Desta, 2013 Bog

32 What is the relevance of Increased surface runoff? Large amounts of inorganic and organic bound P in the plough layer (Ap) and in the forest floor (O) Increased erosion of particle bound P from agricultural soils Increased leaching of DNOM-P from surface forest soil layers

33 What is the relevance of Increased surface runoff? Large amounts of inorganic and organic bound P in the plough layer (Ap) and in the forest floor (O) Increased erosion of particle bound P from agricultural soils Increased leaching of DNOM-P from surface forest soil layers Flushing of total-p during episodes ug Total P/L Huggenesbekken L/s discharge

34 Increased flooding µg P/L 40 Western Vansjø År Morsa, 2011 Yr.no

35 Increased flooding The flood in 2000 led to especially large fluxes of total-p to western Vansjø the following year This may partly be due to water logged iron rich soils µg P/L Morsa, 2011 Western Vansjø År

36 Water logged and iron rich soils Soils south of western Vansjø have high iron (Fe) content Fe(III) binds PO 4 3- : FePO 4, R-Fe-PO 4 where R is clay or organic material with net negative charge Huggenes In water logged soils the Fe(III) is reduced to Fe(II) This reduces the soils capacity to hold PO 4 which therefore is leached out This may be an important cause for increased leaching of potentially bioavailable PO 4 and algae blooming after the flood Støa 2

37 Milder winters More frequent runoff periods during winter Increased surface runoff and erosion due to soil frost and fall tillage P g/daa/day Total P at Støa1 during a relatively warm winter 2007/ Discharge (L/s) Date estimated tot P (g/daa/day) Runoff (L/s) Temperature p g/daa/day Total P at Støa1 during a relatively cold winter, 2009/ Discharge(L/s) Large flux of bioavailable PO 4 due to no assimilation Parekh, 2012

38 Important nature science knowledge More precipitation and milder winters have led to greater flux of P: By increased surface runoff through only P rich surface soils Decline in acid rain has led to: That an important precipitator (Al) of bioavailable PO 4 is lost Increased background flux of DNOM-P Conclusion: Without the abatement actions the eutrophication would today have been much worse! 23 of 23