Reducing agricultural phosphorus load by gypsum: results from the first year after amendment

Transcription

1 Reducing agricultural phosphorus load by gypsum: results from the first year after amendment Photo: Janne Artell Petri Ekholm Finnish Environment Institute SYKE

2 Contents What is gypsum and how it works SAVE project A large pilot going on in southwestern Finland Preliminary results from the effects of gypsum on particulate P and dissolved P Potential side-effects Sulfate Future plans

3 What is gypsum (CaSO 4 2H 2 O)? Naturally present in rock A voluminously formed side-product of phosphorus acid manufacturing Also formed e.g. in flue-gas desulfurization In our pilots, gypsum originated from Yara s igneous apatite mine in Siilinjärvi Safe to use, contains no heavy metals or radioactivity Unlike CaCO 3, does not affect ph

4 How gypsum works? After dissolution to Ca 2+ and SO 2-4 ions the ionic strength of soil solution increases Electrical double layer around soil particles is suppressed Particles can come closer, form larger aggregates and become less sensitive to erosion Desorption of P also reduced Before gypsum After gypsum The TraP project ( ) 100 hectares of clayey soil amended with gypsum 60% reduction in the losses of particulate P and 30% in dissolved P* Effect lasted about 4 years No negative effects on yield (Se) DRP PP *Ekholm P, Valkama P, Jaakkola E, Kiirikki M, Lahti K, Pietola L Gypsum amendment of soils reduces phosphorus losses in an agricultural catchment. Agricultural and Food Science 21:

5 Why gypsum? HELCOM s Baltic Sea Action Plan Finland has to reduce the load of P into the Gulf of Finland by 364 t y 1 Even if all the planned measures were fully implemented, the target would fall about 250 t y 1 short (Knuuttila et al. 2017) A need for efficient P abatement measures in agriculture A tentative estimate: gypsum amendment of agricultural fields could reduce the P load into the Gulf of Finland by 50 t y 1 the Archipelago Sea by 100 t y 1 Cost about 66 kg 1 P (gypsum, transportation, spreading) Knuuttila S, Räike A, Ekholm P, Kondratyev S Nutrient inputs into the Gulf of Finland: Trends and water protection targets Journal of Marine Systems. Journal of Marine Systems 171:54 64.

6 SAVING THE ARCHIPELAGO SEA BY APPLYING GYPSUM TO AGRICULTURAL FIELDS Aims to Study the performance of gypsum in yet a larger pilot Test gypsum transport and spreading Survey farmers attitudes towards gypsum Make a plan for gypsum treatment of all the potential fields in Finland

7 Apatite mine in Siilinjärvi Gypsum formed as a side-product Pilot area: the River Savijoki The mine The pilot area 144 lorries transported 6.27 million kg gypsum 55 farms taking part in the pilot Gypsum spread on 1530 hectares of fields in autumn 2016 Photos: Janne Artell, Eliisa Punttila, Petri Ekholm A hint of gypsum (4000 kg/ha)

8 Runoff in the Savijoki Gypsum spreading Before gypsum After gypsum

9 Field parcels Gypsum No gypsum The River Savijoki (SW Finland) Relatively homogeneous area in terms of Soil type of the fields (clay) Cultivation practices No other major loading sources Gypsum area Reference area River channel Control site Catchment area 15 km 2 No gypsum Gypsum area, middle site Catchment area 33 km 2 28% upstream fields amended Gypsum area, lower site Catchment area 82 km 2 43% upstream fields amended Gypsum effect increases 9 All the sites equipped with online sensors and visited (quite) frequently for water quality sampling

10 Immediate effect Treated with gypsum Not treated Photos: Janne Artell

11 Mikko Kiirikki Estimation of the losses of particulate P Estimation of the concentrations of particulate P Runoff measurements q, (l s 1 km 2 ) C PP (µg l 1 ) = Turbidity Calculation of hourly losses of particulate P L PP (g km 2 h 1 ) = q C PP 3600/ Summing up for daily losses Comparison of pre- and post-gypsum losses in the control and gypsum areas

12 Loss of particulate P before the gypsum amendment (g km 2 d 1 ) Area Pre-gypsum d During gypsum d Post-gypsum d Runoff (mm) Control Gypsum area middle % % % Gypsum area lower % % % Before gypsum The loss of particulate P about one third higher in the gypsum area than in the control area

13 Loss of particulate P before and during the gypsum amendment (g km 2 d 1 ) Area Pre-gypsum d During gypsum d Post-gypsum d Runoff (mm) Control Gypsum area middle % % % Gypsum area lower % % % During the three months of gypsum spreading The loss of particulate P was smaller from the gypsum area The period was exceptionally dry

14 Loss of particulate P before, during and after the gypsum amendment (g km 2 d 1 ) Area Pre-gypsum d During gypsum d Post-gypsum d Runoff (mm) Control Gypsum area middle % % % Gypsum area lower % % % Note: only 43% of fields upstream of the lower site were amended with gypsum To reach a 28.4 % decrease in the overall loss of particulate P, the loss from gypsum amended fields has been 66% smaller (lower site) than from non-treated fields

15 Concentration of dissolved reactive P (µg l 1 ) Area Pre gypsum days Gypsum amendment days Post gypsum days n Control Gypsum area middle Gypsum area lower % % DRP concentration about 25% lower in runoff from gypsum amended fields than from unamended fields

16 Soil and plant analyses Soil analyses Soil type Loss on ignition Electrical conductivity ph Ca, Kg, K, Na, Cation exchange capacity P S Plant analyses N, P, K, Ca, Mg, Fe, Cu, Mn, Zn, B, S, Se 16

17 Potential side-effects? Sulfate concentrations after gypsum spreading in the lower site Mean concentration Before 16 mg/l After 33 mg/l Thick-shelled river mussels

18 Photos: Johanna Salmelin, Rami Laaksonen, Satu Maaria Karjalainen, Katri Siimes, Heidi Ahkola, Maija Hannula, Wikipedia Potential side-effects? Thick shelled river mussel (Unio crassus) glochidium and adults Moss (Fontinalis antipyretica) Diatoms Incubation experiment with salmon eggs Ground water Pesticides

19 Length (mm) Alive (%) Salmeilin et al. & Rantamo K., unpublished data So far no harmful effects found Growth of moss (Fontinalis antipyretica) in 21-day incubation Survival of glochidium larvae of thickshelled river mussel (Unio crassus) in 2-day incubation

20 Photo: Seppo Knuuttila Sulfate-induced eutrophication Labile C Algae PO 4 (diss) FeOOH~PO 4 (S) 1Τ 2 H Τ2 SO 2 4 (l) + 1 Τ2 C 2 H 3 O 2 1 Τ 2 H 2 S(g) + HCO 3 O 2 15Τ 2 H + + 4FeOOH (s) + 1 Τ2 C 2 H 3 O 2 HCO 3 + 4Fe 2+ (l) + 6H 2 O FeS (s)

21 Photo: Jouni Lehtoranta Can gypsum be used in lake catchments? An experiment will be started with different levels of Sulfate Iron oxides Labile carbon? Internal load External load 21

22 Farmer survey 87% of the farmers responded to a questionnaire 78% would use gypsum, if it were subsidized by the agrienvironmental support scheme 72% considered that local people sympathised with gypsum use 70% would recommend gypsum to other farmers 56% considered that gypsum is an easy agri-environmental measure 6% experienced problems in gypsum spreading BUT: the autumn 2016 was perfect (= dry) for gypsum amendment 22

23 Tentative assessment of the potential of gypsum in the Archipelago sea catchment Catchment area 6580 km 2 (excluding islands) Field area 2020 km 2, of which not suitable the fields located Upstream of lakes On acid sulfate soils On groundwater areas Near Natura2000 sites Area of suitable fields Area (km 2 ) All fields 1320 Fields on mineral soils 220 Fields on clay soils 1060 Fields on organic soils 40 Current P loss 2020 km kg km 2 y 1 P = 222 t y km kg km 2 y 1 P = 117 t y 1 After gypsum amendment (assuming a 50% reduction) 1060 km kg km 2 y 1 P = 58 t y 1 A reduction of 59 t y 1

24 Future tasks The Savijoki will be monitored (at least) till the end of 2018 Water quality, soil and plants, groundwater, mussels, farmers attitudes So far 10% of the applied gypsum flushed away How long do we see a gypsum effect? Plan for a larger scale gypsum treatment including the entire southern Finland and other areas around the Baltic Sea any volunteers?

25 CONTACT Professor Markku Ollikainen, markku.ollikainen (a) helsinki.fi Senior researcher Petri Ekholm, petri.ekholm (a) environment.fi Project coordinator Eliisa Punttila, eliisa.punttila (a) helsinki.fi FACEBOOK & & READ MORE nutritradebaltic.eu blogs.helsinki.fi/save-kipsihanke