Assessing the origin of the acidity in a humic boreal river draining peatlands and sulfide-bearing soil materials

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Rosamond Joan Shields
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1 Assessing the origin of the acidity in a humic boreal river draining peatlands and sulfide-bearing soil materials Jaakko Saukkoriipi, Martinmäki, K., Marttila, H., Heikkinen, K., Tammela, S., Tertsunen, J., Tolkkinen, M., Ihme, R. & Klöve, B. Finnish Environment Institute (SYKE), BO Box, 9 Oulu, Finland University of Oulu, BO Box, 9 Oulu, Finland Centre for Economic Development, Transport and the Environment of North Ostrobothnia, BO Box 8, 9 Oulu, Finland

2 Background Total catchment area is ~ km and the proportion of lakes is, %. Catchment area is mainly covered by mires and forests. Intensively drained! Land use Coverage [%] Agricultural land, Pristine peatlands, Ditched peatlands 8, Peat extraction, Black schist regions 8,8 / of the catchment area is covered by sulfidebearing soils and black schist regions. Temporary acidic peaks detected during spring and autumn high runoff. Fish kills in -. Assessment of the origin of the acidity! The work was conducted in City and Water Ecological enhancement and improvement of recreational value of river Sanginjoki project!

3 Catchment characteristics Mä st sampling period: set of samples in (May - October) nd period: sets of samples in (April May)

4 Methods Due to the high coverage of peatlands and sulfide-bearing sediments/till in the watershed, the assesment of the origin of the acidity in river Sanginjoki was performed as follows:. Comparison of the organic anion [A - ] and non-marine sulphate [*SO - ] concentrations. Ion balance & model based on titration results of isolated hydrophobic and hydrophilic acids (a. Sea salt corrected sulphate concentration.. Statistical analysis of the water quality variables.. Comparison of the collected data to a hydrogeochemistry of other streams affected by a.s. soils. (a Kortelainen P., Ph.D. Thesis, University of Helsinki, Publications of the Water and Environment Research Institute, no., Helsinki 99.

5 Organic anion vs. non-marine sulphate,,,,8,,,, The organic anion concentration exceeded the non-marine sulphate concentration in all main channel sampling sites. D,,,,,8,,8 *[SO-]/*[BC] *[SO-]/*[BC],, [A-]/*[BC] [A-]/*[BC],,,, A J I,,,,,,,,,,,,,8,,, *[SO-]/*[BC] [A-]/*[BC],,,,8,,,, *[SO-]/*[BC] [A-]/*[BC]

6 EC (µs/cm) EC (µs/cm) Al (mg/l) Al (mg/l),,, Statistical analysis r p =,** r s =,** y =,x +,8 R² =,,,, r p =,8** r s =,**,,,,,, y =,x +,8 R² =,, y = -,9x +,9 R² =,9, y = -,x +,8 R² =,,,, r p = -, r s = -,, r p = -,8** r s = -,8** r p =,** r s =,** y =,9x +,9 R² =, r p =,** r s =,** y =,8x +,9 R² =, Suphate (mg/l) **Correlations significant at the, level (n = 98) Dissolved organic carbon (mg/l)

7 Longer term trends,, n = 9 n = 8, r p =,** r s =,99**,,, y =,x +, R² =,8 8 Sulphate (mg/l),, r p = -,8** r s = -,** y = -,9x +, R² =,89 COD Mn (mg/l) **Correlations significant at the, level The low values were associated with high DOC or COD Mn concentrations in the drainage basin. Longer term data collected from the national Hertta database (99- for COD Mn and 998- for SO - ).

8 DOC [mg/l] DOC [mg/l] SO [mg/l] SO [mg/l] Discharge [m/s] DOC [mg/l] Discharge [m/s] DOC [mg/l] Discharge vs. DOC/SO -,,,8,,, Sanginsuu Discharge DOC,,, Koivujoki Discharge DOC n = r s = -,8 y = -,8x +, R² =, y = -,x +,8 R² =, r s = -,9,, r s = -,9 y = -,8x +,8 R² =,,, Discharge [m/s] **Correlations significant at the, level r s = -,** y = -,x + 8,8 R² =,8 Discharge [m/s] 8

9 The hydrochemistry of river Sanginjoki vs. streams affected by a.s. soils Detected sulphate and metal concentrations were notably higher in streams that were known to be affected by a.s. soils in the drainage basin. Detected EC values were also low in river Sanginjoki compared to the streams in western Finland. EC (µs/cm) SO - (mg/l) Fe (mg/l) Al (mg/l) Mn (µg/l) Zn (µg/l) River Sanginjoki (n=9) Streams in western Finland (n=) Headwater streams in Finland (n=) MIN MED MAX MIN MED MAX MED,,,,,8,9,,, Data from Åström et al., 99 Data from Lahermo et al., 99., 8, 9,,,, BD,, 8,, 8,8,9,,8,9 9, 9

10 Conclusions The average organic anion concentration exceeded the non-marine sulfate concetration in all main channel sampling sites and 8 times out of in the tributaries. Low values were associated with high DOC concentrations in the drainage basin. Detected sulfate and aluminum concentrations were low compared to other streams affected by a.s. soils. The results indicate that the leaching of organic acids from the catchment area, was the primary cause of the acidity in river Sanginjoki during sampling period!

11 Thank You!

**Finnish Environment Institute (SYKE) hoto: Roland Lensch

**Finnish Environment Institute (SYKE) hoto: Roland Lensch Increasing organic carbon concentrations in the raw water source of Helsinki H. Poutanen*, A. Räike**, M. Forsius**, V. Vuorilehto* ** Helsinki Region Environmental Services Authority HSY **Finnish Environment