Water chemistry

Cenflumarin – 4MT 2015Teacher: Nathalie Verelst

Water chemistry partners

Water chemistry sampling sites

Methodology

• First we compare our data to last years data of measurements around the school.

• Then we compare our test strip data to the Walhorn, Emajõgi, Lake Melliste and Luutsna datasets.

• We try to identify the land use around the water body to explain the values.

T, S, ρ

• 2015 is warmer than 2014• If S↑ → ρ ↑• Measurement of S in the

Scheldt river might have been less accurate.

• The dock is a lot less saline, but it had rained a lot before the measurement.

Scheldt Pond Dock0

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T in °C 2014 T in °C 2015 S in PSU 2014

S in PSU 2015 Density in mg/cm³ 2014 Density in mg/cm³ 2015

pH, GH, KH

Scheldt Pond Dock0

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pH strips pH titration GH strips KH strips KH titration

• pH (titration) is slightly alkaline than the pond or the dock. This is because the Scheldt is more saline.

• KH is the same• GH is higher in the pond and dock

because water is not moving, i.e. there is more uptake of CO2 at the surface.

• Titration is the most accurate type of testing

• In comparison to 2014, the water has become a lot harder, it can now more easily bind with an acid an this will lower pH (see also the graph on the next slide).

CO2 & O2

• Before the water was more alkaline, though it contained a lot more CO2.

• With the rise of temperature, primary production consumed a lot of CO2 and a bit of O2 .

• The dock became less alkaline because of mixing with the Scheldt river.

Scheldt Pond Dock0

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02 in mg/l 2014 O2 in mg/l 2015 CO2 in mg/l 2014 CO2 in mg/l 2015

KH in °d 2014 KH in °d 2015 pH 2014 pH 2015

NO3, NO2 & NH4

Scheldt pond dock0

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NO3 2014 titration NO3 2015 titration NO3 2015 strips

NO2 2014 titration NO2 2015 titration NO2 2015 strips

NH4 2014 titration NH4 2015 titration

• In 2015 we have less ammonia in the Scheldt, pond & dock.

• In 2015 chemical oxidation of NO3 into NO2 was more pronounced in the Scheldt river.

• The amonium level clearly dropped in 2015. This might indicate a population of decomposers in anaerobic circumstances in the benthos.

PO4

Scheldt river Middlepond Dock0

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2014 2015

• There has been an increase of PO4 between 2014 & 2015. This increase is more pronounced in the dock and pond because circulation is low. The dock & pond are also connected. The most likely source of PO4 is the increase of nutrient load in the Scheldt river.

Copper

• In 2014 the lock was permanently closed and the water stayed on the same place and there was a lot of oil pollution. Recently the lock has been repaired and all values are just within normative values (norm = 0.1 mg/l).

Scheldt river Middlepond Dock0

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Cu_2014Cu_2015

T, S, ρ

• Conductivity measurements at respective temperatures were converted to psu.

• The Scheldt river, Cenflumarin dock and pond are brackish. If S↑ → ρ ↑

• Temperatures in Lake Melliste and Luutsna river are lower. Walhorn

1Walhorn

2Scheldt Pond Dock Tartu

River Emajõgi

Lake Melliste

Tartu County

Luutsna River, Tartu

County

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T in °C S in PSU Density in mg/cm³

pH, GH, KH• Salty water is more alkaline than

fresh water.• Orissaare has low hardness and

pH. The water will not easily bond to an acid.

• The hardest water is found in rivers that flow through mineral rich geological regions.

• Cenflumarin pond has a relatively high nutrient content and low uptakem the water will therefore be more likely to bond to an acid.

• Luutsna river has unusually low carbonate hardness.

Antwerp

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eldt R

iver

Antwerp

Cenflumari

n pond

Antwerp

Cenflumari

n dock

Tartu

River E

majõgi

Orissaa

re Koigi

Lake M

ellist

e Tart

u County

Luutsn

a Rive

r, Tart

u County

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pH GH KH

NO3, NO2, NH4

• Nitrates are higher in agricultural zones and in rivers that flow through agricultural zones.

• When it becomes warmer they form toxic nitrites. Titration of nitrites led to a false positive in the Scheldt river (NO2 high, T low), what about Emajõgi river?

• Decomposers can break down poisionous nitrites into NH4, though their productivity is low. NH4 was not measured in Estonia.

Walh

orn 1

Walh

orn 2

Antwerp

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eldt R

iver

Antwerp

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n pond

Antwerp

Cenflumari

n dock

Tartu

River E

majõgi

Orissaa

re Koigi

Lake M

ellist

e Tart

u County

Luutsn

a Rive

r, Tart

u County0

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NO3

NO2

NH4

Conclusion• It would be interesting if all partners could have measured

temperature, salinity, O2 and CO2 – content.• The values in the Cenflumarin dock changed significantly from

2014 untill 2015 because the lock connecting the dock to the Scheldt river has been reopened.

• The Walhorn sites suffer from a high nutrient load from agriculture, for Emajogi river we should consider not only the nutrient load, but also the temperature. In cold conditions, there will be no nutrient uptake.

• We were wondering whether the high nitrite value for nitrites in Emajõgi river was not a false positive, since no nitrates are present. Lake Melliste seems a rather clean water body.