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Home Themes & Results Nutrients (I2) Physicochemical and hydrological characterization

Rivers – Physico-chemical and hydrological characterization of the studied river reaches

Physicochemical and hydrological features play a key role in the interpretation of nutrient retention dynamics, enabling the description of the baseline water composition and the definition of primary aspects influencing water residence time and water-sediment exchanges.
The discharge of selected river reaches covered a wide range of variability  with values ​​varying from 5 to 200 l s-1 in Piedmont and 10-300 l s-1 in Sardinia. In line with the prerogatives of the experimental plan, there are no sites characterized by very high flow rate that could compromise the results obtained with the experiment additions.

Sardegna     Piemonte


With regard to the morphological features, we found a high variety of  flow and substrate types, in particular in  Sardinian sites, while in Piedmont coarse grain sizes and turbulent flows prevailed.
A great spatial variability characterized the hyporheic system with large differences within the investigated reaches (along 100m). This has raised the need for the definition of some indicators able to better integrate the eterogeneity/omogeneity of the parameters and thus useful for a comparison with  the retention metrics.  
As expected, the chemical composition of the surface waters was different between the two regions. The high NaCl concentrations in the Sardinian  streams indicated the influence of marine aerosols varying with the distance of each site from the seashore. Differently, in the Piedmont streams the most abundant ionic species were HCO3,  Ca and Mg  deriving from the leaching of carbonate rocks.
As for the nutrients and contaminants in trace chemical analysis made ​​it possible to confirm the choices of the experimental plan which provided for the exclusion of sites characterized by an important pollution source end (discharge civil, industrial and spillways).
Regarding nutrients and trace contaminants, the chemical analyses allow to confirm the experimental assumptions that excluded point sources contaminated sites (sewages, spillways, etc). In Piedmont NH4 and PO4 concentrations were in most cases below the detection limit, while in the Sardinian reaches the levels were slightly higher and distributed over a wider range. These conditions are probably due to the widespread presence of farm animals (sheep, goats and cows) in the vicinity of watercourses in Sardinia. Contrary to NH4, NO3 concentration was, on average, higher in Piedmont and this is presumably related to higher nitrogen atmospheric loads and to an intensive agriculture requiring the use of great amounts of nitrogen fertilizers.
Deliverable I2d1 contains the full description of this activity.


Chemico-physical variables concentration for Piedmont HER06 river reaches

  Unit N Mean Min Max Median 25%ile 75%ile
O2 mg/l 16 10.7 6.50 13.7 10.45 9.90 11.50
O2 % 16 98.6 75.0 111.0 99.0 94.8 103.0
BOD5 mgO2/l 16 3.38 2.00 8.00 2.00 2.00 4.25
COD mgO2/l 16 7.69 5.00 21.00 5.00 5.00 9.00
pH   25 7.30 6.55 8.50 7.20 7.00 7.45
Cond. µS/cm 25 110.5 36.0 175.0 128.1 96.8 134.0
HCO3 meq/l 19 0.65 0.23 1.21 0.60 0.36 0.87
N-NH4 mg/l 21 0.06 D.L 0.36 D.L D.L 0.03
N-NO3 mg/l 25 1.14 0.20 2.10 1.10 0.80 1.40
TN mg/l 16 2.32 1.20 3.60 2.15 1.85 3.00
P-PO4 mg/l 24 0.06 0.04 0.260 0.05 0.04 0.05
TP mg/l 16 0.09 0.05 0.33 0.05 0.05 0.07
SO4 mg/l 25 5.5 1.6 11.0 4.0 3.0 6.4
Cl mg/l 25 8.2 1.0 24.3 5.4 3.5 12.6
Ca mg/l 16 10.6 3.1 16.8 11.8 7.6 14.0
Mg mg/l 16 5.0 D.L 7.9 4.4 2.7 7.0
Na mg/l 16 6.3 3.0 10.6 5.6 3.7 9.1
K mg/l 16 1.84 D.L 5.4 1.1 D.L 1.6
S.S mg/l 16 17 10 76 10 10 19


Chemico-physical variables concentration for Sardinia – May2011 river reaches

  Unit N Mean Min Max Median 25%ile 75%ile
O2 mg/l 13 9.2 8.1 9.6 9.3 9.0 9.6
O2 % 13 98.3 94.0 102.0 98.0 96.0 101.0
pH   13 7.40 7.10 7.8 7.4 7.1 7.6
Cond. µS/cm 13 406 145 856 393 258 314
HCO3 meq/l 12 1.42 0.40 2.20 1.40 1.33 1.60
N-NH4 mg/l 13 0.036 0.008 0.117 0.027 0.016 0.053
N-NO3 mg/l 13 0.66 0.04 2.20 0.60 0.20 0.70
P-PO4 mg/l 13 0.059 0.002 0.260 0.025 0.005 0.048
TP mg/l 12 0.100 0.006 0.280 0.040 0.015 0.057
SO4 mg/l 13 23.9 8.35 42.6 24.0 15.9 32.0
Cl mg/l 13 83.2 22.5 248 67.5 43.2 115
Ca mg/l 13 19.7 3.71 36.6 20.8 16.9 22.8
Mg mg/l 13 11.5 2.67 22.6 13.1 6.5 14.5
Na mg/l 13 48.8 18.7 123 39.8 32.3 61.3
K mg/l 13 1.6 0.3 3.4 1.4 1.2 2.1