Environmental Engineering Reference
In-Depth Information
Fig. 1
Sampling points at
the mining area of El Bierzo
construction is clearly noticeable, attending to the data of the Confederación
Hidrográfica del Norte for the NO01590001 Station, located at 8,175 m from the
headwaters and near to the S12 sampling point. These data also show the evolution
of pH (from neutrality to nearly 4) and alkalinity (from 34 to 0 mg/L) in 2,000. Up
to now these conditions have been maintained.
Prior to the construction, the natural attenuation processes and the dilution pro-
duced by the tributaries (mainly La Retuerta, Mostruelo and the adit) were suffi-
cient to maintain a neutral pH in the stream and a population of brown trout. Some
characteristics of the tributaries of La Silva can be seen in the Table
1
.
Variation in Water Physicochemical Characteristics
Along La Silva
In the headwaters of La Silva, the ARD mix with superficial runoffs during rainy
periods and with small unpolluted streams which flow into the main bed. Both the
runoffs and the discharges increase the flow of the stream, producing a dilution of
the metallic content, a slight increase of pH and a precipitation that reduce espe-
cially Fe and Al contents. Main properties of the water samples of La Silva and its
tributaries in winter 2005-2006 are shown in Table
2
.
