Large spill of mining wastes in Portelo stream: impacts on ecosystem integrity and on angling potential
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abstract
Streams located at Montesinho Natural Park
(NE Portugal) have high potential for brown trout (Salmo
trutta) angling. However, in this territory there are several
abandoned mine sites. Therefore, the continuous drainage
of fine grained tailings can be particularly problematic
due to arsenic, copper, aluminium and zinc. However,
until now no significant disturbance was detected in water
quality and in biota. Nevertheless, there has never been
such a large spill of mining wastes as that occurred in
January 2010. As a consequence of intense precipitation,
several millions of cubic meters of wastes were spilled
into Portelo stream. The large amount of wastes covered
the riverbed with a layer of mud reaching more than half a
meter in areas close to the mine. Both riparian and agricultural areas were also affected by the sediments
from mine. Wastes were spilled downstream by several
strong rain events. Thus, the objective of the present
research was to evaluate the impact of this event on
ecosystem integrity and ultimately on angling potential.
To achieve the proposed objective the water from four
sampling points along the affected stream was sampled
for the following metals- AI, Mn, Co, Cu, Ni, Cd and As.
Concomitantly, macroinvertebrate and fish assemblages
were also assessed. Temporal differences between
stations were not detected. On contrary spatial differences
were found. As expected, the stations located near the
1nine showed the highest levels of contamination and
disturbance. Consequently, in these stations no
macroinvertebrates and fish were found during the period
of study.
Streams located at Montesinho Natural Park (NE Portugal) have high potential for
brown trout (Salmo trutta) angling . However, in this territory there are severa! abandoned mine
sites. Therefore, the continuous drainage of fine grained tailings can be particularly problematic
due to arsenic, copper, aluminium and zinc. However, until now no significant disturbance was
detected in water quality and in biota. Nevertheless, there has never been such a large spill of
mining wastes as that occurred in January 201 O. As a consequence of intense precipitation,
severa! millions of cubic meters of wastes were spilled into Portelo stream. The large amount of
wastes covered the riverbed with a layer of mud reaching more than half a meter in areas close to
the mine. Both riparian and agricultura! areas were also affected by the sediments from mine.
Wastes were spilled downstream by severa! strong rain events. Thus, the objective of the present
research was to evaluate the impact of this event on ecosystem integrity and ultimately on angling
potential. To achieve the proposed objective the water from four sampling points along the
affected stream was sampled for the following metais - AI , Mn, Co, Cu , Ni, Cd and As.
Concomitantly, macroinvertebrate and fish assemblages were also assessed. Temporal
differences between stations were not detected. On contrary spatial differences were found. As
expected, the stations located near the mine showed the highest leveis of contamination and
disturbance. Consequently, in these stations no macroinvertebrates and fish were found during
the period of study.
