69
place approximately between the late 1950s and the early 1970s. This is in accordance with previous results from the nearby Txipio salt marsh, where the beginning
of the environmental regeneration was established in the 1960s (Cearreta et al.
2002, 2011). The very high sedimentation rates (40 mm year
−1
) observed in Isuskiza
during DI 2 were responsible for the transformation of the tidal flat (lower part of
DI 2) into the regenerated salt marsh (DI 1). The sedimentary “dilution” caused by
these extremely elevated sedimentation rates could have been the reason why the
137
Cs and the Pb/Al peaks were not as obvious as in the previous Carasa core
(Fig. 2.12). Besides, the latter presented elevated metal concentrations very likely
unaffected by the high sedimentation rates occurred during the environmental
regeneration process.
2.6.3 Isla Salt Marsh in the Urdaibai Estuary
The Isla salt marsh is located in the middle-upper part of the Urdaibai estuary, where
in 2008 a 44-cm long core (two replicates) (coordinates X: 526,567.318, Y:
4,800,781.350, Z: 3.599 m above LOD) was obtained from an area covered by H.
portulacoides and Puccinellia maritima vegetation (Fig. 2.17).
Fig. 2.16 Core photograph, Al-normalized Pb distribution, and excess
210
Pb and
137
Cs activities
(Bq kg
−1 ) with depth (cm) in the Isuskiza salt-marsh core (Plentzia estuary). Depth intervals (DIs)
and the
137 Cs maximum are shown (Modified from Leorri et al. 2013)
2 Recent Agricultural Occupation and Environmental Regeneration of Salt...
place approximately between the late 1950s and the early 1970s. This is in accordance with previous results from the nearby Txipio salt marsh, where the beginning
of the environmental regeneration was established in the 1960s (Cearreta et al.
2002, 2011). The very high sedimentation rates (40 mm year
−1
) observed in Isuskiza
during DI 2 were responsible for the transformation of the tidal flat (lower part of
DI 2) into the regenerated salt marsh (DI 1). The sedimentary “dilution” caused by
these extremely elevated sedimentation rates could have been the reason why the
137
Cs and the Pb/Al peaks were not as obvious as in the previous Carasa core
(Fig. 2.12). Besides, the latter presented elevated metal concentrations very likely
unaffected by the high sedimentation rates occurred during the environmental
regeneration process.
2.6.3 Isla Salt Marsh in the Urdaibai Estuary
The Isla salt marsh is located in the middle-upper part of the Urdaibai estuary, where
in 2008 a 44-cm long core (two replicates) (coordinates X: 526,567.318, Y:
4,800,781.350, Z: 3.599 m above LOD) was obtained from an area covered by H.
portulacoides and Puccinellia maritima vegetation (Fig. 2.17).
Fig. 2.16 Core photograph, Al-normalized Pb distribution, and excess
210
Pb and
137
Cs activities
(Bq kg
−1 ) with depth (cm) in the Isuskiza salt-marsh core (Plentzia estuary). Depth intervals (DIs)
and the
137 Cs maximum are shown (Modified from Leorri et al. 2013)
2 Recent Agricultural Occupation and Environmental Regeneration of Salt...