The influence of natural vs anthropogenic factors on trace metal(loid) levels in the Mussel Watch programme: Two decades of monitoring in the Spanish Mediterranean sea

The spatial distribution and temporal trends of trace metals (i.e. Cd, Cu, Hg, Pb Zn) a metalloid As) along the Spanish Mediterranean coast from 1993 to 2013 are presented with new estimation their background levels monitored using wild mussels. Over 20 years period, yearly mussel monitoring was undertaken rigorous field sampling protocol 3 pooled samples strategy (3 x n = 80, 8 mussels in 3.0 3.9 size categories at each site), obtained pre-spawning period (May–June) minimize biological factors seasonal variability, which is fundamental element international programme. Spatial characterized every 5 were determined 11 locations. main aims present long term study evaluate environmental status different coastal locations regarding metal follow evolution these over time after implementation regulatory measures. Regarding distribution, highest values for Hg found close known highly anthopogenic cities or shipyard areas. However, As Zn did not strictly this pattern, showing natural increased concentrations Levantine Balearic Strait Gibraltar-Alboran Sea demarcations respectively. These distributions associated conjunction two geological formation inputs (Massif Central France Iberian Pyritic Belt Spain) oceanographic conditions adjacent area. In case trends, decreased significantly most stations, confirming effectiveness measures prohibitions established under European legislation. Concentrations above thresholds human consumption only 12–14% With information study, we estimate propose Background Assesment Criteria (BAC) as threshold criterion: 1.62 mg/kg d.w. 8.75 0.202 2.83 Pb. Exceptions should exist Zn, there be demarcation, due geological, hydrological peculiarities coast. For Levantine-Balearic proposed 117 200 Zn., whereas they 27.5 As, 471 Zn. This work demonstrates vital importance defining metal(loid)s regional subregional level because, areas affected by anthropogenic causes have high result processes, would avoid risk constantly surpassing directives.