Contributions of trace elements to the sea by small uncontaminated rivers: Effects of a water reservoir and a wastewater treatment plant.
Trace element contributions from small rivers to estuaries is an issue barely addressed in the literature. In this work, freshwater flowing into the Ria of Cedeira (NW Iberian Peninsula) was studied during a hydrological year through the input from three rivers, one considered uncontaminated (the Das-Mestas River), a second affected by urban treated wastewater discharges (the Condomiñas River), and the third containing a water reservoir for urban supply (the Forcadas River). With the objective of assessing the possible influence of human pressure, the annual yields for selected trace elements (Al, Fe, As, Cd, Co, Cr, Cu, Mn, Mo, Ni and Pb) were estimated and compared by normalizing by basin surface. Both dissolved and particulate transported elements were considered. After the data treatment and analysis it can be highlighted that: (i) the Das Mestas River is suitable to be included between the short European pristine baseline of small rivers, at least regarding the transported trace elements; (ii) natural enrichments were identified associated to the lithology of the basin in the Das-Mestas River (i.e. As) and in the Condomiñas River (i.e. Co, Cr and Ni); this fact highlights the importance of considering the local background for a proper assessment; (iii) the impoundment in the Forcadas River is related with a general decrease, even depletion, of the particulate and dissolved transported trace elements, except Mn; (iv) the discharge of sewage to the Condomiñas River is increasing the inputs to the ria of some trace elements in the particulate phase (i.e. Al, Cu and Pb). Both observed human-induced changes can be regarded as typical disturbances of trace element contributions from small rivers to estuaries.
Instituto de Investigaciones Marinas (CSIC), 36208, Vigo, Spain; Área de Geografía Física, Grupo GEAAT, Campus de Ourense (UVigo), 32004, Ourense, Spain.
Miguel Ángel
MÁ
Álvarez-Vázquez
Instituto de Investigaciones Marinas (CSIC), 36208, Vigo, Spain. Electronic address: prego@iim.csic.es.
Ricardo
R
Prego
Instituto Português do Mar e da Atmosfera (IPMA), 1495-006, Lisboa, Portugal.
Miguel
M
Caetano
Área de Geografía Física, Grupo GEAAT, Campus de Ourense (UVigo), 32004, Ourense, Spain.
Elena
E
De Uña-Álvarez
INTECMAR (Xunta de Galicia), 36611, Vilagarcía de Arousa, Spain.
Maryló
M
Doval
Instituto de Investigaciones Marinas (CSIC), 36208, Vigo, Spain.
Susana
S
Calvo
Marine and Environmental Research Center (CIIMAR), 4050-123, Porto, Portugal.
Carlos
C
Vale
D004784:Environmental Monitoring / Q000379:methods; D063366:Estuaries; D005618:Fresh Water / Q000032:analysis; D006801:Humans; D045483:Rivers / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry; D014131:Trace Elements / Q000032:analysis*; D014865:Waste Disposal, Fluid / Q000379:methods / Q000592:standards; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis
D012722:Sewage; D014131:Trace Elements; D062065:Wastewater; D014874:Water Pollutants, Chemical
Dam; Load; Metal; Ria; River; Spain; Wastewater