Effect of flood events on transport of suspended sediments, organic matter and particulate metals in a forest watershed in the Basque Country (Northern Spain)

• Published in: The Science of the total environment Vol. 569-570; pp. 784 - 797
• Main Authors: Peraza-Castro, M., Sauvage, S., Sánchez-Pérez, J.M., Ruiz-Romera, E.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.11.2016
• Subjects: Environmental Monitoring; Flood event; Floods; Forest catchment; Geologic Sediments - analysis; Metals - analysis; Organic matter; Particulate Matter - analysis; Rivers - chemistry; Spain; Suspended particulate matter; Trace metals; Water Pollutants, Chemical - analysis; ANE, Spain; Forest catchment; Organic matter; Flood event; Suspended particulate matter; Trace metals
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2016.06.203

An understanding of the processes controlling sediment, organic matter and metal export is critical to assessing and anticipating risk situations in water systems. Concentrations of suspended particulate matter (SPM), dissolved (DOC) and particulate (POC) organic carbon and metals (Cu, Ni, Pb, Cr, Zn, Mn, Fe) in dissolved and particulate phases were monitored in a forest watershed in the Basque Country (Northern Spain) (31.5km2) over three hydrological years (2009–2012), to evaluate the effect of flood events on the transport of these materials. Good regression was found between SPM and particulate metal concentration, making it possible to compute the load during the twenty five flood events that occurred during the study period at an annual scale. Particulate metals were exported in the following order: Fe>Mn>Zn>Cr>Pb>Cu>Ni. Annual mean loads of SPM, DOC and POC were estimated at 2267t, 104t and 57t, respectively, and the load (kg) of particulate metals at 76 (Ni), 83 (Cu), 135 (Pb), 256 (Cr), 532 (Zn), 1783 (Mn) and 95170 (Fe). Flood events constituted 91%-SPM, 65%-DOC, 71%-POC, 80%-Cu, 85%-Ni, 72%-Pb, 84%-Cr, 74%-Zn, 87%-Mn and 88%-Fe of total load exported during the three years studied. Flood events were classified into three categories according to their capacity for transporting organic carbon and particulate metals. High intensity flood events are those with high transport capacity of SPM, organic carbon and particulate metals. Most of the SPM, DOC, POC and particulate metal load was exported by this type of flood event, which contributed 59% of SPM, 45% of organic carbon and 54% of metals. •Fluxes of SPM, DOC, POC and particulate metal during flood events and at annual scale were estimated.•From good regressions between SPM and particulate metal concentrationobtained during floods, it is possible to calculate the metal annual load.•A methodology to classify floods according to their intensity and export capability of particulate metal was established.•High intensity-flood events are the largest contributors to the export of SPM, organic carbon and particulate metal load.•Variability of particulate metal load is related with suspended particulate matter (SPM), precipitation and discharge.