Sediment quality evolution (2001-2011) in the Ebro River basin (Spain).

Spatio-temporal variations in sediment quality (20 sample sites) of the Ebro River basin between 2001 and 2011 have been assessed. The self-organizing map classified the sediment samples according to similarities in their chemical compositions. Its powerful visualization tools helped establish the main pollution contribution on each sample. Most of the samples showed low values of the mean-probable effect concentration quotient through time. However, six samples presented several quality issues related to some trace elements or polycyclic aromatic hydrocarbons. Finally, geoaccumulation index values calculated using estimates of background trace element concentrations suggested anthropogenic influences in more than half of the samples.

Potential risk assessment of trace elements and PAHs in sediment samples of the Ebro River basin (Spain).

This study was carried out in order to assess potential toxicity of hazardous pollutants (8 trace elements and 8 polycyclic aromatic hydrocarbons) in 20 sediment samples of the Ebro River basin (Spain) sampled in 2009. Mean-probable effect concentration quotient (m-PECQ) was found to range from 0.03 to 0.79. Two sites were classified as high priority sites in order to take future remediation actions due to their high m-PECQ value (>0.5). Worst-case scenario in equilibrium partitioning approach showed that acid volatile sulfide (AVS) content was greater than total trace element concentration in all samples. However, 4 sediments were classified as degraded due to the high AVS content measured (>50 mmol/kg). Principal component analysis classified the samples according to similar chemical characteristics and revealed that industrial activities are the main source of pollution of the basin.

Potential toxicity of polycyclic aromatic hydrocarbons and organochlorine pesticides in sediments from the Ebro River basin in Spain.

This study was carried out to estimate the potential toxicity of 8 Polycyclic Aromatic Hydrocarbons (PAHs) and 5 organochlorine pesticides (OCPs) in sediments in the Ebro River Basin (20 sampling points) according to different methodologies. Detection limit (DL) concentrations were used for compounds reported below the DL (worst-case scenario). The majority of PAH concentrations were found to be below their method detection limit. DL concentrations for OCPs were above the threshold values set by one guideline. In such cases, no toxicity assessment was carried out. It should be noted that no sediment is expected to cause adverse effects on the benthic species living in these sediments according to the methodologies applied.