Occurrence and Fate of Pharmaceuticals and Illicit Drugs Under Water Scarcity. In: Sabater S, Barceló D, editors. Water Scarcity in the Mediterranean. Berlin: Springer Berlin Heidelberg; 2010. pp. 197-228. [DOI: 10.1007/698_2009_27]

Occurrence and modeling of pharmaceuticals on a sewage-impacted Mediterranean river and their dynamics under different hydrological conditions

The occurrence of 73 representative pharmacologically active compounds (PhACs) was assessed in a sewage-impacted section of the Llobregat River (NE Catalonia, Spain). This Mediterranean river is characterized by flow rate fluctuations strongly influenced by seasonal rainfall. River flow variations increase the potential environmental risk posed by organic micro-pollutants as their concentrations may increase substantially under low flow conditions. Little is known about the transport behavior of emerging contaminants in surface waters once they are discharged from waste water treatment plants (WWTP) into rivers. This research aimed to study the presence and fate of emerging contaminants under different hydrological conditions by sampling two different sites along the river in different seasons. The highest levels of pharmaceuticals were determined during cold and dry periods. The impact of the flow changes on the concentration of the pharmaceuticals in the river was assessed with the relative sensitive coefficients. Due to expected dilution effects, the response of pharmaceuticals to river flow was negative. Only in a few cases, positive relationships between drug concentrations and flow were detected, suggesting an important role of other hydrological phenomena like sediment re-suspension as well as the source of pollutants. To evaluate the role of other factors influencing PhAC concentrations, a plug-flow model was applied to obtain disappearance constants "k" for a set of selected compounds. Erythromycin presented k values of -0.15 h(-1) in both sites being the compound more efficiently removed from the water column. The k values for ibuprofen, furosemide, enrofloxacin, enalapril, acetaminophen, diclofenac and Ketoprofen were between -0.04 and -0.10 h(-1) showing less disappearance than erythromycin in the water column. However, other compounds presented k values<0.06, which suggested conservative behavior of these compounds in the water column. This study supports the reliability of the calculated k values for the disappearance of compounds in river waters.

Linking in-stream nutrient flux to land use and inter-annual hydrological variability at the watershed scale

The significance of nutrient inputs at the watershed scale is best expressed in terms of in-stream processes, compared to evaluating simple field measurements of nutrient inputs. Modeling tools are necessary to consider the complexity of river networks in the determination of the sources and processes by which nutrients are transported at the watershed scale. Mediterranean rivers are potentially vulnerable to climate change (decrease in precipitation and increase of extreme events), and identifying and quantifying nutrient pollution sources and their spatial distribution can improve water resource management at the watershed scale. We apply a hybrid process-based and statistical model (SPARROW, spatially referenced regression on watershed attributes) to a largely disturbed Mediterranean watershed in NE Spain in order to estimate the annual nitrate and phosphate loads reaching the drainage network. The model emphasized the contribution of in-stream processes in nutrient transport and retention, and the inter-annual (7 years) effects of hydrological variability on the export of nutrients from the landscape to water bodies. Although forest and grassland land cover types predominate, agricultural activities and human agglomerations were significant sources of nutrient enrichment. Nutrient flux apportionment was also linked to inter-annual hydrological variability. Exported nutrient load increased in the downstream direction and coincided with decreased in-stream nutrient removal, probably worsened by the significant chemical and geomorphological impairment found in the lower parts of the watershed.