Release of polycyclic aromatic compounds into a Mediterranean creek (Catalonia, NE Spain) after a forest fire.

Wildfires produce polycyclic aromatic compounds (PACs), among which polycyclic aromatic hydrocarbons (PAHs) are of environmental concern. After a fire affecting a Mediterranean creek, we studied the distribution and short-term permanence of PACs and of 16 priority PAH pollutants in the aquatic environment. PACs were traced through absorbance and fluorescence emissions and organic carbon concentrations. PAHs were analysed by gas chromatography. High TOC/DOC concentrations and fluorescence/absorbance values reflected abnormal inputs of fire-induced aromatic compounds. Their concentrations decreased gradually but showed sporadic peaks after precipitation. Fifteen months later, values still surpassed background levels. Initially concentrations of individual and total PAH species of the dissolved, particulate and sediment phases were increased. Then they fluctuated with new PAH inputs related with runoff, leaching and soil erosion following precipitation events. All PAH concentrations approached background levels 15 months after the fire, and never reached values of toxicological concern. However, some bioaccumulation may have occurred.

Trace metal concentration, antioxidant enzyme activities and susceptibility to oxidative stress in the tricoptera larvae Hydropsyche exocellata from the Llobregat river basin (NE Spain).

Caddisfly larvae of Hydropsyche exocellata were sampled from seven locations receiving increasing levels of urban and industrial waste water discharges along the Llobregat river system (NE Spain) during spring and summer 2003. Locations were selected to include aquatic communities in poor and good ecological state according to measured physicochemical water parameters and the analysis of benthic macroinvertebtrate communities. Whole body residues of selected metals (Fe, Al, Zn, Cu, Co, Ni, Pb, Cd) were determined in conjunction with antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase activity of GST, GSTPX), a phase II enzyme (glutathione-S-transferase, GST) and lipid peroxide levels measured as thiobarbituric reactive species (TBARs) with the aim of investigating whether resident macroinvertebrate benthic species were responsive to changes in water quality. Caddisfly larvae inhabiting those rivers were exposed to increasing levels of metal pollution. Enhanced activities of two (CAT and GST) out of the four tested enzymes, coupled with increased levels of TBARs, indicated increasing levels of stress in the studied species towards downstream reaches or locations near industrial and urban areas. These results indicate that combination of chemical and biochemical responses can be used to assess and diagnose pollution in high stressed river ecosystems.