Determination of dicyclopentadiene and its derivatives as compounds causing odors in groundwater supplies

A study of organic pollutants causing odor events in the groundwater from the Lower Llobregat aquifer system has been conducted. This aquifer acts as water reserve of Barcelona (northeast Spain) when the quality of the raw water from the Llobregat River is low. Closed-loop stripping analysis (CLSA), purge-and-trap (P&T), sensory GC, and flavor profile analysis (FPA) have been used as analytical methodologies to identify the compounds responsible for the odor events. Industrial organochlorinated solvents-di-to hexa chlorinated saturated and unsaturated hydrocarbons-dicyclopentadiene (DCPD) and its derivatives 8-dihydroDCPD, tetrahydroDCPD, and adamantane (the trimer of DCPD) are among the most significant compounds identified in the groundwater. DCPD with a mean concentration of <1 mu g/L in almost all analyzed wells is the compound causing the odor incidents, regardless that some organochlorinated solvents such as 1,1,2-trichloroethane, trichloroethylene, and perchloroethylene might be even 2 or 3 orders of magnitude more concentrated than DCPD. The synthesis of dihydroDCPD was performed for confirmatory purposes. Trained and untrained panelists have established the threshold odor for this compound in the range of 10-25 ng/L. Although further research is needed, it is possible that an illegal landfill closed in the 1970s could be the origin of the different pollutants found.