Polycyclic aromatic hydrocarbons (PAHs), a group of the hydrophobic organic pollutants (HOPs), are mainly generated from incomplete combustion and commonly found in the urban runoff. PAHs have been targeted to control due to their prevalence and toxicity. Researches have estimated that urban runoff results in 14-36% total PAHs loading into aquatic ecosystems. However, most studies for PAHs in urban runoff have only studied the particulate phase and during the rain events. The pollution of HOPs, such as PAHs, in the dissolved phase of urban runoff has not been clarified.  Dissolved organic matter (DOM) is ubiquitous in the aquatic environment and with different characteristics. DOM has the ability to associate with HOPs in urban runoff. The association between HOPs and DOM affects the bioavailability of HOPs and their resulting toxicity. In other words, when DOM associates with HOPs to become a bound form, DOM-HOPs, in the dissolved phase, is not toxic to biota. In aquatic environment, knowing true free concentration of HOPs is necessary to effectively determine the bioavailable quantity of HOPs and minimize environmental hazards.  This study used the PAH, perylene, as a probe for HOPs. Partition coefficients between DOM and perylene (KDOM) were measured by the fluorescence quenching method. Characteristics of DOM were measured for: 1) size distribution 2) polarity and 3) UV and fluorescent chemical functionality. The results showed that DOM characteristics show seasonal variations and there is a significant difference between dry weather runoff and storm events. Thus the relationship between DOM and HOPs in equilibrium with DOM-HOPs needs definition on a seasonal basis. Specific UV Absorbance (SUVA) of bulk samples and UV254 within DOM in the 10k-5k molecular weight size fraction appear to primarily affect association between DOM and PAHs. The results can help understand the distribution of HOPs in the urban runoff in the dissolved phase and potential toxicity of free PAHs. The procedure developed in this study can help optimize the Toxicity Identification Evaluation (TIE) process required in the National Pollutant Discharge Elimination System (NPDES) permit. Relating the toxic free PAHs from the non-toxic bound DOM-PAH complex is important for the regulatory agency when considering the fate and transport for regulating HOPs in the receiving water bodies, such as Total Maximum Daily Load and Water Quality Objectives.

Understanding how hydrophobic organic pollutants distribute in urban runoff by using perylene as a probe

253rd National Meeting (2017)

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