Occurrence of Emerging Contaminant 4-Nonylphenol in Stream Water of a Mixed Use Small Watershed: Impact of Urban Storm Water Runoff.

4-Nonlyphenol (4-NP), an endocrine disruptor, is metabolite of nonylphenol polyethoxylate, which is widely used in many industrial and consumer products as surfactant, emulsifier, and stabilizer. 4-NP has been detected in various environmental samples. Up to date, it is believed that wastewater treatment plants are the sources of 4-NP in the environment. The occurrence of 4-NP in the Stroubles Creek of a small mixed use watershed in Blacksburg, VA was investigated between May 2012 to December 2013. Sediment and water samples were collected weekly and every 15 min during three storm events in the summer of 2013. The Levels of 4-NP in the sediment of the Stroubles Creek, which does not have wastewater treatment plant outfalls, were similar or even higher than that in the sediment of large scale WWTPs outfalls. The levels of 4-NP was higher in the portion of the creek that is heavily impacted by urban activity than areas impacted by agriculture. However, although lower than what was detected in the areas impacted by urban and agriculture, significant levels of 4-NP were detected in the sediment and water in the natural forest area that is 6 miles downstream. Our study suggested: 1) collective urban storm water runoff is the major source of 4-NP in the watershed; 2) the retention pond of urban storm water runoff is not effective in reducing 4-NP accumulated in the fine particle size fraction (<0.1 mm) than that in larger size fraction (> 0.5 mm) of the pond sediment; and 3) stream sediment transport and re-suspension releases 4-NP during rain events, resulting occurrence of 4-NP downstream in the pristine environment and possibly in the receiving river.