High Volume Water Sampling
The Ohio River Valley Water Sanitation Commission (ORSANCO) is currently using a sampling technique called high-volume water sampling to quantify instream concentrations of dioxin, PCBs and chlordane in the Ohio River and its major tributaries. The US EPA water quality standard for dioxin is 0.013 parts per quadrillion (ppq).  This water quality standard and typical ambient water column concentrations are well below current analytical detection limits of 1-10 ppq. High-volume water sampling, however, is a new technique that for the first time allows for the direct measurement of instream dioxin concentrations at levels below the established water quality criterion.

The basic principle of high-volume water sampling is to filter a large volume of water in order collect a sufficient amount of dioxin, such that it can be detected by existing analytical methods.  This process is accomplished by first drawing the river water through glass fiber filters that separate and collect the suspended solids. The filtered water then passes through stainless steel columns filled with a hydrophobic resin that extracts the dioxin present in the dissolved phase.  The filters and columns are then analyzed separately to quantify dioxin levels in both the particulate and dissolved phases.