Abstract: An improved method and apparatus for simultaneously monitoring the fluid flux and the target chemical mass fluxes in fluid flow systems is provided comprising the use of a body or shell that is inserted into the flow field. Inside or outside this body is a bundle of one or more permeable sorptive columns. The extremes of each column are hydraulically connected to the outside flow field around the body of the device through a pair of small openings in the body. The known non-uniform flow velocity distribution around the body of the invention causes a pressure difference between pairs of openings used to connect internal or external column units. A preferred shape of the body is a hydrofoil. Alternatively, instantaneous measurement of the fluid flux and contaminant composition is possible using pressure transducers and a chemical sensor.