A passive dosimeter is to be designed for use in obtaining monthly average concentrations of atrazine in a stretch of river. Typical concentrations range from 10 to 50 g/L. Atrazine, a herbicide commonly found in runoff from agricultural lands. The dosimeter will use activated carbon as the adsorbent. To maximize diffusion rate, the diffusion barrier adjacent to the activated carbon is to be a polycarbonate membrane filter that has pores with a nominal diameter of 1 ?m and a total surface area of pores that is estimated as 0.635 cm^2. The length of the diffusion channels is the thickness of the membrane (10 ?m). Tests have shown that atrazine adsorbs very strongly on activated carbon such that 2 g of activated carbon should be sufficient to ensure that the concentration remains close to zero at the surface of the activated carbon. Given the percent recovery of adsorbed atrazine (using a solvent extraction), the volume of solvent and the sensitivity of the analytical method (a gas chromatographic procedure), the minimum mass of atrazine accumulated by the activated carbon that is capable of detection is 10 ?g.

a). determine whether this dosimeter design will be adequate to detect atrazine given the sampling time and the typical concentration range mentioned above.

b). Discuss the limitations of this monitoring approach.