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Endocrine disrupting chemicals (EDCs) are detected in environmental matrices such as surface water, wastewater, groundwater, and drinking water in the ng/L range. For environmental sediments, values in the range of ng/g and even lower are reported. These almost omnipresent low concentrations of estrogens are of major concern, in particular as sorption parameters derived from laboratory investigations tend to imply the absence of estrogens in the natural environment. Very few studies consider the fate and transport of estrogens in column tests at environmentally relevant concentrations, including metabolite formation and sorption. Also, the effect of input concentration on hormone degradation is unclear. To close this gap, the estrogens 17s-estradiol (E2), estrone (E1), and the conjugated estrogen estrone-sulfate (E1-3S) were each injected into saturated, packed soil columns as pulses with subsequent analysis of soil and aqueous samples. The transformation pathway E2 to E1 and subsequently to E1-3S was verified in sandy clay loam soil from Bet Dagan, Israel. Furthermore, it was shown that (i) E2 is rapidly degraded in soil and transformed in soil to E1; (ii) E1 is subject to strong retardation by sorption; and (iii) E1-3S behaves almost conservatively and shows the lowest sorption and transformation potential.

A promising approach to abiotically dechlorinate a variety of chlorinated organic contaminants under reducing conditions is to utilize porphyrins or other tetrapyrrole macrocycles as electron transfer mediators/shuttles for catalyzing their reduction. In this study, various experimental approaches were used to elucidate the role of porphyrin core metals in the reductive dechlorination of tetrachloroethylene (PCE). The importance of specific core metals for the reactivity of a porphyrin and its mediated reaction mechanisms was demonstrated by inserting different metals into metallo tetrakis (N-methyl-4-4 pyridiniumyl) porphyrin (TMPyP). No PCE dechlorination was observed when the free-base (i.e., no core metal) and iron core metal forms of TMPyP were utilized. When using nickel or cobalt TMPyP, reductive dechlorination of PCE occurred but appeared to follow different pathways for the two metals based on product analyses. Physical (e.g., steric) considerations suggest that direct contact between a porphyrin core metal and PCE may be limited and therefore that the entire metalloporphyrin molecule should be viewed as a functional system in which the organic macrocycle has an active part in reductive dechlorination reactions. This view is supported by the fact that slight changes in the functional groups on a porphyrin macrocycle, particularly those far removed from the core metal itself, greatly affected the reactivity and mechanism of the porphyrin. Solution conditions also had a major effect on porphyrin reactivities, to the extent that a nonreactive metalloporphyrin could be activated merely by adjusting the pH of the solution or by adding a small amount of cosolvent. The collective results of this study suggest that fine tuning of naturally occurring metalloporphyrin complexes and/or their environments can enhance the catalyzed detoxification of chlorinated contaminants in many natural and engineered environmental systems.