The Microbial and Transformations of Arsenic in Anoxic WatersEPA Grant Number: R823222
Title: The Microbial and Transformations of Arsenic in Anoxic Waters
Investigators: Morel, Francois M.
Institution: Princeton University
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1995 through September 30, 1998
Project Amount: $356,082
RFA: Exploratory Research - Environmental Biology (1995) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Health , Ecosystems
The goal of this project is to understand the role of microorganisms in arsenic cycling in contaminated freshwater systems. Arsenic is an important pollutant, one whose toxicity and potential carcinogenicity are responsible for the "high ranking" of several superfund sites. Yet for all its importance, we are still relatively ignorant of the processes that control arsenic chemistry and mobility in the environment. In particular, we know little of the processes responsible for the dissolution and precipitation of arsenic in anoxic waters and sediments where arsenic is most often found. The specific goals of this proposal are to elucidate two particular pathways that are important for the mobility of arsenic in anoxic systems: 1) the reduction (and dissolution) of As(V) to As(III); and 2) the precipitation of arsenic-sulfides.
The project is based on two related hypotheses that posit that bacteria are responsible for arsenic transformations in the environment. The first hypothesis is that arsenate (AsO43-) is used as an electron acceptor by some bacteria (dissimilatory As(V) reduction) and thus reduced to the more mobile arsenite (AsO33-) form in anoxic waters. According to the second hypothesis, some of these bacteria also catalyze the precipitation of arsenic sulfides, chiefly orpiment (As2S3). Both of these hypotheses are at variance with current wisdom since arsenic's toxicity makes it a seemingly improbable bacterial substrate and orpiment is not considered a typical sedimentary constituent.
The results of this project will further our understanding of the processes that promote or hinder the mobility of arsenic in contaminated environments. They will thus allow us to develop better models for predicting the fate of arsenic and perform more accurate impact/exposure assessments.