Grantee Research Project Results
1998 Progress Report: Role of Reduced Sulfur Species in Promoting the Transformation of Triazines in Estuaries and Salt Marshes
EPA Grant Number: R826269Title: Role of Reduced Sulfur Species in Promoting the Transformation of Triazines in Estuaries and Salt Marshes
Investigators: Roberts, A. Lynn , Salmun, H.
Institution: The Johns Hopkins University
EPA Project Officer: Chung, Serena
Project Period: February 1, 1998 through January 31, 2001 (Extended to January 31, 2002)
Project Period Covered by this Report: February 1, 1998 through January 31, 1999
Project Amount: $304,163
RFA: Exploratory Research - Environmental Chemistry (1997) RFA Text | Recipients Lists
Research Category: Water , Air , Safer Chemicals , Land and Waste Management
Objective:
The objectives of this research are to: (1) determine the rates of abiotic nucleophilic aromatic substitution reactions of triazines (and related species) with inorganic reduced sulfur nucleophiles; (2) examine the ability of triazines to bind covalently to natural organic matter (NOM); and (3) examine the potential impact of reduced sulfur species on the fate of azines in a typical estuary and salt marsh through development of box models.Progress Summary:
This report covers the first year of a 3-year project. Objective 1 is approximately 40 percent completed; Objective 3 is approximately 35 percent completed; and initial experiments have been conducted pertaining to Objective 2.
Initial laboratory studies pertaining to the kinetics of reaction of atrazine and other azines with polysulfides (Sn2-) and bisulfide (HS-) have been conducted in "clean" systems at 25?C. Products (consistent with nucleophilic displacement of chlorine by sulfur species) were identified by methylation with CH3I, followed by GC/MS analysis. Transformation of atrazine also was followed in the laboratory in a natural sulfidic water sample spiked with this herbicide in the laboratory. Filter-sterilized controls suggested that the principal removal process in this natural water was abiotic. Transformation rates and products were compared with those anticipated on the basis of the "clean" laboratory studies. Experiments also have been conducted with "model" NOM compounds containing thiolate moieties.
Development of a "box model" for atrazine fate in the upper Chesapeake Bay (as a typical estuary) is currently under way. Atrazine mass loads into the upper Bay have been estimated for fluvial input, groundwater input, and atmospheric deposition. The dominant mass input appears to be fluvial input, followed by groundwater flow, and finally atmospheric deposition. These inputs have been incorporated into the box model MASAS (Modeling of Anthropogenic Substances in Aquatic Systems) to simulate the fate of atrazine. Physical parameters of the Bay and various approaches for describing vertical mixing have been applied in developing the model, which has been calibrated on the basis of salinity profiles. Three chemical reactions have been incorporated for atrazine: photolysis, hydrolysis, and abiotic reaction with reduced sulfur species in the sediment porewaters. Preliminary results indicate measured atrazine concentrations in the Bay are significantly higher than predicted values, suggesting that significant sources of atrazine in the northern section of the Bay remain unaccounted for.
Future Activities:
Future work will focus on: (1) determining the dependence of pseudo-first order rate constants for polysulfide reaction with azines on pH and total polysulfide concentration; (2) measuring rates of reaction of azines in additional natural sulfidic water samples obtained from local salt marshes; (3) assessing the possibility that covalently bonded azine-NOM species could form through spectroscopic examination of products of 13C-labeled atrazine reaction with NOM and model NOM compounds; (4) investigation of additional sources of atrazine input into the upper Chesapeake Bay; and (5) development of a "box model" of atrazine fate in a typical salt marsh.Journal Articles:
No journal articles submitted with this report: View all 23 publications for this projectSupplemental Keywords:
chloro-s-triazine herbicides, fiber-reactive dyes, agrochemicals., Air, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Waste, Fate & Transport, Chemistry, Ecology, Biology, Engineering, Chemistry, & Physics, coastal ecosytems, salt marshes, Triazines, water quality, kinetic models, estuaries, sulfur, halogenated hydrocarbons, fate and transport, toxicology, agriculture, waste treatmentProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.