2001 Progress Report: Social Impact Assessment of Human Exposure to Mercury Related to Land Use and Physicochemical Settings in the Alabama-Mobile River System

EPA Grant Number: R827168
Title: Social Impact Assessment of Human Exposure to Mercury Related to Land Use and Physicochemical Settings in the Alabama-Mobile River System
Investigators: Bonzongo, Jean-Claude J. , Lyons, W. Berry , Roden, Eric E. , Ward, Milton G. , Bryan, C. H. , Chaubey, Indrajeet
Current Investigators: Bonzongo, Jean-Claude J. , Warner, Kimberly A. , Lyons, W. Berry , Bryan, Hobson C. , Roden, Eric E. , Ward, Milton G. , Chaubey, Indrajeet
Institution: The University of Alabama at Birmingham , University of Florida , University of Arkansas - Little Rock , The Ohio State University
Current Institution: The University of Alabama at Birmingham , The Ohio State University , University of Arkansas - Little Rock , University of Florida
EPA Project Officer: Chung, Serena
Project Period: December 21, 1998 through December 20, 2001
Project Period Covered by this Report: December 21, 2000 through December 20, 2001
Project Amount: $804,534
RFA: Water and Watersheds (1998) RFA Text |  Recipients Lists
Research Category: Water , Watersheds

Objective:

In the past decade, mercury (Hg) concentrations above levels that could pose human health risks have been measured in predatory fish from many rivers and reservoirs in the Southeastern region of the United States. This region, specifically the Coastal Plain portion, is particularly vulnerable to Hg contamination in aquatic food chains, due to the coexistence of both natural and human imposed conditions, which favor the production/accumulation of methyl-Hg. This research project hypothesizes that: (1) nutrient loading from certain land-use activities and increased sedimentation above water impoundments develop conditions favorable for methyl-Hg production; (2) increased sulfate loading from mining operations result in increased methyl-Hg production; (3) abundant wetlands within the Mobile-Alabama River Basin (MARB) contribute to methyl-Hg loads downstream and in fish; and (4) fish tissue levels of methyl-Hg are related to water levels and net rates of methyl-Hg production in sediments. The objectives of this study are to: (1) determine levels and speciation of Hg in different compartments of various aquatic systems in the MARB; (2) investigate the linkage between land use types or the presence of wetlands and microbial processes associated with methyl-Hg production; (3) use Geographic Information Systems (GIS) to represent spatially arranged data and ultimately to predict Hg levels in fish; and (4) use a participatory approach to environmental decisionmaking to ameliorate conflict, and achieve an effective public understanding and support for Hg policy. As part of this approach, a social and economic impact-assessment is being conducted of potential remedial alternatives as a basis for recommendations.

Progress Summary:

In the past decade, mercury (Hg) concentrations above levels that could pose human health risks have been measured in predatory fish from many rivers and reservoirs in the Southeastern region of the United States. This region, specifically the Coastal Plain portion, is particularly vulnerable to Hg contamination in aquatic food chains, due to the coexistence of both natural and human imposed conditions, which favor the production/accumulation of methyl-Hg. This research project hypothesizes that: (1) nutrient loading from certain land-use activities and increased sedimentation above water impoundments develop conditions favorable for methyl-Hg production; (2) increased sulfate loading from mining operations result in increased methyl-Hg production; (3) abundant wetlands within the Mobile-Alabama River Basin (MARB) contribute to methyl-Hg loads downstream and in fish; and (4) fish tissue levels of methyl-Hg are related to water levels and net rates of methyl-Hg production in sediments. The objectives of this study are to: (1) determine levels and speciation of Hg in different compartments of various aquatic systems in the MARB; (2) investigate the linkage between land use types or the presence of wetlands and microbial processes associated with methyl-Hg production; (3) use Geographic Information Systems (GIS) to represent spatially arranged data and ultimately to predict Hg levels in fish; and (4) use a participatory approach to environmental decisionmaking to ameliorate conflict, and achieve an effective public understanding and support for Hg policy. As part of this approach, a social and economic impact-assessment is being conducted of potential remedial alternatives as a basis for recommendations.

Progress Summary/Accomplishments: In the original proposal, an extensive survey based on the collection of water, sediment, and fish samples in waterway sections affected by different land use types was planned for Year 1. Unfortunately, this did not occur until summer of Year 2. This past summer, another set of samples was collected during the intensive study (Phase II of the project). Currently, laboratory determinations of all physical and chemical parameters have been completed, except for methyl-Hg in sediment samples of Phase I, for which the analysis is still taking place.

Current results can be summarized as follows. Total iron (FeT) and total reduced sulfur (TRS) concentrations in sediments ranged from 0.1-149 and 26-686 mol.g-1 dry sediment, respectively. There were positive relationships between sediment FeT concentrations and sediment porosity, TRS, and organic matter content. Total-Hg and methyl-Hg concentrations in water were low and ranged from 0.2-3.8 and 0.02-3.8ng L-1, respectively. Regarding biological tissues, a total of 96 fish samples (largemouth bass) were taken from 51 out of 52 sites from the Phase 1 survey. At least two fish were sampled at 43 sites, and only one fish at the remaining 8 sites. The concentrations of Hg in these 96 fish spanned over 3 orders of magnitude, from 0.02 to 2.8 ppm (mg Kg-1 ww). Mean and median concentrations were 0.45 and 0.32 ppm, respectively. Approximately 12 percent of the fish had Hg concentrations greater than or equal to 1 ppm, the level at which consumption advisories are posted in Alabama. Average fish Hg concentrations were greater than or equal to 0.5 ppm at 21 (41 percent) of the sites. Coefficients of variation in fish Hg concentrations from any one site were usually high, averaging 68 percent. In many cases, Hg concentration was higher in the smaller of two fish.

Based on the results of the Phase I field survey and the updated land use analyses, it was decided to focus on one pool (Demopolis, AL) containing four sites with different impact types: (1) dam; (2) agricultural; (3) wetland; and (4) open river. In these sites, water, sediment, and fish samples were collected; and laboratory experiments were conducted to determine the different environmental factors controlling methyl-Hg production/decomposition, hence its accumulation in biota.

Biogeochemical analyses and experiments using radio-labeled chemicals revealed high rates of sulfate reduction (SR) at the agricultural site in both sediment depths, SR in the lower depth of the wetland site, and iron reduction as the dominant TEAP at the dam, open river, and surface sediment horizon of the wetland site. In general, microbial Hg transformation was active in the surface sediment interval, but not the lower depth, at most sites. Consistent with the preliminary experimental results from experiments conducted in the first year, Hg methylation, but not methyl-Hg demethylation, was suppressed under iron reducing conditions in the sandy sediments at the open river site and in the oxidized fine-grained lower depth sediments of the dam site. However, both Hg methylation and methyl-Hg demethylation were observed under iron-reducing conditions in the surficial sediments of the dam site. This is the first observation of Hg methylation under iron-reducing conditions. Both methylation and demethylation proceeded in the reduced, fine-grained, sulfate-reducing surficial sediments of the agricultural site, but not in sediments from the lower depth. Unfortunately, Hg transformation experimental samples were compromised at the wetland site and data could not be used to determine potential rates of methylation and demethylation. Depending on funds availability, experiments at the wetland site would probably be repeated to complete the study of different impact factors.

Concentrations of Hg (127-393ng.g-1) and MeHg (0.13-2ng.g-1) in non-amended sediments increased in the following order of impacts: open river less than dam less than agriculture less than wetland. The percentage of methyl-Hg produced in the sediments was a positive function of sediment iron, organic matter, and porosity. That is, a higher proportion of methyl-Hg is produced in fine-grained, organic-rich sediments, consistent with the hypotheses and most published data.

Despite differences in net production of methyl-Hg in sediments from the different sites, the average concentration of Hg in fish tissues among the four sites was consistently rather high. The average concentrations of Hg (ppm?1SD) in the six fish from each site were: open river: 0.77?0.45; dam: 0.85?0.35; agriculture: 0.88?0.35; wetland: 1.7?0.80. Comparing fish Hg concentrations among sites, only the wetland site was found to be significantly different from the other three sites (Student Newman Keuls test, p less than 0.05). All sites had at least one fish with Hg concentration greater than 1ppm, and two fish from the wetland site had concentrations in excess of 2.5ppm.

Data Base Development and GIS.Information has been developed and updated about the watersheds within which the samples were taken. Specifically, new (1990s) and more accurate delineations have been obtained for watershed boundaries, hydrography, and land use/land cover (LULC), as well as a series of physical measurements that better describe the geomorphology of the basin terrains. With this new data, LULC analyses of study watersheds also have been developed and updated, as well as portions of each study basin that lie adjacent to, and upstream of, sample sites. LULC information was created for buffers of 50, 100, 300 m adjacent to stream channels, as well as for various radial buffer distances surrounding fish collection sites, and for upstream distances from stream mouths (up to 1 mile). All of this updated information was designed for use in correlative analyses, and was included in a database (ACCESS). Additional analyses have been completed comparing LULC changes that have occurred within the study basins from 1970 to 1990. Also, all data available have been added to the database developed last year. This database has been linked to updated land use and other watershed spatial characteristics in an ArcView GIS environment. The database has reports to display query results that can be used by researchers and stakeholders.

Finally, multiple regression models have been developed that relate land use in a watershed to in-stream nitrogen and phosphorus concentrations. Proportion of each land use type within the watershed, and within a buffer zone of 30, 150, 300, and 500 m around the stream channel was derived using ArcView GIS. Various sets of regression models were developed to predict the in-stream N and P concentration as a function of the proportion of a land use type within the watershed, and within buffer zones of various widths. These models can be used to identify watershed areas that should be managed to protect water quality and to predict changes in water quality as a function of quantity and spatial distribution of land use changes.

Social Assessment. A critical component of the social science segment of this research has been the integration of stakeholder concerns into the research process via consultation and, in the case of anglers, via collection of data. The rationale has been that this strategy encourages stakeholders to contribute and exchange information with the project team members. This approach has achieved demonstrable results in facilitating the project design and implementation. Stakeholders also have contributed meaningful input towards identifying the issues that will frame the assessment of social impacts. These approaches underscore the operating principle that all biophysical research has social implications, and that the earlier that stakeholders are meaningfully engaged in the process; the more timely the biophysical outcomes can be presented and incorporated into the decisionmaking process for appropriate response to human exposure to methyl mercury.

During this past year, a series of meetings were concluded between the research team and distinct interest groups. (Collection of data by tournament anglers was completed during the second year of the project.) These meetings included a presentation of the research project purpose and goals, and explanation of the hypotheses regarding anticipated elevated mercury levels related to land use. They served to introduce the project design, explain the project approach and intent, and provide a platform for presenting project findings during subsequent meetings.

Future Activities:

Following the completion of field and laboratory work, the upcoming data analysis in Year 4 will lead to the preparation of manuscripts for publication in peer reviewed literature. Given the scope of the study, a large audience will be targeted by publishing at least one "synthesis-paper" on the overall findings of the project. The journal Bioscience is considered as a possible option. In addition to the above paper, more technical manuscripts from each component of the project will be submitted to different technical journals. At least five papers are anticipated from this study.

During this "fourth" year, the methyl-Hg analysis will be completed in sediment samples and perform more robust statistical analyses of the data. Also, analysis and comparison of historical and government agency data will continue on Hg concentration in Alabama largemouth bass with our data to check for spatial trends.

Regarding GIS, plans for the no-cost extension year are to incorporate final project data into the database, and continue to refine the operation of the database within the GIS environment (i.e., refining spatial query methods). The goal is to make the use of the process as user-friendly as possible for researchers and stakeholders.

So far, data have been obtained profiling the social and economic dimensions of sport and commercial fisheries in the Lower Tombigbee River and Mobile River Delta. These will be used to draw inferences about social and economic impacts of study findings. What remains is reporting findings back to stakeholders and soliciting their reaction and advice concerning ultimate policy implications of the research and projecting social and economic impacts.

Journal Articles:

No journal articles submitted with this report: View all 26 publications for this project

Supplemental Keywords:

southeastern U.S., Alabama, watersheds, mercury, biogeochemistry, GIS, social science, and policy, RFA, Scientific Discipline, Geographic Area, Water, Water & Watershed, Ecology, Hydrology, Environmental Chemistry, State, Chemistry, Wet Weather Flows, Ecological Risk Assessment, Agronomy, Biology, Watersheds, Mercury, aquatic, fate and transport, aquatic ecosystem, anthropogenic stress, watershed, food chain, agricultural discharges, social impact assessment, runoff, urban runoff, Alabama (AL), citizen perceptions, soils, mercury cycling, aquatic degradation, biogeochemical cycling, methylmercury, watershed influences, methylation, GIS, water quality, marine environment, public policy, bioaccumulation, land management, methylization of mercury

Progress and Final Reports:

Original Abstract
  • 1999 Progress Report
  • 2000
  • Final Report