2002 Progress Report: Methods Comparison Between Stripping Voltammetry and Plasma Emission Spectroscopy for Metals in Mobile Bay

EPA Grant Number: R827072C023
Subproject: this is subproject number 023 , established and managed by the Center Director under grant R827072
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Alabama Center For Estuarine Studies (ACES)
Center Director: Shipp, Robert L.
Title: Methods Comparison Between Stripping Voltammetry and Plasma Emission Spectroscopy for Metals in Mobile Bay
Investigators: Dorman, Scott C. , Isphording, Wayne
Institution: University of South Alabama
EPA Project Officer: Packard, Benjamin H
Project Period: July 1, 2000 through December 31, 2003
Project Period Covered by this Report: July 1, 2001 through December 31, 2002
RFA: Alabama Center For Estuarine Studies (ACES) (1999) RFA Text |  Recipients Lists
Research Category: Targeted Research

Objective:

The overall objective of this research project is to assess whether or not stripping voltammetry (SV) would yield comparable data as Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) for Mobile Bay water and sediment samples. SV equipment is substantially cheaper and far less complex to operate than ICP-AES equipment. A secondary objective of this investigation is to determine if the voltammetric method also might be used to identify the manner by which a specific metal is partitioned in naturally occurring sediment samples. This is particularly valuable to an environmental scientist because it provides information with respect to the actual bioavailability of the metal and its potential for remobilization. The final objective of this work is to accomplish field measurements with the voltammetric equipment and compare them to laboratory measurements.

Progress Summary:

The overall objective was accomplished in 2001. Metal standards, National Bureau of Standards whole rock samples, and 24 portioned samples from 12 sites in the bay were analyzed with SV and plasma emission spectroscopy. Seventy-six additional sites in Mobile Bay also were sampled to obtain complete Bay coverage. These were analyzed using plasma emission spectroscopy only. For each sample analyzed by SV, concentrations were calculated using calibration curves generated from standards. Metals analyzed in all samples include copper (Cu), lead (Pb), cadmium (Cd), and zinc. Preliminary analyses also were carried out for iron and bismuth. The results of these analyses are:

(1) Detection limits for both the SV and ICP-AES methods were found to be comparable. These limits are approximately in the upper parts-per-billion range when averaged over all elements analyzed. Therefore, it is possible to use the SV procedure to obtain data at the sub parts-per-million level

(2) Comparisons between the ICP and SV methods on whole sediment (unpartitioned) analyses were quite good for Cu, Pb, and Cd. Most sediments contained levels in the low ppm to upper ppb range for these elements. Table 1 lists results from one sampling site in the bay and gives a "feel" for the variation between the two methods. The two methods yield very similar values.

Table 1. Results From a Sampling Site in the Bay

 
Total Cu (ppm)
Total Pb (ppm)
Total Cd (ppm)
ICP-AES
24.90
21.00
0.67
SV
20.68
21.75
0.52

The secondary objective was partially accomplished during 2001 and 2002. Reasonable agreement between the two methods for results from the ion partitioning analyses was obtained. All of the values obtained for the different phases for Cu, Pb, and Cd were within the same order of magnitude. This was especially encouraging and confirmed that the SV procedure can be used (at least for certain metals) for these critical types of analyses.

Although a number of attempts were made to use the method to measure barium, no results were obtained. This metal does not appear to be amenable to the SV technique.

It was difficult to ascertain how sample treatment might have affected the results. One step in the ion partitioning procedure requires the addition of a strong oxidizing agent. This substance would be electroactive if present at the end of the chemical treatment and might lead to distorted results for the SV method. pH control was not carried out for any of the samples. Highly acidic samples typically show interference from proton reduction when using SV.

Whereas 20 metal species were analyzed for each sediment sampled by ICP-AES, only 4 were analyzed by SV. In general, this fact simply reflects the time necessary to carry out analyses using a “new” method (SV) as opposed to an established method (ICP-AES), but it also reflects the fact that SV is a much slower technique (requiring rinsing, cleaning, and blank conditioning between every sample run).

It is important to stress here that the SV procedure performed well beyond expectations. For the metals tested, for which no interferences were observed (copper, lead, and cadmium), the SV method produced sensitivities and detection limits that were comparable to systems costing five to eight times more. Complete results for these metals from the 12 sampling sites in the bay can be displayed graphically by maps and in tabular form. Of all the analyses performed, all differences were less than one order of magnitude in size and only two of the samples produced questionable values. These data clearly attest to the importance and potential of SV as a low-cost alternative for environmental analyses. Additional testing and evaluation will, hopefully, show that this technique can be applied to a wide range of elements and can consistently attain detection levels appropriate for most environmental applications.

Efforts to achieve the final objective were initiated in 2002. We attempted to take the voltammetry equipment into the field using a laptop computer. Unfortunately, the equipment as designed at present is cumbersome and requires AC power, which we attempted to provide using a generator. The noise resulting from the generator completely obscured any voltammetric signal.

Future Activities:

Future activities are to continue testing the stripping methodology for additional metals such as iron, chromium, nickel, manganese, and titanium. We also plan for field testing in natural waters using a laptop computer and a battery powered potentiostat. This should eliminate some of the problems previously encountered.

Journal Articles:

No journal articles submitted with this report: View all 2 publications for this subproject

Supplemental Keywords:

stripping voltammetry, SV, inductively coupled plasma-atomic emission spectroscopy, ICP-AES, metal bioavailability, plasma emission, Mobile Bay, Alabama, AL, Region 4, estuaries, estuarine research, estuarine waters, ecosystem protection, coastal ecosystems, coastal environments, water use, spectroscopy, ecosystem, ecology, ecological effects, environmental exposure, geographic area, environmental chemistry, chemistry, human modifications, land use., RFA, Scientific Discipline, ECOSYSTEMS, Water, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, estuarine research, Environmental Chemistry, Restoration, Aquatic Ecosystem, Aquatic Ecosystems, Environmental Monitoring, Ecology and Ecosystems, Environmental Engineering, Aquatic Ecosystem Restoration, coastal ecosystem, estuaries, ecosystem monitoring, plasma emission, shellfish, pollution markers, spectroscopic studies, coastal environments, estuarine waters, water quality

Relevant Websites:

http://www.southalabama.edu/aces/ Exit

Progress and Final Reports:

Original Abstract
  • 2001
  • 2003
  • Final

  • Main Center Abstract and Reports:

    R827072    Alabama Center For Estuarine Studies (ACES)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827072C001 Fluorescent Whitening Agents As Facile Pollution Markers In Shellfishing Waters
    R827072C002 Red Snapper Demographics on Artificial Reefs: The Effect of Nearest-Neighbor Dynamics
    R827072C003 Stabilization of Eroding Shorelines in Estuarine Wave Eliminates with Constructed Fringe Wetlands Incorporating Offshore Breakwaters
    R827072C004 Interaction Between Water Column Structure and Reproduction in Jellyfish Populations Of Mobile Bay (SGER)
    R827072C005 Effects of Variation in River Discharge and Wind-Driven Resuspension on Higher Trophic Levels in the Mobile Bay Ecosystem
    R827072C006 Results of Zooplankton Component
    R827072C007 Benthic Study Component
    R827072C008 A Preliminary Survey of Macroalgal and Aquatic Plant Distribution in the Mobile Tensaw Delta
    R827072C009 Fisheries-induced changes in the structure and function of shallow water "nursery habitats": an experimental assessment
    R827072C010 Effects Of Variation in River Discharge and Wind-Driven Resuspension on Lower Trophic Levels of the Mobile Bay Ecosystem
    R827072C011 Evaluation of Alabama Estuaries as Developmental Habitat for Juvenile Sea Turtles
    R827072C012 Effects of Salinity Stress on Natural and Anthropogenically-Derived Bacteria in Estuarine Environments
    R827072C013 The Role of Land-Use/Land-Cover and Sub-estuarine Ecosystem Nitrogen Cycling in the Regulation of Nitrogen Delivery to a River Dominated Estuary; Mobile Bay, Alabama
    R827072C014 Environmental Attitudes of Alabama Coastal Residents: Public Opinion Polls and Environmental Policy
    R827072C015 Synthesis and Characterization of an Electrochemical Peptide Nucleic Acid Probe
    R827072C016 Determinants of Small-Scale Variation in the Abundance of the Blue Crab Callinectes Sapidus
    R827072C017 Effects of Estrogen Pollution on the Reproductive Fitness of the Gulf Pipefish, Syngnathus scovelli
    R827072C019 A Model for Genetic Diversity Aquatic Insects of the Mobile/Tensaw River Delta
    R827072C020 Evaluating Trophic Processes as Indicators of Anthropogenic Eutrophication in Coastal Ecosystems: An Exploratory Analysis
    R827072C021 Effects of Anthropogenic Eutrophication on the Magnitude and Trophic Fate of Microphytobenthic Production in Estuaries
    R827072C022 Characteristics of Ship Waves and Wind Waves in Mobile Bay
    R827072C023 Methods Comparison Between Stripping Voltammetry and Plasma Emission Spectroscopy for Metals in Mobile Bay
    R827072C024 Changes in Water Conditions and Sedimentation Rates Associated With Construction of the Mobile Bay Causeway
    R827072C025 Cold-Induced Hibernation of Marine Vibrios in the Gulf of Mexico: A Study of Cell-Cell Communication and Dormancy in Vibrio vulnificus
    R827072C026 Holocene Sedimentary History of Weeks Bay, AL: Human and Natural Impacts on Deposition in a Gulf Coast Estuary
    R827072C027 Shelter Bottlenecks and Self-Regulation in Blue Crab Populations: Assessing the Roles of Nursery Habitats and Juvenile Interactions for Shelter Dependent Organisms
    R827072C028 Predicting Seagrass Survival in Nutrient Enriched Waters: Toward a New View of an Existing Paradigm
    R827072C029 DMSP and its Role as an Antioxidant in the Salt Marsh Macrophyte Spartina alterniflora
    R827072C030 A Preliminary Survey of Aerial and Ground-Dwelling Insects of the Mobile/Tensaw Delta
    R827072C031 Natural Biogeochemical Tags of Striped Mullet, Mugil cephalus, Estuarine Nursery Areas in the North Central Gulf of Mexico
    R827072C032 Resolution of Sedimentation Rates in Impacted Coastal Environments Using 137Cs and 210Pb Markers: Dog River and Fowl River Embayments
    R827072C033 Investigation of the Use of Pulse Amplitude Modulated (PAM) Fluorometry as an Indicator of Submerged Aquatic Vegetation Health in Mobile Bay
    R827072C034 Influence of Invasive Plant Species in Determining Diversity of Aquatic Vegetation in the Mobile-Tensaw Delta
    R827072C035 The Influence of Shallow Water Hydrodynamics on the Importance of Seagrass Detritus in Estuarine Food Webs
    R827072C036 Food Web Interactions, Spatial Subsidies and the Flow of Energy Between the Mobile Bay Delta and Offshore Waters: A SGER Proposal to the Alabama Center for Estuarine Studies
    R830651C001 Meteorological Modeling of Hurricanes and Coastal Interactions: A Stability Study For Vertical Pressure Levels
    R830651C002 Characterization of Glycoprotein Cues Used by the Parasitic Rhizocephalan Barnacle Loxothylacus texanus To Identify Its Blue Crab Host, Callinectes sapidus
    R830651C003 Survey of Diamondback Terrapin Populations in Alabama Estuaries
    R830651C004 An Assessment of Environmental Contaminant Levels in Water and Dragonfly Larvae Tissues from the Mobile/Tensaw Delta