Nematodes as ecological indicators of soil ecosystem restoration at E&P sites (2 Year Project)
EPA Grant Number: X83-2428-01Investigators:
Kerry L. Sublette, Sarkeys Professor of Environmental Engineering, University of Tulsa, 600 S. College Ave., Tulsa, OK 74104, (918)631-3085 Phone, (918)631-3268 Fax, kerry-sublette@utulsa.edu
Tim Todd, Kansas State University, Department of Plant Pathology, 4024 Throckmorton Plant Sciences Center, Manhattan, KS 66506, (785)532-6176 Phone, (785)532-5692 Fax, nema@plantpath.ksu.edu
Kathleen E. Duncan, Energy Center, Department of Botany and Microbiology, University of Oklahoma, 770 Van Vleet Oval, Norman, OK 73019, (405) 325-6927 Phone, (405) 325-3180 Fax, Kathleen.E.Duncan-1@ou.edu
Institutions: University of Tulsa; Kansas State University, University of Oklahoma
EPA Project Officer: Bala Krishnan
Project Period: 1-10-06 through 1-9-08
Project Amount: $194,486
Research Category: Soil ecosystem restoration
Description: We propose to investigate nematode population dynamics in a number of E&P sites in various stages of remediation and restoration in various climates to develop a more robust dataset. This data will help facilitate the acceptance of nematode testing by state and federal regulatory agencies as a measure of soil ecosystem status.
Objective: The objectives of this project are to generate a data set that can be used by the scientific community, the petroleum industry, and regulators to determine the efficacy of using nematode community analysis as an ecological indicator in E&P settings. Specifically we will investigate nematode population dynamics at a number of E&P sites in various stages of remediation and restoration in various climates to develop a robust dataset. The American Petroleum Institute will assist us in gaining access to E&P sites for sampling and/or provide soil samples and analytical data for impacted sites and appropriate controls. Based on soil chemistry (TPH, nutrients, pH), soil microbiology (PLFA), nematode numbers and diversity, and vegetation cover and species diversity these sites will be classified in terms of the status of the impacted sites in terms of soil health compared to controls. At each site we will verify that the nematode analysis tells the same story as the other more costly and time-consuming analyses. These data will also allow correlation of nematode community characteristics to various kinds of disturbances in an E&P setting. A second important goal of this project is the dissemination of this information. If this project is successful we intend to incorporate this information in soil remediation workshops for producers and state regulatory agencies through IPEC (subject to IAB and SAC approval) and prepare interpretive tools to be distributed by IPEC through the OCC and AOGC district offices and IPEC’s web site. The technology transfer deliverable from this project will be draft curricula and tools to be submitted to the IPEC Joint IAB/SAC Technology Transfer Committee for evaluation.
Approach: A total of twelve (12) field sites will be chosen in consultation with API and API member companies to be representative of three climates zones in terms of temperature and rainfall, original contaminant (crude oil or primarily brine), and perceived stage of restoration. Three stages of restoration will be considered: unimpacted control, early restoration stage, and advanced restoration stage. The early restoration phase will be defined as remediated but less than 25 % revegetated (in terms of percent cover). Crude oil sites will be considered remediated if the TPH concentration is below 1%. Brine sites will be considered remediated if the chloride concentration is less than 1000 mg/kg (by IPEC Soil Salt Analysis Kit). The advanced stage of restoration will be characterized by the same remediation criteria plus >75% revegetated.
In each climate zone four sites will be chosen, two crude oil sites and two brine sites along with nearby unimpacted controls. For each pair of like impacted sites one will be in an early restoration phase and the other will be in an advanced restoration phase. Tentatively the three climate zones will be Louisiana, Oklahoma, and Colorado/Wyoming. For each impacted site there will be an associated unimpacted control for a total of 24 sampling sites.
The status of each test site in terms of soil health will be evaluated through evaluation of soil chemistry, soil texture, soil microbiology, and plant community structure. Each impacted site and its companion control will be sampled twice, in spring and fall within a 12-month period for nutrients (total N, total C, NH4+, NO3-, plant available P, pH), phospholipid fatty acids (PLFA, total microbial density, diversity, and community structure), TPH (total and fractions), brine components, plant data aboveground biomass, percent coverage, and species diversity), and nematodes (identification to family level, tropic group assignment, c-p classification). Nematode indices as described earlier will be calculated from the nematode data. Sites will be sampled only once for soil texture, as that property is not expected to change over the course of the study.
All impacted and control sites will be 3600 ft2 or larger. Samples will be taken with reference to a permanent grid of 4 nodes set in a square approximately 30 ft by 30 ft in order to account for some of the spatial variation in contamination or other factors. Edge effects will be lessened by requiring a minimum of 15 ft from the edge of the contaminated area to the node. Because soil nutrients, especially nitrate and ammonium, are notorious for their spatial heterogeneity, three samples for nutrient analysis (not composited) will be taken within a 2 ft radius of each node, giving a total of 12 samples per site per sampling event for the nutrient analysis. In addition approximately 2 kg of soil will be removed from within the 2 ft radius around each individual node, composited in the field in a clean bucket (one bucket per node, a total of 4 buckets/site/sampling event), then aliquoted to provide samples for nematode analysis, PLFA, brine components, and TPH (four composite samples per site). Only one composite sample from a brine-impacted site will be taken at each sampling event for TPH analysis. Likewise only one composite sample will be taken from an oil-impacted site at each sampling event for brine component analysis. Lastly, only one composite sample for TPH and brine component analysis will be taken from unimpacted controls at each sampling event.
Several types of statistical analysis will be performed: degree of association among the variables (Pearson correlation coefficients), source of the variation within and between sites (ANOVA), the relationship of the variables to one another (linear regression, other regression analyses), similarities among the individual sites (cluster analysis), and ordination plots (principal components analysis) to examine the distribution of sites plotted in a 2-D space in which the axes are a smaller set of mutually independent variables that explain the pattern of correlations within the set of variables.
Expected Results: The results of these analyses will define the distribution of values for each parameter in unimpacted, early restoration stage, and advanced restoration stage soil ecosystems for two contaminants (oil and brine) in three distinct climatic zones. The conditions of soil nutrient pools will be determined and PLFA analysis will yield information on the concentrations and status of the decomposers which make up the bottom of the food web. Plant community analysis will reveal the status of the producers at the top of the food web. Both of these groups should be more or less responsive to chemical disturbances which will be characterized by the TPH and brine component analyses and the history of the site. We propose that the nematode community in the middle of the food web will reflect the status of both the producers and the decomposers, e.g. show a high degree of correlation with these other parameters, and that we will find significant differences among the three types of sites (unimpacted, early stage, advanced stage) in some of the nematode indices that will allow us to classify other sites as to their stage of restoration using these indices.
Key Words: Nematode, soil ecosystem restoration, oil spill, brine spill, revegetation