Development of Relevant Ecological Screening Criteria (RESC) for Petroleum H ydrocarbon-Contaminated Exploration and Production Sites

EPA Grant Number: R827015-01-0
Title: Development of Relevant Ecological Screening Criteria (RESC) for Petroleum Hydrocarbon-Contaminated Exploration and Production Sites
Investigators: Roman Lanno, Will Focht, Anne Cross
Institutions: Oklahoma State University
EPA Project Officer: Bala Krishnan
Project Period: July 1, 2000 to June 30, 2001 (N/C Ext. to December 31, 2001)
Project Amount: $117,463
Research Category: Ecorisk assessment

Description:

Quarterly Progress Report Covering the Period from July-September 2000:

The major accomplishments of this quarter were:

1. Collection of soil samples from the contaminated sites at the Tallgrass Prairie
2. Preparation of soils for toxicity testing and total petroleum hydrocarbon (TPH) analysis
3. Conducting toxicity tests with soil invertebrates

1. Develop relevant ecological screening criteria (RESCs) for petrochemical-contaminated sites on the Nature Conservancy's Tall Grass Prairie Preserve, Pawhuska, OK, and use them in a baseline ecological risk assessment. RESCs would be generated for a number of relevant ecological receptors including soil invertebrates, plants, and soil microbes.
2. Incorporate evolving research initiatives in soil toxicology (e.g., chemical measures of the bioavailability of petrochemicals in soil) into the testing by comparing total petroleum hydrocarbon (TPH) and bioavailable (BPH) fractions in exposure analysis.
3. Conduct soil toxicity tests with organisms for which no codified toxicity tests are available (e.g., enchytraeids, isopods, Collembola) in order to expand the database available for conducting ecological risk assessments of contaminated soils.
4. Assemble data from various researchers who have investigated the response of tall grass prairie ecosystems to petroleum spills and include it in the ecological risk assessment. This would include data on microbial communities and responses to petrochemicals; information on soil micro-and macrofauna (e.g., nematodes, earthworms, soil arthropods; effects on plants; and chemical analysis data of soils. Actual field data on exposure and effects for earthworms, soil arthropods, and plants will be collected.

Research this quarter involved the collection of hydrocarbon- contaminated soils from the Tallgrass Prairie Preserve in Pawhuska, OK. Soil collection was completed in May 2000, prior to the actual commencement of the grant since it was decided that a complete summer of weathering might reduce hydrocarbon concentrations below levels that would result in potential toxic effects. TPH analysis suggested a concentration gradient from 13,243 mg/kg to below detection limits in the spill areas. Six soils were selected to represent this concentration gradient and were used in toxicity tests with soil invertebrates. Initial invertebrate toxicity tests were conducted with an earthworm Eisenia fetida and a Collembola Folsomia candida. No mortality of earthworms was observed, but cocoon production decreased significantly with increased TPH levels. No apparent effect of TPH on survival of the F. candida was observed. This may be due to the ecological niche occupied by F. candida as an organism that lives in the upper layers (organic horizon) of soil rather than an organism that actually burrows into the soil. Due to these results, we will determine whether tests with the isopod Armadillidium vulgare are warranted since this organism is epigeic and lives almost entirely on the upper surface of the soil and not actually in the surficial soil as F. candida does.

Plans for the current quarter include completion of the toxicity test with enchytraeids, preparation for toxicity tests with plant species, begin assembling existing data on the toxicity of hydrocarbons in soils, enumeration of bacteria in soil, and further chemical analysis of soils.