Biological test method for measuring terrestrial plants exposed to contaminants in soil: abstract

Abstract

This document provides detailed procedures, conditions, and guidance for preparing for and conducting a biological test for measuring soil toxicity using terrestrial plants. Twelve species options are provided and include: alfalfa (Medicago sativa), barley (Hordeum vulgare), blue grama grass (Bouteloua gracilis), carrot (Daucus carota), cucumber (Cucumis sativus), durum wheat (Triticum durum), lettuce (Lactuca sativa), northern wheatgrass (Elymus lanceolatus), radish (Raphanus sativus), red clover (Trifolium pratense?), red fescue (Festuca rubra),or tomato ( Lycopersicon esculentum). The test is a 14- or 21-day test for effects on seedling emergence and plant growth (measured as shoot and root length and shoot and roo t dry mass). The method is conducted as a static (i.e., no renewal) test, using one or more samples of contaminated or potentially contaminated soil or one or more concentrations of chemical(s) or chemical product(s) spiked in negative control (or other) soil. Water is added to the test vessels to hydrate soils for the duration of the test.

The test is conducted at a mean temperature of 24 ± 3 °C in 1-L polypropylene test vessels containing a measured wet weight equivalent to a volume of ~500 mL of test soil. Five or ten seeds (i.e., number of seeds per test vessel is species-specific) are placed into each replicate test vessel. This test uses 5 replicated test vessels/treatment for a single-concentration test, and 3 6 replicated test vessels/treatment for a multi-concentration test. The options for test design in a multi-concentration test include an equal number of replicates per treatment (i.e., 4) or unequal replicates per treatment (i.e., six per treatment for each negative and other control; four replicates for each of the lowest 6 test concentrations; and three replicates for each of the highest five test concentrations). Following a 14- or 21-day exposure (i.e., test duration is species-specific), the number of emerged seedlings in each replicate and each treatment is determined, and the mean percent emergence for each treatment is then compared. Additionally, the shoot and root lengths and the shoot and root dry weights of individual plants surviving in each replicate are determined, and the treatment means compared.

General or universal conditions and procedures are outlined for test preparation and performance. Additional conditions and procedures are stipulated that are specific to the intended use of each test. The biological test method described herein is suitable for measuring and assessing the toxicity of samples of field-collected soil, biosolids, sludge, or similar particulate material; or of natural or artificial soil spiked (mixed) in the laboratory with test chemical(s) or chemical product(s). Instructions and requirements are included on test facilities, sample collection, handling and storing samples, seed source, seed storage and handling, preparing soil or spiked-soil mixtures and initiating tests, specific test conditions, appropriate observations and measurements, endpoints and methods of calculation, and the use of a reference toxicant.