MULTISPECIES TOXICITY ASSESSMENT OF COMPOST PRODUCED IN BIOREMEDIATION OF AN EXPLOSIVES-CONTAMINATED SEDIMENT

A multispecies terrestrial test system was used to assess the environm ental effectiveness of composting for bioremediation of explosives-con taminated soils. The assessment involved comparing biological response s, from the individual to the community level, in remediated and refer ence composts. A 6-month greenhouse study incorporated two soil invert ebrate species, three plant species and an associated symbiont, and th e naturally occurring complement of soil microorganisms. Measured para meters included growth and reproduction of earthworms and isopods; soi l mire diversity; soil lipid class composition as an indicator of soil microbial community structure; plant growth, photosynthesis, and repr oduction; and root nodulation and symbiotic N-2 fixation. Additional s hort-term toxicity rests of seed germination and earthworm survival we re performed to supplement the mesocosm data. Compost prepared from th e explosives-contaminated soil inhibited several aspects of plant grow th and physiology, but few adverse effects on soil invertebrates were detected. An initial lag in earthworm and isopod reproduction occurred in the reference compost, reflecting some inherent compost difference s not associated with contamination, and highlighting the importance a nd the difficulty of finding appropriate reference soils for assessing hazardous waste sites or remediation technologies. Nonetheless, the r esults from this study suggested some nonlethal effects from the conta minated-soil compost, primarily to plants. The mesocosm methodology us ed in this study can bridge the gap between traditional short-term tox icity testing and longer term field assessments, and provide informati on on ecological effects by explicitly including measurements of multi ple species across several levels of ecological organization.