Biosolids‐Amended Soils: Part I. Effect of Biosolids Application on Soil Quality and Ecotoxicity

Abstract

Investigations of potential risk from biosolids generally indicate that land application does not threaten human or ecosystem health, but questions continue to arise concerning the environmental effects of this practice. This research project was initiated to evaluate ecotoxicity resulting from the amendment of soils with biosolids from municipal wastewater treatment plants. Toxicity was evaluated using standard tests, including earthworm mortality, growth, and reproduction; seedling germination and root elongation; microbial respiration; and nematode mortality and reproduction. Nineteen municipal wastewater treatment plants were identified to participate in an initial screening of toxicity, and five were chosen for a more detailed evaluation. In addition, two soils with historically high applications of high‐metal biosolids were evaluated. Contaminants examined were zinc, copper, nickel, chromium, arsenic, cadmium, lead, and coplanar polychlorinated biphenyls (PCBs). Single applications had no effect on soil metal concentrations. Coplanar PCBs were not detectable in any of the soils or biosolids. All target organisms were sensitive to reference toxicants. Limited toxicity was observed in a small number of the amended soils, but no patterns emerged. Approximately one‐half of the negative effects of biosolids on bioindicators could be attributed to routine properties, such as slight depression of pH and/or elevated salinity. None of the accumulated metal concentrations were excessive, and most would not be considered elevated. These observations suggest that current regulations for application of biosolids to soils are providing adequate ecosystem protection.

Biosolids‐Amended Soils: Part II. Chemical Lability as a Measure of Contaminant Bioaccessability

“…For all metals, except arsenic, extractable concentrations in sites 20 and 21 were 10 times those for the other sites. This shows the sensitivity of the extractants, particularly in conjunction with the previous observations that biological indicators were not affected by the metals in the amended soils ( Banks et al, 2006 ).…”

“…The research strategy was to extract all experimental soil samples in the study (amended, long‐term amended, laboratory‐amended, and controls, as described by Banks et al [2006] ). The extracts were analyzed for critical U.S. EPA 503 metals, including zinc, nickel, lead, cadmium, arsenic, copper, and chromium ( U.S. EPA, 2004 ).…”

“…Wastewater treatment plant biosolids and associated soils were tested for heavy metal lability and toxicity using four bioassays (seed germination, microbial respiration, earthworms, and nemotodes). For the complete study design, please review the companion paper, Banks et al (2006) .…”

Toxicity and bioaccumulation of biosolids‐borne triclosan in terrestrial organisms

“…After 28 d, earthworms were removed, counted, washed, and weighed. The earthworms were allowed to depurate for 24 h in petri dishes lined with moistened filter paper [24] and were subsequently frozen until analyses. Birds and worm-eating animals feed on nondepurated earthworms, but depuration allows earthworms to excrete TCScontaminated soil or organic matter remaining in the gut.…”

Emergence and survival of blue grama with biosolids under greenhouse conditions

“…Zubillaga and Lavado (2006) also observed a germination delay and a root growth decrease of ryegrass (Lolium perenne L.) with biosolids water extract under laboratory conditions, attributing this effect to its high electrical conductivity (4.3 dS m À1 ). Banks et al (2006) also observed reductions in lettuce (Lactuca sativa L.) seedling emergence and root growth and millet (Panicum miliaceum L.) seedling emergence under controlled conditions attributed to the high electrical conductivity (4.6 dS m À1 ) in a biosolids-amended soil.…”