Title: Metal and nanoparticle occurrence in biosolids - amended soils Authors
|Yang, Yu -|
|Wang, Yifei -|
|Westerhoff, Paul -|
|Hristovski, Kiril -|
|Johnson, Mari-Vaughn -|
Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 24, 2014
Publication Date: N/A
Interpretive Summary: Growing urban populations present a serious waste disposal issue for city services. Recycling of municipal biosolids by land application can support agricultural production while also providing a cost-effective waste disposal plan. There is concern, however, about possible effects of metals entering the environment through land application programs. This study looks at whether metals are present as nano-materials in biosolids-applied soils. We found that land application of biosolids increased soil concentrations of metals regulated by the Environmental Protection Agency (chromium, copper, cadmium, lead, zinc, silver) as well as several non-toxic metals (yttrium, zirconium, molybdenum, indium, tin, antimony, niobium, hafnium, tantalum, tungsten, gold). Metals related to nanomaterials (silver, zinc, titanium) built up in soils, and were identified using a novel method of transmission electron microscopy.
Technical Abstract: Approximately 40% of the 7 million dry tons of municipal biosolids produced annually in the US are applied to soils for disposal nutrient enrichment. The goal of this study is to prospect agricultural sites with long-term biosolids application for a suite of metals, some of which are regulated and others potentially attributable to engineered nanomaterials (ENMs). Sampling occurred at a USDA- Agriculture Research Service site with differing biosolid application rates which has been operated for over a decade. Depth profiles of metals were developed for soils without biosolids amendment or different rates of application (10 to 30 dry tons per year). Regulated metals of known toxicity accumulated in the upper soils (top 30 cm). Some metals exhibit depth profiles with higher concentrations in 0-30 cm than in 70-100 cm, indicating their low mobility after entering the soils. Metal content in soils are greater with higher or longer biosolid application rate. The averaged concentrations of Y, In, Te, Ir, Pt, Au were around or below 1 mg/kg, while Li, Cr, Cu, Pb, Zr, Zn and Ti had concentrations above 100 mg/kg. The other elements including Be, Co, As, Se, Nb, Mo, Ag, Cd, Sn, Sb, Ce, Hf, W were in the range of 1 – 100 mg/kg. Titanium containing nanoparticles between 50 nm to 250 nm were identified on soil by transmission electron microcopy (TEM) coupled with energy dispersive d-ray analysis (EDX).