Article pubs.acs.org/est
Short-Term Effect of the Soil Amendments Activated Carbon, Biochar, and Ferric Oxyhydroxide on Bacteria and Invertebrates Sarah E. Hale,† John Jensen,‡ Lena Jakob,§,○ Patryk Oleszczuk,∥ Thomas Hartnik,§,◆ Thomas Henriksen,⊥ Gudny Okkenhaug,†,# Vegard Martinsen,# and Gerard Cornelissen*,†,#,∇ †
Department of Environmental Engineering, Norwegian Geotechnical Institute (NGI), P.O. Box 3930, Ullevål Stadion, N-0806 Oslo, Norway ‡ Department of Bioscience, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark § Soil and Environment Division, Norwegian Institute for Agricultural and Environmental Research, Bioforsk, Fredrik A. Dahls vei 20, N-1432 Ås, Norway ∥ Faculty of Chemistry, Department of Environmental Chemistry, Maria Curie-Skłodowska University, 3 Maria Curie-Skłodowska Square, 20-031 Lublin, Poland ⊥ Lindum Ressurs og Gjenvinning AS, Lerpeveien 155, N-3036 Drammen, Norway # Department of Plant and Environmental Sciences (UMB), University of Life Sciences, 5003 Ås, Norway ∇ Department of Applied Environmental Sciences (ITM), Stockholm University, 10691 Stockholm, Sweden S Supporting Information *
ABSTRACT: The aim of the present study was to evaluate the secondary ecotoxicological effects of soil amendment materials that can be added to contaminated soils in order to sequester harmful pollutants. To this end, a nonpolluted agricultural soil was amended with 0.5, 2, and 5% of the following four amendments: powder activated carbon (PAC), granular activated carbon, corn stover biochar, and ferric oxyhydroxide powder, which have previously been proven to sequester pollutants in soil. The resulting immediate effects (i.e., without aging the mixtures before carrying out tests) on the springtail Folsomia candida, the earthworm species Aporectodea caliginosa and Eisenia fetida, the marine bacteria Vibrio f ischeri, a suite of ten prokaryotic species, and a eukaryote (the yeast species Pichia anomalia) were investigated. Reproduction of F. candida was significantly increased compared to the unamended soil when 2% biochar was added to it. None of the treatments caused a negative effect on reproduction. All amendments had a deleterious effect on the growth of A. caliginosa when compared to the unamended soil, except the 0.5% amendment of biochar. In avoidance tests, E. fetida preferred biochar compared to all other amendments including the unamended soil. All amendments reduced the inhibition of luminescence to V. f ischeri, i.e., were beneficial for the bacteria, with PAC showing the greatest improvement. The effects of the amendments on the suite of prokaryotic species and the eukaryote were variable, but overall the 2% biochar dose provided the most frequent positive effect on growth. It is concluded that the four soil amendments had variable but never strongly deleterious effects on the bacteria and invertebrates studied here during the respective recommended experimental test periods.
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INTRODUCTION
remediate contaminated soils and sediments has previously been carried out in both the laboratory and the field.1 Successful experiments have demonstrated vast reductions in aqueous polycyclic aromatic hydrocarbon (PAH), polychlorobiphenyl (PCB), and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) concentrations and the uptake of these compounds by passive sampling devices and benthic organ-
The remediation of contaminated soil and sediment is traditionally carried out by digging/dredging and disposing of the material in a landfill, in situ solidification/stabilization, and placement of impervious cover or cap. However, such methods may not meet risk reduction remediation goals for human health and ecosystem protection and may actually exacerbate the problem. Adding strongly sorbing amendment materials to soils is an increasingly popular method for the chemical stabilization of soils polluted with either organic contaminants or heavy metals. Using activated carbon (AC) amendment in order to sequester hydrophobic organic chemicals and therefore © 2013 American Chemical Society
Received: Revised: Accepted: Published: 8674
March 4, 2013 June 21, 2013 June 26, 2013 June 26, 2013 dx.doi.org/10.1021/es400917g | Environ. Sci. Technol. 2013, 47, 8674−8683
Environmental Science & Technology
Article
isms.2−7 The use of biochar, a material produced during the combustion of biomass, to remediate contaminated soils has also begun to attract attention. The lower cost of biochar8 combined with its positive climate effects9 have prompted investigations of the adsorption capacity of various biochars for organic pollutants.10−12 Thus far, field implementations have not been carried out. However, successful remediation of heavy metal and metalloid contaminated soil13−17 and tailing materials18,19 has been accomplished with the addition of Febased amendments (e.g., zerovalent iron (Fe0), ferrihydrite, goethite, hematite, and deferrisation sludge). It has been shown that different iron oxyhydroxides can sorb both heavy metals (i.e., Pb, Cu and Zn)20,21 and oxyanions (e.g., Sb and As).22−24 While these amendment materials may have a large sorption affinity for organic and inorganic pollutants and thus provide chemical benefits when added to polluted sediments and soils, it is important to consider the effects that the amendment materials themselves may have on the native ecosystem. A suite of studies have investigated the response of resident biota following the amendment of AC to contaminated sediments, drawing variable conclusions in relation to survival, growth, and lipid content. Detrimental effects were not observed for the polychaete Neanthes arenaceodentata,6,25 the clam Macoma balthica,7 and the earthworm Lumbriculus variegatus26 following AC amendment in laboratory experiments. These results were replicated in the field when the composition, richness, and diversity of the resident macrobenthic community was considered.27 By contrast, Jonker et al28 observed a large reduction in the lipid content of the aquatic oligochaete Limnodrilus sp. following the amendment of coal and charcoal particles to sediment in the laboratory, and the egestion rate, growth, and reproduction of L. variegatus decreased following AC amendment.29 Toxic effects have also been observed for L. variegatus, Daphnia magna, and Corophium volutator in AC amended sediment.30 In addition, field results have also shown detrimental effects on the benthic community following AC amendment, either alone or mixed with sand, especially on the number of individuals.31 The effect of amending AC to soils on earthworms and microbes has similarly demonstrated a mixed picture.13,15,32,33 Earthworms lost weight when AC was added to a PCB contaminated soil13 and a dioxin and furan polluted soil,32 likely because they were not fed during the study or that the soil and amendment had a poor nutritional quality. However, in a trinitrotoluene impacted soil amended with AC, the amendment resulted in a greater number of microorganisms compared to the unamended soil.33 This was also substantiated in a study that showed total microbial counts and respiration were higher in AC amended compared to unamended soil, 3 years after amendment.15 Studies focusing on earthworms and microbes have also been carried out on biochar amended soil. In avoidance tests carried out with earthworms, no clear pattern related to the preference or avoidance of biochar has been noted.34−38 Biochar can be ingested by earthworms,36 although no conclusive evidence has been presented to implicate this as the reason for a preference of biochar amended soil. The habitat for microbes can be positively affected by the presence of biochar,39 as respiration rates40 and the abundance of microbes can increase.41 However, bacterial diversity has also been observed to be lower when burned and unburned forest soils were amended with oak and grass biochar.34 In addition, biochar-treated soils showed shifts in the relative abundance and diversity of key taxa upon the addition of biochar, with a loss of microbial diversity
in all soils treated with oak- and grass-derived biochar.42 Studies of the effect of iron-based amendments on soil biota or plants are scarce.20 The aim of the current study was to investigate the secondary effects (i.e., not bioavailability/pollutant related) of four adsorbent amendments on invertebrates and bacteria. Clean agricultural soil was amended with powder activated carbon (PAC), granular activated carbon (GAC), biochar from corn stover, and ferric oxyhydroxide powder. These amendments have previously improved the quality of soils and sediments by sequestering organic18,31 and inorganic pollutants.24 The effects on the springtail Folsomia candida, the earthworms Eisenia fetida and Aporectodea caliginosa, the marine bacteria Vibrio fischeri, a suite of ten prokaryotic species, and a eukaryote (the yeast species Pichia anomalia) were investigated using the unamended soil and amended soil immediately after amendment (i.e., without any prior soil aging). This is the first comparative study where the toxicity of organic and inorganic soil amendments to invertebrates and bacteria has been investigated simultaneously.
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MATERIALS AND METHODS Soil and Amendments. The soil was an uncontaminated loam taken from the Ap horizon of an agricultural soil (Norderås, UTM 32-N6617041/E599609) and has been used in one of our previous studies.43 An uncontaminated soil was chosen as the aim of the study was to investigate toxic effects arising from the amendments themselves, not from contaminants already contained in a polluted soil. Using a contaminated soil and considering toxic effects would have introduced the complicating factor of pollutant sequestration by the amendment materials themselves which then could reduce toxicity. The amendments tested were powder and granular activated carbon (PAC and GAC), biochar, and ferric oxyhydroxide powder. The two types of AC were both produced from bituminous coal and purchased from Silcarbon (Kirchhundem, Germany). The ACs were used in our earlier soil18 and sediment31 remediation field and laboratory experiments.43 The biochar was produced from corn stover residues at 600 °C using a slow pyrolysis method in a continuous flow gas unit for a residence time of 20 min. The biochar has been used in a field study to investigate the growth of maize when applied at doses between 0 and 30 t/ha.44 The ferric oxyhydroxide powder
