Do earthworms impact metal mobility and availability in soil? – A review (original) (raw)
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A review of studies performed to assess metal uptake by earthworms
Earthworms perform a number of essential functions in soil; the impacts of metals on earthworms are often investigated. In this review we consider the range of earthworm species, types of soil and forms of metal for which metal uptake and accumulation have been studied, the design of these experiments and the quantitative relationships that have been derived to predict earthworm metal body burden. We conclude that there is a need for more studies on earthworm species other than Eisenia fetida in order to apply the large existing database on this earthworm to other, soil dwelling species. To aid comparisons between studies agreement is needed on standard protocols that define exposure and depuration periods and the parameters, such as soil solution composition, soil chemical and physical properties to be measured. It is recommended that more field or terrestrial model ecosystem studies using real contaminated soil rather than metal-amended artificial soils are performed.
Impacts of epigeic, anecic and endogeic earthworms on metal and metalloid mobility and availability
J. Environ. Monit., 2010
The introduction of earthworms into soils contaminated with metals and metalloids has been suggested to aid restoration practices. Eisenia veneta (epigeic), Lumbricus terrestris (anecic) and Allolobophora chlorotica (endogeic) earthworms were cultivated in columns containing 900 g soil with 1130, 345, 113 and 131 mg kg−1 of As, Cu, Pb and Zn, respectively, for up to 112 days, in parallel with earthworm-free columns. Leachate was produced by pouring water on the soil surface to saturate the soil and generate downflow. Ryegrass was grown on the top of columns to assess metal uptake into biota. Different ecological groups affected metals in the same way by increasing concentrations and free ion activities in leachate, but anecic L. terrestris had the greatest effect by increasing leachate concentrations of As by 267%, Cu by 393%, Pb by 190%, and Zn by 429% compared to earthworm-free columns. Ryegrass grown in earthworm-bearing soil accumulated more metal and the soil microbial community exhibited greater stress. Results are consistent with earthworm enhanced degradation of organic matter leading to release of organically bound elements. The degradation of organic matter also releases organic acids which decrease the soil pH. The earthworms do not appear to carry out a unique process, but increase the rate of a process that is already occurring. The impact of earthworms on metal mobility and availability should therefore be considered when inoculating earthworms into contaminated soils as new pathways to receptors may be created or the flow of metals and metalloids to receptors may be elevated.
Environmental Pollution, 2013
Due to diffuse atmospheric fallouts of process particles enriched by metals and metalloids, polluted soils concern large areas at the global scale. Useful tools to assess ecotoxicity induced by these polluted soils are therefore needed. Earthworms are currently used as biotest, however the influence of specie and earthworm behaviour, soil characteristics are poorly highlighted. Our aim was therefore to assess the toxicity of various polluted soils with process particles enriches by metals and metalloids (Pb, Cd, Cu, Zn, As and Sb) collected from a lead recycling facility on two earthworm species belonging to different ecological types and thus likely to have contrasted behavioural responses (Eiseina hortensis and Lumbricus terrestris).
Environmental Pollution, 2014
The aim of this study was to estimate the bioavailability of essential (Zn, Cu) and non-essential metals (Cd, Pb) to the earthworm Lumbricus rubellus exposed to soils originating from a gradient of metal pollution in Southern Poland. Metal uptake and elimination kinetics were determined and related to soils properties. Experimental results were compared with tissue metal concentrations observed in earthworms from the studied transect. Cd and Pb were intensively accumulated by the earthworms, with very slow or no elimination. Their uptake rate constants, based on 0.01 M CaCl 2 -extractable concentrations in the soils, increased with soil pH. Internal concentrations of Cu and Zn were maintained by the earthworms at a stable level, suggesting efficient regulation of these metals by the animals. The estimated uptake and elimination kinetics parameters enabled fairly accurate prediction of metal concentrations reached within a life span of L. rubellus in nature.
HEAVY METAL CONTENT IN SOIL AND THEIR BIOACCUMULATION IN EARTHWORMS (Lumbricus terrestris L.)
The Journal "Agriculture and Forestry", 2020
The aim of this study was to determine the concentrations of heavy metals (Cu, Fe, Zn, Pb, and Cd) in the soil and earthworm body (Lumbricus terrestris), as well to estimate Bioaccumulation Factor (BAF) in earthworm body. The soil and earthworm samples were taken three times, from March to June 2018, in six different locations in Kosovo (Mitrovicë, Kishnicë, Kastriot, Barilevë, Drenas and Lipjan) and were brought to the laboratory for heavy metal analysis. Concentrations of heavy metals in soil and earthworm samples were determined by an Atomic Absorption Spectrophotometer (AAS) Perkin-Elmer brand model 1100 (Boston, MA, USA). Mean heavy metal concentration in soils were, 0.03-0.78mg/kg, 70.62-264.29mg/kg, 18.96-82.24mg/kg, 0.11-0.52 and 0.03-0.42mg/kg for Cu, Fe, Zn, Pb, and Cd respectively. The mean concentration range recorded in earthworms (Lumbricus terrestris) were 0.02-0.42mg/kg for Cu, 53.11-205.31mg/kg for Fe, 15.74-53.15mg/kg for Zn, 0.07-0.43mg/kg for Pb, and 0.01-0.37mg/kg for Cd. Based on the results obtained it was shown that there are statistically significant differences of different levels of significance regarding the content of heavy metals according to locality (Factor A), substrate (Factor B), heavy metal (Factor C) and factor interactions (A*B), (A*C), (B*C), and (A*B*C). The accumulation of heavy metals in earthworm samples maintains the same profile as mean heavy metal concentration of the soil Fe>Zn>Pb>Cu>Cd. Since some organisms like reptiles, birds and some other vertebrates feed on earthworms, transfer of these metals across the food chain is most likely, and therefore this research will be useful for risk assessment by relevant institutions responsible for the monitoring and surveying of environmental pollution and food security and safety in Kosovo.
Short-term changes of metal availability in soil. II: The influence of earthworm activity
Applied Soil Ecology, 2011
This study aimed to evaluate short-term earthworm-induced changes in the availability of metals applied to soil directly (metal-spiked) or via an organic matrix (sludge-amended). A laboratory experiment was performed using destructive sampling of microcosms filled with agricultural soil. A concentration gradient of industrial sludge contaminated predominantly with Cr, Cu, Ni, and Zn, and a soil freshly spiked with the same
Environmental Pollution, 2010
To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required. Lumbricus terrestris L. were incubated in three soils contaminated with As, Cu, Pb and Zn. The concentration and speciation of metal(loid)s in pore waters and the mobility and partitioning in casts were compared with earthworm-free soil. Generally the concentrations of water extractable metal(loid)s in earthworm casts were greater than in earthworm-free soil. The impact of the earthworms on concentration and speciation in pore waters was soil and metal specific and could be explained either by earthworm induced changes in soil pH or soluble organic carbon. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for leaching or uptake into biota.