Bioavailability and mobility of organic contaminants in soil: new three-step ecotoxicological evaluation

Abstract

A novel approach was developed for rapid assessment of bioavailability and potential mobility of contaminants in soil. The response of the same test organism to the organic extract, water extract and solid phase of soil was recorded and compared. This approach was designed to give an initial estimate of the total organic toxicity (response to organic extractable fraction), as well as the mobile (response to water extract) and bioavailable fraction (response to solid phase) of soil samples. Eighteen soil samples with different levels of pollution and content of organic carbon were selected to validate the novel three-step ecotoxicological evaluation approach. All samples were chemically analysed for priority contaminants, including aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), hexachlorocyclohexane (HCH) and dichlordiphenyltrichloroethane (DDT). The ecotoxicological evaluation involved determination of toxicity of the organic, mobile and bioavailable fractions of soil to the test organism, bacterium Bacillus cereus. We found a good correlation between the chemical analysis and the toxicity of organic extract. The low toxicity of water extracts indicated low water solubility, and thus, low potential mobility of toxic contaminants present in the soil samples. The toxicity of the bioavailable fraction was significantly greater than the toxicity of water-soluble (mobile) fraction of the contaminants as deduced from comparing untreated samples and water extracts. The bioavailability of the contaminants decreased with increasing concentrations of organic carbon in evaluated soil samples. In conclusion, the three-step ecotoxicological evaluation utilised in this study can give a quick insight into soil contamination in context with bioavailability and mobility of the contaminants present. This information can be useful for hazard identification and risk assessment of soil-associated contaminants. Graphical Abstract New three-step ecotoxicological evaluation by using the same organism.

Carbon mineralization, biological indicators, and phytotoxicity to assess the impact of urban sewage sludge on two light‐textured soils in a microcosm

“…This is mainly explained by the phenomena of biostimulation and bioaugmentation of soil microorganisms through the supply of nutrients and exogenous biodegraders brought along with sludge amendments (Ambrazaitiene et al., 2013; Hamdi et al., 2007b). Furthermore, it has been shown that the bioavailability of contaminants in soil decreases with increasing concentrations of organic C owing to the enhancement of soil adsorption capacity (Navarro, 2012; Prokop, Nečasová, Klánová, & Čupr, 2015). As for heavy metal immobilization, clay–humic complexes play very important roles in regulating the transport and retention of hydrophobic organic contaminants in soils (Wang & Xing, 2005)…”

Assessing ecotoxicological effects of 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, and 2,3,4,7,8-PeCDF in soil using Allivibrio fischeri

“…The acute toxicity was determined by following the 81.9% basic test method for the liquid samples [10,11], and the Basic Solid-Phase Test with nine serial dilutions of the test solution for the soil samples [12]. With contaminated soil samples, the toxicity tests were carried out in three phases of water extract, solid-phase, and organic extract to assess the bioavailability and potential mobility of contaminants in soil [13]. The water extracts were used to test the mobile fraction of the contaminants, while the soil slurry were used to test the bioavailable fraction of the contaminants [13].…”

“…With contaminated soil samples, the toxicity tests were carried out in three phases of water extract, solid-phase, and organic extract to assess the bioavailability and potential mobility of contaminants in soil [13]. The water extracts were used to test the mobile fraction of the contaminants, while the soil slurry were used to test the bioavailable fraction of the contaminants [13]. The organic extracts are used to represent the total organic toxicity of the contaminated soil [13]; however, in this study, the toxicity obtained using the dioxin standards was used to represent the total organic toxicity of dioxins in contaminated soils.…”

“…The water extracts were used to test the mobile fraction of the contaminants, while the soil slurry were used to test the bioavailable fraction of the contaminants [13]. The organic extracts are used to represent the total organic toxicity of the contaminated soil [13]; however, in this study, the toxicity obtained using the dioxin standards was used to represent the total organic toxicity of dioxins in contaminated soils.…”

“…This can be attributed to the increased bioavailable fractions of contaminants in the soil samples due to direct contact between the bacteria and the soil sample [12]. In other words, the toxic effects of the bioavailable fraction were greater than the toxic effects of the mobile fraction of the dioxins in the soil samples (i.e., the water extracts) [13]. Also, the luminescence of the bacteria can be affected by the color and turbidity of the samples as well [12].…”