Ecological impact evaluation by constructing in situ microcosm with porous ceramic arrowhead
Graphical abstract
Introduction
Rapid global industrial development has increased environmental pollution from various hazardous chemicals, making cleanup of polluted sites a major concern. Bioremediation takes advantage of the metabolic activities of microorganisms to degrade environmental pollutants and has been used as an effective technique for cleaning polluted sites. Additionally, bioremediation is cost-effective and does not produce secondary environmental pollution. However, bioremediation treatment efficacy depends on the indigenous microbial composition of the polluted site, and treatment efficacy can vary considerably among sites. Thus, understanding the microbial composition at a specific site is essential for efficient bioremediation (Hara et al., 2013a, 2013b). Additionally, several previous studies found that environmental pollutants can affect the microbial composition of the polluted site (Evans et al., 2004; Margesin et al., 2003; Ringerlberg et al., 2001). Thus, evaluating the impact of pollutants on indigenous microorganisms is also essential for predicting bioremediation treatment efficacy.
Traditionally, ecological impact evaluation has been conducted using the flask microcosm method (Chikere et al., 2012; Goigic-Cvijovic et al., 2012; Nyyssönen et al., 2006, 2008; Ringerlberg et al., 2001; Roling et al., 2002). Although this method is simple and poses no risk of contaminating the environment, the flask microcosm greatly differs from the natural environment (Yang et al., 2010). Thus, data obtained from a flask microcosm experiment may not accurately reflect the microbial composition of the natural environment. To better estimate microbial composition, in situ field studies have been conducted (Evans et al., 2004; Lors et al., 2012; Rojas-Avelizapa et al., 2007; Swannell et al., 1996). However, in situ approaches require vast field areas, utilize heavy industrial machinery, and have a high environmental impact. Thus, the development of a novel in situ ecological impact evaluation method that includes the advantages of conventional methods is needed.
In this study, we evaluated the efficacy of a porous ceramic arrowhead for in situ ecological impact evaluation of phenol, a common environmental pollutant. The arrowhead has a cylindrical shape that enables the addition of various chemicals within its cavity. Upon burial in the soil, chemicals added to the arrowhead percolate into the soil, creating a unique “in situ microcosm” environment (Fig. S1). Thus, the impact of various pollutants on soil microorganisms can be evaluated by analyzing the soil from the in situ microcosm.
Section snippets
Porous ceramic arrowhead material and dimensions
The porous ceramic arrowhead was made from Kibushi clay (IA city, Mie prefecture, Japan) using a vitrification process. Kibushi clay is a kind of kaolin; it is characterized by fine particle-size and has high plasticity and dry strength compared to other clays. The clay was kneaded, molded using a mold, thoroughly dried, and then baked in a kiln at approximately 1250 °C. Five arrowheads were chosen at random, and the dimensions (height, external diameter, internal diameter, and depth) and
Porous ceramic arrowhead material and dimensions: development of a new in situ microcosm construction tool
The porous ceramic arrowhead used in this study is shown in Fig. 1. The average weight of the five randomly selected arrowheads was 7.78 ± 0.12 g; their dimensions were not significantly different.
The dimensions of the arrowhead are shown in the diagram. Various chemicals can be added to the cylindrical cavity of the arrowhead for gradual percolation into the soil.
Arrowhead-mediated phenol percolation into soil
Phenol percolation into autoclaved soil was assessed by GC-MS (Fig. 2). The phenol concentration was highest near the arrowhead and
Discussion
In this study, an ecological impact evaluation method was developed. Unlike conventional methods, this novel method enabled construction of an “in situ microcosm” using a porous ceramic arrowhead. The arrowhead is ceramic, selectively permeable, and allows chemicals to pass through, while blocking the passage of microorganisms. Thus, the arrowhead prohibits direct contact of soil microorganisms to high concentrations of chemicals. Additionally, the arrowhead is composed of clay, which is an
Conclusion
In conclusion, the porous ceramic arrowhead method combines the advantages of various conventional ecological impact evaluation methods. The arrowhead method can be used for cost-effective in situ ecological impact evaluation with low contamination risk. Additionally, this method can be used for assessing the effectiveness of bioremediation. Overall, the arrowhead method may have potential applications in numerous subject areas, including bioremediation studies.
Further studies are required to
Conflicts of interest
The authors have no conflicts of interest to declare.
Dual first authorship
Eri Hara and Takuya Yoshimoto contributed equally to this work.
Acknowledgements
This work was partly supported by JSPS KAKENHI (Grant-in-Aid for Challenging Exploratory Research) (grant number 23658067).
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