Abstract
Petroleum hydrocarbon (PHC) contamination of soil is a widespread global environmental concern due to the persistence and recalcitrant nature of PHCs. The PHCs are highly toxic and their removal from the terrestrial ecosystem is necessary to maintain soil as well as human health. Here, a pot experiment was performed to examine the impact of Enterobacter sp. MN17 and biochar addition on the growth of mungbean plants and PHCs removal from diesel-polluted soil. For this purpose, soil was contaminated artificially with diesel to achieve a final concentration of 5000 mg kg−1. Untreated and Enterobacter sp. MN17 treated mungbean seeds were sown in pots. Sugarcane bagasse biochar was applied as an amendment in respective pots along with the recommended levels of essential nutrients. Results showed that PHCs significantly suppressed the seedling emergence as well as agronomic and physiological attributes of mungbean as compared to un-contaminated controls. However, the co-application of Enterobacter sp. MN17 and biochar significantly reduced the phytotoxicity of PHCs to mungbean plants and effectively increased the seedling emergence, shoot and root length, shoot fresh and dry biomass, root fresh and dry biomass of plants up to 24%, 54%, 52%, 52%, 54%, 55% and 60%, respectively as compared to controls. Similarly, 30%, 57%, 64%, 36% and 57% increase in chlorophylls contents, transpiration rate, stomatal conductance, sub-stomatal conductance, and photosynthetic rate, respectively were observed in their combined application as compared to respective controls. Furthermore, the co-addition of biochar and Enterobacter sp. MN17 could remove 69% and 85% higher PHCs from unplanted and planted pots, respectively, than that of their respective controls. Our results suggest that the co-application of biochar and Enterobacter sp. MN17 may be useful in enhancing plant growth and eliminating PHCs from contaminated soil.
Highlights
To overcome the energy demands of the fast-growing industry and human population, the daily use of petroleum hydrocarbons (PHCs) is increasing alarmingly [1]
Our results indicated that PHC contamination substantially reduced the seedling emergence (Figure 1)
Strain MN17 or biochar applications were shown to be helpful in alleviating the toxic effects of PHCs on mungbean plants, enhancing the growth of plants in soil contaminated with PHCs
Summary
To overcome the energy demands of the fast-growing industry and human population, the daily use of petroleum hydrocarbons (PHCs) is increasing alarmingly [1]. Sci. 2020, 10, 8548 compounds comprising aliphatic, aromatic, resins, and asphaltenes that are highly toxic to living beings [2,3]. The contamination of PHCs in the soil mostly occurs due to accidental spills, underground storage malfunction, extraction and transportation losses and causes a serious environmental threat to all living communities due to recalcitrance and the xenobiotic nature of PHCs [4,5]. The soil contamination with PHCs results in infertile soil because of hydrophobic conditions that lead to low plant and microbial growth [6]. PHCs affect physico-chemical properties of soils such as pH, electrical conductivity (EC), total exchangeable cation, soil moisture and oxygen contents that disrupt micro-climate around the soil and impairs plant growth by reducing soil porosity [7,8]
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