Physical And Chemical Properties Of Soil Lab Report

Soil properties: Some physical and chemical properties of the soil were measured, which are presented in Table 1. The availability of nutrients and even contaminants depends on the degree of soil acidity. The most suitable pH for soil microorganism’ activity is 7, as nutrient solubility depends on soil pH changes (Riser-Roberts, 1998). The soil used in the present study has neutral pH and therefore does not limit the activity of microorganisms or the solubility of nutrients except for phosphorus.
According to results provided in Table 1 and using the soil texture triangle, the type of soil was identified as loamy sand. Since the clay content percentage of this soil is low, the adsorption of hydrocarbons to these particles is also decreased
95.8% vs. 75,9% in F8 treatment) (Fig. 3). Heavy hydrocarbons were less exposed to microorganisms due to their lower solubility in an aqueous phase and higher adsorption on soil surfaces; as a result, their degradation is also lower. Haritash and Kaushik (2009) stated that presence of light oils instead heavy ones can increase the bioavailability of PAHs. Soleimani et al. (2010) reported the lowest degradation degree of benzo (ghi) perylen (a 6-ring PAH) and concluded that high-molecular-weight PAHs do not easily serve as a carbon and energy source for microbial populations during degradation. They also stated that benzo (ghi) perylene could be removed in the presence of plant root exudates through the co-metabolism
Given these findings, it can be asserted that B. mojavensis and B. licheniformis have potential for improving the conditions for remediation. The different degrading behaviour of bacteria toward the types of hydrocarbons (light or heavy) can be attributed to the unique properties of each bacterium. Each bacterium acts uniquely in its degradation of certain hydrocarbons based on its specific enzyme system (Lease, 2004). According to results of the present study, it can be asserted that the mechanism of bio and phytoremediation (Rhizoremediation), which involves the plant and its dependent microbial activities in the rhizosphere, is greatly capable of removing PAHs from the soil. In such plant–bacteria partnership, plant supplies the bacteria with a special carbon source that stimulates them to degrade organic contaminants in the soil. In response, bacteria can support the plant to conquer contaminated-induced stress responses, and improve plant growth and development. Additionally, plants get benefits from the bacteria with hydrocarbon-degradation ability, leading to enhanced hydrocarbon mineralization and lowering of both phytotoxicity and evapotranspiration of volatile hydrocarbons (Khan 2013a, b) and improved the efficiency of phytoremediation (Weynes et al. 2009). Su and Zhu