Effective bioremediation of soil from the Burgan oil field (Kuwait) using compost: A comprehensive hydrocarbon and DNA fingerprinting study

Assessment of co-contaminated soil amended by graphene oxide: Effects on pollutants, microbial communities and soil health

Graphene oxide (GOx) is a nanomaterial with demonstrated capacity to remove metals from water. However, its effects on organic pollutants and metal(loid)s present in polluted soils when used for remediation purposes have not been extensively addressed. Likewise, few studies describe the effects of GOx on edaphic properties and soil biology. In this context, here we assessed the potential of GOx for remediating polluted soil focusing also on different unexplored effects of GOx in soil. To achieve this, we treated soil contaminated with concurrent inorganic (As and metals) and organic pollution (TPH and PAHs), using GOx alone and in combination with nutrients (N and P sources). In both cases increased availability of As and Zn was observed after 90 days, whereas Cu and Hg availability was reduced and the availability of Pb and the concentration of organic pollutants were not significantly affected. The application of GOx on the soil induced a significant and rapid change (within 1 week) in microbial populations, leading to a transient reduction in biodiversity, consistent with the alteration of several soil properties. Concurrently, the combination with nutrients exhibited a distinct behaviour, manifesting a more pronounced and persistent shift in microbial populations without a decrease in biodiversity. On the basis of these findings, GOx emerges as a versatile amendment for soil remediation approaches.

Application of compost assisted by Fe3O4 nanoparticles in di (2-ethylhexyl) phthalate-contaminated soil remediation: Biostimulation strategy, Soil responses, and RSM/CCD Optimization

Globally, contamination of agricultural soils by phthalate esters (PAEs) caused by direct consumption of plastic mulch films has been confirmed. The most widely used plasticizer is di (2-ethylhexyl) phthalate (DEHP), which is a more recalcitrant endocrine-disrupting chemical (EDC). Because of its low solubility and hydrophobicity, it remains in the soil longer, causes bioaccumulation in agricultural products, and has negative repercussions for food safety. In this study, the performance of kitchen organic waste compost assisted by Fe3O4 nanoparticles in DEHP removal efficiency (%) and soil C:N ratio (two responses) was optimized using Response Surface Methodology (RSM) based on Central Composite Design (CCD) in Design-Expert software (11.0.3.0). Under optimum conditions, a DEHP concentration of 10 mg·kg-1 (dw soil), a retention time of 35 days, an NPs dose of 0.99 g·kg-1 (media), a removal efficiency of 91.6 %, and a soil C:N ratio of 10.5 with a desirability of 0.963 were determined. A quadratic model (P-value <0.0001, adjusted R2 = 0.974 (Y1), 0.943 (Y2)) was used to predict the variables and their interactions. The agricultural soil responses in the treatments amended by compost and Fe3O4 NPs (SCN) showed a significant increase in SOM, TC, TN, AP, K, and Fe nutrients when compared to the control (P < 0.05). After 35 days, in the SC1N3 treatment (DEHP concentration = 10 mg·kg-1, NPs dose =1.2 g·kg-1), with higher DEHP removal efficiency (89.57 %), the C:N:P ratio was equal to 100: 9.75:0.69, and the total microbial colony count was 3.6 × 109 CFU/ml at pH 7.45. The study found that compost nutrients and Fe-based nanoparticle micronutrients can enhance DEHP degradation by stimulating the soil's native microflora. As a result, the synergistic potential of compost and Fe3O4 nanoparticles can be considered a promising, cost-effective, and agri-environmentally friendly approach in the "assisted bioremediation" strategy of DEHP-contaminated soils.

Nutritional additives dominance in driving the bacterial communities succession and bioremediation of hydrocarbon and heavy metal contaminated soil microcosms

Soil quality and microbial diversity are essential to the health of ecosystems. However, it is unclear how the use of eco-friendly natural additives can improve the quality and microbial diversity of contaminated soils. Herein, we used high-throughput 16 S rDNA amplicon Illumina sequencing to evaluate the stimulation and development of microbial diversity and concomitant bioremediation in hydrocarbon (HC) and heavy metal (HM)-rich waste disposal site soil when treated with meat and bone meal (MBM), cyclodextrin (Cdx), and MBM and cyclodextrin mixture (Cdx MBM) over a period of 3 months. Results showed that natural additive treatments significantly increased the soil bacterial diversity (higher Shannon index, Simpson index and evenness) in a time-dependent manner, with Cdx eliciting the greatest enhancement. The two additives influenced the bacterial community succession patterns differently. MBM, while it enhanced the enrichment of specific genera Chitinophaga and Terrimonas, did not significantly alter the total bacterial community. In contrast, Cdx or Cdx MBM promoted a profound change of the bacteria community over time, with the enrichment of the genera Parvibaculum, Arenimonas and unclassified Actinobacteria. These results provide evidence on the involvement of the two natural additives in coupling HC and HM bioremediation and bacterial community perturbations, and thus illustrates their potential application in ecologically sound bioremediation technologies for contaminated soils.