Remediation of petroleum-contaminated site soil by bioaugmentation with immobilized bacterial pellets stimulated by a controlled-release oxygen composite.

Bioaugmentation techniques still show drawbacks in the cleanup of total petroleum hydrocarbons (TPHs) from petroleum-contaminated site soil. Herein, this study explored high-performance immobilized bacterial pellets (IBPs) embed Microbacterium oxydans with a high degrading capacity, and developed a controlled-release oxygen composite (CROC) that allows the efficient, long-term release of oxygen. Tests with four different microcosm incubations were performed to assess the effects of IBPs and CROC on the removal of TPHs from petroleum-contaminated site soil. The results showed that the addition of IBPs and/or CROC could significantly promote the remediation of TPHs in soil. A CROC only played a significant role in the degradation of TPHs in deep soil. The combined application of IBPs and CROC had the best effect on the remediation of deep soil, and the removal rate of TPHs reached 70%, which was much higher than that of nature attenuation (13.2%) and IBPs (43.0%) or CROC (31.9%) alone. In particular, the CROC could better promote the degradation of heavy distillate hydrocarbons (HFAs) in deep soil, and the degradation rates of HFAs increased from 6.6% to 33.2%-21.0% and 67.9%, respectively. In addition, the IBPs and CROC significantly enhanced the activity of dehydrogenase, catalase, and lipase in soil. Results of the enzyme activity were the same as that of TPH degradation. The combined application of IBPs and CROC not only increased the microbial abundance and diversity of soil, but also significantly enhanced the enrichment of potential TPH-biodegrading bacteria. M. oxydans was dominant in AP (bioaugmentation with addition of IBPs) and APO (bioaugmentation with the addition of IBPs and CROC) microcosms that added IBPs. Overall, the IBPs and CROC developed in this study provide a novel option for the combination of bioaugmentation and biostimulation for remediating organic pollutants in soil.

Mendelian randomization analyses reveal causal relationship between liver volume and stroke.

BACKGROUND: Observational studies have suggested a potential association between abdominal viscera volume and increased risk of stroke. However, the causal relationship remains unclear. This study aims to utilize Mendelian randomization (MR) to explore the genetic causal relationship between them. METHODS: We conducted MR analysis to study the causal effects of five abdominal viscera volumes on stroke. The genetic variations of abdominal viscera volume were obtained from the UK Biobank, and the summary data for stroke and ischemic stroke were acquired from the MEGASTROKE consortium. This study employed inverse variance weighting (IVW), MR Egger, and weighted median methods. IVW served as the primary MR analysis method, supplemented by other sensitivity analyses to validate the robustness of the results. RESULTS: We found that liver volume can causally increase the risk of stroke [odds ratio (OR): 1.13, 95 % confidence interval (CI): 1.03-1.25, P = 0.013] and ischemic stroke (OR: 1.14, 95 % CI: 1.03-1.26, P = 0.012). No causal relationships between other abdominal viscera volumes and stroke and ischemic stroke appeared to be present (P > 0.05). Sensitivity analyses confirmed the robustness of the results. CONCLUSION: Our research findings indicate a causal relationship between liver volume and stroke, highlighting the potential role of liver volume in the onset of stroke. However, further basic and clinical research is needed to delve into the specific mechanisms underlying the relationship between liver volume and stroke, and to implement interventions aimed at reducing the impact of liver volume on stroke risk.