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Bioremediation has drawn widespread concern in passivating heavy metals, but the intense toxicity of heavy metals to biological cells limits the application of functional strains. Herein, goethite-modified biochar (GMB) was chosen as the carrier to immobilize phosphate-solubilizing bacteria (PSB) of strain L1 for lead and cadmium remediation. Batch experiments showed that the GMB-L1 possessed excellent adsorption performance with a maximum adsorption of 496.54 and 178.18 mg/g for Pb and Cd, respectively. Moreover, adding GMB-L1 in contaminated soil converted heavy metals (Pb and Cd) into more stable fractions and reduced TCLP-extracted heavy metal concentrations (73.24% of Pb and 57.25% of Cd). The GMB-L1 was proved to accomplish Pb and Cd remediation via the process of chemical precipitation, surface complexation, electrostatic attraction, and biomineralization, which was accompanied by the transformation of heavy metals into a more stable crystal structure, such as Pb5(PO4)3OH and Cd5(PO4)3OH. Therefore, the co-system of GMB and strain L1 could be regarded as a prospective option for efficiently remedying environmental heavy metal pollution. [ABSTRACT FROM AUTHOR]

Sulfate radical-based advanced oxidation processes exhibit great potential for the degradation of organic pollutants. In this study, P-doped biochar (PBC500) was successfully synthesized by the pyrolysis of H3PO4-impregnated cow manure waste and was employed to activate peroxymonosulfate (PMS) for the elimination of 17β-estradiol (E2). The characterization results showed that the surface area, defective structure, and functional groups (C=O and phosphorus-containing groups) of biochar increased after H3PO4 modification. PBC500 exhibited high PMS activation activity and excellent E2 degradation capacity; 97.91% of 3 mg/L E2 can be removed within 90 min using 0.2 g/L PBC500 and 1 mM PMS. Based on the quenching experiments and X-ray photoelectron spectroscopy (XPS) analysis, defective structures, C=O, and P-C groups on biochar act as active sites to promote the catalytic oxidation of E2 by generating O2− and 1O2. In addition, PBC500 displayed excellent reusability, achieving 65.15% E2 degradation after three reuse cycles. Overall, this study presented a new technique that supports a high efficiency, environmentally friendly, and low cost treatment method for E2 wastewater and simultaneously provided a new option for the resource utilization of livestock waste. [ABSTRACT FROM AUTHOR]

Purpose: Nitrous oxide (N2O) is an important greenhouse gas. Soils are the main source and an important sink of N2O. Gross rates of soil N2O emission and uptake determine the net flux and concentration of N2O in the atmosphere. Denitrification is generally considered a key pathway of N2O consumption, during which N2O is reduced to N2 by nitrous oxide reductase (N2OR) encoded by nosZ genes. Although the soil pH is an important factor in denitrification, its effect on N2O uptake across the soil‒atmosphere interface is still unclear. Materials and methods: This study subjected acid red soil to eight different pH treatments (including 3.80, 4.47, 4.98, 6.08, 6.69, 6.99, 7.15, and 7.32) via lime application. An incubation experiment was conducted using a 15N2O dilution technique to quantify soil gross N2O emission, N2O uptake, and net N2O flux. Results and discussion: There are two contrasting gross N2O emission patterns in the tested pH range. When pH ≤ 4.98, the cumulative gross N2O emission decreased as the soil pH increased. In contrast, when pH > 4.98, the increasing pH promoted gross N2O emission. The significant positive correlation between gross N2O emission and net N2O flux indicated that the net flux of N2O is driven by gross emission rather than uptake. There was no observable effect on the cumulative N2O uptake in the 3.80–6.99 pH range, but it decreased at 7.15 and 7.32 pH. However, the copies of nosZ genes (both nosZ clades I and II) were inhibited at low pH and considerably increased with increasing soil pH. In addition, the cumulative N2O uptake/gross emission ratio was negatively correlated with soil pH. Conclusions: Our findings show that low pH inhibits soil nosZ without affecting N2O uptake. However, this study provides direct evidence for N2O absorption across the atmospheric soil interface. [ABSTRACT FROM AUTHOR]