Municipal wastewater treatment plants (MWWTPs) are both sinks and sources of per- and polyfluoroalkyl substances (PFAS) due to limited removal efficiency in current treatment systems. However, the role of treatment processes, especially disinfection, in altering PFAS and microbial communities remains underexplored. In this study, we investigated the occurrence of 17 PFAS in two MWWTPs in Northwest China and characterized microbial communities through metagenomic sequencing. Results showed that total PFAS concentrations increased from 56.8 to 60.3 ng/L in MWWTP_A and from 5.1 to 19.1 ng/L in MWWTP_B, indicating ineffective removal. Perfluoropentanoic acid (PFPeA) and perfluorononanoic acid (PFNA) dominated the influent, accounting for 86.6% and 33.3% in MWWTP_A and MWWTP_B, respectively. In contrast, perfluorooctanesulfonic acid (PFOS, 46.8-52.4%) and perfluorooctanoic acid (PFOA, 5.1-8.9%) concentrations increased markedly in the effluent, becoming the predominant PFAS. Meanwhile, disinfection also altered microbial diversity and homogenized community structures between the two MWWTPs. Further analysis revealed strong associations (p < 0.01) between elevated PFAS levels and specific microbial taxa, including Actinomycetia and Thermoprotei, alongside increased relative abundance of genes annotated as haloacid dehalogenases, monooxygenases, and cytochrome P450. These associations may reflect potential influences on PFAS precursor dynamics. Overall, these findings highlight the importance of considering both chemical and microbial shifts when evaluating PFAS behavior during wastewater treatment.

Biochar has been widely applied for immobilization of potentially toxic elements (PTEs) in contaminated soils; however, its effects on metal transport under transient unsaturated conditions remain insufficiently understood. This study investigated the adsorption, desorption, and transport behavior of Pb²⁺ and Cd²⁺ in biochar-amended soils by combining batch experiments, unsaturated conditions column experiments, and transport modeling. The adsorption kinetics, isotherms, and desorption characteristics of Pb²⁺ and Cd²⁺ were evaluated under different biochar levels, and their redistribution during unsaturated infiltration was further analyzed using soil–water-dependent models. Biochar increased the apparent adsorption capacity of both metals, with a stronger response observed for Pb²⁺ than Cd²⁺. The Elovich and two-constant models provided better statistical descriptions of adsorption kinetics than the pseudo-second-order model, indicating that adsorption rate behavior involved heterogeneous and multi-rate processes. Freundlich fitting showed that Pb²⁺ and Cd²⁺ exhibited non-ideal adsorption behavior, while desorption experiments demonstrated a stronger reduction in apparent Pb²⁺ release compared with Cd²⁺ under biochar. Under transient unsaturated infiltration, Pb²⁺ and Cd²⁺ exhibited distinct transport patterns. Pb²⁺ redistribution was adequately described by a linear partitioning relationship, with R² values ranging from 0.988 to 0.990, indicating relatively stable solid–liquid partitioning within the tested conditions. In contrast, Cd²⁺ showed stronger dependence on soil–water conditions, and an empirical nonlinear water-dependent model improved model performance, increasing R² values from 0.533–0.652 for the linear model to 0.903–0.973. The results suggest that biochar effects on potentially toxic element migration under unsaturated conditions are element-specific, involving both apparent sorption enhancement and water-dependent redistribution processes. This study highlights that biochar performance in potentially toxic elements remediation should not be evaluated solely based on equilibrium adsorption capacity. Under field-relevant unsaturated conditions, amendment effectiveness may also depend on interactions between metal-specific retention behavior and soil hydraulic variability. Further studies integrating structural characterization, long-term aging, and reactive transport modeling are required to validate these processes under heterogeneous field conditions.

Carbon capture and utilization (CCU) is imperative for industrial decarbonization. However, current life cycle assessment (LCA) methodologies often apply a static, one-size-fits-all approach, assuming a 99% CO₂ purity standard for all utilization pathways. This ignores the thermodynamic limits of capture technologies and the tolerance of certain endpoints for coarse gas, leading to severe over-purification energy penalties. To bridge this gap, we developed a quality-matched dynamic LCA framework targeting steam methane reforming (SMR) tail gas in industrial parks. A superstructure matrix was constructed, coupling 16 capture configurations (spanning chemical absorption to cryogenic separation across 85–99% purities) with five utilization pathways, under a dynamic grid decarbonization model (2024–2060). The baseline scenario shows that methanol is the most carbon-intensive pathway at 16.88 kg CO₂-eq per kg CO₂ utilized, whereas mineralization and concrete curing remain near break-even at 0.221 and 0.010 kg CO₂-eq, respectively. When low-purity demand is matched with PSA capture at 85–90% purity, the net GWP of mineralization and concrete curing decreases to 0.134 and 0.005 kg CO₂-eq, corresponding to capture-stage penalty reductions exceeding 60% relative to unnecessary 99% purification. Under the dynamic electricity scenario, concrete curing reaches the net-zero tipping point around 2031, and the coupled mineralization substitution strategy ultimately achieves −0.046 kg CO₂-eq per kg CO₂ utilized. These findings provide a compelling scientific basis for policymakers to design dual-grade CO₂ pipeline networks and prioritize low-purity, high-circularity building materials over carbon-intensive chemical synthesis in near-term industrial transitions.