Soil heavy metal pollution caused by human activities has become one of the most critical environmental issues with a global concern. Phytoremediation is widely used due to its low cost and environmental friendliness. However, the impact of heavy metals on plant growth remains unclear. This study investigated the effects on the growth and photosynthetic activity of Picris divaricata Vant. under different cadmium concentrations using a hydroponics cultivation system. The results showed that the growth and photosynthetic processes of P. divaricata exhibited a phenomenon of promotion in low Cd concentrations and inhibition in high Cd concentrations. Under a low to medium Cd concentration (≤25 μM), there was no Cd toxicity in terms of plant growth, but high concentrations of Cd inhibited plant growth. The Fe content of leaves gradually increased as the Cd concentration increased; it reached 201.8 mg kg⁻¹ in 75 μM Cd. However, there was no significant difference in Mn between the 75 μM Cd treatment and the control (p > 0.05). The contents of carotenoid ranged between 3.06 and 3.26 mg/g across the different Cd treatments, showing no significant differences. The treatment with 5–75 μM Cd did not directly affect the photosynthesis of P. divaricata. Higher Cd concentrations reduced the stomatal density on the of P. divaricata leaves, resulting in stomatal and mesophyll conductance limitations, indirectly affecting P. divaricata photosynthesis. These research results provide a reference for evaluating and selecting heavy metal tolerant plants and provide environmentally friendly approaches to remediate heavy metal pollution.

Groundwater contamination at active petrol stations is a global concern, yet distinguishing natural hydrogeochemical backgrounds from anthropogenic signals remains challenging. We conducted a comprehensive survey at 21 petrol stations in central China, analyzing 62 groundwater and 21 soil samples for 45 parameters, including metals, BTEX, MTBE, petroleum hydrocarbons, and conventional ions. Using Positive Matrix Factorization (PMF) coupled with spatial statistics and hydrogeological analysis, we resolved four robust sources. Factor 1 (geological background) contributed 60–70% of Mn/Al and 48–93% (mean 68%) of the individual soil heavy metals. Factor 2 (reductive pollution) contributed 75–85% of NH₄⁺-N, oxygen consumption (COD_Mn), and elevated Fe, exceeding 90% in certain hotspots. Factor 3 (petroleum hydrocarbons) contributed 75–85% to MTBE (mean 83%) and 50–65% to groundwater petroleum hydrocarbons (C₁₀–C₄₀; mean 58%), confirming point-source releases. Factor 4 (industrial solvents) dominated VOCs at an isolated site (92%). Conventional exceedance assessment misclassified geogenic Mn (26.2-fold exceedance, 62% natural) as high priority while underestimating anthropogenic NH₄⁺-N (moderate mean exceedance, 81% human-derived). The “coarse-over-fine” stratigraphy controls spatial patterns, with low-permeability clay inducing long natural-attenuation lags (8–>30 years). We propose a source-differentiated management framework, transitioning from compliance-based to risk-based regulation. This approach provides a transferable paradigm for source apportionment in urbanizing regions facing similar contamination challenges.

Through sampling and analysis of 20 groundwater monitoring wells from nine oil storage enterprises in the Jiangbei New District of Nanjing, the pollution characteristics and chemical spatial distribution of total petroleum hydrocarbons (TPH) in the groundwater of the study area were revealed. TPH was detected in all 20 groundwater samples, with concentrations ranging from 0.26 to 90.24 mg/L. A factor analysis identified two principal factors, F1 and F2, representing the biodegradation processes of iron–manganese reduction and sulfate reduction, respectively. A correlation analysis showed that TPH was significantly positively correlated with total dissolved solids (TDS), total hardness, Fe, Mn²⁺, and oxygen consumption, but its correlation with sulfides and SO₄²⁻ was not significant. A further multiple regression analysis indicated that the relative contribution rates of electron acceptors followed the order of iron reduction (90.62%) > manganese reduction (9.35%) > sulfate reduction (0.032%), suggesting that TPH biodegradation is primarily dominated by iron–manganese reduction. Additionally, the study found that microbial growth was more robust in freshwater environments, facilitating TPH degradation, whereas saline environments inhibited microbial activity, thereby hindering TPH degradation.

Historical chemical production sites often harbor irregularly distributed solid waste landfills, posing significant environmental risks. Traditional drilling methods, while accurate, are inefficient for comprehensive characterization due to high costs and spatial limitations. This study aims to develop an integrated geophysical drilling approach to accurately delineate the spatial distribution and volume of landfilled solid waste (predominantly organic pollutants) at two decommissioned chemical plant sites (total area: 8954 m²). Methods: We combined (1) geophysical surveys (transient electromagnetic (TEM, 50 profiles, 2936 points), high-density resistivity (HDR, 2 profiles, 192 points), and ground-penetrating radar (GPR, 22 profiles, 1072.1 m)) and (2) systematic drilling verification (136 boreholes, ≤10 m × 10 m density). Anomalies were interpreted through integrating geophysical responses, historical records, and borehole validation. Spatial modeling was conducted using Kriging interpolation in EVS software. The results show that (1) the anomalies exhibited a “sparse multi-point distribution” across zones A2 (primary waste concentration), A4, and A6, which were differentiated into solid waste, foundations, contaminated soil, voids, and cracks; (2) drilling confirmed solid waste at nine locations (A2: “multi-point, small-quantity” residues; A6: contaminated clay layers with garbage) with irregular thicknesses (0.2–1.3 m); (3) TEM identified diagnostic medium–high-resistivity anomalies (e.g., 28–37 m in A4L3), while GPR detected 17 shallow anomalies (only one validated as waste); and (4) the total waste volume was quantified as 266.9 m³. The methodology reduced the field effort by ∼35% versus drilling-only approaches, resolved geophysical limitations (e.g., HDR’s volume effect overestimating the thickness), and provided a validated framework for efficient characterization of complex historical landfills.

Nano zero-valent iron (nZVI) and its modified forms are promising for remediation of heavy metal-contaminated soils, but bare nZVI aggregates and oxidizes readily. In this study, carboxymethyl cellulose (CMC), polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) were used to prepare modified nZVI. The modifiers increased electrostatic repulsion and steric hindrance, inhibited aggregation, and maintained reactivity. The modified particles were smaller (5–15 nm vs. ~50 nm for nZVI) and more dispersible. In three heavy metal-contaminated soils from Zn–Pb mine areas in China, modified nZVI showed improved mobility and retention; column effluent Fe reached 595.5 mg/L for P-nZVI in S1 and 639.6 mg/L for C-nZVI in S3, although mobility varied with soil properties. After stabilization, TCLP leaching of Zn, Cr, Pb, and Cu decreased significantly. Zn leaching was reduced by up to 95.0% (P-nZVI, S3) and 93.49% (C-nZVI, S2); Cr leaching was reduced by up to 98.6% (S-nZVI, S3) and 97.0% (P-nZVI, S3); Pb and Cu reached below detection limits under optimized treatments (C-nZVI or P-nZVI at 1.0 g/L Fe) in selected soils. The K value, defined as (F1 + F2)/(F3 + F4 + F5), decreased by up to 16.25% for Zn, 11.88% for Cr, 13.63% for Cu, and 10.04% for Pb. Because K represents the ratio of labile to stable fractions, its decrease indicates a shift from labile to stable fractions, enhanced immobilization, and reduced bioavailability. Overall, PVP-modified nZVI performed best for Zn and Cr, whereas CMC-modified nZVI was most suitable for Pb and Cu.