Quantitative relationships between the adsorptivity of carbonaceous materials in soil for Pb(II) and soil organic matter content

Mapping soil cadmium content using multi-spectral satellite images and multiple-residual-stacking model: Incorporating information from homologous pollution and spectrally active materials

Soil cadmium (Cd) contamination significantly threatens ecosystems and human health. Traditional geochemical investigation, although accurate, is impractical for wide-area and frequent monitoring applications. Multi-spectral satellite images combined with the homologous pollution information (HPI) and the spectral and content information of soil organic matter (SOMSCI) is an unconventional and promising approach for large-scale, dynamic soil heavy metal (SHM) monitoring. Based on a novel Multiple-Residual-Stacked (MRS) machine-learning framework, the study estimated the soil Cd content in Yueyang City, China, during the past decade (2014-2023) using Landsat 8 images. Within it, three feature construction methods and four models were employed. The experimental results indicate that the XGB-MRS model incorporating HPI and SOMSCI significantly improved the estimation performance (RPD exceeded 90 %, R2, RMSE, and MAE exceeded 40 %). Moreover, against 243 ground samples during 2016-2022, the average overall estimation accuracy exceeded 80 %, validating the model's robustness and practicality. Furthermore, the descending order of contribution in the modelling is environmental auxiliary variables (55 %), HPI and SOMSCI (26 %), and spectral information (19 %). The fertilizer usage has direct (up to 2 years) and delayed (3-5 years) effects on soil Cd accumulation. Overall, our study provides a scalable framework for monitoring global SHM pollution using open-source multi-spectral satellite data.

Transport of bisphenol A, bisphenol S, and three bisphenol F isomers in saturated soils

With the limitation of the use of bisphenol A (BPA), the production of its substitutes, bisphenol S (BPS), and bisphenol F (4,4'-BPF) is increasing. Understanding the fate and transport of BPA and its substitutes in porous media can help reduce their risk of contaminating soil and groundwater systems. In this study, column and batch adsorption experiments were performed with 14C-labeled bisphenol analogs and combined with mathematical models to investigate the interaction of BPA, BPS, 4,4'-BPF, 2,2'-BPF, and 2,4'-BPF with four standard soils with different soil organic matter (SOM) contents. The results show that the transport capacity of BPS and 4,4'-BPF in the saturated soils is significantly stronger than that of BPA. Meanwhile, the mobility of the three isomers of bisphenol F exhibits variability in saturated soils with high SOM content. The two-site nonequilibrium sorption model was applied to simulate and interpret column experimental data, and model simulations described the interactions between the bisphenol analogs and soil very well. The fitting results underscore SOM's role in providing dynamic adsorption sites for bisphenol analogs. Hydrophobicity primarily accounts for the disparity in adsorption affinity between BPA, BPS, 4,4'-BPF, and soil, whereas hydrogen bonding forces may predominantly influence the differential adsorption affinity between 4,4'-BPF and its isomers and soil. The results of this study indicate that BPS and three isomers of BPF, as alternatives to BPA, have higher mobility in saturated soils and may pose a substantial risk to groundwater quality. This study enhances our understanding of bisphenol analogs' behavior in natural soils, facilitating an assessment of their environmental implications, particularly regarding groundwater contamination.

The adsorption characteristics of Cu(II) and Zn(II) on the sediments at the mouth of a typical urban polluted river in Dianchi Lake: taking Xinhe as an example

This study is to determine the spatial distribution characteristics of Cu and Zn adsorption on the sediments of the estuary of Dianchi Lake, as well as the composite adsorption law of Cu and Zn on combinations of sediment organic matter, metal oxides, and organic-inorganic composites. The relationship between the adsorption contribution of each component of the substance. A static adsorption experiment was applied to the sediments in the estuary of Dianchi Lake. The relationship between adsorption capacity and sediment composition was analyzed through correlation analysis and redundant analysis. The results show that along the direction of the river flow and the vertical depth, the adsorption capacity presents a relatively obvious spatial distribution law; the change trend of sediment component content is not the same as the change trend of Cu and Zn adsorption capacity. The change trend of the sediment component content is not the same as the change trend of the adsorption amount of Cu and Zn, and the compound effect between the components affects the adsorption amount. The adsorption of Cu by the four groups of sediments after different treatments is more in line with the Freundlich isotherm adsorption model; When adsorbing Zn, the untreated and removed organic matter and iron-aluminum oxide group are in good agreement with the Freundlich model, while the organic matter-removed group and the iron-aluminum oxide removal group are more consistent with the Langmuir isotherm adsorption model; The adsorption contribution rate of organic-inorganic composites in sediments is not a simple addition of organic matter and iron-aluminum oxides, but a more complex quantitative relationship.

Mechanisms of aromatic molecule - Oxygen-containing functional group interactions on carbonaceous material surfaces

Surface oxygen-containing functional groups (OFGs) at different sites of carbonaceous materials showed different effects on the normalized monolayer adsorption capacity (Q_BET/A) obtained from the modified BET model. The OFGs on mesoporous surfaces inhibited the adsorption via the water competition, whereas those on the external surface promoted the adsorption due to the enhanced hydrophobic driving force and electrostatic forces, as analyzed from the adsorption molar free energy. Multiple linear relationships were established between the monolayer adsorption capacity Q_BET/A and the amounts of OFGs on mesoporous and the external surfaces ([O]_meso and [O]_external, respectively). The properties of aromatic adsorbate compounds, the polar area radio of aromatic molecule to water (PA_ad/w), and the log K_ow together influenced the inhibition or promotion effects of OFGs. These results would allow predictions of adsorption behavior of aromatic compounds on carbonaceous materials on the basis of OFGs parameters. Theoretical calculations and simulations projected the configuration of aromatic molecules being parallel to the graphene sheets of carbonaceous materials. The symmetry-adapted perturbation theory (SAPT) energy decomposition showed that the electrostatic forces intensified with the increase of adsorbate polarity. These analyses revealed that the electrostatic forces were enhanced in the presence of OFGs and that the π-π EDA (electron donor-acceptor) was the main force.

Adsorption of Cadmium on Degraded Soils Amended with Maize-Stalk-Derived Biochar

Biochar has been extensively proven to distinctively enhance the sorption capacity of both heavy metal and organic pollutants and reduce the related environmental risks. Soil pollution and degradation widely coexist, and the effect of biochar addition on adsorption behavior by degraded soils is not well understood. Four degraded soils with different degrees of degradation were amended with maize-stalk-derived biochar to investigate the adsorption of cadmium using batch methods. The maximum adsorption capacity (Q_m) of degraded soil remarkably decreased in comparison with undegraded soil (5361 mg·kg⁻¹→170 mg·kg⁻¹), and the Q_m of biochar increased with increasing pyrolysis temperature (22987 mg·kg⁻¹→49016 mg·kg⁻¹) which was much higher than that of soil. The addition of biochar can effectively improve the cadmium adsorption capacity of degraded soil (36–328%). The improving effect is stronger when increasing either the degradation level or the amount of added biochar, or the pyrolysis temperature of biochar. Contrary to the general soil–biochar system, adsorption of Cd was not enhanced but slightly suppressed (7.1–36.6%) when biochar was incorporated with degraded soils, and the adsorptivity attenuation degree was found to be negatively linear with SOM content in the degraded soil–biochar system. The results of the present study suggest that more attention on the adsorption inhibition and acceleration effect difference between the soil–biochar system and the degraded soil–biochar system is needed.