No abstract

The high concentrations of trace elements in the environment, especially the carcinogenic elements Cr, Cd, and As, in populated areas can lead to an increased non-carcinogenic risk and carcinogenic risk in humans via the effective exposure pathways (inhalation and dermal contact). In this study, the concentrations of the trace elements Cd, Cr, and As in four media were comprehensively evaluated by collecting samples from atmospheric precipitates (A), wheat (W), soil (S), and groundwater (G) in the agricultural plain. This study not only considers the health risk level, but also focuses on the relationship between soil properties and the soil–wheat system. First, according to the results of the analysis, the concentration of carcinogenic elements in atmospheric precipitates was higher than that in other media. The sequence follows the order A > S > W > G. Moreover, the input flux of A was at a relatively higher level (determined via an input flux calculation) than other farming areas. Second, the pollution of Cr, Cd, and As in A and S were analyzed using the geoaccumulation method, and the level of Cd reached mild to moderate pollution. In addition, it was found that the bioaccumulation factors (BAFs) of Cd were much higher than those of As and Cr in the soil–wheat system. Furthermore, it was found that the negative relationship between BAFs and pH, CEC (cation exchange capacity), Corg (soil organic carbon), and clay was significant. Lastly, the hazard quotient (HQ) of the non-carcinogenic risk and carcinogenic risk (CR) of the three elements in multiple media were calculated using the health risk model. The HQ results showed that the total non-carcinogenic risk index (HI) of Cd, As, and Cr in the multiple-media did not exceed the risk limit (1.00), and there was no significant risk to the locally exposed population. However, the total carcinogenic risk index (TCR) indicated that the risk index of Cr, As and Cd in multiple media exceeded the safety index range (≈10−6–10−4), and the three elements posed a significant carcinogenic risk to local residents via the main pathways. In terms of individual elements, the risk of cancer was highest via the ingestion of the carcinogenic element Cd in G and W.

Interaction between the AgNP coating and the cell membrane structure of Gram-negative E. coli reduces both the AgNP–cell affinity and AgNP mobility in porous media, but has little effect on the E. coli mobility. These mechanisms help to protect the bacteria against AgNP.

Preparation of sludge-derived mesoporous carbon materials (SMCs) through pyrolysis of excess activated sludge from urban municipal sewage plants is an effective means of reducing pollution and utilizing a waste resource. This paper presented a method of SMC preparation in which calcium oxide (CaO), polyacrylamide (PAM), and chitosan (CAS) flocculating agents were used as pore-forming additives. Physical and chemical characterizations of the prepared SMCs were conducted by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The prepared SMCs were used to adsorb a tetracycline (TC) antibiotic pollutant. The influences of pH, adsorption time, temperature, and pollutant concentration on TC adsorption capacity were determined. The experiments demonstrated that weakly acidic conditions were conducive to TC adsorption, which mainly occurs via electrostatic and π-π interactions. The TC adsorption process by SMCs conformed better to the pseudo-second-order models, indicating that chemical adsorption was the dominant adsorption process. The isothermal adsorption of TC by the SMCs conformed to the Freundlich model. This implied that TC easily adhered onto the SMC surfaces via multilayer homogeneous adsorption. Thermodynamic studies revealed that the adsorption of TC onto SMCs was spontaneous and endothermic.