A field experiment was conducted to evaluate the environmental risk of phytoextraction of Cd, Cu, and Pb using Sedum alfredii Hance. with different intercropping patterns. Three receptors representing invertebrates (earthworms), avians (yellow‐feathered chickens), and small mammalian omnivores (Rattus losea) were selected as the potentially impacted environmental receptors. Soil deglutition and food ingestion are considered dominant pathways of metal exposure. Different planting patterns, including S. alfredii monoculture and S. alfredii intercropped (coordinate and malposed) with Cicer arietinum L., were used to evaluate the mobilization, absorption, and migration of Cd during phytoextraction. This study revealed that the intercropping systems, particularly the malposed intercropping patterns, significantly increased the Cd decontamination efficiency by 31.3% and enhanced the content of Cu and Pb in the aboveground tissues of the intercropped C. arietinum. Correspondingly, different planting patterns resulted in varying environmental risks. For the omnivores, which primarily consume earthworms and plant tissues, the hazard index was 0.096 for the S. alfredii monoculture, and the index decreased to 0.074 and 0.090 in the coordinate and malposed intercropping patterns, respectively. The environmental risk might be induced by the increased Cd concentrations in the roots and shoots of S. alfredii. When extrapolating the results of this treatment to the entire region, all the environmental hazard index values of the receptors were higher than 1.0. This study suggests that if a phytoextraction method is used for metal decontamination, corresponding prevention strategies should be established to prevent the diffusion of concentrated metals to higher trophic levels via the food chain.
Recently, rampant eutrophication induced by phosphorus enrichment in water has been attracting attention worldwide. However, the mechanisms by which phosphate can be eliminated from the aqueous environment remain unclear. This study was aimed at investigating the adsorption performance and regulation mechanisms of the zeolite-biochar composite for removing phosphate from an aqueous environment. To do this, physicochemical properties of the zeolite-biochar composite were assessed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) specific surface area (SSA) analyzer, and transmission electron microscopy (TEM). Adsorption tests were performed to evaluate the adsorption ability of the composite material for mitigating excess phosphorus in the aqueous environment. The findings evinced that the phosphorus removed by PZC 7:3 (pyrolyzed zeolite and corn straw at a mass ratio of 7:3) can reach 90% of that removed by biochar. The maximum adsorption capacities of zeolite, biochar, and PZC 7:3 were 0.69, 3.60, and 2.41 mg/g, respectively. The main mechanism of phosphate removal by PZC 7:3 was the formation of thin-film amorphous calcium-magnesium phosphate compounds through ligand exchange. This study suggests that PZC 7:3 is a viable adsorbent for the removal of phosphate from aquatic systems.
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