{"title":"Sediment-derived humic fractions regulate phosphate adsorption and retention by calcined modified red clay.","authors":"Anqi Guo, Xuemei Chen, Tongtong Rao, Debora Nkhata, Ninren Su, Wen Zhang","doi":"10.1007/s10653-026-03511-2","DOIUrl":null,"url":null,"abstract":"<p><p>Calcined modified red clay produced at 700 ° C (MRC-700) has been widely applied for phosphate removal in eutrophic waters. However, humic substances released from sediments may interfere with phosphate fixation and reduce its retention stability. This study employed sediment-derived humic acid (HA) and fulvic acid (FA) as representative humic fractions to examine their effects, together with critical water chemistry parameters, on phosphate adsorption, competition, and release behaviors related to MRC-700. Both HA and FA inhibited phosphate adsorption by MRC-700, although the magnitude of inhibition differed substantially between the two fractions. At the highest humic-fraction concentration tested, HA and FA reduced phosphate adsorption at 480 min by 74.1% and 40.8%, respectively. Preloading experiments further demonstrated that HA was more effective at destabilizing previously fixed phosphate. At a humic-fraction concentration of 100 mg·L<sup>-1</sup>, phosphate desorption induced by HA and FA reached 17.9% and 7.5%, respectively. Water chemistry conditions further regulated these competitive interactions. Lower pH and higher temperature enhanced phosphate adsorption by MRC-700, whereas the inhibitory effects of humic fractions persisted across these conditions. Increasing ionic strength mitigated the adverse influence of humic fractions on phosphate adsorption. Overall, the results indicate that sediment-derived HA can substantially constrain both the phosphate adsorption capacity and retention stability of MRC-700. These findings highlight the importance of considering humic-fraction composition and water chemistry when evaluating the effectiveness of mineral-based phosphorus control materials in eutrophic aquatic systems.</p>","PeriodicalId":11759,"journal":{"name":"Environmental Geochemistry and Health","volume":"48 15","pages":""},"PeriodicalIF":4.3000,"publicationDate":"2026-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Environmental Geochemistry and Health","FirstCategoryId":"93","ListUrlMain":"https://doi.org/10.1007/s10653-026-03511-2","RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENGINEERING, ENVIRONMENTAL","Score":null,"Total":0}
引用次数: 0
Abstract
Calcined modified red clay produced at 700 ° C (MRC-700) has been widely applied for phosphate removal in eutrophic waters. However, humic substances released from sediments may interfere with phosphate fixation and reduce its retention stability. This study employed sediment-derived humic acid (HA) and fulvic acid (FA) as representative humic fractions to examine their effects, together with critical water chemistry parameters, on phosphate adsorption, competition, and release behaviors related to MRC-700. Both HA and FA inhibited phosphate adsorption by MRC-700, although the magnitude of inhibition differed substantially between the two fractions. At the highest humic-fraction concentration tested, HA and FA reduced phosphate adsorption at 480 min by 74.1% and 40.8%, respectively. Preloading experiments further demonstrated that HA was more effective at destabilizing previously fixed phosphate. At a humic-fraction concentration of 100 mg·L-1, phosphate desorption induced by HA and FA reached 17.9% and 7.5%, respectively. Water chemistry conditions further regulated these competitive interactions. Lower pH and higher temperature enhanced phosphate adsorption by MRC-700, whereas the inhibitory effects of humic fractions persisted across these conditions. Increasing ionic strength mitigated the adverse influence of humic fractions on phosphate adsorption. Overall, the results indicate that sediment-derived HA can substantially constrain both the phosphate adsorption capacity and retention stability of MRC-700. These findings highlight the importance of considering humic-fraction composition and water chemistry when evaluating the effectiveness of mineral-based phosphorus control materials in eutrophic aquatic systems.
期刊介绍：
Environmental Geochemistry and Health publishes original research papers and review papers across the broad field of environmental geochemistry. Environmental geochemistry and health establishes and explains links between the natural or disturbed chemical composition of the earth’s surface and the health of plants, animals and people.
Beneficial elements regulate or promote enzymatic and hormonal activity whereas other elements may be toxic. Bedrock geochemistry controls the composition of soil and hence that of water and vegetation. Environmental issues, such as pollution, arising from the extraction and use of mineral resources, are discussed. The effects of contaminants introduced into the earth’s geochemical systems are examined. Geochemical surveys of soil, water and plants show how major and trace elements are distributed geographically. Associated epidemiological studies reveal the possibility of causal links between the natural or disturbed geochemical environment and disease. Experimental research illuminates the nature or consequences of natural or disturbed geochemical processes.
The journal particularly welcomes novel research linking environmental geochemistry and health issues on such topics as: heavy metals (including mercury), persistent organic pollutants (POPs), and mixed chemicals emitted through human activities, such as uncontrolled recycling of electronic-waste; waste recycling; surface-atmospheric interaction processes (natural and anthropogenic emissions, vertical transport, deposition, and physical-chemical interaction) of gases and aerosols; phytoremediation/restoration of contaminated sites; food contamination and safety; environmental effects of medicines; effects and toxicity of mixed pollutants; speciation of heavy metals/metalloids; effects of mining; disturbed geochemistry from human behavior, natural or man-made hazards; particle and nanoparticle toxicology; risk and the vulnerability of populations, etc.
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