Effects of Fe...uthwest China_Xianjin An.pdf

ORIGINAL ARTICLE Acta Geochim(2023)42(1):125135 https:/doi.org/10.1007/s11631-022-00566-7 Keywords Inorganic ions Humin Phenanthrene Adsorption Soil Karst 1 Introduction The fate of PAHs in the natural environment is mainly con-trolled by physicochemical processes such as adsorption/desorption(Ukalska-Jaruga et al.2020;Schneckenburger&Thiele-Bruhn 2020;Chen et al.2021;Wang et al.2021),and their environmental toxic eff ects are closely related to their bioavailability.However,the traditional organic pol-lution risk assessment is still mainly based on the observed concentrations of organic pollutants,which may lead to overestimation of the short-term eff ects of organic pollut-ants and underestimation of their long-term eff ects in stud-ies(Alexander 2000;Louchart&Voltz 2007;Qian et al.2020a,b).A large number of studies have shown that soil organic matter(SOM)is an important component for the adsorption of toxic pollutants(Lamichhane et al.2016;An et al.2021).As a part of SOM,HM is the main component to control the adsorption of PAHs in soil.Studies have shown that HM is the momentous“hard carbon”in soil,which performs nonlinear adsorption of PAHs by kinds of ways such as surface high energy site and pore adsorption(Chen et al.2017).Many reports have been conducted on PAHs in karst ecology(Shao et al.2014;Yu et al.2018;Cheng et al.2021).Lan et al(2018)reported that the migration of PAHs in karst groundwater closely related to seasonal rain-fall.Zhu et al.(2022)illustrated that high ring PAHs were more enriched in the soil of typical karst trough valleys in Chongqing,and PAHs of soil generally caused a low risk of carcinogenicity.Qian et al(2020)showed that PAHs of low molecular weight was mainly found in the karst cave sedi-ment,and PAHs distribution had no signifi cant relationship with the sediment particle size.Chen et al(2022)shown that particle-promoted transport with rapid water fl ow was Abstract Humin(HM)is the main organic matter component to aff ect the migration and transformation of polycyclic aro-matic hydrocarbons(PAHs)in soil.The study on infl u-ence of the morphology change of inorganic ions on the adsorption of PAHs in soil and its organic matter is still rare at microscopic scale.In this paper,yellow soil humin(YS-HM)and lime soil humin(LS-HM)were chosen as samples,then Fe 3+and Ca 2+were added into samples to facilitate the precipitation by changing the existing con-ditions of ions,and the mechanism by which inorganic precipitation changed adsorption capacity of karst soil was analyzed from the microscopic scale.The results showed that the adsorption capacity of HM reduced with the inor-ganic precipitation increasing.The precipitation of Ca 2+and Fe 3+both reduced the adsorption capacity of YS-HM and LS-HM by 61.71%and 71.83%on average,respec-tively.The results of scanning electron microscope-energy dispersive spectrometry(SEM-EDS)and pore analysis showed that the HM porosity decreased after formation of Ca 2+and Fe 3+precipitation.According to the value of Freundlich parameter n,it may be because the precipitation or colloid of Ca 2+and Fe 3+fi lled micropores and covers high-energy adsorption sites of the HM.This research pro-vides theoretical support for studying the PAHs migration and bioavailability of Calcium-rich in karst soil.Wei Li 1 School of Karst Science ,Guizhou Normal University ,550001 Guiyang ,China 2 State Engineering Technology Institute for Karst Desertifi cation Control ,550001 Guiyang ,China 3 Guiyang University ,550005 Guiyang ,China 4 School of Geography and Environmental Engineering ,Gannan Normal University ,341000 Ganzhou ,China Received:11 July 2022/Revised:29 August 2022/Accepted:29 August 2022 /Published online:28 October 2022 The Author(s),under exclusive licence to Science Press and Institute of Geochemistry,CAS and Springer-Verlag GmbH Germany,part of Springer Nature 2022 Eff ects of Fe 3+and Ca 2+on sorption of phenanthrene by Humin in karst soil,Southwest China Xianjin An 1,2 Wei Li 3 Xinyue Di 4 Jiacheng Lan 1,2 Acta Geochim(2023)42(1):125135pivotal for PAHs mobilization to sediments and signifi cant correlations of PAHs compositions were observed in the multimedia environment of karst spring systems.However,these studies mainly focused on the environmental behavior of PAHs overall,and the migration of PAHs in karst soil is rarely reported from the microscale.The eff ect of HM on the PAHs adsorption is still rarely studied from the micro-scopic scale.In order to accurately investigate the eff ect of ion precipitation in high-calcium soils in karst areas on the adsorption of PAHs by hard carbon organic matter of soil-HM,HM was demineralized after extraction,and inorganic mineral ions(such as calcium and iron)were removed.The content of Ca 2+in the soil of karst areas is abnormal,which is 23 times that of the same type of soil in other areas(Gao et al.2019).Under the complex environmen-tal conditions of karst,the Ca 2+and Fe 3+are precipitated after saturati