title: Effect of environmental factors on the complexation of iron and humic acid.
abstract: A method of size exclusion chromatography coupled with ultraviolet spectrophotometry and off-line graphite furnace atomic absorption spectrometry was developed to assess the complexation properties of iron (Fe) and humic acid (HA) in a water environment. The factors affecting the complexation of Fe and HA, such as ionic strength, pH, temperature and UV radiation, were investigated. The Fe-HA complex residence time was also studied. Experimental results showed that pH could influence the deprotonation of HA and hydrolysis of Fe, and thus affected the complexation of Fe and HA. The complexation was greatly disrupted by the presence of NaCl. Temperature had some influence on the complexation. The yield of Fe-HA complexes showed a small decrease at high levels of UV radiation, but the effect of UV radiation on Fe-HA complex formation at natural levels could be neglected. It took about 10 hr for the complexation to reach equilibrium, and the Fe-HA complex residence time was about 20 hr. Complexation of Fe and HA reached a maximum level under the conditions of pH 6, very low ionic strength, in the dark and at a water temperature of about 25°C, for 10 hr. It was suggested that the Fe-HA complex could form mainly in freshwater bodies and reach high levels in the warm season with mild sunlight radiation. With changing environmental parameters, such as at lower temperature in winter or higher pH and ionic strength in an estuary, the concentration of the Fe-HA complex would decrease.
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen 361102, China. Electronic address: justmist@126.com.
authors.forename: Kai
authors.initials: K
authors.lastname: Fang
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen 361102, China. Electronic address: yuandx@xmu.edu.cn.
authors.forename: Dongxing
authors.initials: D
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen 361102, China. Electronic address: 460203861@qq.com.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen 361102, China. Electronic address: 635847814@qq.com.
authors.forename: Lifeng
authors.initials: L
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen 361102, China. Electronic address: chenyaojin05xd@163.com.
authors.forename: Yaojin
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen 361102, China. Electronic address: 199205061@qq.com.
authors.forename: Yuzhou
authors.initials: Y
authors.lastname: Wang
mesh_terms: D002850:Chromatography, Gel; D004777:Environment; D004784:Environmental Monitoring / Q000379:methods*; D063366:Estuaries; D005618:Fresh Water / Q000032:analysis; D006812:Humic Substances / Q000032:analysis*; D007501:Iron / Q000737:chemistry*; D012621:Seasons; D013054:Spectrophotometry, Atomic; D013056:Spectrophotometry, Ultraviolet; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D014874:Water Pollutants, Chemical; D007501:Iron
keywords: Complexation; Graphite furnace atomic absorption spectrometry; Humic acid; Iron; Size exclusion chromatography