Nonlinear transformation and release of arsenic fractions in soil and its implication for site risk assessment. (20th July 2020)

• Record Type: Journal Article
• Authors: Dong, Haochen; Xun, Yu; Feng, Liu; Yoneda, Minoru
• Is Part Of: Journal of cleaner production. Volume 262(2020)
• Publication Date: 2020-07-20
• Subjects: Site risk assessment -- Fraction transformation -- Arsenic -- Soil -- Static risk -- Dynamic risk; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2020.121304
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: Fraction transformation is the intrinsic driving force of risk formation and the evolution of sites polluted with heavy metals. This process is usually a long, slow and spontaneous process characterized by a gradual linear release of the most stable to the most mobile fractions, in accordance with fraction stability, leading to the thermodynamic static risk of the site. However, this process may be altered by drastic changes in environmental conditions, showing nonlinear characteristic and resulting in a nonlinear surge of some mobile fractions over a certain period of time. This process not only greatly increases the static risk but also induces the dynamic transient risk of the site. By applying a sequential extraction procedure, the delayed geochemical hazard methodology and statistical analysis, the transformation of arsenic fractions at a polluted site and their potential geochemical paths was investigated, which confirmed the above hypothesis. The transformation process was found to be mainly nonlinear. Taking water-soluble arsenic, surface-adsorbed arsenic, and acid-extractable arsenic as the endpoints, these nonlinear paths might lead to a surge in those three endpoint fractions when their associated arsenic fractions accumulate in the soil beyond a critical content, inducing dynamic risk and raising the static risk. These results provide new insights into site risk assessment, namely, that site risk highly depends on fraction transformation, especially on nonlinear transformation; therefore, both static and dynamic risks should be involved in site risk assessment. From this perspective, the case site (A total of 42 topsoil samples from Shimen realgar mine, Hunan) had a medium risk in terms of static risk, with a probability of 4.76%–7.14% of a possible burst of dynamic risk due to high arsenic accumulation in its some areas. Highlights: Static and dynamic risk were hypothesized and assessed for the site. Release of the stable arsenic fractions to the mobile ones preferred nonlinear. The studied site is posing medium static risk and low dynamic risk.