Pedosphere 27(3): 616–629, 2017 doi:10.1016/S1002-0160(17)60356-4 ISSN 1002-0160/CN 32-1315/P c ⃝ 2017 Soil Science Society of China Published by Elsevier B.V. and Science Press Chemical Availability of Cd, Pb and Zn in Anthropogenically Polluted Soil: Assessing the Geochemical Reactivity and Oral Bioaccessibility Christophe WATERLOT ∗ , Francis DOUAY and Aur´elie PELFR ˆ ENE Yncr´ea Hauts-de-France, Laboratoire G´enie Civil et g´eoEnvironnement (LGCgE), 48 boulevard Vauban, 59046 Lille cedex (France) (Received February 17, 2016; revised April 14, 2017) ABSTRACT The most recent in vitro tests used to determine metal bioaccessiblility are generally time-consuming and expensive. This study aimed at determining potential relationships between the concentrations of metals extracted using single-extraction methods and the concentrations of bioaccessible metals assessed by a harmonised in vitro test, the Unified BARGE Method (UBM). A total number of 27 soil samples were collected from kitchen gardens and lawns with various physicochemical parameters and contamination levels. Significant relationships were obtained between Cd, Pb and Zn extracted in gastric and gastrointestinal phases and using single extractions. The best relationhips were established using acetic and citric acids for Cd, whereas for Pb, citric acid and ethylenedi- aminetetraacetic acid (EDTA) were identified as the best extractants. These relationships were improved by means of a linear multiple regression with a downward stepwise procedure involving agronomic parameters (soil cation exchange capacity and assimilated P). This method highlighted the fact that the cation exchange capacity and P contents in soils were the two main parameters that controlled the human bioaccessibility of Cd, Pb and Zn in the gastric phase. Besides, the metal concentrations extracted with the acetic and citric acids correlated well with the metal concentrations in the gastric and gastrointestinal phases, suggesting that the bioaccessible metals were mainly in a soluble form, weakly bound to the organic matter and associated with the carbonates and the Fe and Mn oxides/hydroxides in soils. Key Words: gastric phase, gastrointestinal phase, linear multiple regression, single extractant, urban soil Citation: Waterlot C, Douay F, Pelfrˆene A. 2017. Chemical availability of Cd, Pb and Zn in anthropogenically polluted soil: Assessing the geochemical reactivity and oral bioaccessibility. Pedosphere. 27(3): 616–629. INTRODUCTION Metals and metalloids are generally present in varying amounts in the contaminated environmental compartments (e.g., water, sediment and soil). Some of these elements are known as essential for plants and animals, while others affect the fauna and flora and generate damages to human health. These conse- quences depend on the pollutant types and their con- centrations and speciations. Thus, the accurate estima- tion of the environmental availability and the human oral bioaccessibility are becoming more and more im- portant as risk assessments in the last decades. Since many years ago, in vitro methodologies have been developed to simulate exposure to contamina- ted soils via the human ingestion pathway (Oomen et al., 2002; Drexler and Brattin, 2007). Simulated inges- tion systems consist of one, two or three phases (e.g., mouth phase at near neutral pH, stomach phase at acidic pH and intestine phase at near neutral pH) and can include dynamic or batch-based systems at human body temperature (37 ◦ C). Among the in vitro met- hods used for the measurement of the oral bioacces- sibility of metals and metalloids in soils (Wragg and Cave, 2003; Van de Wiele et al., 2007), the Bioacces- sibility Research Group of Europe (BARGE) has de- veloped a harmonised in vitro bioaccessibility method (the Unified BARGE Bioaccessibility Method, UBM) in order to overcome problems related to the wide- ranging bioaccessibility values between the various in vitro methods applied owing to the different opera- ting conditions, i.e., chemical products, enzymes and residence time (Oomen et al., 2002; Meunier et al., 2010). Briefly, the UBM test consists of two parallel extractions, simulating the chemical processes in the mouth and stomach (gastric, G) compartments and those in stomach and intestinal (gastrointestinal, GI) compartments. These two parallel extractions provided samples for analysis of metals in the G and GI phases, respectively. From a theoretically point of view, the * Corresponding author. E-mail: christophe.waterlot@yncrea.fr.