1 Anthropogenic chromium (Cr) pollution in soils poses a great threat to human health through the food chain. It is imperative to understand Cr accumulation properties in common vegetables because the proportion of vegetables consumed has increased with the improvement of living standards. his study investigated Cr accumulation in pak choi (Brassica chinensis L.) grown on six representative agricultural soils in China. Chromium concentration in the edible parts of pak choi generally increased with soil Cr concentrations following the order: Ustic Cambosols > Periudic Argosols > Mollisols > Calcaric Regosols > Stagnic Anthrosols > Udic Ferrisols. Simple correlation analysis indicated that Cr concentration in pak choi was signiicantly correlated with the total Cr, Mehlich-3–extractable Cr, and Cr(VI). Stepwise multiple regression analysis also demonstrated that the phytoavailability of Cr was strongly correlated with the extractable fraction by Mehlich-3, total Cr concentration, soil organic matter, and Fe(II). Critical Cr concentrations in these six soils were evaluated for pak choi based on the maximum safe level for daily intake of Cr. Total soil Cr can be used as Cr thresholds for potential dietary toxicity in pak choi. Mehlich-3–extractable Cr is most suitable to be used as Cr thresholds for Periudic Argosols, Udic Ferrisols, Mollisols, and Ustic Cambosols, with values of 20.7, 15.8, 21.2, and 20.4 mg kg −1 , respectively, whereas Cr(VI) is most suitable for Calcaric Regosols and Stagnic Anthrosols, with values of 26.5 and 28.0 mg kg −1 , respectively. Accumulation of Chromium in Pak Choi (Brassica chinensis L.) Grown on Representative Chinese Soils Wendan Xiao, Xiaoe Yang,* Yibin Zhang, M. T. Raiq, Zhenli He, R. Aziz, and Tingqiang Li* C hromium (Cr) is a natural element in the earth’s crust and occurs in most unpolluted soils at concentrations of 10 to 150 mg kg −1 (Adriano, 2001). Anthropogenic Cr sources (e.g., ore reining, electroplating industry, tanning, paper making, steel production, and automobile manufactur- ing) contribute greatly to Cr pollution in the environment (Zayed and Terry, 2003). he lack of appropriate disposal facili- ties has led to severe Cr pollution in waters and soils throughout the world (Sethunathan et al., 2005). High Cr content in soils increases the potential uptake of the metal by plants, thus posing a great threat to human health through the food chain (Lavado et al., 2007). he proportion of vegetables consumed has increased with the improvement of living standards, and vegetables are also one of the most important pathways through which heavy metals enter the food chain and afect human health. Pak choi (Brassica chinensis L.), also known as bok or bok choy, is a popular veg- etable grown worldwide. It is therefore imperative to control Cr concentrations in pak choi, especially in its edible parts to, ensure food safety. To limit the accumulation of soil Cr in the edible parts of pak choi, a good understanding of its accumula- tion properties is crucial. here is a raised concern over Cr pollu- tion in food and its potential risks to human health (Wang et al., 2004; Mapanda et al., 2005). he toxicity of Cr to humans, plants, and animals mainly results from one of its oxidation states, Cr(VI), which exists as highly soluble oxyanionic species (i.e., CrO 4 2− [chromate], HCrO 4 − [bichromate], and Cr 2 O 7 2− [dichromate]) (Kozuh et al., 2000), is highly toxic and is a known human carcinogen (Costa and Klein, 2006). Cr(III), the other stable species of chromium in natural environments, is an essential trace element for mammals and is generally considered nonbioavailable due to its low solubility in water at a normal pH range (4–9) (Rai et al., 1987; Dayan and Paine, 2001). he mobility, toxicity, and plant uptake of Cr depend strongly on its oxidation states. he reduction and oxidation of Cr have been demonstrated to be associated with soil properties, including content of the electron donors [organic matter (Banks et al., 2006), Fe(II) (Buerge and Hug, 1997), Abbreviations: BV, background value; CEC, cation exchange capacity; Mn(ER), easily reducible Mn; OM, organic matter; PSD, particle size distribution. W. Xiao, X. Yang, Y. Zhang, M.T. Raiq, R. Aziz, and T. Li, Ministry of Education, Key Lab. of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang Univ., Hangzhou 310058, China; Z. He, Univ. of Florida, Institute of Food and Agricultural Sciences, Indian River Research and Education Center, Fort Pierce, FL 34945. Assigned to Associate Editor Brett Robinson. Copyright © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. J. Environ. Qual. 42:1–8 (2013) doi:10.2134/jeq2012.0419 Received 1 Nov. 2012. *Corresponding author (xyang571@yahoo.com; litq@zhu.edu.cn). Journal of Environmental Quality HEAVY METALS IN THE ENVIRONMENT TECHNICAL REPORTS