Pedosphere 27(3): 491--501, 2017
ISSN 1002-0160/CN 32-1315/P
©2017 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Refinement of methodology for cadmium determination in soil micro-arthropod tissues
ZHU Dong1,2, KE Xin3, WU Longhua1, HUANG Yujuan1, Peter CHRISTIE1,LUO Yongming4
1Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2 University of Chinese Academy of Sciences, Beijing 100049 (China)
3 Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032 (China)
4 Key Laboratory of Coastal Zone Environmental Processes, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003 (China)
      Highly precise and reliable determination of heavy metals in soil micro-arthropod tissues remains a challenge because of the small size of the animals and their typical low abundance in metal-contaminated agricultural soils.The present study sought to develop a method for cadmium (Cd) determination in soil micro-arthropods by optimizing the sample digestion procedure, reducing sample weight, modifying sample pre-treatment and validating the methodology with field samples.The optimized digestion conditions comprised a sample mass of 50--150 μg, digestion reagent of nitric acid:hydrogen peroxide (3:1), digestion temperature of 105 $^\circ$C, digestion period of 3 h and digestion volume of 30 μL. Defecation of the standard Collembola Folsomia candida (92 h) and the indigenous Collembola Onychiurus yodai (42 h) and ultrasonic cleaning of F. candida increased the accuracy of Cd determination. The recovery of Cd using the refined procedure was 98.9% and the limits of detection and quantification were 0.002 and 0.008 μg L-1, respecti-vely.The within-batch precision values were $<$ 3%. The Cd concentrations in the tissues of the Collembola Isotoma sp. collected from a range of metal-contaminated fields determined by the improved method were consistent with the Cd concentrations in the field soils.The results indicate that the optimized method can be used for more accurate or reliable determination of Cd concentrations in soil micro-arthropod tissues.
Key Words:  digestion, defecation, Folsomia candida, micro-samples, predatory mite, sample pre-treatment, ultrasonic cleaning
Citation: Zhu D, Ke X, Wu L H, Huang Y J, Christie P, Luo Y M. 2017. Refinement of methodology for cadmium determination in soil micro-arthropod tissues. Pedosphere. 27(3): 491--501.
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