Earthworm and organic amendment effects on microbial activities and metal availability in a contaminated soil from China Chi Zhang a , Philippe Mora c , Jun Dai a , Xufei Chen a , Stephanie Giusti-Miller c , Nuria Ruiz-Camacho b , Elena Velasquez d , Patrick Lavelle b, * a College of Natural Resources and Environment/College of Public management, South China Agricultural University, 510642 Guangzhou, China b Institute of Ecology and Environmental Science (IEES), Université Paris XII, Créteil, France c UMR BioEMCo (UMR 7618), University Paris Est Créteil, 61 av du General de Gaulle 94000 Créteil, France d Universidad Nacional de Colombia, Palmira, Colombia A R T I C L E I N F O Article history: Received 25 February 2015 Received in revised form 4 March 2016 Accepted 5 March 2016 Available online xxx Keywords: Contaminated soil Earthworms Organic matter dynamics Microbial activities Available metals A B S T R A C T We tested the effect of an addition of organic matter (OM: 10% of a mixture of coconut bran and cattle dung) and/or earthworm inoculation (15 g fresh weight kg 1 soil) in a soil polluted by metals on microbial activities and concentrations of metal DTPA extractable fractions. The experiment, conducted under laboratory conditions, lasted for 60 days. Soil organic C and total N in control were 15.3and 1.47 mg kg 1 , and total Zn, Cd, Pb and Cu contents, 405, 0.639, 439 and 394 mg kg 1 , respectively. The native earthworm species Amynthas morrisi exhibited 91.5% mortality in the un-amended polluted soil, whereas only 20% of Eisenia fetida individuals died. In the OM treatment the native species performed much better showing reproduction and a higher soil ingestion rate than E. fetida. In both amended and non-amended soils, casts exhibited higher concentrations of total organic C (+15.7 to 46.5%) and N(+13.3 to 59.3%) and alkali hydrolysable N (+78.0 to 133%), but not dissolved organic C. Microbial enzymatic activities were significantly increased when OM was added to the soil (+142 to 456%), with the sole exception of acid phosphatase activity. The addition of earthworms had contrasting effects on microbial activities: N- acetyl glucosamine activity was enhanced (+559 to 829%) while no significant difference was noted for other measured enzymatic activities. Introduction of earthworms in OM amended treatments tended to decrease all activities (30.6 to 59.3%) although they were still higher than in the non- amended soil, especially for b-glucosidase (+182 to 230%). We noted no significant differences between the effects of the two earthworm species. Increased microbial activities resulting from the addition of organic matter did not substantially alter the availability of Zn, Cd, Pb and Cu assessed by their association with DTPA. Earthworm increased the availability of Zn (up to +31%), Cd (+ 78 to 193%) and decreased Pb (down to 16.4%) in the non-amended treatment. In the amended treatment earthworms induced an increase in Cd (up to 18.8%), but a decrease in Zn availability. Total Cd available concentrations in the experimental units (in soil and casts when earthworms were present) increased from 36.2% in control soil to up to 46.1% after 60 days depending on treatments, while no significant changes were observed for other metals. This rather important change obtained for Cd in such a short amount of time indicates a possible environmental risk. ã 2016 Elsevier B.V. All rights reserved. 1. Introduction In China, 19.4% of cultivated land is polluted, with 82.8% of this pollution originating from metals contained in contaminated waste, irrigation with contaminated water, chemical fertilizers or non-point source industrial contamination (Meng, 2014). Never- theless, most of these soils are still used for cropping (Gong et al., 2005). Metal contamination has resulted in degradation of soil quality, decreases in crop yields, and threats to human health (Liu et al., 2005). Remediation of heavy metal polluted soils has therefore become an urgent necessity. Current remediation operations are generally associated with civil-engineering techni- ques or some environmentally friendly options using phytoreme- diation (Vangronsveld and Cunningham, 1998; Lasat, 2000; Wong, 2003). A new generation of remediation techniques proposes the * Corresponding author at: Bioemco UMR 7618, Centre IRD Ile de France, 32 rue H. Varagnat, 93143 Bondy Cedex, France. E-mail address: Patrick.Lavelle@ird.fr (P. Lavelle). http://dx.doi.org/10.1016/j.apsoil.2016.03.006 0929-1393/ ã 2016 Elsevier B.V. All rights reserved. Applied Soil Ecology xxx (2015) xxx–xxx G Model APSOIL 2406 No. of Pages 13 Please cite this article in press as: C. Zhang, et al., Earthworm and organic amendment effects on microbial activities and metal availability in a contaminated soil from China, Appl. Soil Ecol. (2016), http://dx.doi.org/10.1016/j.apsoil.2016.03.006 Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil