Abstract Lead and zinc mine tailings from Guangdong, China were found to be toxic to two common species of the earthworm Pheretima, unless the spoil was diluted by at least 20% with an artificial uncontaminated soil. With different soil dilutions, there were significant differences in mortality, growth and Zn uptake between the two spe- cies. Zinc and arsenic were principally responsible for the toxicity of the tailings. LC 50 values for Zn, Pb, Cu and As for Pheretima were similar to those reported in the literature for Eisenia fetida. Following inoculation with the earthworms, spoil pH, EC and available metals increased; available-Pb and -Zn concentrations increased by up to 48.2% and 24.8% respectively. The findings suggest that earthworms may play an important role in reclamation of mining spoils to achieve a healthy soil supporting sustainable vegetation. Potentially increased toxicity of metals to plants and animals, through in- creased bioavailability in the presence of earthworms, is discussed in the context of their role in modifying the ef- ficiency of phytoremediation treatments. Keywords Mine tailings · Toxicity · Pheretima · Heavy metals · Reclamation Introduction Considerable advances have been made throughout the world over the last 30 years in reclaiming mine wastes such as lead/zinc tailings (Bradshaw and Chadwick 1980; Kimmerer 1984; Ernst 1990; Lan et al. 1997; Ye et al. 2000). Early attempts at reclamation involved estab- lishment of vegetation on an overburden of innocuous amendments. Subsoil or topsoil was applied to the sur- face of mine spoils, sometimes coupled with planting metal-tolerant grasses (McNeilly and Johnson 1981; Wong 1982a, 1987), or trees (Eltrop et al. 1991). As the desired end-point has moved away from reclamation for agriculture towards restoration for amenity and wildlife conservation (Dickinson 2000; Dickinson et al. 2000), less engineered and lower cost methods of treating the spoil have been the more recent goal of reclamation (Vangronsveld and Cunningham 1998). A more restrained and refined approach to reclama- tion has required a better understanding of metal mobili- ty and toxicity. Metal availability to plants and animals is higher under acid conditions, but may be reduced in fertile soils with better physico-chemical structures and higher organic matter contents. Thus, the reclamation process frequently involves addition of lime, organic wastes, fertilisers, or amendments such as zeolites (Wong 1982b; Gworeck 1992; Lan et al. 1998) or phos- phates that inactivate or precipitate the metals (Hodson and Valsami-Jones 2000). There is a possibility of using chelating agents and hyperaccumulator plants to remove the available fractions of metals from spoil (Blaylock et al. 1997; Vassil et al. 1998). Development of healthy, sustainable soils (Vangronsveld and Cunningham 1998) and more diverse plant communities (Zhang et al. 2000) in the longer term requires careful management of the conditions that influence metal mobility. One vital component of a healthy sustainable soil is often the earthworm community that develops and main- tains the structure of the soil, promoting the breakdown of organic matter and numerous other processes that pro- vide the integrity of soil (Edwards and Bohlen 1996). There have been numerous studies on heavy metal up- take, toxicity and accumulation by earthworms (Ireland 1975a; Ireland and Woolton 1976). Generally, earth- worms appear to be more sensitive to heavy metals than other soil invertebrates (Bengtsson et al. 1992) and they Y. Ma · M.H. Wong ( ✉ ) Institute for Natural Resources and Environmental Management, and Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China e-mail: mhwong@hkbu.edu.hk Tel.: +852-34117050, Fax: +852-34115995 N.M. Dickinson School of Biological and Earth Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK Biol Fertil Soils (2002) 36:79–86 DOI 10.1007/s00374-002-0506-0 ORIGINAL PAPER Y. Ma · N. M. Dickinson · M. H. Wong Toxicity of Pb/Zn mine tailings to the earthworm Pheretima and the effects of burrowing on metal availability Received: 11 February 2002 / Accepted: 16 May 2002 / Published online: 10 July 2002 © Springer-Verlag 2002