2. Materials and methods
The study site is located in the north of France (Nord-Pas-de-Calais). Metal pollution is due to the accumulation
of zinc smelter wastes that were used for the construction of a road during the Second World War. A sampling protocol
on an irregular grid was designed to study the distribution of heavy metal pollution and macrofauna communities (Fig.
1a–c). Forty samples were taken at 0–20 cm in depth on eight parallel lines separated by regular 5 m intervals;
distance between the samples on a given transect increased from 1 m in the vicinity of the pollutant source to a
maximum of 3 m in the non-polluted area. Total zinc content was measured (AFNOR X31-147 method [1]) and a
map was realised with ADE-4 [16]. On the same grid, the
macrofauna community was sampled using a modified
Tropical Soil Biology and Fertility protocol [8], which
consists in an application of a 0.2% formalin solution to the
upper 10 cm of soil followed by hand-sorting. In order to
test the relation between zinc and soil fauna, a redundancy
analysis (RDA) was performed by means of a Canoco