Urban green roof versus roadside cultivation: effect of pollution, substrate type and fertilization on heavy metal concentration in oregano plants
The aim of this study was to investigate and assess the heavy metal concentrations in leaves of oregano (Origanum vulgare ssp. hirtum) cultivated at different urban sites. Rooted stem cuttings were planted, in April 2012, in plastic containers (40×60×22 cm) (two plants per container), with a green roof infrastructure fitted (moisture retention and protection of the insulation mat, drainage layer and filter sheet). Half of the containers were placed on a fully exposed third floor roof at the Agricultural University of Athens and the other half in the botanic garden of the Agricultural University of Athens alongside a main road with average traffic, in Athens, Greece. Two types of substrate were used, 40% peat:60% perlite, and 30% cotton gin trash compost:10% peat:60% perlite (v/v) with the same 12 cm depth. Half of the containers in each substrate and site were fertilized monthly with Nutrileaf 20-20-20, 4 g L-1. The experiment lasted six months. At the end of the experiment, the concentrations of lead (Pb), nickel (Ni), copper (Cu), zinc (Zn) and manganese (Mn), in the leaves of plants grown alongside the road were higher compared to those of plants on the roof, but only in half of the measurements the effect was statistically significant. However, in the compost-substrate without fertilization, all heavy metal values were statistically significant higher alongside the road. Plants grown on compost-substrate had higher concentrations of Ni, Pb and Zn when grown next to the road compared to those on the roof independently of fertilization, while the concentrations of Cu and Mn were higher in plants next to the road only in the non-fertilized plants. In addition, the concentrations of Cu and Pb in plants grown on peat-perlite was higher alongside the road, only in the non-fertilized plants. Finally, the concentrations of Ni and Pb, independently of location, fertilization and substrate type had exceed the FAO/WHO permitted levels for tissues of edible plants.
Papafotiou, M., Koutri, A. and Massas, I. (2017). Urban green roof versus roadside cultivation: effect of pollution, substrate type and fertilization on heavy metal concentration in oregano plants. Acta Hortic. 1189, 443-446
cotton gin trash compost, xyrophyte Mediterranean herb, Oreganum vulgare spp. hirtum, urban horticulture