*2.2. Soils*

Thirty-five representative soils (Figure 1) were sampled in 6 of the 15 districts of the province of Havana, Cuba (Regla, San Miguel del Padrón, Plaza de la Revolución, 10 de Octubre, Playa, and Habana Vieja). The 35 soils have different uses: urban agriculture, parks and gardens, wooded areas, and vacant areas. The presence of PTEs in agricultural soils is of concern because of the risk of metal exportation to the food chain. In the case of parks and gardens, the main concern is related to the presence of children playing in these areas [15].

The agricultural soils were often built from soil materials transported from other locations. Some of them have a surface layer made of compost from various organic wastes. The urban

agriculture system developed in these soils is known as organoponics [21,22]. Others only had manure and vermicompost applied.

The studied soils are moderately alkaline (pH = 8.27 ± 0.20) and usually rich in calcium carbonate (CaCO3) in the surface horizon. The most frequent textures were clay, loam, or clay loam. According to the World Reference Base for Soil Resources [1], the selected soils were classified as Urbic or Garbic Technosols. Often the water table was near the soil surface, so that the soils had hydromorphic features. Twelve of the 35 soils studied showed gleyic properties. Gleyic properties mean current or past soil saturation with groundwater for a period that allows reducing conditions to occur [1].

**Figure 1.** Location of the studied soils in Havana, Cuba (map from Google Earth).

Several horizons were morphologically differentiated and sampled for each soil. Soil samples were air-dried and sieved (<2 mm) before analysis.
