Physicochemical and microbial properties of urban park soils of the cities of Marrakech, Morocco and Toruń, Poland: Human health risk assessment of fecal coliforms and trace elements

The public green space (PGS) in urban areas presents an image of nature and its animal and plant biodiversity in the city. Due to intense urbanization in the world, pollutants such as trace elements (TE) or pathogenic microorganisms are continually emitted into the environment and pose a threat to ecosystems. The aim of this work was to assess the soil quality of PGS in the cities of Marrakech (Morocco) and Toruń (Poland) through physicochemical and microbiological approaches and to assess related health risks. Eighteen soils from the most visited historic parks in Marrakech and Toruń were sampled and analyzed. The results showed that content of Total Organic Carbon (TOC) in Toruń urban soils is about three times higher than that measured in Marrakech urban park soils. These differences are related to the naturally higher content of organic matter in the soils of temperate climate regions than in Mediterranean soils. The concentrations of trace element (TE) showed a similar trend in both cities, except for Pb in one Marrakech site, which exhibited a high concentration (400 mg Pb Kg⁻¹ in Bab Rab Park). Soil enzymes present a high sensitivity to anthropogenic disturbances and can be used as tool to evaluate early disturbance of urban soils. The alkaline phosphatase (APHa) and urease (URa) activities are less affected by anthropogenic pressure than dehydrogenase (DHa). Slight sensitivity to TE was observed in the microbial community in the order fungi < actinomycetes < bacteria. Total and fecal coliforms (TC, FC) were present in all soil samples, with higher concentrations in Marrakech sites. Based on estimated FC risk, the highest percentage did not exceed 11% of the guideline limit set by International Commission on Microbiological Specifications for Foods. Hazard index showed no health risk for adults caused by studied TE concentrations in the park soils of Marrakech and Toruń, but potential adverse non-cancer health effects for children. Their safety depends on their own behavior and the ways by adults supervise them.