Microbial community and heavy metals content in soils along the Curu River in Ceará, Brazil

This study aimed to survey the soils surrounding the Curu River with respect to the content of heavy metals and microbial community, besides evaluating the effects of heavy metals on the microbial community. Soil samples were collected from the layers of 0-5 cm and 5-30 cm at 22 sites, close to areas possibly contaminated by heavy metals. The samples were analyzed for granulometry, pH, electrical conductivity, organic matter (OM) and the contents of arsenic, cadmium, cobalt, chromium, copper, molybdenum, nickel, lead and selenium. The responses of microbial structures to the different soil uses were evaluated using phospholipid fatty acid PLFA analysis. Canonical correlation was used to verify possible relations between groups of variables (soil physical-chemical characteristics, heavy metals and soil microbiological attributes). The soil chemical and physical characteristics (clay, OM, silt, pH and sand) contributed to explain the contents of heavy metals in this soil, but the behavior of the microbiological attributes cannot be explained by the heavy metals in this soil. According to the national standards of the Environmental Company of São Paulo State (CETESB), some sites in the studied area are contaminated by heavy metals.