Assessment of the degree of external corrosion of buried water pipelines and source identification of heavy metals due to surrounding soil conditions in humid environment

Abstract

Water distribution pipelines installed underground has possible risks of pipe failure due to corrosion as it ages while urban soils have been noted to have highly elevated concentration of heavy metals due to various human activities. The study aimed to assess the degree of external corrosion of distribution pipe networks and identify probable sources of heavy metals in the surrounding aggressive soil environments. Soil samples were collected with the aid of soil auger at a depth of about 1.0 m while the analyzed soil properties and metals content were done using the standard procedures in the laboratory. The soil quality properties of interest are: soil pH, moisture content, soil temperature, soil resistivity, porosity, oxidation–reduction potential (ORP), chloride ions, sulphate ions, total carbon (TC), total nitrogen (TN), and microbial counts with heavy metals of Cu, Fe, Zn and Mn. Principal component analysis (PCA) was used to identify major soil quality indicators affecting soil corrosivity while multivariate analysis of variance (MANOVA) and cluster analysis (CA) were used to evaluate the spatial variability among the sampling locations, interrelationship between variables and source of heavy metals in soils, respectively. A total consideration of all the analyzed variables on the degree of external corrosion on buried pipelines indicates severely corrosive to mildly corrosive state. PCA identified chemical, moisture content, microbial influenced corrosion (MIC), and heavy metal as four principal factors accounting for 89.4% of total variation in soil quality properties. The results of multivariate statistical analyses identified two sources of metals as from soil parent materials and anthropogenic activities while MANOVA showed that the physio–chemical properties varied significantly different at $$\alpha =0.05$$ among the sampling locations.