Speciation of Cr, Cu, Ni and Zn in soils irrigated with contaminated waters: A case study of agricultural soils from the plain of Saiss (Fez, Morocco)

The excessive input of heavy metals into agricultural soils has become one of the most important concerns in the third world cities all over the world. The contamination of agricultural soils can affect the health of people living in agricultural areas and the surrounding ecosystems. The current study was conducted to assess the quality of urban and suburban soils of the City of Fez (Morocco), which are irrigated by waters enriched by heavy metals. The main objective was to define the distribution and the mobility of heavy metals in different soil compartments using the method of sequential extractions. The samples were also investigated for mineralogy using X-ray diffraction. The identified minerals were mainly composed of quartz, carbonate and clay minerals. Smectite and mixed-layer (chlorite-vermiculite and mica-smectite) are by far the most abundant clay minerals in all soils. The study of the availability and distribution of heavy metals (Cr, Cu, Ni, Pb and Zn) in urban soils, allowed us to observe a total content of Cr in the Oued Fez soils which is lower than the contents in the Oued Sebou soils. The Cu and Zn contents are low in Oued Sebou. Despite the Oued Fez input; the contents of these elements in the confluence do not increase. Sequential extractions completed the study of the potential mobility of heavy metals in different fractions of the soil. Indeed, this has allowed us to show that Cr, Cu, Ni and Pb are mostly related to the residual fraction; they are therefore theoretically little mobile; while Zn is practically related to the metals oxides fraction and exchangeable phase, respectively, in soils (FEZ1, FEZ2, SEBup) and (SEBdown, SEBconf), therefore the Zn is potentially mobile

Evaluation of the environmental and human health risk related to metallic contamination in agricultural soils in the Mediterranean semi arid area (Saiss plain, Morocco)

International audienceIn the plain of Saiss, the most agricultural region of Morocco, the studies concerning the assessment of environmental and human risks related to metal contamination of agricultural soils are severely missing. To overcome the lack of such studies, trace-element analyses were carried out on six sampling sites of agricultural surface soils (66 sampling points), irrigated by superficial watercourses with high heavy metal contents. The average trace-element contents were 78, 55, 33, and 119 (mg kg−1), respectively, for Cr, Cu, Ni, and Zn. These values are above average worldwide soil and geochemical background levels. Multivariate statistical analyses, principal component, and cluster analyses suggest that soil contamination by Cr, Cu, and Zn is mainly due to wastewater irrigation, with the exception of Ni, which is probably of pedo-lithogenic origin. To provide further information on contamination transmission, the bioavailability and distribution of the four heavy metals in the soils were studied by sequential and single extractions. The results indicate that Cu and Zn are potentially available and can constitute a potential risk to the environment. The risk assessment of soil contamination was also carried out using risk assessment code, enrichment factor, contamination factor, degree of contamination, pollution lead index, geoaccumulation index, and potential ecological risk factors. The health risk evaluation by the Hazard Index was used to derive a combined risk of soil ingestion, dermal contact, and inhalation for adults and children. According to these indices, the soils present a moderate-to-high contamination for Cu and Zn elements, respectively. Hazard Index values indicate the relative absence of health risks associated to heavy metals for both adults and children

Speciation of Cr, Cu, Ni and Zn in soils irrigated with contaminated waters: A case study of agricultural soils from the plain of Saiss (Fez, Morocco)

The excessive input of heavy metals into agricultural soils has become one of the most important concerns in the third world cities all over the world. The contamination of agricultural soils can affect the health of people living in agricultural areas and the surrounding ecosystems. The current study was conducted to assess the quality of urban and suburban soils of the City of Fez (Morocco), which are irrigated by waters enriched by heavy metals. The main objective was to define the distribution and the mobility of heavy metals in different soil compartments using the method of sequential extractions. The samples were also investigated for mineralogy using X-ray diffraction. The identified minerals were mainly composed of quartz, carbonate and clay minerals. Smectite and mixed-layer (chlorite-vermiculite and mica-smectite) are by far the most abundant clay minerals in all soils. The study of the availability and distribution of heavy metals (Cr, Cu, Ni, Pb and Zn) in urban soils, allowed us to observe a total content of Cr in the Oued Fez soils which is lower than the contents in the Oued Sebou soils. The Cu and Zn contents are low in Oued Sebou. Despite the Oued Fez input; the contents of these elements in the confluence do not increase. Sequential extractions completed the study of the potential mobility of heavy metals in different fractions of the soil. Indeed, this has allowed us to show that Cr, Cu, Ni and Pb are mostly related to the residual fraction; they are therefore theoretically little mobile; while Zn is practically related to the metals oxides fraction and exchangeable phase, respectively, in soils (FEZ1, FEZ2, SEBup) and (SEBdown, SEBconf), therefore the Zn is potentially mobile