A case study was undertaken to assess the long-term
effects of irrigation with municipal waste water on heavy metalscontamination
of soil and leaf of black locust (Robinia pseudoacacia L.) trees.
For this purpose, a field study was conducted at two sites irrigated by
waste water and well water in the suburban areas of Tehran, Iran. Samples
of irrigation water, soil and tree leaf were collected and were analyzed
for Mn, Fe, Cr and Cd concentrations. Results indicated that municipal
waste water had higher significantly (p<0.01) amount of Mn, Fe and
Cr compared to well water. These heavy metals in waste water were upon
the internationally recommended (WHO) maximum permissible limits set for
land use. Heavy metals accumulation of soil was significantly greater
in waste water-irrigated site and in depth of 0-15 cm. The mean of heavy
metals concentration in soil was below the standard for all heavy metals.
Fe and Mn concentrations in leaf of trees irrigated with waste water were
significantly greater than those in well water but without risk. Cr and
Cd were not detected in leaves and also Cd in water and soil samples.
It was concluded that the use of waste water in irrigation might enriched
soils with heavy metals to concentrations that may pose potential environmental
and health risks in the long-term. Hence regulations about the utilization
of waste water in irrigation should consider for control heavy metals
content that may be added to soil, in order to minimize the risk of negative
effects to ecosystem health.
M. Tabari, A. Salehi and A.R. Ali-Arab, 2008. Effects of Waste Water Application on Heavy Metals (Mn, Fe, Cr and Cd) Contamination in a Black Locust Stand in Semi-Arid Zone of Iran. Asian Journal of Plant Sciences, 7: 382-388.