Accumulation of trace elements by corn (Zea mays) under irrigation with treated wastewater using different irrigation methods

Treated wastewater reuse for irrigation has gained a greater significance as an alternative resource to meet the growing water demands for agriculture and reduce the pressure on limited existing fresh water. However, this reuse needs adapted management in order to avoid environmental and health risks. An experiment was conducted in a greenhouse to evaluate the effect of different irrigation methods on the Metallic Trace elements and metals concentrations of a Tunisian soil (pH = 8.6) and corn when using treated wastewater. Four irrigation methods: surface irrigation, sprinkler irrigation, drip irrigation and subsurface drip irrigation, and two water qualities were used: treated wastewater and fresh water. Samples of soil and corn were analyzed for several Metallic Trace elements. Results for soil showed that treated wastewater increased electrical conductivity, nutrients and metallic trace elements. The highest levels of salinity and Metallic Trace elements were recorded with using surface irrigation and the lowest were noticed by using subsurface drip irrigation. Whereas the highest levels of nutrients elements were recorded by using subsurface drip irrigation. Results for corn showed that irrigation with treated wastewater improved corn biomass, increased nutrient elements, nitrate reductase activity and chlorophyll content. The concentrations of Metallic Trace elements in different parts of corn were significantly higher under treated wastewater irrigation than fresh water irrigation and were reduced in case of subsurface drip irrigation. Among studied metals, Nickel concentration exceeded the permissible limits of 10 mg kg^-1. Bio-concentration factor values were, in order, Iron > Zinc > Nickel > Copper > lead > Cadmium, whereas, translocation factor values were, in order, Copper > Zinc > Cadmium > iron > lead > Nickel. Because of translocation factor < 1 and bio-concentration factor ≥ 0.2, maize could be considered as both an excluder and an accumulator plant. Results of this study indicate that the use of subsurface drip irrigation decreased the amount of soil and corn contamination by Metallic Trace elements.