Different sources of irrigation water affect heavy metal accumulation in soils and some properties of guava fruits.

Guava is a highly nutritious fruit and widely grown in tropical and sub-tropical regions of the world. Guava orchards are frequently irrigated with contaminated water in different regions of the world. In the present study, fruits of two guava cultivars, i.e., Gola and Surahi were collected from orchards grown in peri-urban areas of Multan, Pakistan, which were irrigated with different sources of irrigation i.e., canal water, tubewell water, and sewage water. The soil (at four different layers), water, and fruit (at harvesting) samples were collected from the orchards for their physical, chemical, and heavy metal analysis. The results revealed that sewage water contained more concentrations of copper (Cu), zinc (Zn), and nickel (Ni) compared to tubewell and canal water. The soil irrigated with sewage water also contained the highest copper, nickel, and zinc contents, while tubewell water-irrigated soils contained the lowest copper, nickel, and zinc contents. As regards different soil layers, the top soil layer (0-15 cm) contained the maximum copper, nickel, and zinc contents. In contrast, the minimum copper, nickel, and zinc contents were estimated in the soil layer of 46-60 cm depth. The different physiological parameters of guava leaves i.e., photosynthesis (A net ), stomatal conductance (gs), transpiration (E), leaf chlorophyll fluorescence in light (Fv'/Fm') and in dark-acclimated (Fv/Fm), and non-photochemical quenching in dark-acclimated (NPQ) were decreased with sewage water irrigation. Furthermore, the sources of irrigation water significantly altered the different physical and chemical properties of the fruits. It is concluded that sewage water improved the physico-chemical properties of fruits but these also had high concentration of Cu, Ni, and Zn. The cadmium (Cd) was not detected in the fruits of guava cultivars, soils and in different sources of irrigation water. Furthermore, the soil irrigated with sewage water also had high contents of Cu, Ni, and Zn.