A nature-based solution to water pollution: A viable option for urban forestry

Sewage water is one of the leading causes of pollution in developing countries. The key concern is its use for irrigating agriculture crops including vegetables and fruits in many low-and middle-income countries. Sewage water not only pollutes the land but also contaminates the edible produce due to accumulation of heavy metals and other poisonous material. This study not only provided a nature-based solution for disposal of toxic sewage water but also offered an economically viable option for urban forestry. Five tree species, Eucalyptus camaldulensis, Populus deltoides, Pinus roxburgii, Platanus orientalis, and Melia azedarach were selected for the evaluation of growth performance and heavy metals accumulation. One-year-old saplings of these tree species were transplanted into pots and applied with fresh water (T0), 100 percent sewage water (T1) and 50 percent sewage water (T2). This study concluded that Eucalyptus and Populus species performed remarkably well in terms of biomass and heavy metals accumulation. Melia and Platanus are relatively slow-growing thus their biomass accumulation was lower than Eucalyptus and Populus but their heavy metal accumulation was ample. Heavy metal accumulations in plants were observed the most where watered with T1. The highest amount of Arsenic was 1.44 mg L-1 and Cobalt was 0.08 mg L-1 in Eucalyptus plants with T1. Zinc was under the safe limits in all samples analyzed, Lead was 137.37 mg L-1 in Eucalyptus plants with T1, very high compared to safe limits defined by World Health Organization (WHO). We recommend planting Eucalyptus camaldulensis, Populus deltoides, and Melia azedarach species for urban forestry in the Abbottabad region, using sewage water for irrigation.