Perils of irrigated agriculture in urban environment: case study from the Mumbai Metropolitan Region (MMR), India

The role of urban and peri-urban agriculture (UPA) role is to reduce urban poverty and ensure urban food security, income generation, and livelihood strategies that support Millennium Development Goals (MDGs). The UPA production systems often use intensive management techniques and untreated wastewater for food production. The use of untreated sewage may challenge the quality of food products and pose health hazards through the food chain. Quantitative data about the Phyto-availability and food chain transfer of heavy metals in the Mumbai Metropolitan Region (MMR) is scarce. This study was conducted to characterise the elemental and heavy metal transfer among major UPA production systems (farms and railway gardens), in MMR eliciting the soil to root translocation as well as its localisation in produce. It comprises a detailed two-year onsite examination of three farms (F1-3) and three railway gardens (RG1-3) across MMR. Potential risk assessments have been conducted by metal transfer factor (MTF), metal translocation (TF), daily intake of metals (DIM), health risk index (HRI), the average daily dose (ADD) and target hazard quotient (THQ), as well as total metal and element content in comparison with different safety standards. Copper concentration in soils ranged from 29.7 - 545 mg kg -1 , with the highest and lowest concentrations observed at RG3 and RG2, respectively. The shoots of white radish accumulated Sr concentrations up to 424 mg kg -1 at RG2. Strontium had a TF up to 32.3 compared with Co, Cu, Zn, Ni and Cr with a maximum of 5.9, 5.3, 3.4, 1.7 and 1.5, respectively. The average daily dose of Zn was between 1.3 × 10 -1 and 3.6 × 10 -1 mg kg -1 d -1 while Ni had a daily dose of between 4.6 × 10 -2 and 7.4 × 10 -2 mg kg -1 d -1 . The estimated values of ADD were below the world standard levels except for Cr and Ni, and there is a relative absence of health risk imposed by the ingestion of these vegetables produced in UPA systems in MMR. Detailed investigations are needed to identify the sources, mobilisation of heavy metals and trace element contaminations.