Study Area: Gazipur District is a suburban industrial area located 50 km north of the capital, Dhaka. The area covers 1806 km2, with a population of 3,403,912. A multi-industrial zone has recently been developed in the district. Rice and vegetables are planted on farmland adjacent to the zone. Recently, vegetable planting appears to be on the rise, particularly in the dry season. The district has a flat lowland topography with an elevation of 4–24 m. The annual average rainfall is 2036 mm, the wet season is from April to October, and the dry season from November to March. The annual average air temperature is 25.80C, with the lowest in January (18.80C) and the highest in August (28.80C) on average. The district is situated in the Madhupur Tract agro-ecological region, with dominant soils of deep to shallow red-brown terrace soils (entisols in US soil taxonomy), which have the characteristics of poor nutrients and acid basin clays. The target areas in the district are Banglabazar, Kashimpur, and Chandra, where various small-scale factories exist. The main industries are different in each area: textiles, dyes, batteries, metallurgy, and ceramics in Banglabazar; plastics, garments, and agrochemicals in Kashimpur; and pharmaceuticals, agrochemicals, fabric printing, poultry feed, and fish feed in Chandra. In all areas, industrial wastewater is discharged from factories into nearby irrigation canals throughout the year. Sampling of Irrigation Water, Soil, and Vegetables: Irrigation water, soil, and vegetables were sampled from the 3 targeted areas in November and December 2017 during the dry season. During the wet season, the sampling was done in June and July 2015. In the study area, yearly expansion of the industrial area was not observed from 2015 to 2017, because the numbers of factories and wastewater discharging points were the same in that time. Samples of 500 mL of water were collected from irrigation canals at 12 points selected randomly to represent the situation of contamination in each area. The samples were filtered through a paper filter and then a drop of HNO3 (65%) was added to make their pH < 2 for preservation. The samples were stored in acid-washed 20 mL plastic bottles and stored in a refrigerator at 4 0C until analysis. At each point, 5 soil samples were collected from topsoil (0–15 cm depth) to produce a single composite sample. Then, soil samples (12 samples in each area) were air-dried, ground, and sieved with 2 mm mesh sieve. The sampling depth of 0–15 cm was chosen based on the most active zone of maximum root concentration and the most sensitive zone of erosion and atmospheric deposition. Water 2019, 10, x 3 of 13 The target areas in the district are Banglabazar, Kashimpur, and Chandra, where various small-scale factories exist. The main industries are different in each area: textiles, dyes, batteries, metallurgy, and ceramics in Banglabazar; plastics, garments, and agrochemicals in Kashimpur; and pharmaceuticals, agrochemicals, fabric printing, poultry feed, and fish feed in Chandra. In all areas, industrial wastewater is discharged from factories into nearby irrigation canals throughout the year. Sampling of Irrigation Water, Soil, and Vegetables: Irrigation water, soil, and vegetables were sampled from the 3 targeted areas in November and December 2017 during the dry season. During the wet season, the sampling was done in June and July 2015. In the study area, yearly expansion of the industrial area was not observed from 2015 to 2017, because the numbers of factories and wastewater discharging points were the same in that time. Samples of 500 mL of water were collected from irrigation canals at 12 points selected randomly to represent the situation of contamination in each area. The samples were filtered through a paper filter and then a drop of HNO3 (65%) was added to make their pH < 2 for preservation. The samples were stored in acid-washed 20 mL plastic bottles and stored in a refrigerator at 4°C until analysis. At each point, 5 soil samples were collected from topsoil (0–15 cm depth) to produce a single composite sample. Then, soil samples (12 samples in each area) were air-dried, ground, and sieved with 2 mm mesh sieve. The sampling depth of 0–15 cm was chosen based on the most active zone of maximum root concentration and the most sensitive zone of erosion and atmospheric deposition. Sample Analysis: In sample preparation, soils were digested using a wet digestion method (US EPA 3050B method), and vegetables were digested at 120–130?C for 14–16 h using concentrated HNO3 and 30% H2O2. After that, the digested solutions of soil and vegetables were filtered through a 4 µm paper filter (No. 5B; Advantec, Toyo Roshi Kaisha Ltd., Tokyo, Japan) and diluted to a fixed volume. Heavy metal (Cr, Cu, Zn, As, Cd, and Pb) concentrations of irrigation water and the digested solutions of soil and vegetables were determined by using inductively coupled plasma–mass spectrometry (ICP-MS; 7500 ce, Agilent Technologies, USA) at the Center of Advanced Instrumental Analysis, Kyushu University, Japan. Data Analysis: Descriptive statistics and analysis of variance (ANOVA) for the heavy metal concentrations of irrigation water, soil, and vegetables were performed by Excel software (version 2016). The graphical presentation of data was made by Origin Pro 8 software. The t-test and hierarchical cluster analysis (HCA) were implemented by SPSS statistics software (version 21.0).