## 3 Results and Discussion  
### Seasonal and Spatial Variation of Heavy Metal Content  
The average concentration of different metals in the agricultural soil of the study area in two seasons is given in Table 5. Average concentration of Fe, As, Mn, Cu, Zn, Cr, Pb, Hg, Ni and Cd in the study area during the dry season was 30,404, 4,073.1, 339, 60, 209, 49.66, 27.6, 486.6, 48.1 and 0.0072 mg/kg, respectively. While average concentration of Fe, As, Mn, Cu, Zn, Cr, Pb, Hg, Ni and Cd in the wet season was 17,103, 2,326.2, 305, 90, 194, 34.2, 23.83, 133.2, 5.5 and 1.04 mg/kg, respectively. So the trend of metals according to mean concentration in the dry season was: \(\mathrm{As}\)\(>\)\(\mathrm{Fe}\)\(>\)\(\mathrm{Hg}\)\(>\)\(\mathrm{Mn}\)\(>\)\(\mathrm{Zn}\)\(>\)\(\mathrm{Cu}\)\(>\)\(\mathrm{Cr}\)\(>\)\(\mathrm{Ni}\)\(>\)\(\mathrm{Pb}\)\(>\) Cd, while in the wet season the trend was: \(\mathrm{As}\)\(>\)\(\mathrm{Fe}\)\(>\)\(\mathrm{Mn}\)\(>\)\(\mathrm{Zn}\)\(>\)\(\mathrm{Hg}\)\(>\)\(\mathrm{Cu}\)\(>\)\(\mathrm{Ni}\)\(>\)\(\mathrm{Cr}\)\(>\)\(\mathrm{Pb}\)\(>\) Cd. The variation of heavy metal concentration in the study area was due to irrigation of land by industrial wastewater and other agronomic practices. The higher standard deviation reveals higher variations in heavy metal distributions from the point source of discharge to the adjacent areas. The low concentration of heavy metals in the soil may be ascribed to its continuous removal by vegetables grown in the designated areas. Among the different metals examined in soil, the concentration of Fe was the maximum and variation in its concentration was several times higher than those reported by [PERSON] _et al_. [30]. Average concentration of metals during the dry season in the surface layer of the soil is higher than that in the wet season. The highest deposition of Fe (Figure 2) in soil might be due to its long-term use in the production of machine tools, paints, pigments, and alloying in various industries of the study area that may result in contamination of the soil and a change to the soil structure thus making it risky for use in cultivation [31]. Mn is one of the commonly found elements in the lithosphere and its concentration in the dry season was about two times higher than in the wet season (Figure 3). Cu was distributed uniformly in the wet season, but in the dry some zigzag was found. This metal was about 1.5 times higher in the dry season compared to the wet (Figure 3). There was a sharp variation in average Cu concentration in the dry season at sampling point 8 due to point source contamination. More or less the average concentration of the metal was within the MAC of elements in agricultural soil found in China [34], and within the safe limit of India [35]. Cu content of soils in the Gebze region was between 7.87 and 725 mg/kg with an average of 95.88 mg/kg which was significantly greater than that in uncontaminated soils [32]. In some other works, Cu concentrations lower than in Gebze soils were recorded [33, 36]. Zn and Cr are heavy metals and their sources in industrial locations are usually anthropogenic [38]. The main anthropogenic sources of Zn are related to the non-ferric metal industry and agricultural practice [32, 33]. Zinc is a very readily mobile element. High doses of Zn show toxic and carcinogenic effects and result in neurologic and hematological complications, hypertension, and kidney and liver function disorders [39]. The Cr content of topsoil is known to increase due to pollution from various sources of which the main ones are attributable to industrial wastes such as Cr pigment and tannery wastes, electroplating sludge, leather manufacturing wastes, and municipal sewage sludge _etc._ Cr behavior in soil is controlled by soil pH and redox potential, while long term exposure to Cr can cause liver and kidney damage [38]. The observed Zn and Cr concentrations in studied soil around DEPZ probably comes from construction materials in the form of alloys for protective coating for iron and steel.