Source Apportionment of Heavy Metal Contaminated Soil Around a Urea Fertilizer Factory and Probabilistic Risk Assessment of Human Health

14 The mean concentrations of heavy metals viz: K, Ca, Mg, Ti, Fe, Co, Cu, As, Zn, Rb, Sr, Zr, Pb and Th were 15 measured in soil samples using Energy Dispersive X-ray Fluorescence (EDXRF) technique and sampling sites as a 16 whole were found highly contaminated by Zn, considerably contaminated by Mg and Pb, while moderately 17 contaminated by Fe, Co, Cu, Rb, Sr, As, Rb, Y, Th. The sampling sites are moderate to strongly polluted by heavy 18 metals according to Enrichment factors value, whereas, Pollution Load Index values for 95% of the sample sites 19 were ≥1.5, indicating deterioration of soil quality. Potential Ecological risk (RI) value followed the increasing 20 sequence of Pb>As>Co>Zn>Cu. Non-carcinogenic exposure found higher in children compared to adults,however 21 carcinogenic risk assessment revealed that both groups (adult and children) lied within Grade II category (10 to 22 10) and considered to be at no risk. 23


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Fertilizers are applied to increase and enhance the crop yield and ensure healthy produce by appropriate balance of 36 nutrient to the soil. Exact balance of fertilizer helps in soil quality depletion and hence helps in proper growth of 37 plant. Basically fertilizers are chemical substances that promotes the crop productivity by supplying nitrogen, 38 potassium and phosphorous and enhance the water retention capacity of the soil, increase soil fertility as 39 well.Among different types of chemical fertilizers urea is the most important nitrogenous fertilizer to improve the 40 quality of soil providing nitrogen to increase the yield of crops.Soil is a complex matrix that can absorb pollutants 41 like metals (Hamaker et al.1972 and Thompson et al. 1972), which becomes common across the globe due to 42 increase in geologic and anthropogenic activities. Emission and waste disposal from rapidly expanding industrial 43 areas, coal combustion, use of chemical fertilizer, waste water irrigation, domestic wastes are known to be 44 responsible for the release of heavy metals into the soil, leaving behind lasting effects for years (Fusion et al. 1999), 45 since they are environmentally stable, non-biodegradable, and tend to cause accumulation in soils. In addition to 46 anthropogenic sources, toxic pollutants may be derived from other sources such as the weathering of naturally high 47 background rocks and metal deposits (Senesi et al. 1999).When the surface soils are contaminated, they 48 consequently serve as a transmitter of pollutants to surface water, groundwater, atmosphere, and food. Excessive 49 accumulation of heavy metals in soil may not only result in soil pollution or contamination, but can also lead to 50 elevate heavy metal (HM) uptake by plants, and thus affect food quality and safety (Muchuweti et al. 2006).

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Therefore heavy metal accumulation in soil is of increasing concern as it ultimately becomes the potential source of 52 human health risks (Singh et al. 2010). This problem has been focused by many researchers and widely reported

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The Jamuna Fertilizer Company Ltd. Jamalpur of Bangladesh produces Urea fertilizer, contributing significantly to 59 meet the demand for urea fertilizer of the country from years. The main raw materials used are the natural gas, 60 differentchemicals like Fe2O3, Fe3O4, Al2O3, K2O, CaO, and SiO2etc. However the factory dischargesthe 3 liquidwastes to the nearby lands which finally go to the Jamuna River and to the adjacent agricultural lands. In this 62 way, the soil gets contaminated and causes toxicity to the public thereafter when the land isused for agricultural 63 cultivation. A vast investigation therefore needed to understand the present heavy metal status of that area, their 64 potential sources as well as impact on human health.The present study was sketched to determine qualitatively and 65 quantitatively the concentrations of heavy metals (Mg, K, Ca, Ti, Fe, Co, Cu, Zn, As, Rb, Sr, Zr, Pb and Th)in the 66 near-surface (~0-20 cm) soils around theJamuna Fertilizer Company Ltd., area using Energy Dispersive X-ray 67 fluorescence spectrometry (EDXRF) and to assess the extent of pollution by calculating some contamination indices 68 and ecological risk assessment . To find outthe possible sources statistical analysis like Pearson correlation,

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Principal Component Analysis (PCA) has been done and the impact on direct human exposure via inhalation, 70 ingestion and dermal contact of soil dust evaluated as well.

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The North-East side of 'The Jamuna Fertilizer Co. Ltd.Jamalpur of Bangladesh (geographical coordinates are at 24° 74 59' 0" North, 90° 6' 0" East), a residential cum agricultural field area,was selected as the study area and soil samples

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A total of 20 soilsamples were collectedfrom different places of the sampling siteusing stainless-steel specula at 81 regular intervals of 2 m at specific transects and labeled as soil-1 to soil-20. The soil samples after collection were 82 sieved with a stainless steel sieve to remove dirt and plant materials. Samples were then separately taken into 83 porcelain dishes and placed in an oven at around 70ºC for complete drying. Each driedsample wasgrounded to fine 84 powder using a mortar and pestle and preserved in a distinctly marked plastic vial inside a desiccator. The 85 homogeneous powder was used to prepare pellet (7mm dia. and 1mm thick) using 10 ton pressure by a pellet maker 86 (Specac, UK) for elemental analysis by EDXRF.

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The sample irradiation was performed using Energy Dispersive X-ray Fluorescence (EDXRF) Spectroscopy System.

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The entire process is done following (Shirin et al. 2019).The X-Ray beam of 22.4 keV from 109 Cd point source hits 90 the target sample to produce the characteristic X-rays, the [Si (Li)] detector (Canberra) having the resolution of 91 175eV at 5.9 keVdetects the characteristic X-rays, which are ultimately converted into voltage pulses and amplified 92 by the spectroscopy amplifier and then finallyprocessed in MCA having16K + channel.The irradiation and spectrum

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The expression of Pi is as follow: where Pi is the single factor index of individual metal, Ci represents the actual measured concentration of metals in     Dermal Contact with Soil is calculated thus;

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Where, ADDdermal is the exposure dose via dermal contact in mg/kg/day. C represents the concentration of heavy 224 metal in soil in mg/kg, SA stands for exposed skin area in cm 2 . SL, adherence factor in mg.cm -2 day -1 ; and ABS, the 225 fraction of the applied dose absorbed across the skin, unitless. EF, ED, BW, CF, and AT are as defined earlier in 226 Equation (2). Table 2 shows the exposure parameters, used for health risk assessment of standard residential 227 exposure scenario through different exposure pathways.

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Heavy metal abundance in and around fertilizer factory soil

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The results of heavy metal concentrations for each sampling site in soil presented in Table 3     The total variance in each factor was calculated as the sum of the squared loadings for the given factor. The scree 274 plot (Fig.2) (Fig.3). The first principal component PC1 is highly loaded with Rb, Ti, Fe,

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EF value of all heavy metals were reported to be<2 at all sampling sites (Fig.6) but Ti showed moderate enrichment 300 in the area as it remains between 2 and 5 thus can be severe in the near future so regular monitoring is necessary.

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Sampling point Soil-1is moderately contaminated by Mg, Fe, As, Zn. Cu, Sr Y, Thbut the contamination level of 303 Al, K, Ca, Co, Ti and Co is very low (Table 5)

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Thecarcinogenic risk due to the four heavy metals Cu, Zn, As and Pb has been calculated for both the adults and 356 children population (Table 9), from where it is evident that children are more vulnerable than adults and the risk 357 factor of As is much higher than Pb in case of children.The total carcinogenic risk factor for children is 7.762×10 -6 358 which is less than the acceptablecarcinogenic value range (Risk<10 -4 ) and as the risk value lies within (10 -6 to10 -5 ),

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according to (Li et al.2017) it has been considered as Grade II (Low risk) and hence there is no need to wary about 14 the risk.The total carcinogenic risk factor for adults is 3.326×10 -6 which is within the acceptable range (Risk<10 -4 ) 361 and did not pose a carcinogenic risk to the population group.  do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.   The degree of metal pollution of soil samples according to the Geo-accumulation index (Igeo). Pollution Load Index (PLI) of soil of Jamuna fertilizer area