Elsevier

Environmental Research

Volume 205, 1 April 2022, 112527
Environmental Research

Accumulation and human health risk assessment of nitrate in vegetables irrigated with different irrigation water sources- transfer evaluation of nitrate from soil to vegetables

https://doi.org/10.1016/j.envres.2021.112527Get rights and content

Highlights

  • The aim of this study is the effect of irrigation sources on the nitrate of vegetables.

  • The ADI of nitrate in all irrigated vegetables is less than the allowable level.

  • The Gharasoo River, causes more nitrate accumulation in the soil and vegetables.

  • TWE is the best irrigation source for vegetable cultivation in Kermanshah.

Abstract

The present study aimed to investigate the rate of accumulation, human health risk assessment, and nitrate-related transfer factor in vegetables irrigated with different sources, including treated wastewater effluent (TWE) of Kermanshah wastewater treatment plant, Gharasoo river water (RW) of Kermanshah, and well water with chemical fertilizer (WWF). For this purpose, three different types of vegetables, including basil, coriander, and radish, was cultivated, and each of them was irrigated by the three irrigation sources mentioned above. Finally, the amount of nitrate in different sources of irrigation, soil (before growing vegetables and after harvesting vegetables), and the mentioned vegetables was measured. Based on the study results, it can be concluded that the water of the Gharasoo River (RW), compared to the other two irrigation sources, causes more nitrate accumulation in the soil and vegetables grown in it. The highest transmission factor was related to basil vegetables irrigated with WWF. The results showed that the average daily intake of nitrate through the consumption of vegetables grown in Kermanshah with any irrigation water is less than the allowable amount, so the consumption of such vegetables is not dangerous to consumers' health. Therefore, it is suggested that the best irrigation source for vegetable cultivation in Kermanshah is TWE, provided that all of its physical, chemical and microbial parameters meet the standards for reuse in agriculture irrigation. Thus, the use of treated wastewater reduces the need for farmers to use chemical and organic fertilizers and cost-effectiveness, high frequency, and high availability.

Introduction

Nitrate and nitrite are present in a wide range of foods and water resources (Chung et al., 2003; Meah et al., 1994; Ahmed et al., 2020a, 2020b). Nitrate is usually found naturally in leafy vegetables, and nitrite is generally added to meat as a preservative in the form of nitrite salts (Cammack et al., 1999). Nitrate does not pose much risk to human health, but it can easily be reduced to nitrite in the mouth and stomach. Nitrite in the gut can then react with secondary amines to form carcinogenic N-nitrosamines (WHO, 1989). Furthermore, due to the high affinity of nitrite for hemoglobin in the blood, it can combine vigorously to form methemoglobinemia, which is also known as a blue baby syndrome and has a high potential for toxicity in children (Knobeloch et al., 2000; Ward et al., 2018; Hickey et al., 2021). Based on clinical and epidemiological studies, high nitrite and nitrate levels in the diet cause gastric cancer (Joossens et al., 1996). Moreover, exposure to N-nitrosamine compounds formed in the stomach has increased esophageal and gallbladder cancer (Bartsch et al., 1990).

High nitrate levels in the diet have been linked to gastric cancer in the United Kingdom, Colombia, Chile, Japan, Denmark, Hungary, and Italy (Wong et al., 2004). However, the amount of nitrate and nitrite in the diet varies significantly from region to region. This variation depends on the repetition of cultivation, and other factors, including weather factors, soil quality of the agricultural production site, food production processes, chemical fertilizer type and quantity, irrigation source type, and local rules (Hsu et al., 2009).

Today, in most parts of the world, using treated wastewater and rivers for irrigation is critical to preventing the overuse of groundwater in agriculture (Lavrnić et al., 2017). However, in some countries, the use of sewage and river water for irrigation is uncontrolled. This causes the transfer of many toxic pollutants to the soil and irrigation products, with nitrate being one of the most critical pollutants in this process (Ahmadi-Jouibari et al., 2021; Manas et al., 2009; Minhas and Yadav, 2015).

There are usually three primary sources for agricultural products' irrigation: groundwater, surface water such as rivers, and treated wastewater as alternative sources (Ahmadi-Jouibari et al., 2021; Mandal et al., 2019; Minhas et al., 2019). Moreover, various chemical and organic fertilizers are sometimes used to increase soil fertility and thus increase the growth of agricultural products and surface water and groundwater (Bergström and Brink, 1986; Sebilo et al., 2013).

Kermanshah province is one of the leading agricultural hubs, especially for the cultivation of edible vegetables in the west of Iran, facing water shortage and the problem of using groundwater (through digging deep wells). Consequently, farmers in this province have to use other water resources such as rivers and various sewages (Ahmadi-Jouibari et al., 2021; Doabi et al., 2018). Typically, Iranian farmers are unconcerned with each irrigation source's amount and type of contamination transmitted to vegetables. Researchers should think about this as one of the health and environmental concerns.

Due to the reasons mentioned above, the primary purpose of this study was to evaluate the effect of three different irrigation sources, including WWF (first source), TWE (second source), and RW (third source), on nitrate accumulation in soil and three types of cultivated vegetables included coriander, basil, and radish. Moreover, the risk of nitrate-related human health was assessed by consuming the above-mentioned edible vegetable and the rate of transferring nitrate factor from soil to vegetable. Based on our best knowledge, there are limited global concurrent studies on soil and vegetable pollution effects of three types of irrigation sources in nitrate and health risk assessments and nitrate transfer factors. Therefore, the results of this study will help, support, and be used to design similar future studies.

Section snippets

Study design

For this study, a 36-square-meter plot of agricultural land near Kermanshah's wastewater treatment plant was selected and divided into nine portions (P) equal to 2 × 2 (4 square meters) (Fig. 1). In this study, three types of vegetables containing coriander cultivated in parts (P1, P4, P7), basil, and radish were cultured in (P2, P5, P8), and (P3, P6, P9) part, respectively, and irrigated with three different water sources. Furthermore, each cultivated land part was evaluated for a particular

Nitrate in irrigation water and soil

Based on the results, the average amount of nitrate in the soil samples was from highest to lowest concentration as SWI˂SWWF˂STWE˂SRW (Fig. 2), and the observed difference was statistically significant (Table 2). In terms of mean nitrate content, from highest to lowest concentration was RW > WW < TWE (Fig. 2), and statistically, the difference observed between all three types of irrigation was significantly different (Table 2).

The statistical analysis results showed that all three irrigation

Conclusion

Based on the study results, it can be concluded that the water of RW compared to two other irrigation sources, including TWE and WWF, causes more nitrate accumulation in the soil and vegetables grown in it. The highest transmission factor was related to basil vegetables irrigated with well water and fertilizer. However, the results showed that the average daily nitrate intake through the consumption of vegetables grown in Kermanshah with any irrigation water is less than the allowable amount,

Author contributions section

Kiomars Sharafi: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Writing – original draft, Writing – review & editing, Visualization, Supervision, Project administration, Funding acquisition. and Ehsan Ahmadi: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Writing – original draft, Writing – review & editing, Visualization, Supervision, Project administration, Funding acquisition. Amir Kiani: Conceptualization, Methodology, Validation,

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

The authors gratefully acknowledge the Research Council of Kermanshah University of Medical Sciences (Grant Numbers: 990931 and 990606) for financial support. Also, the authors appreciate the personnel of the Kermanshah province water and wastewater company for their cooperation in the analysis of samples.

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