Nitrate in groundwater and agricultural products: intake and risk assessment in northeastern Iran

Abstract

The suitability of groundwater and agricultural products for human consumption requires determining levels and assessing the health risks associated with potential pollutants. Here, particularly pollution with nitrate still remains a challenge, especially for those urban areas suffering from insufficient sewage collection systems, resulting in contaminating soil, endangering food safety, and deteriorating drinking water quality. In the present study, nitrate concentrations in the commonly consumed fruit and vegetable species were determined, and the results, together with the groundwater nitrate levels, were used to assess the associated health risks for Mashhad city residents. For this assessment, 261 water samples and 16 produce types were used to compute the daily intake of nitrate. Nitrate in groundwater was analyzed using a spectrophotometer, and produce species were examined using High-Performance Liquid Chromatography. Ward’s hierarchical cluster analysis was applied for categorizing produce samples with regard to their nitrate content. Additionally, to account for the sanitation hazards associated with groundwater quality for drinking purposes, total coliform and turbidity were also assessed using the membrane filter (MF) technique and a nephelometer, respectively. Nitrate concentrations exceeded the prescribed permissible limits in 42% of the groundwater wells. The outcomes also exhibit significantly higher nitrate accumulation levels in root-tuber vegetables and leafy vegetables compared to fruit vegetables and fruits. Using cluster analysis, the accumulation of nitrate in vegetables and fruits was categorized into four clusters, specifying that radish contributes to 65.8% of the total content of nitrate in all samples. The Estimated Daily Intake (EDI) of nitrate and Health Risk Index (HRI) associated with consumption of groundwater exceeded the prescribed limit for the children’s target group in Mashhad’s south and central parts. Likewise, EDI and HRI values for produce consumption, in most samples, were found to be in the tolerable range, except for radish, lettuce, and cabbage, potentially posing risks for both children and adult consumers. The total coliforms in groundwater were found to violate the prescribed limit at 78.93% of the sampling locations and were generally much higher over the city’s central and southern areas. A relatively strong correlation (R2 = 0.6307) between total coliform and nitrate concentrations suggests the release of anthropogenic pollution (i.e., sewage and manure) in the central and southern Mashhad.

Human health risk of nitrate in groundwater of Tehran–Karaj plain, Iran

“…These studies further confirm our findings about the concern on high levels of nitrate in some regions of Tehran–Karaj aquifer. Using the groundwater samples taken in west of Tehran city in 2016, Shirazi et al 77 reported no concern about the elevated concentration of nitrate in this region—a finding that is in-line with our results as shown in Fig. 4 .…”

Health Risk Assessment of Nitrate in Drinking Water with Potential Source Identification: A Case Study in Almaty, Kazakhstan

“…This characteristic suggests that when Cl − is higher than the NO3 − /Cl − ratio, nitrate pollution is related to domestic effluent and sewage, whereas reverse ratios are typically related to precipitation/fertilizers [54]. The approach A strong correlation between nitrate and other anions (such as chloride, phosphate, and sulfate) was found in earlier studies [42], suggesting that these pollutants come from the same source such as sewage water leaks into the groundwater. Elevated nitrate concentrations in tap water could be related to domestic sewage due to the poor condition of water pipes and insufficient wastewater treatment [40,43].…”

“…Numerous studies [18,20,51,52] have used stable isotope analysis, such as dual nitrogen and oxygen isotope ratios of nitrate, to identify nitrate pollution sources. Also, the sources of nitrate contamination in water have been found using relationships between nitrate, nitrite, ammonium, and chloride [42,53]. According to Liu et al [54], chloride is not affected by physicochemical or microbiological processes that take place in groundwater, making it useful as a sewage impact indicator.…”

“…Consequently, better management of sanitation facilities is critical to reduce nitrate concentrations in the groundwater [47]. Improving and expanding sewage collection networks and wastewater treatment systems should be prioritized to improve groundwater quality [42,47,48]. It has been observed that specific districts of Almaty (Alatau, Auezov, and Nauryzbay) have high concentrations of nitrate where local inhabitants have constructed improper sewage tanks that leak into the soil and contaminate the groundwater [27].…”

Groundwater quality in coastal area: A case study in Parangtritis Village, Bantul, Yogyakarta, Indonesia

“…Escherichia coli (E. coli) was used as an indicator of groundwater quality as its presence indicates fecal contamination (Febriarta, 2020;Sejati, 2020;Zendehbad, Mostaghelchi, Mojganfar, Cepuder, & Loiskandl, 2022). Table 5 shows the results of the E. coli test for groundwater samples with the standards for E. coli bacteria for sanitation hygiene purposes are explained in the rightmost column in the table.…”