Iranian Journal of Soil and Water Research

Iranian Journal of Soil and Water Research

Studying the Effect of Microbial and Heavy Metal Contamination on Barley Seed Plants Irrigated with Urban Sewage Effluent

Document Type : Research Paper

Author
Hamid Molahoseini
Soil and Water Research Department, Isfahan Agricultural and Natural Resources Research and Education Center, Agricultural Research,Education and Extension Organization (AREEO), Isfahan, Iran
10.22059/ijswr.2026.414523.670143
Abstract
This study was conducted to investigate the effects of microbial contamination and heavy metals resulting from wastewater effluent irrigation on soil and barley in Isfahan. To statistically evaluate the effects of wastewater on soil and barley plants in terms of heavy metals and microbial contamination, composite soil and plant samples were collected at harvest time for each crop under wastewater and well-water irrigation conditions, with ten samples taken from each treatment and sent to the laboratory for analysis. Statistical analysis of soil and plant results using a paired-samples t-test showed that the concentrations of cadmium, nickel, chromium, cobalt and arsenic in soil and plants did not show significant differences compared with well-water irrigation. The enrichment factor for lead and cadmium in plants was greater than 2, while other metals showed weak enrichment for transfer to roots and aerial plant parts. The bioconcentration factor for lead, cadmium, nickel, chromium, cobalt, and arsenic in aerial plant parts was also less than 1, while the translocation factor for lead was greater than 1 and for other heavy metals under both wastewater and well-water irrigation conditions was less than 1. Microbial contamination, including total coliforms and fecal coliforms in soil and plant samples collected twenty-one days after the last irrigation, showed no significant differences between wastewater and well-water treatments, indicating that microbial contamination was reduced to levels comparable with well-water-irrigated lands after twenty-one days. Therefore, it is recommended that seed harvesting should be carried out at least twenty-one days after the final irrigation event.
Keywords
Agriculture
Bioaccumulation
Heavy elements
Unconventional waters
Subjects

Introduction

Isfahan Province, as one of the arid and semi-arid regions of Iran, is facing a reduction in water resources, and water scarcity has been increasing in this province. This issue has led to the use of unconventional water resources, particularly municipal wastewater effluent, for agricultural irrigation purposes. Improper management in the use of wastewater effluents, in addition to causing health problems and risks for humans and animals, also results in various forms of soil and water resource contamination. Studies have shown that irrigation water containing heavy metals and soil salinity are among the important environmental factors that have significant effects on barley yield, growth, and salt uptake. Irrigation with wastewater (treated or untreated) may lead to the accumulation of heavy metals in the soil as well as in different parts of barley, including grains, shoots, and roots. Such accumulation may affect barley growth and development and may pose health risks to consumers. The accumulation of toxic heavy metals in barley depends on various factors, including barley species, the type of heavy metals, and other related factors.

Materials and Methods

Considering the importance of the potential risk of toxic heavy metals and microbial contamination entering the human food chain, the present study was conducted to investigate the effects of microbial contamination and heavy metals resulting from wastewater effluent irrigation on soil and seed barley plants compared with well-water irrigation in Isfahan. For this purpose, following soil and plant sampling, chemical analyses including salinity, pH, organic carbon, concentrations of available nutrients such as nitrogen, potassium, and phosphorus, total concentrations of manganese, iron, zinc, copper, cadmium, lead, nickel, chromium, and cobalt, as well as several microbial analyses including total coliforms, fecal coliforms, Salmonella, Escherichia coli (E. coli), and helminth eggs were performed on the collected samples.

Results and Discussion

The results of this study showed that the wastewater effluent contained approximately 6–8 times higher concentrations of total nitrogen and phosphorus, while chloride, sulfate, calcium–magnesium, sodium, and potassium levels were approximately 5%, 12%, 30%, and 15% lower than, or similar to, those in well water, respectively. Furthermore, the concentrations of cadmium (Cd), cobalt (Co), chromium (Cr), arsenic (As), nickel (Ni), lead (Pb), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), as well as the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) parameters in the wastewater effluent, were below the permissible limits of national and international standards. Regarding microbial contamination, total coliforms, fecal coliforms, and Escherichia coli concentrations exceeded the permissible limits established by the Iranian Department of Environment standards.

The results related to soil and plant samples also indicated that cadmium, nickel, chromium, cobalt, and arsenic concentrations in soil and plants did not differ significantly compared with well-water irrigation. In contrast, lead concentrations in soil showed no significant differences, whereas a significant increase was observed in plant tissues. Based on the enrichment factor results, this parameter for lead and cadmium in plant tissues exceeded 2, indicating that soils irrigated with wastewater exhibited moderate enrichment with respect to lead and cadmium, whereas weak enrichment was observed for the other heavy metals in terms of transfer to roots and aerial plant parts. The bioconcentration factor for lead, cadmium, nickel, chromium, cobalt, and arsenic in aerial plant parts was lower than 1. The translocation factor for lead was greater than 1, whereas the translocation factor for the other heavy metals under both wastewater and well-water irrigation conditions remained below 1. Regarding microbial contamination, no significant differences in total coliforms and fecal coliforms were observed in soil and plant samples between wastewater and well-water treatments. Twenty-one days after the final irrigation event, the differences in total and fecal coliform counts in soil were 0 and 2.5 (MPN/g), respectively, while in aerial plant tissues the differences in total coliforms and fecal coliforms were 1.3 and 0.4 (MPN/g), respectively. These findings indicate the reduction of microbial contamination to levels comparable with those observed in lands irrigated with well water after twenty-one days.

Conclusion

To reduce the effects of wastewater effluent on soil and plants, it is recommended that at least twenty-one days should elapse after the final irrigation event, and that seed harvesting should be carried out thirty days after the last irrigation according to Standard No. 21786. Furthermore, based on the same standard, the entry of animals into the field should be prevented for up to twenty-four hours after the final irrigation event. Therefore, under the current conditions of water scarcity in Isfahan, wastewater effluent with relatively low salinity and the presence of certain nutrient elements may be used for seed barley production, provided that the aforementioned environmental and public health considerations are properly observed.

Funding

Financial support for this research was provided by the private sector, namely the North Espadana Brewery Company, in the form of a research project of the first author.

Authorship contribution

Conceptualization, methodology, software, validation, formal analysis, investigation, resources, data curation, writing—original draft preparation, writing—review and editing, visualization, supervision, project administration: Hamid Molahoseini. The author has read and agreed to the published version of the manuscript.

Declaration of Generative AI and AI-assisted technologies in the writing process

There is no use of any type of artificial intelligence-based technology in this paper.

Data availability statement

Data available on request from the authors.

Acknowledgements

The author would like to thank the esteemed Research Vice President of the Soil and Water Research Institute/Isfahan Province Agricultural and Natural Resources Research and Education Center for their moral support and cooperation in carrying out this research.

The author would like to thank Dr. Maryam Moosavi for reviewing the text of the article and providing structural comments.

The author would like to thank reviewers for their valuable suggestions in manuscript revision.

The author would like to thank Dr. Babak Khayyam Bashi for reading the text of this article and providing valuable comments.

Ethical considerations

The author avoided data fabrication, falsification, and plagiarism, and any form of misconduct.

Conflict of interest

The author declares no conflict of interest.

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Iranian Journal of Soil and Water Research
Volume 57, Issue 7
September 2026
Pages 1745-1764