# Microplastics in irrigation water and vegetable garden soils adjacent to the Msimbazi river, Tanzania

## TL;DR

This study finds high levels of microplastics in irrigation water and soils near the Msimbazi River in Tanzania, highlighting environmental risks and the need for better waste management.

## Contribution

First study to examine microplastics in both the Msimbazi River water and adjacent vegetable garden soils.

## Key findings

- Downstream Msimbazi River water had significantly higher microplastic concentrations than upstream Sukita.
- Msimbazi garden soils contained more microplastics than Sukita garden soils.
- Common polymers like LDPE and PP were identified, linked to single-use and reusable plastic bags.

## Abstract

Microplastics (MPs) are present in significant quantities across various environments; however, their persistence and detrimental effects on terrestrial and aquatic ecosystems remain poorly understood. This study has examined MPs in water from the Msimbazi River, used for irrigation, and from soils of nearby vegetable gardens. The results indicate a higher concentration of MPs downstream in the Msimbazi (14.33 ± 2.92 MPs per 10 mL of water) compared to upstream at Sukita (8.49 ± 2.47 MPs per 10 mL of water). A significant difference in MPs abundance was observed between the water samples collected from Sukita and Msimbazi sites (two-sample t-test, degrees of freedom (df) = 62, P < 0.001). Conversely, soil from Sukita gardens exhibited a lower abundance of MPs (28.00 ± 4.25 MPs per g of soil) compared to soils from Msimbazi gardens, which contained (34 ± 5.79 MPs per g of soil). Additionally, a significant difference in MPs concentration was found between soils from vegetable gardens in Sukita and Msimbazi (two-sample t-test, df = 62, P < 0.0001). Attenuated reflection transform infrared spectroscopy identified common plastic polymers from water and soil samples, including polyethylene terephthalate, low-density polyethylene (LDPE), polypropylene (PP), and polyesters. The results provide crucial insights into the abundance of LDPE (18.70–21.20%) and PP (20.50–22.10%) in the Msimbazi River water and soil of the adjacent vegetable gardens, respectively. These findings underscore the potential danger of MPs to the environment and the urgent need for better waste management strategies.

The online version contains supplementary material available at 10.1007/s42452-025-07742-3.

First study to examine the co-occurrence of microplastics (MPs) in the water of the Msimbazi River and the soils of nearby vegetable gardens.

Primary source of microplastics (MPs) to the soil in vegetable gardens.

A microplastics (MPs) hub from multiple pathways, containing a large amount of microplastics (MPs), up to 44,300/Kg.

The study has identified the predominant microplastic polymers linked to single-use plastic bags (LDPE) and reusable bags (PP) in both water and soil.

The study highlights the vital role of the authorities in ensuring clean and safe spaces for urban vegetable farming.

The online version contains supplementary material available at 10.1007/s42452-025-07742-3.