A study conducted by a team of scientists from Ghana, Canada, and Nigeria has revealed that manure applied to farmlands to improve crop yields is contributing to high concentrations of nitrate in groundwater.

The research, conducted in agricultural communities in the Upper West Region of Ghana, found that organic manure from cattle grazing, open defecation, and other sources accounted for about 74 per cent of the nitrate contamination in the affected groundwater.

The study focused on 98 communities, with nine communities—including Charia, Nyayiri, Sankana, Moyiri, Nadowli, Tampoe, Gball, Jeffisi, and Gbelle—showing significantly higher nitrate levels than the World Health Organization’s (WHO) recommended limit of 50 milligrams per liter.

In these areas, nitrate concentrations exceeded the WHO safety threshold, raising serious health concerns, particularly for infants who are at greater risk from nitrate contamination.

The research was led by Ms. Priscilla Lartsey, a PhD candidate at the University of Ghana, and an International Atomic Energy Agency (IAEA) Fellow at Université du Québec à Montréal (UQAM).

Other contributors to the study include Samuel Y. Ganyaglo, Dickson Adomako, Patrick Asamoah Sakyi, Abass Gibrilla, Florent Barbecot, Karine Lefebvre, and Etuk Mary Nsikanabasi.

The study, sponsored by the IAEA and the Ghana Atomic Energy Commission, began in 2019 with a field campaign to collect groundwater and surface water samples from the Black Volta River in Ghana’s Upper West Region.

During the campaign, scientists measured various physical and chemical parameters, including pH, Electrical Conductivity (EC), temperature, alkalinity, and Total Dissolved Solids (TDS).

The samples were collected according to specific protocols required for analyzing major ions, stable isotopes of water, and stable isotopes of nitrate.

Lead researcher Ms. Lartsey explained to the Ghana News Agency that continued consumption of water from wells in the nine affected communities, where nitrate levels are high, could pose a risk to infants, potentially leading to a condition known as methemoglobinemia.

Methemoglobinemia is a blood disorder that occurs when there is excessive methemoglobin in the blood, a form of haemoglobin that cannot transport oxygen. This lack of oxygen delivery to tissues can result in severe, life-threatening health issues.

“Nitrate is known to be an important component of fertilisers and some rocks. This element when found in elevated concentrations beyond the WHO limit can be detrimental to the health and lead to a disease called methemoglobinemia,” she said.

Ms Lartsey recommended the continuous sensitisation of farmers on the appropriate location to carry out agricultural activities to reduce contamination of groundwater resources.

“For instance, special ponds should be constructed for cattle grazing away from faulty well heads to prevent manure from contaminating groundwater directly,” she said.

The scientists said the nitrate contamination of groundwater was mainly found at the discharge areas of groundwater resources, which could be better managed than at the recharge areas or upstream that recorded low levels of nitrate contamination.