Stable isotopic composition of precipitation in a tropical rainforest region of the Niger Delta, Nigeria

ABSTRACT

The isotopic compositions of oxygen (δ¹⁸O) and hydrogen (δ²H) of precipitation were determined from three different locations in the western Niger Delta (Warri, Ughelli and Abraka) between 2014 and 2015. ¹⁸O and ²H in wet season precipitation were more depleted compared to the dry season. Similarly, d-excess computed for wet season precipitation is lower than that for the dry season. The δ¹⁸O and δ²H variations in precipitation suggest the effect of the convective system and north-easterly and south-westerly trade winds. The decrease in δ¹⁸O and δ²H was also observed in precipitation data of a continuous rain event of two successive days. The local meteoric water lines estimated for Warri, Ughelli and Abraka were δ²H = 8.8 δ¹⁸O + 9.1 ‰ (R² = 0.93), δ²H = 6.9 δ¹⁸O + 10.7 ‰ (R² = 0.98) and δ²H = 7.9 δ¹⁸O + 11.3 ‰ (R² = 0.87), respectively. The Niger Delta regional meteoric water line of δ²H = 7.7 δ¹⁸O + 10.2 ‰ (R² = 0.91) was derived from the monthly average from the three locations. The provided local meteoric water line for the Niger Delta from unweighted stable isotopic data represents a baseline for regional water resources studies.

KEYWORDS:

• Deuterium excess
• hydrogen-2
• isotope hydrology
• meteoric water lines
• Niger Delta region
• Nigeria
• oxygen-18
• precipitation
• trade winds

Disclosure statement

No potential conflict of interest was reported by the author(s).