Dual isotopes of nitrate in Korean fertilizers and their application for identifying nitrate sources

Abstract

Many studies have used typical ranges of δ 15 N and δ 18 O values to identify nitrate sources. However, it is questionable whether typical nitrate isotopes for various sources can be universally applied. Thus, for inorganic (IOF), organic (OF) and plant-based compound fertilizers (PCF) in South Korea, δ 15 N and δ 18 O were measured to evaluate their commonly used ranges. The δ 15 N and δ 18 O were 2.6 ± 2.5‰ and 19.3 ± 2.6‰ (n = 19) for IOFs, 14.7 ± 7.7‰ and 5.9 ± 4.9‰ (n = 30) for OFs, and 10.9 ± 6.7‰ and 16.0 ± 6.1‰ (n = 24) for PCFs, respectively. Some OFs showed relatively lower δ 15 N than the previously reported values for NO 3 fertilizers but all PCFs had both δ 15 N and δ 18 O similar to them, indicating that δ 15 N and δ 18 O for the organic material-based fertilizers were likely affected by both the composition level of the main ingredients and various additives in them. Dual isotopic data for three types of fertilizer in this study can play a crucial role in in-depth understanding the fate of natural and anthropogenic nitrate sources occurring in watershed.

Dietary homogenization and spatial distributions of carbon, nitrogen, and sulfur isotope ratios in human hair in South Korea

“…Specifically, N isotope values are markedly low in the northern to western inland and high along the southern coast (including the southeastern coast), that is, distinctively low in mountainous areas and high in agricultural areas (Fig 5B). Organic fertilizers such as animal manures (chicken and farmyard manures; δ 15 N = +14.7 ± 7.7 ‰, n = 30) are primarily used in agricultural lands in South Korea [36,58]; thus, the spatial variation of δ 15 N values seems to be related to the consumption of food produced in these areas. Generally, δ 15 N values are also determined by the consumption of fish and meat [1,56,57,59,60] and the high values along the coastal regions are unsurprising, as marine-derived proteins have high δ 15 N values [61,62].…”