Sediment denitrification and nitrous oxide production in Chinese plateau lakes with varying watershed land uses

Abstract

Denitrification in lake sediments removes nitrogen and releases N2O to the atmosphere, contributing to global warming. However, the rates and controls of sediment denitrification and N2O production are still poorly understood in lakes. In this study, we measured potential denitrification, unamended denitrification and N2O production rate in sediments which were collected from 68 sites in 20 Chinese plateau lakes of varying watershed land uses. The result showed that potential denitrification rate of human-dominated lakes (37.94 ± 8.91 ng N g−1 h−1) was significantly higher than that of reference lakes (18.50 ± 3.22 ng N g−1 h−1). In addition, potential denitrification rate was positively related to the proportion of human land uses in watersheds. At the lake level, unamended denitrification and N2O production rates were significantly related to water chemistry or sediment properties (e.g., conductivity and sediment total nitrogen). Water chemistry and sediment properties together accounted for 0–69 % of the variance in denitrification and N2O production rates. Variance partitioning showed that unamended denitrification and N2O production rates in human-dominated lakes were controlled primarily by sediment properties, while in reference lakes were generally controlled by water chemistry. Our findings suggest that Chinese plateau lakes can remove large quantities of nitrogen through sediment denitrification and produce small amounts of N2O. The relative contributions of water chemistry and sediment properties to the lake denitrification and N2O production vary widely.