Control factors on Nutrient Cycling in the Lake Water and Groundwater of the Badain Jaran Desert, China

Abstract

Saline lakes are characterized by high salinity and limited biological diversity. The nutrient cycle directly determines biological diversity. Many factors including internal loading, riverine inflows, salinity, and/or anthropogenic activities affect the nutrient cycle in saline lakes. The Badain Jaran Desert (BJD) is featured by hyper-arid climate and by mega sand dune-lake landscapes. In this study, nutrients in groundwater and lake water in the BJD were analyzed to explore the control factors on the nutrient cycle. Results show that 76% of the lakes are nitrogen-limited and the rests are phosphorus-limited, 56% of lakeside groundwater samples are phosphorus-limited and the rests nitrogen-limited, and most of the well water in the mountain area surrounding the BJD is phosphorus-limited. The lake water in the BJD is mainly supported by mountain block recharge and local groundwater, but nutrients in lake water are mainly supplied by the mountain block recharge and lakebed diffusion. Lakebed diffusion delivers up to 70% total ammonium and 97.6% total orthophosphate to the lake water, while mountain block recharge accounts for about 72% nitrate/nitrite and about 73% silicate to the lake water. Nutrients in local groundwater systems are highly variable due to the complexity of hydrological and hydrogeochemical conditions (rainfall, precipitation/dissolution, and redox reaction). This study systematically investigates the control factors on the nutrient structure and cycle in groundwater and lake water in the BJD. The findings of this study will be constructive to explore the nutrient cycle in saline lakes worldwide with similar hydrogeological conditions.