Decline in nitrogen concentrations of eutrophic Lake Dianchi associated with policy interventions during 2002–2018. (1st November 2021)

• Record Type: Journal Article
• Authors: Liu, Yong; Jiang, Qingsong; Sun, Yanxin; Jian, Yiwei; Zhou, Feng
• Is Part Of: Environmental pollution. Volume 288(2021)
• Publication Date: 2021-11-01
• Subjects: Nitrogen -- Nutrient cycling -- Lake eutrophication -- Water quality model -- Mitigation measures; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2021.117826
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Excessive nutrient discharges have resulted in pervasive water pollution and aquatic eutrophication. China has made massive efforts to improve water quality since 2000. However, how long-term policy interventions govern external and internal fluxes as well as nitrogen (N) concentrations is not well known. Here we examined the historical N concentration change and its key drivers in eutrophic Lake Dianchi (southwest China) over the period 2002–2018, based on monthly observations of water quality and external N fluxes, local surveys of mitigation measures, and process-based model simulations of internal N fluxes. Our data indicated that N concentrations peaked at 3.0 mg L −1 in 2007–2010 but afterwards declined down to 1.2 mg L −1 in 2018. Compared with 2010, the decline in lake N concentrations was attributed to reduced riverine N inflow decreasing by 0.20 g N m −3 month −1 and the water-sediment exchange flux decreasing by 0.07 g N m −3 month −1 from 2010 to 2018. Adoptions of wastewater treatment, pollution interception, and transboundary water transfer dominated the changes in external and internal fluxes of N and thereby the decline of lake N concentrations. These findings underscore the priority of reducing external discharge for historical lake water quality improvement and the need of enhancing internal N removal for future lake ecosystem restoration. Graphical abstract: Image 1 Highlights: N concentration trend and its key drivers were examined in Lake Dianchi. Decline in N concentration was attributed to reduced external discharge. Reduced external fluxes induced positive but asymmetrical feedback of internal ones. Transboundary water transfer promoted a faster internal removal of N. Abstract : Decline in Lake Dianchi N concentrations was attributed to reduced external discharges and enhanced internal removal associated with long-term policy interventions.