Urban closed lakes: Nutrient sources, assimilative capacity and pollutant reduction under different precipitation frequencies

Heng Yang; Yong Zhao; Jian-Hua Wang; Wei-Hua Xiao; Jerker Jarsjö; Ya Huang; Yang Liu; Jia-Peng Wu; He-Jia Wang

doi:10.1016/j.scitotenv.2019.134531

Urban closed lakes: Nutrient sources, assimilative capacity and pollutant reduction under different precipitation frequencies

Sci Total Environ. 2020 Jan 15:700:134531. doi: 10.1016/j.scitotenv.2019.134531. Epub 2019 Oct 23.

Authors

Heng Yang¹, Yong Zhao², Jian-Hua Wang³, Wei-Hua Xiao³, Jerker Jarsjö⁴, Ya Huang³, Yang Liu³, Jia-Peng Wu³, He-Jia Wang³

Affiliations

¹ State Key Laboratory of Simulation and Regulation of Water Cycles in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China; Department of Physical Geography, Stockholm University, SE-106 91 Stockholm, Sweden.
² State Key Laboratory of Simulation and Regulation of Water Cycles in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China. Electronic address: zhaoyong@iwhr.com.
³ State Key Laboratory of Simulation and Regulation of Water Cycles in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China.
⁴ Department of Physical Geography, Stockholm University, SE-106 91 Stockholm, Sweden. Electronic address: jerker.jarsjo@natgeo.su.se.

PMID: 31655453
DOI: 10.1016/j.scitotenv.2019.134531

Abstract

Many natural and man-made urban lakes have been developed under urbanization. A unique feature of these lakes is the lack of an outlet; thus, they are defined as urban closed lakes (UCLs). UCLs are facing unexpected eutrophication under climate change and human activities. Our study assessed the trophic state, assimilative capacity (AC) and pollutant reduction of UCLs under different precipitation frequencies in Wuhan, China based on Carlson's Trophic State Index, assimilative capacity modelling, field investigations and observed data. The UCLs in Wuhan are nearly eutrophic in summer. Three primary nutrient sources are atmospheric deposition, pollutants carried in rainfall and nutrients released by sediments. TN and TP in the UCL water column are primarily contributed by surface runoff. The ACs of TN and TP in 2015 for Lingjiao Lake, Yue Lake, and Houxianghe Lake were 3472.07 kg, 13,800.99 kg, and 2805.58 kg, respectively, and 641.66 kg, 8386.79 kg, and 800.14 kg, respectively. The ACs of TN and TP were much higher at a 25% precipitation frequency (wet year) compared with a 50% frequency, and the lowest AC was observed at a 75% precipitation frequency (dry year). A comparison of the pollution load and AC showed that TN and TP reduction was highest in the dry and wet years, respectively. We found that specific meteorological conditions in the early stage led to the algal bloom. These results can facilitate governmental decision making in the future.

Keywords: Assimilative capacity; Pollutant reduction; Precipitation frequency; Trophic status; Urban closed lakes.