Nutrient inputs from the leaf decay of Cynodon dactylon (L.) Pers in the water level fluctuation zone of a Three Gorges tributary

Xi Chen; Shuai Zhang; Dan Liu; Zhiguo Yu; Shuang Zhou; Ruijuan Li; Zhengxue Liu; Junjie Lin

doi:10.1016/j.scitotenv.2019.06.357

Nutrient inputs from the leaf decay of Cynodon dactylon (L.) Pers in the water level fluctuation zone of a Three Gorges tributary

Sci Total Environ. 2019 Oct 20:688:718-723. doi: 10.1016/j.scitotenv.2019.06.357. Epub 2019 Jun 24.

Authors

Xi Chen¹, Shuai Zhang¹, Dan Liu², Zhiguo Yu³, Shuang Zhou¹, Ruijuan Li⁴, Zhengxue Liu¹, Junjie Lin⁵

Affiliations

¹ Key Laboratory of Water Environment Evolution and Pollution Control in Three Gorges Reservoir, Chongqing Three Gorges University, Chongqing 404100, China.
² Department of Agricultural and Forestry Science and Technology, Chongqing Three Gorges Vocation College, Chongqing 404000, China.
³ School of Hydrology and Water Resources, Nanjing University of Information Science and Technology, Nanjing 210044, China.
⁴ Jilin Jinrun Environmental Technology Service Co., Ltd., Jilin 130000, China.
⁵ Key Laboratory of Water Environment Evolution and Pollution Control in Three Gorges Reservoir, Chongqing Three Gorges University, Chongqing 404100, China. Electronic address: ybu_lin@126.com.

PMID: 31255809
DOI: 10.1016/j.scitotenv.2019.06.357

Abstract

Cynodon dactylon (L.) Pers (C. dactylon) is one of the dominant plants in the water level fluctuation (WLF) zone of the Three Gorges Reservoir (TGR) tributaries. However, the leaves of C. dactylon can decay to increase the inputs of nutrients under flood inundation, increasing the risk of eutrophication in the TGR tributaries. Nutrient inputs from the leaf decay of C. dactylon in three interfaces, namely, water-sediment (WS), water-C. dactylon (WC) and water-sediment-C. dactylon (W-S-C), were estimated in a 180 d inundation experiment. The results showed that the kinetic processes of total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) input accorded with the power function equation: y = ax^b for the WS, WC and W-S-C interfaces (R²s > 0.72, p < 0.001). The cumulative TDN input from leaf decay of C. dactylon in the WC interface was 506.44 mg N kg^-1 of biomass, which was significantly higher than that in the W-S-C interface with 422.24 mg N kg^-1 of biomass (p < 0.05). However, no significant differences in TDP input were found between the WC and W-S-C interfaces (p > 0.05). The total amounts of TDN and TDP inputs at the 165-175 m altitude were 21,688.81 and 13,121.68 kg year^-1, respectively, which were approximately 3.17 times those from the 145-155 m altitude of the WLF zone. The amounts of TDN and TDP inputs from the leaves of C. dactylon for the whole WLF zone were 49,261.65 and 29,803.17 kg year^-1, respectively, which were 0.1 and 2.7 times the annual permissible discharge amount of pollutants calculated from a municipal wastewater treatment plant with the peak flow of 60,000 m³/d according to Class I (A) of the Wastewater Discharge Standard (GB18918-2002) in China. Thus, the aboveground part of this perennial herb should be harvested in a timely manner before reflooding, especially at the higher altitudes of the WLF zone to decrease eutrophication risk.

Keywords: Eutrophication; Three Gorges reservoir; Total dissolved nitrogen; Total dissolved phosphorus; Water level fluctuating zone.

MeSH terms

China
Cynodon*
Environmental Monitoring
Nitrogen / analysis*
Phosphorus / analysis*
Plant Leaves*
Rivers
Water Pollutants, Chemical / analysis*

Substances

Water Pollutants, Chemical
Phosphorus
Nitrogen