Effect of long-term phosphorus addition on the quantity and quality of dissolved organic carbon in a freshwater wetland of Northeast China

Rong Mao; Si-Yue Li; Xin-Hou Zhang; Xian-Wei Wang; Chang-Chun Song

doi:10.1016/j.scitotenv.2017.02.084

Effect of long-term phosphorus addition on the quantity and quality of dissolved organic carbon in a freshwater wetland of Northeast China

Sci Total Environ. 2017 May 15:586:1032-1037. doi: 10.1016/j.scitotenv.2017.02.084. Epub 2017 Feb 16.

Authors

Rong Mao¹, Si-Yue Li², Xin-Hou Zhang³, Xian-Wei Wang³, Chang-Chun Song⁴

Affiliations

¹ Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China. Electronic address: maorong@cigit.ac.cn.
² Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
³ Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China.
⁴ Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China. Electronic address: songcc@neigae.ac.cn.

PMID: 28215795
DOI: 10.1016/j.scitotenv.2017.02.084

Abstract

Understanding how P enrichment alters the quantity and quality of dissolved organic carbon (DOC) is important, because of their role in regulating the C cycle. Here, we established a four-level P addition experiment (0, 1.2, 4.8, and 9.6gPm^-2year^-1) in a N-limited freshwater wetland in the Sanjiang Plain, Northeast China. The aim of this study was to examine the effects of eight years of P addition on DOC concentration, SUVA₂₅₄ (Abs²⁵⁴/DOC concentration, indicating the aromaticity of DOC), C:C ratio (Abs⁴⁰⁰/DOC concentration, indicating the proportion of colored humic substances in DOC), and E4:E6 ratio (Abs⁴⁶⁵/Abs⁶⁶⁵, indicating the molecular size of humic substances) in surface water and soil pore water (0-15cm depth) during the growing season (June through September). Our results showed similar changing trends in concentration and optical properties of DOC following eight years of P addition in the both surface water and soil pore water across the sampling dates. Generally, P addition decreased DOC concentration, SUVA₂₅₄, and C:C ratio, and increased E4:E6 ratio, irrespective of P addition levels. These altered optical properties of DOC indicated that P addition decreased the molecular weight and aromaticity of DOC, and thus increased the quality of DOC. These results suggest P enrichment substantially reduces the quantity of DOC in N-limited temperate freshwater wetlands, and imply that increased DOC quality following P addition can further provide a positive feedback to decreased DOC pool.

Keywords: Chemical composition; Eutrophication; Fertilization; Global change; Optical properties; Temperate wetland.