U.S. Geological Survey, New England Water Science Center, 196 Whitten Rd., Augusta, ME 04330, USA.
U.S. Geological Survey, Maryland-Delaware-D.C. Water Science Center, 5522 Research Park Drive, Catonsville, MD 21228, USA.
Sci Total Environ. 2021 Jul 15;778:146149. doi: 10.1016/j.scitotenv.2021.146149. Epub 2021 Mar 2.
The mobilization and transport of organic carbon (OC) in rivers and delivery to the near-coastal ocean are important processes in the carbon cycle that are affected by both climate and anthropogenic activities. Riverine OC transport can affect carbon sequestration, contaminant transport, ocean acidification, the formation of toxic disinfection by-products, ocean temperature and phytoplankton productivity. There have been many studies reporting temporal trends in OC concentrations in comparatively small streams with minimal anthropogenic influences but there have been fewer studies on larger rivers and fewer still that have investigated changes in OC concentration-discharge (C-Q) relations. This study examined changes in C-Q relations for total organic carbon (TOC) from 1973 to 2019 in 8 rivers in New England, USA. TOC concentrations declined in all rivers, and in most rivers, and in most seasons, the slope of the C-Q relation increased between 1973 to 1995 and 1996 to 2019. The increase in C-Q slope between periods may be related to changes in the magnitude of TOC sources. The most likely sources to have changed are wastewater inputs, urban runoff, production through photosynthesis in aquatic systems, and runoff from agricultural and forestry practices. Changes in wetland abundance and changes in sulfate concentrations can be ruled out as drivers of the observed changes in C-Q.
河流中有机碳（OC）的迁移和输送以及向近岸海洋的输送是碳循环中的重要过程，受到气候和人为活动的影响。河流 OC 输送会影响碳封存、污染物输送、海洋酸化、有毒消毒副产物的形成、海洋温度和浮游植物生产力。已有许多研究报告了受人为影响最小的相对较小溪流中 OC 浓度的时间趋势，但对较大河流的研究较少，对 OC 浓度-流量（C-Q）关系变化的研究则更少。本研究调查了 1973 年至 2019 年期间美国新英格兰 8 条河流中总有机碳（TOC）的 C-Q 关系变化。所有河流的 TOC 浓度都下降了，在大多数河流和大多数季节，1973 年至 1995 年和 1996 年至 2019 年期间，C-Q 关系的斜率增加。两个时期之间 C-Q 斜率的增加可能与 TOC 来源的变化有关。最有可能发生变化的来源是废水输入、城市径流、水生系统光合作用产生的产物以及农业和林业实践产生的径流。湿地丰度的变化和硫酸盐浓度的变化可以排除为观察到的 C-Q 变化的驱动因素。
