ORIGINAL ARTICLE Effects of sediment texture on in-stream nitrogen uptake Dingjiang Chen • Hailong Wang • Gerty Gielen • Yena Shen • Songchao Chen • Jiawei Chen • Jun Lu Received: 8 May 2013 / Accepted: 4 November 2013 / Published online: 6 December 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract A comparative experiment was conducted in two cross sections with sandy and sandy loam sediment textures along an agricultural drainage stream in eastern China to address the effects of sediment texture on in- stream nitrogen uptake efficiency. Using dimerous cham- bers for in situ incubations, NO 3 -N and NH 4 -N uptake metrics (i.e., areal uptake rate and uptake velocity) and associated hydrochemical variables in the enclosed sedi- ment–water column system were measured for 8 days and two nights across April–July in 2011 and March–June in 2012. For the investigated sites, in-stream uptake accoun- ted for 2–45 and 9–36 % of the initial NH 4 -N and NO 3 -N within the enclosed water column, respectively. Although similar daytime, diel and day-to-day (daytime) variation patterns of NO 3 -N or NH 4 -N uptake metrics were observed for the two sites, the sandy loam sediments had average net NO 3 -N and NH 4 -N uptake efficiency *50 % higher and *40 % lower than for the sandy sediments, respectively. As NO 3 -N was the dominant nitrogen form in the studied water columns (typical of agricultural drainage rivers), the sandy loam sediment site had an average of about 47 % higher net uptake efficiency for dissolved inorganic nitro- gen (i.e., NO 3 -N ? NH 4 -N). This study demonstrates that sediment texture has a considerable effect on spatial vari- ation of nitrogen uptake along the river system. Changing sediment texture due to anthropogenic modifications on catchment land use and stream channels has the potential to change stream nitrogen cycling as well as altering nitrogen inputs and forms to downstream aquatic ecosystems. Keywords Nitrogen  Uptake  Denitrification  Nitrification  Sediment texture Introduction Excessive riverine nitrogen loading associated with agri- culture and urbanization is of increasing concern world- wide, as it induces eutrophication and hypoxia in many downstream freshwater and marine ecosystems (Mulhol- land et al. 2008; Peterson and Benning 2013; Schwientek et al. 2013). In-stream nitrogen uptake by various pro- cesses, such as microbial denitrification, biological assim- ilation, and sediment sorption (Birgand et al. 2007; Chen et al. 2010), is an important process regulating watershed nitrogen loading during downstream transport, as it can account for 1–80 % of the annual nitrogen input load to streams (Seitzinger et al. 2006; Chen et al. 2010). In-stream D. Chen (&)  H. Wang  Y. Shen  S. Chen  J. Chen  J. Lu (&) College of Environmental Science and Natural Resources, Zhejiang University, 866# YuHangTang Road, Hangzhou 310058, Zhejiang, China e-mail: chendj@zju.edu.cn J. Lu e-mail: twsp455@zju.edu.cn D. Chen China Ministry of Education Key Lab of Environment Remediation and Ecological Health, Zhejiang University, Hangzhou 310058, China H. Wang School of Environmental and Resource Sciences, Zhejiang A & F University, Lin’an, Hangzhou 311300, China G. Gielen Scion, Private Bag 3020, Rotorua 3046, New Zealand J. Lu Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058, China 123 Environ Earth Sci (2014) 72:21–33 DOI 10.1007/s12665-013-2983-x