Seasonal variability of sediment controls of nitrogen cycling in an agricultural stream
Seasonal variability of sediment controls of nitrogen cycling in an agricultural stream
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DOI：
10.1007/s10533-020-00644-z
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发表时间：
2020-02-13
期刊：
影响因子：
4
通讯作者：
Krause, Stefan
中科院分区：
文献类型：
--
作者：
Comer-Warner, Sophie A.;Gooddy, Daren C.;Krause, Stefan
农业河流接受大量营养物质的输入，如硝酸盐（NO3-）和铵（NH4+），影响水质和河流健康。河床沉积物是生物地球化学反应的热点，其特征是养分衰减和反硝化速率高。先前在河流沉积物中观察到的高浓度氧化亚氮（N2O）表明不完全反硝化作用，沉积物是全球N2O的潜在重要来源。我们研究了沉积物类型和季节变化对英国一条农业河流河床反硝化和N2O生成的影响。反硝化作用受沉积物类型的强烈控制，砂质沉积物的潜在反硝化速率比砾石沉积物高近10倍(砂质沉积物为0.026 +/- 0.004 n20 - n mu g g(-1) h(-1))，砾石沉积物为0.003 +/- 0.003 n20 - n mu g g（-1) h(-1)）。现场测量支持这一发现，在砾石为主的沉积物孔隙水中观察到较高浓度的NO3-、亚硝酸盐（NO2-）和N2O。反硝化作用在季节之间变化很大，从冬季到秋季反硝化作用增加。我们的研究结果表明，在以砂为主的沉积物中，NO3-还原量最大，而在以砾石为主的沉积物中，N2O浓度最高。这表明，细粒河床在去除农业集水区过量氮而不产生过量N2O方面可能发挥重要作用。
Agricultural streams receive large inputs of nutrients, such as nitrate (NO3-) and ammonium (NH4+), which impact water quality and stream health. Streambed sediments are hotspots of biogeochemical reactivity, characterised by high rates of nutrient attenuation and denitrification. High concentrations of nitrous oxide (N2O) previously observed in stream sediments point to incomplete denitrification, with sediments acting as a potentially significant source of global N2O. We investigated the effect of sediment type and seasonal variation on denitrification and N2O production in the streambed of an agricultural UK stream. Denitrification was strongly controlled by sediment type, with sand-dominated sediments exhibiting potential rates of denitrification almost 10 times higher than those observed in gravel-dominated sediments (0.026 +/- 0.004 N2O-N mu g g(-1) h(-1) for sand-dominated and 0.003 +/- 0.003 N2O-N mu g g(-1) h(-1) for gravel-dominated). In-situ measurements supported this finding, with higher concentrations of NO3-, nitrite (NO2-) and N2O observed in the porewaters of gravel-dominated sediments. Denitrification varied substantially between seasons, with denitrification increasing from winter to autumn. Our results indicate highest NO3- reduction occurred in sand-dominated sediments whilst highest N2O concentrations occurred in gravel-dominated sediments. This suggests that finer-grained streambeds could play an important role in removing excess nitrogen from agricultural catchments without producing excess N2O.