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Hydrological, geochemical and land use drivers of greenhouse gas dynamics in eleven sub-tropical streams
Aquatic Sciences ( IF 2.4 ) Pub Date : 2021-03-14 , DOI: 10.1007/s00027-021-00791-x
Luke F. Andrews , Praktan D. Wadnerkar , Shane A. White , Xiaogang Chen , Rogger E. Correa , Luke C. Jeffrey , Isaac R. Santos

Greenhouse gas (GHG) emissions from freshwater streams are poorly quantified in sub-tropical climates, especially in the southern hemisphere where land use is rapidly changing. Here, we examined the distribution, potential drivers, and emissions of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) from eleven Australian freshwater streams with varying catchment land uses yet similar hydrology, geomorphology, and climate. These sub-tropical streams were a source of CO2 (74 ± 39 mmol m−2 day−1), CH4 (0.04 ± 0.06 mmol m−2 day−1), and N2O (4.01 ± 5.98 µmol m−2 day−1) to the atmosphere. CO2 accounted for ~ 97% of all CO2-equivalent emissions with CH4 (~ 1.5%) and N2O (~ 1.5%) playing a minor role. Episodic rainfall events drove changes in stream GHG due to the release of soil NOx (nitrate + nitrite) and dissolved organic carbon (DOC). Groundwater discharge as traced by radon (222Rn, a natural groundwater tracer) was not an apparent source of CO2 and CH4, but was a source of N2O in both agricultural and forest catchments. Land use played a subtle role on greenhouse gas dynamics. CO2 and CH4 increased with catchment forest cover during the wet period, while N2O and CH4 increased with agricultural catchment area during the dry period. Overall, this study showed how DOC and NOx, land use, and rainfall events interact to drive spatial and temporal dynamics of GHG emissions in sub-tropical streams using multiple linear regression modelling. Increasing intensive agricultural land use will likely decrease regional CO2 and CH4 emissions, but increase N2O.



中文翻译:

11种亚热带河流温室气体动力学的水文,地球化学和土地利用驱动因素

在亚热带气候中,尤其是在土地利用迅速变化的南半球,淡水流产生的温室气体(GHG)排放很难量化。在这里,我们研究了来自11个澳大利亚淡水溪流,流域土地用途不同但水文,地貌和水生环境相似的二氧化碳的分布,潜在驱动因素和排放的二氧化碳(CO 2),一氧化二氮(N 2 O)和甲烷(CH 4)。气候。这些亚热带流是CO的源2(74±39毫摩尔米-2-1),CH 4(0.04±0.06毫摩尔米-2-1)和N 2 O(4.01±5.98微摩尔米- 2个-1天)到大气中。CO 2占所有CO 2当量排放量的〜97 %,其中CH 4(〜1.5 %)和N 2 O(〜1.5%)发挥的作用很小。降雨事件开车在流GHG的变化,由于土壤的释放NO X(硝酸盐+亚硝酸盐)和溶解的有机碳(DOC)。ra(222 Rn,天然地下水示踪剂)所追踪的地下水排放不是CO 2和CH 4的明显来源,而是农业和森林集水区的N 2 O来源。土地使用对温室气体动力学起着微妙的作用。CO 2和CH 4干旱时期,随着集水区森林覆盖率的增加,N 2 O和CH 4随农业集水区的增加而增加。总体而言,这项研究表明,使用多元线性回归模型,DOC和NO x,土地利用和降雨事件如何相互作用以驱动亚热带河流中温室气体排放的时空动态。提高集约农业土地利用可能会因此减少区域CO 2和CH 4的排放量,但增加Ñ 2 O.

更新日期:2021-03-15
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