摘要
选择东江流域为研究区,监测流域溶解氧、氮浓度和氮氧多同位素时空变化,定量探究氮周转过程对河流溶解氧消耗的贡献.结果发现,河流溶解氧浓度在2.96~11.47mg/L之间变动,春夏季下游感潮河网区成为氧消耗利用和氧亏缺的热点区,其中表观耗氧量最高达4.8mg/L,并与水温和Cl^(-)浓度呈现高度相关性.然而,冬春季下游感潮河网区是不同形态氮浓度的累积区以及氮同位素发生硝化作用分馏的主要时区.基于端元混合模型和同位素瑞利分馏模型模拟可知,夏季氮主要体现为保守混合,而冬、春季氮则呈现非保守状态,并在下游河网区易发生硝化作用,其作用程度分别为14.4%和32.3%,这也分别对应着冬、春季最大约7.5%和5.9%的溶解氧消耗利用来自氨氧化耗氧.氮的环境行为对河流溶解氧的影响相对局限,特别是夏季氧亏缺问题更多地受其他因素的主导.这为当前环境管理多通过氨氮标准评价和研判溶解氧能否达标的局限认识带来新的见解,也为探索研究建立分区域、分流域的溶解氧评价和考核体系提供技术支撑.
The Dongjiang River basin was selected as the study area to monitor the spatio-temporal variations in dissolved oxygen(DO),nitrogen concentration and multi-isotope in the basin,so as to provide a better understanding for the quantitative contribution of nitrogen turnover processes to DO depletion.The DO concentrations ranged from 2.96mg/L to 11.47mg/L in the Dongjiang River.In the spring and summer,the downstream of the river became the low DO hot spot,where the highest value in the apparent oxygen utilization(AOU)was up to 4.8mg/L,and a high correlation between water temperature and Cl-concentration and AOU was observed.However,the accumulation of different nitrogen species and δ^(15)N fractionation of nitrification mainly occurred in the downstream river network area in the winter and spring.Based on the end-members mixing model and isotope Rayleigh fractionation model,it was found that nitrogen mainly reflected the conservative mixing driven by hydrological process in the summer whereas nitrogen prone to occur nitrification in the downstream in the winter and spring.The degree of nitrification reached 14.4% and 32.3% in the winter and spring,respectively,which also corresponded to about 7.5% and 5.9% of AOU in maximum,respectively.Therefore,there were certain limitations in the contribution of nitrogen behavior to the low DO in tidal river.Especially,the oxygen deficit in the summer might be dominated by other factors.Our results will provide a new insight into the limitations of current environmental management pattern in judging whether DO will satisfy the water quality standard through the concentration of ammonia nitrogen,and will also provide a support for exploring and establishing the DO assessment systems focused on distinguishing different regions and watersheds.
作者
温婧
黄邦杰
黄志伟
房怀阳
王龙乐
张英民
曾凡棠
杜宏伟
WEN jing;HUANG Bang-jie;HUANG Zhi-wei;FANG Huai-yang;WANG Long-le;ZHANG Ying-min;ZENG Fan-tang;DU Hong-wei(Guangdong Key Laboratory of Water and Air Pollution Control,National Key Laboratory of Water Environment Simulation and Pollution Control,South China Institute of Environmental Science,Ministry of Ecology and Environment,Guangzhou 510535,China)
出处
《中国环境科学》
EI
CAS
CSCD
北大核心
2023年第8期4003-4012,共10页
China Environmental Science
基金
广东省重点领域研发计划项目(2020B1111350001)
中央级公益性科研院所基本科研业务专项(PM-zx703-202104-082)
广州市基础研究计划基础与应用基础研究项目(2023A04J0950)。
关键词
感潮河流
溶解氧亏损
氮周转耗氧贡献
氮氧同位素
the tidal river
dissolved oxygen deficit
contribution of nitrogen turnover to oxygen deficit
nitrogen and oxygen multi-isotope
