中国农业科学 ›› 2016, Vol. 49 ›› Issue (20): 3968-3980.doi: 10.3864/j.issn.0578-1752.2016.20.011

• 土壤肥料·节水灌溉·农业生态环境 • 上一篇    下一篇

亚热带农业小流域水系溶存甲烷浓度和扩散通量研究

张羽1, 2,李 悦2,秦晓波1,孔范龙2,郗 敏2,李玉娥1

 
  

  1. 1中国农业科学院农业环境与可持续发展研究所/农业部农业环境重点实验室,北京 100081
    2青岛大学环境科学与工程学院,山东青岛266000
  • 收稿日期:2016-02-02 出版日期:2016-10-16 发布日期:2016-10-16
  • 通讯作者: 李悦,E-mail:qdenv@126.com。秦晓波,E-mail:qinxiaobo@caas.cn
  • 作者简介:张羽,E-mail:zhangyusdlq@163.com
  • 基金资助:
    国家自然基金面上项目(41475129)、国家“973”计划专项(2012CB417106)

Dissolved Methane Concentration and Diffusion Flux in Agricultural Watershed of Subtropics

ZHANG Yu1, 2, LI Yue2, Qin Xiao-bo1, Kong Fan-long2, Xi Min2, Li Yu’e1   

  1. 1Institute of environment and sustainable development in agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory of Agricultural Environment, Ministry of Agriculture, Beijing 100081
    2Institude of Environmental Science and Engineering,  Qingdao University, Qingdao 266000, Shandong
  • Received:2016-02-02 Online:2016-10-16 Published:2016-10-16

摘要: 【目的】研究亚热带丘陵地区农业小流域水系溶存甲烷(CH4)浓度分布特征及其扩散传输特性。【方法】在一年周期内(20144132015412),利用扩散模型法对湘江下游脱甲小流域4级河流溶存CH4浓度及扩散通量的时空变异及其影响因素进行研究。【结果】脱甲小流域水系溶存CH4浓度年均值为(0.61±0.43)μmol·L-1,变化范围为0.03—2.23 μmol·L-1;扩散通量在一年内的变化为1.71—290.08(63.36±50.76)μgC·m-2·h-1,表现为大气CH4的净源。河流溶存CH4浓度和通量的时空分布均呈现出显著的差异:时空变化规律具有一致性,其中季节变化特征均为春高((0.74±0.41)μmol·L-1,(93.58±65.24)μgC·m-2·h-1),冬低((0.53±0.38)μmol·L-1,(50.79±33.03)μgC·m-2·h-1);空间分布呈现自上游到下游波动增加的趋势。影响脱甲小流域河流溶存CH4浓度和扩散通量的环境因子中,溶解氧(DO:3.49—12.79(7.90±1.78)mg·L-1)与河流溶存CH4浓度(r=-0.39,P<0.001)和扩散通量(r=-0.36,P<0.001)均呈显著负相关,溶解性有机碳(DOC:0.92—7.38(2.99±1.25)mg·L-1)与河流溶存CH4浓度(r=0.50,P<0.001)和扩散通量(r=0.44,P<0.001)均呈显著正相关,两者是影响河流溶存CH4浓度和扩散通量的主导因子;另外,水体铵态氮(NH4+-N:0.02—4.37(1.26±1.03)mg·L-1)、硝态氮(NO3--N:0.24—2.66(1.43±0.55)mg·L-1)、盐度(以电导率EC表示:50.36—248.43(138.37±47.54)μS·cm-1)与河流溶存CH4浓度和扩散通量均呈显著正相关;河流水体pH(5.89—8.54(6.82±0.31))与CH4浓度呈正相关(r=0.20,P<0.05),与通量之间无显著关联。【结论】脱甲小流域内,农业面源污染、畜牧养殖以及居民生活废水和污水的排入造成的河流水体中DOC、氮含量的增加以及DO的降低,均能加剧河流中溶存CH4气体的产生和排放,使其成为大气CH4的一个重要潜在排放源。

关键词: 亚热带小流域, 水系, 甲烷, 浓度, 扩散通量, 影响因素

Abstract:

【Objective】The objective of this study is to investigate the regulation of dissolved CH4 and flux diffused from river water and its influencing factors. 【Method】A one year period of (from April 2014 to April 2015) monitoring was conducted in Tuojia watershed of Xiangjiang river, which is located in the red soil hilly area of subtropical China. The double-layer-diffusion model was used to measure the diffusion of CH4 flux from river water and the influencing factors of water were monitored by a portable multi-parameter meter. Four reaches river of Tuojia watershed with 3 streams (up stream, middle stream and down stream) each were employed in this study. 【Result】The results indicated that the annual dissolved CH4 concentration and diffusion flux of CH4 from Tuojia river varied widely from 0.03 to 2.23(0.61±0.43) μmol·L-1 and from 1.71 to 290.08(63.36±50.76) μgC·m-2·h-1, respectively. Tuojia river expressed as the net source of atmospheric CH4. There was a significant spatial and temporal difference both in the CH4 concentration and flux between the 4 reaches. Generally speaking, the CH4 flux from down stream were greater than the up stream, and the same as the CH4 concentration (S4>S3>S2>S1). And the temporal variation of CH4 concentration and flux between the 4 reaches was also significant. Spring period (from April 2014 to Jun 2014) showed the highest CH4 concentration (0.74±0.41μmol·L-1) and the highest flux (93.58±65.24μgC·m-2·h-1), and winter period (from Dec 2014 to April 2015) showed the smallest CH4 concentration(0.53±0.38 μmol·L-1) and the smallest flux (50.79±33.03 μgC·m-2·h-1). By correlation analysis, it was found that, on the one hand, the water dissolved oxygen(DO: 3.49-12.79 (7.90±1.78) mg·L-1) appeared a significant negative correlation with CH4 concentration(r=-0.39, P<0.001) and CH4 flux(r=-0.36, P<0.001), while the dissolved organic carbon (DOC: 0.92-7.38 (2.99±1.25) mg·L-1) showed a positive correlation with CH4 concentration(r=0.50, P<0.001) and CH4 flux(r=0.44, P<0.001), all of them were the dominant factors that influence the CH4 concentration and CH4 flux of Tuojia River, on the other hand, dissolved inorganic N (NH4+-N: 0.02-4.37 (1.26±1.03) mg·L-1, NO3--N: 0.24-2.66 (1.43±0.55) mg·L-1) concentration, salinity(represented by electrical conductivity EC: 50.36-248.43 (138.37±47.54) μS·cm-1) appeared a positive correlation with CH4 concentration and CH4 flux. Additionally, water pH value (5.89-8.54(6.82±0.31)) showed a positive relationship with stream CH4 concentration (r=0.20, P<0.05), but not a significant correlation with CH4 flux. The dissolved CH4 in river water was produced from river sediment by methanogenesis, and then diffused from water to atmosphere.【Conclusion】The results of this study indicate that waste and sewage produced by agricultural non-point source pollution, livestock breeding and human activities are the main reasons that leading to the increase of river pollution loading and the decrease of water DO, which give raises to more stream CH4 transportation, made river as an important potential CH4 source.

Key words: subtropical watershed, water system, methane, concentration, diffusion flux, impact factors