脱甲河水系CH_4关键产生途径及其稳定碳同位素特征

为明确脱甲河溶存CH_4关键产生途径,明晰水系碳同位素组成及其分布特征,为小流域CH_4排放估算和减排提供数据支撑.利用双层扩散模型法估算了CH_4浓度和传输通量,研究了周年内脱甲河4级河段(S_1~S_4)水体CH_4通量的时空分布及其主控环境因子;运用稳定同位素方法探究了溶存CH_4关键产生途径,分析了溶解CH_4、悬浮颗粒物和沉积物有机质δ¹³C分布特征.结果表明:水体pH均值为(7.27±0.03),各河段四季差异均显著;溶解氧(DO)在0.43~13.99 mg·L^-1内变化,S_1河段DO浓度最高且夏、秋季差异显著,其他河段均为冬与春、夏、秋季差异显著;可溶性有机碳(DOC)变化范围是0.34~8.32 mg·L^-1,由S_1至S_4河段总体呈递增趋势;水体电导率(EC)和氧化还原电位(ORP)变化范围分别是17~436μS·cm^-1和-52.30~674.10 mV,各河段差异明显;铵态氮(NH_4^+-N)、硝态氮(NO_3^--N)浓度分别在0.30~1.35(平均0.90±0.10)mg·L^-1和0.82~2.45(平均1.62±0.16)mg·L^-1内变化.溶存CH_4浓度和传输通量变化范围分别是0~5.28(平均0.46±0.06)μmol·L^-1和-0.34~619.72(平均53.88±7.15)μg C·m^-2·h^-1;均存在时空变化且变异规律相似,为春季>冬季>夏季>秋季,S_2>S_3>S_4>S_1.通量与水体铵态氮和DOC浓度均呈显著正相关.各级河段均以乙酸发酵产甲烷途径为主导,但不同河段差异明显,乙酸发酵途径产CH_4贡献率以S_1河段最高(87%),其次为S_4(81%),S_2、S_3分别达到78%和76%.溶存CH_4、悬浮颗粒物和沉积物有机质的δ¹³C均值分别为-41.64‰±1.91‰、-14.07‰±1.06‰和-26.20‰±1.02‰,溶存甲烷δ¹³C与沉积物有机质的δ¹³C呈显著正相关,与其传输通量呈极显著负相关.

Key pathway of methane production and characteristics of stable carbon isotope of the Tuojia River waterbody

ZHAO Qiang1＇2, LYU Cheng-wen2, QIN Xiao-boi , WU Hong-bao, WAN Yun-fan, LIAO Yu-lin3, LU Yan-hong3, WANG Bin1, LI Yong4(1.Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory of Agricultural Environment, Ministry of Agriculture, Beijing 100081, China ; 2 College of Territorial Resources and Tourism, Anhui Normal University, Wuhu 241002, Anhui , China; 3 Hunan Institute of Soil and Fertilizer, Changsha 410125, China; 4Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China)