Qin Xiaobo

脱甲河农业流域土壤沉积物氮素时空分布与N 2 O释放

为研究脱甲河农业小流域氮素输出特性，运用流动注射仪法和顶空平衡-气相色谱法于2015年4月—2016年1月对流域内4级河段（S1、S2、S3和S4）稻田-岸坡-河底沉积物土壤铵态氮（NH4+-N）、硝态氮（NO3--N）及水体溶存氧化亚氮（N2O）浓度进行了连续10个月的监测，并利用双层扩散模型法对水系N2O排放通量进行了估算.结果表明：脱甲河流域稻田-岸坡-河底沉积物NH4+-N含量逐渐升高，NO3--N含量逐渐降低，其中，岸坡及河底沉积物土壤中的氮主要以NH4+-N形式为主，均值分别为（7.38±0.62）mg·kg-1和（16.49±1.70）mg·kg-1；稻田土壤和脱甲河水体中的氮主要以NO3--N为主，均值分别为（7.40±0.81）mg·kg-1和（1.55±0.03）mg·L-1.水体溶存N2O浓度范围在0.005~7.37 μmol·L-1之间，均值为（0.54±0.05）μmol·L-1；扩散通量在-1.11~1811.29 μg·m-2·h-1之间，均值为（130.10±12.04）μg·m-2·h-1，每年向大气输出的N2O量为11.40 kg·hm-2.其中，在早稻生长初期和早晚稻收割、栽种交替时段N2O输出量达到高峰.空间上，N2O扩散通量表现为S1 < S4 < S3 < S2，S1级河段显著低于其他3级河段（p < 0.01）.相关分析表明，脱甲河表层水体N2O扩散通量与NH4+-N（r=0.87，p < 0.01）、NO3--N（r=0.80，p < 0.01）和水温（r=0.57，p < 0.01）呈显著正相关，流域内稻田-岸坡-河底沉积物及水体NH4+-N和NO3--N浓度间相关性不显著.脱甲河农业小流域氮素流失主要包括稻田-岸坡-河底沉积物中铵态氮、硝态氮及水体中N2O，在水稻栽种期间出现高峰，存在较大氮素流失风险，因此，开展农业小流域氮素流失研究对区域氮素周转及农业生产活动具有重要的指导意义.

A Study of Paddy CO2 Emissions under Long-Term Fertilizations and Associated Impact Factors

A field experiment was made using static chamber-GC theory to observe CO₂ emissions from rice paddy that have been fertilized for 25 consecutive years. Impact factors derived from the experiment were also studied. Seasonal variations of CO₂ flux presented a similar pattern, though they were different in treatment. CO₂ flux peaks appeared in the flooding season, with the bottom in the drainage. Seasonal trends of CO₂ flux went along with the air temperature near the ground. Chemical fertilizer applications produced more CO₂ flux, compared with other treatments, though there was no significant correlation between other treatments and the treatment with only chemical fertilizer. NPKS had the largest CO₂ flux, or 502.58 mgldrm^-2h^-1, and CK the lowest flux, or 249.16 mgldrm^-2h^-1 . There was a significant negative correlation between CO₂ flux and water depth (p<0.01). Water is a most important factor that controls paddy CO₂ flux. Temperature is another most important factor that controls CO₂ flux from rice-involved plots, in a range of 13.33degC~38.59degC. There is a significant exponential relationship between CO₂ flux and temperature, or F=20.1365e ^0.088838T (p<0.01). Temperature coefficient (Q10) was 2.43. Both soil pH and Eh values were correlated with CO₂ flux (p<0.01), though further study is needed to clarify the mechanism.