東南亞河川流域及海洋之碳循環─子計畫一：河川及湖泊二氧化碳及甲烷通量測定及底泥有機態碳及無機態碳含量之關係(II)

本年度已完成淡水河流域與高屏溪流域六次及澄清湖四次現場研析工作，在水質評 估方面，利用河川污染指數進行分類，發現淡水河流域上游水質較佳，中游最差，高屏 溪流域以上游水質較佳，中下游較差。在氣體濃度測定方面，利用上部空間法(棕色瓶) 所得之CO2 平均濃度，在淡水河流域上、中及下游依序為3,365、3,766 和1,905 ppm， 在高屏溪流域上、中及下游依序為5,526、6,779 和3,167 ppm，而在CH4 平均濃度方面， 在淡水河流域上、中及下游依序為1,315、3,546 和571 ppm，在高屏溪流域上、中及下 游則依序為5,220、5,361 和2,649 ppm。在氣體通量測定方面，淡水河流域CO2 通量介 於-87.52~104.24 mg m-2 h-1，CH4 通量則介於0.02~245.18 mg m-2 h-1，至於高屏溪流域 CO2 通量介於-51.3~134.64 mg m-2 h-1，甲烷通量則介於0.05~33.16 mg m-2 h-1。水質特性 與CO2 及CH4 通量關聯性方面，篩選七項可能影響水體產生CO2 及CH4 之因子進行分 析，包括：氧化還原電位、化學需氧量、生化需氧量、懸浮有機物含量、硝酸鹽、氨氮 及生菌數，其他項目(六項)做為現象解釋之輔助工具。除部份採樣時間為正午，受水生 植物光合作用影響，CO2 通量為負值外，其餘通量皆為正值，可提供進行統計分析研究。 結果顯示，淡水河流域水質之氧化還原電位及硝酸鹽與CO2 通量成不顯著負相關，其餘 參數則與CO2 通量成正相關，其中以BOD 與CO2 通量之關聯性較佳(R2=0.7028)，生菌 數與CO2 通量之關聯性最佳(R2=0.9001)，主要水質與CH4 通量之關聯性方面，氧化還原 電位與CH4 通量呈負相關趨勢(R2=0.5012)，ORP 需降至159 mV 以下，有較大量CH4 釋出，其中以氨氮含量之相關性較高(可能做為微生物氮源)，硝酸鹽次之(可能做為厭氣 菌之電子接受者)。淡水河流域底泥特性與CO2 及CH4 通量之關聯性方面，篩選四項可 能經由底泥固相轉移至水相，進而影響水體產生CO2 及CH4 之因子進行分析，包括：總 有機碳、總氮、硝酸鹽及氨氮，結果顯示，底泥之硝酸鹽與CO2 通量成不顯著之負相關， 總有機碳及氨氮與CO2 通量無關聯性，僅總氮與CO2 通量成正相關，在底泥特性與CH4 通量關聯性方面，硝酸鹽、氨氮與CH4 通量無關聯性，總有機碳及總氮與CH4 通量有正 相關性，由於CH4 之生成應在水體深層，因此底泥中T-N 與TOC 之影響似乎比水質成 分更重要。在高屏溪流域方面，其水質之化學需氧量、生化需氧量、氧化還原電位、生菌數與CO2 通量成正相關，其中以生菌數與CO2 通量之關聯性最佳(R2=0.9186)，水質中 之懸浮有機物含量、硝酸鹽、氨氮則與CH4 通量呈現正相關性，其中以氨氮之相關性最 高(R2=0.614)，在底泥特性與CO2 通量之關聯性方面，兩者無顯著相關性，總有機碳、 總氮與CH4 通量則有正相關性。假如不考慮各地環境之差異性，將各研究因子與氣體之 通量進行迴歸分析，僅水體中生化需氧量及生菌數與CO2 通量關聯性最高，而水體中 ORP 則與CH4 通量有較高度關聯性，底泥特性與CO2 及CH4 通量之關聯性方面，總有 機碳及總氮含量與CH4 通量成正相關，無任何底泥特性與CO2 通量有高度關聯性 (R2>0.2)。將所有因子與氣體通量同時進行複廻歸關聯性分析，發現水質中僅COD 及微 生物顯著水準(P 值)小於α(0.05)，顯示CO2 通量僅與BOD 及微生物(生菌數)有顯著的 關聯性，將無關聯性參數剔除後，最後迴歸方程式為y =0.00032x1+3.18089x2+25.37304， 水質中僅ORP 與CH4 具顯著水準，其迴歸方程式為y =-0.825216x1+169.02257。底泥與 氣體通量複廻歸關聯性方面，所有底泥特性(TOC、NO3 -、T-N、NH4 +)皆與CO2 通量無 明顯的關係，底泥中之TOC 與T-N 兩變數之顯著水準(P 值)小於α，顯示CH4 通量與這 些變數間具顯著直線關係，其相關迴歸方程式為y =5.073962x1+2.871245x2-12.3262。淡 水河中游24 小時監測方面，生菌數與二氧化碳有強烈之關聯性(R2=0.8767)，其他參數 可能因短時間監測下水質穩定，無法研判其與二氧化碳或甲烷之關聯性。大陸現地研究 方面，本次採樣共採集注入南海地區之河川水體共三十六處，其中廣西省五處，廣東省 二十八處及福建省三處。這三十六處採樣點中大氣中二氧化碳濃度最低出現於廣西省合 浦縣廉江(295.75±8.14 ppm)，濃度最高出現於廣東省新豐縣新豐江水庫(473.22±0.57 ppm)，大氣中二氧化碳平均濃度為386.85±37.13 ppm，較目前大氣中二氧化碳平均濃度 350 ppm 稍高。至於甲烷氣，在三十六處採樣點中大氣中甲烷濃度最低出現於廣西省永 安縣西江(1.28±0.02 ppm)，濃度最高則出現於廣東省寶安縣珠江(2.04±0.11 ppm)，大氣 中甲烷平均濃度為1.6±0.18 ppm。限於大陸地區實際採樣時，氣體通量不易採集之限制， 為尋求其水體表面氣體通量，利用上部空間法(Headspace method)來推測氣體通量。首先 將本島所採集之數據，建立氣體通量與上部空間法之關聯性，在二氧化碳方面，利用逐 次迴歸之方式探求兩者之最佳關聯度，結果顯示，當ORP 小於200 mV 時，可獲得良好 關聯性(R2=0.9598)，y = 114.94 x + 1262.8 之關係式。甲烷方面，將所有氣體通量與上部 空間法進行回歸分析，發現兩者間具有顯著關聯性(R2=0.8484)，y = 12.231 x + 55.397 之 關係式。在匯入南海碳通量評估方面，若以雙園大橋附近之年平均流量106 CMS 與水 中之有機物總碳量(懸浮有機物28.5 mg l-1 與化學需氧量62 mg l-1)推估，目前每年流入 南海流域之總碳量約為3×105 公噸。Over the past year, the research has accomplished six times field investigations along the Tan-Shei and Kao-Ping River and four times in Chen-chin lake area. In the water polluted aspect, the river quality is commonly impacted by the introduction of organic matter to streams and categorized by the river pollution index in this research. Overall, the principal findings in the upper stream of Tan-shei River have well-sustained water quality. The lower flows, however, show a certain water quality violation. Water quality in Kao-Ping creek area was relatively unaffected by man’s activities. But significant water quality challenge exist in lower and lowest flows. Monitoring sites were set up along the Tan-shei River and the Kao-Ping creek. The determination oof gas flux was by using the head space method. The CO2 concentration showed on upper, lower, and lowest Tan-shei river area was 3365, 3766 and 1905 ppm respectively, and 5526, 6779 and 3167 ppm in Kao-ping creek. In the CH4 aspect, the sampler indicated an average concentration of 1315, 3546 and 571 ppm on upper, lower, and lowest Tan-shei River respectively, and 5220, 5361 and 2649 ppm in Kao-ping creek. The sampler of gas emission being released or discharged into the Tan-shei River from natural or man-made sources indicated the CO2 was averagely in -87.52~104.24 mg m-2 h-1 and 0.02~245.18 mg m-2 h-1 for CH4. In Kao-ping creek area, the emission rate is approximately -51.3~134.64 mg m-2 h-1.and 0.05~33.16 mg m-2 h-1 for methane emission. To find connection between water characteristic and CO2 and CH4 emission, this research selected seven possible parameters which may affect the production of CO2 and CH4. Parameters monitored were ORP, COD, BOD, SS, Nitrate, Ammonia, and Hygiene amount. The sampling time was designed to avoid the influence of photosynthesis to water born plants in the mid-day so that samples of the actual CO2 emission concentrations are collected accurately and consistently. The presence of the ORP and nitrate in the in Tan-shei River show no decreasing relation with CO2 emission. However, the rest parameters indicated significant relationship with CO2 emission; the BOD has close relation with CO2.emission (R2=0.7028); the Hygiene keep the most direct relation with CO2 emission (R2=0.9001). In the principle of water quality measuring, the ORP and CH4 presented a decreasing relationship (R2=0.5012) with ORP decreased below 159 mV. Besides, CH4 emission was positive relationship with ammonia concentration. The phenomenon can be explained by the great amount of ammonia as a nitrogen source for microbe or nitrate as an electronic accepter for anaerobic microbe. In addition, this research selected four possible parameters to clarify the connection between river basin sediment and CO2 and CH4 emission. Parameters included TOC, total nitrogen, nitrate, and ammonia. The finding indicated the nitrate and CO2 emission has no direct relationship; TOC and ammonia presented no relation; total nitrogen and CO2 emission showed increasing relation. In the study of CH4 emission aspect, nitrate and ammonia show no relation with CH4 emission; an increasing relation existed between TOC and total nitrogen and CH4 emission. As the production of CH4 occurred often in the deep water body, the total nitrogen and TOC in the basin mud possessed more significant role than water quality. In Kao-ping creek area, the COD, BOD, ORP, microbe in the water body presented an increasing relation with CO2 emission. The hygiene presented a significant relation with CO2 emission (R2=0.9186). The suspended organic matter, nitrate, and ammonia nitrogen demonstrated an increasing relation with CH4 emission. Among than, the ammonia nitrogen showed a significant relation (R2=0.614). In the research of the connection between basin mud and CO2.emission, no apparent relation existed, but TOC and total nitrogen indicated an increasing relation with CH4 emission. Without considering the difference of sampling surrounding environment, the research applied regression techniques to analyze the relation between parameters collected and gas emission. The result showed that the BOD and hygiene in the water body exists a strong relation with CO2.emission. The ORP in the water body had a high connection to the CH4 emission. In the characteristic of river basin mud with CO2 and CH4 emission, the concentration of TOC and total nitrogen indicated a high relation with CH4 emission, and seldom evident had direct relation with CO2 emission (R2>0.2). In applying multiple-regression techniques on all parameter and gas emission, the research uncover that the COD and microbe with CO2 flux shows high relationship (P < α), which means the CO2 emission can only connect to the change of BOD and microbe concentration. Taken off the unrelated parameter, the final regression formula is y =0.00032x1+3.18089x2+25.37304. The ORP in the water body presented the unique role in react with CH4 emission. The regression formula is y =-0.825216x1+169.02257. In multiple-regression analysis of river basin mud with gas emission, the characteristic of river basin mud, TOC, NO3 -、T-N、NH4 +, had no parent relation with CO2 emission, but two variant, TOC and T-N, in the mud presented an apparent P value less than α, which showed a linear relation was existed between CH4 emission and the variant. The final regression formula is y =5.073962x1+2.871245x2-12.3262. Conducting 24 hrs monitoring in the midstream of Tan-shei River, the finding showed only the strong relation between hygiene and CO2 emission (R2=0.8767). Constrained by the limited sampling time, the research has little evident to clarify the relation between the CH4 and CO2 emission. The research conducted in China has totally sampled 36 locations in which the river in South Sea infilling. In total, five sampling point located in Kung-His Province, 28 point in Kung-Dong Province, and 3 points in Fu-Chien Province. The lowest concentration of CO2 in the atmosphere was showed at Lian-chung city, Ho-Pu county, Kung-tung Province (295.75± 8.14）, and the highest concentration of CO2was showed at New Fun-chung Dam, Hsin-Fun county, Kung-tung Province (473.22±0.57 ppm). The average concentration of CO2 in the atmosphere, 386.85±37.13 ppm, was higher than the current concentration of 350 ppm. For methane gas, the lowest concentration in 36 sampling points was showed at His-chung city, Yun-an county, Kung-His Province (1.28±0.02 ppm), and the highest concentration was occurred at Chu-chung city, Po-an county, Kung-His Province (2.04±0.11 ppm).The average concentration of methane in the atmosphere is 1.6±0.18 ppm. Constrained by geographic difficulty, the research adopted headspace method to obtain the data of gas emission. The data collected from the Taiwan was first used in establishing the connection between gas emission and headspace. Following the procedure, the regression method was utilized to search the proper relation. The finding showed that the CO2 existed a proper relation with ORP under the concentration less than 200 mV (R2=0.9598), and the final formula is y = 114.94x + 1262.8. In methane aspect, regression method was used on all gas emission and headspace, and the result showed that an apparent relation existed between them (R2=0.8484). The final formula is y = 12.231x + 55.397. In the assessment of carbon emission to the South Sea, the annual flow amount of 106 CMS and carbon concentration (28.5 mg l-1 suspended organic and 62 mg l-1 COD) in the water body were used to estimate the total carbon. The result showed a 3×105 ton in total