滁州花山水文實驗流域氮流失特征分析

王建群,郭 昆,劉松平,王 洋

(河海大學水文水資源學院,江蘇 南京 210098)

滁州花山水文實驗流域氮流失特征分析

王建群,郭 昆,劉松平,王 洋

(河海大學水文水資源學院,江蘇 南京 210098)

水文實驗流域;氮流失;非點源污染;土地利用

1 材料與方法

1.1 研究區(qū)概況

研究區(qū)域花山水文實驗流域位于安徽省東部城市滁州市域內(nèi),范圍在東經(jīng)118°8′8″～118°16′50″、北緯32°13′16″～32°18′52″之間,距滁州市主城區(qū)10 km處,流域出口胡莊斷面集水面積80.13 km2。流域內(nèi)河系呈標準的扇形,胡莊測流斷面以上有3條支流和1條小溝匯入,分別為東源、中源、西源和竹園溝。流域水系見圖1。研究區(qū)域氣候屬于溫帶半濕潤季風氣候,冬季干旱少雨,夏季高溫多雨,四季分明,氣候溫和,平均氣溫14～15℃,多年平均E601水面蒸發(fā)1 100～1 300 mm,多年平均降水量1 048.5 mm。

花山水文實驗流域為丘陵地區(qū),地形復雜,主要以鄉(xiāng)村景觀為主,農(nóng)田、塘壩、林地等交錯分布。本研究于2013年1月開展實地調查和遙感資料調查,結果表明,研究區(qū)域土地利用/覆被面積比例分別為：林地68.33%,水田14.64%,旱地8.02%,裸地4.85%,水體2.84%,建筑用地1.32%,涉及屬滁州市南譙區(qū)施集鎮(zhèn)的豐山、花山、龍蟠、榮譽、楊家飯店、河東等6個行政村3 533戶12 196人,其中常住人口9 944人;流域內(nèi)有牛27頭、豬1 150頭、羊3 600只、土雞76 420只、肉雞197 800只、鴨118 500只;農(nóng)作物主要有水稻、小麥、油菜、棉花、玉米、花生等;經(jīng)濟以種養(yǎng)殖業(yè)為主,畜禽養(yǎng)殖業(yè)是農(nóng)民收入的重要來源。研究區(qū)域無工業(yè),氮的主要來源是農(nóng)業(yè)化肥、人畜糞便、大氣氮沉降、生物固氮、種子等。

圖1 花山水文實驗流域水系與子流域及采樣點

1.2 地理信息提取

研究中使用到的空間數(shù)據(jù)主要包括數(shù)字高程模型DEM、水系圖、子流域劃分、土地利用圖等,由項目組直接從資源三號衛(wèi)星影像中提取?；谫Y源三號衛(wèi)星遙感影像進行土地利用信息的提取,將區(qū)域土地利用類型劃分為常綠林、落葉林、水田、旱地、水體、裸地及建筑用地,并運用混淆矩陣對土地利用圖進行了精度評價,總體精度為92.04%,Kappa系數(shù)為0.903 0。水系與子流域劃分、土地利用情況分別見圖1、圖2。

圖2 花山水文實驗流域土地利用情況

1.3 監(jiān)測斷面布置

根據(jù)花山水文實驗流域的下墊面特征和徑流監(jiān)測站點的位置及研究的目的,在全流域干支流上共布設了10個氮素監(jiān)測斷面,其中西源子流域為重點監(jiān)測子流域,自上而下分別布置了軍事牌、汪郢左支、汪郢水庫下、三板橋、三岔河等5個監(jiān)測斷面,汪郢左支斷面在西源支流上與軍事牌斷面并聯(lián);竹園溝子流域布置了1個監(jiān)測斷面竹園溝;中源子流域布置了2個監(jiān)測斷面——新壩、蔡集橋,其中新壩監(jiān)測斷面布置在中源干流的支流上;東源子流域布置了1個監(jiān)測斷面張郢;花山流域出口斷面為胡莊斷面。斷面位置參見圖1。

利用ArcGIS對土地利用圖進行統(tǒng)計分析得各監(jiān)測斷面集水區(qū)土地利用信息,見表1。

表1 各監(jiān)測斷面集水區(qū)土地利用類型面積比例統(tǒng)計結果

1.4 樣品采集與分析

表2 監(jiān)測項目監(jiān)測期年平均值統(tǒng)計結果

1.5 研究區(qū)域不同月份降雨量統(tǒng)計

研究區(qū)域雨量觀測資料來源于水利行業(yè)公益性科研專項(201201026)參加單位安徽省滁州水文局。對研究區(qū)域各站點不同月份降雨量進行統(tǒng)計,并進行面積加權平均,計算結果見表3。

表3 研究區(qū)域不同月份降雨量統(tǒng)計結果

2 結果與分析

2.1 實驗流域年尺度氮輸出特征

由監(jiān)測斷面監(jiān)測項目年平均值統(tǒng)計表(表2)可以看出:

b. 汪郢左支斷面和軍事牌斷面集水區(qū)域林地比重高達99.92%以上,人類活動較少,CODMn質量濃度分別為1.72 mg/L、2.36 mg/L,分別達到Ⅰ類水和Ⅱ類水標準,但TN輸出量較高,甚至高于集水區(qū)域農(nóng)田比重較大的竹園溝、新壩斷面。這一現(xiàn)象與人們通常的認識不一致,應該引起重視。

圖質量濃度與林地面積比例關系

圖4 NH3-N質量濃度與耕地面積比例關系

2.2 實驗流域月尺度氮輸出特征

圖5 監(jiān)測斷面氮素月平均質量濃度過程

由圖5可以看出:

圖6 各監(jiān)測斷面TN質量濃度與或NH3-N質量濃度相關關系

2.3 嵌套子流域氮輸出特征

圖7 西源嵌套子流域月平均質量濃度變化過程比較

從圖7可以看出:

b. 在農(nóng)田非施肥季節(jié),西源流域各采樣點的NH3-N質量濃度變化較小,基本一致。軍事牌斷面、汪郢水庫下斷面集水區(qū)域的農(nóng)田面積比例小于0.22%,汪郢水庫下斷面以下流域為農(nóng)田區(qū)域,下游的三板橋、三岔河2斷面集水區(qū)域農(nóng)田比例分別為15.06%、21.30%,5月底、6月初正是當?shù)胤N植的雜交水稻插秧、返青季節(jié),水稻田施用底肥和返青肥,由于農(nóng)田施肥導致下游的三板橋、三岔河2個采樣斷面在5月和6月NH3-N質量濃度較大,而在上游林區(qū)的軍事牌、汪郢水庫下斷面,NH3-N質量濃度保持穩(wěn)定不變(圖7(b))。這說明,NH3-N質量濃度在5月、6月的突變是農(nóng)田化肥的使用導致的。

3 結 語

基于2012年10月—2013年9月滁州花山水文實驗流域氮素實驗觀測數(shù)據(jù),對流域的氮隨徑流流失的特征進行了分析,得出如下結論:

d. 研究區(qū)域汪郢左支斷面和軍事牌斷面集水區(qū)域林地比重高達99.92%以上,人類活動較少,CODMn質量濃度分別為1.72 mg/L和2.36 mg/L,分別達到Ⅰ類水和Ⅱ類水標準,但汪郢左支斷面和軍事牌斷面的TN質量濃度較高，分別為2.830 mg/L、4.028 mg/L,高于其集水區(qū)域農(nóng)田比重較大的竹園溝斷面和新壩斷面(分別為39.59%和35.63%),分別是竹園溝斷面和新壩斷面的1.42～2.51倍、2.02～3.57倍。人類活動較少、林地比重較大的集水區(qū)域徑流中的TN質量濃度高于農(nóng)田比重較大的集水區(qū)域徑流中TN質量濃度,這一事實與人們通常的認識不一致,值得進一步深入研究。

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Analysis of characteristics of nitrogen loss in Huashan hydrological experimental watershed

WANG Jianqun,GUO Kun, LIU Songping,WANG Yang

(CollegeofHydrologyandWaterResources,HohaiUniversity,Nanjing210098,China)

In this paper, the characteristics of nitrogen loss with runoff under different land use patterns in Huashan hydrological experimental watershed are studied. Based on the data of sample measurement of nitrogen mass concentrations from October, 2012 to September, 2013 in Huashan hydrological experimental watershed, the characteristics of nitrogen loss with runoff are analyzed. The results show that, there are higher total nitrogen mass concentration and nitrate nitrogen mass concentration in the runoff of the large proportion of the forest catchment as well as higher ammonia nitrogen mass concentration in the runoff of the large proportion of the farmland catchment. The mass concentration of total nitrogen highly correlates with the mass concentration of nitrate nitrogen in catchments with a higher proportion of forest, while the mass concentration of total nitrogen highly correlates with the mass concentration of ammonia nitrogen in catchments with a higher proportion of farmland. For the nested subcatchments the mass concentration of nitrate nitrogen decreased along the river channel downstream with the increase of catchment area and the reduction of forest coverage; in non-fertilization seasons, the mass concentration of total nitrogen decreased along the river channel downstream with the increase of catchment area and the reduction of forest coverage,and the mass concentration of ammonia nitrogen has a small change, while in fertilization seasons, the mass concentration of total nitrogen increased with the increase of the mass concentration of ammonia nitrogen. The study found that,in the catchment of the Junshipai section and the Wangyingzuozhi section, the proportion of forest is as high as more than 99.92% and human activities are quite limited, however, the mass concentration of total nitrogen in these sections are 2.830 mg/L and 4.039 mg/L respectively, being 1.42～2.51 times and 2.02～3.57 times higher than the one in the catchment of Zhuyuangou section and Xinba section respectively, where the proportion of farmland is 39.59% and 35.63% respectively. This fact is inconsistent with the common knowledge of people, which is worth further studying.

hydrological experimental watershed; nitrogen loss; non-point source pollution; land use

10.3880/j.issn.1004-6933.2015.02.001

水利行業(yè)公益性科研專項(201201026)

王建群(1960—),男,教授,博士,主要從事流域水文模擬及水資源規(guī)劃管理研究。 E-mail: wangjq@hhu.edu.cn

X522

A

1004-6933(2015)02-0001-06

2014-09-09 編輯：彭桃英)