康萍萍,許士國(guó),禹守泉

(1.大連理工大學(xué)水利學(xué)院水環(huán)境研究所,遼寧 大連　116024; 2.萊州市水務(wù)局,山東 萊州　261400)

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同位素溯源解析地下水庫(kù)對(duì)地下水氮分布影響

康萍萍1,許士國(guó)1,禹守泉2

(1.大連理工大學(xué)水利學(xué)院水環(huán)境研究所,遼寧 大連116024; 2.萊州市水務(wù)局,山東 萊州261400)

地下水庫(kù);氮氧同位素;環(huán)境影響;氮來(lái)源;IsoSource;氮貢獻(xiàn)比例

1　材料與方法

1.1研究區(qū)概況

王河流域位于山東省萊州市東北部。氣候?qū)儆谂瘻貛|亞季風(fēng)區(qū)大陸性氣候。多年平均氣溫為12.4℃,多年平均降水量為1 172.4 mm,多年平均蒸發(fā)量為2 039.6 mm。5月和6月蒸發(fā)量最大,是同期降雨量的9～16倍。地下水補(bǔ)給以大氣降水、王河地表水下滲和海水倒灌為主。流域內(nèi)土地利用以耕地為主,分布著村莊,東部近海區(qū)分布著大面積的海水養(yǎng)殖池。

自1977年以來(lái),王河流域多年持續(xù)干旱,水源緊缺,為了滿(mǎn)足工農(nóng)業(yè)及生活用水需要,流域內(nèi)開(kāi)始開(kāi)采地下水。到1980年,年平均超采地下水0.61億m3,使地下水位大幅度下降。1977—1992年間全市地下水位總計(jì)下降8.02 m,負(fù)值區(qū)達(dá)282.2 km2。超采改變了地下淡水與海水之間的極限平衡,造成海水大面積入侵。截至1992年底,海水入侵面積達(dá)到234.15 km2，近1.33萬(wàn)hm2農(nóng)田荒廢,平均減產(chǎn)40%。為了充分利用王河流域水資源,抑制萊州灣海水進(jìn)一步入侵，在王河下游修建了王河地下水庫(kù)。

王河地下水庫(kù)位于萊州市西北15 km處、西由村附近王河下游,距離萊州灣約2 km。王河地下水庫(kù)東倚山前崗地,西與渤海平原相接,東西寬5～9 km,南北為呈帶狀展布的沖洪積平原。地下水庫(kù)含水層巖性為礫質(zhì)粗砂、微含土礫質(zhì)粗礫、中細(xì)砂及沙壤土。王河地下水庫(kù)總庫(kù)容為5 693萬(wàn)m3,最大調(diào)節(jié)庫(kù)容為3 273萬(wàn)m3,最高運(yùn)行水位為1.0 m, 死水位為-9.0 m, 工業(yè)用水日供水量為3萬(wàn)t。地下壩主要包括北壩、西壩、副壩地下防滲墻工程。北壩西起倉(cāng)上村北,東至街西村西北,壩長(zhǎng)2.7 km,西壩南起朱由鎮(zhèn)武家村龍王河北岸,北與倉(cāng)上殘丘相接,壩長(zhǎng)8.25 km,副壩位于西由鎮(zhèn)新合村南,壩長(zhǎng)0.84 km。地下壩防滲墻采用高壓擺噴灌漿、高壓定噴灌漿和高壓旋噴灌漿。庫(kù)區(qū)內(nèi)土地利用類(lèi)型主要是耕地和村莊,庫(kù)區(qū)外土地利用類(lèi)型較為復(fù)雜,西部近海區(qū)主要是海水養(yǎng)殖,內(nèi)陸區(qū)主要是耕地和荒地,零星分布著村莊。

1.2地下水樣品采集

圖1　研究區(qū)位置及采樣點(diǎn)分布

1.3氮濃度分析

1.4氮氧同位素分析

(1)

式中:Rsa和Rst分別為樣品和標(biāo)準(zhǔn)樣品的15N/14N和18O/16O比值。

(2)

(3)

表1　王河地下水庫(kù)內(nèi)外地下水水樣檢測(cè)結(jié)果

2　結(jié)果分析與討論

2.1庫(kù)區(qū)內(nèi)外地下水中氮濃度特征

圖2　不同來(lái)源[12]的和及王河地下水庫(kù)的和

圖3　王河地下水庫(kù)庫(kù)區(qū)內(nèi)外地下水中與的關(guān)系

圖4　王河地下水庫(kù)庫(kù)內(nèi)地下水污染源貢獻(xiàn)比例

圖5　王河地下水庫(kù)庫(kù)外地下水污染源貢獻(xiàn)比例

3　結(jié)　語(yǔ)

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[ 8 ] VOSS M,DEUTSCH B,ELMGREN R,et al.Source identification of nitrate by means of isotopic tracers in the Baltic Sea catchments[J].Biogeosciences,2006,3(4):663-676.

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[10] 國(guó)家海洋監(jiān)測(cè)中心.海洋監(jiān)測(cè)規(guī)范(GB17378.4—2007)[S].北京:中國(guó)標(biāo)準(zhǔn)出版社,2007.

[11] 徐春英,李玉中,郝衛(wèi)平,等.反硝化細(xì)菌法結(jié)合痕量氣體分析儀/同位素比質(zhì)譜儀分析水體硝酸鹽氮同位素組成[J].分析化學(xué),2012,40(9):1360-1365.(XU Chunying,LI Yuzhong,HAO Weiping,et al.Analysis of nitrogen isotopic composition of nitrate in water by denitrifier method and trace-gas/isotope ratio mass spectrometry[J].Chinese Journal of Analytical Chemistry,2012,40(9):1360-1365.(in Chinese))

[12] GRANGER J,SIGMAN D M,LEHMANN M F,et al.Nitrogen and oxygen isotope fractionation during dissimilatory nitrate reduction by denitrifying bacteria[J].Limnology and Oceanography,2008,53(6):2533-2545.

[13] SIGMAN D M,GRANGER J,DIFIORE P J,et al.Coupled nitrogen and oxygen isotope measurements of nitrate along the eastern North Pacific margin[J].Global Biogeochemical Cycles,2005,19(4):GB4022.

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Analysis of influence of underground reservoir on nitrogen distribution through tracing of isotope source

KANG Pingping1, XU Shiguo1, YU Shouquan2

(1.InstituteofWaterandEnvironmentalResearch,FacultyofInfrastructureEngineering,DalianUniversityofTechnology,Dalian116024,China;2.LaizhouWaterAuthority,Laizhou261400,China)

Taking the Wanghe River Underground Reservoir in Shandong Province as an example, we used nitrogen and oxygen isotopes to analyze the distribution, sources, and transformation of nitrogen in groundwater. We used the IsoSource software to calculate the contribution ratios of different pollution sources, in order to analyze the influence of the underground reservoir on nitrogen distribution in groundwater. The results show that NO3-and TN in groundwater within the underground reservoir had higher concentrations and smaller spatial differences than they did outside of the underground reservoir, and the main nitrogen source was fertilizer in groundwater within the underground reservoir. Denitrification occurred in groundwater within the underground reservoir. The nitrogen in groundwater outside of the underground reservoir was mainly from mariculture and fertilizers. All the results mentioned above indicate that the underground reservoir prevents nitrogen from flowing horizontally, resulting in the accumulation of nitrogen and the enhancement of denitrification of nitrogen in groundwater within the underground reservoir.

underground reservoir; nitrogen and oxygen isotopes; environmental effects; nitrogen sources; IsoSource; nitrogen contribution ratio

10.3880/j.issn.1004-6933.2016.05.016

國(guó)家重點(diǎn)基礎(chǔ)研究發(fā)展計(jì)劃(973計(jì)劃)資助項(xiàng)目(2013CB430403)

康萍萍(1985—),女,博士研究生,研究方向?yàn)樗h(huán)境保護(hù)與修復(fù)。E-mail: kpp@mail.dlut.edu.cn

許士國(guó),教授。E-mail:sgxu@dlut.edu.cn

P597.2; X523

A

1004-6933(2016)05-0079-06

2015-11-24編輯：徐娟)