田慧娟 何 江 呂昌偉 樊慶云

(1.內(nèi)蒙古大學(xué)環(huán)境與資源學(xué)院 呼和浩特 010021;2.淮海工學(xué)院 江蘇連云港 222000;3.內(nèi)蒙古大學(xué)環(huán)境地質(zhì)研究所呼和浩特 010021)

黃河包頭段不同粒級(jí)沉積物中重金屬形態(tài)分布特征①

田慧娟1,2何 江1,3呂昌偉1,3樊慶云1,3

(1.內(nèi)蒙古大學(xué)環(huán)境與資源學(xué)院 呼和浩特 010021;2.淮海工學(xué)院 江蘇連云港 222000;3.內(nèi)蒙古大學(xué)環(huán)境地質(zhì)研究所呼和浩特 010021)

以黃河包頭段為研究對(duì)象,探討了該河段不同粒級(jí)沉積物中重金屬的形態(tài)分布特征,并估算了各粒級(jí)沉積物對(duì)各形態(tài)重金屬的貢獻(xiàn)率。結(jié)果表明,鐵錳氧化物結(jié)合態(tài)是黃河干流各粒級(jí)沉積物中Cu、Pb和Zn非穩(wěn)定態(tài)的主導(dǎo)形態(tài);總體上,黃河干支流沉積物中3種重金屬各形態(tài)含量均隨粒級(jí)增大而減小,表現(xiàn)明顯的粒度效應(yīng);重金屬形態(tài)分布的粒度效應(yīng)是沉積物粒徑大小與沉積物中有機(jī)質(zhì)、碳酸鹽、鐵氧化物和錳氧化物等活性組分含量共同作用的結(jié)果,粒徑是主控因素;Fe的含量是影響不同粒級(jí)黃河包頭段沉積物中重金屬的主導(dǎo)形態(tài)——鐵錳氧化物結(jié)合態(tài)的主要因素;同一粒級(jí)沉積物中,不同重金屬同一形態(tài)的含量總體有Zn>Pb>Cu的規(guī)律,與黃河中游沉積物重金屬背景值Zn>Cu>Pb的研究結(jié)果不盡一致,揭示來(lái)自包頭市工業(yè)廢水的外源重金屬對(duì)黃河水體沉積物的疊加影響。有機(jī)質(zhì)結(jié)合態(tài)和鐵錳氧化物結(jié)合態(tài)分別為支流各粒級(jí)沉積物中Cu及Pb、Zn的主導(dǎo)形態(tài)。不同粒級(jí)沉積物質(zhì)量分?jǐn)?shù)的差異導(dǎo)致不同粒級(jí)沉積物對(duì)重金屬形態(tài)分布的實(shí)際貢獻(xiàn)率不同。總體上,D5和D3粒級(jí)對(duì)黃河包頭段沉積物重金屬的形態(tài)貢獻(xiàn)率為大,其潛在生態(tài)風(fēng)險(xiǎn)不容忽視。

黃河包頭段 沉積物粒級(jí) 重金屬形態(tài) 粒度效應(yīng)

水體顆粒物的基本特征為不均一性或非均質(zhì)性,不同粒級(jí)顆粒物在礦物組成、比表面積、反應(yīng)活性點(diǎn)、帶電荷數(shù)等方面均有較大差異[1～8]。由粒徑大小導(dǎo)致的上述性質(zhì)的差異也必將影響不同粒徑顆粒物中重金屬的形態(tài)分布特征。盡管沉積物中重金屬的形態(tài)表現(xiàn)一定的粒度效應(yīng)規(guī)律,但因不同研究者在研究粒度效應(yīng)時(shí)采用的粒徑范圍不盡一致,使研究結(jié)果存在差異且沒(méi)有可比性。研究業(yè)已證明,重金屬主要富集在<63μm的沉積顆粒物中且<63μm的顆粒物代表了水體沉積物中可被再懸浮部分[9],因而<63 μm的顆粒物是學(xué)者們普遍接受和公認(rèn)的研究介質(zhì)。以往研究中,研究者們對(duì)>50μm顆粒物的分級(jí)提取和形態(tài)分析給予了更多關(guān)注,而對(duì)<50μm的顆粒物再行分級(jí)進(jìn)行形態(tài)分析研究則為數(shù)較少。本研究采用沉降法,從<63μm的顆粒物中依次提取<4μm、4～16μm、16～32μm、32～50μm和50～63μm等5個(gè)粒級(jí)的顆粒物,在此基礎(chǔ)上,系統(tǒng)開(kāi)展了不同粒級(jí)黃河顆粒物中重金屬的形態(tài)分析實(shí)驗(yàn)研究,闡述了重金屬形態(tài)在不同粒級(jí)沉積物中的分布特征,探討了不同粒級(jí)沉積物中重金屬形態(tài)分布的差異,以期揭示不同粒級(jí)沉積物中重金屬的污染程度及其生物危害性。

1 樣品采集與分析方法

圖1 黃河包頭段采樣點(diǎn)位示意圖Fig.1 Location of sampling points in the Yellow River

于2004年9月在黃河包頭段干流打不素(A站位)、昆都侖河入黃河口下游(B站位)、四道沙河入黃河口下游(C站位)和磴口(D站位)及兩條接納工業(yè)污水的支流昆都侖河(E站位)和四道沙河(F站位)系統(tǒng)采集了柱狀沉積物樣品(圖1)。采樣站位布設(shè)在水流較緩,沉積較好的地帶。沉積物用挪威Swedaq公司產(chǎn)KCmod A och B型無(wú)擾動(dòng)沉積物采樣器采集,沉積物柱和上覆水柱界面清晰,現(xiàn)場(chǎng)用膠管將上層水相吸棄后,裝入聚乙烯塑料袋,回實(shí)驗(yàn)室自然風(fēng)干,攪勻篩取<63μm部分備用。

依據(jù)國(guó)際通用的伍登-溫德華氏(Udden-Wentworth)等比制Φ值粒級(jí)標(biāo)準(zhǔn),根據(jù)Stokes定律[10],采用沉降法,從<63μm的顆粒物中依次提取<4μm (D1)、4～16μm(D2)、16～32μm(D3)、32～50μm (D4)和50～63μm(D5)等5個(gè)粒級(jí)的顆粒物。黃河沉積物的實(shí)測(cè)平均比重為2.65 g/cm3。

形態(tài)分析采用Tessier的連續(xù)提取法[11].u、Pb、Zn均用火焰原子吸收分光光度法(日立公司產(chǎn)Z-5000型)測(cè)定,所有重金屬測(cè)定均以中國(guó)國(guó)家標(biāo)準(zhǔn)樣品(Cu,GSB 02-1182-2000;Pb,GSB 02-1183-2000;Zn,GSB 02-1184-2000)為質(zhì)控樣,相對(duì)誤差5%。實(shí)驗(yàn)所用藥品除各種酸為優(yōu)級(jí)純外,其余均為分析純,水為二次去離子水。實(shí)驗(yàn)及采樣所用玻璃及聚乙烯容器均在14%的硝酸中浸泡24 h以上,并用二次去離子水沖洗后低溫烘干。

2 結(jié)果與討論

2.1 干流不同粒級(jí)沉積物中重金屬形態(tài)分布特征

表生環(huán)境下,沉積物中原生相(殘?jiān)鼞B(tài))重金屬一般不再參與水-沉積物系統(tǒng)的再平衡分配,外源金屬元素主要疊加于沉積物次生相(非穩(wěn)定態(tài))中。因此,本文著重討論非穩(wěn)定態(tài)重金屬的分布。

黃河包頭段各粒級(jí)沉積物中,Cu和Pb非穩(wěn)定態(tài)含量的大致順序?yàn)殍F錳氧化物結(jié)合態(tài)>碳酸鹽結(jié)合態(tài)>有機(jī)質(zhì)結(jié)合態(tài);Zn的非穩(wěn)定態(tài)含量大致順序?yàn)殍F錳氧化物結(jié)合態(tài)>有機(jī)質(zhì)結(jié)合態(tài)>碳酸鹽結(jié)合態(tài), (圖2).n的非穩(wěn)定態(tài)含量順序與Cu、Pb有一定差別,在B、C站位其有機(jī)質(zhì)結(jié)合態(tài)的含量有所升高,尤其在D2-D5粒級(jí)顆粒物中?？傮w上,3種重金屬各形態(tài)含量均隨粒級(jí)增大而減小,表現(xiàn)明顯的粒度效應(yīng)。

圖2 干流表層沉積物(0～10 cm)中重金屬形態(tài)含量的分布特征Fig.2 The speciation distribution character of heavy metal in the surface sediments from themainstream

同一粒級(jí)沉積物中,不同元素同一形態(tài)的含量總體有Zn>Pb>Cu的規(guī)律,與黃河中游沉積物重金屬背景值Zn>Cu>Pb的研究結(jié)果[12]不盡一致。據(jù)包頭市環(huán)境監(jiān)測(cè)站監(jiān)測(cè)資料顯示,2002-2004年包頭市排污河流污染物入黃量平均值以Zn為最(132.63 t/a),Pb入黃量(22.67 t/a)約是Cu(4.68 t/a)的5倍,這可能是導(dǎo)致黃河包頭段沉積物中Pb含量高于Cu的直接原因,同時(shí)揭示了來(lái)自包頭市工業(yè)廢水的外源重金屬對(duì)黃河水體沉積物的疊加影響。

2.2 支流不同粒級(jí)沉積物中重金屬形態(tài)分布特征

昆都侖河(E站位)和四道沙河(F站位)沉積物中(圖3),各粒級(jí)沉積物Cu的非穩(wěn)定態(tài)含量順序?yàn)橛袡C(jī)質(zhì)結(jié)合態(tài)>>鐵錳氧化物結(jié)合態(tài)>碳酸鹽結(jié)合態(tài);Pb和Zn的非穩(wěn)定態(tài)含量順序均為鐵錳氧化物結(jié)合態(tài)>碳酸鹽結(jié)合態(tài)≥有機(jī)質(zhì)結(jié)合態(tài);有機(jī)質(zhì)結(jié)合態(tài)和鐵錳氧化物結(jié)合態(tài)分別為支流各粒級(jí)沉積物中Cu及Pb、Zn的主導(dǎo)形態(tài)。有機(jī)質(zhì)結(jié)合態(tài)在Cu的非穩(wěn)定態(tài)中占絕對(duì)主導(dǎo)地位,這既與支流中有機(jī)質(zhì)的含量高直接相關(guān),又進(jìn)一步說(shuō)明了有機(jī)質(zhì)對(duì)Cu的地球化學(xué)親合性比Pb和Zn強(qiáng)。支流沉積物中,Cu和Zn的各非穩(wěn)定態(tài)含量及E站位Pb的各非穩(wěn)定態(tài)含量均隨粒級(jí)增大而減小,表現(xiàn)顯著的粒度效應(yīng).站位Pb的鐵錳氧化物結(jié)合態(tài)和碳酸鹽結(jié)合態(tài)的含量盡管也表現(xiàn)出粒度效應(yīng),但不及E站位明顯。有趣的是, F站位Pb的有機(jī)質(zhì)結(jié)合態(tài)含量表現(xiàn)出隨粒級(jí)增大而增大的現(xiàn)象,這可能與四道沙河稀土行業(yè)酸性廢水的粗粒懸浮沉積物(細(xì)小顆粒的固結(jié)體)本身含有較高Pb的硫化物有關(guān).站位沉積物中,Cu、Pb和Zn各非穩(wěn)定態(tài)的含量及非穩(wěn)定態(tài)含量之和均遠(yuǎn)較F站位高,這與昆都侖河是接納城市工業(yè)廢水的主要河流的監(jiān)測(cè)結(jié)果相一致(表1)。此外,黃河包頭段干支流不同粒級(jí)沉積物中3種重金屬的形態(tài)含量對(duì)比表明(圖2和圖3),2條支流沉積物中各形態(tài)重金屬的含量均遠(yuǎn)高于干流,也表明接納大量工業(yè)廢水的2條支流對(duì)黃河包頭段重金屬的污染迭加作用。相較而言,昆都侖河對(duì)黃河包頭段Pb和Zn的貢獻(xiàn)較大,四道沙河對(duì)Cu的貢獻(xiàn)較大。

2.3 不同粒級(jí)沉積物對(duì)重金屬形態(tài)分布的貢獻(xiàn)率

表1 排污河污染物入黃量Table1 The discharge amount of pollution from the two branches

圖3 支流表層沉積物(0～10 cm)中重金屬形態(tài)含量的分布特征Fig.3 The speciation distribution character of heavymetal in the surface sediments from the branch

黃河沉積物受外界環(huán)境如水動(dòng)力條件,pH,Eh等因素影響頗大,沉積物-水界面間的交換反應(yīng)頻繁復(fù)雜。不同粒級(jí)沉積物中各形態(tài)重金屬含量的分布特征尚不能全面反映沉積物中各形態(tài)重金屬對(duì)水環(huán)境及水生生態(tài)系統(tǒng)的影響。不同粒級(jí)顆粒物的質(zhì)量分?jǐn)?shù)直接影響重金屬形態(tài)分布的質(zhì)量分?jǐn)?shù),進(jìn)而影響對(duì)重金屬潛在危害評(píng)價(jià)的客觀性。探尋顆粒物粒級(jí)對(duì)重金屬形態(tài),特別是對(duì)非穩(wěn)定態(tài)分布的影響,揭示不同粒級(jí)顆粒物中重金屬的潛在危害性,對(duì)黃河包頭段水體重金屬污染防治更具實(shí)際意義。

圖4 各粒級(jí)對(duì)重金屬形態(tài)的貢獻(xiàn)率Fig.4 Contribution rate of grain size fractions to heavymetal

由圖4可看出,不同粒級(jí)顆粒物質(zhì)量分?jǐn)?shù)的變化趨勢(shì)與各形態(tài)重金屬的質(zhì)量分?jǐn)?shù)基本相同,亦即質(zhì)量分?jǐn)?shù)大的顆粒物粒級(jí)對(duì)重金屬各形態(tài)的貢獻(xiàn)率也大.站位中各粒級(jí)對(duì)重金屬形態(tài)的貢獻(xiàn)率依序?yàn)镈5> D4、D2>D3>D1;B站位為D4>D3、D2>D5>D1;C站位為D3>>D5>D4、D2>D1;D站位為D5>>D4 >D3>D2>D1。

A站位中對(duì)重金屬形態(tài)貢獻(xiàn)率最大的粒級(jí)為D5,B站位為D3、D4、D5,C站位為D3、D5,D站位為D5。總體上,D5和D3粒級(jí)對(duì)黃河包頭段沉積物重金屬的形態(tài)貢獻(xiàn)率為大。這既反映了黃河水動(dòng)力條件的復(fù)雜多變,從而導(dǎo)致沉積粒序旋回的復(fù)雜多變,使得黃河包頭段不同區(qū)段沉積物粒度組成有較大差異,同時(shí)也揭示沉積物的粒度組成對(duì)重金屬的含量及其形態(tài)分布有重要影響。顆粒物的粒級(jí)不同,其礦物組成、比表面積、反應(yīng)活性點(diǎn)、帶電荷數(shù)等均不同,從而導(dǎo)致不同粒級(jí)顆粒物表面與重金屬離子的結(jié)合力不同。一般而言,顆粒物的粒級(jí)越大,其與重金屬離子的結(jié)合力越弱,賦存其中的重金屬就越有可能重新釋放返回水體而造成二次污染。因此,在評(píng)價(jià)重金屬的潛在危害時(shí),既要考慮重金屬的形態(tài)含量和分布,又要考慮各粒級(jí)顆粒物質(zhì)量分?jǐn)?shù)的影響,方可能做出無(wú)偏見(jiàn)的評(píng)價(jià)。就黃河包頭段本身而言,因D5和D3粒級(jí)對(duì)重金屬形態(tài)的貢獻(xiàn)率較大,其潛在生態(tài)風(fēng)險(xiǎn)不容忽視。

2.4 重金屬形態(tài)分布的粒度效應(yīng)

研究表明,干流4個(gè)站位不同粒徑沉積物中有機(jī)質(zhì)、碳酸鹽、鐵氧化物和錳氧化物等活性組分含量與平均粒徑呈負(fù)相關(guān)關(guān)系(圖5)。有機(jī)質(zhì)與沉積物粒徑呈顯著相關(guān),相關(guān)系數(shù)為-0.975(p<0.005);碳酸鹽與沉積物粒徑亦呈顯著相關(guān),相關(guān)系數(shù)為-0.944(p<0.05)。4種活性組分的含量均隨粒徑增大而明顯降低,揭示顆粒物理化性質(zhì)自身表現(xiàn)的粒度效應(yīng)特征導(dǎo)致了顆粒物對(duì)重金屬形態(tài)分布的粒度效應(yīng),粒度效應(yīng)是沉積物粒徑大小與活性組分含量共同作用的結(jié)果,粒徑是主控因素。

圖5 碳酸鹽、有機(jī)質(zhì)、三氧化二鐵和二氧化錳與平均粒徑的相關(guān)關(guān)系Fig.5 Correlation between the contents of carbonate, organicmatter,ferric oxide,manganese dioxide and themean grain size

相關(guān)分析表明(表2),干流4個(gè)站位沉積物中,碳酸鹽和有機(jī)質(zhì)兩種活性組分均與3種重金屬呈顯著相關(guān);鐵氧化物除與個(gè)別重金屬形態(tài)相關(guān)性不顯著外,也表現(xiàn)出顯著相關(guān)關(guān)系;錳氧化物與所有重金屬形態(tài)均不存在顯著相關(guān)關(guān)系。

盡管隨粒級(jí)變化,碳酸鹽和有機(jī)質(zhì)與Cu、Pb的相應(yīng)相態(tài)表現(xiàn)顯著正相關(guān),但因有機(jī)質(zhì)在各粒級(jí)黃河沉積物中的含量(一般小于1%)遠(yuǎn)低于碳酸鹽,故各粒級(jí)沉積物中有機(jī)質(zhì)結(jié)合態(tài)的含量均低于碳酸鹽結(jié)合態(tài)。3種重金屬的鐵錳氧化物結(jié)合態(tài)與碳酸鹽、有機(jī)質(zhì)及鐵的氧化物相關(guān)性均較好,說(shuō)明黃河包頭段沉積物中3種重金屬非穩(wěn)定態(tài)的主導(dǎo)形態(tài)-鐵錳氧化物結(jié)合態(tài)是碳酸鹽、有機(jī)質(zhì)和鐵的氧化物共同作用的結(jié)果。黃河包頭段不同粒級(jí)沉積物中Fe、Mn的百分含量分別介于3.8%～6.5%和0.03%～0.06%之間,Fe的含量遠(yuǎn)高于Mn。相關(guān)分析結(jié)果表明,鐵氧化物與3種重金屬鐵錳氧化物結(jié)合態(tài)的相關(guān)系數(shù)為0.95～0.96,而錳氧化物與3種重金屬鐵錳氧化物結(jié)合態(tài)的相關(guān)系數(shù)僅為0.50～0.64,鐵氧化物與3種重金屬鐵錳氧化物結(jié)合態(tài)的相關(guān)性遠(yuǎn)好于錳氧化物。由此可知,與Mn相比,Fe的含量是影響不同粒級(jí)黃河包頭段沉積物中鐵錳氧化物結(jié)合態(tài)重金屬含量的主要因素。

3 主要結(jié)論

表2 Cu、Pb、Zn各形態(tài)及總量與碳酸鹽、有機(jī)質(zhì)、鐵錳氧化物含量的相關(guān)性分析Table2 Correlation between the contents of carbonate,organicmatter,ferric oxide,manganese dioxide and speciation and total concentration of heavy metal

總體上,黃河干支流沉積物中3種重金屬各形態(tài)含量均隨粒級(jí)增大而減小,表現(xiàn)明顯的粒度效應(yīng)。重金屬形態(tài)分布的粒度效應(yīng)是沉積物粒徑大小與沉積物中有機(jī)質(zhì)、碳酸鹽、鐵氧化物和錳氧化物等活性組分含量共同作用的結(jié)果,粒徑是主控因素.e的含量是影響不同粒級(jí)黃河包頭段沉積物中重金屬的主導(dǎo)形態(tài)-鐵錳氧化物結(jié)合態(tài)的主要因素。同一粒級(jí)沉積物中,不同重金屬同一形態(tài)的含量總體有Zn> Pb>Cu的規(guī)律,與黃河中游沉積物重金屬背景值Zn >Cu>Pb的研究結(jié)果不盡一致,揭示來(lái)自包頭市工業(yè)廢水的外源重金屬對(duì)黃河水體沉積物的疊加影響。

不同粒級(jí)沉積物質(zhì)量分?jǐn)?shù)的差異導(dǎo)致不同粒級(jí)沉積物對(duì)重金屬形態(tài)分布的實(shí)際貢獻(xiàn)率不同。在評(píng)價(jià)重金屬的潛在危害時(shí),既要考慮重金屬的形態(tài)含量和分布,又應(yīng)考慮各粒級(jí)顆粒物質(zhì)量分?jǐn)?shù)的影響,才可能做出無(wú)偏見(jiàn)的評(píng)價(jià)?？傮w上,D5和D3粒級(jí)對(duì)黃河包頭段沉積物重金屬的形態(tài)分布貢獻(xiàn)率為大,其潛在生態(tài)風(fēng)險(xiǎn)不容忽視。

References)

1 范德江,楊作升。長(zhǎng)江、黃河沉積物中碳酸鹽組成及差異[J]。自然科學(xué)進(jìn)展,2002,12(1):60-64[Fan Dejiang,Yang Zuosheng.The differences in the composition of carbonate sediments from Yangtze River and Yellow River[J].rogress in Natural Science,2002,12 (1):60-64]

2 陳靜生,王飛越。中國(guó)東部河流沉積物中重金屬含量與沉積物主要性質(zhì)的關(guān)系[J]。環(huán)境化學(xué),1996,25(1):8-14[Chen Jingsheng,Wang Feiyue.Relation of geochemical and surface properties to heavy metal concentrations of sediments from Eastern Chinese rivers [J].nvironmental Chemistry,1996,25(1):8-14]

3 陳靜生,陳江麟,王飛躍。中國(guó)東部主要河流沉積物的比表面積及其地域差異研究[J]。環(huán)境化學(xué),1994,13(6):479-485[Chen Jingsheng,Chen Jianglin,Wang Feiyue.Specific surface areas of the sediments from themain rivers in the Eastern China[J].nvironmental Chemistry,1994,13(6):479-485]

4 王飛越,陳靜生。中國(guó)東部河流沉積物樣品表面性質(zhì)的初步研究[J]。環(huán)境科學(xué)學(xué)報(bào),2002,20(6):682-687[Wang Feiyue,Chen Jingsheng.Preliminary research on surface properties of river surface sediment in eastern China[J].cta Scientiae Circumstantiae,2002, 20(6):682-687]

5 王波,張耀明,鮑士旦。不同土壤不同粒級(jí)顆粒供鉀能力的研究[J]。蘇州大學(xué)學(xué)報(bào),2004,20(1):77-81[Wang Bo,Zhang Yaoming,Bao Shidan.Evaluation of potassium supplying power of soils and its particles[J].ournal of Suzhou University。2004,20(1):77-81]

6 楊毅,劉敏,侯立軍。長(zhǎng)江口潮灘含氯有機(jī)物的分布及與TOC、粒度的相關(guān)性[J]。上海環(huán)境科學(xué),2002,21(9):530-535[Yang Yi, Liu Min,Hou Lijun.Distribution of polychlorinated organic compound in Yangtze Estuary and its correlation with TOC and particle size[J].hanghai Environmental Science,2002,21(9):530-535]

7 徐陽(yáng)春,沈其榮,茆澤圣。長(zhǎng)期施用有機(jī)肥對(duì)土壤及不同粒級(jí)中有機(jī)磷含量與分配的影響[J]。土壤學(xué)報(bào),2003,40(4):593-598 [Xu Yangchun,Shen Qirong,Mao Zesheng.Influences of long-term fertilization on the content and distribution of organic P in soil and soil particle size[J].cta Pedological Sinica,2003,40(4):593-598]

8 汪景寬,張繼宏,王雷,等。棕壤不同粒級(jí)微團(tuán)聚體中磷素的保持與供應(yīng)[J]。土壤通報(bào),2001,32(3):113-115[Wang Jingkuan, Zhang Jihong,Wang Lei,et al.Phosphorous retention and supply in microaggergates of brown earth with different fertility levels in Liaoning province[J].hinese Journal of Soil Science,2001,32(3):113-115]

9 陳靜生,王飛躍。論小于63μm粒級(jí)作為水體顆粒物重金屬研究介質(zhì)的合理性及有關(guān)粒級(jí)轉(zhuǎn)換模型研究[J]。環(huán)境科學(xué)學(xué)報(bào), 1994,14(4):419-425[Chen Jingsheng,Wang Feiyue.On reasonability of grain size less than 63μm as researchmedia of granular heavy metal in water body and conversionmodel of grain grade[J].ournal of Environmental Science,1994,14(4):419-425]

10 中國(guó)科學(xué)院南京土壤研究所。土壤理化分析[M]。上海:上?？茖W(xué)技術(shù)出版社,1978:4-7,474-480[Nanjing Institute of Soil Science,Chinese Academy of Sciences.Physical and Chemical Analysis of Soil[M].hanghai:Shanghai Science and Technology Press, 1978:4-7,474-480]

11 Tessier A,Campbell PG C,Sisson M.Sequential extraction procedure for the speciation of particulate trace metals[J].nalytical Chemistry,1979,51(7):844-851

12 蔣廉潔,李學(xué)夢(mèng)。黃河中游干流泥沙中的金屬元素背景值及污染評(píng)價(jià)[J]。鄭州工學(xué)院學(xué)報(bào),1994,15(4):82-89[Jiang Lianjie, Li Xuemeng.Heavymetal elementbackground values on the sediment in themiddle reach of the yellow river and assess present level of pollution[J].ournal of Zhengzhou University of Technology,1994,15 (4):82-89]

Species and Distribution of Heavy M etals in Different Size Fractions of Sediments from the Baotou Section of the Yellow River

TIAN Hui-juan1,2HE Jiang1LüChang-wei1FAN Qing-yun1
(1.College of Environment and Resources,Inner Mongolia University,Huhhot 010021;2.Huaihai Institute of Technology, Lianyungang,Jiangsu 222005;3.Institute of Enviromental Geology,Inner M ongalia.University,Huhhot 010021)

The Yellow River contains large amounts of sands,resulting in a peculiar hydraulic condition which is characterized by amagnificent interface between the particulates and water.In addition,Baotou section of the Yellow River suffers from severe heavy metal pollution receiving the industrial discharges from the Baotou city.Therefore, this study was carried out on Baotou section of the Yellow River based on its representativeness on themechanism of heavymetal adsorption on water-sediment interface,and on the heavy metal spatial distribution,mobilization,transformation,and accumulation effects in sediments.Because of their persistence in the environment,heavymetals often pose threats to aquatic lives and plants in the environment.Based on the theories and methods of environmental geochemistry,biogeochemistry,pollution ecology and modern sedimentology,the speciation distribution characters of heavymetals such as Cu,Pb,Zn in the different grain sizes sediments and the contribution of the different grain sizes sediments on the concentrations of differentheavymetals speciation were discussed in thiswork.The results indicated that the bound to Fe-Mn oxide was the dominant form of non-steady-state of Cu,Pb,and Zn in different grain sizes sediments from the Yellow River,and therewere the concentration order of the bound to Fe-Mn oxide>the bound to carbonate>the bound to organicmatter for Cu and Pb,while the bound to Fe-Mn oxide>the bound to organicmatter>the bound to carbonate for Zn.The grain-size effects of the different species for the selected heavymetalswere observed in thiswork which was the results of particle size and active components such as organic matter,carbonate and Fe-Mn oxides in different grain sizes sediments from the studied section of the Yellow River.In all of the factors, the particle sizes played a key role in affecting the concentration of different species of the selected heavy metals.Based on the experiments,itwas found that the bound to Fe-Mn oxides was the dominant form in different size fractions of sediments from Baotou Section of the Yellow River,and its concentration wasmainly influenced by the content of Fe oxide in differentgrain sizes sediments from the studied section of the Yellow River.The results also showed that the concentrations of each species were ranked as Zn>Pb>Cu in the same size fraction sediments,which was not consistentwith the background values of heavymetals in sediment from themidstream of the Yellow River.The differences found in thiswork indicated that therewere exogenous heavymetals inputs from the industrialwastewater of the Baotou City from another point of view.The dominant forms of Cu,Pb and Zn are Fe-Mn oxides bound and bound to organic matter in sediments from the tributaries of the Yellow River.From the comparison between the main stream and the tributaries of the Baotou Section of the Yellow River,it could be found that the concentration of each species for the selected heavymetals in the tributarieswere obviously high than those in themain stream which was also indicated the exogenous heavymetals inputs from the industrialwastewater of the Baotou City.By the comparison of the two tributaries,the pollution superposition of Pb and Zn from the Kundulun Riverwere higher than those from the Sidaosha River,while the pollution superposition of Cu from the Sidaosha Riverwas higher than those from the Kundulun River.The correlation analysis indicated that there were negative correlation between the mean grain sizes and the concentrations of organicmatter,carbonate,Fe oxide and Mn oxide in the sedimentswith differentgrain sizes from the main stream of the Yellow River.The results showed that therewere significant negative correlation found between the organic matter and themean grain sizeswith the correlation coefficient of-0.975(p<0.005);and there were significant negative correlation found between the carbonate and themean grain sizes with the correlation coefficient of-0.944(p<0.05).he contribution ofmass fraction for different size sediments to speciation distribution was different.The ordre of contribution rate for differentgrain sizes sedimentswas D5>D4,D2>D3>D1 at Site A;D4 >D3,D2>D5>D1 at Site B;D3?D5>D4,D2>D1 at Site C;D5?D4>D3>D2>D1 at Site D.Overall,the contribution on heavy metal speciation in sediments from Baotou Section of the Yellow River was mainly caused by the size fractions of D5 and D3.hus,the potential ecological risk caused by the different grain size sediments can not be ignored,especially the size fractions of D5 and D3.

Baotou section of Yellow River;size fraction of sediment;speciation of heavy metal;grain-size effect

田慧娟 女 1979年出生 碩士研究生 環(huán)境地球化學(xué)

何江 E-mail:ndjhe@imu.edu.cn

P512.2 P595

A

1000-0550(2011)04-0776-07

①國(guó)家自然科學(xué)基金項(xiàng)目(批準(zhǔn)號(hào):40363001)、內(nèi)蒙古自然科學(xué)基金(編號(hào):990303-1)、內(nèi)蒙古教育廳重點(diǎn)項(xiàng)目基金(編號(hào):ZD9901)、內(nèi)蒙古“ 321人才工程”基金(內(nèi)人(99)51)和教育部高等院校骨干教師項(xiàng)目基金聯(lián)合資助。

2010-04-06;收修改稿日期:2010-09-25