【摘要】：江心洲作為流域環(huán)境的重要自然檔案,對比不同形成原因和形成時間的江心洲上發(fā)育土壤的地球化學(xué)特征,不僅有助于認(rèn)識江心洲土壤的形成發(fā)育,也有助于揭示河流地貌及流域環(huán)境的演變。本文以長江安徽段15個面積較大的江心洲為研究區(qū),采集表層(0～20cm)和深層(150～180 cm)土壤樣品,探討研究區(qū)土壤地球化學(xué)特征,研究重金屬元素含量的分布特征和來源,揭示其富集成因和遷移轉(zhuǎn)化規(guī)律,并評價其潛在的生態(tài)風(fēng)險。得到下列主要研究結(jié)論:1.江心洲經(jīng)歷不斷消長、聯(lián)并等過程,有些江心洲歷史上變化很大,大部分洲體新于其初始形成時間。江心洲洲體的不斷演變是江心洲土壤化學(xué)風(fēng)化程度與江心洲初始形成時間不一致的主要原因。土壤化學(xué)風(fēng)化指數(shù)(CIA)作為土壤發(fā)育程度的指標(biāo),可以指示所在洲體的形成時間,即CIA空間分布一定程度上可以指示江心洲演變過程。2.長江安徽段江心洲表層、深層土壤中大多數(shù)元素特別是表生環(huán)境中活動性弱、人為擾動影響小的元素含量間具有顯著相關(guān)性,Cu、Pb、Zn、Hg和Cd等易受人為影響的元素在表層土壤出現(xiàn)明顯富集。表層土壤中Cu、Pb、Zn、As、Hg等重金屬平均含量均在我國土壤環(huán)境Ⅱ級質(zhì)量標(biāo)準(zhǔn)限值內(nèi),分別有44%和8%的樣品Cd含量超出了 Ⅱ級和Ⅲ級標(biāo)準(zhǔn)。3.不同江心洲之間以及同一江心洲內(nèi)部土壤重金屬含量的差異,主要與江心洲的成因及其發(fā)育演變過程有關(guān),近期淤長的部分,土壤重金屬元素含量通常比較高。4.研究區(qū)Cr、Ni、Cu、Zn、As和Pb等重金屬元素隨土壤發(fā)育呈累積趨勢,而Cd和Hg受土壤發(fā)育程度影響較小。土壤重金屬的富集主要與粒徑效應(yīng)、含鈣礦物對Cd等元素的固定,以及受燃煤影響的大氣沉降輸入有關(guān)。粒度效應(yīng)是影響研究區(qū)土壤重金屬分布的主要因素,土壤粒度端元對研究區(qū)土壤Ni、Cu、Pb、Zn、As、Cd的貢獻(xiàn)率均超過70%。鈣以及受燃煤影響的大氣沉降輸入對上述重金屬的影響已達(dá)到顯著性水平,有機(jī)質(zhì)和粒徑效應(yīng)對Hg的貢獻(xiàn)率分別為57.8%和36.1%,土壤中有機(jī)物質(zhì)的含量和成分的變化是決定Hg分布的主要控制因子。5.以長江沉積物背景值作為基線值進(jìn)行的地累積指數(shù)評價結(jié)果表明,研究區(qū)土壤重金屬富集程度為CdHgCuNiCrZnAsPb。潛在生態(tài)危害評價法顯示,三號洲、鳳凰洲重金屬污染的生態(tài)風(fēng)險最高,各江心洲出現(xiàn)不同程度的污染,且各采樣點(diǎn)都有兩種或更多的元素同時達(dá)到不同程度的污染水平,即表現(xiàn)為復(fù)合性的污染。
[Abstract]:Jiangxinzhou, as an important natural archives of watershed environment, not only helps to understand the formation and development of Jiangxinzhou soil, but also compares the geochemical characteristics of the developed soils on Jiangxinzhou with different formation reasons and time. It is also helpful to reveal the evolution of river geomorphology and watershed environment. In this paper, 15 large Jiangxinzhou in Anhui section of the Yangtze River are taken as the study area. The soil samples of surface (0~20cm) and deep layer (150m ~ 180cm) are collected, and the geochemical characteristics of soil and the distribution characteristics and sources of heavy metal contents in the study area are discussed. The enrichment causes, migration and transformation laws were revealed and its potential ecological risks were evaluated. The main conclusions are as follows: 1. Jiangxinzhou has experienced continuous growth and decline, joint merger and other processes. Some Jiangxinzhou has changed greatly in history, and most of the continental bodies were newly formed at the time of its initial formation. The continuous evolution of Jiangxinzhou body is the main reason why the soil chemical weathering degree of Jiangxinzhou is inconsistent with the initial formation time of Jiangxinzhou. Soil chemical weathering index (CIA), as an indicator of soil development, can indicate the formation time of the continental body, that is, the CIA spatial distribution can indicate the evolution process of Jiangxinzhou to some extent. In the surface layer of Jiangxinzhou in the Anhui section of the Yangtze River, the activity of most elements in the deep soil, especially in the supergene environment, is weak. There was a significant correlation between the contents of elements with small disturbance, such as CuPbHG, ZnHG, CD and so on, which were obviously enriched in the topsoil. The average contents of heavy metals such as Cu PbPb, ZnN, AsHg and so on in the surface soil were within the limit of grade 鈪，

本文編號：2128107