【摘要】：本文以新疆瑪納斯河流域莫索灣灌區(qū)為研究區(qū)域,通過(guò)區(qū)域調(diào)查分析和田間定位試驗(yàn)選取5a、10a、20a、30a棉田土壤與荒地土壤對(duì)比等方法,分析棉田耕作過(guò)程中土壤重金屬的剖面分布特征和累積狀況;利用地統(tǒng)計(jì)插值方法估測(cè)出研究區(qū)表層土壤重金屬含量的空間分布規(guī)律,為該灌區(qū)的棉田土壤環(huán)境質(zhì)量保護(hù)提供基礎(chǔ)數(shù)據(jù);選取灌區(qū)污染較重的Cr元素為改良對(duì)象,通過(guò)室內(nèi)培養(yǎng)試驗(yàn),揭示了幾種化學(xué)改良劑對(duì)土壤中Cr的形態(tài)分布及轉(zhuǎn)化的影響,得到以下主要結(jié)論:(1)棉田土壤(0~100 cm)重金屬Cr、Ni、Cu、As、Pb含量分別為90.65、32.22、52.64、10.90、13.86 mg/kg,荒地土壤分別為78.21、32.34、44.16、9.48、13.91 mg/kg,Cr、Ni、Cu、As在棉田土壤中的含量顯著大于荒地,且均高于新疆土壤背景值,Pb含量?jī)烧呦嗖畈淮?均低于背景值。棉田土壤中5種重金屬元素的變異系數(shù)均大于荒地土壤,屬于中等變異。(2)對(duì)5a、10a、20a、30a棉田土壤不同剖面分布特征發(fā)現(xiàn),隨著連作年限的增加,Cr、Ni、Cu、As、Pb五種重金屬在1 m土層均有所增加,且不同連作年限間差異顯著;表層土壤的重金屬含量顯著高于底層,連作30年的棉田土壤垂直分布趨勢(shì)更為明顯。通過(guò)土壤元素相關(guān)性分析發(fā)現(xiàn),棉田土壤中Cr、Cu、As和Ni重金屬元素的累積主要由磷肥的施入造成的,而荒地土壤中重金屬元素與N、P、K、pH之間的相關(guān)性不顯著,進(jìn)一步說(shuō)明了棉田連作過(guò)程化肥的長(zhǎng)期大量施入會(huì)對(duì)土壤重金屬產(chǎn)生累積。(3)對(duì)便攜式X射線熒光光譜儀的實(shí)用性進(jìn)行了建模探究和模型驗(yàn)證,驗(yàn)證模型R2分別為0.9124、0.8979、0.7723、0.8729 mg/kg,斜率與截距得到優(yōu)化,較接近理想模型,校準(zhǔn)后的檢測(cè)結(jié)果與傳統(tǒng)實(shí)驗(yàn)室ICP-AES檢測(cè)結(jié)果呈極顯著正相關(guān)關(guān)系。通過(guò)二次采樣的36~50號(hào)土壤樣品組建的驗(yàn)證模型可以充分證明PXRF異位法的實(shí)用性和校準(zhǔn)曲線的高準(zhǔn)確性。(4)通過(guò)使用便攜式X射線熒光光譜儀對(duì)灌區(qū)表層土壤重金屬含量進(jìn)行速效測(cè)定,土壤重金屬含量變異函數(shù)和模型擬合發(fā)現(xiàn):Cr、As以指數(shù)模型最佳,Ni、Pb以高斯模型最佳,Cu以球型模型最佳,Cr、Cu的塊金效應(yīng)分別為0.86、0.92,空間自相關(guān)性較弱,受人為隨機(jī)因素影響較大,Ni、As、Pb的塊金效應(yīng)分別為0.57、0.41和0.46,空間相關(guān)性中等,受人為隨機(jī)因素和空間結(jié)構(gòu)因素的共同作用影響;研究區(qū)當(dāng)前整體污染評(píng)價(jià)結(jié)果為Cr、As兩種元素趨近輕微污染水平,Ni對(duì)土壤環(huán)境造成輕度污染。(5)利用盆栽試驗(yàn)研究不同改良劑對(duì)土壤重金屬Cr的修復(fù)效果研究發(fā)現(xiàn):改良劑的施入可以抑制Cr的可交換態(tài)含量,同時(shí)在一定程度上會(huì)增加土壤pH值,隨著污染濃度的增加,對(duì)pH值影響力逐漸下降,但始終高于CK。4種改良劑中,以鈣鎂磷肥的改良效果最佳,土壤中可交換態(tài)含量先降低后升高,殘?jiān)鼞B(tài)含量先升高后降低,最終表現(xiàn)為可交換態(tài)含量降低。石灰的改良效果僅次于鈣鎂磷肥,它主要使Cr的可交換態(tài)轉(zhuǎn)化為鐵錳氧化物結(jié)合態(tài)。兩種改良劑效果顯著高于活性炭與秸稈,但其對(duì)Cr可交換態(tài)含量降低的影響時(shí)間較短,在第42天后可交換態(tài)含量出現(xiàn)回升�；钚蕴恐饕獙⒖山粨Q態(tài)轉(zhuǎn)化為有機(jī)物結(jié)合態(tài),且在第56天后其含量出現(xiàn)升高趨勢(shì)的現(xiàn)象,但改良效果低于鈣鎂磷肥和石灰。而秸稈施入對(duì)土壤pH值和Cr可交換態(tài)含量影響均不顯著,這與改良的施入量和培養(yǎng)時(shí)間有關(guān)。綜上所述,棉田長(zhǎng)年連作的種植措施會(huì)導(dǎo)致土壤重金屬累積加重,且主要富集在表層土壤。整個(gè)灌區(qū)棉田土壤環(huán)境尚屬于無(wú)污染,但接近輕度污染水平,應(yīng)在以后的種植過(guò)程中做好對(duì)重金屬污染的防控工作。向Cr污染土壤中施入改良劑,會(huì)造成土壤pH有一定程度的升高,Cr的可交換態(tài)含量隨著時(shí)間的變化最終含量有所下降,從而降低了土壤中Cr的生物有效性,達(dá)到了修復(fù)Cr污染土壤的目的。
[Abstract]:In this paper, the distribution characteristics and accumulation of heavy metals in soils under cotton cultivation in Mosuowan Irrigation Area of Manas River Basin in Xinjiang were analyzed by means of regional investigation and field location test. The table of the study area was estimated by geostatistical interpolation method. The spatial distribution of heavy metals in soil layers provides basic data for the protection of soil environmental quality in cotton field of the irrigation area. The Cr element which is heavily polluted in the irrigation area is selected as the improvement object. Through indoor culture experiment, the effects of several chemical amendments on the distribution and transformation of Cr in soil are revealed. The main conclusions are as follows: (1) Cotton field The contents of heavy metals Cr, Ni, Cu, As and Pb in soils (0-100 cm) were 90.65, 32.22, 52.64, 10.90, 13.86 mg/kg, respectively, and those in wasteland soils were 78.21, 32.34, 44.16, 9.48, 13.91 mg/kg, respectively. The contents of Cr, Ni, Cu and As in cotton soils were significantly higher than those in wasteland, and higher than those in Xinjiang soils. The differences of Pb contents between the two soils were not significant, but lower than those in cotton soils. The variation coefficients of heavy metals in cotton soils were higher than those in wasteland soils, which belonged to moderate variation. The results showed that the accumulation of Cr, Cu, As and Ni in cotton field soil was mainly caused by the application of phosphorus fertilizer, but the correlation between heavy metal elements and N, P, K, pH in wasteland soil was not significant, which further explained the continuous cropping of cotton field. (3) The practicability of portable X-ray fluorescence spectrometer was studied and validated. The validation models R2 were 0.9124, 0.8979, 0.7723, 0.8729 mg/kg, respectively. The slope and intercept were optimized, which were close to the ideal model. The calibration results were compared with the traditional laboratory. The results of ICP-AES test showed a very significant positive correlation. The practicability of PXRF heterotopic method and the high accuracy of calibration curve can be fully proved by the validation model of secondary sampling of 36-50 soil samples. (4) Using portable X-ray fluorescence spectrometer to determine the heavy metal content in surface soil of irrigation area, the heavy metal content in soil can be determined quickly. Content variation function and model fitting showed that Cr, As were the best in exponential model, Ni, Pb were the best in Gaussian model, Cu was the best in spherical model, Cr and Cu were 0.86, 0.92 respectively, and the spatial autocorrelation was weak, which was influenced by human random factors. The spatial correlation of Ni, As and Pb were 0.57, 0.41 and 0.46, respectively, with moderate spatial correlation, which was followed by human activities. The results showed that Cr and As were slightly polluted and Ni were slightly polluted. (5) Pot experiment was used to study the remediation effect of different amendments on heavy metal Cr in soil. Exchangeable state content and soil pH value increase to a certain extent. With the increase of pollution concentration, the influence on pH value decreases gradually, but the effect of calcium magnesium phosphate fertilizer is better than CK.4. Exchangeable state content of soil first decreases and then increases, residual state content first increases and then decreases, and finally shows exchangeable state. The effect of the two modifiers was significantly higher than that of the activated carbon and straw, but their effect on the reduction of the exchangeable state content of Cr was shorter. The exchangeable state content of Cr increased after 42 days. The effect of straw application on soil pH and Cr exchangeable state content was not significant, which was related to the amount of improved application and cultivation time. The soil environment of cotton field in the whole irrigation area is not polluted, but it is close to the level of slight pollution. It is necessary to do a good job in the prevention and control of heavy metal pollution in the future planting process. Exchangeable state content decreased with time, which reduced the bioavailability of Cr in soil and achieved the purpose of remediation of Cr contaminated soil.
【學(xué)位授予單位】：石河子大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：X53;X825

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