本文選題：土壤重金屬 + 神經(jīng)網(wǎng)絡(luò)　； 參考：《昆明理工大學(xué)》2017年碩士論文

【摘要】：土壤重金屬污染可威脅到人類的健康,城鄉(xiāng)結(jié)合處生態(tài)環(huán)境復(fù)雜,農(nóng)田分散且容易受到污染,本文主要是對(duì)上海市奉賢區(qū)某農(nóng)田中的土壤重金屬污染風(fēng)險(xiǎn)研究。采集41份樣品,經(jīng)初步處理后,檢測(cè)重金屬鉻(Cr)、砷(As)、鎳(Ni)、鉛(Pb)、鋅(Zn)、鈷(Co)和銻(Sb)7種元素的含量,然后利用RBF神經(jīng)網(wǎng)絡(luò)與BP神經(jīng)網(wǎng)絡(luò)兩種模型預(yù)測(cè)出研究區(qū)域未檢測(cè)的11組預(yù)采樣位點(diǎn)的7種重金屬的含量。取出前35組數(shù)據(jù)作為訓(xùn)練數(shù)據(jù),后6組數(shù)據(jù)作為驗(yàn)證,結(jié)果顯示,RBF神經(jīng)網(wǎng)絡(luò)預(yù)測(cè)優(yōu)于BP神經(jīng)網(wǎng)絡(luò)預(yù)測(cè)模型。多元統(tǒng)計(jì)結(jié)果顯示52組數(shù)據(jù)中除Co、Sb沒(méi)有國(guó)家標(biāo)準(zhǔn)的參考值之外,Cr、As、Ni、Pb、Zn的平均值均未超過(guò)國(guó)家二級(jí)標(biāo)準(zhǔn)值,但As、Ni的最大值則超過(guò)了環(huán)境土壤質(zhì)量標(biāo)準(zhǔn)中國(guó)家二級(jí)標(biāo)準(zhǔn);As、Ni、Zn、Co和Sb5種元素的均值超過(guò)了上海市土壤環(huán)境背景值,Sb、As、Co 3種元素在土壤中存在明顯富集。As和Sb達(dá)到高度變異,Pb、Zn、Ni、Co達(dá)到中度變異。在地統(tǒng)計(jì)分析中,研究區(qū)域土壤重金屬元素Cr、As、Ni、Pb、Zn、Co和Sb的含量采用普通克里格插值法。結(jié)果顯示:總體上看,在土壤重金屬的空間分布中,研究區(qū)域的西南部多為元素的高值區(qū),而中東部地區(qū)土壤重金屬積累不明顯。相關(guān)性分析中,重金屬元素Cr-Ni、Cr-Co和Co-Ni兩兩之間已經(jīng)達(dá)到高度相關(guān)。主成份分析中前3個(gè)因子的累積方差貢獻(xiàn)率為89.044%。第1因子中,旋轉(zhuǎn)元素Ni的載荷最高,旋轉(zhuǎn)后元素Cr的載荷最高,第2因子中旋轉(zhuǎn)前元素As的載荷最高旋轉(zhuǎn)后元素Pb的載荷最高,在第三因子中,旋轉(zhuǎn)前元素Pb的載荷最高,旋轉(zhuǎn)后元素As的載荷最高。地累積指數(shù)法發(fā)現(xiàn)研究區(qū)域采集及預(yù)測(cè)樣品中,Cr、Pb未受到污染,Sb整體上處于于無(wú)污染-中度污染,研究區(qū)域試驗(yàn)樣品中污染較為嚴(yán)重。污染負(fù)荷指數(shù)法研究發(fā)現(xiàn),研究區(qū)域整體上處于中等污染。潛在生態(tài)危害指數(shù)法研究發(fā)現(xiàn)Sb的平均值達(dá)到43.61,整體上已處于中度風(fēng)險(xiǎn)水平,As元素的最大值是50.29,達(dá)到了中度風(fēng)險(xiǎn)水平,其余元素的最大值均為超過(guò)40,處在輕度風(fēng)險(xiǎn)水平。研究區(qū)綜合潛在生態(tài)風(fēng)險(xiǎn)指數(shù)RI的平均值為80.29,小于150,說(shuō)明研究區(qū)整體上處于輕度生態(tài)風(fēng)險(xiǎn)水平。
[Abstract]:Heavy metal pollution in soil can threaten human health. The ecological environment in the combination of urban and rural areas is complex and farmland is scattered and vulnerable to pollution. This paper mainly studies the risk of heavy metal pollution in a farmland in Fengxian District of Shanghai. 41 samples were collected. After preliminary treatment, the contents of 7 kinds of elements, such as Cr, Cr, as, Ni, Pb, Zn, Co) and SB ~ (3 +), were determined. Then, RBF neural network and BP neural network were used to predict the contents of 7 heavy metals in 11 groups of presampled sites in the study area. The first 35 groups of data are taken as training data and the last 6 groups of data are used as verification data. The results show that RBF neural network prediction is better than BP neural network prediction model. The results of multivariate statistics show that the average value of Cr ~ (2 +) -As-Ni ~ (2 +) Pb ~ (2 +) in 52 groups of data does not exceed the national second class standard value except that there is no reference value of the national standard for CoSb. However, the maximum value of As-Ni is higher than that of the national secondary standard, As-NiNiZn-Co and Sb5, in the environmental soil quality standard, which is higher than the soil environmental background value of Shanghai, where there are significant enrichment of. As and SB in the soil. The variation was moderate. In the geostatistical analysis, the contents of heavy metal elements in the soil of the region were studied by the ordinary Kriging interpolation method. The results showed that, in the spatial distribution of soil heavy metals, the southwest of the study area was mostly the high value area of elements, but the accumulation of heavy metals in the middle and eastern regions was not obvious. In the correlation analysis, there is a high correlation between the heavy metal elements Cr-NiCr-Co and Co-Ni. The cumulative variance contribution rate of the first three factors in principal component analysis was 89.04444. In the first factor, the load of rotating element Ni is the highest, the load of rotating element Cr is the highest, the load of element as before rotation is the highest in factor 2, the load of element Pb after rotation is the highest, and the load of element Pb before rotation is the highest in the third factor. The load of as is the highest after rotation. It was found by the method of geoaccumulation index that the samples collected and predicted in the study area were not polluted and the SB was generally in the range of no pollution and moderate pollution, and the pollution in the samples of the study area was more serious. The study of pollution load index method found that the study area is in the middle pollution as a whole. The study of potential ecological hazard index showed that the average value of SB reached 43.61, and the maximum value of element as was 50.29, which reached the level of moderate risk, and the maximum value of other elements was over 40, which was at the level of mild risk. The average value of the comprehensive potential ecological risk index RI is 80.29, which is less than 150, which indicates that the study area is at the level of light ecological risk as a whole.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：X53

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本文編號(hào)：1833014