| 摘要: |
| 【目的】探明色季拉山森林土壤重金属含量空间分布特征及其污染状况。【方法】在色季拉山阴坡和阳坡分别选取了3 700，3 900，4 300 m 3个海拔梯度,设置了6个采样点，分层（0～10，10～20，20～40，40～60和60～100 cm）采集土样，测定Cr、Cd、Hg、Ni、Se、As、Pb 7种土壤重金属元素含量，并参照全国土壤元素背景值，采用单因子指数法、内梅罗指数法和污染负荷指数法对土壤重金属污染状况进行综合评价。【结果】（1）色季拉山森林0～20 cm土层重金属元素Cr、Se、As、Pb含量低于全国土壤元素背景值和西藏土壤元素背景值；Cd和Hg含量都超过了全国土壤元素背景值和西藏土壤元素背景值，分别是全国土壤元素背景值的2.2倍和2.92倍、西藏土壤元素背景值的2.75倍和9.5倍；Ni含量低于西藏土壤元素背景值，但高于全国土壤元素背景值，是其含量的1.03倍。7种重金属元素含量的变异系数都大于50%，其中Hg表现为极度变异，其余6种均属于高度变异。（2）在同一土层Cr、As含量均表现为阳坡低于阴坡，Pb、Ni和Hg含量总体均表现为阳坡大于阴坡。在阳坡，As、Cd、Hg含量随着海拔升高而降低，Se含量随着海拔的升高而增加；而在阴坡，Cr、Se和As含量随着海拔的升高而降低，Pb和Hg含量随着海拔的升高而增加；重金属元素As含量在阴坡随土层的加深而增加，Hg含量在阳坡随土层的加深而减少。其余重金属元素含量在不同坡向、海拔及土层间无明显规律性。（3）单因子指数评价结果表明，在色季拉山森林土壤0～20 cm土层，在阳坡，Hg为重度污染，Cd为中度污染，Ni为轻度污染，Cr、Se、As、Pb都是非污染状态；在阴坡，Cd和Hg为中度污染，其他5种重金属元素都是非污染状态。（4）内梅罗指数法评价结果表明，在色季拉山森林0～20 cm土层，阳坡土壤受重金属污染程度明显高于阴坡，主要污染物均为Ni、Cd和Hg。（5）通过污染负荷指数法对色季拉山林0～20 cm土层重金属污染状况进行评价发现，阳坡森林土壤受到轻度的重金属污染，阴坡土壤无重金属污染。【结论】在色季拉山森林0～20 cm土层中，Ni、Cd和Hg 3种重金属元素都达到了污染程度，其中Ni是轻度污染，Cd和Hg是中度以上污染；阳坡土壤受到轻度的重金属污染，阴坡无重金属污染。 |
| 关键词: 森林土壤；重金属污染；空间分布；污染评价 色季拉山 |
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| 基金项目:西藏林芝高山森林生态系统国家野外科学观测研究项目（2015-2020）；西藏生态安全实验室项目（STX2018-03） |
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| Spatial distribution characteristics and pollution assessment of heavy metals in forest soils of the Sygera Mountain |
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FAN Zhiying,LI Jiangrong,GAO Tan,et al
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| Abstract: |
| 【Objective】This study aimed to find out the spatial distribution characteristics of heavy metals in forest soil of the Sygera Mountain.【Method】A total of 6 stratified sampling points (0-10,10-20,20-40,40-60,and 60-100 cm) were set at 3 700,3 900,and 4 300 m on the shady and sunny slopes of Sygera Mountain.The contents of heavy metals including Cr,Cd,Hg,Ni,Se,As and Pb in seven types of soils were determined.With reference to the background values of national soil elements,the single factor index method,Nemero index method and pollution load index method were used for comprehensive evaluation of soil heavy metal pollution.【Result】(1) In the 0-20 cm forest soil layer of the Sygera Mountain,the contents of heavy metals including Cr,Se,As and Pb were lower than the national and Tibetan background values.Cd and Hg contents exceeded the national and Tibetan background values.They were 2.2 and 2.92 times of the national background values and 2.75 and 9.5 times of the Tibetan background values.Ni content was lower than the Tibetan background value,but was 1.03 times of the national background value.The coefficients of variation of the seven heavy metal elements were greater than 50%.Hg showed extreme variation,and the other six were highly variable.(2) The contents of Cr and As in the same soil layer in the sunny slope were lower than in the shady slope,while Pb,Ni and Hg contents were opposite.On the sunny slope,contents of As,Cd and Hg decreased with the elevation,while Se content increased.On the shady slope, contents of Cr,Se and As decreased with the increase of altitude,while contents of Pb and Hg increased.The content of As increased with the increase of soil layer depth on the shady slope,and Hg content decreased with the increase of soil layer depth on the sunny slope.The contents of other heavy metal elements had no obvious regularity in different slope aspelt,altitude and soil layer.(3) The single factor index evaluation results showed that in the soil layer of 0-20 cm,Hg was heavily polluted,Cd was moderately polluted,Ni was mildly polluted,and Cr,Se,As and Pb were in non polluting state on the sunny slope.On the shady slope,Cd and Hg were moderately polluted, and the other elements were in non polluting state.(4) The evaluation results of Nemero index method showed that the sunny slope was more polluted than the shady slope in the soil layer of 0-20 cm.The main pollutants were Ni,Cd and Hg.(5) The pollution load index method showed that the soil in the sunny slope was mildly polluted by heavy metals, while the soil was not polluted in the shady slope.【Conclusion】In the 0-20 cm forest soil layer of the Sygera Mountain,Ni,Cd and Hg all reached the pollution levels. Ni was in mild pollution,while Cd and Hg were in moderate pollution.The sunny slope soil was slightly polluted by heavy metals and the shady slope soil was not polluted. |
| Key words: forest soil heavy metals pollution spatial distribution pollution assessment Sygera Mountain |
