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1、青藏铁路沿线土壤重金属的分布规律初探鲁春霞1，谢高地1，李双成2，李利锋1，陈辉11. 中国科学院地理科学与资源研究所，北京 100101；2. 北京大学城市与环境学院，北京 100871摘要：通过对青藏铁路沿线已经运营路段和正在修建路段两侧采集的土壤样品进行重金属含量测定分析，研究修建青藏铁路对铁路沿线土壤生态环境的影响。分析的重金属元素包括Hg和Pb。其中Hg采用氢化发生等离子发射光谱法，Pb采用等离子发射光谱法进行测定。测定结果表明，已运营铁路沿线重金属铅和汞具有显著的规律性变化。在铁路一侧，铅和汞含量随距离变化呈现正态分布，其最高峰值出现在距铁路50 m左右。而且，铅和汞含量高于土壤背
2、景值以及正在修建铁路两侧的土壤含量。通过对土壤理化性质的分析表明，已运营铁路段土壤的理化性质与铅和汞含量变化没有显著的相关性，因此，可以推断，铁路运输已经造成了铁路两侧土壤一定程度的重金属污染。关键词：重金属污染；土壤环境；青藏铁路中图分类号：X144 文献标识码：A 文章编号：1672-2175（2004）04-0546-03随着我国交通运输业的快速发展，重金属的环境污染问题已经引起人们的高度重视。公路重金属污染的主要来源是目前已经得到公认的汽油、柴油燃烧后的废气扩散，同时车辆轮胎成分中亦含有多种重金属元素，因此，轮胎磨损也是重金属元素的重要物质来源。这些重金属在自然环境中沉降，从而对人类、
3、家畜、农业生态及自然环境产生严重的潜在影响和危害。对铁路沿线的环境污染通常以水污染物中的COD和石油类为主要研究对象。尽管铅、铬等重金属元素也是铁路沿线环境监测的重要内容1，但是到目前为止，对铁路两侧重金属污染关注较少。图1 都兰寺车站铁路南侧土壤中铅含量随距离的变化青藏高原作为全球的第三极，不仅孕育着我国的主要河流，影响着我国以及东亚的气候变化，而且，它脆弱而敏感的环境决定了它对小的干扰会产生显著放大的影响作用。因此，对于这样一个独特而典型的区域，任何开发建设活动都可能产生难以预料的潜在影响。青藏铁路二期工程格尔木至拉萨段正在修建。修建青藏铁路是否会对沿线的土壤生态环境产生重金属污染？为此，
4、我们沿高原已经运营多年的铁路段和正在修建的铁路段，采集土壤样品进行土壤重金属分布规律分析。由于铁路与公路均为线状工程，根据前人的研究可知，公路两侧土壤中铅含量呈现指数衰减分布规律2。也有人总结国内外研究成果后认为，沿公路两侧土壤中铅的影响范围主要集中在50 m左右，且铅含量与离公路边沿的距离呈高斯衰减分布3。因此，本研究采样布点均分布距铁路50 m的范围内。1 采样点概况及样品处理由于已建青藏铁路大致和青藏公路相伴而行，采样点选择尽量远离公路。采样时结合地特点在铁路一侧或两侧50 m内采样。采样点沿铁路两侧等间距分布。不同采样点的自然环境概况如表1所示。表1 样点周围的自然概况采样点铁路修建情
5、况主要植被地带性土壤类型周围状况都兰寺车站(3659N, 9840E)已运营芨芨草、白刺山地栗钙土周围无大污染源南山口(3707N, 9529E)已运营植被稀少灰棕荒漠土周围无污染源昆仑山(3544N, 9404E)正在修建嵩草、红景天等高寒草甸土周围无污染源风火山(3441N, 9250E)正在修建针茅、羊茅高寒草甸土周围无污染源那曲(3119N, 9152E)正在修建紫花针茅、火绒草、景天高寒草甸土周围无污染源同一个采样点土样取三个重复，经混合后，进行碾碎、研磨、过筛等处理。Hg采用氢化发生等离子发射光谱法进行测定；Pb采用等离子发射光谱法进行测定。2 重金属分布规律及含量变化2.1 铅的
6、分布及其含量变化位于青海省都兰县都兰火车站（3659N，9840E）附近铁路南侧土壤的含铅量如图1所示，除25 m处的最小值23.57 mg/kg外，铅含量与离铁路边沿的距离基本呈正态分布。心土层最大含铅量68.67 mg/kg在距铁路45 m处，而表土层的最大铅量则在距铁路65 m处，说明土壤中的铅含量高峰在距铁路的50 m左右，对南山口铁路一侧样品的分析也表明同样的规律。这与公路两侧铅含量的分布规律有一定差异3，公路两侧土壤的铅含量随着距离公路愈远而减少3，即铅含量的高峰值在公路边最高，而铁路两侧的高峰则出现在距铁路50 m左右处。这可能是由于铁路一般都修建有高大的路基，在路基两侧形成了较
7、高的坡面地形，这种坡面地形在降雨的作用下，会把土壤中的重金属淋滤到低洼的地方，从而改变了土壤中重金属的原始分布状态。与青海省土壤中的铅背景值(20.95.95) mg/kg4相比，除了距铁轨25 m处心土的含铅量小于最大背景值之外，其余各点的含铅量均高于最高土壤背景值。表2 铁路沿线样点的土壤铅含量变化 mg/kg距铁路5 m处距铁路25 m处距铁路45 m处都兰寺(表土)30.7544.0747.15已运营南山口35.9137.0341.14已运营昆仑山29.1426.9324.69正在修建风火山25.6232.7923.92正在修建那曲15.7130.2926.93正在修建根据国家GB 1
8、56181995的土壤环境质量标准，一级土壤环境质量的铅自然背景值小于35 mg/kg。而表1中所显示的5个土壤样品中3个样品的铅平均含量值高于35 mg/kg。都兰寺火车站周围完全是荒漠草原景观，很少有其他人类活动的干扰，而且，采样点与公路之间有山体阻挡，公路两侧的铅污染应该不会对铁路两侧的土壤产生影响。对铁路沿线已经运营和正在修建的几个样点土壤铅含量的测定结果见表2。在已经运营的铁路段，土壤中的重金属含量分布具有一定的规律，而正在修建的铁路两侧其土壤中的重金属含量分布没有明显的规律性变化。由此可以推断，铁路运营使铁路两侧产生了一定程度的重金属铅污染。2.2 土壤中的汞含量变化对都兰寺车站采
9、集的样品进行汞含量的分析表明（图2），其变化规律与铅的分布变化基本相似，所不同的是表层土壤和心土中的汞含量最高值同时出现在距铁路45 m处，这与铅含量的高峰值表现有一定差异。而且，已运营铁路段的土壤汞含量均高于西藏和全国的土壤汞含量的平均水平5。表3 都兰寺站铁路南侧土壤铅、汞、pH、CaCO3和有机质变化趋势w(CaCO3)/%w(有机质)/%pHw(Pb)/(mgkg-1)Lb: w(Hg)/(mgkg-1)10.401.368.02370.234011.742.338.00300.403712.621.158.34560.419012.623.178.25460.330310.841.9
10、48.16320.2218根据对土壤中铅汞含量与pH、有机质和碳酸钙含量的相关分析表明（表3），它们之间没有显著的相关关系，说明铅汞含量的变化不是土壤本身的理化性质变化而引起的，由此推测，土壤的基本理化性质对土壤铅和汞的含量的影响不明显。对沿线正在修建铁路段样点土壤汞的分析表明，那曲样点土壤汞含量基本上与西藏同类土壤的背景值一致，而昆仑山和风火山的汞含量相对较高，但普遍低于已运营铁路段样点的土壤汞含量值。这可能说明土壤中铅和汞含量变化的主要原因应该是铁路运行带来的污染。3 结论与讨论在青藏铁路沿线已运营段和正在修建段采集土壤样品进行重金属含量分析的结果表明，已运营铁路段的土壤铅和汞含量显著高于
11、土壤背景值，而且普遍高于正在修建铁路段的含量值。土壤铅和汞含量随距离呈现正态分布，这种分布与公路两侧土壤铅分布规律不同。可能是由于铁路路基形成的高大坡面，容易产生坡面流，使土壤中的重金属向低洼区域富集，因此，高峰值出现在距铁路50 m左右。对样品土壤理化性质与重金属含量进行的相关分析也表明，在铁路两侧，土壤理化性质对土壤铅和汞含量的影响程度不大。而且，正在修建的青藏铁路段，没有显著的随距离变化的分布规律。由此推断，铁路运输造成了两侧土壤一定程度的污染。图2 都兰寺站铁路南侧土壤中汞含量随距离的变化铁路运输带来的环境污染一般以油类污染最为突出。青藏铁路沿线土壤中的重金属含量汞和铅高于背景值似乎不
12、合常理。实际上，根据研究，油污染可以产生大量的重金属污染6，所以，铁路沿线的重金属污染很可能是油污染造成的。其次，铁路两侧的环境污染与运输的货物有很大关系。另外，尽管在铁路沿线采样时尽可能远离公路，但由于青藏铁路和公路基本上总是相伴而行，公路运输产生的废气扩散，也或多或少会产生影响，但可以肯定还是以铁路运输产生的污染为主。由于资料数据所限，对于青藏铁路沿线土壤重金属污染的原因还有待于进一步深入研究。参考文献：1 蔡惟瑾, 潘智, 宋珺. 铁路环境监测实验室质量控制水样考核评价J. 铁道劳动安全卫生与环保, 1997, 24（2）: 132-134. 2 汪新生, 赵建奇, 弋鼎哲. 公路两侧土
13、壤铅污染预测研究J. 西北大学学报(自然科学版), 1993, 23(5): 472-477. 3 王斌, 丁桑岚. 公路两侧土壤中铅的分布规律研究J. 重庆环境科学, 1998, 20(4): 53-55. 4 索有瑞, 黄雅丽. 西宁地区公路两侧土壤和植物中铅含量及其评价J. 环境科学, 1996, 17(2): 74-76. 5 张晓平, 朱延明. 西藏土壤中的汞含量及其地理分布J. 环境科学, 1994, 15(4): 27-30. 6 邵涛, 刘真, 黄开明, 等. 油污染土壤重金属赋存形态和生物有效性研究J. 中国环境科学, 2000, 20(1): 57-59.Heavy met
14、al distribution along the Tibet railroadLU Chun-xia1, XIE Gao-di1, LI Shuang-cheng2, LI Li-feng1, CHEN Hui11. Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; 2. Department of Urban and Environmental Sciences, Peking University, B
15、eijing 100871, ChinaAbstract: It is well known that the ecological environment in the Tibet Plateau is fragile and it can be disturbed readily by humans activities. In order to study the impact of railroad construction on soil environment in Tibet Plateau, heavy metal content and its distribution al
16、ong the Tibet railroad was investigated. The metal elements including Hg and Pb were determined by the plasma radiation spectrum. The results showed that there was an obvious normal distribution of Pb and Hg and the maximum appeared in the 50 m beside the railroad. The content of Pb and Hg were high
17、er than that of soil background value. The Pb and Hg distribution along the being constructed railroad reach had not the similar situation. The related analysis suggested that the physical and chemical properties didnt make a remarkable influence on the Pb and Hg distribution, it is thus concluded t
18、hat the railroad transportation is likely to cause heavy metal pollution in soil to a certain extent. Key word: heavy metal pollution; soil environment; Tibet railroad（上接第545页）参考文献：1 黄铭洪. 环境污染与生态恢复M. 北京: 科学出版社: 2003.2 熊毅, 陈家坊. 土壤胶体(第3册): 土壤胶体的性质M. 北京: 科学出版社: 1990.3 彭刚华. 水稻土中重金属Cd的形态含量变化J. 福建环境, 2002
19、, 19(1): 34-35.4 于天仁, 季国亮, 丁昌璞. 可变电荷土壤的电化学M. 北京: 科学出版社, 1996: 12-15.5 华路, 陈世宝. 有机质在土壤重金属污染治理中的作用J. 农业环境与发展, 1999(3): 26-29.6 倪才英, 刘永厚, 姚益云, 等. 不同质地土壤对铜的吸附性能试验J. 江西农业大学学报, 1996, 18(4): 426-430.7 龙新宪, 倪吾钟, 杨肖娥. 菜园土壤铜吸附: 解吸特性的研究J. 农村生态环境, 2000, 16(3): 39-41.8 丁颖, 周启星, 王新, 等. 黑土和棕壤对铜的吸附研究J. 应用生态学报, 2003
20、, 14(5): 761-765.9 SUMNER M E. Handbook of soil scienceM. Boca Raton: CRC press, 2000.Effects of physiochemical and surface characteristics of soils on copper adsorptionHU Hong-qing, CHEN Song, LI Yan, DING Shu-wen, ZHAO Zhu-qingCollege of Resource and Environment, Huazhong Agricultural University,
21、Wuhan 430070, ChinaAbstracts: The eleven soils collected from Daye city were used to investigate the relationship of the physiochemical properties and Cu2+ adsorption. Results indicated that copper adsorption amount decreased with the order of calcareous soil paddy soil chao soil brown red soil. The
22、 adsorption amount of Cu2+ was corresponding to the cation change capacity (CEC) of soils. At 5 mmolL-1 addition concentration, the amount of Cu2+ adsorption (x) of soils and CEC were observed a positive straight line correlation as following equation: x = 2.018CEC + 24.4 (r =0.7066)。Other physioche
23、mical characteristics which affect CEC, such as pH, clay content and composition, organic matter, specific surface area, were factors controlling Cu2+ adsorption.Key words: cation change capacity; copper adsorption; soils; Daye cityEditors note: Judson Jones is a meteorologist, journalist and photog
24、rapher. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the worlds firs
25、t satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken.
26、 Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a space capsu
27、le hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet T
28、uesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line we would be go for launch.I feel this mission was created for me
29、because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop m
30、e from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almos
31、t grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The sup
32、ersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the l
33、ower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he cros
34、ses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto somethin
35、g resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the sh
36、allow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him co
37、mpletely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to dep
38、loy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass
39、out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
