【作者】 刘艳；

【导师】 彭镇华；

【作者基本信息】 中国林业科学研究院 ， 森林培育， 2009， 博士

【摘要】 城市绿地功能的发挥离不开土壤,城市的居住适宜性、环境质量和人们的生活品质都与城区内土壤所行使的功能密切相关。本研究分析测定了北京市崇文区公园绿地、街旁绿地、居住绿地和行道树绿带土壤的理化性质、重金属污染水平以及微生物数量和活性,揭示了崇文区绿地土壤存在的主要问题,评价了绿地土壤的肥力质量、环境质量和生物质量。研究显示:(1)崇文区绿地土壤理化性质崇文区4类绿地土壤总体上均属于砂质土。崇文区绿地土壤容重变幅为1.12～1.69 g/cm3,平均1.35g/cm3;行道树绿带土壤容重显著高于其它3类绿地,但压实程度尚未达到影响植物生长的水平。崇文区绿地土壤总孔隙度平均为49.14%;公园、街旁和居住绿地土壤总孔隙度均在适宜范围之内(一般适于植物生长发育的总孔隙度为50～56%),只有行道树绿带土壤的孔隙度偏低(40.95%),对植物根系生长可能具有一定影响。崇文区各类绿地土壤紧实度均低于2.5 Mpa;一般情况下,紧实度测量值达到2.5 Mpa时会限制根系生长,因此,对土壤紧实度的测定结果也表明崇文区4类绿地土壤不存在明显的土壤压实问题。崇文区4类绿地土壤pH值介于7.73～8.58之间,所有样点的土壤均为碱性。崇文区绿地土壤有机质、全氮、全磷、全钾含量的均值分别为18.79 g/kg、0.91g/kg、0.96 g/kg和17.07 g/kg。速效氮、速效磷和速效钾的平均含量分别为50.66 mg/kg、29.91 mg/kg和44.16 mg/kg。崇文区绿地土壤碳氮比平均为13.03。依据全国第二次土壤普查土壤肥力标准,崇文区4类绿地土壤有机质含量总体上处于中等水平,部分行道树绿带样点的土壤有机质含量较低;4类绿地土壤全氮含量总体属于中等偏下水平,但各类绿地土壤速效氮含量总体上处于低或很低水平;崇文区绿地土壤总体上非但不缺磷,而且全磷含量普遍较高,速效磷在各绿地土壤中也均不是主要的限制性因子,4类绿地中以居住绿地土壤全磷和有效磷含量为最高; 4类绿地土壤速效钾含量均存在不同程度的缺乏,其中行道树绿带土壤速效钾缺乏问题最为严重。土壤肥力综合指数的计算结果显示,公园绿地土壤养分勉强达到中等水平,街旁绿地、居住绿地和行道树绿带土壤养分总体状况均为低等,主要是由于各绿地土壤速效氮和速效钾含量较低所致。(2)崇文区绿地土壤环境质量崇文区绿地土壤Zn、Cu、Pb、Cr、Ni、As的平均含量分别为63.78 mg/kg、53.72 mg/kg、46.53 mg/kg、25.80 mg/kg、15.76 mg/kg和11.74 mg/kg。参照北京市土壤背景值、中国土壤背景值、国家土壤环境质量一级或二级标准值,崇文区各类型绿地土壤均不存在Cr和Ni污染,但As、Cu、Pb、Zn均有不同程度的超标现象。4类绿地中,行道树绿带土壤的Zn、Pb、Cr含量均最高;而居住绿地土壤Cu含量最高,Pb含量最低,Zn含量也处于最高一级水平;总体上,公园绿地土壤重金属污染相对轻于其它3种绿地类型。(3)崇文区绿地土壤生物质量对全崇文区绿地土壤而言,脲酶活性平均为0.63 mg NH3-N·g-1·24h-1,脱氢酶活性平均92.06 mg TPF·kg-1·h-1,过氧化氢酶活性平均10.48 ml KMnO4·g-120min-1,酸性磷酸酶活性平均29.02 mg C6H5NO3·kg-1·h-1,碱性磷酸酶的平均酶活性为30.28 mg C6H5NO3·kg-1·h-1。不同土壤酶之间以及土壤酶活性与土壤物理性质、养分和重金属含量之间存在着不同程度的相关关系。在测定的5种土壤酶中,过氧化氢酶、脲酶和碱性磷酸酶比较适于作为城市绿地土壤质量的酶学评价指标。崇文区绿地土壤微生物生物量碳、微生物生物量氮的平均含量分别为417.14 mg/kg和62.86 mg/kg;绿地土壤基础呼吸速率平均值为0.480 mg CO2-C·kg-1·h-1;土壤微生物熵平均为4.09 %;代谢熵平均为1.53 mg·g-1·h-1。4类绿地土壤3大微生物类群总数量平均为4.69×106个·g-1,其中细菌所占的比例达到88.87%。在测定的各土壤微生物指标中,只有土壤基础呼吸和土壤微生物量碳氮比与其它指标的相关性较差;除此之外,各微生物指标之间几乎均存在两两间的显著相关关系。崇文区绿地土壤微生物指标与土壤物理指标普遍具有显著的相关性,与部分化学指标和重金属元素也呈显著相关关系。在研究的所有微生物指标中,细菌、真菌和放线菌数量、微生物量碳、微生物量氮最适合作土壤质量评价的微生物指标。(4)比较所有测定指标的方差分析和多重比较结果,无法确定4类绿地土壤总体质量状况间的显著性差异,仅可概括出总体趋势为:公园绿地土壤质量优于街旁和居住绿地,这3类绿地均优于行道树绿带。然而,通过主成分分析(PCA)可计算出崇文区绿地所有土壤样点的综合主成分值,从而可对研究地点的土壤质量进行定量、综合的评价;该方法不仅可以对所有调查样点的土壤质量进行排序,更可清晰的说明公园绿地、街旁绿地、居住绿地和行道树绿带土壤质量从大到小依次降低,且两两间存在显著差异。另外,本文将“数字地球”软件应用于城市绿地土壤采样方案设计中,对于城市土壤研究中的调查取样问题可能会有借鉴作用。目前,有关城市绿地土壤质量的评价体系(如评价方法、指标体系、质量标准)以及与此紧密相关的绿地土壤管理体系尚未建立,本文在综合评价城市绿地土壤方面进行了探索性研究,并对上述相关问题进行了具有作者鲜明观点的探讨。作者认为,绿地土壤质量评价的合适研究尺度应是地块水平,这一尺度不仅与绿化施工、绿地管理实践活动的尺度相符,也避免了在更大的研究尺度上探讨城市土壤质量问题所面临的高度土壤异质性问题。因此,城市绿地土壤研究未来的发展趋势将是面向科学城市土壤管理和健康人居环境的土壤质量监测和评价,研究尺度将缩小到地块水平以与地块尺度的建设或管理活动相统一。更多还原

【Abstract】 The urban green area functions exertive can not be separated from the soil. The urban residential environmental suitability, environment quality and people’s life quality are closely related to urban soil functions. In this study, soil samples from four types of urban green areas in Chongwen District of Beijing, including park green area, settlement green area, roadside green area and street tree greenbelt, were collected. And soil physical and chemical properties, heavy metal pollution level, as well as microorganism quantity and activeness were determined. The main problems of green areas soil of Chongwen District were revealed. Fertility quality, environment quality and biological quality of green areas soil were evaluated. The research demonstrated:(1) Soil physical and chemical properties of urban green areas in Chongwen districtFour types of urban green areas soil in Chongwen District are sandy soils. The amplitude of Chongwen District green areas soil bulk density is 1.12~1.69 g/cm3, and average value is 1.35 g/cm3.The bulk density of street tree greenbelt is significantly higher than the other three types of green areas, but the compaction degree not yet reached the level of impact on plant growth. The average value of Chongwen District green areas soil total porosity is 49.14%; Soil total porosity of park green area, settlement green area, and roadside green area is in suitable scope (generally, suitable scope of soil total porosity for plant growth is 50~56%). Only soil total porosity of street tree greenbelt is low (40.95%), which is possibly has certain influence on growth of plant root. The compaction of Chongwen District green areas soil is lower than 2.5Mpa; In general case, growth of plant root will be limited when the soil compaction reaching 2.5Mpa. Therefore, the result of soil compaction shows that there is no obvious soil compaction problem.The amplitude of Chongwen District green areas soil pH is 7.73~8.58. Almost all the soil samples are alkaline. The average value of organic matter, total nitrogen, total phosphorus, and total potassium content is 18.79 g/kg, 0.91 g/kg, 0.96 g/kg and 17.07 g/kg, respectively. The average content of available nitrogen, available phosphorus and available potassium is 50.66 mg/kg, 29.91mg/kg and 44.16mg/kg, respectively. The soil C/N of Chongwen District green areas is 13.03. According to soil fertility standard of the second national soil survey, the soil organic matter content of Chongwen District green areas is in the medium level. Some of street tree greenbelt soil samples’organic matter content is low. The soil total nitrogen content of Chongwen District green areas is in lower-middle level. But the soil available nitrogen content is in low or very low level. The Chongwen District green areas soil does not lack the phosphorus grossly, moreover the total phosphorus content is generally high, and available phosphorus is not the main limited factor in Chongwen District green areas soil. Among the four types green areas soil, settlement green area soil total phosphorus and available phosphorus content is highest. About one-third street tree greenbelt soil samples lack total potassium. The other three types green areas soil do not have the problem. But available potassium has the varying degree lacking in four type of green areas soil. The street tree greenbelt soil available potassium is the most serious lacking.The result of soil fertility comprehensive index shows that the park green area soil nutrient reaches the medium level. The settlement green area, roadside green area and street tree greenbelt soil nutrient is in low level. It is maybe because that available nitrogen and available potassium are low.(2) Soil envioronmental quality of urban green areas in Chongwen districtThe average concentration of Zn, Cu, Pb, Cr, Ni and As in the green areas of Chongwen District is 63.78, 53.72, 46.53, 25.80, 15.76 and 11.74 mg/kg, respectively. According to BVB, BVC, NSEQS-Ⅰo r NSEQS-Ⅱ, the green area soil of Chongwen District is unpolluted by As and Ni, but As, Cu, Pb, Zn is over standard in different degree.Among the four types of green areas, the average concentrations of Zn, Pb and Cr in the soils of the street tree greenbelts are the highest. Cu concentrations in the soils of the settlement green area are the highest, and its Pb concentrations are the lowest. In general, the concentrations of heavy metals in the soils of park green area are lower than those of the other types of green areas.(3) Soil biological quality of urban green areas in Chongwen districtThe average enzyme activity of urease (UA), dehydrogenase (DHA), catalase (CA), acid phosphatase (acid-Pa) and alkaline phosphatase (alk-Pa) in the green areas of Chongwen District is 0.63 mg NH3-N·g-1·24h-1, 92.06 mg TPF·kg-1·h-1, 10.48 ml KMnO4·g-120min-1, 29.02 mg C6H5NO3·kg-1·h-1, and 30.28 mg C6H5NO3·kg-1·h-1, respectively. There are varying degrees of relevance among different soil enzymes as well as soil enzyme activities with soil physico-chemical properties. On the whole, soil enzyme activities in park green areas are the highest, soil enzyme activities in street tree greenbelts are the lowest. No significant differences are found in soil enzyme activities between settlement and roadside green areas. Among the five kinds of soil enzymes, catalase, urease and alkalinity phosphatase are suitable for soil quality enzymatic assessment in urban green areas.The average concentration of soil microbial biomass carbon and soil microbial biomass nitrogen of green areas in Chongwen District is 417.14 mg/kg and 62.86 mg/kg, respectively. The soil basal respiration rate is 0.480 mg CO2-C·kg-1·h-1 in average. The average values of soil microbial quotient and metabolic quotient is 4.09 % and 1.53 mg·g-1·h-1. The total number of microbes (bacteria, fungi and actinomycete) is 4.69×106 CFU·g-1, among which, the proportion of bacteria reached 88.87%. A poor correlation between BR (soil basal respiration), Cmic: Nmic (soil microbial biomass carbon nitrogen ratio) and other soil microbial indicators are demonstrated in this study. In addition, almost anyone microbial indicator is significantly related with another microbial indicator. Soil microbial indicators are significantly with most physical indicator and are significantly correlated with a portion of chemical parameters and heavy metal elements. In all microbial indicators, the number of soil micrbes, Cmic (soil microbial biomass carbon) and Nmic (soil microbial biomass nitrogen) are best suitable for evaluating soil quality.(4) The results of variance analysis and multiple comparisons of all parameters are compared, but significant difference of overall quality condition among four kind of green area soil does been determined, only a general trend can be summed up as follows: the soil quality of park green area is superior to roadside and settlement green area and they all are better than the street tree green area. However, we can get the comprehensive principal component values of all sampling points through the principal component analyzes (PCA), thus having a quantitatively and comprehensively soil quality evaluation to all sampling points. This method not only may carry on sorting to soil quality of all investigation sampling point, but also clearly explain that the quality decrease in order of park green area>roadside green area>settlement green area>street tree greenbelt. And there is significant difference between every two types. In addition, this article applied“digital globe”the software to the urban green area soil sampling program, may be used for reference to the study of urban soil sampling survey.At present, soil quality evaluation system (such as the evaluation principles, methods, indicators, quality standards) of the urban green areas as well as the green areas management system which is closely related with this not yet been established, this article has also conducted the exploring research on the synthetic evaluation of urban green areas soil quality, and above-mentioned related issues were discussed with a clear viewpoint of the author. The author believed that the suitable scale of green area soil quality assessment study should be block-scale level, this research criterion not only matched with afforested construction, green areas management practice criterion, also avoided high degree of heterogeneity problem of urban soil in larger-scale studies on urban soil quality. Therefore, development trend of urban green areas soil research are soil quality monitoring and evaluation which facing urban soil management and healthy living environment. And research-scale will be reduced to the plots level which matching with the building or land management activities.更多还原