Field Description and Identification of Diagnostic Qualifiers for Urban Soils in Brazil

ABSTRACT Human activities often alter soils found in urban areas. These alterations affect their environmental functions and potential for use. However, soils from urban areas in Brazil have not been surveyed and identified, which can pose a technical problem for the development of the city. Considering the importance of urban environments and their soils, this study aimed to evaluate the environmental and morphological characteristics and the physical properties of urban soils in Santa Maria, Rio Grande do Sul, Brazil. The purpose was then to organize a protocol for describing urban soils and to identify diagnostic qualifiers to subsidize establishment of an order that allows proper classification of these soils in the Brazilian Soil Classification System. The protocol containing general and environmental notes and morphological notes and qualifiers was organized based on the experience of this study and the relevant literature. The environmental, morphological, and physical analyses carried out supported interpretation of the urban soils of Santa Maria, their classification in the World Reference Base for Soil Resources system, and identification of diagnostic qualifiers proposed for the Brazilian Soil Classification System. The protocol tested in this study was adequate for data collection in the field. Soils had high variation in layer thickness, particle size composition, color, bulk density, saturated hydraulic conductivity, penetration resistance, stoniness, and the presence of artifacts. Considering the establishment of a Brazilian taxonomy for urban soils, the field data led to the proposal for new qualifiers, such as Saprolitic (residual saprolite material), Impervic (sealed/impermeable layer), Multigranic (layers with contrasting textures), Stonic (layers with stoniness), and Saprorockic (layers constituted of transported saprolite), which can be used as diagnostic attributes in the Brazilian Soil Classification System and even contribute to improvement of the order of Technosols in the World Reference Base For Soil Resources system.摘要 人类活动常会改变城市区域内的土壤，此类改变会影响土壤的环境功能与利用潜力。然而，巴西境内城市区域的土壤尚未得到系统调查与鉴定，这会为城市发展带来技术层面的难题。鉴于城市环境及其土壤的重要性，本研究旨在评估巴西南里奥格兰德州圣玛丽亚市城市土壤的环境与形态特征，以及其物理性质。本研究的另一目标是构建一套城市土壤描述规程，并确定诊断限定特征（diagnostic qualifiers），以辅助制定相关规范，从而实现基于《巴西土壤分类系统（Brazilian Soil Classification System）》对这类土壤进行合理分类。本研究结合自身试验经验与相关文献，编制了包含基础信息、环境记录、形态描述及限定特征的野外调查规程。通过开展环境、形态与物理分析，为圣玛丽亚市城市土壤的解译、《世界土壤资源参比基础（World Reference Base for Soil Resources）》系统中的分类，以及针对《巴西土壤分类系统》提出的诊断限定特征的鉴定提供了支撑。本研究验证的规程适用于野外数据采集工作。研究区域内的土壤在土层厚度、粒度组成、颜色、容重（bulk density）、饱和导水率（saturated hydraulic conductivity）、贯入阻力（penetration resistance）、砾石含量（stoniness）以及人工侵入体（artifacts）的存在情况等方面均存在显著变异。考虑到构建巴西城市土壤分类体系的需求，本次野外调研数据催生了一批新型诊断限定特征的提案，包括腐岩质（Saprolitic，指残余腐岩物质）、不透水层质（Impervic，指封闭/不透水层）、多粒级质（Multigranic，指具有相反质地的土层）、多石质（Stonic，指富含砾石的土层）以及搬运腐岩质（Saprorockic，指由搬运腐岩构成的土层），这些特征可作为《巴西土壤分类系统》中的诊断属性，甚至有助于完善《世界土壤资源参比基础》系统中人为土（Technosols）的分类层级。