流域土地利用与景观格局变化对土壤重金属的影响-以洋河流域为例

Effect of landuse and landscape changes on heavy metals in soils at a watershed scale is a key research project for a new emerging interdiscipline, Landscape Ecotoxicology. Based on "3S"， namely remote sensing (RS), geography information systems (GIS) and global positioning systems (GPS), the evolution of landuse and landscape pattern in a case study area, the Yanghe watershed in the past 30 years will be analyzed. A technique of spatial sampling in landscape ecology will be employed for soil sampling at the watershed scale. Total concentrations of heavy metals in all soils will be measured, and their spatial variations and distributions will be modelled and displayed, respectively. Total concentrations of heavy metals, their contamination and enrichment in the soils from different long-term landuse types, landuse transformations and landuse intensities at the watershed scale will be determined. According to these results, some land plots representing different landuse and landscape changes will be selected. Different chemical extraction methods (including soil pore water extraction, EDTA extraction, 0.1M Ca(NO3)2 extraction and in vitro method) will be applied to extract the heavy metals in the soils collected from the plots in order to characterize their potential risks to water, plant, animal and human health. Combined with soil physicochemical properties, the influencing mechanisms of landuse and landscape changes upon heavy metal contamination and potential risks at the representative plots will be demonstrated. Then, based on what have been found from the representative plots, multiple regression modelling, geostatistics and GIS will be used to explore the impact of landuse and landscape changes on heavy metal contamination and risks from the soils at the watershed scale. Additionally, the landscape pattern indicators will be related to heavy metal concentrations in the soils at the watershed scale and the impact of landscape pattern variations at horizontal and vertical levels upon heavy metal comtamination and potential risks will be ascertained by an integration of landscape ecolgoy, "3S" and soil ecotoxicology. The purpose of this study is to understand the relationships between landuse and landscape changes caused by human activities and spatial distributions of soil heavy metals as well as their potential risks to water, plant, animal and human health at a watershed scale. The research results could be helpful for a reasonable land allocation, source identification as well as modelling and early warning of soil heavy metal comtamintation and potential risks at a watershed scale. We expect that this study could promote watershed eco-envrionmetal protection and regional sustainability as well as the development of Landscape Ecotoxicology in China in the future.

流域土地利用与景观格局变化对土壤重金属的影响是新兴边缘学科-景观生态毒理学研究的重要课题。本项目拟以洋河流域为例，在"3S"技术支持下分析近30年来流域土地利用与景观格局的演变，并基于景观空间采集法对流域土壤进行系统布点采样，分析模拟重金属污染及累积的空间分布规律，阐明流域不同土地类型长期利用、利用类型转化、利用强度变化对重金属污染及累积的影响机制。在此基础上选择典型地块，深入分析土壤重金属的各种有效态，探讨其对水、植物、动物和人体健康的潜在风险，并结合土壤理化性质详细阐明典型地块土地利用变化对重金属污染及风险的影响机理，然后由点及面推演流域尺度上土地利用变化对土壤重金属的影响机理机制。借助景观生态学、"3S"和生态毒理学研究手段，揭示流域景观格局水平和垂直变异对土壤重金属污染及风险的影响。本研究对于提升景观生态毒理学的理论研究具有重要科学意义，对于指导流域土地利用与保护具有重要实践价值。

分析了1990-2013年间洋河流域土地利用和景观格局的变异规律，据此采集并测定了洋河不同土地利用和景观格局变化下土壤理化性质和重金属含量变化，将经典统计学、地统计与景观格局分析与ArcGIS技术相结合研究了洋河流域土地利用和景观格局变化对土壤重金属的影响机制，结果表明，1990-2013年间洋河流域耕地面积先增后减，林地面积先减后增，草地面积减少，城乡工矿用地面积增加。洋河流域土壤Cd污染较重，主要分布于以宣化县为中心由东南方向周边呈递减趋势的区域。土壤Cr和Ni的高值区主要集中于兴和县、天镇县与阳高县的交界处以及尚义县、万全县的部分地区。土壤Zn主要分布于兴和县、阳高县和天镇县的大部分地区。洋河流域上游土壤As污染较中下游严重，高值区集中于阳高县南部、兴和县和尚义县交界处以及尚义县北部区。土壤Pb的高值区主要分布于怀安县东部与宣化县西部的交界区和怀来县东北。土壤Cu的高值区主要出现于兴和县、阳高县和天镇县的交界处。由土壤重金属与景观格局指数的分析表明，土壤Cd与河道、企业和道路的距离指数呈极显著正相关，因而污水灌溉、企业和汽车尾气排放是土壤Cd的重要来源；土壤Pb与平均斑块面积、Zn与斑块面积标准差、Ni与斑块面积变异系数均呈显著正相关关系，调整这些景观格局指数可控制土壤重金属污染。耕地、城乡用地和工矿用地土壤重金属变异较大、污染较重，林地和草地土壤重金属的空间变异性较弱、污染较轻。耕地和林地土壤Cd、Cr和Ni的含量较高，草地土壤Cd、As和Pb的含量较高，城乡用地土壤Cd、Cu和As的含量较高，工矿用地土壤Cd、Cu和Pb的含量较高。1990-2013年20年间和2000-2013年10年间由林地和草地转入为耕地土壤受到大部分重金属的轻微污染，而长期耕作土壤受重金属污染最重。20年间由其耕地、草地转入为林地的土壤Cr、Ni、Zn、Pb和Cu含量均高于10年间转入为林地的土壤。城乡工矿用地及其转入土地利用时间越长，其土壤越易累积Cd、Cr、Zn、As和Pb，但不易累积Ni和Cu。不同海拔高度的人为活动是导致洋河流土壤Cd、Cr、As和Ni具有海拔效应的重要原因。