污染足迹及其在区域水污染压力评估中的应用——以太湖流域上游湖州市为例

传统生态足迹理论虽然在可持续发展评价等方面得到了广泛的应用,但却仍然无法全面衡量人类活动对生态系统造成的各种影响。其无法全面评估人类活动的根源在于,土地功能排他性假设限制了其对利用生态系统非生物生产性产品和服务的人类活动的衡量。为了摆脱传统生态足迹理论的局限性,建议承认土地功能多样性的客观事实,将生态足迹构建于多种生态系统服务功能之上。针对传统生态足迹对定义中废弃物吸纳的考虑不足,提出了基于污染物吸纳功能的生态足迹,即污染足迹。污染足迹不是对传统生态足迹中能源足迹的简单置换,而是能够囊括人类活动产生的大部分污染物,并可以根据不同的污染物类别或类型进一步细化的足迹类型。构建了太湖流域有机物、氮和磷污染足迹模型,并利用该模型对流域上游湖州市的水污染压力进行了综合评估。结果表明:(1)2007年湖州市污染足迹为39948.73 hm²,东部平原地区污染足迹较大,西部丘陵地区污染足迹相对较小;(2)湖州市人类活动排放的氮磷污染物对水域空间的生态占用已经远远超过了有机污染物;(3)2007年湖州市污染承载力为20896.00 hm²,污染赤字为19052.73 hm²,人类排污活动俨然超出了当地水域的承载能力;(4)2007年湖州市污染压力指数为1.91,当地水环境总体上处于轻度接近中度污染压力;(5)湖州市水污染压力较大的地区,区域内人类活动的维持建立在区域水环境质量恶化或污染物向下游输移的基础之上。

Pollution footprint and its application in regional water pollution pressure assessment: a case study of Huzhou City in the upstream of Taihu Lake Watershed

After nearly twenty years of development, ecological footprint has become one of the most widely applied methods for sustainable development assessment. The ecological footprint is, however, unable to evaluate the impacts of human activities on natural ecosystems in an all-round way. The authors indicated that the failure of the conventional ecological footprint in providing a comprehensive measurement on human impacts lies in that the assumption of the exclusive land function has prevented the non-bioproductive commodities and services from being considered. To overcome the limitations in conventional ecological footprint theories, the authors suggested that the multi-functionality of land be acknowledged and the ecological footprint be built on multiple ecosystem services. The authors then proposed the concept of pollution footprint and elaborated its model construction and calculation methods. The pollution footprint, an ecological footprint based on pollution absorption, is a typical ecosystem services-based ecological footprint. It should be noted that the pollution footprint is not a simple replacement of energy footprint in the conventional ecological footprint; it is able to account for most pollutants incurred by human activities and to be further clarified in terms of different classes or types of pollutants. Given that organic matter, nitrogen and phosphorus are the main pollutants in Taihu Lake Watershed, the authors constructed organic, nitrogen and phosphorus pollutant footprint models and then utilized them to evaluate water pollution pressure of Huzhou City in the upstream of the watershed. Results showed that (1) pollution footprint of Huzhou City in 2007 was 39948.73 hm², of which the eastern plain river-net areas accounted for a larger part than the western mountainous and hilly areas; (2) phosphorus and nitrogen pollutant footprints were larger than organic pollutant footprint in most counties and even towns of Huzhou City, which indicated that surplus phosphorus and nitrogen released by human activities there needed more water areas to assimilate than that organic pollutants required; (3) pollution capacity of Huzhou city in 2007 was 20896.00 hm², leaving 19052.73 hm² as pollution deficit, which implied that the amount of pollutants discharged by human activities there went far beyond the assimilation ability of local water body; (4) pollution pressure index of Huzhou City in 2007 was 1.91, revealing that the city had a moderate pollution pressure as a whole; (5) human activities in high-pollution-pressure regions were maintained through deterioration of local water quality or transport of pollutants to the down stream.