流域非点源磷污染的遗留效应研究进展

Progress on legacy effects of watershed non-point source phosphorus pollution

流域非点源磷污染的遗留效应是许多流域经过多年污染控制努力后水质仍未见成效的重要原因。本文综述了流域非点源磷污染遗留效应的形成过程机理、模型方法及对水质的影响。由于化肥施用等人为磷过量输入以及水文和生物地球化学滞后性,磷在土壤、沉积物、地下水等介质中大量累积,在人为扰动、气候变化等作用下,累积的遗留磷会重新释放/流失,因而成为受纳水体长期的污染源。数学模型是解析流域非点源磷污染遗留效应的主要方法,现行的模型仍以统计模型为主,其中ELEMeNT-P模型是唯一针对遗留效应问题研发的过程性模型。模型估算结果表明,很多流域的遗留磷是受纳水体磷污染的重要甚至主要原因,且其污染影响可长达数十年到数百年。总体而言,目前对流域非点源磷污染遗留效应的过程机制尚未完全明确,相关模型尚难以模拟遗留效应的时空分布特征。未来研究应深入探究流域遗留磷累积-释放-输移的动态过程机制,改进模型的水文和生物地球化学过程模块,强化模型的多时空尺度模拟功能及多重验证,以精确刻画流域遗留磷的污染贡献及其时空分布特征,为突破非点源磷污染治理困境提供关键科学依据。

The legacy effect of non-point source phosphorus(P)pollution is an important cause of the failure to yield the expected water quality improvements after implementing P pollution control measures for a decade to several decades in many watersheds.This review provides a systematic overview of the mechanism,model,and impacts on water quality of legacy effects.Due to excessive anthropogenic P inputs(fertilizer application),hydrologic and biogeochemical lag effects,substantial amounts of P have accumulated in the soils,sediments,and groundwater over long-term periods in many watersheds.With anthropogenic disturbance and environmental changes,legacy P can be re-released/lost,becoming a long-term pollution source to receiving water bodies.Models are the main method to quantify the legacy effects of watershed non-point source P pollution.Currently,statistical models are major tools,and the ELEMeNT-P model is the only efficient process model developed for legacy effects.The modeled results indicate that watershed legacy P sources contribute to considerable or main proportions of P pollution loads in receiving waters,and such contributions could persist for decades to centuries.Overall,the mechanisms of the watershed non-point source P pollution legacy effect have not been fully clarified,and the available models have difficulty addressing the spatial and temporal distribution characteristics of the legacy effect.In the future,the mechanisms of P accumulation-release-transport dynamics within the watershed continuum should be fully addressed.Then the hydrological and biogeochemical modules should be incorporated and improved in the available models.The models should be improved to simulate watershed P dynamics at multi-temporal and multi-spatial scales,and be efficiently validated by multiple measures.Based on these efforts,we can accurately quantify watershed legacy P accumulation locations,magnitudes,contributed pollution loads,and their spatiotemporal distributions,guiding the development of efficient watershed P pollution control strategies.