"稻鸭共生"生态系统重金属镉的转化、迁移及循环特征研究

Heavy metals contamination have been the subject of much attention because they endanger the food security and people′s health. Heavy metals in fertilizers and feeds is essential for agricultural ecological environment and food security. The pattern of raising duck in paddy field is a model in Chinese traditional agriculture. Which is a combination system of planting and breeding in rice paddy field in subtropical region. Neither chemical pesticides nor herbicides were applied throughout the growth period of rice in rice-duck mutual ecosystems. Rice-duck mutualism is identified as the Green Food and Pollution-Free Agriculture Products. Cd cycling of rice-duck mutual ecosystems is through "rice-duck-soil-water". Ducks is identified as the regulated and the active pool, time of cycle and turnover of materials depend on their time of rice-duck mutualism. Physical and chemic factors can influence Cd cycling of rice-duck mutualism, and anthropic agricultural managements, including fertilizers application, feed input, as well as irrigation, have significant regulations and influences on Cd cycling of the ecosystem. This study will apply Input-Output Analysis method to analyze heavy metals Cd cycling in rice-duck mutual ecosystems based on the monitoring data from field experiments. Input included material embodied in fertilizers, feed, seedling, duckling, irrigation, rainfall while output covered seed, straws and duck in rice-duck mutualism. the return material consists of feces, rice root, weed and insect. Fractionation character and bioavailability of Cd in rice-duck mutual ecosystems will be investigated. The main objectives of this study are to provide theoretical and practical basis for further development and utilization of this classical agricultural technique. The study will be beneficial to adjusting and improving management of fertilizers and feed, reducing the toxicology risk of heavy metal cadmium through food chains, optimizing input-output structure of materials in rice-duck mutualism.

重金属镉(Cd)通过污染饲料和化肥而影响农产品进而危害人体健康已经成为食品安全关注的焦点。以自然资源高效利用和生产无公害有机绿色农产品为目的的"稻鸭共生"生态系统Cd循环是发生在水稻-鸭-土水界面下的循环。鸭是该系统一个"流动"物质库，其周转以鸭与稻田"共生"的时间为周期。该系统Cd循环受一系列物理和化学过程影响，同时因施肥制度、饲料投入、灌溉水等田间管理措施而不同，该循环受人为的补给和控制。本研究以开展的田间试验为研究对象，定性与定量相结合，通过监测化学肥料、饲料、水稻秧苗、雏鸭、灌溉水、降雨等物质输入项，水稻籽粒及秸秆、成鸭、排水等物质输出项，鸭粪、杂草、害虫、水稻根系等系统内部物质循环项，研究分析重金属Cd的转化、迁移及循环特征。研究结果为完善"稻鸭共生"的肥料管理、降低重金属Cd的生态毒理风险及食物链优化管理、合理化物质产投结构，具有重要的意义。

重金属镉(Cd)通过污染饲料和化肥而影响农产品进而危害人体健康已经成为食品安全和生态环境关注的焦点。为完善“稻鸭共生”的肥料和饲料管理、合理化物质产投结构及降低重金属Cd的生态毒理风险，开展了3年田间试验，以常规稻作为对照，采用投入产出法，研究分析“稻鸭共生”生态系统重金属Cd的转化、迁移及循环特征。结果表明：“稻鸭共生”生态系统Cd输入中肥料Cd＞饲料Cd＞秧苗Cd＞雏鸭Cd，其中肥料Cd输入主要是磷肥输入。“稻鸭共生”生态系统Cd输出主要是水稻籽粒Cd和成鸭Cd。“稻鸭共生”系统内循环的Cd主要是鸭粪Cd、杂草Cd、害虫Cd及归还给系统的水稻秸秆Cd和根系Cd。鸭所摄食的Cd主要来自鸭饲料，大鸭饲料Cd输入大于小鸭饲料Cd输入。在“稲-鸭”共生系统中重金属Cd沿食物链的转化、迁移过程被以鸭粪Cd形式放大，且鸭粪Cd高于鸭饲料Cd输入。与常规稻作相比，“稲鸭共生”没有增加水稻植株Cd含量和Cd积累。短期来看，“稻鸭共生”能够提供安全无Cd污染的农产品（鸭和稻米）。“稻鸭共生”能够降低稻田耕层土壤有效镉含量，虽没有显著降低土壤全镉含量，但有益于生物有效态镉向无效态转化。