Land & Environment, AgResearch Ltd, Invermay Research Centre, Private Bag 50034, Mosgiel 9053, New Zealand.
Land & Environment, AgResearch Ltd, Invermay Research Centre, Private Bag 50034, Mosgiel 9053, New Zealand.
Environ Int. 2012 Apr;40:8-14. doi: 10.1016/j.envint.2011.11.009. Epub 2011 Dec 27.
Animal agriculture has been identified as an important source of diffuse faecal microbial pollution of water. Our current understanding of the losses of faecal microbes from grazed pasture systems is however poor. To help synthesise our current knowledge, a simple two reservoir model was constructed to represent the faecal and environmental sources of Escherichia coli found in a grazed pastoral system. The size of the faecal reservoir was modelled on a daily basis with inputs from grazing animals, and losses due to die-off of E. coli and decomposition of the faecal material. Estimates were made of transport coefficients of E. coli losses from the two reservoirs. The concentration of E. coli measured in overland flow and artificial drainage from grazed plots, used for calibration of the model, showed a significant (P<0.0001) decrease with days since last grazing - up to 120 days. Modelled E. coli runoff concentrations calibrated well with the regression line from the measured data up to 120 days. Variability of E. coli concentrations in the source faecal material could account for the variability in the measured runoff concentrations. Measured E. coli concentrations in artificial drainage water from 120 to 1300 days since last grazing appeared to be greater than the model predicted. The longer term data clearly illustrated the need for an environmental reservoir of E. coli in models of grazed pasture systems. Research is needed to understand the behaviour and impact of this environmental reservoir. Scenario analysis using the model indicated that rather than manipulating the faecal material itself post defecation, mitigation options should focus on manipulating grazing management.
动物农业已被确定为水的弥散粪便微生物污染的一个重要来源。然而，我们目前对放牧牧场系统中粪便微生物的损失的了解甚少。为了帮助综合我们目前的知识，构建了一个简单的双储层模型来表示放牧系统中发现的大肠杆菌的粪便和环境来源。粪便储层的大小基于放牧动物的输入，以每日为基础进行建模，并考虑了大肠杆菌死亡和粪便物质分解的损失。估计了大肠杆菌从两个储层中损失的传输系数。用于模型校准的放牧地块径流水和人工排水中测量的大肠杆菌浓度与上次放牧以来的天数呈显著（P<0.0001）下降关系-高达 120 天。在高达 120 天的范围内，经校准的模型大肠杆菌径流水浓度与实测数据的回归线拟合良好。粪便源中大肠杆菌浓度的可变性可以解释实测径流水浓度的可变性。在最后一次放牧 120 至 1300 天后，从人工排水中测量的大肠杆菌浓度似乎高于模型预测值。更长时间的数据清楚地说明了在放牧牧场系统模型中需要有一个大肠杆菌的环境储层。需要研究以了解该环境储层的行为和影响。使用模型进行的情景分析表明，缓解措施不应侧重于操纵粪便本身，而是应侧重于管理放牧。
