娱乐水体隐孢子虫分布迁移规律与多环境介质传播机制研究

Cryptosporidium is one-celled intestinal parasite surrounded by oocyst, whih are environmentally persistent and very resistant to disinfectants. Cryptosporidium species are the most common cause of gastrointestinal illness, such as watery diarrhea, dehydration, fever, nausea, body fatigue, and abdominal cramps. Numerous waterborne outbreaks of cryptosporidiosis have been linked to recreational water. ..The concerns of public health and increasing demands for recreational opportunities combined with Cryptosporidium outbreaks have pushed the researches on Cryptosporidium distribution, occurrence, and migration in recreational surface water system critical important and emergent. ..In this project, recreational water system is defined as recreational water body, bank soil and sediment. This project will (1) investigate Cryptosporidium’s genotype and 3-dimention distributions in Yunlong Lake in Xuzhou. Samples including surface water, medium layer of water, bottom water, sediment, and soil will be collected. Additionally, surface water samples in four seasons will be collected to test the content variation with season and recreational water quality. Genotype of Cryptosporidium will be identified. (2) Discuss impact factors of adsorption of Cryptosporidium by soil and sediment, reveal adsorption mechanism. Cryptosporidium distribution in filed soil and sediment will be studied. Batch scale experiments will be conducted to discuss the impact factors of adsorption. Interaction between Cryptosporidium and particles will be measured. (3) Discuss overland flow and preference flow process and control parameters, especially 2-direction preference flow process, and reveal Cryptosporidium migration mechanism with overland flow and preference flow. Rainfall experiments will be conducted for the migration study. The two process, adsorption and migration, occurred in root micro-environment will be studied. The combined behaviors, preference flow formed by roots and adsorption by vegetable, will be discussed to reveal the role of roots playing on Cryptosporidium migration and adsorption. The control mechanism and the dominant behavior under this condition will also be discussed. ..The objective of this project is to reveal the Cryptosporidium genotype, desorption and migration process, control factors, and transport mechanism, in order to provide theoretical foundation on recreational water management, ensure swimming safety in public recreational water body and protect public health...The main differences from the previous research include, 3-dimention distributions of Cryptosporidium in Yunlong Lake will be studied at the first time, genotype will be identified, adsorption and migration of Cryptosporidium will be discussed in recreational water system, 2-direction preference flow and adsorption by roots will be studied.

娱乐水体是隐孢子虫病暴发与传播的主要媒介，我国尚未开展娱乐水体中隐孢子虫的分布调查，对隐孢子虫在其中的传播过程亦无科学认识。针对以上问题，本课题拟对江苏省徐州市主要娱乐水体系统中隐孢子虫的三维多相分布进行调查研究并检验其基因型；将场地调查与实验模拟相结合，研究隐孢子虫由边坡土壤和底泥沉积物向上覆水的释放和迁移规律及影响因素，以确定典型娱乐水体中隐孢子虫的物种类别和污染水平，阐明隐孢子虫在多环境介质间的传播机制。本课题在分析隐孢子虫随地表径流传播的基础上，创新性地引入地下二维优先流的概念，通过研究根系二维优先流的迁移作用，探讨隐孢子虫在根际微环境中的吸附与迁移双重作用机理，突破优先流研究的局限性。并通过优选特征参数实现隐孢子虫污染的暴发预警。

当今全球暴发的消化道疾病中，隐孢子虫导致的腹泻在寄生虫腹泻中排首位，儿童和免疫力差的人群更易感染。娱乐功能水体中隐孢子虫损害人体健康的同时，也给当地的经济发展带来了巨大损失。为了减少隐孢子虫在娱乐水体的暴发，本项目开展了以下三方面研究，得出以下结论：1)研究区水体和底泥隐孢子虫检出率为35%和47%，主要基因型为C. andersoni。在雨季丰水期，隐孢子虫卵囊的检出率高于与其他时期。其分布与大肠杆菌分布相关性较好。2)植物根系对隐孢子虫卵囊替代物有明显的吸附作用。植物根系表面为隐孢子虫卵囊替代物提供了大量的结合位点，使得隐孢子虫卵囊替代物吸附在植物根的表面，减少了隐孢子虫卵囊替代物由土壤与根系体系向水体的迁移。高pH值抑制植物根对隐孢子虫卵囊替代物的吸附。高的钠离子强度促进植物根对隐孢子虫卵囊替代物的吸附作用。根据胶体基本理论，低pH或高离子强度通过压缩表面双电子层使其降稳，进而促进植物根系表面或土壤颗粒的截留作用。植物根系对底泥沉积物中隐孢子虫卵囊替代物具有的吸附作用，从而抑制其向上覆水的释放。3)高降雨强度和频率导致大量隐孢子虫迁移。较高的离子强度增加了胶体的吸附速率，使得胶体强烈地吸附于高离子强度的物体上，抑制其迁移。有机质的结合为胶体提供了额外的疏水性结合位点，增强土壤对胶体的吸附作用，抑制其迁移。含沙量高的土壤保水能力较差，促进隐孢子虫随地表径流迁移。一维优先流促进了隐孢子虫由表层土壤向深层土壤和地下水的迁移，二维优先流促进其由边坡土壤向周围水体的迁移。较根系对隐孢子虫的吸附作用相比，根系优先流导致的隐孢子虫迁移占主导。