洪涝灾害后通江河道砼护坡控制钉螺效果的纵向观察

Oncomelania snail control by concrete bank of river in connection with the Yangtze River after floodwater

目的评价洪涝灾害后通江河道砼护坡控制钉螺效果.方法选择受长江洪涝灾害影响的通江河道及其流域作为研究现场,对通江河道砼护坡工程实施前后流域内河道、灌区及通江口外江滩进行钉螺消长的纵向观察,评价护坡工程控制钉螺效果;同时对河道内潮位变化、钉螺扩散、滩地淤积等影响因素进行观察研究.结果实施通江河道砼护坡3年,河道钉螺面积下降74.68%,有螺框出现率下降61.15%,活螺密度下降85.65%,钉螺感染率及感染性钉螺面积降至0.但其后钉螺面积则徘徊不下,有螺框出现率上升,并再次出现感染性钉螺;内陆灌区钉螺面积、有螺框出现率、活螺密度均呈缓慢波动上升趋势;河道内水体持续保持血吸虫感染性.影响因素研究表明：通江河道内潮位变幅大,月平均潮位差在3.45～5.57 m;河道内由于工程原因和泥沙淤积,存在大量孳生钉螺的淤积滩地;汛期河道漂浮物平均携带钉螺18.10只/kg;通江口外存在大面积江滩钉螺,钉螺密度呈增长趋势;同时河道沿线涵闸均缺乏防螺措施.结论在水位未控制的通江河道单纯进行砼护坡不能防止钉螺扩散,也不能完全消除水体血吸虫感染性.建议此类通江河道应优先考虑控制水位,增加防螺措施,同时最大限度控制和杀灭通江口外江滩钉螺.

Objective To evaluate the effect of concrete bank on controlling Oncomelania snails in rivers connecting with the Yangtze River after floodwater. Methods The river in connection with the Yangtze River and the drainage area were selected as the research field. The longitudinal observation of the change of distributing status of Oncomelania snails was carried out in the riverway, the irrigated area and the marshland outside the outfall of water system of the Bianmin River. At the same time, the impact factors as change of the tide height, the spread of Oncomelania snails and the silt shoal were investigated. Results The areas with snails, the rate of frame with living snails and the density of living snails dropped by 74.68%, 61.15% and 85.65% respectively, and the snail infection rate and the area with infected snails reduced to zero duing three years after concrete bank of river in the connection with the Yangtze River. And then, the areas with snails paced up and down, the rate of frame of living snails raised and infected snails appeared again. The areas with snails, rate of fram of living snails, density of living snails were increasing slowly in the irrigated area. And the infectiousness of schistosome was retained in the riverway. The research showed that the change of tide height was large, the average tide height of a month being from 3.45 --5.57 m, and there was a lot of the silt shoal in the riverway and the average number of schlepped snails by the float was 18.10 snail/kg. There were a lot of marshland with snails outside the outfall in connection with the Yangtze River, and the density of living snails increased. The culverts and water gates along the river was devoid of snail control establishment. Conclusions Concrete bank alone could not control the diffusion of snails and eliminate the infectiousness of schistosome completely in rivers in connection with the Yangtze River when the water level could not be controlled. It is suggested that water level control should be the first choice in snail control. At the same time, other snail control measures should be taken, especially in marshland outside the outfall in connection with the Yangtze River.