在河流水文测验、河工模型试验、水质评价及工农业取水中，通常采用比重瓶法测验含沙量。在含沙量较小时，因水中溶解质含量较大，用比重瓶法测验得到的含沙量往往大于实际含沙量，但测验者常常怀疑测验过程或测验仪器出现误差，而忽略其真正原因。通过某城市供水沉沙池试验的含沙量测验发现，影响低含沙量测验误差的潜在原因就是浑水中溶解质含量，它对含沙量的影响远远大于水体自身含沙量；此外，温度测验误差对含沙量的影响较大，并且含沙量越小，温度测验误差对含沙量的影响越大。基于此，提出了比重瓶法测验低含沙量的改进方法，得到了与烘干法基本一致的测验结果，为低含沙量测验提供了一些借鉴和参考。%Pycnometer method has been widely used in sediment concentration measurements such as river hydrolog⁃ical measurement, model test of river engineering, evaluation of water quality and water intake in industry and agri⁃culture. However, when sediment concentration is low, the sediment concentration measured by pycnometer method is usually greater than the actual value because the content of dissolved matter is big. In face of such phenomenon, test engineers often doubt error of test instruments or test process, but can’ t find the real reasons. Through the sedi⁃ment concentration measurement of desilting basin test of water supply in a city, we found that the content of dis⁃solved matter in the water is crucial to the measurement error of low sediment concentration;nevertheless, tempera⁃ture greatly affects sediment concentration, and the smaller the sediment concentration is, the bigger the effect of temperature error is. On this basis, we put forward the improved pycnometer method to measure low sediment con⁃centration, and test results by the method is basically consistent with those by drying method. Finally, it can pro⁃vide reference for test with low sediment concentration.
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