一条河流宽100m，平均水深2m，流速为1m/s，河流坡度为1‰，岸边有一排污口，则污染物在河流中达到均匀混合的长度为（）。
A．37.3km
B．1.18km
C．30.53km
D．1.31km
参考答案：A
解析：
式中：L——达到充分混合断面的长度，m；
B——河流宽度，m；
a——排放口到近岸水边的距离，m；
H——平均水深，m；
u——河流平均流速，m/s；
g——重力加速度，9.8m/s2；
I——河流底坡，m/m。
注意：河流底坡的单位是m/m，带入公式中的数值是0.001。
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