Make sure it's clean river sand, not beach sand.

确保那是干净河沙，不是海滩的沙子。

youdao

While working in the shadow of the iron bridge, he tried his luck by dipping a pan into the river sand.

当他在铁桥下阴凉处干活时，随手把淘金盘浸入河沙中淘了淘，想碰碰运气。

youdao

The results show that the system using new combined fillers has better purification effect on polluted river water and higher hydraulic loading than the system using only river sand as fillers.

结果表明，新型混合填料渗滤系统对受污染河水的净化效果较好，系统的水力负荷也较单独以河砂为填料的渗滤池有大幅提高。

youdao

It lies between sand hills covered with pine trees and rich farmland near the Mississippi River.

VOA: special.2010.01.03

The first course at Dismal River, in the sand hills near tiny Mullen, Neb.

WSJ: Cabot Links, Streamsong, Bandon: When Building a Course Makes Sense | Golf Journal by John Paul Newport

The cassiterite makes up some fraction of the standard sand and river silt there.

FORBES: After Conflict Minerals Comes The Death Metal: Tin. And It's Apple's Fault Again.

The industry uses regulated amounts of water from the Athabasca River to separate bitumen from the sand.

BBC: Canada's 'dirty oil' challenge