See, cement is made from limestone, a type of rock that’s mostly calcium carbonate.

看，水泥是由石灰石制成的，石灰石是一种主要含有碳酸钙的岩石。

Acid rain dissolves the calcium carbonate in the limestone, that carbonate washes in to the river and acts as a natural buffer.

酸雨溶解了石灰石中的碳酸钙，碳酸盐被冲刷到河流中，起到天然缓冲的作用。

Drs Ding and Kildahl made their version by grinding up barium carbonate, calcium carbonate, niobium oxide and iron oxide, mixing the resulting powders, and then baking the mixture in an oven.

Ding 和 Kildahl 博士通过研磨碳酸钡、碳酸钙、氧化铌和氧化铁，混合所得粉末，然后在烤箱中烘烤混合物来制作他们的版本。