Magnesium is an important component of chlorophyll. If there is no
magnesium in the soil, plants will not be able to make chlorophyll, they will be yellow
rather than green and will not be able to carry out photosynthesis so they will not grow
properly.
Calcium is necessary for our teeth, bones, muscles and nerves. Calcium
is absorbed by plants from the soil so most of our food contains some calcium. Young
mammals need lots of calcium for their growing teeth and bones, so there is a lot of
calcium in milk. There is also a lot of calcium in your drinking water if you live in a
"hard water" district.
Strontium can also get out of the soil and into our bones through the
food chain. Unlike calcium, our bones cannot remove strontium: this is only a problem with
radioactive Strontium 90.
Barium sulphate can be used as a "Barium Meal" to make our
intestines visible to X-rays; radiographers can use this to find ulcers. Soluble Barium is
very toxic, but since Barium Sulphate is very insoluble it does not do us any harm.
