48
in pollution associated with manufacturing during World War One and a subsequent
decrease as the economy slowed during the Great Depression, for example. The
isotope cesium-137 is produced in nuclear reactors and nuclear weapons. Like the
concentration of lead, down-core trends in cesium-137 activity can be traced back
to human activities of known ages. Following World War Two, several countries
sought to acquire, develop, and build nuclear weapons, which required them to be
tested at places like Bikini Atoll in the Pacific Ocean. These tests generated
cesium-137 that entered the atmosphere and was distributed by winds around the
world and was eventually rained out onto surfaces including salt marshes in eastern
North America such as those in North Carolina. The deepest occurrence of
cesium-137 is usually taken as evidence for nuclear testing becoming increasingly
common in the early 1950s and it peaked it in the early 1960s when above-ground
testing of nuclear weapons was banned, and most countries adhered to the new
rules. Once the testing went physically underground, the cesium-137 did not enter
the atmosphere.
As anyone who suffers from hay fever knows, plants produce huge quantities of
pollen and those pollen grains have a shape and structure that varies among species
(hence we can be allergic to one type, but not others). Pollen is extremely resistant
to decay and hard to break down. Therefore, when it settles out on the surface of a
Fig. 3.9 The wooden
schoolhouse in Russia
where we stayed while
working on salt marshes
around the White Sea. We
nicknamed the large dog
“Wolfy” and he followed
us into the field most days
and most nights he forced
his way through the front
door and tried to climb into
one of our sleeping bags.
Coauthor Horton wears a
red cap. (Image by
A.C. Kemp)
A. C. Kemp and B. P. Horton
in pollution associated with manufacturing during World War One and a subsequent
decrease as the economy slowed during the Great Depression, for example. The
isotope cesium-137 is produced in nuclear reactors and nuclear weapons. Like the
concentration of lead, down-core trends in cesium-137 activity can be traced back
to human activities of known ages. Following World War Two, several countries
sought to acquire, develop, and build nuclear weapons, which required them to be
tested at places like Bikini Atoll in the Pacific Ocean. These tests generated
cesium-137 that entered the atmosphere and was distributed by winds around the
world and was eventually rained out onto surfaces including salt marshes in eastern
North America such as those in North Carolina. The deepest occurrence of
cesium-137 is usually taken as evidence for nuclear testing becoming increasingly
common in the early 1950s and it peaked it in the early 1960s when above-ground
testing of nuclear weapons was banned, and most countries adhered to the new
rules. Once the testing went physically underground, the cesium-137 did not enter
the atmosphere.
As anyone who suffers from hay fever knows, plants produce huge quantities of
pollen and those pollen grains have a shape and structure that varies among species
(hence we can be allergic to one type, but not others). Pollen is extremely resistant
to decay and hard to break down. Therefore, when it settles out on the surface of a
Fig. 3.9 The wooden
schoolhouse in Russia
where we stayed while
working on salt marshes
around the White Sea. We
nicknamed the large dog
“Wolfy” and he followed
us into the field most days
and most nights he forced
his way through the front
door and tried to climb into
one of our sleeping bags.
Coauthor Horton wears a
red cap. (Image by
A.C. Kemp)
A. C. Kemp and B. P. Horton