Biogeochemical Cycles
COMMONALITIES AMONG THE CYCLES:
>exist in the hydro-, litho-, biosphere, & sometimes the
atmosphere
>there are “pools” or reservoirs
>they are changed chemically or biochemically
>there are “fluxes”, or movement between pools
>transformations (changes) are important & can lead to
positive or negative consequences
SOURCE – a reservoir that releases more nutrients than it
accepts
SINK – a reservoir that accepts more nutrients than it releases
CARBON CYCLE
WHERE USED BIOLOGICALLY:
>for structural growth – part of plants &
bones
>cellular respiration – releases carbon
(carbon dioxide)
>photosynthesis – removes carbon dioxide
>decomposition
>largest reservoir is sedimentary rock (fossil
fuels & sediments), then oceans (calcium
carbonate)
WHERE USED GEOLOGICALLY:
>volcanic activity
>fossil fuels
>sedimentary rocks – limestone &
carbonate rocks
>oceans – calcium carbonate in animal shells
CHEMICAL CHANGES TAKING PLACE:
>CO2 used to make sugars
>CO2 used to make calcium carbonate
>sugars broken down & releasing CO2
>dead organisms decomposing or turning
into fossil fuels (coal, oil, natural gas)
HUMAN INFLUENCE:
>burning fossil fuels
>clearing/burning forests & rainforests
>mining fossils, minerals
>planting crops, trees, etc.
NITROGEN CYCLE
WHERE USED BIOLOGICALLY:
>fertilizer for plants
>78% of the atmosphere is nitrogen & it is
essential for making amino acids & proteins,
DNA, RNA
>bacterial nitrogen fixation – nitrogen gas changed to
nitrites and nitrates
>animal waste – ammonia NH3
>bacterial denitrification – release nitrogen gas
WHERE USED GEOLOGICALLY:
>deposition of nitrogen compounds & animal
excretion
>decaying organic matter
>nitrates move down through soil by
leaching, are dissolved in groundwater & may go to ocean
sediments
CHEMICAL CHANGES TAKING PLACE:
>nitrogen gas changed to nitrates & nitrites
>ammonia (NH3) changed to nitrates & nitrites
>nitric oxide (from combustion of fossil fuels) changed to
nitric acid (forms acid precipitation)
HUMAN INFLUENCE:
>manufacture & use of synthetic fertilizer
>fossil fuel use
>using natural, organic fertilizer
PHOSPHORUS
WHERE USED BIOLOGICALLY:
>key component of DNA, RNA, & ATP & ADP
> in cell membranes, bones, teeth
>excretion of urea, bird & bat guano
>marine organism use
>plants use phosphate dissolved in water
WHERE USED GEOLOGICALLY:
>most phosphorus is in rocks, ocean sediments, & soil
(mostly calcium phosphate)
>erosion, weathering, & uplifting releases phosphate
>phosphatic rock from ancient seas can
be mined for phosphorus
CHEMICAL CHANGES TAKING PLACE:
> phosphate (PO4) is changed into organic compounds
>decomposition returns phosphorus to the soil
HUMAN INFLUENCE:
>making synthetic fertilizer
>using guano for fertilizer
TAKE-HOME MESSAGE
THE CYCLES WORK TOGETHER, AND CHANGING ONE
CYCLE WILL CHANGE THE OTHER
THE CARBON, NITROGEN, & PHORPHORUS CYCLES
HAVE ELEMENTS THAT ARE ESSENTIAL FOR LIFE ON
EARTH
HUMAN ACTIVITIES HAVE ACCELERATED GLOBAL
CHANGES OF ELEMENTS, RESULTING IN CHANGING
CONCENTRATIONS IN THE LAND, ATMOSPHERE, &
WATER
MANY ENVIRONMENTAL PROBLEMS STARTED DUE TO
ACCELERATED BIOGEOCHEMICAL CHANGES IN THE
ELEMENTS, WHICH BECOME “POLLUTANTS WHEN THEY
ARE OUT OF BALANCE