Environmental Engineering Reference
In-Depth Information
our.food.production.systems.(e.g.,.crop.growth.and.ish.culture).and.also.to.
avoid.the.chance.for.these.contaminants.transforming.into.more.toxic.forms.
DifferentTypesofEnvironmentalPollutants
Heavy Metals
Heavy.metals.are.naturally.occurring.in.the.environment..However,.human.
activities. have. greatly. altered. their. biochemical. and. geochemical. cycles,.
and.their.balance.in.the.nature..They.are.mainly.emitted.through.industrial.
activities,. such. as. fuel. combustion. (diffusion. point. sources,. e.g.,. from. traf-
ic),. mineral. extraction,. and. metal. smelting. (industrial. point. sources).. This.
is.especially.true.as.China.is.full.of.mineral.resources..China.is.the.largest.
producer.of.coal.and.also.possesses.ample.reserves.of.tungsten,.tin,.stibium,.
zinc,.titanium,.tantalum,.thallium,.lead,.nickel,.mercury,.molybdenum,.nio-
bium,.and.aluminum.(State.Statistical.Bureau.1998)..Mining.of.these.reserves.
has. given. rise. to. the. large-scale. destruction. of. land. surface. leading. to. soil.
erosion. and. emissions. of. heavy. metals. into. the. immediate. environment,.
enhancing.their.entry.into.food.production.systems,.for.example,.crop.and.
ish.cultivation.
Environmental. contamination. and. exposure. (through. oral. intake,. inha-
lation,. and. dermal. contact). to. heavy. metals. has. become. a. serious. public.
health.concern.worldwide..Some.of.the.heavy.metalloid/metals,.for.example,.
arsenic.(As),.cadmium.(Cd),.mercury.(Hg),.and.lead.(Pb).are.highly.toxic,.and.
they.have.become.topical.issues.since.the.mid-1970s..In.fact,.the.Priority.List.
of.the.“Top.20.Hazardous.Substances”.included.As.(irst.place),.Pb.(second.
place),.Hg.(third.place),.and.Cd.(seventh.place),.a.list.released.by.the.Agency.
for. Toxic. Substances. and. Disease. Registry. (ATSDR).. Some. of. these. heavy.
metal. elements. such. as. Cu. and. Ni. are. needed. in. trace. amounts. in. biota,.
including.humans,.but.would.become.toxic.under.high.concentrations..Most.
others. are.toxic.or.carcinogenic,. imposing.adverse. effects. on. different. sys-
tems:.As,.Hg,.and.Pb.on.central.nervous.system;.Cd,.Hg,.and.Pb.on.kidneys.
or.liver;.and.Cd,.Cu,.Cr,.and.Ni.on.skin,.bones,.and.teeth.(ATSDR.2001).
Persistent Organic Pollutants
Stockholm Convention POPs
The.original.list.of.the.12.POPs.listed.in.The.Stockholm.Convention.on.POPs.
included.7.chlorinated.hydrocarbon.pesticides.(aldrin,.chlordane,.DDT,.diel-
drin,.endrin,.heptachlor,.hexachlorobenzene,.mirex,.toxaphene),.2.industrial.
chemicals. (PCB. and. hexachlorobenzene),. and. 2. unintended. byproducts.
(dioxins. and. furans),. and. 10. chemicals. have. been. included. in. the. control.
Search WWH ::
Custom Search