Environmental Pollution Final Exam
Leading causes of water pollution are
-Agricultural activities -Sediment eroded from lands -Oxygen demanding wastes (org. carbon) -Fertilizers, pesticides &bacteria from livestock -industrial facilities -mining
Biological Oxygen Demand (BOD)
-All materials that consume dissolved oxygen -High BOD results in anaerobic conditions and harms higher life forms -Want low BOD
Haber-Bosh process
-Allows artificial, industrial nitrogen fixation -400million tons of N fertillizer per year -this process feeds the world -process is very energy intensive (breaking of N2 triple bond)
Pourbaix Diagrams: Aluminium
-Aluminium normally in the form of aluminium hydroxides (at high pH) -If you lower pH can have toxic Aluminium (Al3+) ions which are mobile -Only get released if you are in oxic environment with surface soils, not relevant in ocean or rice fields etc
Agricultural Sources of Phosphorus
-Animal manure, excess fertilizer, soil erosion -one of the largest sources of nitrogen and phosphorus pollution -Stormwater: precipitations runoff from hard surfaces., lawns etc
Biggest difference between Arsenate and Arsenite
-Arsenate As(V) is strongly absorbed to minerals meaning LOW mobility -Arsenite As(3) abrobs less and to fewer minerals, HIGHER mobility
Differences in toxicity in Arsenate and Arsenite
-Arsenate is toxic b/c it is a molecular analog of phosphate, inhibits oxidative phosphorylation, centers cell throuh phosphate transporters -Arsenite is MORE toxic b/c binds to sulfhydryl groups impoaring function of many proteins, affects respiration etc
Phosphate timeline in laundry detergent
-Ban began in 1970 in some states -Most states do not have ban -big problem in great lakes
Oxygen-demanding wastes
-Biological oxygen demand: waste waster, animal wastes. org. matter (wold pulp), oil etc
Nonpoint sources are
-Broad, diffuse areas -ex. rainfall or snowmelt washes pollutants from land to surface water -ex. runoff of fertilizers and pesticides from croplands, logged forests lawns and gold courses Agricultural areas
"Heavy metal"
-Ca and K are metals but not heavy -Pb and Hg are "heavy" Lead MW: 207.59 11x heavier than water -Hg MW: 200.59 13.5x heavier than water
Cadmium in Chesapeake Bay
-Cadmium is a problem in the Chesapeake Bay -Cd is toxic to humans and other organisms -Cd-Chloro complexes are less bioavailabCd- -Cd-chloro-complexes less bioavailable than free Cd2+ -Organisms near the river outlet bio-accumulate more cadmium than near the open ocean
Transitional Metals:
-Can form complexes with all types of ligands -Mn2+, Zn2+, Fe2+, Ni2+, Co2+, Cu2+, Sn4+ -Fall between Type A & B
Single Variable diagrams: Cd
-Cd speciation changes as a function of chloride (Cl-) concentrations -Depending what type of environment you are in Cd can appear in different forms with Cl
Point Sources are
-Discharge of pollutants at specific locations Ex. factories, animal feed lots, underground mines, oil wells and oil tankers
Environmental Impacts of high NH4:
-Eutrophication -max. acceptable level in water .5 mg/L -Creates chloramines in drinking water supplies
Environmental Impacts of high NO3
-Eutrophication in rivers/lakes -NO3 not strongly bound to soil particles (low AEC) easily leachable -Toxic to humans -Blue baby syndrome
Type A metals:
-Ex. K+, Na+, Ca2+, Sr2+, Ba2+, Al3+ -They like Oxygen and Fluorine containing ligands (form oxides and hydroxides) -Only form weak complexes with halides -Form insoluble compounds (precipitate out wth OH-, CO3 2-, PO4 3-)
Eutrophication is
-Excess nutrients of nitrogen and phosphorus -Dense growths of algae and cyanobacteria -Oxygen depleted by bacteria that decompose the algae
What happens with Fe in soils that floods/water saturated?
-Fe(3) to Fe(2) reduction, Fe(2) is mobile and moves vertically (getting dissolved in saturated layers) -Soil horizons bleached and grey -Called Hyric Soils
Difference between Fe2+ and Fe3+
-Fe2+ is soluble and mobile -Iron hydroxides are immobile
Sources (inputs) of Ammonium and Nitrate in soils
-Fertilization in agriculture: Ammonium - Nitrate - Org. N (manure) -Heavy application of nitrogen fertilizers, excess is leaching to watersheds
Negative pE conditions mean (pourbaix diagram)
-Flooded, saturated environmental conditions (anoxic environments ex. swamps) -reduced conditions -examples: paddy rice feilds, sediments, high OM and submerged (water-logged)
What environments have low Cl concentrations?
-Freshwater environments -More likely to have Cd 2+
Pourbaix Diagram: Arsenic (As)
-Has Arsenite (As(3) form) H2AsO3 Reduced State -Arsenate (As(v) form) AsO4 3- HAsO4 2- H2AsO4 Oxidation states
Photochemistry plays a role in Mercury how
-In soil present as oxidized mercury(2) -sunlight (UV-A & B) helps reduce Hg(2) to Hg(0) -can happen in dark
No oxygen available (anaerobic respiration) Denitrification process
-Instead of oxygen, use nitrogen -Happens because Gibbs -480 meaning not using as much energy
Two major fluxes are naturally occur are
-Land to atmosphere flux (30) -Land sinks (-160)
Type B Metals:
-Like to form complexes with Haldies (I- > Br- > Cl- > F-) -High, electro-negativity, form covalent bonds with ligands -Common and stable (insoluble) complexes with sulphides & organosulphides -Complexes w/ Carbon (Org. Matter)
Line of Pourbaix Diagrams
-Lines define boundary conditions -Between lines is when water conditions is stable -Reduction of water below line -Above is oxidation of water
Phosphorus in water
-Log scale -At some point you see lake/stream with certain phosphorus content (ex. 50% of lake had below 20 microgram per liter) -increases from 2008-2014 -no corresponding increase in N, strong increase in undeveloped areas -reasons: runoff from agriculture, wastewater, stormwater?
Dimethl-Hg (Me2Hg)
-Most toxic form of Hg -readily absorbs through skin -can result in immediate death
Pourbaix diagram: Iron
-Not a contaminant -Under reducing conditions iron is present as Fe2+ or Fe(OH)2 both are in oxidizing states of iron -Under oxidized Fe is 3+ with Fe(OH)3 (higher redox state)
Role of OM (organic matter) in Pourbaix diagrams
-OM want to respire (use O2) to CO2 -If no O2 is available they use other molecules -Respiration reduces redox conditions (in the absence of O2)
Natural Sources of Arsenic
-Ores of metals -Broadly distributed in many subsurface drinking water aquifers
What is nitrogen fixation?
-Process of converting nitrogen gas into ammonia -some bacteria that do this live in plant roots
Methods to remediate eutrophication:
-Remove excess weeds -Use herbicides and algaecides -Pump in oxygen -Most lakes will recover is excessive inputs of nutrients stop
Anthropogenic Sources of Arsenic:
-Smelter -Coal combustion -Runoff from mine tailings -Arsenic based pesticides -Pigment production for paints and dyes -Pressure treated wood
Summary of Aerobic and Anerobic Respiration process
-Soils are first oxic (arerobic respiration) -Flooding: microbes use up O2, then NO3 then use SO4 -pE values drop *Process driven by available OC and microbes that to oxidize(eat) OC
Hg(1) and Hg(2)
-Strong complexation with Cl, S and Org. Matter -In surface soils and water, Hg is complexed with org.matter -Under reducing conditions, Hg forms very insoluble Hg-Sulfide compounds
Process of mercury methylation
-Sulfate reducing bacteria (SRB) most dominant -Not all mercury compounds have some bioavailability -methlyation dependent on a lot of things (pH, temp., redox etc)
Mercuric/Mercury (HgII)
-Sulfur plays important role in complexes -under reducing states HgS is formed -Does not cross blood-brain barrier
Flint water is bad because
-They did not add ortho-phosphate -Had high levels of Chloride -Phosphate-lead complex is insoluble, forms a passivation layer, protects metal from oxidants -Oxidants (such as O2) disrupts the layer which oxidizes Pb to Pb2+ (soluble)
Mercury Speciation (redox cycling of mercury)
-Under certain conditions Hg(0) can turn into Hg(2) under oxidation -oxidized mercury more water soluble -gaseous elemental mercury can be taken up by plants
What happens in soils when soils drain again and/or exposed to O2?
-When exposed to oxygen, Fe(2) to Fe(3) oxidation and precipitation as Fe(3)-oxides -Fe(3) oxides are brown and red colors -Color patterns indicative of where oxygen is available (ex. root channels-preferential flow pattern)
Ammonia is favored in which conditions?
-alkaline soils (deserts, high pH) -low CEC -low nitrification rates
Elemental Mercury Hg(0)
-crosses blood brain barrier placenta -Has vapor pressure, semi volatile -distributes through atmosphere
Mercurous/Mercury (HgI)
-ex. Hg2Cl2 -in oxidation state -poorly soluble -form complexes
Eutrophication can cause
-explosive growth of phytoplankton that eventually die and are consumed by bacteria -depletes oxygen -results in dead zone containing little marine life
Monomethyl-Hg (CH3Hg+)
-forms under reducing (little oxygen) environments -Toxic -crosses blood-brain barrier, not soluble, not easily excretable -interferes with DNA transcription, protein synthesis etc
Microbes can eat up
-organic pollutants -synthetic pollutants
Nitrification:
-oxidation of NH4 in the environment -optimal pH is 6.5-8 -Two step reaction, both driven by autrophic bacteria -produces acidity
Prevention/Reduction of Eutrophication:
-remove nitrates and phosphates -recycle nutrients into the soil
Nitrate in Soils:
-subject to plant uptake -Nitrate remains in solution phase, readily leached out of soils and into surface/groundwater -subject to denitrification
Positive pE values mean (pourbaix diagram)
-well-aerated surface water conditions -oxygenated surface water -connected to the atmosphere -examples: rivers, lakes, surface oceans, mine wastes (low ph)
In 1959 laundry detergents in US contained between ___ % phosphorus In 1969 how much was there?
1959: 7-12% 1969: 15-17%
In 1970 what was in reduction of phosphorus in detergent? What was it in 1971?
1970: 8% 1971: 2.2%
In natural environment we are usually between a pH of
4 and 8 Ocean environmental usually around 8-8.5
Add the chemical form in the blanks: Lead forms stable complexes with [A] leading to precipitation of a mineral passivation layer in lead pipes that protects lead from dissolution in water. However, both [B] and [C] act as oxidants and corrodes the passivation layer which results in a release of lead in the form of [D].
A- HPO4 2- (hydrogen phosphate) B- Cl- C- O2 D- Pb2+
Graph of Single Varible Diagram: Phosphorus
At high pH, phosphate will exist in its ionic form At pH 14 (doesnt exist in real life environment) it will be pure phosphate As pH lessens will lose phosphate ion and show up in protonated form As go lower Hydrogen ion picks up another proton and continues At very low pH, the acid is dominating Dissociation of an acid through pH
In natural systems what anion dominates?
Biocarbonate HCO3-
Bio-concentration:
Bioconcentration is the accumulation of a chemical or pollutant in an organism compared to the surrounding water.
The dead sea is made of ____ instead of NaCl
Bromine concentration
Mobility of NO3- is much higher than NH4- because
CEC >> AEC
Which metals are highly toxic?
Cd, Mn, Pb, Hg, As, Po
Classification of metals based on
Chemical behavior -Type A, Type B and Transition metals
F.A.C.E stands for:
Free Air CO2 Enrichment
China Phosphorus
In 2006, highest concentrations and since then large scale declines in lake phosphorus concentration
Bio-magnification
Indicate an increase in the concentration as you move up the food chain
Which metals are macro-nutrients for plants?
K+, Na+, Ca2+, Mg2+
Ammonium in soils:
Major sources of NH4: major fertilizer, mineralization of org. matter, urea Cold conditions: chemical reactions and plant uptake slow runoff -high ammonia loads in wintertime -can volatilize into the atmosphere as NH3 which is major air pollutant
Most toxic form of mercury is
MeHg
Redox Chain: Oxygen then Nitrate then Sulfer then ___
Methane
Which metals are micro-nutrients?
Mn2+, Co2+, Zn2+, Fe2+
Major anions that can neutralize acidity
OH- HCO3- 2CO3 2- (help buffer system)
Biomass degradation (aerobic respiration)
This is a reverse example of photosynthesis -Highly exogenic
Fish at the top of the food chain (ex. Tuna) have higher Mercury content. True or False
True
Pourbaix diagram: whats on y and x axis
Y axis: have redox conditions X axis: pH
Is high alkalinity good for lakes?
Yes because they now have the ability to buffer the acidity If you have high alkalinity pH will not drop
As(V) dominant in ___ environment
aerobic
As(3) dominant in ___ environment
anoxic
NOx is a major ___ source
anthropogentic
Many toxic metals ___ and ____
bio-accumulate and bio-magnify
Complexation by Org. Matter involves
both covalent and ionic bonds
In Bangladesh, 30 million people drink well waters that ____
contain elevated arsenic concentrations (from geologic sources)
NO3- subject to denitrification forms
forms N2O (gaseous) + N2 (gaseous)
USA is hotspot in mercury pollution because
have very productive forests
CO2 increase causes *CO2 fertilization effect*
higher rate of photosynthesis
Nitrogen is important where?
in DNA chrlorophyll in plants & protiens
Bio-accumulation:
is the process by which contaminants build up in individual organisms
Organisms near the river outlet have ____
more bio-accumulation and more cadmium than near the open ocean Cadmium and Salinity have an inverse relationship
In water free (metal) ions are ___
not free, they are normally hydrated forming "aquo" complexes
In most natural water, other ___ act as ___ forming __
other dissolved substances act as ligands, forming new complex with central ion
Alkalinity is
the ability of water to neutralize acidity
Assume ____ in single variable diagrams (aqueous chemistry)
thermodynamic equilibrium (vs. kinetics that are more important in atmospheric chemistry) b/c water is densier
Over three quarters of our lakes have ___
too high nutrients in them (phosphorus is one of the driving nutrients)
Assimilation
uptake of ammonium then plants synthesis and becomes org. carbon
