Lecture notes Environmental Chemistry and Health (GEO3-2119)
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Course
Environmental Chemistry and Health (GEO32119)
Institution
Universiteit Utrecht (UU)
This document contains the notes from all lectures that were given in the course Environmental Chemistry and Health about the three subjects; chemistry, toxicology and epidemiology in the environment.
Lecture 1
3 parts: environmental chemistry (sources, reactions, transport and fate of
chemical species in air, water and soil) - toxicology (harmful effects of
chemical, physical and biological agents on living organisms) - epidemiology
(branch of epidemiology concerned with determining how environmental
exposures impact human health).
Case study: a problem related to environmental chemistry and health → you
have to formulate an advice for humans → it is a self-study (have to do it by
yourself) → 2 components: output presentation (15%) and written report (35%).
Chemicals in the environment: from anthropogenic and
geogenic or natural sources → the contaminants will
be cycling in the environment → these compartments
are interlinked (picture left).
→ important to understand the transportation of
chemicals to understand its impact on health.
Behaviour and risk of chemicals depends on the
chemical speciation.
- Speciation of an element: distribution of an
element amongst defined chemical species in a system.
- Chemical species: a specific form of a chemical
element, defined as its complex structure or oxidation state.
- Chemical speciation helps understand mobility, bioavailability and toxicity of substances.
→ examples: chromium (Cr) has different oxidation states → most
common: (1) Cr(III) as cation Cr3+, (2) Cr(VI) as anion chromate (CrO42-) →
due to different nature of the charge the chromium species behave
different in the environment and pose different risks.
→ example: mercury (Hg) is a highly toxic heavy metal → especially organo-mercury compounds
bioaccumulate in aquatic environments → consumption of fish can cause mercury toxicity →
BUT, metallic and inorganic mercury species are less dangerous → FEX. mercury (Hg0) for tooth
fillings and jewelry containing mineral cinnabar (HgS) →
because they are poorly soluble and absorbed by a much
smaller extent.
Conclusion: chemical speciation of substances in the
environment is (a) complex and (b) the result of many
simultaneous physical, chemical
and biological processes.
Chemical speciation of metals:
picture right → metals behave
differently at different stages.
Uptake = how metal ions enter the cellular material.
Absorption = adhesion of metal ions onto a surface.
Dissociation = a compound that breaks into its component ions.
Complexation = a metal atom or ion bonded to one or more ligands (ions or molecules that
contain one or more pairs of electrons that can be shared with FEX. metals).
Precipitation = when cations and anions in aqueous solution combine to form an insoluble ionic
solid.
,Changes in speciation can be described through 2 different approaches:
1. Thermodynamics: for reactions that are at equilibrium ∆G=0 (Gabbs free energy) →
speciation can be described using mass law and mass balance equations.
a. at equilibrium: rateforward = ratereverse
𝑐 𝑑
[𝐶] [𝐷]
b. mass law equation: Kw = [OH-][H+] = 10-14 → aA + bB ↔ cC + dD → K = 𝑎 𝑏
[𝐴] [𝐵]
c. mass balance equation: based on conservation of matter = sum of all species of a
certain element must be equal to the amount of the element delivered to the
solution → include all relevant species, they add up to the total amount in the
system.
→ example of mass law equation.
2. Kinetic description: rate law
equations (A → B) → zero, first
and second order (pictures
right).
In an environmental system, a single
element
participates in many reactions
that form a complex reaction
network → free concentration
plays a central role in
understanding speciation in
environmental systems → most
equilibrium reactions involve the
free concentration → 2 ways of
calculating.
Reactive soil surfaces: in the environment we find reactive solids with a large surface area,
with the ability to bind solutes → FEX. organic matter, clay and metal(hydr)oxides.
Absorption: solution with a high affinity for surfaces are often primarily absorbed →
sorption isotherms describe the equilibrium between the absorbed concentration (Q in
mol/kg) and the solution concentration (C in mol/L) → for transport, sorption is a
process of major importance → retardation = the velocity of solute in water → the velocity of
how much a solute is moving slower → how much slower a solute is going (factor larger than 1).
Pictures below: explain absorption and retardation.
, Bioavailability = the degree to which chemicals may be absorbed or metabolised by human or
ecological receptors or are available for interaction with biological systems → related to
chemical speciation → not all species of a certain chemical can be taken up → chemical
speciation helps understand the mobility, bioavailability and toxicity of substances.
→ many organisms predominantly take up molecules and ions from the aqueous phase →
assumption: only dissolved species are directly bioavailable, BUT adsorption of the dissolved
species/solutes may occur → however, if sorption equilibrium is preserved, the solution
concentration will be replenished through desorption and are referred to as potentially
bioavailable.
Risk evaluation environmental contamination: to evaluate the necessity to remediate
environmental contamination, various risks are evaluated: (a) threat to human health, (b) threat
to ecosystem health, (c) threat of spreading → are influenced by speciation.
→ the national institute for public health and the environment (RIVM) develops methods, models
and instruments to perform risk assessments of contaminated sites.
Soil contamination in NL: 250.000 locations are contaminated and 1518 require urgent action →
pressure on (a) spatial use, (b) below ground building activities, (c) heat-cold storage in the
subsurface, (d) groundwater use for drinking water.
Soil texture influences metal toxicity → clay has a higher cation exchange capacity (CEC) and
binds Cu more strongly → less available to be taken up by the plant.
→ the pH is also important → at a low pH, the grass suffers from more copper than at a high pH
(because there is more copper available for the plant to take up, so growth decreases over time).
Dutch regulation: the concepts of chemical speciation and bioavailability are incorporated in
Dutch regulation on environmental contamination, BUT to a limited extent
→ examples: (a) correction of the intervention value for lutum and organic matter content of a
soil, (b) distinction between chromium (III) and chromium (VI), (c) distinction between organic
and inorganic mercury.
→ Dutch regulation is conservative → they avoid risks (on the safe side), it is based on “total
amounts” rather than “reactive amounts” or “potentially available amounts” of contaminants.
→ drawback: potentially substantial costs when there are no actual threat risks.
Lecture 2
Examples of toxicology: PFAS chemicals which contaminate plastic food containers → firponil in
eggs → chromium 6 in paint which was used without protection → crumb rubber in soccer
fields, but people, especially children, received too much chemicals from this and could get
cancer → high levels in carcinogen in paracetamol → microplastics form a
health risk → steel industry causes high pollution.
Toxicology = study of adverse effects of chemical, physical or biological
agents on living organisms → exposure to toxic chemicals → is it safe to use
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