- 2.4 – micropollutants

- 2.4 –

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Micropollutants

MICROPOLLUTANTSChapter 3.8, 3.9 & 5.8 in Chapman et al.

Diederik Rousseau

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Diederik RousseauTamara Avellan

Peter Kelderman

Online Module on Water Quality Assessment

CONTENTS

1. Types and origins of micropollutants

a) Inorganic: Heavy metals

b) Organic: PCB, PAH, Hormones and EDC, PPCPs & pesticides

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PPCPs & pesticides

2. Bioaccumulation

3. Aquatic Ecotoxicology

4. Micropollutants in aquatic sediments

What are Micropollutants?

Inorganic and organic substances that can affect the environment in a

negative way even at very low concentrations, in the range of micro,

nano, pico-grams (µg/L (10-6 g/L); ng/L (10-9 g/L); pg/L (10-12 g/L))

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Basically two types:

• “Heavy metals” (specific density > 4.5 kg/L) such as Cd, Pb, Cu, or

“trace metals” (Fe, Mn,..) and metalloids (As, V,..). These terms often

used as synonyms

• Organic micropollutants (DDT, PCBs,..)

Anthropogenic Sources of trace metals

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Toxicity: The case of Cadmium in Japan

http://www.kanazawa-med.ac.jp/~pubhealt/cadmium2/itaiitai-e/itai04.html

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• Itai-itai disease was found in the Cd polluted Jinzu River• Since the 1950's by the effort of inhabitants and Dr. Hagino• Itai-itai disease was officially recognized in 1968 as the first disease induced

by environmental pollution in Japan

Toxicity: The case of Hg in Manado Bay, Indonesia

• Gold mining with Hg extraction

• Discharge of Hg from rivers into bay

• Deposition and accumulation in

downstream locations

• Bioaccumulation in bivalves

Source: Lasut et al. (2005), Coastal Marine Science

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Source: Lasut et al. (2005), Coastal Marine Science

Metal speciation:depends partly on redox potential (Eh, Volts), and pH

• Precipitation of PbO2 at high pH and high Eh (“aerobic conditions”)

• Low-neutral pH, high Eh: as Pb2+

• Solid Pb at low Eh (“anaerobic”for

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• Solid Pb at low Eh (“anaerobic”foralmost all pH values)

• For intermediate Eh various dissolved species exist; at high pH and enough carbonate (“hardness”) also PbCO3 ↓

• Will influence availability for organisms; ionic form most toxic!

Organics

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Organics – PAHs

PAHs (polycyclic aromatic hydrocarbons): 2-8 fused benzene rings.

May also contain S, O, N: are then called heterocyclic PAHs.

From combustion processes (automobiles, coal, oil, stacks..)

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PAHs are hard to degrade and carcinogenic at low concentrations.

PAHs have large tendency to accumulate in sediments and in the

aquatic food chain.

Polychlorinated Biphenyls (PCBs) in fish

Built up by two benzene rings + Clsubstitutions � more than 200 different PCB components (e.g. PCB- 28)

PCBs extremely stable; therefore widely used as thermal and electric insulators; in plastics, paints

PCBs have large tendency to be

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PCBs have large tendency to be accumulated in sediments and in the food chain

Already at extremely low concentrations, there may be adverse effects on humans and aquatic life (“pseudo-sex hormone”)

Partial global ban in the 1980s; however still measurable concentrations (non-degradable).

Hormones

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Hormones

13http://www.mindfully.org/Pesticide/Alligators-Apopka-PBS2jun98.htm

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• Application rates

• Disposal of containers

• Washing of equipment

• Timing of application

Pesticide residues

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• Timing of application

Agrochemicals in small scale farming in Ghana

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Increased concentrations in wet season � effect of runoff

Source: Ntow (2008), PhD Thesis UNESCO-IHE

CONTENTS

1. Types and origin of micropollutants

a) Inorganic: Heavy metals

b) Organic: PCB, PAH, Hormones and EDC, PPCPs & pesticides

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PPCPs & pesticides

2. Bioaccumulation

3. Aquatic Ecotoxicology

4. Micropollutants in aquatic sediments

Bioaccumulation:

increase in concentration of a pollutant from the environment to

the first organism in a food chain (i.e. in tissues)

Biomagnification:

Definitions

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Biomagnification:

increase in concentration of a pollutant from one link in a food

chain to another

(Food chain/web: see Unit 5)

Bioaccumulation/magnification Process

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CONTENTS

1. Types and origin of micropollutants

a) Inorganic: Heavy metals

b) Organic: PCB, PAH, Hormones and EDC, PPCPs & pesticides

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PPCPs & pesticides

2. Bioaccumulation

3. Aquatic Ecotoxicology

4. Micropollutants in aquatic sediments

Start of Ecotoxicology � triggered by effects of DDT and

related organochlorine pesticides on birds and mammals

1962 - Rachel Carson: "Silent Spring”

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Carson R (1962) Silent Spring. Houghton Mifflin Company, New York

Toxicology: science of poisons

ParacelsusA.P.T.B. von Hohenheim

1493 – 1541(Salzburg)

“Every chemical is poisonous,

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“Every chemical is poisonous, dose determines the effect”

(“Alle Ding sind Gifft. Allein die Dosis macht daß ein Ding kein

Gifft ist”)

The dose-response-relationship

� the basis of (eco)toxicology

Survival, growth or other measure of performance

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NOEC LC50 or LD50

(log) concentration

Ecotoxicological assessment: two parts

RISK

=

EXPOSURE

X

TOXICITY

24Source: Schwarzenbach et al. (2006)

Toxicological endpoints derived from dose-

response relationships

LC50: median lethal concentration

EC50: concentration causing 50% effect

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50

NOEC: no observed effect concentration

These endpoints provide measure of toxicity

� Enable comparison of toxic potency of chemicals

� The lower the endpoint value, the more toxic the chemical

Chemical LD50

botulin-toxin A 0.0005

diphtheria-toxin 0.3

2,3,7,8-TCDD 1

tetrodotoxin 15

strychnin 500

aflatoxin 600

aldicarb 900

nicotin 1 000

Acute oral toxicity of selected chemicalsexpressed LD50

(lethal dose 50%) in µg per kg body weight

nicotin 1 000

Methyl mercury 1 000

parathion 3 000

HCN 10 000

thallium 10 000

DDT 113 000

Salt (NaCl) 4 000 000

Water (H2O) 160 000 000

The most standardized

aquatic test protocol

Test species Daphnia magna

Test duration 48 hTest system Static, no foodEndpoint MortalityParameter LC single compound

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Parameter LC50 single compound

- toxicity tests on (extract of) environmental sample

- performed in the laboratory under controlled conditions

(may also be performed in the field)

- endpoints: survival, behaviour, growth, reproduction, etc.

Bioassays

Examples:

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Examples:

• Bacterial tests (enzyme inhibition), e.g. ECHA test; metal-specific tests

• Microtox, using luminescent bacteria (Vibro fischeri)

• Algae (e.g. algal tox kit)

• Daphnids and other crustaceans, e.g. Daphtox, Rototox, Artoxkit)

Examples of toxkits used as bioassays

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CONTENTS

1. Types and origin of micropollutants

a) Inorganic: Heavy metals

b) Organic: PCB, PAH, Hormones and EDC, PPCPs & pesticides

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PPCPs & pesticides

2. Bioaccumulation

3. Aquatic Ecotoxicology

4. Micropollutants in aquatic sediments

WHY MONITORING AQUATIC SEDIMENTS?

• Sediments may be important “sinks” or “sources” of pollutants, e.g. of phosphorus (P) (Lake water balance � P mass balance: “In” –”out” terms � “Sediment P accumulation; may be > 80% ! (or P release)

• They may release pollutants (e.g. heavy metals) under certainconditions (pH, redox potential, salinity..)

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conditions (pH, redox potential, salinity..)

• Sediments can give “history” of pollution

• Often slower (bio) degradation of pollutants, especially in anaerobicsediments

• Many bottom-dwelling organisms (fish, cockles) and rooted plants.

AQUATIC SEDIMENTS

Allogenic (or allochthonous) material, from outsidethe system (�)

Aquatic sediments complex mixture of minerals + organic compounds + bound ions:

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the system (�)

• Endogenic minerals, from processes in the water system (sedimentation of carbonates, algae, etc.) (�)

• Authigenic (or authochtonous) minerals, by physico-chemical and microbiological processes in the sediment

MICROPOLLUTANTS IN AQUATIC SEDIMENTS

Micropollutants large tendency to be adsorbed onto suspended matter and sediments

Expressed with: partition coefficient P (L/kg) :

P = µµµµg micropollutant/kg particulate matter, divided by the µµµµg/L present in the water phase

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µµµµg/L present in the water phase

Heavy metals 104 – 105 L/kgBenzo(a)pyrene (PAH) 104 - 105

PCBs 105 – 106

Methoxychlor 104

Naphthalene 103

Example: fate of dissolved heavy metals in the Dutch IJssel Lake

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> 50% can be adsorbed onto particulate matter and thus be “lost” from the water.

THE FATE OF HEAVY METALS IN SEDIMENTS

No irreversibly bonding to the sediment; remobilisation by:

• Elevated salinity (e.g. in estuaries; Na+ replaces metal ions)

• For lower pH (higher [H+] which replaces metal ions)

• Redox potential Eh (“aerobic/anaerobic” conditions; slide 8):

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• Redox potential Eh (“aerobic/anaerobic” conditions; slide 8):- Low Eh : precipitation of HMs as metal sulphides; - Aerobic conditions: S2- � SO4

2- ; more soluble � release HMs

• Biological and microbiological activities and conversions

• Sediment resuspension, due to waves and currents; dredging (see bullet point 3)

Minamata case, Japan:

• Industrial mercury pollution; many people were affected or even killed

• Sediments: up to 2000 mg Hg/kg (Standards: ~ 2 mg/kg)

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(Standards: ~ 2 mg/kg)

• Methyl mercury uptake by fish � men

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Degradation product of DDT (also toxic) in sediments of Lake Geneva (France/Switzerland)

SEDIMENT GRAIN SIZE

• Highest micropollutants contents on smallest sediment fraction (high

specific surface area)

Cadmium content on

river Rhine sediment

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• By waves and currents, especially this “fine” sediment is transported to the

deeper areas � “sedimentation basins” of polluted sediments !

“sand” “silt” “clay”

>63 µm……… <63; > 2µm …….<2 µm

The role of sediments in water Qualty

Cu and Pb in Lake Ontario sediment profiles, 1985

Decrease due to recent sanitation measures

SEDIMENT CORES AS “HISTORICAL CALENDARS”

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Background; increase in 1900s (industrialization)

Hg (ppm = mg/kg)

Top layer: 1960/65 sohardly any decrease yet(no abatement measures)

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Background concentration,

before around 1800

Sediment depth = “history”

“Age” determined with e.g. radioactive dating (210Pb or 137Cs)

RADIOACTIVE SEDIMENT DATING

Effect of nuclear tests in the 1960s

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• 210Pb (half life = 22 years)• Chernobyl accident (1986): 137Cs (half life = 30 years)

Overall

In the Netherlands, four sediment quality classes: heavy metals and organic micropollutants (mg/kg = ppm) :• class 1 +2 can be dumped into the environment • class 3+4 sediments: stored and/or cleaned-up

MANAGEMENT POLLUTED SEDIMENTS

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assessment:

“worst case”

E.g. Cu in class 4 -->

whole sediment

in class 4 !

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Sediment research in a Dutch lake, using “grab sampler” and “core sampler”

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