Environmental Geoscience TEST 1

unimelb

Stakeholders

Communitiy members, scientists, local government, industry

four areas of environmental science

systems, processes & conditions, change, technology

examples of human action

land clearance, draining coastal lowlands, open pit mining, fracking, carbon capture & storage

how to use rock record as archive

lithological, micropaleontological, and chemical variations in sediments

how to define anthropocene

increase in co2 concentration, introduction of engineered material, increase in sedimentation & nutrient levels, eutrophication, land management changes

catchment

the area around a body of water that feeds it through runoff an other processes

where people want to live

the coast

how are catchments defined

topography: with ridges as boundaries

types of maps used for catchment management

topography, geologic, soil, land use

input = output

steady state

input NO output

nonsteady state

why soils are integral

provide growth substrate, nutrients and water, form physical barrier for water erosion and runoff

how soils can be diminished

erosion events or degradation over time

Soil forming factors

1. Parent material

2. climate

3. organisms

4. topography

5. time

Major soil processes

1. Decomposition and humification of organic matter

2. Physical weathering

3. chemical weathering

4. leaching

5. translocation

6. capillary action

Soil layers

O horizon: Organic matter, decomposed at depth

A/E horizon: Amalgamation of ricks and org matter, eluvial and subject to leaching, chemical weathering, and translocation. Porous.

B horizon: Illuvial, enriched and dense

C horizon: weathered parent material

R horizon: regolith (unweathered)

Podzol

boreal/cool climates, with sandy parent material. well-drained.

Latosols

Red! in permanently wet and hot environments with intense chemical weathering. can be very thick and has indistinct layering

Laterites

in hot areas with wet/dry seasonality, Very strong leaching, dry season capillary action, Fe and Al precipitation.

Types of erosion

1. rill erosion (<30cm deep, caused by rain)

2. sheet erosion (large patches, caused by rain)

3. Gully erosion (>50cm deep, erosion endmember)

4. tunnel erosion (removal of subsoil)

5. wind erosion (in unvegetated areas, turbidity rules apply)

Soil salinization

when land is cleared, native vegetation is removed. This causes greater runoff and erosion, decreased evapotranspiration, and the rise of the water table. Higher groundwater evaporates and causes soil to become salty because of the ions.

how to mitigate soil salinization

1. terracing

2. contour farming

3. shelter belts

4. riparian (uncultivated) wetlands

Estuary

mixing zone between river freshwater and ocean saltwater

Eutrophication

enhanced nutrient enrichment of a body of water—usually nitrogren

consequences of estuarine eutrophication

1. boom and bust algal patterns

2. periods of anoxia

3. toxic algal blooms (smelly!)

types of estuaries

1. wave/tide dominated delta

2. wave/tide dominated estuary

3. coastal lagoon

4. strandplains/tidal flats

where wave-dominated estuaries are dominant

south of QL: due to decreased rainfall (input) and lower tidal range

where tide-dominated estuaries are dominant

Northern tropical AU: because of high rainfall

characteristics of wave-dominated estuaries

internal circulation, limited exchange, episodic inflow, sandbars, long residence time, high salinity

characteristics of tide-dominated estuaries

high river inflow, tidal flow, tidal (flats, creeks, and channels), mangrove belts, seasonal water residence time

types of estuarine producers

1. Phytoplankton (floats)

2. Microbenthic algae (on sediment)

3. submerged aquatic vegetation (grasses)

redfield ratio

106C:16N:1P

Highest energy yielding oxidant used by surface sediment bacteria

oxygen

other oxidants

nitrate, Fe-Mg oxide, sulfate

role of sediments in oxidation

oxygen sink, can deplete bottom water

processes that limit efficiency of recycling N and P

1. Denitrification (changes to nonreactive N2 gas)

2. Phosphorus adsorption by Fe oxides (binds P to sediment)

St. George

deep, phytoplankton dominant, no sea grass, no mixing could lead to anoxia

Wilson Inlet

middling depth, seasonal dominance of phytoplankton in winter and microbenthic algae in summer, some seagrass, light penetration is a potential issue

Lake Wollumboola

shallow, macrophyte cover. vulnerable to boom and bust cycles, N and O are variable

Torbay Inlet

shallow with low light penetration (tannins). high in dissolved nutrients, prone to toxic algae

interglacial period

high sea level, not much land in between coastline and elevated plain, inner shelf deposition of Fe-oxide, intensive reduction of Fe-oxide and sulfates, formation of pyrite

glacial period

low sea level, coastal flats/plain, subaerial erosion, and deep fluvial incisions, pyrite oxidation and Fe oxide formation, increased acidity of water

Estuarine mixing zones

are a net sink for iron minerals, neutralize hydrolised ions, coagulates Fe-oxyhydroxides and humic acids…

pyrite

FeS2, made of iron and sulfates. Formed during interglacial periods

Iron (Fe) oxides

great at adsorbing heavy metals (arsenic, selenium), formed in glacial periods, associated with acidification

Bay of Bengal

retreating water causes oxidation of sediment, leading to heavy metal contamination. Recommendation to allow groundwater to become fully oxidized before use (metals will precipitate out)

Actual Acid Sulfate Soil

highly acidic soil horizons from oxidation, pH less than 4

how to determine AASS

pH less than 4

electrical conductivity (more iron = more conductive)

in situ redox potential (Eh/mV)

presence of pyrite (can determine by adding H2O2 and watching results of reaction—color change)

Baker Inlet

acidifying soils through oxidation due to pyrite exposure can kill local vegetation—which contaminates groundwater and causes increased greenhouse emissions from decomposing organic matter. Recommendation was to re-flood the drained area.

O horizon

Organic matter, decomposed at depth

A/E horizon

Amalgamation of ricks and org matter, eluvial and subject to leaching, chemical weathering, and translocation. Porous.

B horizon

Illuvial, enriched and dense

C horizon

weathered parent material

R horizon

regolith (unweathered)

rill erosion

<30cm deep, caused by rain

sheet erosion

large patches, caused by rain

Gully erosion

>50cm deep, erosion endmember

tunnel erosion

removal of subsoil

wind erosion

in unvegetated areas, turbidity rules apply

denitrification

changes to nonreactive N2 gas

phosphorus adsorption by Fe oxides

binds P to sediment