PLSC170 Exam 3

urban areas

higher density = lower carbon emission by scale

cities

higher density requires more environmental service for human communities

urban soil

all soils in areas with an established population in the built environment and have a high likelihood of soil alteration

urban rural gradient

the spatial variation of environmental factors in relation to the intensity of urbanization

parcelization of land and management differences

leads to high heterogeneity in landscape composition

standardization of development and city landscapes

leads to increase in homogenization

homogenization

process by which different places resemble those found in other areas

indirect anthropogenic effects

• altered temperature and soil moisture regimes

• elevated CO₂

• pollution stress

• non-native species introductions

• atmospheric deposition

direct anthropogenic effects

• soil physical disturbances

• burial and coverage of soil

urban ecosystem inputs and outputs

energy, food, water, air → heat, liquid, and solid waste, air pollution

unsustainable urban ecosystem

when a city is beyond the carrying capacity of local resources

enters soil from atmosphere

precipitation, nitrogen deposition, pollution

leaves soil to atmosphere

CO₂ respiration

runoff from urban soils

pollution, nitrogen

leaches into urban soil

pollution, nitrogen

physical characteristics of urban soil

• higher compaction → lower permeability

• higher temperature

chemical and biological characteristics of urban soil

• increase of pH (from cation deposition → variation in soil microbial communities

• increase of heavy metals and pollutants → pB, solvents, and waste near urban centers

• potential increase in C storage → higher biomass growth, especially in arid regions

bulk density response

≥ 1.4 g/cc inhibits root growth

• leads to porosity → microbial community → nutrient sequestration → plant establishmnet and again to bulk density

Liebig’s Law of the Minimum

plant growth is controlled by the mineral nutrient in shortest supply

urban environments are rich in what mineral nutrients?

N, P, and Ca

soil functional responses

increased invasive vegetation have reduced carbon accumulation, Ca and Mg increases with invasion (increased soil pH making less nutrients available)

urban soil response to replacement with highly managed landscapes

• reduced CH₄ capture

• reduced C storage

• increased BD

urban soil response to atmospheric deposition

• higher N deposition than rural soils

• Pb greater next to buildings due to interception

• higher BC in soil under trees due to interception

urban soil response to increased atmospheric temperature

• increased presence of invasive subtropic soil organisms

• increased decomposition of SOM, greater loss of CO₂

• decreased soil moisture and water uptake by trees → less photosynthesis but increasing root growth as a response

ecosystem services of urban soils

1. regulation services

2. provisioning services

3. cultural services

4. supporting services

regulation services

storage of soil carbon and mitigation of greenhouse gases and urban outputs

provisioning services

food production and supporting structures

cultural services

support of public green spaces used for community recreation, aesthetics, and spiritual value

supporting services

soil formation, nutrient cycling, capture and storage of pollutants

Brown Infrastructure for Urban Sustainability

the blue-green infrastructure relies on understanding and adapting to brown infrastructure within the urban landscape

steps to assessing urban soil remediaton

1. determine the current status of urban soil health

2. identify current and long-term urban soil issues and community needs

3. provide a framework to move forward

site assessment

• investigate site history

• identify proximity to impairments such as roads and buildings

• assess soil health through sampling surfaces for nutrients and structure

• identify issues

challenges of remediation

• effective soil volume may be restricted

• water availability is significantly reduced

• urban soils are highly heterogenous

BMPs to reduce bioavailability of soil Pb

• adding organic amendments to bind Pb

• maintaining pH near neutrality

• providing adequate plant nutrients to reduce uptake of Pb

restoring urban soils in highly managed areas

1. apply organic amendments to improve soil material

2. mix contaminated soil with non polluted soil to dilute pollutants, reduce plant uptake and skin contact

3. recover nutrients from urban outputs to use as fertilizer

4. get rid of turf and work within the boundaries of the climate

BMP for urban soil management

• remove debris

• keep soil covered → reduce erosion, increase water retention, and temperature control

linear economy

take → make → use → dispose

circular economy

make → use → collect → transform → reuse → make

• more efficient use and reuse of materials

• many by-products and residuals contain carbon and nutrients

• other constituents can be a concern limiting reuse

clean water

springs, wells, purified water, city water

greywater

used water from sinks, showers, baths, laundry

blackwater

water from toilets or containing hash chemicals

physical wastewater pollutants

sediments, grit, microplastics, debris

chemical wastewater pollutants

nutrients, organic chemicals, metals

biological wastewater pollutants

pathogenic bacteria, viruses, protozoa

wastewater treatment

• rural → on-site septic (can be source of biological pollutants, 20% of U.S.)

• urban → wastewater treatment plants

water reuse options

• irrigation

• industrial process water

• toilet flushing

• concrete mixing or construction

• environmental restoration

biosolids

• composed of organic material

• characteristics depend on properties of raw sewage, wastewater treatment processes, and biosolids treatment

environmental issues of biosolids

• trace elements and pathogens

• organic contaminants

• microplastics

• nanoparticles

• PFAS (forever chemicals)

animal manures

most common use is beneficial soil amendmnet

industrial wastes

• created by factories, mills, mines, and other industrial activities

• can be liquid of solid

• may include hazardous waste (highly regulated in US)

• sometimes mixed with municipal waste

hazardous wastes

• classified by ignitability, reactivity, corrosivity, toxicity

• regulated in U.S. under RCRA

open dumps

• prevalent in low-income countries

• anything can be deposited

• no protection of surface or groundwater

• attract animals and birds

• may allow open burning

• prohibited in U.S.

controlled landfills

• controlled access limits hazardous material disposal

• no open burning

• covered daily to reduce access to birds and animals

• gas and leachate not collected or treated

• relies on natural attenuation

sanitary landfills

• most complex and expensive

• impermeable layers or liners are placed prior to disposal

• pipes and pumps collect leachate for treatment

• capped with clay, soil, or geomembrane

incineration

• most common waste to energy method

• popular in land-limited, high-income countries

• common for medical and hazardous wastes

• can be used to manage animal mortalities

• reduce volume significantly

anaerobic digestion

• reduces waste to landfills

• reduce methane emissions

• produces biogas that can reduce odors

• expensive to build and operate

waste to energy

• avoids landfilling ← biggest benefit

• metals can be recovered

• high CO₂ emissions

• could disincentivize recycling

• usually not economical

land application of residuals

• recycling of organic matter and nutrients

• improper management can lead to environmental degradation, crop damage, or conflicts with the public

land application sources

manures, biosolids, composts, digestates

land application rate

• laboratory analysis gives actual nutrient content

• nutrients might not be balanced with crop needs

• rates may be limited due to soil P enrichment

• not all nitrogen will be available to crops in application year

land application methods

• surface applications susceptible to more nutrient losses and odors

• adding tillage conserves nutrients but disturbs soil

• low-disturbance subsurface application available for liquids only

land application timing

• best nutrient uptake when applied near crop planting

• avoid application to frozen or snow-covered soils

• lower nutrient losses with longer time between application and rainfall

land application barriers - odors

• many residuals smell

• consider downwind neighbors

• apply when wind speeds are lower

• incorporate

land application barriers - pathogens

• materials may contain animal or human pathogens

• some materials should not be applied to crops for direct human consumption

• regulated for biosolids

land application barriers - trace elements

• concentrations depend on the source

• concerns with plant uptake and impact on soil biota

• loading in biosolids is regulated

land application barriers - other contaminants

• nanoparticles

• personal care products

• antibiotics

• hormones

• PFAS

dairy waste management

• methane digester turns food waste and dairy manure into biogas to power farm and nearby residences

• installed solid-liquid separator to improve digester efficiency

• solids composted and 60% sold off-site as fertilizer

• liquids reused as wash water or spray irrigated onto the fields

soil contamination

chemicals (either inorganic or organic) in a soil that pose a risk to human health and the environment

xenobiotics

substances foreign to an ecosystem

anthropogenic

something produced by humans

DNAPL

dense, non-aqueous phase liquid

• heavier than water and does not mix with water

• example: chlorinated compounds

LNAPL

• light, non-aqueous phase liquid

• example: petroleum products

inorganic contaminants

Cr, Ni, Cu, Zn, Cd, Hg, Pb, As, Se, Rn, U

BP Deepwater Horizon

• 210,000,000 gallons of oil spilled from April 20, 2010 to September 19, 2010

solubility

inversely proportional to hydrophobicity

how do contaminants move through soil?

• leaking tanks of DNAPL and LNAPL leak into vadose zone

• DNAPL continues to mvoe into saturated zone in the direction of groundwater flow

• flows into fractured bedrock

in situ

remediate the contaminate in place

ex situ

processes remove the contaminate for treatment

pump & treat

• widley used

• groundwater treated ex situ

• not very efficient if the contaminant is not soluble in water, most be continued for years or decades

dig & haul

• removal of contaminated soil, usually when contaminated with inorganic compounds

• does not actually remediate soil

• expensive, but commonly done for liability reasons

air spaging and soil vapor extraction

• less common

• used if contaminant is volatile

bioremediation

when microbes are added to the soil, they use the contaminants as an energy source

aerobic bioremediation

oxygen is terminal electron accepter

anaerobic bioremediation

alternate terminal electron accepter

cometabolism

microbes break down contaminants without gaining any benefit

factors affecting bioremediation

• contaminant concentrations

• contaminant bioavailability

• site characteristics (pH, redox, nutrients, temperature, water content)

bioaugmentation

addition of microbes to soil

biostimulation

addition of amendments (air, organic substances, electron donors, nutrients)

In situ Chemical Oxidation (ISCO)

• oxidants injected into aquifer

• improve mixing by recirculating between wells

permeable reactive barriers

treat contaminated groundwater as it flows through reactive materials, capturing and breaking down pollutants

monitored natural attenuation

• microbes present onsite remove contaminants

• dilution

• abiotic reactions

• absorption

• volatilization

phytoremediation

process that uses plants to clean up contaminated air, soil, and water by absorbing, degrading, or stabilizing pollutants

phytostabilization

stabilize contaminated soil with plants

phytoextraction

process that uses certain plants to absorb contaminants, particularly heavy metals, from soil or water and concentrate them in their biomass

phytotransformation and phytodegredation process

• phase I: transformation/functionalization/modification

• phase II: conjugation

• phase III: compartmentalization/sequestration

rhizodegredation

plants assist in breaking down pollutants in the soil around their roots with microorganisms

phytovolatilization

pollutants enter plant through roots and escape through stomata and cuticle

pH of natural rain water

• not neutral — 5.6 to 5.7

• because rainwater dissolves CO₂ forming carbonic acid

• acid rain when pH < 5.6

acid deposition

transfer of strong acids and acid forming substances from the atmosphere to the surface of the earth