Wetland and Soil Chemistry for GHG Emissions Key Words: Wetland; Soil; Greenhouse gases; Dry and wet deposition; Sewage treatment; Life cycle assessment Description: Wetland breeds varied plants, animals and microorganisms. The crisscrossed roots of plants and soil colloid offer a perfect condition for sedimentation. Then organics, trace elements, nitrogenous substances, phosphorus-­‐containing compound and even heavy metals could be removed in certain ways with less ecological effects. Artificial wetland is generally constructed to treat wastewater. Wastewater treatment processes are identified as important sources of world GHGs (greenhouse gases) budgets. During the aerobic biological treatment processes, organic carbon is transferred into carbon dioxide through anabolism, catabolism and biomineralization by aerobic microorganisms. In the processes of anaerobic biological treatment, methanogenus would combine with acetogen and fermentative bacterium to generate methane. Nitrous oxide as an emerging GHG produced from biological nitrogen removal treatment is mainly due to incomplete nitrification and denitrification processes. To evaluate the environmental burdens associated with a product, process, or activity from cradle to grave, life cycle assessment (LCA) is applied by identifying, quantifying and assessing the impact of the utilized energy, materials and the wastes released to the environment. LCA could identify and evaluate opportunities for environmental improvements to guide government policy, strategic planning, marketing, consumer education, process improvement, product design, eco-­‐labeling and consumer education programs throughout the world. Pictures: Fig. 1. Gas sampling of lab-­‐scale subsurface flow constructed wetland Fig. 2 Photo of on-­‐site gas sampling in wastewater treatment plant Fig. 3 Lab-­‐scale aquaponic systems 2174
Environ Earth Sci (2013) 68:2171–2180
NH4+
Amo NH OH
2
N 2O
NOH Hao
NO3- Nar
iNor
N 2O
NO2- Nor
NO2·NHOH
Fig. 2 Scheme
denitrification
NO3N2O
NO 2-
Nir
of
relevant
NO
N2O
Nr
N2 O
production
Nos
pathways
N2
in
Fig. 1 Scheme of relevant N2O production pathways in nitrification
the
cell while N2O will be released using NO2- as
Fig. 4 Scheme of relevant N2O production pathways in AOB’s
nitrification an electron acceptor to avoid the accumulation of NO2- in
the system. In nitrifier denitrification, N2O is an intermediate product during the reduction of NO2- to N2 under O2Nir
Nos
Nr asNthe
- Nar
N2
NOnitrifiers
The
of
areNO
regarded
NOactivities
2
2O main nitrogen
3
limited conditions, which is also similar to heterotrophic
removal pathway in CW systems. Among all species of
denitrification (Wrage et al. 2001).
Fig. 2 Scheme
of relevant
N2O production
pathways in
nitrifier
to nitrification,
Indaddition
to nitrifiers, N2O can be produced by aerobic
Fig. 5 Scontributing
cheme of relevant N2O pammonia-oxidizing
roduction pathways in enitrification denitrification
bacteria (AOB) are ubiquitous in wetland ecosystems and
denitrifiers, which contribute to the reduction of NO3- or
dominant members of the rhizosphere microbial NO2- to N2O and N2, respectively. Blankmer et al. (1980)
are
community.
found that heterotrophic bacteria aid in the release of N2O
the AOB’s cell while N2O will be released using NO2- as
Nitrification is a bacterial respiratory process with two
under low DO, low sludge retention time, and acidic
an electron acceptor to avoid the accumulation of NO2- in
successive
steps
carried
out
by
ubiquitous
AOB
and
nitritecondition.
the system. In nitrifier denitrification, N2O is an intermeoxidizing
bacteria
(Inamori
et al.- to
2008).
AOBO isdiate product
during(NOB)
the reduction
of
NO
N
under
2
2
2
responsible
for nitrite
(NO2is-)also
formation,
whereas
NOB is
N2O emission in denitrification
limited conditions,
which
similar
to heterotrophic
responsible
for (Wrage
the conversion
of NO2 to NO3 . The first
denitrification
et al. 2001).
stepIncan
be catalyzed
by ammonia
(Amo)
Denitrification is the microbial-mediated process carried
addition
to nitrifiers,
N2O canmonooxygennase
be produced by aerobic
-step
and
hydroxylamine
oxidoreductase
(Hao).
The
second
out by facultative aerobic bacteria and aerobic microordenitrifiers, which contribute to the reduction-of NO3 - or
of
the- nitrification
pathway, oxidation of NO2 to NO3 , is
ganisms in hypoxic or anaerobic conditions, whereby
NO
2 to N2O and N2, respectively. Blankmer et al. (1980)
catalyzed
by
nitrite
oxidoreductase
(Nor).
N
O
emission
NO3- is converted into N2 via the intermediates NO2-,
2
found that heterotrophic bacteria aid in the release of N2O
isunder
affected
by
the
activity
and
expression
of
these
three
nitric oxide (NO), and N2O. The generally recognized
low DO, low sludge retention time, and acidic
enzymes,
which
are
influenced
by
many
factors
under
pathway
is shown in Fig. 2 (Tallec et al. 2008).
condition.
different environmental conditions (Hu et al. 2011). Fig. 1
N2O is produced as an intermediate of denitrification,
shows
the pathway
of N2O emission in nitrification.
which is different from nitrification. Microbial denitrificaN2O emission
in denitrification
As a nitrification byproduct, N2O is produced mainly in
tion is a respiratory process that consists of four consecuEnviron Earth Sci (2013) 68:2171–2180
N 2O emission in nitrification
ao
iNor
N 2O
NO2- Nor
NO2·NHOH
NO3N2O
on pathways in nitrification
ed as the main nitrogen
Among all species of
on, ammonia-oxidizing
wetland ecosystems and
rhizosphere microbial
atory process with two
uitous AOB and nitritei et al. 2008). AOB is
ation, whereas NOB is
O2- to NO3-. The first
-
Human toxicity impact
(cases/year)
Human
Air pollution
activities PAHs
Inhalation
Plant
DNA damage
400
Straw (Rice)
Bituminous coal
Indigenous coking
Others
Firewood
Alumuninum
Metallurgical coking
300
200
100
0
400
Huamn toxicity impact
(Case/year)
Sediment
Mechanism analysis
Water
2005 2006 2007 2008 2009 2010 2011 2012
Soil
Ingestion
BaP
IcdP
Chr
Flu
BbF
Others
DahA
BghiP
NaP
BkF
300
200
100
0
2005 2006 2007 2008 2009 2010 2011 2012
1.0E-05
1.0E-06
<5
Inhalation
5 ~ 15
BghiP
Chr
BkF
BbF
IcdP
Nap
DahA
Flu
BaP
1.0E-08
BghiP
Chr
BkF
BbF
IcdP
Nap
DahA
Flu
BaP
PAHs air emissions
distribution (kg/km2)
4µmol/L
1.0E-07
700
120
y = 0.15x + 38.48
R² = 0.69
600
60
400
30
y = 1.84x - 100.85
R² = 0.98
300
0
200
Ingestion
24h
15 ~ 25
90
500
48h
72h
PAHs emissions (kt)
1.0E-04
0.5µmol/L 1µmol/L
iF (kginta ke/kgemission)
1.0E-03
HTP
(cases,epidemiology )
Control
1.0E-02
240
280
320
360
400
HTP (cases, animal data)
Sustainable management
25 ~ 40
> 40
Energy, raw
material supply,
waste disposal,
labor, carbon
emissions,
infrastructure,
and
maintenance
cost
Indentifying key
factors
Economic
assessment
Inputs
Process 1
Outputs
Inputs
Process 2
Outputs
Inputs
Process n
Outputs
Social information
Technical information
(Improvement potential, safety,
human rights, worker initiative,
etc) of each process
(e.g., experiments, advancment,
maneuverability, legality,
feasibility) of each process
Social assessment
Technical assessment
Life cycle multi-objective assessment
Emissions and
consumption
Environmental
impact
assessment at
mid-point and
end-point level
Indentifying key
factors
Environmental
assessment
Fig. 6 Life cycle assessment Field study Description: The Weishan Lake Wetland, located in Jining City of eastern China's Shandong Province, is one of the most famous national wetland parks in the country, thanks to its abundant lakes, flowers, plants and animals, as well as its breathtaking scenery. It was award “Top Ten Most Charming Wetlands” in 2013. Pictures: Fig.1 Photo of wetland at Lake “Weishan” Fig.2 Photo of wetland at Lake “Weishan” Fig.3 Photo of wetland at Lake “Weishan” Internet links: http://www.huanke.sdu.edu.cn/en/index.php http://en.sdu.edu.cn