18th International
Conference
HeavyMetals
Metals
inEnvironment
the Environment
18th International
Conferenceon
on Heavy
in the
ICHMET
12 to 15 September 2016, Ghent, Belgium
2016
ARSENIC BIOTRANSFORMATION BY MICROCYSTIS AERUGINOSA
UNDER DIFFERENT NITROGEN AND PHOSPHATE LEVELS
Changzhou Yan, Feifei Che, Zhuanxi Luo
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese
Academy of Sciences, Xiamen, China
[email protected]
Keywords: Arsenic; biotransformation; nitrogen; phosphorus; M. aeruginosa
Introduction
The toxicity of arsenic to organism in freshwater is dependent on its speciation and concentration. To the
best of our knowledge, little has been studied regarding the potential influence of N : P ratio on
arsenic metabolism in microalgae. In this study, we chose the typical freshwater cyanobacteria M.
aeruginosa (FACHB 905) to investigate the influences of N and P on As biotransformation. Changes in As
speciation for both the alga and culture media were measured at different levels of N and P. The observed
results would contribute to a better understanding of nitrogen-regulated interactions between As
contaminants and cyanobacteria, and facilitate the realization of As biogeochemistry in environments.
Methods
Test medium were divided into five groups according to the concentrations of N (NaNO3) and P (K2HPO4)
in the modified BG11 medium (N:P=4:0.2, 10:0.2, 20:0.2, 10:0.5, 10:1.0, respectively). Treatment groups
and control groups were subjected to same treatments, and treatment groups were exposed to 15 μg/L As(
Ⅴ) (Na3AsO4·12H2O) additionally at the beginning of the test. The experiment lasted for 8 days. Arsenic
species in the medium as well as algal digestion solutions were determined by HPLC-ICP-MS using anionexchange column as detailed by Zhu et al (Zhu et al. 2008).
Results
10
b
6
a
a a
4
b
a,b a b
2
0
12
a
10
8
b
a,b
b
a a
a
c
a
a
b
b
6
c
b
0.3
a
b
a
b
4
10:0.2
10:0.5
10:1.0
N=10mg/L
a
b
b b
a
1
2
3
4
5
Time (days)
6
7
4:0.2
10:0.2
20:0.2
a
0.2
b
b
b
0.1
0.0
N=10mg/L
0.4
10:0.2
0.3
0.2
0.1
2
0
P=0.2mg/L
0.4
As(
As( ) Concentration (μg/L)
8
a,b a
0.5
a
4:0.2
10:0.2
20:0.2
P=0.2mg/L
) Concentration (μg/L)
12
0.0
8
1
2
3
4
5
6
7
8
Time (days)
Figure 1. As(Ⅴ) (a) and As(Ⅲ) (b) in medium with exposure to 15 μg/L As(Ⅴ) under five concentrations of N and
P during a 8-day cultivation.
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2016,
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Abstract
Bookofofthe
the1818 International
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2016,
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18th International Conference on Heavy Metals in the Environment
1.6
Concentration of MMA (μg/L)
1.0
a
P=0.2mg/L
4:0.2
10:0.2
20:0.2
1.2
b
b
a
b
0.6
0.4
c b
0.2
a
c
a
b
c
0.0
1.4
N=10mg/L
10:0.2
10:0.5
10:1.0
1.2
1.0
a
a
a
0.8
a
0.6
0.4
a
b
b
b
b
0.0
1
2
3
4
5
6
8
7
b
a
6
4
a
b
c
b
a
a a
c
b
b
c b a
0
12
N=10mg/L
10:0.2
10:0.5
10:1.0
10
8
a
6
a
2
0
1
Time (days)
2
b
b
3
b
b
c
b
c
c
c
c
4
a
b
a
a
a
4
8
a
b a
c
2
c
c
b
0.2
P=0.2mg/L
4:0.2
10:0.2
20:0.2
10
c
c
c
12
b
a
0.8
14
a
a
Concentration of DMA (μg/L)
1.4
5
6
Time (days)
7
8
Figure 2. MMA (a) and DMA (b) in medium with 15 μg/L As(Ⅴ) exposure under different N and P conditions
during a 8-day cultivation.
12
a P=0.2mg/L
As( )
b
10
a
a
8
c
6
b
b
c
4:0.2
10:0.2
20:0.2
a
14
12
10
b a,b
0
0
2
4
6
As( )
2.5
8
b
3.0
2.0
1.5
1.5
0.5
0.0
b
a,b a
b
a
2
4
6
0.4
a
a
b
8
As( )
N=10mg/L
10:0.2
10:0.5
10:1.0
2.5
2.0
1.0
c
c
3.5
4:0.2
10:0.2
20:0.2
10:0.2
10:0.5
10:1.0
a
b
b
4
2
P=0.2mg/L
As( )
a
a
6
a
2
3.0
a
8
b
4
3.5
N=10mg/L
Concentration of Organoarsenicals (μg/g DW)
Inorganic Arsenic Concentration (μg/g DW)
14
b
a
b
1.0
b
0.5
2
4
6
8
0.0
Time (days)
2
4
6
MMA
4:0.2
10:0.2
20:0.2
0.3
0.0
2
4
P=0.2mg/L
a
1.0
b
b
6
a
a
a,b
b
0.5
2
4
b
6
d
1.5
2
4
N=10mg/L
6
8
10:0.2
10:0.5
10:1.0
a
b
1.0
b
DMA
a
b
0.0
d
a
a
a,b
0.5
8
c
a
b
a
a
10:0.2
10:0.5
10:1.0
a
0.0
4:0.2
10:0.2
20:0.2
a
c
MMA
0.1
8
DMA
N=10mg/L
0.2
c
b
0.4
0.3
b
a a
0.1
1.5
c
a
0.2
0.0
8
P=0.2mg/L
b
2
4
6
8
Time (days)
Figure 3. Intracellular concentrations of As(Ⅴ) (a), As(Ⅲ) (b), MMA (c), and DMA (d) within a 8-day As(Ⅴ)
exposure under different conditions of N and P.
Conclusion
Arsenate biotransformation in M. aeruginosa was accelerated by increasing N levels, but was inhibited by
increasing P levels in medium. Increasing N levels indirectly facilitated As metabolism possibly according
to the stimulation on algal growth. Dissimilarly, P showed significant regulation on As biotransformation
mainly through the mediation on arsenate uptake by M. aeruginosa. The finding of nutrients regulation on
As metabolism can be considered to mediate As geochemical cycling, and therefore alleviate As
contamination risk in aquatic ecosystem.
References
Guo, P.R.; Gong, Y.; Wang, C.; Liu, X.; Liu, J.T. (2011): Arsenic Speciation and Effect of Arsenate Inhibition in a
Microcystis Aeruginosa Culture Medium under Different Phosphate Regimes. Environ Toxicol Chem 30, 17541759.
Wang, Z.H.; Luo, Z.X.; Yan, C.Z. (2013): Accumulation, transformation, and release of inorganic arsenic by the
freshwater cyanobacterium Microcystis aeruginosa. Environ Sci Pollut R 20, 7286-7295.
Zhu, Y.G.; Sun, G.X.; Lei, M.; Teng, M.; Liu, Y.X.; Chen, N.C.; Wang, L.H.; Carey, A.M.; Deacon, C.; Raab, A.;
Meharg, A.A.; Williams, P.N.(2008): High percentage inorganic arsenic content of mining impacted and
nonimpacted Chinese rice. Environ Sci Technol 42, 5008-5013.
‐
597 -
th th
Proceedings
the
Environment,
1212
toto
1515
September
2016,
Ghent,
Belgium
Abstract
Bookofofthe
the1818 International
InternationalConference
ConferenceononHeavy
HeavyMetals
Metalsinin
the
Environment,
September
2016,
Ghent,
Belgium
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
2 ––
––686