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Good morning, I am Wei Zhang, and the PD for this project. The other co-PDs are Hui Li, Brian Teppen, and Stephen Boyd at MSU, Javier Gonzalez at National Soil Erosion Research Lab of ARS, and Cliff Johnston at Purdue University. I would like to thank NIFA for this opportunity to share some of our results. In this project, we are studying physicochemical factors that influence the transport of pharmaceuticals and hormones to surface waters.
So in this project, we focused on an important group of pharmaceuticals, i.e., antibiotics. Antibiotics are emerging contaminants that have been widely detected in our soils, sediments, and waters. The driver for this proliferation is the overuse by humans and animal agriculture. For instance, the US and China are two largest users of antibiotics, the majority of which are used in livestock production and then released into our environment.
Once in the environment, antibiotics can exert selection pressure on bacteria to develop and maintain antibiotic resistance. If antibiotic resistance proliferation continues at current rate, by 2050, it will cause up to 10 million deaths every year, the majority of which will happen in Asia, Africa, and Latin America. But North America and Europe will also have significant numbers.
To tackle antibiotic resistance problem, we believe that soil and environmental science community can play important roles. Therefore, this project is aimed to study what factors control the transport of antibiotics in soil and water environment, and how we could manage the transport risks. The project mainly focuses on sorption of antibiotics by soil components, and facilitated transport of antibiotics by fine particles. In particular, this project investigates black carbon interaction with antibiotics. Black carbon is produced by thermal decomposition of organic materials under oxygen-limited conditions (i.e., pyrolysis). It can be produced from wildfire, fuel combustion, or pyrolysis bioenergy production. Black carbon from engineered pyrolysis reactors is also called biochar.
Therefore, this project particularly investigated biochar soil amendment as a mitigation strategy for reducing the transport of antibiotics. There are three primary soil geosorbents: amorphous organic matter, black carbon, and clay. If we look at the diagram on the upper right corner, the fraction of sorbed tetracycline in black carbon at lower aqueous-phase tetracycline concentration was much greater than clay and AOM. Therefore, black carbon or biochar may be used to sequester antibiotics. If we add biochar to soils, due to sorption of antibiotics to biochar, their transport to shallow groundwater that eventually flows into surface water by tile drainage or lateral flow can be reduced. Antibiotics uptake by crops and bacteria can also be decreased, which is being looked at in other projects.
Because of the time limit, we cannot show everything we have accomplished in this project. We will highlight some of most interesting results. Here we used lincomycin as example because it is persistent and frequently detected in the environment. Lincomycin is hydrophilic and very soluble in water. Its pKa is 7.6. Therefore, at pH much lower than 7.6, it is cation, and at pH much higher than 7.6, it is a neutral molecule.
First, we will look at some long-term kinetics data. Most of biochar had continued sorption of lincoymcin over 6 months. This long-term sorption was due to slow diffusion of lincomycin molecules into the interior of biochar pore space. This was supported by the good fitting of kinetic data with intra-particle diffusion model. Therefore, biochar could have long-term sequestration potential for antibiotics.
Then, we investigated short-term sorption isotherms. Taking one biochar as example, lincomycin sorption was much higher at lower pH of 6 than at higher pH of 10. Now I would like remind everyone about the pH-dependent speciation of lincomycin on the right. Biochar surface is negatively charged. Therefore, at higher pH, lincomycin sorption was controlled by non-electrostatic interactions, and at lower pH, lincomycin sorption was controlled by both non-electrostatic and electrostatic interactions.
We also found that lincomycin sorption decreased with increasing solution ionic strength at lower pH and remained constant at higher pH. This was because at higher pH non-electrostatic interaction was not influenced by ionic strength, but at lower pH there was competition between Na+ and lincomycin. This is important finding, and we will come back to this when discussing the transport results.
Now let’s shift to a slightly different but relevant topic. It has been known for some time now that biochar can release a substantial amount of organic matter to water. This 2013 science paper argues that charcoal could release dissolved black carbon which eventually flows from soil to surface water. I would also like to highlight a 2014 paper by Spokas et al., reporting that biochar could be physically disintegrated to release biochar colloids and nanoparticles. In a recent 2016 paper, Qu et al. characterized chemical and structural properties of dissolved black carbon. In our own work we also found that up to 24% of total carbon in biochar could be extracted by a dilute base solution. So our question is how the release of organic carbon will influence the sorption and transport of antibiotics. In this presentation, we will mainly focus on the facilitated transport of antibiotics by biochar nanoparticles.
Here we show you the experimental design. The transport experiments were conducted at solution pH 7 for three antibiotics, lincomycin, oxytetracycline, and sulfamethoxazole. But we will only have time to discuss the results of lincomycin. We have two treatments: in the first one, we injected antibiotics-only solution into saturated sand column and then flushed it out with antibiotics-free background solution; in the second one, we injected the mixture of antibiotics and biochar nanoparticles, and then flushed the column with the background solution. We measured antibiotics concentration and biochar nanoparticle concentrations in the effluent to establish the breakthrough curves (BTCs) as shown in the next slide.
The experiments were performed in 0.1 mM, 1 mM, and 10 mM KCl background solutions. Black squares are the BTCs of lincomycin-only treatment. With increasing ionic strength, the transport of lincomycin through saturated sand column increased. Now you probably remember that this could be due to the competition from other cations. Red circles are the BTCs of free lincomycin in water in the antibiotics/biochar mixture treatment, and blue triangels are the BTCs of biochar-associated lincoymcin. Clearly, some of BC-associated lincomycin was transported out of the column. In particular, at 0.1 mM, the total lincomcyin transported was even increased to 79% of injected lincomycin from 49% without BC. Therefore, BC could facilitate the transport of lincomycin at lower ionic strength, but could promote lincomycin retention at higher ionic strength.
Here we listed other work in this project that we didn’t have time to go over today. The pH effect on facilitated antibiotics transport and rainfall simulation study with soil box are still ongoing.
Now we would like to briefly mention some outcome of this project. Two papers were published, one paper currently under revision, and four more manuscripts under preparation. We have also given 12 conference presentations, and 16 invited talks. The project supported 3 graduate students, 1 postdoc, 1 visiting student, and 1 high school student.
With that, I would like to acknowledge the funding support from NIFA and thank our collaborators. Thank you!
Physicochemical Controls On Transport of Veterinary Pharmaceuticals And Hormones To Surface Waters
Physicochemical Controls on Transport of
Veterinary Pharmaceuticals and Hormones
to Surface Waters
Cheng-Hua Liu, Ya-Hui Chuang, Wei Zhang, Hui Li,
Brian J. Teppen, Stephen A. Boyd
Department of Plant, Soil and Microbial Sciences, Michigan
State University, East Lansing, MI
Javier M. Gonzalez, National Soil Erosion Research Lab,
USDA-ARS, West Lafayette, IN
Cliff T. Johnston, Dept. of Agronomy, Purdue University, West
Washington, DC, October 12, 2016
U.S.: about 14,600
tons of antibiotics in
China: about 84,240
tons of antibiotics in
Antibiotics have been widely
detected in soils, sediments,
Antibiotics in ecosystems exert
selection pressure on bacteria
for antibiotic resistance.
Black carbon (BC) up to 45%
Czimczik & Masiello, 2007
BC on average 13.7% of SOC
Reisser et al., 2016
DBC about 11% of DOC in
Jaffé et al., 2013
on fate and transport of
Sorption to soil phases
Facilitated transport of
antibiotics by fine
Lehmann, 2007. Nature
Biochar soil amendment to
reduce the transport &
bioavailability of antibiotics
Biochar amended Soil
Primary soil geosorbents:
amorphous organic matter
(AOM), black carbon (BC) &
Sequestration of lincomycin
Lincomycin, one of lincosamides, is persistent and
frequently detected in the environment.
MW: 406.54 g/mol
Sw: 927 mg L-1
pKa: 7.6 0 2 4 6 8 10 12 14
pKa = 7.6
Liu, C.-H.; Chuang, Y.-H.; Li, H.; Teppen, B. J.; Boyd, S. A.; Gonzalez, J. M.; Johnston, C.
T.; Lehmann, J.; Zhang, W., Sorption of Lincomycin by Manure-Derived Biochars from
Water. J. Environ. Qual. 2016, 45, (2), 519-527.
0 0.01 0.05 0.1
BM600 pH = 6.0
BM600 pH = 9.8
NaCl Concentration (M)
pH and ionic strength effects
0 2 4 6 8 10 12 14
pKa = 7.6
pH << pKa
pH >> pKa
released from bull
(produced by 300oC)
in DI water
Dissolved BC = 11% of
DOC in surface water
Base-extractable OC could be up
to 24% of total carbon in biochars
Facilitated antibiotics transport by fine
A: Background Solution
B: Antibiotics/BC Suspension
Solution pH 7
pKa 7.6, 80% cations
pKa 3.2, 7.5, 8.9; 74% zwitterions
pKa 1.6, 5.7; 95% anions
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
0.1 mM 1 mM 10 mM
Free-LCM BC-sorbed LCM Total
LCM 0.1 49.4 - 49.4
1 86.6 - 86.6
10 96.5 - 96.5
LCM-BC 0.1 3.3 75.4 78.7
1 7.6 16.9 24.4
10 15.8 2.0 17.8
has higher environmental risk
Solute transport has higher
Desorption from immobile BC
should also be concerned
Completed and ongoing work
Sorption screening test of 35 biochar samples under pH 6
and pH 9 for 2 and 30 days, respectively (completed)
180-day sorption kinetics and two-day quasi-equilibrium
sorption studies for 4 biochar samples (completed)
360-day long-term sorption kinetics for 17 biochars
Attenuation effect of sorption by organic acids
Quantification and characterization of extractable organic
carbon from biochar (completed)
Facilitated transport of antibiotics by fine biochar
particles: ionic strength (completed), and pH effect
Rainfall simulation study with soil box (ongoing)
Peer-Reviewed Journal Publications
Liu, C.-H., Y.-H. Chuang, H. Li, B.J. Teppen, S.A. Boyd, J.M. Gonzalez, C.T. Johnston, J.
Lehmann, and W. Zhang. 2016. Sorption of lincomycin by manure-derived biochars from
water. Journal of Environmental Quality, 45(2), 519-527.
Stoof, C.R., A.I. Gevaert, C. Baver, B. Hassanpour, V.L. Morales, W. Zhang, D. Martin, S.K.
Giri, and T.S. Steenhuis. 2016. Can pore-clogging by ash explain post-fire runoff?
International Journal of Wildland Fire, 25(3), 294-305.
Wang, B., W. Zhang, H. Li, H. Fu, X. Qu, and D. Zhu. 201_. Micropore clogging by
dissolved black carbon: A new perspective on sorption irreversibility and kinetics of
hydrophobic organic contaminants to black carbon. Environmental Pollution (in revision).
Liu, C.-H., Y.-H. Chuang, H. Li, B.J. Teppen, S.A. Boyd, and W. Zhang. 201_. Dependence
of lincomycin sorption on biochar physicochemical properties (in preparation).
Liu, C.-H., Y.-H. Chuang, H. Li, B.J. Teppen, S.A. Boyd, and W. Zhang. 201_. Long-term
sorption kinetics of lincomycin to manure-derived biochars (in preparation).
Liu, C.-H., Y.-H. Chuang, H. Li, S.A. Boyd, J. Lehmann, B.J. Teppen, J.D. Mao, and W.
Zhang. 201_. Quantification and characteristics of dissolved organic matter released from
biochars (in preparation).
Liu, C.-H., Y.-H. Chuang, H. Li, J.P. Zarnetske, S.A. Boyd, B.J. Teppen, and W. Zhang.
201_. Black carbon nanoparticles facilitated transport of antibiotics in saturated porous
media (in preparation).
12 conference presentations & 16 invited presentations.
3 graduate students, 1 postdoc, 1 visiting student, & 1
high school student.
• Collaborators: Drs. Yingjie Zhang
(MSU), Bin Gao (UF), Johannes
Lehmann (Cornell), Jingdong Mao
(Old Dominion Univ.), Verónica L.
Morales (ETH Zurich), Dongqiang
Zhu (Peking University).
The research was supported by
Agriculture and Food Research
Initiative Competitive Grant No.
2013-67019-21377 from the
USDA National Institute of Food