Arturo A. Keller is a civil and environmental engineer and an academic. He is a professor at the Bren School of Environmental Science & Management[1] at the University of California, Santa Barbara.[2]

Arturo A. Keller
Born
United States
NationalityAmerican and Mexican
Occupation(s)Civil and environmental engineer and an academic
AwardsUnited States Water Prize, U.S. Water Alliance (2015)
Agilent Thought Leadership Award (2015)
Outstanding Graduate Mentor Award, UCSB (2023)
Academic background
EducationB.S., Chemical Engineering
B.A., Chemistry
M.S., Civil Engineering
PhD, Civil Engineering
Alma materCornell University
Stanford University
Academic work
InstitutionsUniversity of California, Santa Barbara

Keller is most known for his work on water quality and resource management, primarily focusing on emerging contaminants as well as creating technologies and management strategies to address water pollution.[3] His work is highly cited, with over 23,300 citations.[3] He is the recipient of the 2015 Agilent Thought Leadership award for his contributions towards the contemporary understanding of the potential environmental implications of nanotechnology, with a specific focus on its impact within agricultural systems.[4]

Education

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Keller obtained a B.S. in Chemical Engineering and B.A. in Chemistry from Cornell University in 1980. In 1992, he completed his M.S. in Civil (Environmental) Engineering, followed by a PhD in Civil (Environmental) Engineering in 1996 from Stanford University.[2]

Career

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Keller started his academic career in 1996 by joining the University of California, Santa Barbara. There he held multiple appointments including serving as an assistant professor at the Bren School of Environmental Science and Management from 1992 to 1996, and associate professor from 2002 to 2006. Since 2006, he has been a professor.[2] In 2023, he was promoted to the rank of Distinguished professor.[5]

From 1992 to 1996, Keller worked as a Research Associate in the Environmental Division at the Electric Power Research Institute (EPRI). He co-directed the UC Center on the Environmental Implications of Nanotechnology, from 2008 to 2020.[6] He also co-directed the USEPA-funded Chemical Life Cycle Collaborative between 2014 and 2019, where the team developed a framework to predict early life-cycle impacts of new chemicals based on molecular structure, applications, and use characteristics.[2]

Research

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Keller has contributed to the management of the Santa Ana River basin and the establishment of a nutrient trading program for the Ohio River Basin, which earned him recognition through a 2015 US Water Prize.[7] His group received a grant from USEPA and developed a framework employing artificial intelligence, specifically machine learning, alongside other predictive techniques for expeditiously conducting risk assessments for both novel and pre-existing chemicals. He also developed the first numerical model, ChemFate, capable of accommodating diverse chemical classes within one unified framework.[8] He has authored numerous publications spanning the fields of water quality and resource management, environmental engineering, the fate and toxicity of nanomaterials as well as their effects on crops.[3]

Environmental science and engineering

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Keller's environmental sciences research has focused on developing methods for quantifying nanomaterial use and release, both at the global and regional levels. His collaborative work with Suzanne McFerran and others provided a global assessment of likely engineered nanomaterials (ENM) emissions into the environment and landfills, revealing their dominant types, applications, and estimated distribution in various environmental compartments.[9] In his estimation of the ENM concentrations at global, regional, national, and local levels, he used a life-cycle approach and material flow analysis, to assess ENM concentrations at different environmental scales, including examples like the San Francisco Bay area, addressing their relevance for industry, regulators, and toxicologists.[10] In his 2014 study, alongside Anastasiya Lazareva, he estimated ENM release from different uses, in particular personal care products,[10] developed an environmental release model for ENMs in major cities, highlighting local factors' influence on release, and found that ENM concentrations across cities would vary significantly, due to local conditions that control the fate of ENMs.[11] In 2023, his team evaluated the potential implications of nanotechnology from 2020 to 2030, and found that there is a projected rapid pace of introduction of novel nanomaterials in applications such as renewable energy generation and storage, but that personal care products continue to represent the most significant release to the environment.[12] Some of his current work is investigating the life cycle of these materials as they are processed in water treatment facilities, and accumulate in bio-solids.[13]

In collaboration with Peng Wang, Keller and his team have developed a novel class of magnetic nanomaterials, Mag-PCMAs, that can be used to treat water with a wide range of contaminants, including many organic pollutants,[14][15] oxyanions such as perchlorate,[16] and metals.[17] Very recently, he and Qian Gao demonstrated the use of these novel nanoparticles for water disinfection, to remove pathogens while being able to reuse the disinfectant, thereby reducing cost and environmental impacts.[18] Key to the eventual use of nanotechnology for water treatment will be its effectiveness and cost-competitiveness, which was assessed by Keller, Adeyemi Adeleye and other colleagues.[19] With these concepts in mind, he and Victoria Broje developed an advanced oil skimmer for collecting oil from seawater after an oil spill.[20]

Fate and toxicity of different classes of nanomaterials

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Keller has focused on the fate and toxicity of different classes of nanomaterials. His collaborative work with Hongtao Wang and others explored the conditions that increase or decrease the likelihood of exposure to ENMs, particularly in the aquatic environment. Studies of the behavior of well known ENMs, such as Titanium Dioxide (TiO2), Zinc Oxide (ZnO), and Cerium Dioxide (CeO2), within aqueous matrices commonly encountered in realistic environmental settings such as freshwater, groundwater, estuarine and marine waters, demonstrated the major influence of water characteristics such as pH, natural organic matter, and ionic strength (water hardness and salinity).[21] Furthermore, working with Adeyemi Adeleye and others, they demonstrated that microscopic organisms such as phytoplankton and microbes can release extracellular polymeric substances, that play a key role in the determining how ENMs will behave in natural waters.[22] Other studies showed that ENMs are very likely to form aggregates with natural sediments in water, and in fact this can be used as a "cleansing" mechanism to remove ENMs from contaminated water, by adding clay particles to remove them.[23] In 2014, he and his colleague Kendra Garner performed an analysis of publications, to develop the emerging patterns for ENMs in the environment, assessing the potential exposure and toxicity of the most widely used ENMs, and ranking them from high to low risk.[24] These studies led to the development of the nanoFate model, which can be used to assess the predicted environmental concentrations of ENMs in different regions, under a variety of conditions, and considers the dynamics of ENM release as well as local climate and hydrology.[25] Keller has also worked closely with ecotoxicologists, to investigate the health effects of ENMs on different aquatic organisms, such as marine phytoplankton,[26] sea urchins,[27] daphnids,[28] and mussels. These studies have demonstrated that some ENMs pose a health risk to diverse organisms at higher concentrations, typically above predicted environmental concentrations. For example, TiO2 nanoparticles are phototoxic to marine phytoplankton,[29] while ZnO nanoparticles notably inhibited their growth.[26] Mussels are filter feeders, and can thus remove large number of particles from water, including ENMs, which can result in transfer of ENMs up the food chain.[30] Eventually, the results of several toxicity studies on a wide range of aquatic species was assessed using Species Sensitivity Distributions for nanomaterials, a tool developed by USEPA to better assess the potential impact of toxicants on an ecosystem.[31]

Effects of nanomaterials on crops

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Keller, in his research, has recently turned his attention to the benefits and potential negative implications of ENMs on agricultural crops. Copper-based nanopesticides promise high effectiveness against fungi and other crop pests, while potentially reducing the amount applied. This may result in less cost for the farmer, and lower environmental implications. Working with Yiming Su and colleagues, they demonstrated that for nanotechnology to live up to its promise, costs have to continue to decrease, while effectiveness requires a careful assessment of the form in which the nanopesticides are formulated.[32] In collaboration with Lijuan Zhao and others, the benefits of nanotechnology to reduce plant stress were assessed.[33] To evaluate the effect of ENMs on crop plants, his research group have been researching the use of metabolomics, to assess how plants respond to the use of different ENMs. His metabolomics analysis with Lijuan Zhao and others highlighted the potential implications and detoxification strategies associated with the agricultural use of nano-Cu and demonstrated that exposure to copper nanoparticles (nano-Cu) in hydroponic culture significantly alters nutrient uptake, triggers metabolic changes, and activates defense mechanisms in cucumber plants.[34][35] In his investigation of the interaction between Cu(OH)2 nano pesticides and lettuce plants, his study provided insights into the molecular-scale plant response to copper nano pesticides in agriculture, and revealed that exposure of lettuce plants to Cu(OH)2 nano pesticides predominantly accumulated copper in leaves, disrupted metabolism, caused oxidative stress, and triggered detoxification.[36] Furthermore, a study suggested that Cu-containing nano pesticides, while not harming photosynthesis in cucumber plants, induce molecular responses related to antioxidant and detoxification genes, potentially serving as biomarkers for nano pesticide exposure.[37] In related research, his exploration of the metabolic effects of Cu(OH)2 nano pesticide and copper ions on spinach leaves revealed reductions in antioxidants, disruption of metabolic pathways, and a potential decrease in nutritional value.[38]

Water quality and resource management

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At the larger scale, Keller has developed the science for large-scale water quality trading programs. For trading to be effective, knowledge of the factors that go into evaluating a trade was developed by Keller and his team.[39] This work led to the 2015 United States Water Prize from the U.S. Water Alliance to the team led by Jessica Fox at the Electric Power Research Institute.[7] Keller and Hongtao Wang, along with other collaborators, have also made contributions to the assessment of the Energy-Water Nexus, that is the linkage between these two key resources. His research highlighted many important aspects, including the fact that significant energy is needed for potable water treatment,[40] as well as for wastewater processing.[41][42] His research further emphasized that the water footprint of the iron and steel industry is also significant, with important implications for China and other major economies.[43] Additionally, his research also stressed that water is also an important aspect in power generation, which is changing as the use of renewable energies continues to rise.[44]

Awards and honors

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  • 2015 – Agilent Thought Leadership Award, Agilent Technologies[4]
  • 2015 – United States Water Prize, U.S. Water Alliance[7]

Selected articles

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  • Keller, A. A., Wang, H., Zhou, D., Lenihan, H. S., Cherr, G., Cardinale, B. J., ... & Ji, Z. (2010). Stability and aggregation of metal oxide nanoparticles in natural aqueous matrices. Environmental science & technology, 44(6), 1962–1967.
  • Keller, A. A., McFerran, S., Lazareva, A., & Suh, S. (2013). Global life cycle releases of engineered nanomaterials. Journal of nanoparticle research, 15, 1–17.
  • Keller, A. A., & Lazareva, A. (2014). Predicted releases of engineered nanomaterials: from global to regional to local. Environmental Science & Technology Letters, 1(1), 65–70.
  • Adeleye, A. S., Conway, J. R., Garner, K., Huang, Y., Su, Y., & Keller, A. A. (2016). Engineered nanomaterials for water treatment and remediation: Costs, benefits, and applicability. Chemical Engineering Journal, 286, 640–662.
  • Miller, R. J., Lenihan, H. S., Muller, E. B., Tseng, N., Hanna, S. K., & Keller, A. A. (2010). Impacts of metal oxide nanoparticles on marine phytoplankton. Environmental science & technology, 44(19), 7329–7334.

References

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  1. ^ "Arturo Keller". UCSB Bren School of Environmental Science & Management. Retrieved March 20, 2024.
  2. ^ a b c d "Arturo A. Keller". www.aiche.org. November 12, 2020.
  3. ^ a b c "Arturo A. Keller". scholar.google.com.
  4. ^ a b "Agilent | Agilent Technologies Presents Thought Leader Award to Environmental Researcher Dr. Arturo Keller of U.C. Santa Barbara". www.agilent.com. June 9, 2015.
  5. ^ "Arturo Keller". UCSB Bren School of Environmental Science & Management.
  6. ^ Godwin, Hilary A.; Chopra, Kabir; Bradley, Kenneth A.; Cohen, Yoram; Harthorn, Barbara Herr; Hoek, Eric M.V.; Holden, Patricia; Keller, Arturo A.; Lenihan, Hunter S.; Nisbet, Roger M.; Nel, Andre E. (September 1, 2009). "The University of California Center for the Environmental Implications of Nanotechnology". Environmental Science & Technology. 43 (17): 6453–6457. doi:10.1021/es8034544. PMID 19764201.
  7. ^ a b c "The Water Network | by AquaSPE". thewaternetwork.com.
  8. ^ Tao, Mengya; Keller, Arturo A. (September 1, 2020). "ChemFate: A fate and transport modeling framework for evaluating radically different chemicals under comparable conditions". Chemosphere. 255: 126897. Bibcode:2020Chmsp.25526897T. doi:10.1016/j.chemosphere.2020.126897. PMID 32402873. S2CID 218633278 – via ScienceDirect.
  9. ^ Keller, Arturo A.; McFerran, Suzanne; Lazareva, Anastasiya; Suh, Sangwon (May 16, 2013). "Global life cycle releases of engineered nanomaterials". Journal of Nanoparticle Research. 15 (6): 1692. Bibcode:2013JNR....15.1692K. doi:10.1007/s11051-013-1692-4. S2CID 97011693 – via Springer Link.
  10. ^ a b Keller, Arturo A.; Lazareva, Anastasiya (January 14, 2014). "Predicted Releases of Engineered Nanomaterials: From Global to Regional to Local". Environmental Science & Technology Letters. 1 (1): 65–70. Bibcode:2014EnSTL...1...65K. doi:10.1021/ez400106t. S2CID 112325241 – via CrossRef.
  11. ^ Lazareva, Anastasiya; Keller, Arturo A. (July 7, 2014). "Estimating Potential Life Cycle Releases of Engineered Nanomaterials from Wastewater Treatment Plants". ACS Sustainable Chemistry & Engineering. 2 (7): 1656–1665. doi:10.1021/sc500121w – via CrossRef.
  12. ^ Keller, Arturo A.; Ehrens, Alex; Zheng, Yuanfang; Nowack, Bernd (August 2, 2023). "Developing trends in nanomaterials and their environmental implications". Nature Nanotechnology. 18 (8): 834–837. Bibcode:2023NatNa..18..834K. doi:10.1038/s41565-023-01409-z. PMID 37280284. S2CID 259098526 – via PubMed.
  13. ^ "NextGen Water Solutions". UCSB Bren School of Environmental Science & Management. Retrieved November 1, 2023.
  14. ^ Wang, Peng; Shi, Qihui; Shi, Yifeng; Clark, Kristin K.; Stucky, Galen D.; Keller, Arturo A. (January 14, 2009). "Magnetic Permanently Confined Micelle Arrays for Treating Hydrophobic Organic Compound Contamination". Journal of the American Chemical Society. 131 (1): 182–188. doi:10.1021/ja806556a. PMID 19055347 – via CrossRef.
  15. ^ Huang, Yuxiong; Keller, Arturo A. (July 1, 2013). "Magnetic Nanoparticle Adsorbents for Emerging Organic Contaminants". ACS Sustainable Chemistry & Engineering. 1 (7): 731–736. doi:10.1021/sc400047q. S2CID 98182663 – via CrossRef.
  16. ^ Clark, Kristin K.; Keller, Arturo A. (March 1, 2012). "Adsorption of perchlorate and other oxyanions onto magnetic permanently confined micelle arrays (Mag-PCMAs)". Water Research. 46 (3): 635–644. Bibcode:2012WatRe..46..635C. doi:10.1016/j.watres.2011.11.025. PMID 22154111 – via ScienceDirect.
  17. ^ Huang, Yuxiong; Keller, Arturo A. (September 1, 2015). "EDTA functionalized magnetic nanoparticle sorbents for cadmium and lead contaminated water treatment". Water Research. 80: 159–168. Bibcode:2015WatRe..80..159H. doi:10.1016/j.watres.2015.05.011. PMID 26001282. S2CID 205693991 – via ScienceDirect.
  18. ^ Gao, Qian; Keller, Arturo A. (January 8, 2021). "Redesigning Water Disinfection Using Recyclable Nanomaterials and Metal Ions: Evaluation with Escherichia coli". ACS ES&T Water. 1 (1): 185–194. doi:10.1021/acsestwater.0c00066. S2CID 224949410.
  19. ^ Adeleye, Adeyemi S.; Conway, Jon R.; Garner, Kendra; Huang, Yuxiong; Su, Yiming; Keller, Arturo A. (February 15, 2016). "Engineered nanomaterials for water treatment and remediation: Costs, benefits, and applicability". Chemical Engineering Journal. 286: 640–662. Bibcode:2016ChEnJ.286..640A. doi:10.1016/j.cej.2015.10.105. S2CID 51775940.
  20. ^ Broje, Victoria; Keller, Arturo A. (December 1, 2006). "Improved Mechanical Oil Spill Recovery Using an Optimized Geometry for the Skimmer Surface". Environmental Science & Technology. 40 (24): 7914–7918. Bibcode:2006EnST...40.7914B. doi:10.1021/es061842m. PMID 17256548 – via CrossRef.
  21. ^ Keller, Arturo A.; Wang, Hongtao; Zhou, Dongxu; Lenihan, Hunter S.; Cherr, Gary; Cardinale, Bradley J.; Miller, Robert; Ji, Zhaoxia (March 15, 2010). "Stability and Aggregation of Metal Oxide Nanoparticles in Natural Aqueous Matrices". Environmental Science & Technology. 44 (6): 1962–1967. Bibcode:2010EnST...44.1962K. doi:10.1021/es902987d. PMID 20151631 – via CrossRef.
  22. ^ Adeleye, Adeyemi S.; Conway, Jon R.; Perez, Thomas; Rutten, Paige; Keller, Arturo A. (November 4, 2014). "Influence of Extracellular Polymeric Substances on the Long-Term Fate, Dissolution, and Speciation of Copper-Based Nanoparticles". Environmental Science & Technology. 48 (21): 12561–12568. Bibcode:2014EnST...4812561A. doi:10.1021/es5033426. PMID 25295836. S2CID 5423241 – via CrossRef.
  23. ^ Zhou, Dongxu; Abdel-Fattah, Amr I.; Keller, Arturo A. (July 17, 2012). "Clay Particles Destabilize Engineered Nanoparticles in Aqueous Environments". Environmental Science & Technology. 46 (14): 7520–7526. Bibcode:2012EnST...46.7520Z. doi:10.1021/es3004427. PMID 22721423 – via CrossRef.
  24. ^ Garner, Kendra L.; Keller, Arturo A. (October 2, 2014). "Emerging patterns for engineered nanomaterials in the environment: a review of fate and toxicity studies". Journal of Nanoparticle Research. 16 (8): 2503. Bibcode:2014JNR....16.2503G. doi:10.1007/s11051-014-2503-2. S2CID 135526146 – via www.academia.edu.
  25. ^ Garner, Kendra L.; Suh, Sangwon; Keller, Arturo A. (May 16, 2017). "Assessing the Risk of Engineered Nanomaterials in the Environment: Development and Application of the nanoFate Model". Environmental Science & Technology. 51 (10): 5541–5551. Bibcode:2017EnST...51.5541G. doi:10.1021/acs.est.6b05279. PMID 28443660. S2CID 206563615 – via CrossRef.
  26. ^ a b Miller, Robert J.; Lenihan, Hunter S.; Muller, Erik B.; Tseng, Nancy; Hanna, Shannon K.; Keller, Arturo A. (October 1, 2010). "Impacts of Metal Oxide Nanoparticles on Marine Phytoplankton". Environmental Science & Technology. 44 (19): 7329–7334. Bibcode:2010EnST...44.7329M. doi:10.1021/es100247x. PMID 20469893 – via CrossRef.
  27. ^ Fairbairn, Elise A.; Keller, Arturo A.; Mädler, Lutz; Zhou, Dongxu; Pokhrel, Suman; Cherr, Gary N. (September 15, 2011). "Metal oxide nanomaterials in seawater: Linking physicochemical characteristics with biological response in sea urchin development". Journal of Hazardous Materials. 192 (3): 1565–1571. Bibcode:2011JHzM..192.1565F. doi:10.1016/j.jhazmat.2011.06.080. PMID 21775060 – via ScienceDirect.
  28. ^ Keller, Arturo A.; Garner, Kendra; Miller, Robert J.; Lenihan, Hunter S. (August 30, 2012). "Toxicity of Nano-Zero Valent Iron to Freshwater and Marine Organisms". PLOS ONE. 7 (8): e43983. Bibcode:2012PLoSO...743983K. doi:10.1371/journal.pone.0043983. PMC 3431385. PMID 22952836.
  29. ^ Miller, Robert J.; Bennett, Samuel; Keller, Arturo A.; Pease, Scott; Lenihan, Hunter S. (October 2, 2012). "TiO2 nanoparticles are phototoxic to marine phytoplankton". PLOS ONE. 7 (1): e30321. Bibcode:2012PLoSO...730321M. doi:10.1371/journal.pone.0030321. PMC 3262817. PMID 22276179.
  30. ^ Conway, Jon R.; Hanna, Shannon K.; Lenihan, Hunter S.; Keller, Arturo A. (February 4, 2014). "Effects and Implications of Trophic Transfer and Accumulation of CeO 2 Nanoparticles in a Marine Mussel". Environmental Science & Technology. 48 (3): 1517–1524. Bibcode:2014EnST...48.1517C. doi:10.1021/es404549u. PMID 24410520. S2CID 206976387 – via CrossRef.
  31. ^ Garner, K. L.; Suh, S.; Lenihan, H. S.; Keller, A. A. (2015). "Species Sensitivity Distributions for Engineered Nanomaterials | Environmental Science & Technology". Environmental Science & Technology. 49 (9): 5753–5759. doi:10.1021/acs.est.5b00081. PMID 25875138.
  32. ^ Su, Yiming; Zhou, Xuefei; Meng, Huan; Xia, Tian; Liu, Haizhou; Rolshausen, Philippe; Roper, Caroline; McLean, Joan E.; Zhang, Yalei; Keller, Arturo A.; Jassby, David (December 2, 2022). "Cost–benefit analysis of nanofertilizers and nanopesticides emphasizes the need to improve the efficiency of nanoformulations for widescale adoption". Nature Food. 3 (12): 1020–1030. doi:10.1038/s43016-022-00647-z. PMID 37118298. S2CID 254176813 – via www.nature.com.
  33. ^ Zhao, Lijuan; Bai, Tonghao; Wei, Hui; Gardea-Torresdey, Jorge L.; Keller, Arturo; White, Jason C. (October 2, 2022). "Nanobiotechnology-based strategies for enhanced crop stress resilience". Nature Food. 3 (10): 829–836. doi:10.1038/s43016-022-00596-7. PMID 37117882. S2CID 252702211 – via PubMed.
  34. ^ Zhao, L.; Huang, Y.; Hu, J.; Zhou, H.; Adeleye, A. S.; Keller, A. A. (2016). "1H NMR and GC-MS Based Metabolomics Reveal Defense and Detoxification Mechanism of Cucumber Plant under Nano-Cu Stress | Environmental Science & Technology". Environmental Science & Technology. 50 (4): 2000–2010. doi:10.1021/acs.est.5b05011. PMID 26751164. S2CID 206553906.
  35. ^ Zhao, Lijuan; Hu, Jerry; Huang, Yuxiong; Wang, Hongtao; Adeleye, Adeyemi; Ortiz, Cruz; Keller, Arturo A. (January 2, 2017). "1H NMR and GC-MS based metabolomics reveal nano-Cu altered cucumber (Cucumis sativus) fruit nutritional supply". Plant Physiology and Biochemistry: PPB. 110: 138–146. doi:10.1016/j.plaphy.2016.02.010. PMID 26922143. S2CID 19447105.
  36. ^ Zhao, Lijuan; Ortiz, Cruz; Adeleye, Adeyemi S.; Hu, Qirui; Zhou, Hongjun; Huang, Yuxiong; Keller, Arturo A. (September 6, 2016). "Metabolomics to Detect Response of Lettuce (Lactuca sativa) to Cu(OH)2 Nanopesticides: Oxidative Stress Response and Detoxification Mechanisms". Environmental Science & Technology. 50 (17): 9697–9707. Bibcode:2016EnST...50.9697Z. doi:10.1021/acs.est.6b02763. PMID 27483188. S2CID 206560644.
  37. ^ Zhao, Lijuan; Hu, Qirui; Huang, Yuxiong; Fulton, Aaron N.; Hannah-Bick, Cameron; Adeleye, Adeyemi S.; Keller, Arturo A. (August 10, 2017). "Activation of antioxidant and detoxification gene expression in cucumber plants exposed to a Cu(OH)2 nanopesticide". Environmental Science: Nano. 4 (8): 1750–1760. doi:10.1039/C7EN00358G. S2CID 51836842 – via pubs.rsc.org.
  38. ^ Zhao, Lijuan; Huang, Yuxiong; Adeleye, Adeyemi S.; Keller, Arturo A. (September 5, 2017). "Metabolomics Reveals Cu(OH) 2 Nanopesticide-Activated Anti-oxidative Pathways and Decreased Beneficial Antioxidants in Spinach Leaves". Environmental Science & Technology. 51 (17): 10184–10194. Bibcode:2017EnST...5110184Z. doi:10.1021/acs.est.7b02163. PMID 28738142. S2CID 206570926 – via CrossRef.
  39. ^ Keller, Arturo A.; Chen, Xiaoli; Fox, Jessica; Fulda, Matt; Dorsey, Rebecca; Seapy, Briana; Glenday, Julia; Bray, Erin (June 17, 2014). "Attenuation Coefficients for Water Quality Trading". Environmental Science & Technology. 48 (12): 6788–6794. Bibcode:2014EnST...48.6788K. doi:10.1021/es500202x. PMID 24866482. S2CID 35513880 – via CrossRef.
  40. ^ Lee, Mengshan; Keller, Arturo A.; Chiang, Pen-Chi; Den, Walter; Wang, Hongtao; Hou, Chia-Hung; Wu, Jiang; Wang, Xin; Yan, Jinyue (November 1, 2017). "Water-energy nexus for urban water systems: A comparative review on energy intensity and environmental impacts in relation to global water risks". Applied Energy. 205: 589–601. Bibcode:2017ApEn..205..589L. doi:10.1016/j.apenergy.2017.08.002. S2CID 13644768 – via ScienceDirect.
  41. ^ Wang, Hongtao; Yang, Yi; Keller, Arturo A.; Li, Xiang; Feng, Shijin; Dong, Ya-nan; Li, Fengting (December 15, 2016). "Comparative analysis of energy intensity and carbon emissions in wastewater treatment in USA, Germany, China and South Africa". Applied Energy. 184: 873–881. Bibcode:2016ApEn..184..873W. doi:10.1016/j.apenergy.2016.07.061 – via ScienceDirect.
  42. ^ Gu, Yifan; Dong, Ya-nan; Wang, Hongtao; Keller, Arturo; Xu, Jin; Chiramba, Thomas; Li, Fengting (January 1, 2016). "Quantification of the water, energy and carbon footprints of wastewater treatment plants in China considering a water–energy nexus perspective". Ecological Indicators. 60: 402–409. Bibcode:2016EcInd..60..402G. doi:10.1016/j.ecolind.2015.07.012. S2CID 54079351 – via ScienceDirect.
  43. ^ Gu, Yifan; Xu, Jin; Keller, Arturo A.; Yuan, Dazhi; Li, Yi; Zhang, Bei; Weng, Qianting; Zhang, Xiaolei; Deng, Ping; Wang, Hongtao; Li, Fengting (April 1, 2015). "Calculation of water footprint of the iron and steel industry: a case study in Eastern China". Journal of Cleaner Production. 92: 274–281. Bibcode:2015JCPro..92..274G. doi:10.1016/j.jclepro.2014.12.094. S2CID 154590239 – via ScienceDirect.
  44. ^ Keller, Arturo A.; Tellinghuisen, Stacy; Lee, Cheryl; Larson, Dana; Dennen, Bliss; Lee, James (2010). "Projection of California's Future Freshwater Requirements for Power Generation". Energy & Environment. 21 (2): 1–20. Bibcode:2010EnEnv..21....1K. doi:10.1260/0958-305X.21.2.1. S2CID 154346357.