Publications
28 results found
Qian J, Hu T, Xiong H, et al., 2024, Turbid Waters and Clearer Standards: Refining Water Quality Criteria for Coastal Environments by Encompassing Metal Bioavailability from Suspended Particles., Environ Sci Technol, Vol: 58, Pages: 5244-5254
Suspended particulate matter (SPM) carries a major fraction of metals in turbid coastal waters, markedly influencing metal bioaccumulation and posing risks to marine life. However, its effects are often overlooked in current water quality criteria for metals, primarily due to challenges in quantifying SPM's contribution. This contribution depends on the SPM concentration, metal distribution coefficients (Kd), and the bioavailability of SPM-bound metals (assimilation efficiency, AE), which can collectively be integrated as a modifying factor (MF). Accordingly, we developed a new stable isotope method to measure metal AE by individual organisms from SPM, employing the widely distributed filter-feeding clam Ruditapes philippinarum as a representative species. Assessing SPM from 23 coastal sites in China, we found average AEs of 42% for Zn, 26% for Cd, 20% for Cu, 8% for Ni, and 6% for Pb. Moreover, using stable isotope methods, we determined metal Kd of SPM from these sites, which can be well predicted by the total organic carbon and iron content (R2 = 0.977). We calculated MFs using a Monte Carlo method. The calculated MFs are in the range 9.9-43 for Pb, 8.5-37 for Zn, 2.9-9.7 for Cu, 1.4-2.7 for Ni, and 1.1-1.6 for Cd, suggesting that dissolved-metal-based criteria values should be divided by MFs to provide adequate protection to aquatic life. This study provides foundational guidelines to refine water quality criteria in turbid waters and protect coastal ecosystems.
Liu F, Gledhill M, Tan Q-G, et al., 2022, Phycosphere pH of unicellular nano- and micro- phytoplankton cells and consequences for iron speciation, The ISME Journal: multidisciplinary journal of microbial ecology, Vol: 16, Pages: 2329-2336, ISSN: 1751-7362
Surface ocean pH is declining due to anthropogenic atmospheric CO2 uptake with a global decline of ~0.3 possible by 2100. Extracellular pH influences a range of biological processes, including nutrient uptake, calcification and silicification. However, there are poor constraints on how pH levels in the extracellular microenvironment surrounding phytoplankton cells (the phycosphere) differ from bulk seawater. This adds uncertainty to biological impacts of environmental change. Furthermore, previous modelling work suggests that phycosphere pH of small cells is close to bulk seawater, and this has not been experimentally verified. Here we observe under 140 μmol photons·m−2·s−1 the phycosphere pH of Chlamydomonas concordia (5 µm diameter), Emiliania huxleyi (5 µm), Coscinodiscus radiatus (50 µm) and C. wailesii (100 µm) are 0.11 ± 0.07, 0.20 ± 0.09, 0.41 ± 0.04 and 0.15 ± 0.20 (mean ± SD) higher than bulk seawater (pH 8.00), respectively. Thickness of the pH boundary layer of C. wailesii increases from 18 ± 4 to 122 ± 17 µm when bulk seawater pH decreases from 8.00 to 7.78. Phycosphere pH is regulated by photosynthesis and extracellular enzymatic transformation of bicarbonate, as well as being influenced by light intensity and seawater pH and buffering capacity. The pH change alters Fe speciation in the phycosphere, and hence Fe availability to phytoplankton is likely better predicted by the phycosphere, rather than bulk seawater. Overall, the precise quantification of chemical conditions in the phycosphere is crucial for assessing the sensitivity of marine phytoplankton to ongoing ocean acidification and Fe limitation in surface oceans.
Zhou L, Liu F, Liu Q, et al., 2021, Aluminum increases net carbon fixation by marine diatoms and decreases their decomposition: Evidence for the iron-aluminum hypothesis, LIMNOLOGY AND OCEANOGRAPHY, Vol: 66, Pages: 2712-2727, ISSN: 0024-3590
Liu F, Tan Q-G, Weiss D, et al., 2020, Unravelling metal speciation in the microenvironment surrounding phytoplankton cells to improve predictions of metal bioavailability., Environmental Science and Technology (Washington), Vol: 54, Pages: 8177-8185, ISSN: 0013-936X
A lack of knowledge on metal speciation in the microenvironment surrounding phytoplankton cells (i.e., the phycosphere) represents an impediment to accurately predicting metal bioavailability. Phycosphere pH and O2 concentrations from a diversity of algae species were compiled. For marine algae in the light, the average increases were 0.32 pH units and 0.17 mM O2 in the phycosphere, whereas in the dark the average decreases were 0.10 pH units and 0.03 mM O2, in comparison to bulk seawater. In freshwater algae, the phycosphere pH increased by 1.28 units, whereas O2 increased by 0.38 mM in the light. Equilibrium modeling showed that the pH alteration influenced the chemical species distribution (i.e., free ion, inorganic complexes, and organic complexes) of Al, Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb, Sc, Sm, and Zn in the phycosphere, and the O2 fluctuation increased oxidation rates of Cu(I), Fe(II) and Mn(II) from 2 to 938-fold. The pH/O2-induced changes in phycosphere metal chemistry were larger for freshwater algae than for marine species. Reanalyses of algal metal uptake data in the literature showed that uptake of the trivalent metals (Sc, Sm and Fe), in addition to divalent metals, can be better predicted after considering the phycosphere chemistry.
Zhang Y, Takahashi Y, Hong SP, et al., 2019, High-resolution label-free 3D mapping of extracellular pH of single living cells, Nature Communications, Vol: 10, Pages: 1-9, ISSN: 2041-1723
Dynamic mapping of extracellular pH (pHe) at the single-cell level is critical for understanding the role of H+ in cellular and subcellular processes, with particular importance in cancer. While several pHe sensing techniques have been developed, accessing this information at the single-cell level requires improvement in sensitivity, spatial and temporal resolution. We report on a zwitterionic label-free pH nanoprobe that addresses these long-standing challenges. The probe has a sensitivity >0.01 units, 2 ms response time, and 50 nm spatial resolution. The technology was incorporated into a double-barrel nanoprobe integrating pH sensing with feedback-controlled distance sensing via Scanning Ion Conductance Microscopy. This allows for the simultaneous 3D topographical imaging and pHe monitoring of living cancer cells. These classes of nanoprobes were used for real-time high spatiotemporal resolution pHe mapping at the subcellular level and revealed tumour heterogeneity of the peri-cellular environments of melanoma and breast cancer cells.
Kirby ME, Bullen JC, Hanif MD, et al., 2019, Determining the effect of pH on iron oxidation kinetics in aquatic environments: exploring a fundamental chemical reaction to grasp the significant ecosystem implications of iron bioavailability, Journal of Chemical Education, Vol: 97, Pages: 215-220, ISSN: 0021-9584
Understanding the controls of the oxidation rate of iron (Fe) in oxygenated aquatic systems is fundamental for students of the Earth and Environmental Sciences as it defines the bioavailability of Fe, a trace metal essential for life. The laboratory experiment presented here was successfully developed and used during a third-year undergraduate lab course at Imperial College London for several years. It employs ultraviolet–visible (UV–vis) spectroscopy calibrated externally with 0 to 50 μM Fe2+ standards created in a 492 μM ferrozine and 0.43 M acetate matrix. The students conducted the oxidation experiments in stirred batch reactors at equilibrium with atmospheric oxygen. The solution contained 40.5 μM initial Fe2+ concentration and a 5.1 mM imidazole buffer. The pH was adjusted to values between 7.22 and 7.77. The students observed a pseudo-first-order reaction with respect to Fe2+ concentration. Plotting the logarithms of the apparent rate constants (k′) at different pH values leads to a gradient of 2.2 ± 0.2 min–1 pH–1, indicating a second-order reaction with respect to OH– concentration, in agreement with published literature. The oxidation reaction occurred rapidly (tens of seconds to tens of minutes) indicating that in oxygenated aquatic systems, Fe3+ will be the dominant oxidation state, significantly reducing the bioavailability of Fe. The simple laboratory experiment presented here allows the students to learn about kinetic parameters for a fundamental chemical reaction. It allows the students to explore the significant implications this has for aquatic ecosystems.
Tiam SK, Lavoie I, Liu F, et al., 2019, Diatom Deformities and Tolerance to Cadmium Contamination in Four Species, ENVIRONMENTS, Vol: 6
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- Citations: 3
Liu F, Tan Q-G, Fortin C, et al., 2019, Why Does Cysteine Enhance Metal Uptake by Phytoplankton in Seawater but Not in Freshwater?, Environ Sci Technol, Vol: 53, Pages: 6511-6519
Low-molecular-weight weak ligands such as cysteine have been shown to enhance metal uptake by marine phytoplankton in the presence of strong ligands, but the effect is not observed in freshwater. We hypothesized that these contrasting results might be caused by local cysteine degradation and a Ca effect on metal-ligand exchange kinetics in the boundary layer surrounding the algal cells; newly liberated free metal ions cannot be immediately complexed in seawater by Ca-bound strong ligands but can be rapidly complexed by free ligands at low-Ca levels. The present results consistently support this hypothesis. At constant bulk Cd2+ concentrations, buffered by strong ligands: (1) at 50 mM Ca, cysteine addition significantly enhanced Cd uptake in high-Ca preacclimated euryhaline Chlamydomonas reinhardtii (cultured with cysteine as a nitrogen source to enhance local Cd2+ liberation via cysteine degradation); (2) at 0.07 mM Ca, this enhancement was not observed in the algae; (3) at 50 mM Ca, the enhancement disappeared when C. reinhardtii were cultured with ammonium (to inhibit cysteine degradation and local Cd2+ liberation); (4) cysteine addition did not enhance Cd uptake by cysteine-cultured marine Thalassiosira weissflogii when the concentration of immediately reacting strong ligands was sufficient to complex local Cd2+ liberation.
Liu Q, Zhou L, Liu F, et al., 2019, Uptake and subcellular distribution of aluminum in a marine diatom, ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY, Vol: 169, Pages: 85-92, ISSN: 0147-6513
Liu F, Fortin C, Campbell PGC, 2018, Chemical Conditions in the Boundary Layer Surrounding Phytoplankton Cells Modify Cadmium Bioavailability, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 52, Pages: 7988-7995, ISSN: 0013-936X
Sanchez-Marin P, Liu F, Chen Z, et al., 2018, Microalgal-driven pH changes in the boundary layer lead to apparent increases in Pb internalization by a unicellular alga in the presence of citrate, LIMNOLOGY AND OCEANOGRAPHY, Vol: 63, Pages: 1328-1339, ISSN: 0024-3590
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- Citations: 8
Liu F, Fortin C, Campbell PGC, 2017, Can freshwater phytoplankton access cadmium bound to low-molecular-weight thiols?, LIMNOLOGY AND OCEANOGRAPHY, Vol: 62, Pages: 2604-2615, ISSN: 0024-3590
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- Citations: 8
Aharchaou I, Rosabal M, Liu F, et al., 2017, Bioaccumulation and subcellular partitioning of Cr(III) and Cr(VI) in the freshwater green alga <i>Chlamydomonas reinhardtii</i>, AQUATIC TOXICOLOGY, Vol: 182, Pages: 49-57, ISSN: 0166-445X
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- Citations: 36
Peng X, Liu F, Wang W-X, 2016, Organ-specific accumulation, transportation, and elimination of methylmercury and inorganic mercury in a low Hg accumulating fish, ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY, Vol: 35, Pages: 2074-2083, ISSN: 0730-7268
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- Citations: 45
Liu F, Wang W-X, 2015, Linking trace element variations with macronutrients and major cations in marine mussels <i>Mytilus edulis</i> and <i>Perna viridis</i>, ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY, Vol: 34, Pages: 2041-2050, ISSN: 0730-7268
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- Citations: 24
Rainbow PS, Liu F, Wang W-X, 2015, Metal accumulation and toxicity: The critical accumulated concentration of metabolically available zinc in an oyster model, AQUATIC TOXICOLOGY, Vol: 162, Pages: 102-108, ISSN: 0166-445X
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- Citations: 29
Liu F, Wang W-X, 2014, Differential influences of Cu and Zn chronic exposure on Cd and Hg bioaccumulation in an estuarine oyster, AQUATIC TOXICOLOGY, Vol: 148, Pages: 204-210, ISSN: 0166-445X
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- Citations: 22
Yu X-J, Pan K, Liu F, et al., 2013, Spatial variation and subcellular binding of metals in oysters from a large estuary in China, MARINE POLLUTION BULLETIN, Vol: 70, Pages: 274-280, ISSN: 0025-326X
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- Citations: 46
Liu F, Rainbow PS, Wang W-X, 2013, Inter-site differences of zinc susceptibility of the oyster <i>Crassostrea hongkongensis</i>, AQUATIC TOXICOLOGY, Vol: 132, Pages: 26-33, ISSN: 0166-445X
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- Citations: 29
Liu F, Wang W-X, 2013, Facilitated Bioaccumulation of Cadmium and Copper in the Oyster <i>Crassostrea hongkongensis</i> Solely Exposed to Zinc, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 47, Pages: 1670-1677, ISSN: 0013-936X
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- Citations: 54
Liu F, Wang W-X, 2012, Proteome pattern in oysters as a diagnostic tool for metal pollution, JOURNAL OF HAZARDOUS MATERIALS, Vol: 239, Pages: 241-248, ISSN: 0304-3894
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- Citations: 35
Liu F, Wang D-Z, Wang W-X, 2012, Cadmium-induced changes in trace element bioaccumulation and proteomics perspective in four marine bivalves, ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY, Vol: 31, Pages: 1292-1300, ISSN: 0730-7268
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- Citations: 26
Peng X, Liu F, Wang W-X, et al., 2012, Reducing total mercury and methylmercury accumulation in rice grains through water management and deliberate selection of rice cultivars, ENVIRONMENTAL POLLUTION, Vol: 162, Pages: 202-208, ISSN: 0269-7491
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- Citations: 60
Liu F, Wang W-X, 2011, Metallothionein-like proteins turnover, Cd and Zn biokinetics in the dietary Cd-exposed scallop <i>Chlamys nobilis</i>, AQUATIC TOXICOLOGY, Vol: 105, Pages: 361-368, ISSN: 0166-445X
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- Citations: 17
Liu F, Wang W-X, 2011, DIFFERENTIAL ROLES OF METALLOTHIONEIN-LIKE PROTEINS IN CADMIUM UPTAKE AND ELIMINATION BY THE SCALLOP <i>CHLAMYS NOBILIS</i>, ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY, Vol: 30, Pages: 738-746, ISSN: 0730-7268
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- Citations: 23
Liu F, Tang Y, Du R, et al., 2010, Root foraging for zinc and cadmium requirement in the Zn/Cd hyperaccumulator plant Sedum alfredii, PLANT AND SOIL, Vol: 327, Pages: 365-375, ISSN: 0032-079X
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- Citations: 50
Hu P-J, Qiu R-L, Senthilkumar P, et al., 2009, Tolerance, accumulation and distribution of zinc and cadmium in hyperaccumulator <i>Potentilla griffithii</i>, ENVIRONMENTAL AND EXPERIMENTAL BOTANY, Vol: 66, Pages: 317-325, ISSN: 0098-8472
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- Citations: 80
Liu F, Significance of metal-induced proteins in metal bioaccumulation in marine bivalves and pollution assessment
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