Satellite Tracking Reveals the Speed Up of the Lacustrine Algal Bloom Drift in Response to Climate Change.

Satellite evidence indicates a global increase in lacustrine algal blooms. These blooms can drift with winds, resulting in significant changes of the algal biomass spatial distribution, which is crucial in bloom formation. However, the lack of long-term, large-scale observational data has limited our understanding of bloom drift. Here, we have developed a novel method to track the drift using multi-source remote sensing satellites and presented a comprehensive bloom drift data set for four typical lakes: Lake Taihu (China, 2011-2021), Lake Chaohu (China, 2011-2020), Lake Dianchi (China, 2003-2021), and Lake Erie (North America, 2003-2021). We found that blooms closer to the water surface tend to drift faster. Higher temperatures and lower wind speeds bring blooms closer to the water surface, therefore accelerating drift and increasing biomass transportation. Under ongoing climate change, algal blooms are increasingly likely to spread over larger areas and accumulate in downwind waters, thereby posing a heightened risk to water resources. Our research greatly improves the understanding of algal bloom dynamics and provides new insights into the driving factors behind the global expansion of algal blooms. Our bloom-drift-tracking methodology also paves the way for the development of high-precision algal bloom prediction models.

Degradation of imidacloprid by UV-activated persulfate and peroxymonosulfate processes: Kinetics, impact of key factors and degradation pathway.

UV-activated persulfate (UV/PS) and peroxymonosulfate (UV/PMS) processes as alternative methods for removal of imidacloprid (IMP) were conducted for the first time. The reaction rate constants between IMP and the sulfate or hydroxyl radical were calculated as 2.33×109  or 2.42×1010 M-1 s-1, respectively. The degradation of IMP was greatly improved by UV/PS and UV/PMS compared with only UV or oxidant. At any given dosage, UV/PS achieved higher IMP removal rate than UV/PMS. The pH range affecting the degradation in the UV/PS and UV/PMS systems were different in the ranges of 6-8 and 9 to 10. SO42-, F- and NO3- had no obvious effect on the degradation in the UV/PS and UV/PMS systems. CO32- and PO43- inhibited the degradation of IMP in the UV/PS system, while they enhanced the degradation in the UV/PMS system. Algae organic matters (AOM) were used to consider the impact of the degradation of IMP for the first time. The removal of IMP were restrained by both AOM and natural organic matters. The higher removal rate of IMP demonstrated that both UV/PS and UV/PMS were suitable for treating the water containing IMP, while UV/PS was cost-effective than UV/PMS based on the total cost calculation. Finally, the degradation pathways of IMP were proposed.

Impact of preoxidation of UV/persulfate on disinfection byproducts by chlorination of 2,4-Di-tert-butylphenol.

UV/persulfate (UV/PS) has been as an efficient method to remove many organic contaminants in water. However, little is known about the impact of UV/PS pretrement on the formation of disinfection byproducts (DBPs) during chlorination of 2,4-Di-tert-butylphenol (2,4-D). This research evaluated that UV/PS preoxidation of 2,4-D greatly decreased the DBPs generation during following chlorination. In the 2,4-D solution without any treatment system (O system), trichloromethane (TCM) as the only detected DBP increased with the increase of chlorine dosage. While the formation of TCM declined with the increase of PS dosage in the PS and UV/PS preoxidation systems and decreased the estimated toxicity accordingly. And it was found the residual PS in system could combine free chlorine to further oxidize 2,4-D. And intermediate products were analysed by high-performance liquid chromatography combined with triple quadrupole mass spectroscopy analysis. In the presence of bromine, the bromodichloromethane augmented first and then slowly decreased while dibromochloromethane and tribromethane increased both in O and UV/PS systems with the increase of [Br-]. Bromine substitution was decreased by preoxidation of UV/PS. UV/PS could decrease the total-DBPs formation when used in the real water matrix contained 100 µg/L 2,4-D.

Degradation of diethyl phthalate (DEP) by UV/persulfate: An experiment and simulation study of contributions by hydroxyl and sulfate radicals.

Degradation of diethyl phthalate (DEP) by ultraviolet/persulfate (UV/PS) process at different reaction conditions was evaluated. DEP can be degraded effectively via this process. Both tert-butyl (TBA) and methanol (MeOH) inhibited the degradation of DEP with MeOH having a stronger impact than TBA, suggesting sulfate radical () and hydroxyl radical (HO) both existed in the reaction systems studied. The second-order rate constants of DEP reacting with and HO were calculated to be (6.4±0.3)×107 M-1s-1 and (3.7±0.1)×109 M-1s-1, respectively. To further access the potential degradation mechanism in this system, the pseudo-first-order rate constants (ko) and the radical contributions were modeled using a simple steady-state kinetic model involving and HO. Generally, HO had a greater contribution to DEP degradation than . The ko of DEP increased as PS dosages increased when PS dosages were below 1.9 mM. However, it decreased with increasing initial DEP concentrations, which might be due to the radical scavenging effect of DEP. The ko values in acidic conditions were higher than those in alkaline solutions, which was probably caused by the increasing concentration of hydrogen phosphate (with higher scavenging effects than dihydrogen phosphate) from the phosphate buffer as pH values rose. Natural organic matter and bicarbonate dramatically suppressed the degradation of DEP by scavenging and HO. Additionally, the presence of chloride ion (Cl-) promoted the degradation of DEP at low Cl- concentrations (0.25-1 mM). Finally, the proposed degradation pathways were illustrated.

Degradation of diclofenac by UV-activated persulfate process: Kinetic studies, degradation pathways and toxicity assessments.

Diclofenac (DCF) is the frequently detected non-steroidal pharmaceuticals in the aquatic environment. In this study, the degradation of DCF was evaluated by UV-254nm activated persulfate (UV/PS). The degradation of DCF followed the pseudo first-order kinetics pattern. The degradation rate constant (kobs) was accelerated by UV/PS compared to UV alone and PS alone. Increasing the initial PS dosage or solution pH significantly enhanced the degradation efficiency. Presence of various natural water constituents had different effects on DCF degradation, with an enhancement or inhibition in the presence of inorganic anions (HCO3- or Cl-) and a significant inhibition in the presence of NOM. In addition, preliminary degradation mechanisms and major products were elucidated using LC-MS/MS. Hydroxylation, decarbonylation, ring-opening and cyclation reaction involving the attack of SO4•- or other substances, were the main degradation mechanism. TOC analyzer and Microtox bioassay were employed to evaluate the mineralization and cytotoxicity of solutions treated by UV/PS at different times, respectively. Limited elimination of TOC (32%) was observed during the mineralization of DCF. More toxic degradation products and their related intermediate species were formed, and the UV/PS process was suitable for removing the toxicity. Of note, longer degradation time may be considered for the final toxicity removal.

Adsorption and removal of clofibric acid and diclofenac from water with MIEX resin.

This study demonstrates the use of MIEX resin as an efficient adsorbent for the removal of clofibric acid (CA) and diclofenac (DCF). The adsorption performance of CA and DCF are investigated by a batch mode in single-component or bi-component adsorption system. Various factors influencing the adsorption of CA and DCF, including initial concentration, contact time, adsorbent dosage, initial solution pH, agitation speed, natural organic matter and coexistent anions are studied. The Langmuir model can well describe CA adsorption in single-component system, while the Freundlich model gives better fitting in bi-component system. The DCF adsorption can be well fitted by the Freundlich model in both systems. Thermodynamic analyses show that the adsorption of CA and DCF is an endothermic (ΔH(o) > 0), entropy driven (ΔS(o) > 0) process and more randomness exists in the DCF adsorption process. The values of Gibbs free energy (ΔG(o) < 0) indicate the adsorption of DCF is spontaneous but nonspontaneous (ΔG(o) > 0) for CA adsorption. The kinetic data suggest the adsorption of CA and DCF follow the pseudo-first-order model in both systems and the intra-particle is not the unique rate-limiting step. The adsorption process is controlled simultaneously by external mass transfer and surface diffusion according to the surface diffusion modified Biot number (Bis) ranging from 1.06 to 26.15. Moreover, the possible removal mechanism for CA and DCF is respectively proposed based on the ion exchange stoichiometry.

Characteristics of C-, N-DBPs formation from algal organic matter: role of molecular weight fractions and impacts of pre-ozonation.

Extracellular organic matter (EOM) and intracellular organic matter (IOM) of Microcystis aeruginosa have been reported to contribute to the formation of carbonaceous disinfection by-products (C-DBPs) and nitrogenous disinfection by-products (N-DBPs). Little is known about DBPs formation from different molecular weight (MW) fractions, especially for N-nitrosodimethylamine (NDMA). This study fractionated EOM and IOM into several MW fractions using a series of ultrafiltration membranes and is the first to report on the C-DBPs and N-DBPs formation from chlorination and chloramination of different MW fractions. Results showed that EOM and IOM were mainly distributed in low-MW (<1 KDa) and high-MW (>100 KDa) fractions. Additionally, the low-MW and high-MW fractions of EOM and IOM generally took an important part in forming C-DBPs and N-DBPs, either in chlorination or in chloramination. Furthermore, the effects of pre-ozonation on the formation of DBPs in subsequent chlorination and chloramination were also investigated. It was found that ozone shifted the high-MW fractions of EOM and IOM into lower MW fractions and increased the C-DBPs and N-DBPs yields to different degrees. As low-MW fractions are more difficult to remove than high-MW fractions by conventional treatment processes, therefore, activated carbon adsorption, nanofiltration (NF) and biological treatment processes can be ideal to remove the low-MW fractions and minimize the formation potential of C-DBPs and N-DBPs. Moreover, the use of ozone should be carefully considered in the treatment of algal-rich water.

Chlorination and chloramination of tetracycline antibiotics: disinfection by-products formation and influential factors.

Formation of disinfection by-products (DBPs) from chlorination and chloramination of tetracycline antibiotics (TCs) was comprehensively investigated. It was demonstrated that a connection existed between the transformation of TCs and the formation of chloroform (CHCl3), carbon tetrachloride (CCl4), dichloroacetonitrile (DCAN) and dichloroacetone (DCAce). Factors evaluated included chlorine (Cl2) and chloramine(NH2Cl) dosage, reaction time, solution pH and disinfection modes. Increased Cl2/NH2Cl dosage and reaction time improved the formation of CHCl3 and DCAce. Formation of DCAN followed an increasing and then decreasing pattern with increasing Cl2 dosage and prolonged reaction time. pH affected DBPs formation differently, with CHCl3 and DCAN decreasing in chlorination, and having maximum concentrations at pH 7 in chloramination. The total concentrations of DBPs obeyed the following order: chlorination>chloramination>pre-chlorination (0.5h)>pre-chlorination (1h)>pre-chlorination (2h).

Effect of chlorine dioxide on cyanobacterial cell integrity, toxin degradation and disinfection by-product formation.

Bench scale tests were conducted to study the effect of chlorine dioxide (ClO2) oxidation on cell integrity, toxin degradation and disinfection by-product formation of Microcystis aeruginosa. The simulated cyanobacterial suspension was prepared at a concentration of 1.0×10(6)cells/mL and the cell integrity was measured with flow cytometry. Results indicated that ClO2 can inhibit the photosynthetic capacity of M. aeruginosa cells and almost no integral cells were left after oxidation at a ClO2 dose of 1.0mg/L. The total toxin was degraded more rapidly with the ClO2 dosage increasing from 0.1mg/L to 1.0mg/L. Moreover, the damage on cell structure after oxidation resulted in released intracellular organic matter, which contributed to the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) as disinfection by-products. Therefore, the use of ClO2 as an oxidant for treating algal-rich water should be carefully considered.

Characterization of algal organic matters of Microcystis aeruginosa: biodegradability, DBP formation and membrane fouling potential.

Algal organic matters (AOM), including extracellular organic matters (EOM) and intracellular organic matters (IOM), were comprehensively studied in terms of their biodegradability, disinfection byproduct (DBP) formation potentials and membrane fouling. EOM and IOM were fractionated into hydrophobic (HP), transphilic (TP) and hydrophilic (HL) constituents. The HP, TP and HL fractions of EOM and IOM were highly biodegradable with BDOC/DOC ranging from 52.5% to 67.4% and the DBP formation potentials followed the order of HP > TP > HL, except of IOM-HL. Biodegradable process proved very effective in removing the DBP formation potentials. Moreover, the AOM characteristics were also evaluated during ultrafiltration (UF) treatment. Results demonstrated that UF favourably remove DOC and DBP formation potential of IOM than those of EOM. And the HL constituents played a more important role in membrane fouling than HP and TP. The UF foulants exhibited higher BDOC/DOC than AOM, suggesting EOM and IOM might enhance biofouling because more biodegradable proteins and polysaccharides were found in membrane foulants. Therefore, appropriate biological treatment, ultrafiltration, or combination of the both are potential options to address these algae-caused water quality issues.

Influence of hydrophobic/hydrophilic fractions of extracellular organic matters of Microcystis aeruginosa on ultrafiltration membrane fouling.

Fouling is a major obstacle to maintain the efficiency of ultrafiltration-based drinking water treatment process. Algal extracellular organic matters (EOMs) are currently considered as one of the major sources of membrane fouling. The objective of this study was to investigate the influence of different hydrophobic/hydrophilic fractions of EOM extracted from Microcystis aeruginosa on ultrafiltration membrane fouling at lab scale. The experimental data indicated that EOM exhibited similar flux decline trends on polyethersulfone (PES) and regenerated cellulose (RC) membranes but caused greater irreversible fouling on PES membrane than RC membrane due to its hydrophobic property. It was also observed that charged hydrophilic (CHPI) and neutral hydrophilic (NHPI) fractions caused greater flux decline over hydrophobic (HPO) and transphilic (TPI) fractions. For PES membrane, the order of the irreversible fouling potentials for the four fractions was HPO>TPI>CHPI>NHPI, while the irreversible fouling potentials of RC membrane were tiny and could be ignored. Fluorescence excitation-emission matrix (EEM) spectra and Fourier transform infrared (FTIR) spectra suggested that protein-like, polysaccharide-like and humic-like substances were the major components responsible for membrane fouling. The results also indicated that the irreversible fouling increased as the pH decreased. The addition of calcium to feed solutions led to more severe flux decline and irreversible fouling.

CoFe2O4 magnetic nanoparticles as a highly active heterogeneous catalyst of oxone for the degradation of diclofenac in water.

A magnetic nanoscaled catalyst cobalt ferrite (CoFe2O4) was successfully prepared and used for the activation of oxone to generate sulfate radicals for the degradation of diclofenac. The catalyst was characterized by transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The effects of calcination temperature, initial pH, catalyst and oxone dosage on the degradation efficiency were investigated. Results demonstrated that CoFe2O4-300 exhibited the best catalytic performance and almost complete removal of diclofenac was obtained in 15 min. The degradation efficiency increased with initial pH decreasing in the pH range of 5-9. The increase of catalyst and oxone dosage both had the positive effect on the degradation of diclofenac. Moreover, CoFe2O4 could retain high degradation efficiency even after being reused for five cycles. Finally, the major diclofenac degradation intermediates were identified and the primary degradation pathways were proposed.

Effects of different algaecides on the photosynthetic capacity, cell integrity and microcystin-LR release of Microcystis aeruginosa.

Bench scale tests were conducted to study the effects of four common algaecides, including copper sulfate, hydrogen peroxide, diuron and ethyl 2-methylacetoacetate (EMA) on the photosynthetic capacity, cell integrity and microcystin-LR (MC-LR) release of Microcystis aeruginosa. The release of potassium (K(+)) from cell membrane during algaecide exposure was also analyzed. The three typical photosynthetic parameters, including the effective quantum yield (Фe), photosynthetic efficiency (α) and maximal electron transport rate (rETRmax), were measured by a pulse amplitude modulated (PAM) fluorometry. Results showed that the photosynthetic capacity was all inhibited by the four algaecides, to different degrees, by limiting the energy capture in photosynthesis, and blocking the electron transfer chain in primary reaction. For example, at high diuron concentration (7.5 mg L(-1)), Фe, α and rETRmax decreased from 0.46 to 0.19 (p<0.01), from 0.20 to 0.01 (p<0.01) µmol electrons m(-2) s(-1)/µmol photons m(-2) s(-1), and from 160.7 to 0.1 (p<0.001) µmol m(-2) s(-1) compared with the control group after 96 h of exposure, respectively. Furthermore, the increase of algaecide dose could lead to the cell lysis, as well as release of intracellular MC-LR that enhanced the accumulation of extracellular MC-LR. The order of MC-LR release potential for the four algaecides was CuSO4>H2O2>diuron>EMA.

Inequality and polarization analysis of urban water use in the Yangtze River Delta area, China.

Inequality and polarization are terms usually used to describe the overall dispersion of income distribution and the phenomenon of a divided society with a disappearing middle class and increasing rich and poor populations. However, these terms have seldom been used in water sciences. In this paper, the concepts of inequality and polarization are employed to analyze the distribution of urban water use of different cities. Using for reference the conception of Gini coefficient, the EUWU (Equality of Urban Water Use) model is built to analyze the equality of urban water use. And, the PUWU (Polarization of Urban Water Use) model based on exponential functions, which can limit the index of polarization to the range (0, 1) effectively, is built to analyze the polarization of urban water use. Inequality and polarization of resident, industrial and commercial water use in 16 cities in the Yangtze River Delta, the fastest growing region of China, are evaluated using the EUWU model and PUWU model, respectively. The results show that inequality of residential, industrial and commercial water use has decreased by 6.5%, 11.2% and 8.4%, while the index of polarization has increased by 3.9%, 3.8% and 0.1% in Yangtze River Delta area from 2001 to 2006.