2008 Progress Report: Monitoring, Photochemical Fate, and Oxidative Degradation by UV and Solar-based Catalytic Technologies of Cyanotoxins in Freshwater Estuaries

EPA Grant Number: R833223
Title: Monitoring, Photochemical Fate, and Oxidative Degradation by UV and Solar-based Catalytic Technologies of Cyanotoxins in Freshwater Estuaries
Investigators: Dionysiou, Dionysios D. , Deis, Donald R. , Miller, Cheryl L. , O'Shea, Kevin , Westrick, Judy
Institution: University of Cincinnati , Florida International University , Lake Superior State University , PBS&J
Current Institution: University of Cincinnati , Florida International University , Green Water Laboratories/CyanoLab , Lake Superior State University , PBS&J
EPA Project Officer: Klieforth, Barbara I
Project Period: April 1, 2007 through March 31, 2010
Project Period Covered by this Report: April 1, 2008 through March 31,2009
Project Amount: $679,589
RFA: Development and Evaluation of Innovative Approaches for the Quantitative Assessment of Pathogens in Drinking Water (2005) RFA Text |  Recipients Lists
Research Category: Drinking Water , Water

Objective:

The specific objectives of the proposal are to: (1) evaluate the photolytic degradation of microcystins along a salinity and dissolved organic carbon (DOC) gradient and identify the fate and partitioning of microcystins in the estuarine portion of the lower St. Johns River in Florida and several locations in the Great Lakes; (2) investigate the mechanisms of the photo-transformations of cyanotoxins present in synthetic solutions and samples from the Great Lakes and Florida by visible and solar irradiation; (3) explore solar-driven catalytic systems for the destruction of cyanotoxins in water; and (4) investigate the fate of cyanotoxins under germicidal action UV (254 nm) (low pressure lamps) or broader spectrum (medium pressure lamps) at various levels of UV fluence in consideration with the presence of UV disinfection systems in several drinking water treatment plants.

Progress Summary:

Task 1. Monitoring of Harmful Algal Blooms (HAB) and Sampling in the Great Lakes.
 
 Activities and Findings: Five utilities were selected for the 2008 Great Lakes Monitoring Study. Two utilities on Lake Michigan, one utility on Lake Erie, one utility on Lake Huron, and one on Lake St. Clair. These utilities were selected based on plant cyanobacteria data, taste and odor events, and occurrence of cyanobacteria blooms.  Table 1 describes the drinking water utilities.
 
Table 1: Drinking Water Utilities 2008 Study
 
Lake
Location
Treatment
Intake Depth
Algae Data
Michigan I
Lake Bluff, IL
3,000 ft off shore
KMnO4 intake, conventional treatment with ozone, UV and chlorine
25 ft
Yes 
Michigan II
Wyoming
4,440 ft off shore
Conventional
40-50 ft
Yes - not received yet
Erie I
Cleveland, Baldwin Plant
41.54844219,      -81.7504091
Conventional treatment, free chlorine for primary and secondary disinfection, pre-oxidation with potassium permanganate, and powdered activated carbon for taste and odor control
10-25 ft
Yes - will send later
Huron I
Saginaw Bay
2 miles off shore
Source feeds in two storage reservoir, conventional treatment
45 ft
Yes
Huron II
Bay City
Latitude: 43.71N, Longitude: 83.90 W
Ozone, lime softening, conventional treatment
17 ft
Yes
Lake St. Clair
IRA
1,650 ft from the nearest road
Package plant with up flow clarifier filter mix media
6 ft
None
 
 
Results: The utilities were very responsible at grabbing and mailing their samples to LSSU.  Huron I utility removed themselves from the study a week before the sampling was to begin.  Although all Great Lake sampling periods were mid summer to early fall, the start and finishing dates were utility specific (Table 2). Temperature, pH and turbidity were water quality parameters that were reported by the utility (Table 3). Of the 43 samples collected from the Great Lakes, 5 tested positive for microcystin (Table 4). Three variants of microcystin were reported, MCY LR, RR and YR. Microcystin LR was reported in Lake Michigan, Lake Erie, and Lake Huron, whereas MCY RR and YR were reported in Lake Huron. None of the Great Lake samples were above 1 ppb microcystin. Cylindrospermopsis was found in both Lakes Michigan and Erie. Although Microcystis was in each of the study lakes, its concentration was very low in all waters except Huron. Other toxin producing genera included Anabaenopsis, Anabaena, Oscillitoria, and Aphanizomenon
Three Midwestern lakes were included in this study; Muskegon Lake, MI, Mona Lake, MI and Budd Lake, MN. High levels of microcystin have been reported on each of these lakes. These lakes were added to the study to increase the likelihood of sampling a toxic cyanobacteria bloom. The only samples above 1 ppb microcystin were collected from Mona and Muskegon Lakes. Microcystin LR and YR were quantified from these southwestern Michigan lakes.   
 
Table 2: Summary of the 2008 Study Logistics
Lake
Start Date
Stop Date
Samples Taken
Samples Analyzed
Michigan I
7/9/08
9/02/08
6
6
Michigan II
7/9/08
8/27/08
7
7
Erie I
6/25/08
9/10/08
12
12
Huron I
Withdrew from the study before sampling started
Huron II
6/24/08
9/15/08
13
12
Lake  St. Clair
7/22/08
9/12/08
6
6
Muskegon Lake
7/22/08
8/02/08
3
3
Mona Lake
7/22/08
7/22/08
1
1
Budd Lake
 
 
2
2
 
Table 3: Water Quality Summary
Lake
Temperature
pH
Turbidity
# of positive source samples
Dominant cyanobacteria
Michigan I
13-22oC
7.8-8.4
0.7-2.2 NTU
0
None,<100 cells/mL
Michigan II
9-20oC
7.4-8.6
0.4-1.6 NTU
1
None, <100 cells/mL
Erie I
21-26oC
7.5-8.4
0.5-1.4 NTU
2
None, <100 cells/mL
Huron I
Withdrew from the study before sampling started
Huron II
20-25oC
7.8-8.6
4.2-14.5 NTU
2
Microcystis, 9,500-1000 cells/mL
Lake St. Clair
20-24oC
7.4-8.8
1.5-3.1 NTU
0
None, 105 cells/mL
Muskegon Lake
26-27oC
8.8-9.2
70.2, 69.1- 266, 269
3
N/A
Mona Lake
N/A
N/A
N/A
1
N/A
Budd Lake
N/A
N/A
N/A
2
Aphanizomenon, 50,149 cells/mL
 
 
Table 4: Summary of Positive Analyses
Sample Name
Date Taken
Algal Toxin Concentration (ug/L)
Sent to UoC
 

 

 
 
MCY-LR
MCY-YR
MCY-RR
 
Lake Erie
7/16/2008
0.56
 
 
XX
Lake Erie
7/23/2008
0.59
 
 
 
Lake Michigan II
7/23/2008
0.51
 
 
 
Huron II
7/28/2008
0.54
0.47
 
XX
Huron II
8/11/2008
0.33
 
0.27
 
Muskegon Lake Mix 001
7/22/2008
59
13 
 
XX
Mona Lake Ross Park 001
7/22/2008
11
10
 
XX
 
Each of the selected utilities had taste and odor events, shortening of filter runs, and algae problems. Lakes Erie, Michigan, and Huron had low level of microcystin in their source waters. Microcystin LR was reported in Lakes Erie, Michigan and Huron, whereas microcystin YR and RR were reported only in Lake Huron.  Muskegon and Mona Lakes had high levels of both microcystin LR and YR.
 
Liquid Chromatography/Tandem-Mass Spectrometry (LC/MS/MS) is a powerful tool for the analysis of various analytes in a wide variety of matrices. What is especially attractive about LC/MS/MS is its sensitivity and selectivity. Microcystins, in particular, represent an emerging class of cyanotoxins of concern to the drinking water industry. Recognizing the potential health risk, the World Health Organization, Australia, and Brazil have established guidelines for the amount of microcystins permissible in drinking water (specifically microcystin LR). Recently, the United States has begun to evaluate the occurrence, health effects, and susceptibility of water treatment of cyanotoxins. The Environmental Protection Agency (EPA) added freshwater cyanotoxins to its Contaminant Candidate List (CCL).  The use of smaller column media (sub 2μm particles) to both improve the selectivity, speed, sensitivity and resolution to screen for many of these toxins (microcystins, anatoxin-a, and cylindrospermopsin) using Ultra-Performance Liquid Chromatography (UPLC®) combined with tandem mass spectrometry was investigated.  Specific examples, including data from the recent Ohio River cyanobacteria bloom in August, 2008, were presented in the study (Note appendix A for publication details).
 
Task 2. Monitoring of HABs and Photochemical Effects in St. Johns River in Florida
 
Activities and Findings: GreenWater Laboratoires/CyanoLab has completed data collection for 2008. No significant toxin producing blooms were observed or reported in the St. Johns River (SJR) during the sampling period (April-November, 2008).
 
Sampling for 2009, in conjunction with the St. Johns River Water Management District, will be initiated in May of 2009 and will be continued through December of 2009.
 
Results:  Four positive microcystin samples were delivered to the USEPA (Dr. D. Dionysiou and Dr. A. de la Cruz) for chemical degradation experimentation. Two samples were considered to contain low levels of microcystins (< 4 ug/L), one sample with moderate levels of microcystin present (50 ug/L) and one sample with high concentrations of microcystin present (3,200 ug/L). Dr. K. O’Shea at Florida International University (FIU) was not sent the two low level microcystin water samples but was sent the moderate and high level water samples. Water samples from the St. Johns River were not sent for testing and further experimentation as microcystin levels were never analyzed to be greater than 2 ug/L. The moderate and high concentration samples were collected from California and Maryland, respectively. Water quality testing was routinely obtained for four sample stations (Crescent Lake, the SJR at Palatka, the SJR at the Shands Bridge and Doctors Lake) from June – November of 2008. These four stations were selected because they provided representative water quality from south to north, across salinity gradients (0.5 – 5.0 ppt) where cyanobacteria may be transported via tides and wind action and are known locations for microcystin production.
 
In 2009, sample collection and analysis will continue. In 2008, samples were collected and analyzed on a monthly basis.  In 2009, depending on the prevalence of microcystin producing cyanobacteria, samples will be collected twice monthly and analyzed in hopes of the increased frequency of analysis being able to better identify strong positive samples (> 10 ug/L).  Samples collected from outside the confines of the SJR will still be identified and supplied as a source of microcystin in surface waters for the USEPA and FIU. Water quality monitoring will also be continued.
 
Sample and data collection has not been initiated for 2009. GreenWater Laboratories/CyanoLab has communicated with Mr. John Hendrickson and Robert Burks at the St. Johns River Water Management District for collaborative bi-monthly sampling activities on the SJR for June–October of 2009. Mr. Johns Higman, also of the SJRWMD, has also re-confirmed the potential to sample bivalves during the 2009 sampling period.
 
Task 3. Fundamental Studies on the Photochemical Fate and Transformation of Cyanotoxins.
 
Activities and Findings: A crude solution containing cylindrospermosin (CYN) was obtained from the biomass of a lyophilized culture using solid phase extraction and ion exchange. One-two grams of cell biomass were dissolved in the 50 mLs of 90% methanol, then sonication for 2 mins. The resulting solution was centrifuged at 6000 rpm for 30 min, and then the supernatant passed through 10g C18 cartridge. The solution was decanted and concentrated using SpeedVac to 2-3 mLs. The crude isolates were subjected to preparative HPLC and three peaks elute with the strong absorption ~ 262 nm characteristic of CYN. Injection volume was 0.5 mL eluant was water;MeOH gradient increasing to 40% MeOH after 15 mins at a flow rate of 10ml/min. Several peaks appear with CYN-type absorbance characteristics were observed. Each of the peaks was collected and analyzed by HPLC and the chromatographic behavior compared to an authentic sample of CYN. One of the peaks exhibited the same retention time and absorption maxima as the authentic CYN standard. MS analysis further confirmed CYN was isolated in high purity ~ 90-95%. The remaining CYN-like isolates will be further analyzed and tested for biological activity. We have isolated ~ 5 mg and conducted a variety of irradiation experiments. While ultrasonic and UV treatment of CYN leads to only show degradation, but UV TiO2 photocatalysis lead to the rapid degradation of CYN. The degradation of CYN by UV light in the presence of humic materials is strongly inhibited. The addition of hydroxyl radical scavengers during the photolytic treatment of CYN indicates that hydroxyl radical is the primary oxidant during TiO2 photocatalysis and ultrasonic treatment. We continue to isolate CYN, but have a limited quantity of biomass. We expect to obtain ~ 10 mg to conduct detailed kinetic studies on the reaction of hydroxyl radical with CYN.  Radiolysis methods and competitive kinetics will be employed for the kinetic studies. The fundamental parameters obtained from the kinetic studies are critical for the evaluation of photochemical and hydroxyl radical based technologies for the destruction of CYN. The reactivity of CYN towards hydroxyl radical is also critical to understanding the fate and photochemical transformation of CYN in natural waters. While limited by the cost and small amounts of CYN we will attempt product studies using LC/MS and assess the biological activities of the treated solutions as a function of treatment times. 
Results:  Studies have been conducted on the TiO2 photocatalytic oxidation (PCO) of domoic acid (DA), a potent marine toxin. TiO2 photocatalysis is an effective method for degradation of high concentrations of DA in relatively short treatment times. Our study conducted in the presence of variety of scavengers provides a better understanding of oxidants involved in TiO2 PCO degradation. The experiments suggest that .OH/h+VB play key roles in DA degradation during TiO2 photocatalysis. The role of oxygen seems to be primarily as an electron scavenger and a variety of alternative electron scavengers could be used. Superoxide anion radical mediated oxidation may lead to the degradation but it is slow and not required for TiO2 PCO of DA. The pH plays an important role in adsorption and reactivity of DA. The strongest adsorption and thus reactivity is observed at pH 4.5 based on the electrostatic forces between DA and TiO2. It might not be practical to apply TiO2 photocatalysis in the marine waters due to the vast area involved, non-selective, rapid oxidation and complex nature of matrix involved, but it may be applicable for purification of sea water for household, industrial, and drinking purposes. 
 
We have also completed a series of experiments investigating the destruction of DA using a photosensitizer under visible light irradiation. Control experiments conducted with an argon-saturated solution show no degradation of DA in the presence of a sensitizer, while under oxygen saturation rapid degradation is observed. These results indicate singlet oxygen is responsible for the degradation. Singlet oxygen is generated photochemically via energy transfer from the excited sensitizer to molecular oxygen.  Singlet oxygen in turn reacts with domoic acid. A variety of sensitizers are present in natural surface water, i.e., chlorophylls, pigments, and humic materials, and our results suggest singlet oxygen may play an important role of the fate of DA. We are conducting product studies for the reactions of singlet oxygen with domoic acid using NMR. Based on the preliminary peak assignments it appears singlet oxygen reacts almost exclusively at the diene moiety of DA. The proton NMR studies clearly illustrate a variety of products are formed including an aldehyde product. The aldehyde product appears to be the result of oxidative cleavage of the tri-substituted double bond in the diene. There are a number of peaks that suggest the formation of endoperoxide product.
 
Our radiolysis studies on MC-LR clearly indicate the major reaction site for hydroxyl radical is the Adda amino acid. The transient absorbance measurements and kinetic studies further indicate hydroxyl radical attacks the benzene ring and diene of Adda side chain as the major degradation pathways accounting for ~ 67 % of the products. Since nodularin and microcystins variants possess the reactive Adda moiety, all these toxins should be readily degraded by hydroxyl radical. The Adda side chain is also critical to the toxicity of these compounds and oxidative degradation has been shown to dramatically reduce or eliminate the biological activity or toxicity of these compounds. All MC variants and nodularin possess the Adda moiety and thus should be readily destroyed via hydroxyl radical mediated oxidation. The estimation of the hydroxyl radical reactivity towards MC-LR is correctly modeled using the individual reactivities of the specific functional groups and amino acids. The summation of individual kinetic contributions may provide a simple method for predicting the hydroxyl radical reactivity for different MCs (> 80 variants) and used to effectively determine the partitioning of hydroxyl radical reactions among the different amino acid components. While extension of this type of kinetic evaluation would be useful to assess hydroxyl radical destruction of peptides and proteins, an array of polypeptide substrates must be investigated to determine its general applicability. Our kinetic and mechanistic data provide a quantitative foundation for the initial evaluation of AOP efficiency in removing MC-LR from real-world waters, which can contain high levels of dissolved natural organic matter (NOM) and other hydroxyl radical scavengers.
 
TiO2 photocatalysis leads to the rapid degradation of the problematic marine toxins, brevetoxins (PbTxs), in aqueous and organic media. The degradation was fastest under UV irradiation, but solar irradiation also leads to the destruction of PbTxs. The degradation follows a first-order kinetic type process and hydroxyl radical seems to play a major role in degradation of PbTxs. Although the biological activity of the treated solution did not directly parallel the PbTx concentration, the toxicity of PbTx solution measured by ELISA was dramatically reduced during TiO2 photocatalysis. Humic substances and the components (ions) of seawater reduce the efficiency of the TiO2 photocatalytic degradation, but significant degradation is still observed. It is not practical to treat large bodies of marine water with TiO2 photocatalysis, but it may be feasible to treat a heavily populated stretches of beach, a shellfish collection area, or a popular recreation site in an attempt to mitigate the human heath effects of PbTxs. We envision a treatment process would require the attachment of the photocatalyst to a floating substrate (glass beads). The floating substrates could be applied and will be maintained at the surface where the concentrations of the PbTxs are highest in the SML, the solar flux is greatest, and inhibitory effects of ions and humic substances below the SML will have a reduced effect.
 
Task 4. Exploring Nitrogen-Contain Surfactants for the Synthesis of TiO2-xNx
 
Activities and Findings:  During the second year of the project, we conducted several research activities. The first study focused on the development of highly efficient visible light-activated nitrogen and fluorine co-doped TiO2 (NF-TiO2) nanoparticles and films with enhanced structural properties and functionalities using a modified sol-gel method for the degradation of microcystin-LR (MC-LR). The mechanistic aspects of the degradation of the cyanotoxin MC-LR during treatment with thin and thick TiO2 photocatalytic films were determined in the second study; focused on the identification of the reaction intermediates formed during treatment. Most of these reaction intermediates have not been previously reported mainly because of differences in the experimental conditions. We utilized tandem mass spectroscopy (MS/MS) for the elucidation of possible structures for the intermediates. In the third study, we tested the effects of different operational parameters such as initial solution pH and concentration, and changes in the structural properties of the films (porosity, crystallinity and thickness) on the degradation rate of MC-LR with thin transparent UV-activated TiO2 photocatalytic films as an efficient technology for the degradation and detoxification of water contaminated with the cyanotoxin MC-LR. The toxicity of the treated samples was evaluated by an in-house protein phosphatase 1 assay and indicated that treatment with the TiO2 photocatalytic films indeed resulted in complete removal of MC-LR toxicity. Finally, the use of germicidal UV/H2O2 to degrade MC-LR was investigated.
Results:  In one of the studies, we developed nonmetal-doped TiO2 nanoparticles (NF-TiO2) by a novel synthesis route employing a simple sol–gel method containing a nonionic fluorosurfactant as pore template material to tailor-design the structural properties of TiO2 and fluorine dopant as well as ethylenediamine as nitrogen source for the photocatalytic response towards visible light. The synthesized photocatalyst was characterized by XRD, UV–vis spectroscopy, XPS, HR-TEM, ESEM and porosimetry measurements. The resulting nanoparticles exhibited enhanced structural properties such as high surface area (141 m2/g), high porosity (49%), mesoporous structure (2–10 nm pore size) and low degree of agglomeration (1.07). A reduction in the effective band gap (2.75 eV) was observed compared with reference TiO2 (3.00 eV) due to the red-shift in the optical absorption spectrum of the nonmetal-doped TiO2 photocatalyst. We also focused on the environmental application of the prepared nanoparticles for the destruction of microcystin-LR (MC-LR) under visible light irradiation (l > 420 nm). Under acidic conditions (pH 3.0 ± 0.1), the highest MC-LR degradation rate was achieved with N-F-TiO2. The electrostatic interactions between the toxin and the NF codoped TiO2 favored the photocatalytic degradation. Beneficial effects induced by codoping with nitrogen and fluorine are responsible for higher photocatalytic activity than TiO2 nanoparticles with only fluorine or nitrogen doping. Also, commercially available visible light-activated TiO2 showed lower degradation rate per unit surface area of the material. (Note appendix B for publication details). For the synthesis of NF-TiO2 films, we employed the same sol-gel method with different surfactant ratios to enhanced the adhesion, among other morphological properties, of NF-TiO2 in the glass support, as well as vary the film thickness and photocatalytic activity of the nanofilm. We characterized the synthesized NF-TiO2 film with Micro-Raman spectroscopy, electron paramagnetic resonance and hydrophilicity techniques; in addition to the same analytical techniques employed for the NF-TiO2 nanoparticles. We compared their photocatalytic activity, under visible radiation, with reference TiO2 and modified-P25 TiO2 films. High degradation efficiencies were obtained for MC-LR and no irreversible changes of the catalyst occurred since very similar degradation rates are obtained when reutilizing the catalyst after 3 times.
 
Mass spectrometry was utilized for structural identification of the intermediates formed during the photocatalytic degradation of the cyanotoxin, microcystin-LR with immobilized TiO2 photocatalysts at neutral pH. Most of the intermediates reported herein have not been found in prior studies. Results indicate that MC-LR degradation is initiated at four sites of the toxin; three on the Adda amino acid (aromatic ring, methoxy group, and conjugated double bonds) and one on the cyclic structure (Mdha amino acid). Several intermediates gave multiple peaks in the TIC (m/z) 1011.5, 1029.5, 1063.5), which were deduced to be geometrical or constitutional isomers. This is the first study that reports the hydroxylation of the aromatic ring and the demethoxylation of MC-LR with TiO2 photocatalysis. The most targeted site was the conjugated diene bonds because of their location in the MC-LR structure. Isomerization at the C4-C5 and C6-C7 of the diene bond of the Adda chain was a direct result of hydroxyl radical addition/substitution. Based on the above, we concluded that oxidation and isomerization of the diene bonds of MC-LR occurred simultaneously. Other steps included hydroxyl substitution, further oxidation, and bond cleavage. As the reaction time progressed, simultaneous oxidation of the Adda chain and the cyclic structure occurred. (Note appendix C for publication details).
 
A different study investigated the use of thin transparent TiO2 photocatalytic films, prepared with novel sol-gel methods containing surfactants as templating materials, for the degradation of the cyanotoxin, microcystin-LR (MC-LR). MC-LR is an emerging contaminant from the Contaminant Candidate Lists (CCLs 1-3) of the USEPA. The effects of UV-A radiation, solution pH, initial toxin concentration, coated surface area of the TiO2 films and their structural properties (porosity, crystallinity and thickness) on the degradation rate of MC-LR were investigated. Photolysis did not occur with UV-A radiation. Acidic pH was more efficient for the degradation of MC-LR due to toxin interaction with the catalyst surface and increased adsorption into the porous films. The degradation profiles of the toxin at different initial concentrations were fitted with pseudo-first order kinetics. Films prepared with three coatings (0.3 μm thickness) had the best performance at acidic and neutral pH, while the exclusion of surfactant from the preparation method resulted in non-porous films with decreased performance. The parameter that mostly affected the degradation rate was the solution pH. The toxicity of the treated samples, evaluated by an in-house protein phosphatase 1 assay, indicated that treatment with the TiO2 photocatalytic films indeed resulted in complete removal of MC-LR toxicity. A manuscript on the results has been accepted for publication in Applied Catalysis B: Environment (Note appendix D for publication details).
 
Nowadays, we are studying the role of water parameters on the degradation MC-LR, such as natural organic matter (NOM), alkalinity and ionic strength. Preliminary findings suggest that the presence of ions scavenge the photocatalytic activity of the NF-TiO2 catalyst. However, the presence of NOM enhanced the degradation rate of MC-LR indicating that NOM may act as photosensitizer under visible light when codoped TiO2 is present. These results will provide us fundamental understanding when dealing with real water from contaminated sources.
 
In the last part, the degradation of MC-LR by UV/H2O2 process in a collimated beam system was carried out. The UV dose was measured by KI/KIO3 actinometry and verified by ferrioxalate actinometry and radiometer (XRD (XRL) 140T254 Low Profile Germicidal Probe and IL1700 detector). The results showed that the addition of H2O2 greatly increase the degradation rate of MC-LR. At lower H2O2 concentrations, (below 24 mg/L), the rate increases linearly, while excess amounts of H2O2 scavenges the reaction of hydroxyl radicals with MC-LR (Figure 1). Variations of initial MC-LR concentration were performed at three different initial H2O2 concentrations, 10 mg/L, 24 mg/L and 48 mg/L. All of them showed a decrease in the removal of MC-LR with increasing of the initial toxin concentration. However, with a low concentration of 10 mg/L, this effect is not as significant as with the other concentrations tested. The effect of alkalinity was also investigated for this system. As expected, if there is any alkalinity available, the degradation rate was decreased due to scavenging effects. At lower alkalinity levels, it decreases drastically, while at relatively higher alkalinity concentrations, the difference is merely noticeable. Changes in pH were not significant in the values of MC-LR degradation rate for this homogeneous system. These results are being summarized for the elaboration of a manuscript and its submission in a relevant environmental journal.
Figure 1: MC-LR degradation rate vs H2O2 concentration. The initial concentration of MC-LR is 1 mg/L.
 

Future Activities:

Task 1.  Monitoring of HAB and Sampling in the Great Lakes

Five utilities were selected for the 2009 Great Lakes Monitoring Study. These utilities are located on Lakes Michigan, Huron and Erie. The Michigan III utility is on the west shores of Lake Michigan. The three utilities were selected from the west end of Lake Erie. The west end of the Lake Erie is noted for toxic cyanobacteria blooms. The three utilities include 2 small island communities and a medium size city. The 2 small island utility monitoring will be done in collaboration with Dr. Juli Dyble Bressie, NOAA. Dr. Julia Dyble Bressie has also agreed to sample for our study from the NOAA boats which will be located in Saginaw Bay, Lake Huron, and the west end of Lake Erie. In order to increase our likelihood of sampling a toxic cyanobacteria bloom, Dr. David Szlag, LSSU, will attempt to correlate harmful algal blooms with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. The current Chlorophyll-a data product derived from MODIS 1 km resolution bands is fairly accurate for the open ocean environment but experience in the Baltic Sea suggests that it may not accurately reflect conditions in shallow or near shore environments. The MODIS chlorophyll-a product and water temperature will be correlated with cyanotoxin measurements in the lower Great Lakes. The MODIS satellites deliver images several times a day at one kilometer resolution. 

 
Table 5: Plant Selection
 

Plant
Location
Treatment
Depth
Algae Data
Michigan III
44* 4' 31" N 87* 37' 17" W
Microfiltration Membranes, 500 micron pre-strainer, 0.2 micron membranes
28 ft
No
Erie II
2 miles NE of Cooley Canal entrance        41* 41' 58" N    83* 15' 58" W
Potassium permanganate, GAC, alum, lime, soda ash, Cl2, F-, alum coagulation, lime-soda ash softening plant
8-18 ft
No
Huron 2
Latitude: 43.71N, Longitude: 83.90 W
Ozone, lime softening, conventional treatment
17 ft
Yes
Erie III
 
 
 
 
 Erie IV
 
 
 
 

Task 2. Monitoring of HAB and Photochemical Effects in St. Johns River in Florida

Similar to 2008, monthly water sampling in the St. Johns River between Crescent Lake and north of Doctors Lake (in the area of Plummers Cove) will be performed  and analyzed for total and dissolved microcystin content.  This extension in the geographical coverage within the SJR is intended to increase the salinity range of sample collection.  Again, if a bloom event does occur in the St. Johns River 2L of dense algal material will be sent via overnight mail to the USEPA/University of Cincinnati and Florida International University on a as needed basis. Macro-invertebrate collection will be performed, if and when, microcystin concentrations are expected to be high (> 10 ug/L).  Invertebrate sample collection will be performed on a as needed basis and will be dependent on bloom formation or toxin concentrations over time.  Doctors Lake appears to be the best location for sample collection of bivalves.  Microcystin analysis on tissues will be limited to unbound microcystins as a confirmed protocol for tissues currently does not exist at GreenWater Laboratories/CyanoLab. GreenWater Laboratories/CyanoLab is currently developing a protocol for the quantification of MMPB (a breakdown product of bound microcystin) in animal sera and once this protocol is successful an attempt will be made to perform similar analyses on tissues of bivalve

Task 3. Fundamental Studies in the Photochemical Fate and Transformation of Cyanotoxins

For the subsequent funding period, we are planning advanced and 2 dimensional NMR experiments in an attempt to characterize the products of DA degradation as a mixture, but given the liable nature of peroxide products, low temperature studies may be required for proper isolation. While TiO2 photocatalysis effectively destroy and detoxify PbTxs, practical application will require further catalyst development and careful economic analyses. Development of solar activated catalyst on floating substrates may offer an attractive solution for the degradation of PbTxs in marine estuaries. The accomplishments, expenditures, and outputs are consistent with the proposed timetable relative to the date the funding was awarded.

Task 4. Exploring Nitrogen-Containing Surfactants for the Synthesis of TiO2-xNx

For the subsequent period report, we will continue our investigations on the effect of various water matrix parameters (i.e., NOM, hardness, turbidity, alkalinity) on the photocatalytic degradation of MC-LR and other cyanotoxins using UV/H2O2 and modified TiO2 photocatalytic nanoparticles and films, under UV, visible and solar irradiation employing real and simulated sunlight. Mechanistic studies will be carried out to determine the intermediates under these conditions. We will also explore other methods to synthesized visible light activated TiO2 nanomaterials with high photocatalytic activity towards MC-LR and other cyanotoxins. The role of film porosity on the transport and interactions of cyanotoxins on the TiO2 surface will also be explored. Real water with cyanotoxins will be also be evaluated. The equipment, techniques and materials will be the same or similar as described in the publications in appendix B-D.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other project views: All 54 publications 17 publications in selected types All 16 journal articles
Type Citation Project Document Sources
Journal Article Antoniou MG, Shoemaker JA, de la Cruz AA, Dionysiou DD. Unveiling new degradation intermediates/pathways from the photocatalytic degradation of microcystin-LR. Environmental Science & Technology 2008;42(23):8877-8883. R833223 (2008)
R833223 (Final)
  • Abstract from PubMed
  • Full-text: Environmental Science & Technology
    Exit
  • Journal Article Antoniou MG, Shoemaker JA, de la Cruz AA, Dionysiou DD. LC/MS/MS structure elucidation of reaction intermediates formed during the TiO2 photocatalysis of microcystin-LR. Toxicon 2008;51(6):1103-1118. R833223 (2008)
    R833223 (Final)
  • Abstract from PubMed
  • Full-text: Science Direct
    Exit
  • Abstract: Science Direct
    Exit
  • Other: Science Direct
    Exit
  • Journal Article Pelaez M, de la Cruz AA, Stathatos E, Falaras P, Dionysiou DD. Visible light-activated N-F-codoped TiO2 nanoparticles for the photocatalytic degradation of microcystin-LR in water. Catalysis Today 2009;144(1-2):19-25. R833223 (2008)
    R833223 (Final)
  • Full-text: Science Direct
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  • Abstract: Science Direct
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  • Other: Science Direct PDF
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  • Journal Article Song W, Xu T, Cooper WJ, Dionysiou DD, de la Cruz AA, O’Shea KE. Radiolysis studies on the destruction of microcystin-LR in aqueous solution by hydroxyl radicals. Environmental Science & Technology 2009;43(5):1487-1492. R833223 (2008)
    R833223 (Final)
  • Abstract from PubMed
  • Progress and Final Reports:

    Original Abstract
  • 2007
  • Final Report