Maintenance of cell integrity during hydroxyl radical rapid inactivation of Pseudanabaena sp. and simultaneous mineralization of odor compound 2-methylisoborneol.

Pseudanabaena sp. and the odor compound it produces, 2-methylisoborneol (2-MIB), has been reportedly responsible for off-flavor pollution worldwide, leading to substandard drinking water sensory indicators and serious water supply crises. In this paper, the hydroxyl radical (•OH) produced by the synergistic effect of strong ionization discharge and hydrodynamic cavitation rapidly inactivated Pseudanabaena sp. and simultaneously mineralized 2-MIB to a concentration of 2.57 ng/L, which is below the odor threshold of 10 ng/L for a total reactive oxidants (TRO) concentration of 1.2 mg/L within 12 s. Crucially, the intracellular 2-MIB level was maintained in approximately 155.26- 162.29 ng/L range, indicating that 2-MIB was not released from the cells. Based on the scanning electron microscopy (SEM) results, the integrity of Pseudanabaena sp. cells was maintained with intact membranes and no intracellular organic matters (IOM) released during •OH inactivation. In contrast, ClO2 caused severe membrane rupture and massive IOM release. Based on the gas chromatograph/mass spectrometer (GC/MS) analyses and mass spectral database, the chromatogram fitted the baseline with a TRO concentration of 4 mg/L and no peaks corresponding to intermediates were detected. Moreover, •OH could mineralize 2-MIB by opening the ring structures of 1,2,3,3-tetramethyl-4-cyclopentenone, neomenthol, and 2-methylcyclohexene-1-aldehyde to produce small-molecule compounds, finally leading to CO2 and H2O formation via three reaction pathways. Therefore, the •OH not only maintained the cell integrity of Pseudanabaena sp. during inactivation but also mineralized 2-MIB simultaneously.

Treatments of orange-spotted grouper (Epinephelus coioides) against Cryptocaryon irritans with •OH, ClO2 or HCHO: Survival, physiological and histological response.

Cryptocaryon irritans causes one of the most serious diseases in various wild and cultured marine fish, leading to mass mortality and economic loss. In this study, hydroxyl radical (•OH) solution produced by strong ionization discharge combined with water jet cavitation effect was injected into orange-spotted grouper (Epinephelus coioides) aquaculture tanks for C. irritans control. The results showed that all C. irritans theronts were inactivated by •OH solution at concentrations of 0.5 mg/L within 2 min. •OH could induce alteration of shape, the absence of motility and macronucleus dispersion in theronts. A possible explanation was that the macronucleus of C. irritans might be damaged by •OH; as a result, its metabolism and life activities were disturbed. The •OH treatment increased the survival rate of E. coioides challenged with C. irritans from 64.7 ± 8.0% (mean ± SD) to 100% and reduced their infection intensity significantly. Stress response biomarkers such as malonaldehyde, glutathione, glutathione peroxidase, superoxide dismutase (SOD) and catalase levels in the gills of E. coioides at different time points were analysed. The SOD activity in the •OH group first decreased and then recovered to the initial level at the end of the experiment. The other stress response biomarkers had no significant difference from that in the uninfected control group after •OH treatment. Additionally, the gill of E. coioides in the •OH group exhibited slight and reversible transformation compared with the uninfected control group. Compared with •OH treatment, chlorine dioxide and formalin treatment reduced the survival rate, induced oxidative damage and changed the histological gill structure in E. coioides. In conclusion, •OH could be applied effectively to control C. irritans infection without affecting the normal physiological condition of E. coioides.

Genome-Wide Association Analysis Reveals the Genetic Architecture of Parasite (Cryptocaryon irritans) Resistance in Large Yellow Croaker (Larimichthys crocea).

Large yellow croaker is an important marine culture species in China. Recently, the large yellow croaker industry is threatened by various disease problems, especially for the white spot disease, which is caused by parasite Cryptocaryon irritans. In the current study, we conducted a genome-wide association study (GWAS) for C. irritans resistance in two large yellow croaker populations (n = 264 and n = 480, respectively). We identified 15 QTL with explained genetic variance ranging from 1 to 8% in the two populations. One QTL on chromosome 23 was shared by the two populations, and three QTL had been reported in the previous study. We identified a lot of biological pathways associated with C. irritans resistance, such as hormone transport, response to bacterium, apoptotic process, acute inflammatory response to antigenic stimulus, and NF-kappa B signaling pathway. The genes casp8 and traf6 involved in regulatory network for apoptosis and inflammation were identified to be candidate genes for C. irritans resistance. Our results showed the complex polygenic architecture of resistance of large yellow croaker against C. irritans. These results would be helpful for the researches of the molecular mechanism of C. irritans resistance and genome-assisted breeding of large yellow croaker.

Development of solid-phase microextraction with multiple interactions-based monolithic fibers for the sensitive determination of perfluoroalkyl phosphonic acids in water and vegetable samples.

Due to highly fluorinated and di-anionic characters, it is great challenging to enrich perfluoroalkyl phosphonic acids (PFPAs). According to the unique chemical properties and molecular structure of PFPAs, a monolithic adsorbent using dodecafluoroheptyl acrylate and 4-vinylbenzyltrimethylammonium chloride as mixed functional monomers was synthesized and utilized as the extraction medium of multiple monolithic fibers solid-phase microextraction (MMF-SPME). Results well evidenced that the obtained adsorbent could enrich PFPAs effectively by means of multiple interactions including fluorophilic and anion-exchange interactions. Under the optimized synthesized and extraction conditions, a sensitive approach for the monitoring of trace levels of PFPAs in water and vegetable samples was developed by the combination of MMF-SPME and high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Limits of detection (LODs, S/N = 3) for water and vegetable samples were in the ranges of 0.00011-0.00086 µg/L and 0.0022-0.055 µg/kg, respectively. The introduced method was successfully applied to monitor target PFPAs in lake water, wastewater, pumpkin and cucumber samples. Recoveries at different spiking levels and the relative standard deviations for precision were in the ranges of 80.6-120% and 0.9-12%, respectively. Compared to previously reported approaches, the current method displays some merits such as simple operation, satisfactory sensitivity, low cost and eco-friendliness.

Use of multiple regression models for predicting the formation of bromoform and dibromochloromethane during ballast water treatment based on an advanced oxidation process.

Disinfection byproducts (DBPs) generated by ballast water treatment have become a concern worldwide because of their potential threat to the marine environment. Predicting the relative DBP concentrations after disinfection could enable better control of DBP formation. However, there is no appropriate method of evaluating DBP formation in a full-scale ballast water treatment system (BWTS). In this study, multiple regression models were developed for predicting the dibromochloromethane (DBCM) and bromoform (TBM) concentrations produced by an emergency BWTS using field experimental data from ballast water treatments conducted at Dalian Port, China. Six combinations of independent variables [including several water parameters and/or the total residual oxidant (TRO) concentration] were evaluated to construct mathematical prediction formulas based on a polynomial linear model and logarithmic regression model. Further, statistical analyses were performed to verify and determine the appropriate mathematical models for DBCM and TBM formation, which were ultimately validated using additional field experimental data. The polynomial linear model with four variables (temperature, salinity, chlorophyll, and TRO) and the logarithmic regression model with seven variables (temperature, salinity, dissolved oxygen, pH, turbidity, chlorophyll, and TRO) exhibited good reproducibility and could be used to predict the DBCM and TBM concentrations, respectively. The validation results indicated that the developed models could accurately predict DBP concentrations, with no significant statistical difference from the measured values. The results of this work could provide a theoretical basis and data reference for ballast water treatment control in engineering applications of emergency BWTSs.

OH degraded 2-Methylisoborneol during the removal of algae-laden water in a drinking water treatment system: Comparison with ClO2.

The growth of algae in water and the taste and odour compounds produced by algal metabolism present a threat to water quality, public health and aquatic ecosystems and cannot be effectively removed by conventional water treatment processes. In this paper, a hydroxyl radical (OH)-based drinking water treatment system (DWTS) with a capacity of 480 m3 per day was built in the Xinglin water plant, Xiamen, China. With pretreatment at 0.88 mg L-1, sand filtration, and disinfection at 0.31 mg L-1 during the conveyance of algae-laden water within only 9.8 s, OH removed all five kinds of algae, with a total content of 35,180 cells mL-1, while ClO2 treatment left live and dead algae at 7150 cells mL-1, which would be transported into the pipe networks for the drinking water supply. Meanwhile, OH degraded 2-Methylisoborneol (2-MIB) from 175 to 4.4 ng L-1, which was below the Chinese standard of 10 ng L-1, while ClO2 degraded 2-MIB only to 155 ng L-1. Based on analyses of the mass spectra database, OH could mineralize 2-MIB by opening the ring structures of 2,2-dimethyl-1,3-cyclopentanedione and 2-methyl-cyclohexenecarboxaldehyde to produce small-molecule compounds. After OH pretreatment and OH disinfection, all water quality and disinfection by-product indexes met the Chinese Sanitary Standards for Drinking Water. Therefore, OH advanced oxidation produced using strong ionization discharge could be practically applied for the degradation of 2-MIB during the treatment of algae-laden water in the OH DWTS.

Electric field-induced selective catalysis of single-molecule reaction.

Oriented external electric fields (OEEFs) offer a unique chance to tune catalytic selectivity by orienting the alignment of the electric field along the axis of the activated bond for a specific chemical reaction; however, they remain a key experimental challenge. Here, we experimentally and theoretically investigated the OEEF-induced selective catalysis in a two-step cascade reaction of the Diels-Alder addition followed by an aromatization process. Characterized by the mechanically controllable break junction (MCBJ) technique in the nanogap and confirmed by nuclear magnetic resonance (NMR) in bottles, OEEFs are found to selectively catalyze the aromatization reaction by one order of magnitude owing to the alignment of the electric field on the reaction axis. Meanwhile, the Diels-Alder reaction remained unchanged since its reaction axis is orthogonal to the electric fields. This orientation-selective catalytic effect of OEEFs reveals that chemical reactions can be selectively manipulated through the elegant alignment between the electric fields and the reaction axis.

•OH Inactivation of Cyanobacterial Blooms and Degradation of Toxins in Drinking Water Treatment System.

Cyanobacterial blooms continue to serve as one of the most serious global issues threatening water supply and human health. During cyanobacterial bloom season, a large •OH-yield equipment was developed and installed after coagulation settling in a 12000 ton/day drinking water treatment system in Xiamen, China. An •OH concentration of 7.76∼57.8 µmol/L was formed by using the oxygen activated species generated by strong ionisation discharge combining with the effect of water jet cavitation. •OH pre-treatment at a dose of 1.0 mg/L inactivated cyanobacterial blooms in the process of conveying bloom water within only 20s, which were then removed by sand filtration. Under SEM observation, dominant Microcystis sp. colonies connected by mucilage were dispersed into individuals that still retained the cell integrity, indicating no release of intracellular organic matter (IOM). According to a flow cytometry analysis, the main cause of •OH inactivation was the breakage of DNA strands. Meanwhile, the •OH-mineralized microcystin-LR was by breaking the C=C conjugated diene bond and crucial opening the persistent benzene ring to carboxylic acid m/z 158.0. During •OH pre-treatment of 1.0 mg/L and NaClO disinfection of 0.5 mg/L, all water quality indexes and disinfection by-product (DBP) contents complied with the Chinese Sanitary Standards for Drinking Water. Therefore, the •OH based on the strong ionisation discharge showed great prospect for large-scale drinking water treatment in the removal of cyanobacterial blooms while retaining cell integrity as well as the degradation of toxins.

Sensitive determination of perfluoroalkane sulfonamides in water and urine samples by multiple monolithic fiber solid-phase microextraction and liquid chromatography tandem mass spectrometry.

To extract perfluoroalkane sulfonamides (PFASAs) in water and urine samples effectively, a new adsorbent based on poly (1H,1H,2H,2H-nonafluorohexyl acrylate/vinyboronic anhydride pyridine complex-co-ethylenedimethacrylate) monolith (FBE) was synthesized and used as the extraction phase of multiple monolithic fiber solid-phase microextraction (MMF-SPME). Because there are abundant fluorinated (F-) alkyl chains and boron atoms in the adsorbent, the FBE/MMF-SPME displays satisfactory extraction performance for PFASAs by means of fluorophilic and B-N coordination interactions. Under the most favorable conditions, the FBE/MMF-SPME was combined with HPLC-MS/MS for the sensitive monitoring of ultra-trace PFASAs in environmental water and human urine samples. The limits of detection and limits of quantification achieved for target analytes were in the range of 0.13-1.45 ng/L and 0.44-4.80 ng/L, respectively. The developed FBE/MMF-SPME-HPLC-MS/MS method was successfully applied to quantify the level of PFASAs in water and human urine samples, and ultra-trace target PFASAs were detected in the real samples. The recoveries at different fortified concentrations ranged from 80.3% to 119% with RSD in the range of 0.9-11%. Compared with reported methods, the proposed method exhibits some merits such as high sensitivity, good method precision, low consumption of sample and environmental friendliness.

Application of a hydroxyl-radical-based disinfection system for ballast water.

A hydroxyl radical (OH) ballast water treatment system (BWTS) was developed and applied to inactivate entrained organisms in a 10,000-ton oceanic ship, where OH was produced by a strong ionization discharge combined with a water jet cavitation effect. The calculated OH generation rate was 1373.4 µM min-1 in ballast water, which is much higher than that in other advanced oxidative processes such as photocatalysis. As a result, non-indigenous red tide algae were inactivated to meet the ballast water discharge standards (<10 cells mL-1) of the International Maritime Organization. The ratio of variable fluorescence to maximum fluorescence (Fv/Fm) for algal chlorophyll rapidly decreased to zero within a contact time of only 6 s, indicating complete inactivation of algae. Observation under a scanning electron microscope showed no cellular materials were released by algal cells upon OH inactivation. A risk assessment of the OH treatment system was conducted, and the ratios of predicted environmental concentrations to predicted no effect concentrations of all detected disinfection byproducts were less than 1, even at a worst-case oxidant concentration of 2.41 mg L-1. Ship ballast water treated using OH inactivation is safe for marine environments. Finally, the energy consumption and operational costs of the OH BWTS were found to be 0.033 kWh m-3 and CNY 0.03 m-3, respectively.

Efficient extraction of perfluorocarboxylic acids in complex samples with a monolithic adsorbent combining fluorophilic and anion-exchange interactions.

Efficient extraction of perfluorocarboxylic acids (PFCAs) is a key step for the accurate and sensitive determination of PFCAs due to their low concentration and the complexity of sample matrices. Herein, according to the chemical characteristics of PFCAs, a new adsorbent based on poly (2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate/(vinylbenzyl)trimethylammonium chloride-co-divinylbenzene/ethylenedimethacrylate) monolith was fabricated and utilized as the extraction medium of multiple monolithic fiber solid-phase microextraction (MMF-SPME). Results well indicted that the prepared monolithic adsorbent (MA) could efficient extract PFCAs through fluorophilic and anion-exchange interactions. Under the optimal conditions, the MA/MMF-SPME was combined with HPLC-MS/MS for the sensitive monitoring of ultra-trace PFCAs in water and milks samples. The limits of detection (S/N = 3) of the target PFCAs in water and milk samples were 0.40-4.40 ng/L and 0.9-12.1 ng/L, respectively. Furthermore, the proposed method also exhibited some merits including wide linear dynamic ranges, satisfactory sensitivity, good method precision and low consumption of sample and organic solvent. Isotope internal standard calibration curve method was used to quantify the concentration of PFCAs in real samples, and trace levels of PFCAs in tap water and milk samples had been successfully detected.

The estimation for ballast water discharged to China from 2007 to 2014.

Ballast water has been identified as one of the main causes for worldwide transfer of non-indigenous marine species. The volume and source of ballast water are the fundamental elements for an evaluation of the risk posed. However, it is difficult to obtain the volume of ballast water discharged to China, because of the absence of information platform, and until now there is no public report. In this paper, the total volume of ballast water discharged to China and Chinese five major port-groups were estimated. Results showed: the total volume of ballast water exhibited a trend of slow increase from 2007 to 2014, and reached 311 million tons in 2014. Yangtze River Delta received the highest volume of ballast water among all port-groups. The information provided in this research may play an important role in helping policy decision-makers manage such coastal discharges.

Inactivation of invasive marine species in the process of conveying ballast water using OH based on a strong ionization discharge.

In this paper, invasive marine species in medium-salinity ballast water were inactivated using OH generated from a strong ionization discharge. The OH is determined by the concentration of oxygen active species combined with the effects of water jet cavitation. The results indicated that the OH concentration reached 7.62 µM, within 1 s, which is faster and higher than in conventional AOP methods. In a pilot-scale OH ballast water system with a capacity of 10 m(3)/h, algae were inactivated when CT value was 0.1 mg min/L with a contact time only 6 s. The viable and nonviable cells were determined using SYTOX Green nucleic acid stain and Flow cytometry. As a result, the OH treatment could be completed during the process of conveying the ballast water. In addition, the concentrations of relevant disinfection by-products (DBPs), such as trihalomethanes (THMs), haloacetic acids (HAAs), and bromate, were less than that required by the World Health Organization's drinking water standards, which suggest that the discharged ballast water posed no risks to the oceanic environment. Nevertheless, for conventional ozonation and electrolysis methods, the ballast water should be treated only in the treated tanks during the ship's voyage and form higher level DBPs.

[Seasonal Variation on Nutrient Limitation for Phytoplankton Growth in a Coastal River-Reservoir System, Southeast China].

A comprehensive analysis was conducted using a dataset obtained from October in 2013 to October in 2014 monitoring in 20 headwater streams of Jiulong River and four reservoirs, situated in such a coastal river-reservoir system in Southeast China suffering from intensive anthropogenic disturbance. In-situ monitoring, GIS and statistical analysis were coupled in this study to identify the spatiotemporal variations of nutrients & phytoplankton abundance and community structure, the differentiation of nitrogen & phosphorus limitation of phytoplankton growth, and the seasonal variations in nutrient limitation of phytoplankton growth. The results showed that there were obvious spatiotemporal variations in terms of nutrients & phytoplankton abundance and community structure in the 20 headwater streams and four reservoirs. The concentration of nitrogen was higher in winter and spring whereas lower in summer and autumn for both 20 headwater streams and four reservoirs. However, the concentration of phosphorus showed an opposite trend. The phytoplankton's abundance was the highest in summer for four reservoirs while it was higher in winter and spring, lower in summer and autumn in the 20 headwater streams. Meanwhile, the main trend in the succession of phytoplankton was from Bacillariophyta in autumn, winter and spring to Chlorophyta in summer in Tingxi reservoir, from Chlorophyta-Cryptophyta in winter and spring to Chlorophyta-Cyanophyta in summer and autumn in Jiangdong reservoir. No obvious trend exhibited in phytoplankton succession in Shidou-Bantou reservoir and 20 headwater streams. The Redundancy analysis (RDA) ordination plots well displayed the phytoplankton's community structure and its relationships with environmental factors. Besides, according to linear regression analysis there was a closer correlation between chlorophyll-a and nutrients in four reservoirs than in 20 headwater streams. In four reservoirs, N limitation was preliminarily observed in autumn whereas P limitation exhibited in winter.

[Determination of 2-methylisoborneol and geosmin in drinking water using headspace solid phase micro-extraction coupled with gas chromatography-mass-spectrometry].

The odorous compounds of 2-methylisoborneol (2-MIB) and geosmin (GSM) heavily produced and released in water source are one of the most important factors leading to off-flavor emergencies and resident water consumption panic in drinking water. A headspace solid phase micro-extraction ( HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) method was established for the simultaneous determination of these two trace earthy and musty compounds in reservoir water, reservoir soil and tap water. The conditions of HS-SPME, such as salt amount, extraction time and extraction temperature, were optimized based on orthogonal analysis. The qualitative and quantitative analyses of 2-MIB and GSM were carried out in the electron impact (EI) -selective ion scanning mode. The results showed that the linear relationship between peak area and concentration of 2-MIB and GSM was good enough (r2 0.998) from 5 to 1 000 ng/L, the limits of detection were 0.72 ng/L for 2-MIB, 0.34 ng/L for GSM and the limits of quantification were 2.40 ng/L for 2-MIB, 1.13 ng/L for GSM. When the target samples spiked in the range of 10-600 ng/L, the average recoveries of the target compounds were 93.6% - 107.7% ( RSD ≤ 6.1%, n = 6). Based on the above method, the target compounds in reservoir water, reservoir soil and tap water in a certain region of Liaoning Province were analyzed. The results showed that the two target odors in reservoir water were 3.0 -3.6 ng/L. As for the extract of the soil around the reservoir, 2-MIB was 8.1 ng/L and GSM was 17.8 ng/L. The odorous substances were not detected in the tap water. This method is simple, accurate, reliable, highly sensitive and no need of organic solvents. And it is suitable for the detection of 2-MIB and GSM in drinking water.

Risk assessment of marine environments from ballast water discharges with laboratory-scale hydroxyl radicals treatment in Tianjin Harbor, China.

For the majority of ballast water treatment system (BWTS) that employ active substances (e.g., oxidative compounds), relevant chemicals (RCs) formation is an issue owing to their potential adverse effects on aquatic organisms. Accordingly, BWTS must be approved by the International Maritime Organization (IMO), and the approval procedure requires environmental risk assessment. The most commonly employed harbor used to calculate predicted environmental concentrations (PECs) for RCs in treated ballast water is the GESAMP-BWWG (Group of Experts on Scientific Aspects of Marine Environmental Protection-Ballast Water Working Group) model harbor. However, there is very little assessment data available regarding the associated environmental impacts in ports and harbors of China. Therefore, in this study the concentration of fifteen RCs from the existing laboratory-scale BWTS using hydroxyl radicals was obtained and input into the MAMPEC (Marine Antifoulant Model to Predict Environmental Concentrations) model to compute PECs in Tianjin Harbor, China. The potential risks to the aquatic environment posed by treated ballast water in Tianjin Harbor were further assessed based on the calculated ratio of PECs and predicted no effect concentrations (PNECs). Only monochloroacetic acid and dichloroacetic acid were found to have potential risks, and the ratios of PECs and PNECs to the other measured RCs were less than 1, indicating that the environmental risk posed by treated ballast water discharged into Tianjin Harbor is of little concern. The concentration of total residual oxidant recommended by the IMO (<0.2 mg/L) in treated ballast water at discharge was found to be at levels that may pose a risk to the aquatic environment in Tianjin Harbor.

Evaluation of the ecotoxicity and biological efficacy of ship's ballast water treatment based on hydroxyl radicals technique.

Ballast water has been identified as one of the key pathways for the movement of species between different ecosystems. The purpose of this study is to evaluate the biological efficacy and the potential toxicological impact of a proposed ballast water treatment using hydroxyl radicals as the main active substances. Living biomass of organisms kept in treated water for 2 days met the requirement stated in the International Maritime Organization (IMO) Ballast Water Convention (Regulation D-2), and no re-growth was observed over a period of 5 days. Aquatic toxicity tests of three trophic levels for the treated ballast water were performed. The results indicated that the toxicological risk of the discharge water to the receiving environment was not significant.

Simultaneous desulfurization and denitrification of flue gas by ·OH radicals produced from O2+ and water vapor in a duct.

In the present study, simultaneous flue gas desulfurization and denitrification are achieved with ·OH radicals generated from O(2)(+) reacting with water vapor in a duct. The O(2)(+) ions are generated by a strong ionization dielectric barrier discharge and then injected into the duct. Compared with conventional gas discharge treatment, the present method does not need a plasma reaction reactor, additional catalysts, reductants, or oxidants. The main recovered products are the liquids H(2)SO(4) and HNO(3), which can be used in many processes. Removal rates of 97% for NO and 82% for SO(2) are obtained under the following optimal experimental conditions: molar ratio of reactive oxygen species (O(2)(+), O(3)) to SO(2) and NO, 5; inlet flue gas temperature, 65 °C; reaction time, 0.94 s; and H(2)O volume fraction, 8%. Production of O(2)(+) and the plasma reaction mechanisms are discussed, and the recovered acid is characterized. The experimental results show that the present method performs better for denitrification than for desulfurization. Compared with conventional air discharge flue gas treatments, the present method has lower initial investment and operating costs, and the equipment is more compact.

Rapidly eliminating pathogenic microorganisms in large air space using spraying *OH radicals.

A new method for rapidly eliminating pathogenic microorganisms in large air space using spraying *OH radicals is presented in this paper With a physical method of strong electric-field discharge, large numbers of *OH radicals were produced by the oxygen activated particles of O2+, O(1D), O(3P), etc., and the introducing reagent HO2-. The gram-positive bacteria Bacillus subtilis, the gram-negative bacteria Serratia marcescens, and Bacillus spores were used for the eliminating experiments. Results show that the different microorganisms were rapidly killed by *OH radicals with a concentration of 0.8 mg/L and spraying density of 21 microL/m2 within 4 sec. Cell morphological changes were also observed under microscope. The cells of B. subtilis and Bacillus spores in their cellular wall, cellular membrane, or cell protoplasm were greatly destroyed when being exposed to a killing dosage of *OH radicals.

[Studies for killing the oceanic harmful organisms in ship's ballast water using hydroxyl radicals].

With a physical method of strong electric-field discharge, O2 in air and H2O at gas state are ionized and dissociated into a number of activated particles such as *OH, O2+, H2O+, etc, which are injected into a part of ballast water to form the dissolved *OH. High concentration of *OH solution was injected into the main pipe of discharge ballast water to effectively and fast kill the oceanic harmful organisms and bacteria in the course of conveying ship's ballast water. In the 10 t x h(-1) experimental system of ship's ballast water, the experiments were carried out for killing the plankton and bacteria using *OH radicals. The *OH concentration is 0.65 mg x L(-1) for 100% killing efficiency. At the same time, cell morphology changes of Chaetoceros muelleri and Nitzschia closterium were observed by a microscope. The cells of algae in their cellular wall, cellular membrane or cell protoplasm were greatly destroyed using *OH radicals.