NaHSO3 Solution Research Articles

Electrochemical study on corrosion process characteristics of the high-strength low-alloy steels in NaHSO3 solution

Electrochemical methods were used to study the characteristics of corrosion process for the high-strength low-alloy steel and carbon steel used as a huge oil storage tank in NaHSO3 solution. The polarization curve results show that both steel samples take place in active solution, and the high-strength low-alloy (HSLA) steel has higher i corr value than carbon steel, which is due to the small grain size that provides high density of active sites for preferential attack. The electrochemical impedance spectroscopy (EIS) results make known that the corrosion process presents two stages. In the first 136 h, one-time constant in EIS diagrams can be shown. Both steels have similar corrosion resistance due to the combination effects of the grain size and microstructure. After 240 h of immersion, a complete passive film forms on the specimen surface, and two-time constants can be shown in EIS diagram. The HSLA steel exhibited improved corrosion resistance when compared with the carbon steel, which is due to the effect of the shape Fe3C in microstructure and the deposition of FeSO4 on the electrode surface. The scanning electrode microscopy analyses show that both steels take place in homogenous corrosion, and the carbon steel shows higher surface roughness and many Fe3C residues. XRD results show that both steels have similar phase constitutes of corrosion products.

Dispersiones acuosas de poliuretano bloqueado: una alternativa como agente curtiente

Se sintetizaron y se evaluaron como agentes curtientes de pieles vacunas dos tipos de agentes de reticulación base poliuretano bloqueado. Se presentan los resultados de la síntesis de dispersiones acuosas de poliuretano bloqueado (DPU’s), basadas en prepolímeros a partir de la reacción de los diisocianatos alifáticos H12MDI (4,4’ metilenbis-ciclohexilisocianato) y HDI (hexametilendiisocianato) con polioles base poliéter óxido de etileno de peso molecular 1 y 2 KDa, en una relación molar isocianato/oxhidrilo (NCO/OH) de 4:1 y 6:1 a 100 °C por 2 y 4 horas. En una segunda reacción, los grupos isocianato (NCO) libres del prepolímero se bloquearon con una solución acuosa de NaHSO3 ó Na2S2O5 al 40%p/p. Los prepolímeros se caracterizaron mediante espectroscopia IR y RMN de ¹H. El tanto por ciento de isocianato libre en el prepolímero, así como el bloqueo de dichos grupos, se determinaron por espectroscopía IR. La evaluación de la capacidad curtiente de las DPU’s se determinó de acuerdo a la estabilidad térmica de la piel (temperatura de desnaturalización), mediante Calorimetría Diferencial de Barrido (DSC) y a la determinación del índice de reticulación de las DPU’s con la colágena de la piel mediante un ensayo con ninhidrina.

A Novel Method for Synthesis of Sulfonated SBS Ionomers by Ring-Opening Reaction of Epoxidized SBS, Their Characterization, Properties, and Blends

A novel method for synthesis of sulfonated ionomer of (styrene-butadiene-styrene) triblock copolymer (SBS) is developed. SBS is first epoxidized by performic acid formed in situ, followed by ring-opening reaction with an aqueous solution of NaHSO3. The optimum conditions for ring-opening reaction of the epoxidized SBS with aqueous solution of NaHSO3 and some properties of the ionomer are studied. It has been found that during the ring-opening reaction phase transfer catalyst, ring-opening catalyst, and a pH regulator are necessary to raise the conversion of epoxy groups to ionic groups. The product is characterized with FTIR spectrophotometry and transmission electron microscopy (TEM) to be the sulfonated ionomer with ionic domains about 5 nm in diameter. With increasing ionic groups, the water absorbency of the ionomer and the dilute solution viscosity of the ionomer increase, whereas the oil absorbency decreases. The ionomer behaves as thermoplastic elastomer in the presence of zinc stearate as ionic plasticizer. The tensile strength and ultimate elongation of the sodium ionomers are higher than those of the original SBS and both increase with zinc stearate below 10 wt% and with ionic group content up to about 1 mmol/g. When the ionomer is blended with crystalline polypropylene, a synergistic effect occurs with respect to the tensile strength. The ionomer can act as a compatibilizer for blending equal weight of SBS and oil-resistant chlorohydrin rubber. In the presence of 3% ionomer, the blend exhibits much better mechanical properties and solvent resistance than the blend without the ionomer. The blend of equal weight of SBS and CHR compatibilized by the ionomer behaves as an oil resistant thermoplastic elastomer. Scanning electron micrographs of the blends with or without the ionomer indicate the increased compatibility between the two components in the presence of the ionomer.

Effect of Al alloying on corrosion performance of steel

To clarify some features of the atmospheric corrosion mechanism, the corrosion performance of Al bearing steels after wet/dry cyclic corrosion tests were studied by gravimetry, SEM, X-ray diffraction (XRD), potentiodynamic polarisation tests and electrochemical impedance spectra (EIS). The results showed that rusted Al bearing steel presented a better corrosion resistance than that of rusted plain carbon steel (Q235) in 0·3%NaCl (i.e. simulating a marine environment) solution; moreover, the corrosion resistance of Al bearing steel increased with increasing Al content. The formation of a spinel double oxide containing Al(FeAl2O4) in Al alloying steels was observed, which refined the structure of the inner rust layer, suppressed the anodic dissolution and accelerated the cathodic reduction. In addition, Al alloying increased the content of γ-FeOOH and decreased that of β-FeOOH. However, in NaHSO3 solution (i.e. simulating an industrial environment), the rust layer on Al bearing steel did not possess a protective ability, and the rust layer formed was not physically or chemically stable.

Low concentrations of NaHSO<sub>3</sub> increase photosynthesis, biomass, and attenuate photoinhibition in Satsuma mandarin (Citrus unshiu Marc.) plants

Spraying low concentrated (0.5–5.0 mM) solutions of NaHSO3 on Satsuma mandarin (Citrus unshiu Marc.) leaves resulted in enhancement (maximal about 15 % at 1 mM NaHSO3) of net photosynthetic rate (PN) for 6 d. The potential photochemical efficiency of photosystem 2 (PS2, Fv/Fm) and the quantum yield of PS2 electron transport (ΦPS2) were increased under strong photon flux density (PFD). The slow phase of millisecond delayed light emission (ms-DLE) was increased, showing that the transmembrane proton motive force related to photophosphorylation was enhanced. We also observed that low concentrations of NaHSO3 promoted the production of ATP in irradiated leaves. We suggest that the increase in PN in Satsuma mandarin leaves caused by low concentrations of NaHSO3 solution may have been due to the stimulation of photophosphorylation and, hence, the increase in photochemical efficiency through speeding-up of PS2 electron transport. Photoinhibition of photosynthesis in leaves was modified by NaHSO3 treatment under high PFD. Hence the increase in leaf dry mass seems to be associated with the mitigation of photoinhibition caused by strong PFD.

Synthesis of sulfonated rubber ionomers by the ring-opening reaction of epoxidized styrene–butadiene rubber, their characterization, and their properties

A novel method for the synthesis of the sulfonate ionomer of styrene-co-butadiene rubber (SBR) was developed. SBR was first epoxidized by performic acid formed from hydrogen peroxide and formic acid in situ in solution, and this was followed by a ring-opening reaction with an aqueous solution of NaHSO3. The optimum conditions for the epoxidation of SBR in the presence of a phase-transfer catalyst and for the ring-opening reaction of epoxidized SBR with an aqueous solution of NaHSO3 were studied. During the epoxidation of SBR, a phase-transfer catalyst, such as poly(ethylene glycol), could enhance the conversion of double bonds to epoxy groups. During the ring-opening reaction, both the phase-transfer catalyst and ring-opening catalyst were necessary to enhance the conversion of the epoxy groups to ionic groups. The addition of Na2SO3 to the reaction mixture was important to obtain 100% conversion. The products were characterized with Fourier transform infrared spectrophotometry, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). DSC showed that the sodium sulfonate SBR ionomer possessed a dissociation temperature of ionic domains at 110°C, which appeared as black spots under TEM, after the sodium ions of the ionomer were substituted by lead ions. Some properties of the sodium ionomer, such as the water absorbency, oil absorbency, and dilute solution behavior, were studied. With increasing ionic groups, the water absorbency of the ionomer increased, whereas the oil absorbency decreased. The dilute solution viscosity of the ionomer increased abruptly with increasing ionic group content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3090–3096, 2006

Promotive Effect of Low Concentrations of NaHSO3 on Photophosphorylation and Photosynthesis in Phosphoenolpyruvate Carboxylase Transgenic Rice Leaves

Abstract: Spraying a 1–2 mmol/L solution of NaHSO3 on the leaves of wild-type rice (Oryza sativa L.) Kitaake (WT), phosphoenolpyruvate carboxylase (PEPC) transgenic (PC) rice and PEPC+phosphate dikinase (PPDK) transgenic rice (PC+PK), in which the germplasm was transformed with wild-type Kitaake as the gene receptor, resulted in an enhancement of the net photosynthetic rate by 23.0%, 28.8%, and 34.4%, respectively, for more than 3 d. It was also observed that NaHSO3 application caused an increase in the ATP content in leaves. Spraying PMS (a cofactor catalysing the photophosphorylation cycle) and NaHSO3 separately or together on leaves resulted in an increase in photosynthesis with all treatments. There was no additional effect on photosynthetic rate when the mixture was applied, suggesting that the mechanism by which NaHSO3 promotes photosynthesis is similar to the mechanism by which PMS acts and that both of compounds enhanced the supply of ATP. After spraying a solution of NaHSO3 on leaves, compared with the WT Kitaake rice, a greater enhancement of net photosynthetic rate was observed in PEPC transgenic (PC) and PEPC+PPDK transgenic (PC+PK) rice, with the greatest increase being observed in the latter group. Therefore ATP supply may become the limiting factor that concentrates CO2 in rice leaves transformed with an exogenous PEPC gene and exogenous PEPC+PPDK genes. (Managing editor: Ping HE)

New Route to Vicasol, a Water-Soluble Form of Vitamin K3

A procedure was suggested for preparing vicasol in an approximately 85% yield in a two-phase system consisting of concentrated (∼5-6 M) aqueous solution of NaHSO3 and a solution of 2-methyl-1,4-naphthoquinone in an incombustible organic solvent (e.g., chloroform or trichloroethylene).

Enhancing ATP Formation to Increase Photosynthesis

ATP is the necessary component of assimilation power in photosynthesis. It is not only required for CO2 assimilation but also for the maintaining of the operation of the photosynthetic apparatus, such as for the activation or phosphorylation of several kinds of enzymes or other proteins. It is widely accepted that the reduction of NADP+ by the photosynthetic noncyclic electon transfer is coupled with the formation of ATP. The ATP/NADPH ratio is generally considered to be 1.33, which is lower than the ratio required for the assimilation of one molecule of CO2 to carbohydrate level. The insufficient amount of ATP is believed to be supplemented by cyclic or pseudocyclic photophosphorylation (PSP), though there is still debate about which way is more important. In our lab, we showed by several kinds of experiments that in many cases the photosynthesis was often limited by ATP supply, and might be enhanced by two kinds of measures. One is to improve the coupling efficiency by some treatments, such as increasing the concentration of phosphate or polybasic acids, or adding some coupling efficiency improvers. The other way is to increase cyclic PSP by applying adequate amount of PMS solution to the leaves. Recently, we found that spraying 1-2 mM of NaHSO3 solution to the leaves could also enhance cyclic PSP in vivo, which was indicated by increase of the ms-delayed light emission, P700 turnover and post-illumination fluorescence of chlorophyll. As NaHSO3 is very cheap and has no harmful effect at such low concentration, it is hopeful that it could be used as a practical measure in agricultural production. In some experiments, when NaHSO3 was sprayed on wheat or rice leaves during early stage of ripening, the photosynthesis was increased by more than 10% for several days and the yields of harvest were increased by 10%.

Ethylene produced by the lichen Cladina stellaris exposed to sulphur and heavy‐metal‐containing solutions under acidic conditions

Podetia of the terricolous lichen Cladina stellaris (Opiz) Brodo, collected in an unpolluted rural area in N. Finland, were wetted with either H2O, diluted acidic solutions of H2SO4, HNO3 and NaHSO3, simulating acidic rain, or the following salts: K2SO4, KCl, CuSO4, CuCl2, Cu(NO3)3, ZnSO4, ZnCl2, Zn(NO3)2, FeSO4, FeCl2, Fe2(SO4)3, FeCl3 and Fe(NO3)3. The samples were further exposed to combined treatments in both acidic solutions, simulating acidic rain, and heavy metal salts in solution. Lichen samples wetted with H2O at pH 6·8, diluted solutions of H2SO4, HNO3 or a mixture of these two acids produced low concentrations of endogenous ethylene. The application of NaHSO3 greatly increased the production of ethylene. The application of KCl induced a higher rate of ethylene production than the application of K2SO4 solutions. The application of Cu‐containing solutions enhanced the production of ethylene. The influence of Zn was smaller than that of Cu. Iron was the most effective heavy metal to promote the production of ethylene: very high ethylene concentrations were detected upon the application of FeCl2. Combined treatments in H2SO4 or H2SO4+HNO3 followed by either FeCl2 or FeSO4, yielded higher concentrations of ethylene than the same treatments in a reversed order. The role of Fe ions in the production of ethylene is discussed in reference to previous works dealing with ethylene production in higher plants, fungi and algae.

The Influence of Air Pollution on the Concentration of Airborne Elements and on the Production of Stress-Ethylene in the Lichen Usnea hirta (L.) Weber em. Mot. Transplanted in Urban Sites in Oulu, N. Finland

The purpose of the present study was to examine theresponse, as indicated by the production of stress-ethylene, of the lichenUsnea hirta, to a buffered acidic solution and to a solutioncontaining bisulfite ion, both at pH 4.0. In addition, the study investigatedthe accumulation capacity of U. hirta transplanted either to thevicinity of two streets with slow traffic, or to the vicinity of a highway inthe city of Oulu, N. Finland for a short period (45 d), and to analyze thecomparative production of stress-ethylene and the amounts of airborneelements accumulated in the thallus. Thalli of U. hirta manifested ahigh accumulation capacity for K, Ca, Na, Mg, Fe, Zn, and Mn in samplesexposed in one of the two streets with slow traffic in Oulu, in comparisonwith thalli left at the control site in the forest outside of the city. Twoof the observed elements, Pb and Ca, exhibited a positive correlation withthe concentration of ethylene detected consecutive to the treatment of lichenthalli with H2O (pH 6.8). The concentrations of stress-ethylene inlichen thalli retrieved from the streets with slow traffic and less cars(14,000 per day), soaked in solutions of NaHSO3 (pH 4.0), werehigher than those produced by thalli retrieved from a site near the highway(with 25,000 cars per day) and by thalli left in the forest. It is suggestedthat the streets with slow traffic and less cars are more polluted than thehighway as a result of bad ventilation conditions and a slow rate ofdispersion of airborne pollutants.

Nitration of pyridine by dinitrogen pentoxide, a study of the reaction mechanism †

The nitration of pyridine and substituted pyridines by dinitrogen pentoxide (DNP) has been studied. The reaction of DNP with pyridine in either liquid SO2 or an organic solvent produces N-nitropyridinium nitrate (4). On reaction of this with aqueous solutions of SO2 or NaHSO3 three transient species are formed: N-nitro-1,4-dihydropyridine-4-sulfonic acid (5), N-nitro-1,2-dihydropyridine-2-sulfonic acid (6) and 1,2,3,6-tetrahydro-3-nitropyridine-2,6-disulfonic acid (7). Compounds 6 and 7 may be sulfite esters instead of sulfonic acids. Compound 5 reacts by a first order reaction [ΔH‡ = 32(1) kcal mol–1, ΔS‡ = 31(4) cal K–1 mol–1] and 3-nitropyridine is formed. Compound 6 is rapidly transformed to 7 which reacts by a first order pH dependent reaction {kobs = 1.9(4) × 10–4 s–1 + 3.5(2) × 10–2[H+] M–1 s–1} to give 3-nitropyridine. From the available evidence the reactions were either intramolecular or took place in a solvent cage. Two mechanisms are found to be in accordance with the reported evidence: the nitro group either migrated as a nitronium ion in a solvent cage or by a sigmatropic shift. The results from the nitration of a series of dimethylpyridines support the sigmatropic shift migration mechanism.

Degradation of Aflatoxins by Food Additives

Degradation of four aflatoxins (AFB1, AFB2, AFG1 and AFG2) by food additives was investigated. Pure aflatoxins were degraded by treatment with solutions of acidic food additives (hydrochloric acid:HCl and sulfuric acid:H2SO4), alkaline food additives (sodium bicarbonate:NaHCO3, sodium carbonate:Na2CO3, sodium hydroxide:NaOH, sodium sulfite:Na2SO3, and sodium hypochlorite:NaOCl) and neutral food additives (potassium metabisulfite:K2S2O5, sodium bisulfite:NaHSO3, sodium hydrosulfite:Na2S2O4, hydrogen peroxide:H2O2, sodium chlorite:NaClO2, and ammonium peroxodisulfate:(ÑH4)2S2O8). The aflatoxins were treated with these neutral food additives under several conditions, and the effects of treatment temperature, time, and concentration of food additives on aflatoxin degradation were studied. Potassium bromate (KBrO3), potassium nitrate (KNO3), and sodium nitrite (NaNO2) had no effect on aflatoxins. Of the aflatoxin added to corn, 20% AFB, remained after treatment with the solution of NaHSO3 (0.5%, 48 h), but all of the AFB1 was completely degraded by NaClO2 (0.25%, pH 4, 48 h) and (NH4)2S2O8 (0.25%, 48 h) at 60°C. Of the aflatoxins added to butter beans, less than 20 and 5% of AFB1 remained after boiling treatment with a 2 and 0.5% solution of Na2S2O4, respectively. These findings suggested that aflatoxins can be degraded or removed by treatment with food additives during food processing.

Personal Monitoring of Formaldehyde in the Atmosphere Using a Badge-Type Passive Sampler

A badge-type passive sampler has been developed for the determination of formaldehyde (HCHO) in the atmosphere. The filter used in the sampler to collect HCHO comprises Toyo No. 1 filter paper impregnated with a NaHSO3 solution. A passive sampler was attached around either the neck or chest of the examiner; after a definite time the sampler was recovered. The concentration of HCHO exposed on the filter of the sampler was then determined using a chromotropic acid-spectrophotometric method, and the HCHO concentration in the atmosphere was estimated. The permissible limit of HCHO concentrations to be measured with the sampler used in the study was 0.200–630 ppm-h as a time-weighted average concentration when monitored for 8 h. The reproducibility of the determined value of HCHO was excellent, with 4.3% (n=5) at the relative standard deviation. The recovery of HCHO exposed on the filter was 94.7%. The samplers exposed to HCHO showed no notable change in the HCHO concentration on filters either stored at room temperature or refrigerated for 2 weeks.

DPP Determination of Trace Level of As(III) and Total Inorganic Arsenic in Drinking Waters

Abstract A method for the determination and speciation of As(III), As(V) and total inorganic arsenic in drinking waters by Differential Pulse Polarography (DPP) is described. As(III) is determined directly and total inorganic arsenic is measured after reduction of electroinactive As(V). The latter is evaluated by difference. The method involves the removal of interfering ions by anion exchange with Amberlite IRA-400 and the reduction of As(V) to As(III) with a boiling solution of NaHSO3. The efficiency of both procedures is evaluated. The operational and analytical conditions are optimized in order to allow the detection of low arsenic levels. The detection and quantitation limits (8.16 and 9.88 ng/ml, respectively) and the precision of the decribed procedure are evaluated. They prove the usefulness of the method.

A Laboratory Evaluation of Two Methods for Measuring Low Levels of Formaldehyde in Indoor Air

Two methods for measuring formaldehyde at ppb levels–the modified pararosaniline (PRA) and the modified chromotropic acid (CTA)–were evaluated in a laboratory study. A dynamic double dilution system was used to generate controlled test atmospheres of formaldehyde by the catalytic depolymerization of trioxane. Impinger samples were collected from the sampling manifold and analyzed accordingly. Both methods demonstrated good precision (3.5% for the PRA and 3.4% for the CTA) but differed in accuracy and collection efficiency. Accuracy was 87.7±7.5% for the PRA and 92.5±4.2% for the CTA, while collection efficiency was 91.9±6.9% and 98.7±4.7% respectively. These differences were mainly due to the use of 1% NaHSO3 as the absorbing solution in the CTA method. Additionally, the NaHSO3 solution has the advantage of long sample preservation, making the modified CTA the method of choice in most non-industrial indoor air sampling situations.

DISULFIDE-ENRICHMENT IN WOOL BY TREATMENT WITH BIS (β-ISOCYANATOETHYL) DISULFIDE

In an attempt to obtain disulfide-enriched wool (fibers and fabrics), the reaction of wool with a disulfide-containing crosslinking agent, that is, bis (β-isocyanatoethyl) disulfide (BIED), was studied in dimethylformamide. BIED reacted mono-and bifunctionally with wool to form branches and crosslinks, respectively. The crosslinking efficiencies in the percent ratio of the number of the crosslinks (inter-and intrachenic) formed to the total disulfide introduced, which were obtained before and after reduction, ranged from 48% to 66%. The crosslink density of a BIED-treated fiber sample was determined by the method of Arai and Hanyu from Young's modulus in aqueous LiBr/butyl carbitol at 70°C. The crosslink density of the sample determined by the chemical analysis was 1.4 times that of the control wool, while the density determined from the physical method was two times. Supercontraction behavior of BIED-treated wool fibers was compared with that of hexamethylene diisocyanate-treated fibers in either an aqueous solution of NaHSO3, a disulfide reducing agent, or in formamide, a hydrogen bond breaking reagent. Hexamethylene diisocyanatetreated wool fibers did not supercontract in both media, while BIED-treated wool fibers with a low add-on supercontracted in aqueous NaHSO3 but did not in formamide. BIED-treated wool fibers with a higher add-on, however, did not supercontract in aqueous NaHSO3, probably because the excessive introduction of hydrophobic new crosslinks interferes with the penetration of the reducing agent.

Grafting onto wool. XI. Graft copolymerization of poly(vinyl acetate) and poly(methyl acrylate) onto reduced wool in presence of potassium persulfate–ferrous ammonium sulfate (KPS—FAS) system as redox initiator

AbstractIn an attempt to ascertain the role of—SH groups of Himachali wool during graft copolymerization, poly(viny acetate) (PVAc) and poly(methyl acrylate) (PMA) were graft copolymerized onto reduced wool by using potassium persulfate—ferrous ammonium sulfate (KPS—FAS) redox pair in aqueous medium. Reduction of wool was carried out by sodium bisulfite solution of varying concentrations for different reaction periods. Concentration of reducing agent and the extent of reduction were found to influence grafting of vinyl monomers. Maximum grafting of methyl acrylate (MA) and vinyl acetate (VAc) occurred when wool was reduced by 1% and 0.5% NaHSO3 solution, respectively, for 24 h. Increase in percent grafting of MA onto reduced wool compared to that of unreduced wool has been ascribed to the production of more—SH groups by reduction of—SS—groups of wool fiber.

Effect of dissociation on the absorption rate of dilute SO2.

Absorption of dilute SO2 in water, aqueous solutions of H2SO4, NaHSO3 and Fe(II)-edta was theoretically and experimentally investigated. It was found that the dissociation of SO2 in solutions (SO2+H2O→←HSO-3+H+) has a remarkable effect on its absorption rate. The presence of H2SO4 or NaHSO3 prevents the dissociation of SO2, resulting in lower absorption rate than that in pure water. The absorption rate in Fe(II)-edta solution was found to be faster than that into water because of the buffer capacity of Fe(II)-edta solution. The experimental results are satisfactorily explained by the theory of gas absorption accompanied by instantaneous reversible reactions.

Effects of SO2 on Photosynthesis and Nitrogen Fixation

AbstractResponses of photosynthesis and nitrogen fixation to NaHSO3 (10−5−5 × 10−3M) were investigated in the lichen Stereocaulon paschale (L.) Fr. and the blue‐green alga Anabaena cylindrica Lemmermann. The treatments were performed in buffered media with varying pH (5.8–8.1) and light conditions (0–32 W × m−2). The activities of the intact organisms were investigated, under the same environmental conditions, with 14C liquid scintillation and acetylene reduction techniques respectively.The nitrogen fixation proved to be more susceptible than photosynthesis, in both organisms, and in all cases treatments at pH 5.8 were more inhibitory than at higher pH‐values. Treatment with 5 × 10−4M NaHSO3 at pH 5.8 caused no reduction of photosynthesis in S. paschale, while the inhibition of nitrogen fixation was 97%. For A. cylindrica the corresponding values were 40% and 75% respectively. Short‐time treatments of A. cylindrica showed that the nitrogen fixation was more rapidly affected than photosynthesis. The inhibition of nitrogenase activity and CO2‐fixation was smaller in the dark and increased at higher light intensities. Both processes showed a good capacity for recovery after removal of the NaHSO3 solution. Also the clumping ability of A. cylindrica was disturbed by NaHSO3 treatments.