Redox Potential Eh Research Articles

Amelioration of iron deficiency in rice and transformations of soil iron in coarse textured soils of Punjab, India

The productivity of coarse textured soils is generally low due to their poor inherent fertility in particular due to the low water holding capacity and nutrient availability. With the adoption of irrigated upland rice‐wheat cropping system on these soils where water cannot be impounded even after puddling, widespread deficiency of Fe has been reported in rice. Iron deficiency is most severe when the coarse textured soils are brought under rice cultivation for the first time. Iron deficiency in rice grown on such soils results from inherent low Fe content of soils and unfavorable conditions for reduction of Fe3+ to Fe2+. In field experiments, soil application of even 200 kg FeSO47H2O ha−1 proved inferior compared with 3‐sprays of 1% FeSO47H2O solution for remediation of Fe deficiency in rice. Incorporation of Sesbania aculeata green manure before transplanting rice was very effective in ameliorating Fe deficiency and significantly increasing rice yield and DTPA‐extractable Fe in soils. Results of greenhouse experiments demonstrated that incorporation of Sesbania green manure markedly decreased pH and redox potential (Eh) and increased ionic strength, partial pressure of CO2 and Fe concentration in soil solution. Chemical equilibria studies showed that Fe solubility was controlled by Fe(OH)3‐Fe2+ system throughout the periods of submergence and after the peak of Fe2+ in the soil solution Fe3(OH)8‐Fe2+ and Fe(OH)3‐Fe3(OH)s systems were predominant. Under field conditions transformations of a part of Fe from the crystal lattice and/or cristalline oxides of Fe to amorphous oxides and bound by carbonates over the years increased the availability of Fe in the soils.

Copper adsorption behavior of three Malaysian rice soils

Copper (Cu) deficiency exists in different rice growing areas of Malaysia. A study on Cu adsorption was carried out in three Malaysian rice soils (Idris, Tebengau, and Kangar series) using six levels of Cu (0, 100, 200, 300, 400, and 500 ug g‐1). The data on Cu adsorption were fitted into Langmuir, Freundlich, and Temkin equations. Adsorption data were also correlated with pH, cation exchange capacity, and organic matter content of the soils. The effect of Cu addition on redox potential (Eh) of the soils was also measured. The Eh values were correlated with equilibrium solution Cu concentrations. Copper adsorption increased gradually with increasing level of added Cu in all the soils. The rate of increase was the highest in Kangar series followed by Tebengau and Idris, respectively. Correlation between Cu adsorption and pH was significant (r=0.772) whereas correlation of adsorption with either organic matter content or cation exchange capacity was nonsignificant. Copper adsorption in two soils (Idris and Tebengau) fitted Langmuir, Freundlich, and Temkin equations whereas Cu adsorption in the Kangar soil fitted Freundlich and Temkin equations. Redox potential (Eh) of the soils increased gradually with increasing level of added Cu. The rate of increase was the highest in Idris followed by Kangar and Tebengau soils, respectively. The relationship between equilibrium solution Cu concentration and redox potential was significant. The results of this study indicated that copper adsorption is mainly dependent on soil pH. In soils with higher adsorption capacity, more Cu fertilizer may be needed to get immediate crop response.

Effect of pH and Eh on the sorption of selected radionuclides

The effect of the pH of the aqueous phase on the sorption of134Cs,85Sr,125I and99Tc radionuclides has been investigated. Different types of bentonites from north-western Bohemia 85 in mixture with quartz sand have been used for the experiments with134Cs and85Sr. ThK d values have been determined using a batch method. The effect of the redox potential Eh on the sorption of radionuclides and the speciation of radionuclides125I and99Tc has also been investigated. Polarography has been used for speciation of the radionuclides.

Interferences between root plaque formation and phosphorus availability for isoetids in sediments of oligotrophic lakes

Freshwater isoetids exchanges a high proportion of the photosynthetically produced oxygen over the extensive root system and, therefore, they influence the redox potential (Eh) and phosphorus (P) availability in their sediments. Because isoetids rely on the sediment for P uptake, P may be a key element in controlling the distribution of isoetids. We investigated biomass and P availability to isoetids (Littorella uniflora and Isoetes lacustris) in a transect of five stations across the littoral zone in oligotrophic Lake Kalgaard, Denmark. At the two shallowest stations (0.6 and 1.0 m depth) the redox potential in the low organic rhizosphere sediment was high (>300 mV) and low concentrations of reduced exchangeable iron (Fe) and manganese (Mn) compounds in the sediment and of precipitated Fe and Mn oxides on isoetid roots (plaques) were found. The concentration of sediment P pools was low and so was isoetid P content and isoetid biomass. At intermediate water depth (1.8 m) sediment Eh was high (∼300 mV) and isoetids showed low root plaque concentrations. However, higher concentration of P pools in the rhizosphere was found at 1.8 m and isoetids showed the highest P content and biomass. At deeper stations (2.8 and 4.6 m depth) Eh was low (<100 mV) in the high organic rhizosphere and high concentrations of plaques were found. The P content in the sediment was high, however, isoetids showed low biomass and low P content. We suggest that the low P content in isoetids growing on P rich organic sediments is partly due to inhibition of the P uptake because of adsorption of P to the oxidized Fe and Mn plaques. However, ratios between oxidized Fe and Fe-bound P, 150 for plaques and 40 for sediment, suggest the isoetids are able to access some of the P that is bound in the plaques. The pools of dissolved P in the porewater were 25–1100 times lower than the estimated annual P requirement for net growth of isoetids while solid fraction P pools were 20–260 times higher than the estimated annual P requirement. Clearly, the oxygen release from isoetid roots decreases the availability of P either by keeping the entire rhizosphere oxidized (low organic sediments) or by the formation of root plaques (high organic sediments).

Preparation and E h --pH diagrams of Fe(II)--Fe(III) green rust compounds; hyperfine interaction characteristics and stoichiometry of hydroxy-chloride, -sulphate and -carbonate

Fe(II)--Fe(III) hydroxy-chloride, -sulphate and -carbonate were prepared by oxidation of a ferrous hydroxide precipitate in anion-containing aqueous solutions. The compounds are characterized by monitoring the redox potential Eh and the pH of stochiometric suspension vs time with the appropriate concentration ratios. X-ray diffraction allows us to characterize the crystal structure by distinguishing “green rust one” (GR1) from “green rust two” (GR2). Since green rusts (GRs) are of a pyroaurite-sjogrenite-like structure, i.e., consisting of intercalated foreign anions and water molecules in the interlayers between the brucite-like layers of Fe(OH)2, their chemical formulae can be determined from the Mossbauer spectra. Three quadrupole doublets are observed: D1 and D2 correspond to a ferrous state with isomershift IS of about 1.27 mm s-1 and quadrupole splittings QS of about 2.85 and 2.60 mm s-1, respectively, whereas D3 corresponds to a ferric state with IS and QS of about 0.4 mm s-1. The hyperfine parameters of these doublets are similar from one green rust to another but their intensity ratios vary considerably. Finally, Eh and pH equilibrium diagrams of the Fe species in the presence of chloride, sulphate and carbonate anions contained within the water solution are drawn and the thermodynamic conditions of existence and degrees of oxidation of green rusts are discussed.

Stability behavior of soil colloidal suspensions in relation to sequential reduction of soils

Flocculation and dispersion of clay particles in in vitro waterlogged soils at 8, 18, 28, and 38°C were investigated with some indications of soil reduction. Above 28°C, waterlogging for 1-week in the six soils caused a significant decrease in the turbidity of their colloidal suspensions. The decrease in the turbidity, i.e., the flocculation of the clay particles, was evident with (i) a decrease of redox potential (Eh) of the soils, (ii) an increase in the values of electric conductivity (EC) and water-soluble cations (WSCs: Fe2+, Ca2+, Mg2+, NH4 + etc.) in the solutions, and (iii) an increase in the amounts of volatile fatty acids (VFAs: acetic, propionic, and n-butyric acids) in the soils. Soil incubation at 8°C retarded the decrease in Eh, the increase in the values of EC, WSCs, and VFAs, and the decrease in the turbidity. At 38°C, samples of four soils waterlogged for 4 weeks showed a low turbidity with a low Eh, and high values of EC, WSCs, and VFAs. The samples of other two soils, however, exhibited a significant increase in the turbidity, viz. the dispersion of clay particles, with an increase in pH and decrease in the values of EC, WSCs, and VF As under low Eh. The observed flocculation and dispersion of clay particles in the waterlogged soils were discussed in relation to chemical changes under sequential reduction of soils, particularly change in ionic strength of soil solutions largely due to the (i) dissolution and precipitation reactions related to Fe2+ and Fe(III) and (ii) cation exchange reactions between Fe2+ and other exchangeable cations on clay surfaces.

Soil and groundwater chemistry and vegetation distribution in a desert playa, Owens Lake, California

Generation of fine particulate dust (PM10)from the Owens Lake play a creates a severe air pollution hazard in the western Great Basin of the United States. One proposed mitigation strategy involves establishment of native vegetation to stabilize and trap fugitive sand. This study investigated soil and groundwater chemistry and the distribution of native plant species in relation to salts and toxic ions in the soil and groundwater along four transects from vegetated dunes or shorelines to nonvegetated playa surfaces. Soluble salts in soil extracts along all four transects were dominated by Na+(mole fraction = 0.43–0.47), HCO3/CO3 2‐ (020–026), and Cl‐ (0.15–022). Distichlis spicata (L.) E. Greene and Atriplex parryi S. Watson were found at locations with very high salt concentrations (44–77 dS m‐1 saturated paste electrical conductivity EC). The ultimate limitation to plant distribution, however, appears to result from shallow anoxic groundwater restricting rooting depth. Groundwater chemistry was characterized by high pH (93–10), EC (3–54 dS m‐1), and sodium adsorption ratio (46–1223), and low redox potential (Eh = 7 to ‐240 mV). Shallow anoxic groundwater restricted the rooting zone of both D. spicata and A. parryi, and no vegetation was found when anoxic conditions were within 70 cm of the surface. An oxidized rooting zone greater than ∼1.5 m depth was present where cover of D. spicata and A. parryi was adequate for sand stabilization. Artificial dunes created with sand fences appear to be a substrate from which salts and borate‐B could be leached to levels tolerable by these species, and at the same time these raised microsites would provide a rooting zone of adequate depth for persistence of either naturally or artificially established native species.

Influence of redox potential on phosphate-uptake by sediments in two sub-tropical eutrophic lakes

Biogeochemical reactions in shallow eutrophic lakes areaffected bythe changes in redox potential (Eh) as bottom sedimentsundergotemporal resuspension and settling. The stability of varioussediment P fractions and kinetics of P-uptake were evaluatedfortwo sub-tropical lakes (Lake Apopka and Lake Okeechobee,Florida)using sediment suspensions in closed systems maintained atvariousEh levels ranging from −235 to 555 mV. Redox potential hadminimal effect on the stability of NaOH-P (Fe-/Al-bound P plusmoderately resistant organic P) and HCl-P (Ca-/Mg-P) fractionsinLake Apopka sediments. Increases in ortho-P and NH4Cl-P(loosely-bound P plus labile organic P) concentrations wereobserved in highly reduced (Eh = −225 mV) Apopkasediments.Phosphate solubility diagrams and mineral equilibriacalculationssuggest that P-uptake by Apopka bottom sediments at elevated Pconcentrations (ortho-P ≤ 110 μM) was due toformationof Ca-P compounds and/or co-precipitation of P withCaCO3. Incontrast, the ortho-P concentrations for Lake Okeechobeebottomsediments increased exponentially with decreasing Eh. Thequantityof NaOH-P fractions for these sediments decreased withdecreasingEh, suggesting the release of Fe- and Mn-bound P intosolution.Phosphate-uptake by Okeechobee bottom sediments (pH 7.5,ambient)followed first order kinetics, yielding a rate constant (k)of 0.51 ± 0.05 h-1. Unlike that of Apopka, the mudsediments in Lake Okeechobee have strong affinity for P ineitheraerobic or anaerobic conditions. Results suggest that even incalcareous systems, Fe and Al, when present in highconcentrations(as in the case of Lake Okeechobee), are actively involved inregulating P-uptake and geochemistry.

Transformation of N-, O-, and S- heterocycles (NOSHs) in estuarine sediments: Effects of redox potential and sediment particle size

The transformation of 19 N-, O-, and S- heterocycles (NOSHs) was examined in estuarine sediment-water microcosms. The effects of redox potential (Eh) and sediment particle size on compound transformation rates were evaluated, and stable products were identified. Results from stirred, controlled Eh/pH microcosms (CEPMs) showed that most of the NOSHs were significantly transformed under oxidized and reduced conditions over 15 week incubations, and the resulting product distributions were similar. In general, the rates and extent of transformation were greater in oxidized sediments of low surface area vs. those with high particle surface area and reduced redox conditions. Further experiments in sealed, unstirred microcosms also showed that NOSH transformation proceeded more slowly and on fewer compounds in fine vs. coarser grained sediments under oxidized conditions. Unlike the stirred systems, however, NOSH transformation rates were similar or greater under reduced vs. oxidized conditions. Thus, reduced, methanogenic clay of high surface area displayed some of the fastest rates of NOSH transformation. Data from liquid-liquid partitioning experiments suggested that this effect was related to the formation of NOSH complexes with iron and perhaps other redox-active metals in sediments.

Redox potential as a controlling factor in enhancing carbon tetrachloride biodegradation

Biodegradation of hazardous waste is often the most cost-effective technique suitable for purifying large quantities of polluted groundwater and industrial effluents. In an effort of optimizing environmental conditions for microorganisms to degrade carbon tetrachloride, culture redox potential (Eh) was demonstrated as having a critical role. The microorganisms tested were isolated from contaminated field sites and included Pseudomonas cepacia and Providencia stuartii. Ti(III) citrate was used as a reducing agent to poise Eh at designed values. Over 99% degradation of carbon tetrachloride was effected in 3 days at −250 mV ≤ Eh ≤ −200 mV. Lesser rates were observed at Eh ≥ 0 mV. Kinetic analysis indicated that the overall degradation rate constant increased from 2.75×10−3 h−1 to 4.75×10−2 h−1 by controlling Eh at about −200 mV compared with Eh at ≥ 0 mV. Results indicated that the implementation of critical redox potential may be effective in optimizing CT biodegradation activity.

Sorption behavior of Np (IV), Np (V) and Am (III) in the disturbed zone between engineered and natural barriers

In order to be more confident of the performance assessment of high-level radioactive waste disposal, radionuclide transport must be investigated in more detail in the disturbed host rock region adjacent to the engineered barriers where disturbance has been introduced during the construction and waste-emplacement period. Geochemical, hydrological, and rock-mechanical properties should be quite different from those of undisturbed host rock. We have to elucidate the effect of bentonite intrusion into intersecting fractures from the standpoint of radionuclide confinement. In the present work, sorption distribution ratios (Kd's) of Np and Am are measured experimentally for various values or redox potential (Eh) in a simulated rock fracture filled with bentonite. The Kd of Am is approximately 6.5×103 ml/g and found to be insensitive to the redox potential. Under anaerobic conditions, the Kd of Np is approximately 6×104 ml/g. Under aerobic conditions, Kd is as small as 30 to 100 ml/g. This is the first report to measure the sorption behavior of Np and Am in a simulated rock fracture filled with bentonite (namely, in a disturbed zone) under pH, Eh and ionic strength control. We aan make use of these Kd data for numerically evaluating the mass transfer from bentonite filled fractures into the water-flowing fracture network1.

Redox potential as a controlling factor in enhancing carbon tetrachloride biodegradation

Biodegradation of hazardous waste is often the most cost-effective technique suitable for purifying large quantities of polluted groundwater and industrial effluents. In an effort of optimizing environmental conditions for microorganisms to degrade carbon tetrachloride, culture redox potential (Eh) was demonstrated as having a critical role. The microorganisms tested were isolated from contaminated field sites and included Pseudomonas cepacia and Providencia stuartii . Ti(III) citrate was used as a reducing agent to poise Eh at designed values. Over 99% degradation of carbon tetrachloride was effected in 3 days at −250 mV ≤ Eh ≤ −200 mV. Lesser rates were observed at Eh ≥ 0 mV. Kinetic analysis indicated that the overall degradation rate constant increased from 2.75×10−3 h−1 to 4.75×10−2 h−1 by controlling Eh at about −200 mV compared with Eh at ≥ 0 mV. Results indicated that the implementation of critical redox potential may be effective in optimizing CT biodegradation activity.

Effect of temperature on rice growth in nutrient solution and in acid sulphate soils from Vietnam

Climatic and soil factors are limiting rice growth in many countries. In Vietnam, a steep gradient of temperature is observed from the North to the South, and acid sulphate soils are frequently devoted to rice production. We have therefore attempted to understand how temperature affects rice growth in these problem soils, by comparison with rice grown in nutrient solution. Two varieties of rice, IR64 and X2, were cultivated in phytotrons at 19/21 degrees C and 28/32 degrees C (day/night) for 56 days, after 3 weeks preculture in optimal conditions. Two soils from the Mekong Delta were tested. Parallel with the growing experiments, these two soils were incubated in order to monitor redox potential (Eh), PH, soluble Al and Fe, soluble, and available P. Tillering retardation at 20 degrees C compared to 30 degrees C was similar in nutrient solutions and in soils. The effect of temperature on increasing plant biomass was more marked in solutions than in soils. The P concentrations in roots and shoots were higher at 20 degrees C than at 30 degrees C, to such an extent that detrimental effect was suspected in plants grown in solution at the lowest temperature. The translocation of Fe from roots to shoots was stimulated upon rising temperature, both in solutions and in soils. This led to plant death on the most acid soil at 30 degrees C. Indeed, the accumulation of Fe in plants grown on soils was enhanced by the release of Fe2+ due to reduction of Fe(III)-oxihydroxides. Severe reducing conditions were created at 30 degrees C: redox potential (Eh) dropped rapidly down to about 0 V. At 20 degrees C, E(h) did not drop below about 0.2 V, which is a value well in the range of Fe(III)/Fe(II) buffering. Parallel to Eh drop, PH increased up to about 6-6.5 at 30 degrees C, which prevented plants from Al toxicity, even in the most acid soil. Phosphate behavior was obviously related to Fe-dynamics: more reducing conditions at 30 degrees C have resulted in enhancement of available P, especially in the most acid soil.

Transfer of technetium in the soil-rice plant system

In order to assess the behavior of Tc in flooded soil-plant systems, laboratory experiments have been done using95mTc as a tracer. Two common soil types in Japan, Andosol and Gray lowland soils, were used. Soil-plant transfer factors of Tc in rice grain were very low, i.e. 5×10−5 for Andosol and 6×10−4 for Gray lowland soil. It was found that the Tc concentrations in rice plants were influenced by those in soil solutions. Concentrations of95mTc in both soil solutions decreased rapidly in the early period of cultivation. It was observed that redox-potential (Eh) also decreased markedly following flooding. A relationship was found between the decrease of the95mTc concentrations in soil solutions and the drop of Eh in the soils. The Tc (VII) added to soil was transformed to insoluble Tc (IV) under the reduced conditions existing in flooded soil.

テクネチウムの土壌中存在形態に関する考察 抽出実験におけるｐＨおよび酸化還元電位（Ｅｈ）の経時変化

テクネチウムの土壌中存在形態に関する考察 抽出実験におけるｐＨおよび酸化還元電位（Ｅｈ）の経時変化

Changes in redox potential of Escherichia coli culture and in extracellular glutathione status under osmotic shock

When non-growing Escherichia coli cells were inoculated into the fresh isotonic medium or subjected to hypoosmotic shock an N-ethylmaleimide-reversed drop in redox potential Eh was observed. Hyperosmotic shock reversed the drop in Eh which has been demonstrated in the situations described earlier (exhaustion of glucose, treatment with acetate or inhibitors of proteine synthesis). An increase in the level of extracellular GSH and in the GSH: GSSG ratio outside cells was found when glucose was exhausted in E. coli culture. Hyperosmotic shock led to an opposite process: the level of extracellular GSH and the GSH: GSSG ratio decreased. These data suggest that the changes in the redox status of extracellular glutathione may contribute to the observed changes in Eh.

Phosphorus sorption characteristics in acid sulfate soils of Thailand: Effect of uncontrolled and controlled soil redox potential (Eh) and pH

Two laboratory experiments were conducted to study phosphorus sorption characteristics in acid sulfate soils (para- and actual-acid sulfate soils) of Thailand. In one experiment the soils were subjected to oxidized and reduced conditions, in another they were maintained under different controlled pH (4.0, 5.0, and 6.0) and Eh (+600, +400, +300, +200, +100, and 0 mV) conditions. In both experiments the soils were kept in stirred suspensions with a soil to 0.01 M CaCl2 solution ratio of 1:7 for 6 weeks. After the incubation period, the soil suspensions were equilibrated with KH2PO4 ranging from 0 to 500 mg P kg−1 soil. Sorption isotherms were described by the classical Langmuir equation. The results from the first experiment showed that more native insoluble P was released under reduced than oxidized conditions, with more being released from para-acid sulfate soil than from actual acid sulfate soils. Soil reduction also caused an increase in P-sorption. Less P-sorption occurred under both conditions in para-acid sulfate soil than in actual acid sulfate soils. In the second experiment, the P-sorption of both actual and para-acid sulfate soils was significantly affected by soil Eh, pH, and their interactions. The P-sorption increased significantly with increasing pH and decreasing Eh. At pH 4.0, a considerable increase in P-sorption occurred as Eh decreased from +400 to +300 mV, whereas at pH 5.0 and 6.0 an obvious change in P-sorption occurred when Eh decreased from +300 mV to +200 mV. The actual acid sulfate soil sorbed more P than did para-acid sulfate soil. Significant correlation between P-sorption parameters and iron-oxides indicated the primary role of iron-oxides in P-sorption of acid sulfate soils of Thailand. Aluminum-oxides seemed to play a secondary role in P-sorption of these soils. Manganese also showed a significant effect on P-sorption.

Electrolytic Reduction of Soil Suspensions

A three-electrode system and a precision potentiostat were used in the electrolytic reduction of suspensions of two soils. A saturated calomel reference electrode served as a potentiometric probe of the interfacial potential at the surface of the working electrode. Solution resistance between these two electrodes was minimized by suspending the soils in 1 M KCl. In one set of experiments electrolysis was carried out for 4 hours at a range of applied potentials, while in another set of experiments electrolysis at one of two applied potentials was continued until an apparent equilibrium had been reached. Faradic current, suspension redox potential (Eh) and pH, and solution concentrations of Fe were measured as functions of time and applied potential. As evidenced by the appearance of Fe in solution, reduction of Fe (III) compounds began to occur at an applied potential of −48 mV vs. the standard H electrode. This is more negative than the potentials at which Fe first appears in flooded soils. The pH values of the suspensions increased as the applied potentials became more negative and as the duration of electrolysis increased. Measured suspension Ehs were initially lower than the applied potentials, but after 20 h of electrolysis these two quantities had similar values, suspension pH and solution concentrations of Fe had reached relatively constant values, and the faradic current had declined to background levels. Approximately 75% of the citrate-bicarbonate-dithionite-extractable Fe of both soils had been reduced after 20 h of electrolysis at an applied potential of −359 mV. This electrolytic reduction technique potentially offers an alternative in the study of soil redox process under controlled Eh condition.

The effect of a redox agent, methylene blue, on the survival ofPorphyromonas gingivalis in vitro

Methylene blue, at a concentration of 1.0 mg/ml, was able to raise the redox potential (Eh) of pre-reduced culture medium from −288 mV to −154 mV and to poise the medium at an Eh of −171 mV during 48-h incubation in an anaerobic atmosphere. Addition of the dye to suspensions of the anaerobic periodontopathogen,Porphyromonas gingivalis, to give a final concentration of 1.0 mg/ml raised their Eh to −125 mV. During a 24-h period of anaerobic incubation, the dye maintained the Eh at a level (−150 mV) that was more than 200 mV higher than control, dye-free suspensions, and this was accompanied by at least a 6-log reduction in the viable count. The bactericidal effect of the methylene blue could be counteracted by the reducing agent dithiothreitol at a concentration of 2.0 mg/ml, which lowered the Eh to a level (−333 mV) similar to that of controls. These results have demonstrated that the presence of 1.0 mg/ml methylene blue, in its oxidized form, in an environment is inimical to the survival ofP. gingivalis and that this is related, directly or indirectly, to its ability to raise the Eh of the environment. Topical application of methylene blue, or other redox agents, may be an effective means of eliminating this organism from the periodontal pockets of patients with chronic periodontitis.

Vertical distribution of several chemical components in the South‐Western region of the Black Sea

The vertical distribution of several chemical components (NH3, As, P, Zn, Mn, Cu, Fe, O2, alkalinity, salinity and pH) and physical characteristics (suspended matter, T and redox potential Eh of the water phase) has been studied in the marine environment of the south‐western part of the Black Sea. Possible relationships and similarities of different components are checked by the use of cluster analysis. Some explanations of the structure of the clusters formed are suggested taking various aspects of the marine chemistry into account.