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PubMed2001

The nitrogen composition of streams in upland Scotland: some regional and seasonal differences.

The nitrogen (N) composition of streams draining four upland regions of Scotland was compared in samples collected monthly between April 1997 and April 1998. Stream samples were analysed for total N (TN), particulate N (PN), nitrate (NO3), ammonium (NH4), dissolved organic N (DON) and dissolved organic carbon (DOC). Concentrations of TN were small, generally less than 1 mg l(-1) , dominated by dissolved forms of N, and varied significantly between upland regions. Nitrate accounted for most of the variability in TN; largest concentrations were observed in the Southern Uplands and smallest concentrations were observed in the Highlands. Nitrate concentrations were positively correlated with the percentage cover of improved grasslands and brown forest soils and negatively correlated with the percentage cover of peat. Concentrations of DON also varied between regions, but to a lesser extent than those of NO3. Largest concentrations occurred in SW Scotland and smallest concentrations in the Cairngorms. Although a significant positive correlation between DON and DOC was observed, stream water DON content was not related to the percentage cover of peat in the catchment, as was the case for DOC. The average DOC:DON ratio was narrower for streams in the Southern Uplands than for those in the Cairngorms and Highlands. Nitrate and DON displayed contrasting seasonal trends; NO3 concentrations were larger in the winter while DON concentrations were larger in the summer. Only a small proportion, < 8% and < 7%, of TN was PN and NH4, respectively, the majority of N was present as either NO3 or DON. Nitrate was the dominant fraction (58-65%) in all regions except the Highlands where DON accounted for 57% of TN. However, the relative importance of the DON component increased in the summer in all regions. This study has demonstrated that the DON fraction is an important component of the total N transported by streams from upland catchments in Scotland. Thus, assessments of anthropogenic impacts on N losses from upland ecosystems need to consider not only the dissolved inorganic species but also DON.

Agriculture↗
PubMed2001

Is in-stream processing an important control on spatial changes in carbon fluxes in headwater catchments?

Data on small-scale spatial variations in instantaneous fluxes and concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and free carbon dioxide (CO2) are presented for a small acidic headwater stream in NE Scotland. Chloride is used as a conservative element to estimate additional, diffuse inputs of water into the main stem of the stream, other than those from tributaries. Downstream changes in instantaneous carbon fluxes were calculated and then used to estimate losses and gains of carbon within the stream system. Dissolved organic carbon concentrations in the stream ranged from 1.19-6.06 mg l(-1) at its source to a maximum of 10.0-25.3 mg l(-1) as the stream passed through deep peats; DOC concentrations then declined in the lower part of the catchment. DIC concentrations were initially low, increased to 1.5-3.0 mg l(-1) and then decreased to 0.1-1.65 mg l(-1) at the lowest site. Free CO2 concentrations increased from 0.35 mg l(-1) at the stream source to 3.30 mg l(-1) as the stream passed through the peat dominated area. Continually high inputs of CO2-rich water (> 6.0 mg l(-1)) from tributaries maintained these high concentrations in the main stem, until approximately 1.74 km downstream, when there was a rapid decline in concentration. Significant changes in DOC, DIC and CO2 fluxes occur over a distance of 2.7 km downstream from the stream source to the catchment outlet. Between 5.64-41.5 mg C s(-1) as DOC and 2.52-16.2 mg C s(-1) as DIC are removed from the water column. Between 6.81 and 19.0 mg C s(-1) as CO2 is lost along the stream length as progressive equilibration with the atmosphere occurs. We estimate that 11.6-17.6% of the total DOC flux is removed from streamwater by in-stream processes. Dissolved inorganic carbon (HCO3- and free CO2) losses are in excess of nine times its measured flux at the outlet of the catchment. These results suggest that in-stream processing of DOC and DIC and outgassing of CO2 are important controls on the spatial variability of carbon fluxes within headwater streams in upland catchments dominated by organic-rich soils.

Carbon↗
PubMed2001

Sulfate reduction in Lake Agmon, Israel.

Lake Agmon, a newly reflooded water body in the southern part of the Hula valley is characterized by a clear phase period in winter with almost no blooms of phytoplankton. Dense macrobenthos and algal blooms form in the lake during summer and autumn. High primary production and chlorophyll-a concentrations were measured in April and during the summer of 1997. Fresh organic matter in the sediments from the degradation and decomposition of the blooms together with high sulfate concentrations, allowed microbial sulfate reduction to occur. Sediment cores taken from different sites (peat and marl) during various seasons in 1997, showed high sulfate reduction rates in June in the marl region, and in September in the peat region (842 and 2834 nmol SO(4)2- reduced ml(-1) day(-1), respectively). In February, corresponding to the development and decline of macrophytes and algal blooms, lower rates of sulfate reduction were recorded (11 nmol SO(4)2- reduced ml(-1) day(-1)). Sulfate reduction is limited by the supply of organic matter and is one of the major processes contributing to the mineralization of organic matter in this lake.

Chlorophyll↗
PubMed2002

Prediction of the effects of soil-based countermeasures on soil solution chemistry of soils contaminated with radiocesium using the hydrogeochemical code PHREEQC.

For agriculturally used areas, which are contaminated by the debris from a nuclear accident, the use of chemical amendmends (e.g. potassium chloride and lime) is among the most common soil-based countermeasures. These countermeasures are intended to reduce the plant uptake of radionuclides (mainly 137Cs and 90Sr) by competitive inhibition by chemically similar ions. So far, the impacts of countermeasures on soil solution composition - and thus, their effectiveness - have almost exclusively been established experimentally, since they depend on mineral composition and chemical characteristics of the soil affected. In this study, which focuses on caesium contamination, the well-established code PHREEQC was used as a geochemical model to calculate the changes in the ionic compositions of soil solutions, which result from the application of potassium or ammonium in batch equilibrium experiments. The simple ion exchange model used by PHREEQC was improved by taking into account selective sorption of Cs+, NH4+ and K+ by clay minerals. Calculations were performed with three different initial soil solution compositions, corresponding to particular soil types (loam, sand, peat). For loamy and sandy soils, our calculational results agree well with experimental data reported by Nisbet (Effectiveness of soil-based countermeasures six months and one year after contamination of five diverse soil types with caesium-134 and strontium-90. Contract Report NRPB-M546, National Radiation Protection Board, Chilton, 1995.). For peat, discrepancies were found indicating that for organic soils a reliable set of exchange constants of the relevant cations still has to be determined experimentally. For cesium, however, these discrepancies almost disappeared if selective sites were assumed to be inaccessible. Additionally, results of sensitivity analyses are presented by which the influence of the main soil parameters on Cs+ concentrations in solution after soil treatment has been systematically studied. It is shown that calculating the impacts of soil-based chemical countermeasures on soil solution chemistry using geochemical codes such as PHREEQC offers an attractive alternative to establishing these impacts by often time-consuming and site-specific experiments.

Agriculture↗
PubMed2002

Metal sorption to natural filter substrates for storm water treatment--column studies.

Storm water generated from road runoff contains pollutants such as metals that are either dissolved in storm water or bound to particulates. Using detention ponds for the treatment of storm water from road runoff, where particles can settle, can reduce the level of particulate-bound metals in the water, while small particles and dissolved matter pass through the detention pond. Some of these metals can be removed by filtrating water through specially constructed filter systems. This investigation is a laboratory study where different filter substrates were tested in order to evaluate their efficiency in reducing heavy metals from water. Metal solutions were filtered through columns filled with various substrates consisting of combinations of calcium silicate rock (opoka), zeolite and peat. The metal-removal efficiency was correlated to hydraulic load, and for the metal species the reduction efficiency decreased with increased hydraulic load. Mixtures of opoka and zeolite were found to be superior to the other filter-substrate combinations tested with regard to both hydraulic aspects and removal efficiency. Peat mixed with the calcium silicate rock was not successful due to clogging which stopped the experiment. A manufactured product made from the calcium silicate rock (burned opoka) was found to be less useful because of its calcium oxide (CaO) content. Among the tested filter substrates, mixtures of opoka and zeolite seemed to be the most useful compositions with respect to reduction-efficiency and clogging aspects. The removal capacity of metals varied from 0.6 to 1.8 kg m(-3) depending on the metal and the filter substrate.

Calcium Compounds↗
PubMed2003

Sorption of metals onto natural organic matter as a function of complexation and adsorbent-adsorbate contact mode.

The effect of complexing anion and adsorbate-adsorbent contact mode (static equilibrium or dynamic non-equilibrium) on binding and partition of Cu(2+), Cd(2+) and Zn(2+) onto organic matter (exemplified in a low-moor peat) was studied. The study comprised comparative batch and column flow-through sorption experiments on monometallic solutions of Me-Cl and Me-SO(4) salts, at pH 4.0, and sequential fractionation of sorbed metals with respect to binding strength. Both the presence of an anion having complexing properties (Cl(-)) as well as a contact mode was found to quantitatively and qualitatively affect the sorption capacity and binding strength of organic matter (peat) for metal ions. Complexing effect of Cl(-) on metal ions resulted mostly in reduction of metal ability to form strongly bound metal-organic compounds, in accordance with the order of stability constant of complex ions log K: Cd>Zn>Cu. Flow-through (dynamic) contact mode, which is the most appropriate to simulate environmental conditions, appeared to strongly attenuate the complexing effect of chloride ions on Cd and Zn sorption, and significantly enhance sorption capacity also in the absence of complexing ions. For Cd, it was mainly due to the enrichment in the strongly bound "insoluble organic" fraction, while for Zn the quantitative increase of sorption capacity did not alter significantly its partitioning. Neither a quantitative nor qualitative effect of contact mode on Cu binding was observed. Complex and diverse effects of different environmental parameters on metal sorption capacity and binding strength onto organic matter, which strongly influence metal mobility, leads to the conclusion that the correct simulation of these parameters for ecotoxicological testing is crucial for the reliable predicting of metal bioavailability under actual terrestrial environmental conditions.

Adsorption↗
PubMed2002

Direct interface of chemistry to microbiological systems: membrane inlet mass spectrometry.

Direct measurement of dissolved gases and low molecular weight volatiles through permeable membranes (e.g. 50-microm-thick silicone rubber), provides an invaluable tool for the investigation of the activities of microorganisms in the laboratory and in their natural environments. Multiple molecular species are monitored at a single point. Fast response times (t(90%)<1 min) and long-term stability, (<1% week(-1)); high specificity and high sensitivity (e.g. 0.2 microM for O(2), <0.5 mM for ethanol), provides a technique that can provide information on the kinetics of processes over many decades (10(0)-10(6)) of minutes. Spatial resolution of <1 mm enables 3D mapping of gases in complex ecosystems (sediments, peat, soils, biofilms, foodstuffs). Results with membrane inlet mass spectrometry (MIMS) when used in conjunction with confocal scanning laser microscopy, provides a powerful approach to the analysis of kinetic and spatial aspects of natural environments. Examples discussed are peat cores and cheese.

Bacteria↗
PubMed2000

Working for a dustbath: are hens increasing pleasure rather than reducing suffering?

Dustbathing is one of the major behavioural systems of domestic fowl that is constrained by commercial caging systems. Although research conducted over the last 20 years has revealed a great deal about causation of dustbathing, attempts at measuring the importance to hens of having access to dustbathing substrate have proven difficult. Various economic techniques, operant conditioning and learning trials have been used to determine whether hens have a 'need' for dustbathing substrate or 'think' about dustbathing in the absence of substrate. In this study, we measured hens' willingness to work to obtain substrate for dustbathing using a vertically swinging door to which weights could be added. Hens were trained to push through the door to enter a goal box containing peat moss. The hens were subjected to two series of trials to compare the maximum weight that they would push to open the door when living in a cage and deprived of dustbathing substrate, with the maximum weight that they would push when living in a pen furnished with litter and a dustbath (non-deprived). Of the 10 hens that opened the door for access to peat moss, six hens pushed more weight when deprived, three hens pushed more weight when non-deprived and one hen pushed an equal amount of weight. Overall, the hens tended to push more weight (860+/-95.6 vs. 682.5+/-83.3 g; P<0.10, one-tailed paired t-test) and tended to make more attempts to open the door (P<0.10) when they were deprived than when they were non-deprived. Significantly more trials resulted in dustbathing when hens were deprived (P<0.01) suggesting that following deprivation, the hens were, in fact, more motivated to dustbathe. The results of these trials indicate that although deprived hens may be more motivated to dustbathe, and that most hens may be willing to work to obtain a dusty substrate when they can see it, they are not necessarily willing to work harder when they are in a state of deprivation than when they have recently dustbathed. These results are very difficult to explain using a 'needs' model of motivation in which deprivation leads to a state of suffering. They are much more consistent with an 'opportunity' model of motivation in which performance of the behaviour, when the opportunity presents itself, leads to a state of pleasure.

Journal Article↗
PubMed2002

Foliar and root uptake of 134Cs, 85Sr and 65Zn in processing tomato plants (Lycopersicon esculentum Mill.).

The results of an experimental study on the behaviour of 134Cs, 85Sr and 65Zn in processing tomato plants grown in peat substrate are presented. Plants were contaminated by wet deposition of 134Cs, 85Sr and 65Zn, either by sprinkling the above ground part at two phenological stages or by administering 134Cs, 85Sr and 65Zn to the soil. The plants contaminated at the second phenological stage intercepted 38.3% less than those contaminated at the first stage, although leaf area increased by more than double. Transfer coefficients from peat soil to ripe fruit for 134Cs are significantly higher than those for 85Sr and 65Zn. Leaf to fruit transfer coefficients for 134Cs are one order of magnitude higher than for 65Zn and two orders higher than for 85Sr. Only when deposition affects fruits, as at the second phenological stage, are transfer coefficients to fruits similar for the three radionuclides.

Absorption↗
PubMed2003

Assessing drought-related ecological risk in the Florida Everglades.

In the winter-spring of 2001, South Florida experienced one of the worst droughts in its recorded history. Out of a myriad of ecological concerns identified during this time, the potential for catastrophic peat fire and negative impacts to wading bird reproduction emerged as critical issues. Water managers attempted to strike a balance between the environment and protection of water supplies for agriculture and urban interests. It became evident, however, that a broad-scale, integrated way to portray and prioritise ecological stress was lacking in the Florida Everglades, despite this being considered a necessary tool for addressing issues of environmental protection. In order to provide a framework for evaluating various water management operations using real-time information, we developed GIS-based indices of peat-fire risk and wading bird habitat suitability. These indices, based on real physical, chemical, and biological data, describe two ecological conditions that help define the physical and biological integrity of the Everglades. In addition to providing continuous, updated assessments throughout the drought period, we incorporated predictive models of water levels to evaluate how various water management alternatives might exacerbate or alleviate ecological stress during this time.

Animals↗
PubMed2003

Utilization of ICP/OES for the determination of trace metal binding to different humic fractions.

In this study, the use of inductively coupled plasma/optical emission spectrometry (ICP/OES) to determine multi-metal binding to three biomasses, Sphagnum peat moss, humin and humic acids is reported. All the investigations were performed under part per billion (ppb) concentrations. Batch pH profile experiments were performed using multi-metal solutions of Cd(II), Cu(II), Pb(II), Ni(II), Cr(III) and Cr(VI). The results showed that at pH 2 and 3, the metal affinity of the three biomasses exposed to the multi-metal solution that included Cr(III) presented the following order: Cu(II), Pb(II)>Ni(II)>Cr(III)>Cd(II). On the other hand, when Cr(VI) was in the heavy metal mixture, Sphagnum peat moss and humin showed the following affinity: Cu(II), Pb(II)>Ni(II)>Cr(VI)>Cd(II); however, the affinity of the humic acids was: Cu(II)>Pb(II), Cr(VI)>Ni(II)>Cd(II). The results demonstrated that pH values of 4 and 5 were the most favorable for the heavy metal binding process. At pH 5, all the metals, except for Cr(VI), were bound between 90 and 100% to the three biomasses. However, the binding capacity of humic acids decreased at pH 6 in the presence of Cr(VI). The results showed that the ICP/OES permits the determination of heavy metal binding to organic matter at ppb concentration. These results will be very useful in understanding the role of humic substances in the fate and transport of heavy metals, and thus could provide information to develop new methodologies for the removal of low concentrations of toxic heavy metals from contaminated waters.

Adsorption↗
PubMed1980

Degradation of humic acids, extracted from manure and soil by some streptomycetes and fungi.

Humate-decomposing microorganisms were isolated from alluvial soil, farmyard manure and peat by direct plating and enrichment techniques. Peat was found to harbour more of these organisms than soil and manure. Out of 21 actinomycetes and 6 fungi 9 and 3 isolates, respectively, were found to utilize manure-humate as a sole source of carbon and to a less extent as a source of both carbon and nitrogen in liquid medium. These efficient cultures were identified as Streptomyces spec. (A 11 and A 12). Str. candidus, Str. violaceoruber (A 41 and A 42), Str. rubescens, Str. garyphalus, Str. viridochromogenes, Fusarium solani, Aspergillus fumigatus, and Penicillium roseopurpureum. Additional sources of carbon and nitrogen stimulated microbial degradation of humate. Only five isolates formed a zone of decolourization on humate-containing solid medium. Soil humic acid was utilized by Str. candidus as a sole source of carbon and nitrogen, however, F. solani utilized it only in the presence of additional carbon and nitrogen sources. Extent of soil-humate degradation was less than manure-humate.

Culture Media↗
PubMed2001

Growth substrates made from duck excreta enriched wood shavings and source-separated municipal solid waste compost and separates: physical and chemical characteristics.

Production and use of compost is an effective means to reduce wastes, and offers a large potential as growth substrates and source of nutrients. The objective of this study was to determine the physical and chemical characteristics of duck excreta enriched wood shavings (DMC) and source-separated municipal solid waste (MSW) composts and separates, and to assess the physical characteristics of growth substrates made from these two composts and selected substrates. MSW compost separates were the following sizes: F1 > 4 mm diameter, 2 mm < F2 < 4 mm, 1 mm < F3 < 2 mm and F4 < 1 mm. Growth substrates were prepared by mixing DMC and F2 and F3 MSW separates (M/M ratios). Growth substrates A-E consisted exclusively of 10-60% DMC and 20-60% of MSW separates F2 and F3. Growth substrates F-J, and K-O were the same as substrates A E, with 15% M/M brick fragments or shredded plastic added as porosity agents, respectively. Growth substrates (BE/S) made of black earth (BE) and sandy loam soil (Ls) in a 1:4 (M/M) ratio, commercially available peat substrate (Pr) and an in-house sphagnum peat-based substrate (Gs) were used for comparison. Principal component analysis (PCA) showed that DMC was a better material than MSW with respect to porosity and water field capacity. MSW compost and separates differed by their relatively high levels of water-soluble and HCl-hydrolyzable N and increased advantageous water retention capacity. PCA also showed that substrates A-E exhibited porosity and water field capacity similar to those of Pr. Substrates F-J had porosity and water field capacity similar to those of BE/S, whereas substrates K O were more similar to Pr and to substrates A and B. The presented data indicate that DMC and MSW separates were complementary in providing good physical and chemical characteristics to the growth substrates.

Agriculture↗
PubMed2002

Chemical characteristics of Malian and Belgian solid waste composts.

Two composts, a Malian (C1) and a Belgian (C2), and a peat substrate (C3) were analyzed for their suitability for land application. The results revealed that the materials can be used in agriculture but only the composts can supply all macro-nutrients necessary for plant growth. The fractionation of Mn, Fe, Zn and Cu in operationally defined fractions (water soluble, exchangeable, complexed, organically bound and residual) allows estimation of the availability of metals for uptake. For example, 16% of the total Mn in the composts (C1 and C2) and 22% in the peat substrate would be plant available. Available Fe in the three materials was less than 2%. Available Zn varied from 10% to 25%. The fractionation also allowed estimation of the potential for contamination of groundwater following the applications of composts to agricultural lands.

Metals, Heavy↗
PubMed2003

Cultivation of oyster mushroom on waste paper with some added supplementary materials.

Spawn running, pin head and fruit body formation, and mushroom yield of oyster mushroom (Pleurotus ostreatus) on waste paper supplemented with peat, chicken manure and husk rice (90+10; 80+20 w:w) were studied. The fastest spawn running (mycelia development) (15.8 days), pin head formation (21.4 days) and fruit body formation (25.6 days), and the highest yield (350.2 gr) were realized with the substrate composed of 20% rice husk in weight. In general, increasing the ratio of rice husk within the substrate accelerated spawn running, pin head and fruit body formation, and resulted in increased mushroom yields, while more peat and chicken manure had a negative effect on growing.

Animals↗
PubMed2001

Role of ureogenesis in the mud-dwelled Singhi catfish (Heteropneustes fossilis) under condition of water shortage.

The air-breathing Singhi catfish Heteropneustes fossilis was kept inside moist peat for 1 month mimicking their normal habitat in summer and the role of ureogenesis for their survival in a water-restricted condition was studied. The ammonia excretion rate by the mud-dwelled fish increased transiently between 6 and 12 h of re-immersion in water to approximately between eight and 10-fold, followed by a sharp decrease almost to the normal level at the later part of re-immersion. The urea-N excretion by the mud-dwelled fish increased to approximately 11-fold within 0-3 h of re-immersion, followed by a gradual decrease from 9 h onwards. The rate of urea-N excretion by the mud-dwelled fish, however, remained significantly higher (approx. threefold more) than the control fish even after 36-48 h of re-immersion. Although there was a significant increase of both ammonia and urea levels in the plasma and other tissues (except ammonia in the brain), the level of accumulation of urea was higher than ammonia in the mud-dwelled fish as indicated by the decrease in the ratio of ammonia: urea level in different tissues including the plasma. The activities (units/g tissue and /mg protein) of glutamine synthetase and three enzymes of the urea cycle, carbamyl phosphate synthetase, argininosuccinate synthetase and argininosuccinate lyase increased significantly in most of the tissues (except the brain) of the mud-dwelled fish as compared to the control fish. Higher accumulation of ammonia in vivo in the mud-dwelled Singhi catfish is suggested to be one of the major factors contributing to stimulation of ureogenesis. Due to this physiological adaptive strategy of ureogenesis, possibly along with other physiological adaptation(s), this air-breathing amphibious Singhi catfish is able to survive inside the moist peat for months in a water-restricted condition.

Ammonia↗
PubMed2001

Determination of electrophoretic mobilities and hydrodynamic radii of three humic substances as a function of pH and ionic strength.

Capillary electrophoresis (CE) and fluorescence correlation spectroscopy (FCS) were employed to determine electrophoretic mobilities and hydrodynamic sizes of three humic substances (IHSS aquatic fulvic acid (FA), IHSS aquatic humic acid (HA), and IHSS peat humic acid (PHA)) as a function of pH and ionic strength. A slight aggregation corresponding to the formation of dimers and trimers was observed at low pH using fluorescence correlation spectroscopy (FCS). For example, for the peat humic acid, diffusion coefficients decreased from 2.1 x 10(-10) m2 s(-1) at pH 4 to 2.4 x 10(-10) m2 s(-1) at pH 11. For all three humic substances, electrophoretic mobilities were also shown to decrease significantly below pH 6. Calculated zeta potentials observed at high pH of -69 mV (FA), -62 mV (HA), and -63 mV (PHA) decreased to -39, -50, and -47 mV, respectively, under slightly acidic pH (4.5-4.8) conditions. No evidence of ionic strength induced aggregation was found using fluorescence correlation spectroscopy (FCS); diffusion coefficients increased slightly (<25%) with increasing ionic strength (up to 1 M). Negative electrophoretic mobilities decreased to a maximum measured ionic strength of 0.18 M. Above this ionic strength, no peaks were observed due to an increased HS adsorption to the capillary wall and an important decrease in electroosmotic flow. Interpretation of electrophoretic mobilities determined by CE is complicated by the fact that under certain conditions, HS appeared to be complexed by CE buffer systems, including MES, BES, and AMPSO.

Alkanesulfonic Acids↗
PubMed2002

Solubility-normalized combined adsorption-partitioning sorption isotherms for organic pollutants.

Equilibrium sorption isotherms were measured for five different low-polarity organic compounds (benzene, trichloroethene, 1,2- and 1,4-dichlorobenzene, and phenanthrene) over a wide concentration range. The investigated sorbents can be grouped into the following three classes: (1) humic soil organic matter, which shows linear sorption isotherms (solely partitioning, as observed in the peat sample); (2) carbon materials, which were thermally altered (due to their natural history or industrial production) and thus contain a high specific surface area and exhibit nonlinear isotherms, and (3) pure engineered microporous materials (e.g., zeolites and activated carbon), where adsorption is solely due to a pore-filling process. Sorption of all compounds was fitted very well by the Polanyi-Dubinin-Manes (PDM) model, which for sorbents containing humic organic matter (e.g., peat) was combined with linear partitioning. Both the partitioning and the Polanyi-Dubinin-Manes model predict unique sorption isotherms of similar compounds if the solubility-normalized aqueous concentration is used. In addition, an inverse linear relationship between the distribution coefficient (Kd) and water solubility, which was very well confirmed by the data, is obtained. This also leads to unit-equivalent Freundlich sorption isotherms and explains the often observed apparent correlation between sorption capacity at a given concentration (e.g., Freundlich coefficient) and sorption nonlinearity (Freundlich exponent).

Adsorption↗