Phosphorus Adsorption Characteristics Research Articles

Characteristics of phosphorus adsorption for a titanium mesostructure synthesized with various surfactants

Eutrophication due to excessive phosphorus in water has been considered one of the most important environmental problems. In this study, a titanium mesostructure, prepared with different surfactant templates, was tested to confirm its applicability as an adsorbent for the removal of phosphorus and to evaluate the phosphorus removal efficiency. An X‐ray diffraction analysis, the phosphorus adsorption isotherm and a kinetic test were performed on the titanium mesostructure synthesized with various molar ratios of base material to surfactant and different surfactant templates. It was revealed that the mesostructure synthesized with the molar ratio of 1.00/0.25 was the most uniformly and clearly formed and had the maximum adsorption capacity.

Adsorption characteristics of phosphorus from aqueous solutions onto phosphate mine wastes

The present study aims to investigate the key parameters and mechanisms affecting the removal of phosphorus ions from aqueous solutions onto phosphate mine slimes (PMS) in batch mode. PMS is an abundant waste generated by phosphate mine industry. The results indicate that phosphorus removal increases with increasing initial aqueous phosphorus concentrations, adsorbent dosage and temperature, and decreased with increasing pH values. The adsorption data kinetic modeling, the energy dispersive spectroscopy (EDS) and the Fourier transform infra-red spectroscopy (FTIR) analysis before and after adsorption of phosphorus onto PMS show that the main involved mechanisms are both ion exchange with chlorides and sulphur anions and complexation with some functional groups such as hydroxyl, carboxylic and acid halides groups. Furthermore, the results of the elementary composition analysis of PMS before and after adsorption indicated that the phosphorus content in PMS has increased by about 43% which promote its potential to be used as a fertilizer. In comparison with other natural adsorbents, PMS could be considered as one of the most efficient natural materials for the removal and recovery of phosphorus with the possibility of agronomic reuse as fertilizer.

Characteristics of Phosphorus Adsorption of Aerated Concrete in Wastewater Treatment

Constructed wetlands are widely used throughout the world to treat a wide variety of wastewater. Numerous researches on phosphorus removal have been reported, however, in practice, phosphorus removal efficiency through the constructed wetland is still relatively lower due to various reasons. In this paper, the phosphorus adsorption capacity of aerated concrete (a building material) was investigated by using Freundlich and Langmuir adsorption isotherm equations, and then the possibility, using aerated concrete waste residues for the treatment of effluent with relatively higher concentration phosphorus at the outfall of constructed wetland end through certain engineering measures, was explored. The results showed that aerated concrete not only had a higher phosphorus adsorption capacity (6.064mg/g), but also had a higher adsorption rate, compared with some other substrate materials commonly used for constructed wetlands. Coupled with the lightweight characteristic of aerated concrete, the imagination of the secondary purification pond was likely to be formed. If the imagination turns into a reality, it will not only effectively purify sewage emissions from the constructed wetland forever, but also realize the resource utilization of large quantities of aerated concrete waste residues resulting from the construction process.

Determining Phosphorus Adsorption Isotherm in Soil and its Relation to Soil Characteristics

Phosphorus (P) adsorption characteristics of 5 soil samples were studied in soils of Omidie, Southeastern Iran, during 2009/2010 cropping season. Some soil properties as well as selected P-adsoption characteristics were studied in these soils. In this study, results show Langmuir adsorption isotherm had better match with adsorbed P data and maximum R-square. Differences in P- adsorption were greatly influenced by soil organic carbon (SOC), soil pH, exchangeable calcium and exchangeable aluminium. Regression analysis showed that SOC and Al sat were the highest predictors of Padsorption in soils of the study site. There is need for inclusion of more soil chemical, physical and mineralogical properties in predicting soil Padsorption to enhance reliability of information.

Phosphorus adsorption characteristics of oyster shells and alum sludge and their application for nutrient control in constructed wetland system

This research aimed to evaluate the feasibility of employing some locally available oyster shells (OS) and alum sludge (AS) as the P adsorption media of constructed wetland beds. The batch and column tests were conducted with different sizes of OS and AS to observe the P adsorption characteristics and breakthrough, while P adsorption rates were determined from jar test. From the batch test, the ability to adsorb the amount of added P was different considerably between OS and AS media and sizes. At the same size, the P adsorption capacities of OS were higher than those of alum sludge. The P adsorption capacities of AS with 0.3–0.6 mm and > 0.6 mm sizes were similar, but those of 0.3–0.6 mm OS was higher than > 0.6 mm OS. Jar test results revealed the first-order P removal rates (k) to be 11.4, 4.5, 1.7 and 1.0 d− 1 for the 0.3–0.6 mm AS, > 0.6 mm AS, 0.3–0.6 mm OS, and > 0.6 mm OS, respectively. From the column tests, the adsorption capacities were found to be more than 26 and 24.5 g/kg for the OS media sizes of 0.3–0.6 and > 0.6 mm, respectively, and 12 g/kg for the AS media. The column tests revealed that AS was able to adsorb P faster than the oyster shells, but due to its low adsorption capacity, the periods of P breakthrough in the effluent of the alum sludge columns were shorter than those of the oyster shell columns. Experiments with a pilot-scale vertical-flow subsurface constructed wetland unit packed with > 0.6 mm OS media demonstrated the high P removal efficiencies of more than 96.2% during the 210 days of operation.

제지슬러지에 대한 alum 처리 및 퇴비화에 따른 인 흡착능 변화

제지슬러지(PMS)는 침전과정에서 alum을 사용함으로 인해 다량의 알루미늄을 함유하며, 그 결과 토양 시용시 종종 작물에 대한 인의 흡수를 제한하는 요인으로 작용한다. 본 연구는 그러한 제지슬러지의 인 흡착 특성을 조사하기 위하여 토양을 대조로 하여 alum을 처리하기 전과 후에 채취한 제지 슬러지 및 제지슬러지 퇴비(PMSC)를 대상으로 인 최대 흡착<TEX>$(X_m)$</TEX>과 흡착에너지 상수 <TEX>$K_f$</TEX>를 조사하였다. 토양의 인 최대흡착량은 800 <TEX>${\mu}g\;g^{-1}$</TEX>인 반면, alum 처리 전 PMS는 47 <TEX>$mg\;g^{-1}$</TEX>, alum처리 후 PMS는 61 <TEX>$mg\;g^{-1}$</TEX>으로서 대조 토양에 비해 PMS의 인 흡착량은 현저하게 높고, alum 처리 후 인흡착능은 약 30% 증가하였다. 또한 퇴비화 후 PMS 퇴비의 최대 인 흡착능은68 <TEX>$mg\;g^{-1}$</TEX>으로서 퇴비화로 인하여 약 11%의 인 흡착능이 증가하였다. 인 흡착 계수인 <TEX>$K_f$</TEX>는 alum 처리 유무 간 큰 차이가 없었으나 퇴비화후에는 크게 증가하는 것으로 나타났다. 인 최대 흡착량<TEX>$(X_m)$</TEX>과 흡착에너지 상수 <TEX>$K_f$</TEX>를 고려한 이러한 결과들은 제지슬러지의 퇴비의 장기 혹은 과량시용이 작물에 대한 인의 흡수를 제한하는 요인으로 작용할 수 있음을 암시한다. Excess application of paper mill sludge (PMS) in field can limit phosphorus uptake by crops because aluminum presented in the sludge can fix or adsorb available phosphorus which is necessary for crop growth. To investigate phosphorus (P) adsorption characteristics of PMS, we examined P adsorption maximum <TEX>$(X_m)$</TEX> using Langmuir isotherm and P adsorption energy constant <TEX>$(K_f)$</TEX> using Freundlich isotherm for PMS without alum, PMS with alum, and composted PMS with alum through a laboratory incubation test. The maximum P adsorption capacities were 800 <TEX>${\mu}g\;g^{-1}$</TEX> in soil, 47 <TEX>$mg\;g^{-1}$</TEX> in PMS without alum and 61 <TEX>$mg\;g^{-1}$</TEX> in PMS with alum. P adsorption capacity with alum treatment for PMS increased by 30%. That of PMS compost was 68 <TEX>$mg\;g^{-1}$</TEX> and showed that composting increases 11% of P adsorption. Freundlich constant <TEX>$K_f$</TEX> was 22 in check soil, while <TEX>$K_f$</TEX> values in PMS without alum and in PMS with alum were 398 and 426, respectively. After composting, <TEX>$K_f$</TEX> value of PMS compost significantly increased as 1,819. In conclusions, p adsorption capacity for PMS were increased by alum treatment or composting and therefore excess or continuous land application of alum-amended or composted PMS can limit P uptake for crops by reducing available P in sell.

Phosphorus fractions and adsorption characteristics of floodplain sediments in the lower reaches of the Hanjiang River, China

The phosphorus fractions and adsorption characteristics of seven floodplain sediment samples collected in the lower reaches of China's Hanjiang River were studied. Most phosphorus fractions showed a marked downstream increase in response to point-source inputs from urban areas. Total phosphorus (TP) contents in the sediments ranged from 603.68 to 945.25 mg x kg(-1). Inorganic phosphorus (IP) was the major component of TP, and calcium-bound phosphorus (Ca-P) was the major fraction of IP. The distribution characteristics of the phosphorus contents were affected by sediment grain size and hydrodynamic conditions. The maximum phosphorus adsorption capacities (Q (max)) and the half-saturation concentration (k) were obtained using an improved Langmuir model. Native adsorbed exchangeable phosphorus content (w (NAP)) and the zero-equilibrium phosphorus concentration value (c (EPC0)) were subsequently calculated. The effects of sediment grain size, temperature, and disturbance on the phosphorus adsorption isotherms were also studied. The results showed that phosphorus adsorption on floodplain sediments was primarily chemisorption; the particle concentration effect played a more important role at a disturbance intensity of 150 r x min(-1) (on a shaker table) than at 100 r x min(-1).

Phosphorus adsorption characteristics of selected southeastern nigerian soils

The phosphorus adsorption characteristics of selected Southeastern Nigerian soils from Ikom, Bende and Ihiagwa were evaluated. P adsorption isotherm was obtained by shaking soil samples with 0, 10, 20, 30, 40 and 50 ppm P in 0.01M CaCl2 solution. P adsorption maxima (b), affinity constant (k), buffering capacity and P sorbed at 0.2 ppm equilibrium solution were estimated. Also adsorbed P was correlated with some soil properties. The adsorption isotherm showed that the capacity to adsorb phosphorus varied in the order; Ikom> Ihiagwa> Bende. The values for the P sorbed at 0.2 ppm solution, buffering capacity, adsorption maxima and affinity constant were 43.28, 43.30, 34.48 and 12.95 ug/g respectively for Ikom, 3.86, 7.78, 29.50 and 0.21 ug/g respectively for Bende and 8.48, 10.00, 33.11 and 0.57 ug/g respectively for Ihiagwa soils. The capacities to adsorb P was significantly and positively correlated with soil clay (r = 0.94), exchangeable aluminum (r = 0.72), soil pH (r = 0.83), whereas the correlation with exchangeable calcium (r = -0.56) and organic carbon (r = -0.72) were significantly negative. The implications are that the higher the soil pH, clay level, exchangeable aluminum, adsorption maxima and affinity constants the higher the soil adsorption capacities whereas the reverse will occur the higher the soil organic carbon and calcium levels. The study shows that Ikom soil will require higher P fertilization rates than the other two soils for optimum plant growth. Also management practices involving the use of organic matter and liming as basis for P adsorption reduction would be useful for improved crop production in these soils. The use of P adsorption isotherm as a valid tool for P fertilizer management is recommended for Southeastern Nigerian soils.Agro-Science Vol. 4 (1) 2005: pp. 50-55

Phosphorus fractions and adsorption characteristics in grassland soils of varied soil phosphorus status

Characterization of phosphorus (P) in soils is important both agronomically and environmentally, although the outcome may depend on the technique applied. Consequently, we evaluated fractionation and adsorption, individually and jointly, and relevant ancillary soil attributes, to determine the dominant functional characteristics of soil P in 32 fertilized temperate grassland Inceptisols classified by eight soil series, and by two soil-P index and parent material groups. Residual P was low (30.7%) and organic P (Po) prominent, 42.0% vs. 17.5% for equivalent soils in unfertilized natural ecosystems. Labile fractions comprised 6.8% inorganic P (Pi) and 9.1% Po. The proportional increase in high vs. low index soils (Morgan P > 6.0 mg l−1 vs. ≤ 6.0 mg l−1) was higher for Pi, and highest for labile and moderately labile fractions. Only moderately labile Pi and Po differed significantly between soils of limestone and non-limestone origin. Oxalate extractable Fe (Feox) and buffering (EBC) were higher in the latter. The equilibrium P concentration (EPC) was substantially higher in the high index group, and EBC and binding energy (k) substantially lower, with no significant difference in sorption maximum (Pmax). EBC equated with weak to strong buffering in different soil series, and conformed better than k to ancillary attributes. Pmax correlated in order Alox > clay > OC > Feox, and more broadly reflected sorption attributes than oxalate-based sorption capacity (PSC). Principal component (PC) analysis showed consistent differentiation of P fractions, mostly labile and moderately labile, in PC 1 vs. adsorption and ancillary attributes in PC 2. However, scatterplots of PC scores showed that adsorption characteristics provided better functional differentiation than P fractions for distinguishing individual soil series, which may have implications in selection and interpretation of extractants not only for environmental but also for agronomic soil-tests.

Association of soil-test phosphorus with phosphorus fractions and adsorption characteristics

There is incomplete understanding, based on a single comprehensive study, of the relationship between empirical extractants of soil-test P (STP) and fundamental measurements of soil-P status such as inorganic (Pi) and organic (Po) fractions, P adsorption and relevant ancillary soil attributes. Consequently, we assessed these relationships for the extractants Morgan, Mehlich-3, Olsen, Bray-1, lactate–acetate, CaCl2 (1:2 and 1:10 soil:solution) and resin. Multiple regression analysis indicated that STP extracted with Morgan and CaCl2 related dominantly with the most labile resin Pi fraction, Mehlich-3 and Olsen with labile NaHCO3 Pi, Bray-1 with moderately labile NaOH Pi and lactate-acetate with relatively stable Ca-bound HCl Pi, for example. Especially for Morgan and CaCl2 (1:2), and except for Bray-1, the best relationship of STP with adsorption characteristics was with equilibrium P concentration in solution (EPC). Buffering capacity (EBC) and binding energy (k) did not have significant effects, as indicated by regression, whereas the effects of clay and oxalate-extractable Fe (Feox) were generally negative and Alox and organic carbon (OC) positive. Principal component analysis (PCA) highlighted many similarities in the extractants. However, regression of STP against soil-P pools, integrated as principal component scores, inadequately revealed relationships, which were better facilitated by PCA ordinations. For ordinations of STP with P fractions, eigenvalues for the first two axes explained 88.6% of the variance. Closest associations were residual Pi with HCl Pi, CaCl2 (1:10) and to a lesser extent Morgan with OC and clay, and Mehlich-3 and Olsen with NaHCO3 Pi and resin Pi. For ordinations of STP with P adsorption, eigenvalues for the first two axes explained 97.8% of the variance. The STP extractants grouped in specific, but distinctly different, combinations. For example, strongest inverse relationships were EBC to EPC and Morgan, and k to resin and Olsen, and to OC and clay, indicative of weak P bonding on these surfaces. These distinctions are consistent with, and provide a rationale for, the relevance of Morgan as an environmental P test vis-a-vis other extractants of STP.

Assessment of labile phosphorus fractions and adsorption characteristics in relation to soil properties of West African savanna soils

A large proportion of total P in the soils of the area is unavailable to plants and consequently P is the second most limiting nutrient. The labile and moderately labile phosphorus fractions and adsorption characteristics of surface and subsurface horizons of eleven soil profiles in the derived savanna (DS) and the northern Guinea savanna (NGS) of West Africa were assessed. The labile P fractions are the resin and HCO 3-extractable inorganic (Pi) and organic (Po) P. The moderately labile fractions are the NaOH-extractable portion of soil P in the Hedley sequential procedure. In the DS soils, the resin P, considered the most readily available fraction, varied from 1 to 14 mg kg −1, HCO 3-Pi ranged from 3.3 to 11, and HCO 3-PO was between 4 and 12 mg kg −1 in the surface horizon. In the NGS, the topsoil contained 1.5–3 mg kg −1 of resin P, 5–8 mg kg −1 of HCO 3-Pi, and 7.5–9.7 mg kg −1 of HCO 3-Po. Sodium hydroxide-Po was the largest of the fractions in all the soils studied. It ranged from 23 to 55 mg kg −1 in the topsoil. In general, the labile P levels were higher in soils of the DS than of the NGS and were related to the oxalate-extractable Fe (Fe ox), and Al (Al ox) as well as to soil texture. The subsoil of Kasuwan Magani (profile KS 9–21 cm) required 153 mg P kg −1 to maintain 0.2 mg P l −1 in solution (standard P requirement), and Danayamaka (profile DD 7–32 cm) required 145 mg P kg −1. These could translate to 214 and 200 kg P ha −1 if a plow layer of 10 cm is assumed. Because these are within the plow layer, more P fertilizer would be needed for crop production than in the other soils. The standard P requirement and the adsorption maxima were related to Fe ox and Al ox, dithionite-Fe (Fe d), and texture. The increase in labile P content with decreasing Fe ox and Al ox could imply that management practices capable of reducing the activities of Fe and Al in solution might improve P availability.

Phosphorus adsorption characteristics of a constructed wetland soil receiving dairy farm wastewater

Adsorption to soil has been identified as a key wastewater P removal mechanism in treatment wetlands. Batch incubation experiments were performed to measure the capacity of a constructed dairy farm wetland in Pictou County, Nova Scotia, to remove P from solution. The constructed wetland had been receiving wastewater since 1996. Non-linear regression analysis was performed using the Langmuir adsorption model to describe the P adsorption characteristics for the wetland soil under study. The Langmuir model was adequate in describing the P adsorption characteristics of the system studied. The P adsorption maxima found were approximately 925, 924, and 1600 mg P kg-1 soil, for the deep zone soil, shallow zone soil, and a background soil (not receiving wastewater), respectively. The P adsorption maxima for the deep zone and shallow zone soils were not significantly different (P &gt; 0.05) from one another, but were significantly lower (P &lt; 0.05) than the background soil. These data, together with information on wastewater inflow and P loading, were used to predict a lifespan of 8 yr for this wetland, relative to P removal. Key Words: Phosphorus, wetlands, constructed, adsorption, Langmuir, saturation

Phosphorus adsorption and desorption characteristics of constructed wetland gravels and steelworks by-products

Laboratory phosphorus (P) adsorption and desorption experiments were conducted on 9 substrata to evaluate their potential to remove P from sewage effluent. The substrata comprised 2 gravels used in constructed wetlands, Hawkesbury sandstone, and 6 steelworks by-products: granulated blast furnace slag, blast furnace slag, steel slag, fly ash, bottom ash, and coal wash. The studies involved ion-exchange experiments and calculation of Langmuir and Freundlich adsorption isotherms and column adsorption/desorption trials. The ability to adsorb P was then correlated to the physico-chemical attributes including X-ray fluorescence analyses of each substratum. High P adsorption capacities (&gt;380 mg/kg) were shown for granulated blast furnace slag, blast furnace slag, and steel slag, as well as fly ash. All steelworks by-products had adsorption capacities greater than the constructed wetland gravels and Hawkesbury sandstone. The P adsorption capacities of the substrata were significantly correlated with Ca (r2 = 0 · 9206), Mg (r2 = 0 · 8681), pH (r2 = 0 · 7009), S (r2 = 0 · 6696), and Si (r2 = 0 · 6438) when fly ash was omitted from the analyses. Further research is recommended to evaluate the sustainability of using slags for P removal (as well as other contaminants present in wastewater), using full-scale constructed wetlands. Research should include an evaluation of any likely environmental impacts using leachability and toxicity studies.

PHOSPHORUS ADSORPTION AND DESORPTION PROPERTIES OF MINNESOTA BASALT LUNAR SIMULANT AND LUNAR GLASS SIMULANT

Phosphorus (P) adsorption and desorption characteristics of Minnesota Basalt Lunar Simulant (MBLS) and Lunar Glass Simulant (LGS) were evaluated. Results of P interactions with lunar simulants indicated that mineral and glass components adsorbed between 50 and 70% of the applied P and that between 85 and 100% of the applied P was desorbed. The Extended Freundlich equation best described the adsorption data (r2 = 0.92), whereas the Raven/Hossner equation best described the desorption data (r2 = 0.97). Kinetic desorption results indicated that MBLS and LGS released most of their P within 15 h. The expanded Elovich equation fit the data best at shorter times while t/QDT equation had a better fit at longer times. These results indicate that P does not strongly adsorb to the two simulants and that any P that was adsorbed was readily desorbed in the presence of anion exchange resin. This work suggests that multiple small applications of P (10-20 mg P kg-1) should be added to the simulants to ensure adequate solution P for plant uptake and efficient use of P fertilizer.

Phosphorus supplying capacity of heavily fertilized soils I. Phosphorus adsorption characteristics and phosphorus fractionation

Studies were conducted to investigate the P sorption characteristics and P fractions in eight intensively fertilized soils collected from southern and central Norway. Adsorption of P at the initial P concentrations in the soil solution was very high in the Saerheim clay loam soil which contained high amounts of organic C and clay. Adsorption data were fitted well to the classical Langmuir equation. The P affinity constant (k), adsorption maximum (b) and maximum buffer capacity (mbc) calculated from this equation differed considerably among soils. The P affinity constant (r=0.96,p=0.01) and maximum buffer capacity (r=0.97,p=0.01) were highly and positively correlated to organic C. None of the soil parameters were related to adsorption maximum. Phosphorus desorption from the heavily fertilized soils varied widely and depended on the initial P status of the soil and soil texture. The ratio between desorbed P and total P was significantly correlated to sorption parameters. Multiple regression analysis showed that total P positively and organic C negatively affected P desorption in the soils. Iron-P was a major P sink in these soils and it was related to clay content (r=0.69,p=0.1) and organic P (r=0.76,p=0.0.5), but it did not relate to average P removed per harvest (RPH). Calcium-P and Al-P were not related to any of the soil parameters but these fractions were the major contributors to RPH as expressed by a multiple regression equation: RPH=0.397+0.0016 × Ca-P + 0.0012 × Al-P (r=0.84,p=0.05). High content of inorganic fractions shows that most of the residual P may be plant available, albeit at reduced rate with time, in these soils but the availability will depend on soil types.

Phosphorus‐sorption characteristics of intensely weathered soils in south‐central kentucky

Abstract Studies were conducted to investigate phosphorus (P)‐sorption characteristics of some intensely weathered soils in south‐central Kentucky. Phosphorus adsorption characteristics reflected the chemical and mineralogical properties of the soils studied. All adsorption data were adequately described by first order kinetic reactions which implied that the soils have uniform surfaces for P sorption. In spite of the limitations of the Langmuir equation, its usefulness in summarizing data into one adsorption maximum value was demonstrated by nearly identical adsorption maxima estimated by three linear transformations of the equation and small deviations from the observed maxima. Variations in adsorption maxima between surface and subsoils and among soils were best correlated with extractable aluminum (Al) (r = 0.93, p<0.01) and crystalline iron (Fe) oxy‐hydroxides (r = 0.97, p<0.01). Clay content was also highly correlated with P sorption (r = 0.97, p <0.01) as well as with extractable Al (r = 0.83, p<0....

Adsorption and desorption of phosphate in some semi-arid tropical Indian Vertisols

Adsorption and desorption of phosphorus in soils are among the key processes governing its availability to crops. There have been very few studies on the phosphorus adsorption and desorption characteristics of Vertisols. The P adsorption and desorption characteristics of four Vertisols belonging to three agriculturally important soil series were studied. The amounts of P adsorbed by the soils at 0.2µg ml−1 equilibrium solution P concentration was low and ranged from 34.3 to 79.5µg g−1 soil. The phosphate adsorption was very well described by Langmuir and Freundlich isotherms. The P adsorbed by a Vertisol (BR-1) fertilized with different rates of P in the previous season (0, 10, 20 and 40 kg P ha−1) was similar (34.3–41.3µg g−1 soil) indicating little effect of fertilization on P adsorption. The correlation studies indicated that the DTPA-extractable Fe was the most important factor accounting for P adsorption in these soils. Clay and CaCO3 content were found to be relatively less important factors affecting P adsorption in the soils studied.The capacity of the two extractants and EUF (electro-ultrafiltration) to desorb the adsorbed P followed the order: EUF (400V, 80°C)>sodium bicarbonate>EUF (200V, 20°C)>calcium chloride. The average amounts of P desorbed from the four Vertisols using these methods were 74, 63, 50, and 3% respectively of the adsorbed P. In the Begamganj soil, the amount of P desorbed by EUF (400V, 80°C) exceeded 100%, indicating that all of the adsorbed P was desorbable including some native P.In conclusion the results of our study show that the Vertisols studied have low phosphate adsorption capacity and that the P they adsorbed is easily desorbable.

Phosphorus Adsorption by Soils from Heathlands in Southern England in Relation to Successional Change

SUMMARY (1) The area of Calluna heathland in Britain and Europe has been markedly reduced, and changing patterns of land use have resulted in considerable changes in vegetation on many remaining heathland areas. (2) Determinations of the phosphorus adsorption characteristics of a range of heathland soils are described and related to differences in phosphorus economy as a result of heather burning, and the consequent release of phosphorus from organic matter components of the system. (3) Differences in the phosphorus adsorption capacity between sites are discussed in relation to changes in vegetation that have taken place in the absence of grazing or other management. (4) The implications of the differences in phosphorus adsorption capacity between sites are discussed in relation to requirements for the future management and conservation of heathlands in lowland Britain.

Phosphorus adsorption by forest soils

Abstract In 54 Greek forest soils phosphorus adsorption characteristics and their relation to certain soil properties were studied. Values of Langmuir maximum ranged from 261 to 973 μg P/g soil (mean 494) and were significantly correlated to % clay and % organic matter content. Between 24 and 75% of the adsorbed P could subsequently be extracted with Olsen P extractant (0.5M NaHCO3) and was significantly (negatively) correlated to % clay and free iron oxides content. No significant relationship was found between P retention capacities of these soils and either nature of soil parent material or FAO‐Unesco soil units.

Phosphorus adsorption characteristics of Hawaiian soils and their relationships to equilibrium phosphorus concentrations required for maximum growth of Millet

Phosphorus adsor tion isotherms were constructed for six Latosols and one calcareous soil from Hawaii which differed greatly in their phosphorus adsorption capacities. Equilibration was in 0.01M CaCl2 at 25°C for 6 or 8 days. P adsorption properties of the soils were characterised employing the linear form of Langmuir's equation and also by calculating the amount of P adsorbed between equilibrium concentrations of 0.25 to 0.35 ppm (estimates of P buffering capacities), following the procedure of Oaanne and Shaw13. The isotherms of all the soils were found to fit the Langmuir equation at low equilibrium concentrations (< 5 ppm) and the P adsorption maxima ranged from 520 to 10 500 ppm. The buffering capacity estimates correlated closely (r = 0.950) with the adsorption maxima of soils. However, in two soils, the estimates were much lower than expected from their adsorption maxima.