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1.
Studies on selenium adsorption were conducted on seleniferous and non‐seleniferous soils of north‐west India. Soils were equilibrated with graded levels of Se ranging from 1 to 100 μg ml—1 tagged with 75Se in the presence of sulphate, nitrate and phosphate ions, generally being applied to soils as inorganic fertilizers. The adsorption of Se on different soils, both in the presence and absence of competing anions, increased with increase in the level of Se added. Adsorption of Se conformed to Langmuir equation. In the absence of any competing anions, adsorption maxima of Se for different soils ranged from 270 to 461 μg g—1. The corresponding values decreased appreciably in the presence of competing anions; per cent decrease ranged from 3 to 21 at 10 μg SO4‐S ml—1, from 8 to 40 at 60 μg NO3‐N ml—1 and 32 to 56 at 15 μg H2PO4‐P ml—1. The bonding energy of Se in different soils decreased by 33 to 66 per cent in the presence of only phosphate ions. The changes in bonding energy were inconsistent in the case of nitrate and sulphate ions. At equal concentration of added P and Se, the amount of P adsorbed was 2 to 3 times the amount of Se adsorbed. With increasing concentration of Se, greater amounts of S were released in the equilibrium solution. The distribution coefficients (Kd) decreased significantly in the presence of different anions; the effect was conspicuous in the case of phosphate ions.  相似文献   

2.
宁夏灌淤土对磷吸附的初步研究   总被引：8，自引：0，他引：8  
何文寿 《土壤学报》1992,29(2):142-149
本文报道了宁夏灌淤土12个代表性土样对磷的等温吸附与解吸特性。实测吸附曲线与Preundlich、Langmuir和Temkin三种等温吸附方程都很吻合。全部供试样品的相关系数变化在0.931-0.999之间,均达极显著水平(p<0.01)。其中Langmuir等温式与本实验资料最为吻合。供试土壤对磷的最大吸附量(Xm)变化在172-460μgP/g之间,平均为347±28μgP/g。影响其大小的因子主要是物理性粘粒和CaCO3,含量,均达极显著正相关。灌淤土不同土层的吸磷量大小依次为:剖面24>23>21>22,而解吸磷能力大小依次为:剖面23>22>21>24。磷的解吸量与吸附量之间呈极显著正相关。根据本试验数据,土壤对磷的等温吸附曲线可以用来预测土壤需磷量。  相似文献   

3.
ABSTRACT

Lucerne or alfalfa (Medicago sativa L.) is grown as a forage crop on many livestock farms. In calcareous soils in eastern Turkey, lucerne production requires phosphorus (P) additions as the soils are naturally P deficient. Phosphorus sorption isotherms were used to estimate P fertilizer needs for lucerne grown for two years in a 3-cut system on a calcareous P deficient Aridisol in eastern Anatolia, Erzurum province, Turkey. Annual P applications ranged from 0–1200 kg P ha?1. The Langmuir two-surface adsorption equation was used to derive the maximum P sorption capacity of unamended soil and to determine soil solution P, maximum buffer capacity (MBC), equilibrium buffer capacity (EBC), and P saturation at the optimum economic P rate (OEPR) for dry matter (DM) production. Soils were tested for Olson P at the onset of the study and after two years of P applications. In both years, tissue was analyzed for P content at flowering prior to first cutting. The OEPR (2-year average) was 754 kg P ha?1 yr?1 corresponding with a soil solution P concentration of 0.30 mg L?1, a DM yield of 8725 kg DM ha?1, and $528 ha?1 annual profit. The P content of leaves at flowering increased linearly with P application beyond 100 kg P ha?1 and was 3.2 g kg?1 P at the OEPR. The unfertilized soil had an EBC, MBC, P saturation, and Xmax of 3304 mL g?1, 3401 mL g?1, 6%, and 1086 mL g?1, respectively, whereas two years of fertilization to the OEPR decreased EBC and MBC to 358 mL g?1 and 540 mL g?1, and increased P saturation and Olsen P to 56% and 32 mg kg?1, respectively. These results suggest a P saturation >50% or Olsen P >30 mg kg?1 are needed to maintain an optimum soil solution concentration of 0.30 mg L?1 in this calcareous Aridisol. Similar studies with different soils and initial soil test P levels are needed to conclude if these critical soil test values can be applied across the region.  相似文献   

4.
Phosphate adsorption of some Bavarian soils . Phosphate adsorption isotherms were established in buffered (pH 4.6, 5.5, 7.0) and some in unbuffered (0.01 M CaCl2) systems for 9 soil profiles, 6 of which represent loess soils in various stages of development. In the P-equilibrium concentration range of 0–10?4 mole/l two to three ranges can be identified, each of which obeys the Langmuir equation. In the lowest concentration range (0–0.2·10?4 mole/l) adsorption is linearly related to equilibrium concentration. For the different Langmuir ranges the adsorption maxima (b) increase and the adsorption coefficients (k) decrease with increasing equilibrium concentration. The maxima depend on buffer-pH in the order 5.5<4.6<7.0. A single point method similar to the one recently proposed by Bache and Williams (1971) was succesfully applied to obtain b from a single measurement using a significant correlation between b from complete isotherms and the ratio of P adsorbed to that in solution after the addition of a fixed amount of P (0.8–1,6 mg P/g of soil). The b-values in the equilibrium concentration range of 1–20·10?4 mole/l depend mainly on soil pH (negative) and clay (positive) (multiple correlation coefficient r = 0.858). The common reason for this appears to be the amount of exchangeable Al which is also significantly correlated with b. During soil development the depth function of b changes due to decalcification, drop of pH and migration of clay and iron oxides.  相似文献   

5.
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6.
To compare the growth performance of Brassica in a phosphorus (P) stress environment and response to added P, six Brassica cultivars were grown in pots for 49 days after sowing, using a soil low in P [sodium bicarbonate (NaHCO3)–extractable P = 3.97 mg kg?1, Mehlich III–extractable P = 6.13 mg kg?1] with (+P = 60 mg P kg?1 soil) or without P addition (0P). Phosphorus‐stress markedly reduced biomass accumulation and P uptake by roots and shoots. However, root–shoot ratio remained unaffected, implying that relative partitioning of biomass into roots and shoots had little role to play in shoot dry matter (SDM) production by cultivars. Biomass correlated significantly (P < 0.01) with total P uptake. Under P stress, the cultivars that produced greater root biomass were able to accumulate more total P content (r = 0.95**), which in turn was related positively to SDM and total biomass (r > 0.89**) and negatively to P‐stress factor (r = ?0.91**). There was no correlation between P efficiency (PE) (relative shoot growth) and plant P, but PE showed a very significant correlation with shoot P content and SDM. Wide differences in growth and better performance of cultivars such as ‘Brown Raya’ and ‘Con‐1’ under P stress encouraged screening of more germplasm, especially in the field, to identify P‐tolerant cultivars.

In another study, potential relative agronomic effectiveness (RAE) of sparingly soluble P sources was investigated by growing two contrasting cultivars. The P sources incorporated into soil at 0, 10, 25, 50, and 100 mg P Kg?1 were (i) powdered Jordan rock P (RP), (ii) triple superphosphate (TSP), (iii) powdered low‐grade TSP [TSP(PLG)], (iv) a mixture of RP + TSP compacted into pellets at 50:50 P ratio [RP + TSP(PelC)], and (v) a mixture of powdered RP + TSP at 50:50 P ratio [RP + TSP(PM)]. The RP was low in RAE and only 5 and 29% as effective as TSP in producing dry matter (DM) of P‐sensitive ‘B.S.A.’ and P‐tolerant ‘Brown Raya’ cultivars, respectively. There were no significant differences between TSP and RP + TSP(PelC) in DM yield of ‘Brown Raya,’ whereas, in the case of ‘B.S.A.’ RP + TSP(PM) was significantly less effective than RP + TSP(PelC) compared with TSP. Combined utilization of superior genome and P sources [such as TSP(PLG) and RP + TSP(PelC)] produced from low‐grade RP (that cannot be used either for direct application or acidulated P fertilizers) can be used as an alternative strategy for sustainable crop production, especially in resource‐poor environments. Further field trials at the level of cropping systems are needed.  相似文献   

7.
Extensive use of chemical fertilizers in agriculture can induce high concentration of ammonium nitrogen(NH4+-N) in soil. Desorption and leaching of NH4+-N has led to pollution of natural waters. The adsorption of NH4+-N in soil plays an important role in the fate of the NH4+-N. Understanding the adsorption characteristics of NH4+-N is necessary to ascertain and predict its fate in the soil-water environment, and pedotransfer functions(PTFs) could be a convenient method for quantification of the adsorption parameters. Ammonium nitrogen adsorption capacity, isotherms, and their influencing factors were investigated for various soils in an irrigation district of the North China Plain. Fourteen agricultural soils with three types of texture(silt, silty loam, and sandy loam) were collected from topsoil to perform batch experiments. Silt and silty loam soils had higher NH4+-N adsorption capacity than sandy loam soils.Clay and silt contents significantly affected the adsorption capacity of NH4+-N in the different soils. The adsorption isotherms of NH4+-N in the 14 soils fit well using the Freundlich, Langmuir, and Temkin models. The models’ adsorption parameters were significantly related to soil properties including clay,silt, and organic carbon contents and Fe2+ and Fe3+ ion concentrations in the groundwater. The PTFs that relate soil and groundwater properties to soil NH4+-N adsorption isotherms were derived using multiple regressions where the coefficients were predicted using the Bayesian method. The PTFs of the three adsorption isotherm models were successfully verified and could be useful tools to help predict NH4+-N adsorption at a regional scale in irrigation districts.  相似文献   

8.
Abstract

Zinc adsorption by 10 (pH 4.0–6.5) cultivated mineral soils from Finland was studied in batch experiments. Additions of Zn ranged up to 600 mg kg?1 of soil and the corresponding equilibrium concentrations were 0.1–13 mg 1?1. In each soil, Zn adsorption conformed to the Freundlich isotherm. Despite a relatively low initial Zn adsorption by the acidic soils, each of the soils proved to have a high potential to adsorb Zn, but the capacity was highly pH dependent. In addition to the conventional Freundlich adsorption isotherms, calculated separately for each soil, extended Freundlich-type isotherms that also incorporate soil pH and other soil characteristics were used to describe Zn adsorption of several soils simultaneously in one equation. The pH-dependent Freundlich adsorption isotherm proved to serve as a practical tool to assess Zn adsorption by soils varying in pH and other characteristics.  相似文献   

9.
A greenhouse experiment was conducted to investigate the immediate effect of application of mono‐ammonium phosphate (MAP), single superphosphate (SSP), and triple superphosphate (TSP) fertilizers containing varying concentrations of Cd on (1) chemical speciation of Cd and Zn in soil solution by chemical‐equilibrium calculations (MINEQL+4.6 model), (2) growth of barley plants, (3) concentrations of Cd, P, and Zn in soil solution and plant tissue, as well as total plant accumulation of Cd, P, and Zn, and (4) monitoring pH and element changes during incubation periods following phosphate application. Results show that, in general, the pH of soil solution increased during the first 40 d of incubation, then declined. Also, at the end of incubation period, pH of soil solution was affected by fertilization source and fertilization rate. The concentration of Cd in soil solution changed with time. Phosphate fertilization (p < 0.05) or fertilizer source (p < 0.05) showed consistent effects. Also, the application of phosphate fertilizers with three rates significantly increased Zn concentrations in soil solution during the first half (0–30 d) of incubation period and then decreased but still more than in the control. In general, application of different sources of phosphate at 100 g kg–1 did not change the dominant forms of Cd in soil solution during all incubation time intervals. Speciation of Zn in the control after 30 d of incubation had changed, in comparison to 10 d of incubation, and the dominant forms were Zn2+, ZnOH+, ZnHCO3, ZnCO3(aq), and Zn(OH)2(aq). Adding phosphate fertilizer significantly increased both shoot and root dry weight compared to control, indicating P was a growth‐limiting factor in the control plants. The Zn concentrations in shoot and root were lower in the TSP‐ and SSP‐fertilizers treatment than those in the MAP and fertilizer treatments at all rates of fertilization. Adding phosphate increased the Cd : Zn and P : Zn ratios in the shoot and root tissue, with the effect being greater with increasing fertilization rate. Phosphate fertilization greatly increased the total accumulation of Cd of barley compared with the control plants (p < 0.001), with the effect being greater with increasing fertilization rate. Source and rate of fertilizers, and their interactions had significant effect (p < 0.05) on Cd accumulation in the whole plant.  相似文献   

10.
THE HIGH- AND LOW-ENERGY PHOSPHATE ADSORBING SURFACES IN CALCAREOUS SOILS   总被引：2，自引：0，他引：2  
The two-surface Langmuir equation was used to study P adsorption by 24 calcareous soils (pH 7.2-7.6; 0.8-24.2 per cent CaCO3) from the Sherborne soil series, which are derived from Jurassic limestone. High-energy P adsorption capacities (x″m) ranged from 140–345 μg P/g and were most closely correlated with dithionite-soluble Fe. Hydrous oxides therefore appear to provide the principal sites, even in calcareous soils, on which P is strongly adsorbed (x″m 6–51 ml/μg P). The low-energy adsorption capacities (x″m) ranged from 400–663 μg P/g and were correlated with organic matter contents and the total surface areas of CaCO3 but not with per cent CaCO3, pH, or dithionite-soluble Fe. Total surface areas of CaCO3 in the soils ranged from 4.0 to 8.5 m2/g soil. Low-energy P adsorption capacities agree reasonably with values (100 pg P/m2) for the sorption of phosphate on Jurassic limestones but phosphate was bonded much less strongly by soil carbonates (k″= 0.08–0.45 ml/μg P) than by limestones (k～10.0 ml/μg P). Low-energy P adsorption in these soils is tentatively ascribed to adsorption on sites already occupied by organic anions (and probably also by bicarbonate and silicate ions) which lessen the bonding energy of co-adsorbed P.  相似文献   

11.
ABSTRACT

The characteristics of phosphorus (P) sorption/desorption of artificially synthesized ferrihydrate and the relationship between P adsorption saturation of ferrihydrate, rice growth, and P uptake by rice (Oryza sativa L.) were studied. The results obtained from experiments showed that the artificially synthesized ferrihydrate had a very large adsorption potential to P, with 45045 μg P g?1 of maximum adsorption capacity (Qm). Phosphorus adsorption isotherm of ferrihydrate could be fitted very well with the Langmuir equation. Desorption of P adsorbed by ferrihydrate was controlled mainly by P adsorption saturation of ferrihydrate. Phosphorus adsorbed by ferrihydrate with saturation of less than 30% was hardly desorbed. Phosphorus desorption slowly increased with the increase of P saturation from 30% to 60%, but sharply increased with P saturation of greater than 60%. Thus it could be seen that P adsorption saturation should be a key factor affecting the availability of P adsorbed by iron oxides and be a better index than the quantity of oxalate-extractable P in estimating P phyto-availability in flooded soils. A Bioassay using rice indicated that 50% of P adsorption saturation could be used as a critical index for diagnosing status of P supplied by ferrihydrate-bonded P at the tillering stage of rice.  相似文献   

12.
Phosphate (P) was added to soil in solution. The soil was air-dried or freeze-dried and then incubated at a range of temperatures for periods of up to 110 d. The rate of the continuing reaction between the P and soil was measured using the null-point method, and by measuring the amount of desorption induced by filter paper impregnated with iron oxide (Pi test). The reaction between soil and P continued in both air-dried and freeze-dried soil, albeit more slowly than in moist soil. Freezing the soil, whether moist or dry, virtually stopped the reaction. These results are consistent with the hypothesis that the continuing reaction between P and soil involves a solid-state diffusive penetration of the soil particles by the sorbed P ions. They also indicate that the common practice of storing soil air-dry, even for short periods at low temperature, will not preserve the P status of the soil as at sampling. It was estimated that for a sample of soil which remained moist at 25°C for 100d after the addition of 335 μg P g−1 soil, before being sampled and stored air-dry at 4°C for 16 years, the measured Pi test value would be about 15 μg P g−1. This compares with 46 μg P g−1 which is the estimated Pi test value measured on the same day as sampling. When samples cannot be analysed for P status immediately following sampling, they should be stored at the lowest convenient temperature, preferably below 0°C.  相似文献   

13.
STUDIES ON SOIL COPPER   总被引：11，自引：0，他引：11  
Adsorption isotherms were determined for the specific adsorption of copper by soils and soil constituents. Adsorption was found to conform to the Langmuir equation. The Langmuir constants, a (adsorption maximum) and b (bonding term), were calculated. Soils were found to have specific adsorption maxima at pH 5.5 of between 340 and 5780 μg g?1, and a multiple regression analysis revealed that organic matter and free manganese oxides were the dominant constituents contributing towards specific adsorption. Adsorption maxima for soil constituents followed the order manganese oxides > organic matter > iron oxides > clay minerals, which supported the findings for whole soils. The cation exchange capacities (non-specific adsorption) of the test soils were found to be far greater than the specific adsorption maxima. However, evidence suggests that, for the relatively small amounts of copper normally present in soils, specific adsorption is the more important process in controlling the concentration of copper in the soil solution.  相似文献   

14.
Abstract

Sokoto rock phosphate (SRP) obtained from Sokoto in the Northern Nigeria was evaluated with some other phosphorus (P) sources viz: Partially acidulated rock phosphate (PARP) and single superphosphate (SSP) in the greenhouse and field studies. These fertilizers were also compared with nitrogen‐phosphorus‐potassium (NPK) 11–12–11–9.7S‐1.4Zn and NPK 10–20–5–6.5S which have 80% of their P as rock phosphate and were formulated through compaction. The fertilizers were applied in the greenhouse at 0–400 mg kg‐1soil on the Oyo Arenic Haplustalf and Alagba Kandiudult soil. Field trials were carried out at four locations—at Ikenne in the humid, Samara in the subhumid, Gumi and Gusau in the semi‐arid zones of Nigeria. The fertilizers were applied at 0–150 kg P2O5 ha‐1 in the humid zone and 0–100 kg P2O5 ha‐1in the subhumid and semi‐arid zones. Maize was used as test crop in most sites except at Samaru where sorghum was planted. The results of the greenhouse study showed that on the Haplustalf, PARP, and NPK 10–20–5–6.5S gave almost a similar relative agronomic effectiveness (RAE about 70%) as SSP, which was followed by SRP and NPK 11–12–11–9.7S‐1.4Zn (RAE between 50 and 60%). On the Kandiudult, the RAE of the fertilizers increased significantly. The PARP and NPK 10–20–5–6.55S gave high effectiveness (RAE about 90%) relative to SSP. The field trials results indicated that ground SRP was suitable for direct application on slightly acid soil in the humid zone (annual rainfall > 1,200 mm). Its efficiency was fairly moderate in the subhumid and quite low in the semi‐arid zones (annual rainfall <900 mm). The PARP gave higher RAE than SRP and had almost similar efficiency as for NPK 10–20–5–6.5S. The PARP was well comparable to SSP in the humid and subhumid zones and was fairly comparable to the later in the semi‐arid. This suggests that PARP may be suitable for humid and subhumid zones and the physical quality was also superior to SRP and SSP. Application of SRP on soils in the semi‐arid zones of low rainfall gave relatively low yields which could be due to inadequate moisture availability required to enhance P solubilization.  相似文献   

15.
The adsorption isotherms indicated that the adsorption of boron (B) increased with its increasing concentration in the equilibrium solution. The Langmuir adsorption isotherm was curvilinear and it was significant when the curves were resolved into two linear parts. The maximum value of adsorption maxima (b1) was observed to be 7.968 mg B kg?1 in Garhi baghi soil and the bonding energy (k) constant was maximum at 0.509 L mg?1 in Jodhpur ramana soil. The Langmuir isotherm best explains the adsorption phenomenon at low concentrations of the adsorbent, which of course was different for different soils. There was significant correlation between b1 and clay (r = 0.905**), organic matter contents (r = 0.734*), and cation exchange capacity (CEC; r = 0.995**) of soils. A linear relationship was observed in all the soils at all concentration ranges between 0 and 100 mg B L?1, indicating that boron adsorption data conform to the Freundlich equation. Soils that have a higher affinity for boron adsorption, like Garhi baghi, tended to desorb less amount of boron, that is, 43.54%, whereas Ballowal saunkhari desorbed 48.00%, Jodhpur ramana 48.42%, and Naura soil 58.88% of the adsorbed boron. Boron desorption by these soils is positively and significantly correlated with the sand content (r = 0.714**) and negatively with clay content (r = ?0.502*) and CEC (r = ?0.623**). The maximum value of 37.59 mg kg?1 for desorption maxima (Dm) was observed in Garhi baghi soil and also a constant related to B mobility (Kd) was found to be maximum in Garhi baghi (0.222 L kg?1) soil Note: *P<0.05; **P<0.01.  相似文献   

16.
Phosphate sorption by calcareous soils has been studied mainly on heavily fertilized agricultural soils and soils with calcite as the main carbonate mineral. We examined factors affecting phosphate adsorption in the soils of a semi-arid, mediterranean, dolomitic, soil and vegetation chrono-sequence in southeastern Spain. The youngest soils are highly eroded, Sandy Regosols (Typic Xerorthents) under gorse-scrubland vegetation. These have small P sorption capacities, large Mg-Ca carbonate contents but small amounts of Fe and Al oxides. Small total P (HNO3/HClO4 digestion) concentrations (30–130 μg P g?1), of which up to 90% is Ca-bound (HCl-extractable), are typical of these young soils. P sorption markedly increased when Ca2+ was added to the solution. The fractionation of previously sorbed P indicates that the fate of most of this extra-sorbed P is the labile-P fraction sorbed on to (carbonate) surfaces and the apatite-like fraction (NaHCO3-extractable and HCl-extractable fractions). At the other extreme, older more-intensively weathered, sandy-clay-loam rendzinas (Entic Haploxerolls), supporting dense mature garrigue, have a much greater P adsorption capacity and larger clay and Fe and Al oxide concentrations. They have more total P (ca 400 μg P g?1), much of it in occluded form (residual fraction). These soils show no significant differences in P sorption whether or not CaCl2 was used as a background electrolyte. Considering the overall variations within the chronosequence, dithionite extractable Fe and Al are the properties best correlated with P sorption. This support the general finding that crystalline Fe-oxides (e.g. goethite and haematite) appear to be the most important P-sorbing component for soils in the Mediterranean region, rather than amorphous Fe-oxides (e.g. ferrihydrite) as is reported for more mesic areas. Stepwise multiple regression and fractionation data, however, suggest that, provided the soil solution is rich in Ca2+, carbonate may also be a significant contributing factor to P sorption, especially in the youngest of these dolomitic soils.  相似文献   

17.
The geochemical reactivity of single superphosphate (SSP), triple superphosphate (TSP), phosphate rock (PR), partially acidulated phosphate rock (PAPR) and potassium dihydrogen phosphate (KH2PO4) was evaluated in an incubation trial. The soil was Anthrosols, Ap horizon (Sandy loam). Solubility equilibrium of phosphates was calculated by phosphate (PPot = logH2PO4 – pH) and calcium (CaPot = logCa + 2pH) potentials. Next, activity ratio (AR°) and Woodruff potential (ΔF) were considered for estimating phosphate dynamics in the soil. Data showed that phosphate potentials stressed on significant solubility process and varied accordingly to the rates of the fertilizers: ?5.50, ?4.81, ?4.47 and ?4.09 for 0, 50, 100 and 150 kg P ha?1. The values of the Woodruff potential (ΔF) varied widely from ?1929 to 8573 cal mol?1, i.e., from marginal supplying power in the case of the control treatment to very high supplying power for the TSP (Triple superphosphate). These findings are of practical value for the following reasons: TSP and KH2PO4 are recommended for quick and high P supply to plants; SSP and PAPR for moderate supply and finally PR for slow and low supply. Phosphorus efficiency should be treated with priority particularly for areas with intensive cropping and susceptibility to runoffs.  相似文献   

18.
Li  Shiyu  Yang  Xiuhong  Qiu  Rongliang  Wang  Peng 《Water, air, and soil pollution》2003,145(1-4):35-52
Aquatic humic substances can react with chlorine during water treatment to form trihalomethanes (THMs). Soils are important contributors to THM precursors in raw waters. An investigation into the trihalomethane formation potentials (THMFPs) of soilsin South China's Guangdong Province was conducted. The results show that the bulk THMFPs (b-THMFP) of aqueous soil extracts range from 0.7 to 36.8 μg g-1 with a median value of 10.6 μg g-1, and the THMFPs of dissolved organic matter(d-THMFP) in the 0.45 μm filtered aqueous soil extracts rangefrom 0.5 to 21.2 μg g-1 with a median value of 3.9 μg g-1 of soil. Approximately 86% of the 34 soil samples had b-THMFP values ≤20 μg g-1 and 79% had d-THMFP values ≤10 μg g-1. The finding that majority of d-THMFP/b-THMFP ratios are less than 0.5 indicates that suspendedorganic matter in aqueous extract has greater contribution to thebulk THMFP. The results of soil column study indicate that THMFPsof effluents from samples 1, 15 and 21 were higher than 100 or 50 μg L-1 at various leaching acidities. THMFPs concentrations in leachates increase with increases in the amounts of humic substances in soils. THM presursors appear to more easily flow out with soil water flow under lower acidicleaching conditions. In most cases, THMFPs concentrations in leachates showed decline with the increases of cumulative leaching volumes of feed solutions.  相似文献   

19.
Retention of vanadium (V) by three Finnish mineral soils   总被引：1，自引：0，他引：1  
Retention of V(V) by three Finnish mineral soils from 10?4m and 10?5m sodium vanadate solutions was investigated at room temperature in the pH range 2.3–7.5. In adsorption experiments, 0.02 m KCl was used as ionic medium, and the samples were left to equilibrate for 72 h. The solid: solution ration was 1:100 (m: v). Maximum adsorption occurred at pH ～4, where 70–80% of the added V (350–400 μg g?1 from 10?4m solution and 35–40 μg g?1 from 10?5m solution) was retained by each soil. Retention was significant even at pH 6, where adsorption of a similar anion, molybdate, is negligible. Desorption of the retained V was measured by adding 50.0 cm3 of 0.02 M KCl into weighed soil samples and shaking for 17 h in a mechanical stirrer. Only a minor part of retained V could be removed from each soil by the KCl treatment. Retention of different ionic species of V from 10?5m solution is approximated using values of log K obtained from the literature. In these calculations, kaolin is used as a reference material.  相似文献   

20.
Phosphate rock (PR) is an alternative fertilizer to increase the P content of P-deficient weathered soils. We evaluated the effects of fertilizer form on indicators of biological cycling of P using an on-farm trial on a Rhodic Kandiudox in western Kenya. Treatment plots were sampled after 13 cropping seasons of P applications as Minjingu phosphate rock (PR) or as triple super phosphate (?TSP) (50 kg P ha?1 season?1), as well as a P-unfertilized control (0 kg P ha?1 season?1). Soils (0–15 and 15–30 cm) were analyzed for microbial biomass P (Pmic), activities of acid phosphomonoesterase, alkaline phosphomonoesterase, and phosphodiesterase, and sequentially extractable P fractions. P additions as Minjingu PR yielded 299% greater Pmic than TSP at 0–15-cm depth despite similar labile P concentrations in the two P fertilization treatments and stimulated activities of acid phosphomonoesterase (+39%). When added in the soluble form of TSP, a greater percentage of total soil P was present in mineral-bound forms (+33% Fe- and Al-associated P). Higher soil pH under Minjingu PR (pH 5.35) versus TSP (pH 5.02) and the P-unfertilized treatment (pH 4.69) at 0–15-cm depth reflected a liming effect of Minjingu PR. The form of P fertilizer can influence biological P cycling in weathered soils, potentially improving P availability under Minjingu PR relative to TSP via enhanced microbial biomass P and enzymatic drivers of P cycling.  相似文献   

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