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Alum [KAl(SO)⋅12HO] is often added to chicken manure to limit P solubility after land application. This is generally ascribed to the formation of Al-PO complexes. However, Al-PO complex formation could be affected by the matrix of chicken manure, which varies with animal diet. Alum was added to KHPO (as a reference material) and two manures from typical chicken farms in China, one from an intensive farm (CMIF) and another from free-ranging chickens (CMFR). These were subsequently incubated with soils for 100 d to investigate P transformations. Alum reduced water-soluble colorimetrically reactive phosphorus (RP) from soils amended with manure more effectively than in soils amended with KHPO. Alum addition lowered Mehlich-3 RP in soils with CMFR but had no influence on Mehlich-3 RP in CMIF- or KHPO-amended soils. A comparison of P in digested Mehlich-3 extracts with RP in undigested samples showed significantly increased P in digests of alum-treated CMFR only. Fractionation data indicated that alum treatment increased P in the NHF-RP (Al-P) fraction only in soils with KHPO, but not in soils with manure treatments. Furthermore, NaOH-extracted nonreactive P was markedly higher in soil with alum-treated CMFR relative to normal CMFR. The CMFR manure was assumed to contain higher concentrations of organic P because these chickens were fed grains only. These results suggest that the formation of alum-organic P complexes may reduce P solubility. By comparing alum-treated KHPO and manures, it appears that organic matter in manure could interfere with the formation of Al-PO complexes., (Copyright © Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and AgriFood Canada.)

Ten sediments were collected from the northern part of Taihu Lake, China. They were incubated for 24 h and 80 days to analyze the adsorption characteristics. After adsorption, the residual sediments were extracted with 0.01 M CaCl 2 and 0.5 M NaHCO 3 separately. Maximum buffer capacities of the Langmuir and Freundlich functions of 80-day incubation were highly correlated with 24 h (R 2  = 0.97). A longer time would enhance the resistance of the sediments to P changes in the water. Adsorption and NaHCO 3 -P were highly linearly related with R 2  > 0.969, but the relationships between 24 h and 80 days were different. The relationships between adsorption and CaCl 2 -P could be better explained (97 %) by segmented line models, but the fitting results were affected by incubation time. An interesting finding is that when we plotted the NaHCO 3 -P and CaCl 2 -P together by a segmented line model, the data showed a uniform trend unrelated to the incubation time. NaHCO 3 -P is seldom used to evaluate P status in sediments in comparison with soils. Yet, our results suggested NaHCO 3 -P is a good bridge to link the sediments P retention ability and P release risk. Due to its simplicity, NaHCO 3 -P has promising potential in predicting the transfer of P from sediments.

Treating poultry litter with alum has been shown to lower ammonia (NH) emissions and phosphorus (P) runoff losses. Two long-term studies were conducted to assess the effects of alum-treated poultry litter on P availability, leaching, and runoff under pasture conditions. From 1995 to 2015, litter was applied annually in a paired watershed study comparing alum-treated and untreated litter and in a small plot study comparing 13 treatments (an unfertilized control, four rates of alum-treated litter, four rates of untreated litter, and four rates of NHNO). In the paired watershed study, total P loads in runoff were 231% higher from pasture receiving untreated litter (1.96 kg P ha) than from that receiving alum-treated litter (0.85 kg P ha). In both studies, alum-treated litter resulted in significantly higher Mehlich III P (M3-P) and lower water-extractable P at the soil surface, reflecting greater retention of applied P and lesser availability of that P to runoff or leaching. In soils fertilized with alum-treated litter, M3-P was much higher when analyzed by inductively coupled argon plasma emission spectrometry than by colorimetry, possibly due to the formation of aluminum phytate. Indeed, alum-treated poultry litter leached less P over the 20-yr study: M3-P at 10 to 50 cm was 266% greater in plots fertilized with untreated litter (331 kg M3-P ha) than with alum-treated litter (124 kg M3-P ha). This research provides compelling evidence that treating poultry litter with alum provides short-term and long-term benefits to P conservation and water quality., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

Lake sediments are subjected to intensive anthropogenic activities such as dumping of industrial waste water and leakage of P fertilisation from agricultural lands. There has a great body of research focusing on examining phosphorus fractions, which provide fundamental data that facilitate understanding the risk of P-induced eutrophication. Here, we have extracted the data of P fractions from 484 sediment samples residing in 48 lakes mainly in EU, China and USA. NH4Cl-P and total phosphorus (TP) displayed a well linear relationship, but not applicable to all lakes. Six groups were categorised as per the slope and intercept by using the clustering analysis. Specific measures were recommended to curb P release risk by considering the characteristics of each group. For instance, TP controlling is deemed as a priority in group with steep linear dependence of NH4Cl-P on TP. A significant correlation was determined between TP and NaOH-P (r2 = 0.63). Among other findings, larger lake area significantly contributes to lower all P pools. Deeper depth could only pronouncedly influence the BD-P, HCl-P. Additionally, we found lakes in Germany have pronounced higher averaged P pools than other regions. Furthermore, this paper creates awareness of the present status of lake eutrophication for researchers and policy-makers. [ABSTRACT FROM AUTHOR]

Ten sediments were collected from the northern part of Taihu Lake, China. They were incubated for 24 h and 80 days to analyze the adsorption characteristics. After adsorption, the residual sediments were extracted with 0.01 M CaCl and 0.5 M NaHCO separately. Maximum buffer capacities of the Langmuir and Freundlich functions of 80-day incubation were highly correlated with 24 h ( R = 0.97). A longer time would enhance the resistance of the sediments to P changes in the water. Adsorption and NaHCO-P were highly linearly related with R > 0.969, but the relationships between 24 h and 80 days were different. The relationships between adsorption and CaCl-P could be better explained (97 %) by segmented line models, but the fitting results were affected by incubation time. An interesting finding is that when we plotted the NaHCO-P and CaCl-P together by a segmented line model, the data showed a uniform trend unrelated to the incubation time. NaHCO-P is seldom used to evaluate P status in sediments in comparison with soils. Yet, our results suggested NaHCO-P is a good bridge to link the sediments P retention ability and P release risk. Due to its simplicity, NaHCO-P has promising potential in predicting the transfer of P from sediments. [ABSTRACT FROM AUTHOR]

The need for minimizing water eutrophication makes controlling phosphorus (P) release and/or loss from sediments/soil an urgent matter. This research seeks to develop methods to predict P release in sediments. We first studied the P adsorption in 10 sediments from a sub lake of Taihu Lake, China for 80 days. After adsorption, the sediments were extracted with 0.01 M CaCl 2 and 0.5 M pH 8.5 NaHCO 3 solutions. We found strong linear relationships between the equilibrium concentration and CaCl 2 -P (R 2 = 0.91) and between P adsorbed and NaHCO 3 -P (R 2 = 0.90). This result suggests that: (I) CaCl 2 -P can be used as a proxy for the P concentration between the sediment interface and overlying water when it is difficult to measure P; (II) NaHCO 3 -P is able to evaluate the newly adsorbed P in the sediments which may reflect the enriched process. The results indicate that we could link CaCl 2 -P and NaHCO 3 -P further using common isotherm models. This hypothesis was tested for our sediment data and soil data from published literature. Models derived from Langmuir and Temkin isotherms could successfully fit the data. In more general applications, our models are also capable of describing the relationship of NH 4 Cl-P and TP. They are routine indexes to assess the status of sediment P. The fact that the models predict P loss in soils or P release from sediment well makes them potentially useful in areas of wide P risk assessment. [ABSTRACT FROM AUTHOR]

Phosphorus (P) fractions and phosphatase activities were measured in 22 coastal wetland soils with typical vegetation successions in Yancheng National Nature Reserve, China. P forms and phosphatase activities varied greatly from site to site even under the same vegetation cover. NH 4 Cl–P, bicarbonate/dithionite extracted P and NaOH–P were remarkably higher (p < 0.05) in soils with exotic invasive plants, Spartina alterniflora , than in soils with the native species Suaeda salsa , Scirpus mariquete and Phragmites australis . HCl–P and refractory P showed little variation. No significant differences were detected for either alkaline phosphatase (ALAP) or acid phosphatase (ACAP) among the soils. All of the above properties were much higher in soils with plant growth compared to bare flat soils. Regression analysis demonstrated that organic matter (OM), Al, Ca, Fe and total P (TP) were able to explain more than 70% of the variations in the P fractions (except 29% of NH 4 Cl–P), and OM was the most important contributing factor. ALAP and ACAP were irrelevant to P but were significantly related to TOC, suggesting that carbon was a limiting factor for P mineralization in this area. Owing to its huge biomass and densities, Spartina alterniflora displayed great potential for carbon input, thus facilitating P mineralization and cycling. The results enhance our understanding of P availability differences in this area covered by invasive and native vegetation. [ABSTRACT FROM AUTHOR]

Phosphorus (P) sediment sorption is regarded as the most important buffering process against P increases in overlying water. In this study, two shallow eutrophic sediments (Mei and Hua) with distinct compositions were selected to assess effects of pH (from 6 to 9) and ionic strength (IS) (0, 0.001, 0.01 and 0.1 M KCl) on P sorption. In Mei sediments, the P sorption decreased as pH increased (6.97–9.13), but it increased as IS increased over the pH range in question. These results could be attributed to the negatively charged surface of Mei sediments, as indicated by the salt titration curve, and the high cation exchange capacity (CEC). P sorption in Hua sediments was facilitated by a pH increase (6.12–7.49), but it was hindered by an IS increase. A reasonable explanation for this phenomenon is that calcium phosphate precipitates at high pHs and that Cl−exchanges with P because the surface is weakly charged (small CEC). These results indicate that the sediment P sorption may have trends opposite to one another in relation to the salt change (e.g. drought and rainy season) in the lake water between the two sediments. These data provide additional support to explain P concentration variations in lakes. [ABSTRACT FROM AUTHOR]

Phosphate (PO 4 3− ) removal on calcite often entails two processes: adsorption and precipitation. Separating these two processes is of great importance for assessment of PO 4 3− stability after removal. Thus, this study was aimed at finding a critical range of conditions for separating these two processes in calco-carbonic equilibrium, by adjusting PO 4 3− concentration, reaction time and pH. PO 4 3− removal kinetic results showed that: (I) At pH7.7, PO 4 3− removal was mainly by adsorption at initial PO 4 3− concentration ≤2.2 mg L −1 and reaction time ≤24 h, with dominant precipitation occurring at initial PO 4 3− concentration ≥3 mg L −1 after 24 h reaction; (II) At pH8.3, adsorption was the key removal process at initial PO 4 3− concentration ≤7.5 mg L −1 and reaction time ≤24 h, whereas precipitation was observed at initial PO 4 3− concentration of 10 mg L −1 after 24 h reaction, (III) At pH 9.1 and 10.1, PO 4 3− removal mechanism was mainly by adsorption at initial PO 4 3− concentration ≤10 mg L −1 within 24 h reaction. Based on the kinetic results, it is suggested that PO 4 3− precipitation will occur after 24 h reaction when saturation index of amorphous calcium phosphate is between 1.97 and 2.19. Besides, increasing PO 4 3− concentration does not cause a continuous decline of PO 4 3− removal percentage. Moreover, experimental removal data deviated largely from the theoretical adsorption value by CD-MUSIC model. These indicate occurrence of precipitation which is in agreement with the kinetic result. Therefore our study will provide fundamental reference information for better understanding of phosphorous stabilization after removal by calcite. [ABSTRACT FROM AUTHOR]