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• In-situ formation of MgFe 2 O 4 enhancing the dehydration and decarboxylation of SM. • Stabilization of HMs was obviously increased after MgFe 2 O 4 modified HTC. • P retention rate reached 88% due to the decrease of soluble and exchangeable P. • MFHCs exhibited high Pb(II) and Cu(II) adsorption capacity without any HMs leaching. Hydrothermal carbonization is an efficient technique for the disposal of livestock manure, enabling its harmless treatment, quantity reduction, and resourceful utilization. Co-hydrothermal of modified materials facilitates the production of more valuable carbonaceous materials. However, further exploration is needed to understand their potential impact on the environmental risks associated with livestock manure disposal and the application of products derived from it. Therefore, the carbonization degree, heavy metals stabilization, and phosphorus retention during the hydrothermal treatment of swine manure were systematically investigated in this study under the influence of in-situ formed MgFe 2 O 4. The results revealed that the in-situ formation of MgFe 2 O 4 improved the dehydration and decarboxylation of organic components in swine manure, thereby improving its carbonization degree. Furthermore, both hydrothermal carbonization and MgFe 2 O 4 modified hydrothermal carbonization resulted in an enhanced stabilization of heavy metals, leading to a significant reduction in their soluble/exchangeable fraction and reducible fraction. Phosphorus was predominantly retained in the hydrochars, with the highest retention rate reaching 88%, attributed to the significant decrease in soluble and exchangeable phosphorus fractions facilitated by the in-situ formation of MgFe 2 O 4. Moreover, MgFe 2 O 4 modified hydrochars exhibited remarkable adsorption capacity for Pb(II) and Cu(II) without any leaching of heavy metals. Overall, the findings indicated that the in-situ formation of MgFe 2 O 4 positively influenced the hydrothermal of swine manure, improving certain economic benefits in its practical application. [ABSTRACT FROM AUTHOR]

A 90-day feeding trial was conducted to investigate the effects of phytase supplemented Distiller's Dried Grains with Soluble (DDGS) based diet on the production performance, tissue composition, nutrient digestibility and activity of anti-oxidant enzymes in the gills of mrigal (Cirrhinus mrigala) juveniles. Six experimental diets were formulated to contain increasing levels of supplemental phytase, 0 (D1), 250 (D2), 500 (D3), 750 (D4), 1000 (D5), and 1250 (D6) phytase (FTU/kg). Each experimental diet was randomly assigned and fed three times daily to triplicate groups of 180 fish. Significant increase in body weight gain and specific growth rate, feed conversion and protein efficiency ratios of groups fed up to 750 FTU/kg were observed. Broken line analysis of Specific Growth Rate showed that the optimal dietary phytase level of mrigal juveniles is 750 FTU /kg or higher than this dose. Results among protein, lipid, moisture, ash and P contents of whole body, muscle, liver and viscera were not significantly different as phytase level increased from 250 FTU/kg to 1250 FTU/kg (D2 to D6). It was concluded that phytase at the rate of 750 FTU /kg is the optimum dose for the enhanced growth in juvenile mrigal. [ABSTRACT FROM AUTHOR]

Volcanic soils are well-known to have a high agronomical value, and in Sumatra, Mt. Kerinci volcanic soils produce one of the highest quality tea and rice. Declining soil organic carbon (C) and high phosphorus (P) retention are two main issues in volcanic soils in the area. Thus, this study aimed to study the dynamic of C) and P content in volcanic soils and to find the main controls of their variation from geochemical signatures. The soils of Mt Kerinci present a unique environment as one part of the area was converted from forest to tea plantation for about 100 years, and a nearby field had been used for paddy rice cultivation for about 200 years. The study was conducted in the Mt Kerinci area covering 5,922 ha in the north comprise of paddy soils (ps) and north tea soils (nts) and the south slope (south tea soils= sts). Soil samples were collected on a grid of 500 × 500 m under tea and paddy (n = 206 samples) at 0–20 and 20–40 cm depth. All soils have similar pH in H2O, but pH in KCl paddy soils (ps) > north tea soils (nts) > south tea soils (sts). The average content of soil organic Carbon (SOC) in paddy soils was 50% less than in the soils of tea plantations. The labile organic carbon content in paddy soils were lower than in soils of tea plantations. Most C was chemically bound to the metal complex. Higher P retention occurred in all soils. The CaO/TiO2 index indicated a weathering sequence of ps > nts > sts. Soil weathering controlled P retention with an increasing P retention as the soils weathered. Overall, the study suggests that cultivation in volcanic soils influenced the geochemical properties of the soils and subsequently their C and P contents. [ABSTRACT FROM AUTHOR]

Phosphorus is a crucial nutrient in terrestrial ecosystems, influencing primary productivity and ecosystem health. However, its retention and cycling vary significantly between eutrophic and dystrophic systems. This paper examines the role of natural composition-specifically soil properties, vegetation types, and microbial communities-in phosphorus retention within these contrasting ecosystems. Eutrophic ecosystems, characterized by high nutrient levels, often experience phosphorus accumulation and potential eutrophication, while dystrophic ecosystems, with low nutrient availability, exhibit limited phosphorus retention and often struggle with nutrient deficiencies. Understanding the natural mechanisms governing phosphorus retention can inform management practices aimed at maintaining ecosystem health and preventing nutrient-related issues. Key factors influencing phosphorus retention include soil texture, organic matter content, pH levels, and the diversity and function of soil microbiota. The study synthesizes current research on these factors and proposes management strategies tailored to the specific needs of eutrophic and dystrophic ecosystems. [ABSTRACT FROM AUTHOR]

Simple Summary: Phosphorus (P) is an essential mineral in the diets of pigs. The degree to which P is utilized has both economic and environmental consequences to the swine industry. Mathematical models can be used to describe the relationship between P intake and P retention. These models provide information regarding P utilization that can be used to formulate diets aimed at reducing P overfeeding, and therefore decrease P wastage. The objective of this study was to assess the ability of four non-linear models (monomolecular, Michaelis-Menten, Richards, and Morgan) and one simple linear model to describe the relationship between P intake and P retention in growing and finishing pigs. Through fitting these models to data from P balance studies, non-linear models which describe diminishing returns type behaviour, the monomolecular and the Michaelis-Menten models, were found to best describe the relationship between P intake and P retention in these categories of pig. The parameter of these models allows estimates of endogenous P losses, P requirement for maintenance and theoretical maximum P retention enabling the more efficient use of P in the swine industry. The ability of four non-linear mixed models and one linear mixed model to describe phosphorus (P) retention as a function of dietary P intake, expressed on an available P (avP) basis, was assessed in growing and finishing pigs. Of the four non-linear models, the monomolecular and Michaelis-Menten describe diminishing returns behaviour, while the Richards and Morgan describe sigmoidal behaviour with the ability to also describe diminishing returns. Using a meta-analysis approach, models were fitted to avP intake vs. P retention data from P balance studies. Pig bodyweights (BW) ranged from 43.5 to 133 kg, P intake ranged from 0.055 to 0.468 g kg−1 BW0.75 d−1 for avP, and 0.151 to 0.806 g kg−1 BW0.75 d−1 for total P, with P retention ranging from 0.026 to 0.329 g kg−1 BW0.75 d−1. Models were evaluated using statistical measures of goodness-of-fit and inspection of residuals. The monomolecular and Michaelis-Menten best described the relationship between P retention and P intake. Endogenous P losses and P requirement for maintenance were found to be higher in finishing pigs compared to growing pigs as BW increased. [ABSTRACT FROM AUTHOR]

Iron (Fe) cycling exerts strong control on the mobility and bioavailability of the key nutrient phosphate (PO 4) in soils and sediments. Coprecipitation of PO 4 is known to alter the structure of Fe (oxyhydr)oxides (FeOx), however the environmental fate of PO 4 -bearing FeOx is not well-understood. Here, PO 4 -bearing FeOx with 9 mol% coprecipitated PO 4 were prepared by Fe(III) hydrolysis and Fe(II) oxidation in the presence of dissolved PO 4 , in addition to pure FeOx synthesized in PO 4 -free solutions. The pure and PO 4 -bearing FeOx were subsequently exposed to different concentrations of dissolved Fe(II) and sulfide (2 and 10 mmol L−1). Mineral transformations and the fate of PO 4 were tracked over 7–14 days with wet chemical techniques (including sequential Fe and S extraction) and synchrotron-based Fe K-edge X-ray absorption spectroscopy. Coprecipitation of PO 4 affected the rate and extent of FeOx transformation differently for Fe(II) and sulfide. Poorly-ordered PO 4 -bearing FeOx was preserved in the presence of dissolved Fe(II) while pure ferrihydrite was nearly completely transformed into goethite over 7 days. By contrast, coprecipitation of PO 4 rendered FeOx more reactive towards sulfide compared to pure FeOx. Reaction with dissolved sulfide resulted in the formation of non-sulfidized Fe(II) or Fe(II) sulfide under high and low Fe/sulfide ratio, respectively. Under low Fe/sulfide ratio, Fh and PO 4 -bearing, poorly-ordered FeOx were nearly completely sulfidized after 14 days. Sulfidation of FeOx led to efficient release of PO 4 into solution, and at low Fe/sulfide ratio more PO 4 was released than expected based on the extent of Fe sulfidation. The results suggest feedback mechanisms of environmental relevance: coprecipitation of strongly-sorbing species such as PO 4 disrupts FeOx structure, which affects FeOx reactivity and the overall nutrient or contaminant retention capacity of soils or sediments differently depending on the ambient redox conditions. Specifically, the switch from reducing to sulfidic conditions may be associated with the disproportionate release of nutrients and contaminants. [ABSTRACT FROM AUTHOR]

This special issue of Ecological Engineering provides an overview of research within the Everglades Stormwater Treatment Areas (STAs) over the past decade to understand the ecology and the biogeochemical processes that affect phosphorus (P) retention in these constructed wetlands. This research was established within the South Florida Water Management District's Restoration Strategies Science Plan (RSSP). The RSSP was developed in 2012, updated in 2018, and produced a total of 21 studies. The goal of RSSP research is improve understanding of the factors contributing to P retention, to support management of the STAs to attain and sustain a stringent outflow total P concentration goal (i.e., the Water Quality Based Effluent Limit or WQBEL) and to maintain the wetland plant communities used to achieve this goal. Compliance with the WQBEL will reduce P loads to the Everglades to support restore and maintain this special ecosystem. This synthesis paper presents an overview of the STAs and their purpose and then summarizes the findings from the publications included in this special issue as well as previous STA related research. From this synthesis, a list of potential management options to enhance P retention in the STAs is presented. • Stormwater Treatment Areas (STAs) built to reduce P in runoff entering the Everglades. • STA discharge must meet strict low P concentration limits. • P biogeochemistry research conducted to support management of the STAs. • P removed by particle settling, biogeochemical processes and plant uptake. • Fauna excretion, bioturbation, and internal loads substantially affect P retention. [ABSTRACT FROM AUTHOR]

Context: Reducing the environmental impact of animal production is becoming a really hot topic, especially with raised concerns over excessive flows of nitrogen and phosphorus (P) to the environment. Aims: The present study was conducted to determine the effects of phytase supplementation on growth, plasma biochemistry, bone mineralisation and P utilisation of pre-lay pullets fed varying levels of non-phytate P. Methods: A total of 240 Lohmann pullet chicks were randomly allocated to one of six dietary treatments with eight replicate cages (5 birds per cage) per treatment. Six treatments included three phytase-free diets and three diets supplemented with 1000 U/kg phytase; the non-phytate P levels were 2.75-2.50-2.25, 3.75-3.50-3.25 and 4.75-4.50-4.25 g/kg in the former, and 1.75-1.50-1.25, 2.75-2.50-2.25 and 3.75-3.50-3.25 g/kg in the latter, for the age of 0-4, 4-8 and 8-16 weeks respectively. Key results: No significant differences were found for growth performance, plasma biochemistry (calcium, P, alkaline phosphatase and albumin) and bone mineralisation among dietary treatments, but P retention (%) was different (P < 0.001). Analysis of planned contrasts showed that phytase supplementation increased phytate P retention (P < 0.001), and improving the utilisation of phytate P tended most efficiently under low P conditions. Total P retention rate was reduced slightly by phytase supplementation (P < 0.05). Conclusions: The results indicated that dietary non-phytate P level could possibly be reduced to 1.75, 1.50 and 1.25 g/kg for 0-4, 4-8 and 8-16 weeks of age respectively after phytase supplementation, without compromising pullet growth and performance during the pre-laying period. Implications: The results of this study will contribute to decreasing P excretion by poultry and reducing the potential environmental impact with land application of manure. [ABSTRACT FROM AUTHOR]

Drainage ditches are effective agricultural facilities because they can drain excess water from the field, and an eco-friendly drainage ditch can also eliminate agricultural nonpoint source pollution effectively. Field work has been conducted in four types of drainage ditches with different revetment techniques, i.e., a two-stage ditch with a woodpile bank, a single trapezoidal ditch with a geotextile bag, a hollow hexagonal brick, and a reinforced vegetative bank revetment. The corresponding retention capacity of phosphorus in these ditches has been investigated. Results show that two-stage ditches can retain dissolved phosphorus (DP) more effectively compared to the other three single trapezoidal drainage ditches, and the retention efficiency is as high as 60%. The concentration of total suspended sediment (TSS) is positively correlated with that of total phosphorus (TP), and the retention capacity of drainage ditches on phosphorus will decrease as discharge increases. Current work proves that a well-designed two-stage section ditch can effectively eliminate the nonpoint source pollution during practical agriculture drainage application. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) are one of the main countermeasures to reduce diffuse phosphorus (P) losses, but there is still a lack of systematic guidance accounting for spatially variable effects of hydraulic and P load on P retention. We present a three-step modelling approach for determining suitable placement of CWs in four different size groups (0.1–1.0 ha), based on incoming hydraulic and P load. The modelled hypothetical CW area was only 17% of that previously estimated and area of efficient CWs is even lower. The mean area-specific P retention increased with CW size. However, the spatial variation in retention was large for all size groups and largest (6–155 kg ha−1 year−1) for the smallest CWs due to highly variable incoming P loads, showing the possible benefits of targeted placement of CWs. The presented modelling approach has also flexibility to include and account for possible future changes in land cover and management. [ABSTRACT FROM AUTHOR]

Taurine is a component that tends to be deficient in fish diets that contain higher plant‐derivative proteins. Acanthopagrus schlegelii juveniles (IBW − 11.28 g) were fed nine diets containing SPC levels (SPC40, SPC60, SPC80 and SPC100), or supplemented with 5 g/kg of taurine at each replacement level. Our results showed higher WGR and SGR in SPC60 + TAU (WGR; 224.67, SGR; 2.10) followed by SPC40 + TAU (WGR; 221.75, SGR; 2.09). Phosphorus retention efficiency was significantly raised as the SPC increased when compared with the control diet. Taurine addition showed an incline in the nitrogen retention efficiency. An effect was observed within FR between fish and the SPC content. ADCs of dry matter, crude lipid and phosphorous were affected by SPC, while taurine addition affected only crude lipid. A significant effect was seen in ash and phosphorus by the SPC and taurine. TAU supplementation showed an increased T‐AOC activity in the SPC80 + TAU (1.90), while malondialdehyde and catalase activity were reduced except in completely replaced fish meal groups. It could be concluded that black sea bream can accept the substitution of FM with 60% of SPC while at the inclusion of dietary TAU (5 g/kg) growth could be improved. [ABSTRACT FROM AUTHOR]

Surface runoff from agricultural fields is the largest non-point source of phosphorus (P) that pollutes surface water in humid temperate regions. Best management practices have attempted to reduce P loading and improve P retention in agricultural soils, but significant losses continue to occur, emphasizing the need for novel solutions. The objective of this study was to determine whether wood-based biochars applied to an agricultural field, 3 years earlier, could reduce P loss in surface runoff by increasing water infiltration or by improving soil stability. Field plots amended with Dynamotive, Basques and Pyrovac biochars (5 and 10 t ha−1) or without biochar were subjected to 30-min of simulated rainfall to determine runoff volume, time-until-ponding, infiltration rate, and water holding capacity, as well as the P concentration and P load in runoff. The distribution of soil macro- and micro-aggregates and their total organic C and total P content was measured. Soil water dynamics were not affected by biochar amendments, however, runoff contained significantly less ortho-P in field soil amended with Dynamotive and Basques biochar at 5 t ha−1 and significantly less particulate P when amended with biochar at 10 t ha−1. Biochar-amended soil had significantly greater microaggregate stability, organic C and total P content than the control soil without biochar. The reduction in particulate P concentration in runoff may be the result of biochar integration within the microaggregate structure, which indirectly promotes P retention in macroaggregates. • Biochar amendment reduces the P loss in surface runoff from field soil. • Soils amended with biochar had greater microaggregate stability. • Macroaggregates from biochar-amended soils contained higher total P content. • Biochar may increase P integration into the soil microaggregate structure. [ABSTRACT FROM AUTHOR]

H 2 SO 4 -modified biochar has been recognized as a means to achieve the advantages of carbon sequestration, and nitrogen loss reduction. However, little information is available on its effect on phosphorus (P) uptake, soil available P, and P leaching under alternate wetting and drying irrigation (I AWD). A split-plot experimental layout was carried out with two irrigation regimes (conventional continuous flooding, I CF , and alternate wetting and drying, I AWD) as main plots and three biochar additions (biochar-free control, B 0 , non-acidified biochar, B 20 , and acid-modified biochar, B 20A) as subplots. Results indicated that I AWD decreased water percolation by 9.26%–14.74% and P leaching by 50.14%–106.64% and increased surface soil available P by 10.88–29.08%, resulting in 14.21–35.03% apparent phosphorus balance (APB) over the three years as compared with I CF. B 20 produced a 6.23% lower grain yield in the 1st year and 5.06% and 11.02% higher yields in the 2nd and 3rd years, while B 20A increased or tended to increase it throughout the three years. Both B 20 and B 20A significantly decreased total water percolation (9.68–28.37%), P leaching (18.26–152.00%), and increased soil available P (9.90–46.24%), dissolved P in surface soil (10.00–62.50%), and P uptake (4.31–49.71%), and thereafter enhanced apparent phosphorus balance (11.06–40.78%). Compared with B 20 , B 20A achieved a better APB due to a 113% lower P leaching and 52.9% lower dissolved P at 60 cm soil profiles. I AWD B 20A-M produced the highest APB, surface soil available and dissolved P, and the lowest P leaching, which increased grain yield, APB, surface soil available P, and dissolved P by 9.54%, 129.61%, and 53.19%, and decreased P leaching by 257% over I CF B 0 , respectively. Therefore, the use of H 2 SO 4 -modified biochar could produce higher grain yield with lower P leaching and higher APB for I AWD paddy systems, which is beneficial to enhancing plant P uptake, mitigating P leaching, and ensuring sustainable agricultural production. [Display omitted] • Alternate wetting and drying irrigation (I AWD) reduce water use and P leaching. • One-year field-aged biochar reduced P leaching, improve P retention and plant uptake. • Acid-modified biochar (B 20A) enhanced soil available P and rice grain yield. • I AWD B 20A give positive apparent P balance and prevent soil P depletion. [ABSTRACT FROM AUTHOR]

To determine whether buckwheat phytase can be used as an alternative phytase source, growth performance, bone quality and P retention were measured in broilers given non-phytate P-deficient diets. Non-germinated (BU) and germinated (GBU) buckwheat were used: they were ground and sieved to remove hulls before use. A total of 120 male broiler chicks (8 d of age) were divided into 8 groups (15 birds each) and given one of the following 8 diets until 42 d of age: positive control (PC) diet satisfying recommended level of all nutrients, negative control (NC) diet formulated to contain 0.16% lower non-phytate P than PC diet, and six other diets, formulated by replacing maize in NC diet with BU or GBU at 10%, 15% and 20% concentrations. Starter diets contained 23.5% crude protein (CP) and 3,200 kcal of ME/kg, and were used for 8-21 d of age. Then, grower diets with 20.5% CP and 3,250 kcal of ME/kg, and were provided for 22-42 d of age. Compared with the PC group, NC group showed impaired growth performance (BW gain, FI, and FCR), and bone quality (dry weight, breaking strength and contents of ash and P in tibia). However, in most cases, these impairments were ameliorated dose-dependently by the addition of BU and GBU in diets, and the restoration magnitude was greater in GBU than in BU treatment. Total P excretion decreased in NC group and further decreased dose-dependently with increasing levels of BU and GBU. Except for the values in PC group, total P retention increased as the total P excretion decreased. In conclusion, dietary BU and GBU restored the growth performance and bone quality impaired by the P deficiency, and improved P retention in broilers, which suggested that buckwheat, especially when germinated, can be used as an alternative phytase source in broiler diets. [ABSTRACT FROM AUTHOR]

Numerous studies have been conducted worldwide and more specifically in Brazil assessing the consequences of biochar amendments on the soil properties and on the agronomical production. The present study aimed to evaluate the effects of biochar of coffee residues on the physicochemical characteristics of an Entisol and water use efficiency of maize ( Zea mays ). Two types of biochar were produced with both coffee ground (CG) and coffee husk (CH) and their physicochemical properties were characterized. A greenhouse pot experiment, quantifying the growth of maize, with different rates of biochar amendments and fertilizing procedures was conducted in a completely randomized design. Treatments consisted in four replications of (i) control (native soil), (ii) synthetic fertilization and (iii) organic fertilization with cow manure, and (iv) the two types of biochar in four doses (4, 8, 12 and 16 Mg ha − 1 ). Specific surface area (SSA) of CH was significantly higher than CG biochar but both types of biochar had higher SSA than soil. Nutrient and water retention properties of soil and maize growth were significantly improved with increasing biochar doses. The water use efficiency was 50% higher for the treatment with the highest dose of biochar. This is a significant found considering the potential of growing maize on a sandy soil in a dry regions of Brazil. Nutrient use efficiency as well as the C content in Entisol were largely improved by the use of biochar. Determination of SSA was a quick and robust method to anticipate the benefits of biochar on water retention of soil. [ABSTRACT FROM AUTHOR]

Fishponds exhibit high natural retention potential for phosphorus, which enters the ponds from non-point, diffuse and point sources, as well as from aquaculture management. Results of phosphorus mass balance monitoring of nine large fishponds (60-449 ha) over 2010-2014 revealed total phosphorus retention ranging between −66 % (sink) and +52 % (release) of the P loads from inflows, i.e. specific P retention varied between −7.83 g m (sink) and 1.00 g m (release) of surface area, per one fish production cycle. Retention of P was eliminated by application of fertilizers (with simultaneous fish feed application) during fish production process and/or by massive P release from fishpond sediments after previous heavy loads. P retention could be increased by preference of surface water outflow instead of bottom discharge and/or also by minimizing of emissions of suspended sediment particles during a fish harvesting. The real role of fishponds in transport processes of P throughout a watershed could be eruditely assessed only by following newly proposed method called 'new approach' when P input (via inflows) and P output (via outflows) are compared with natural fishpond ability to retain P, which is determined by a simple model proposed by Hejzlar et al. (2006). For evaluation of effect of actual fishery management, the 'culture-balance' method is suitable too. If the P inputs (stocked fish, fertilizing, feeding) and outputs (harvested fish) derived from fishery practice were in balance, the P retention did not decline. However, in condition of inputs > outputs, the P retention appreciably ceased or was totally eliminated. It was concluded that fishponds could serve as an important sink of P transported throughout a watershed even under semi-intensive fish (common carp) production condition. [ABSTRACT FROM AUTHOR]

Ascertaining the phosphorus (P) release processes in polymictic lakes is one of the methodologically most complex questions in limnology. In the current study, we combined short- and long-term investigations to elucidate the role of sediments in the P budget in a chain of eutrophic lake basins. We quantified the internal loading of P in three basins of Lake Peipsi (Estonia/Russia) for two periods characterized by different external P loadings using radiometrically dated sediment cores (long-term studies). The relationships between different water quality variables and the internal P loading, and the external P loading were studied. Our short-term studies aimed at elucidating the possible mechanisms behind variations in internal P loading included examination of the surficial sediments, i . e ., seasonal measurements of redox potential, sediment pore water P concentrations and diffusive fluxes. Our results provided evidence for a potentially high importance of internal P loading in regulating water quality. The sediment core analyses revealed an increase in the internal P loading during the period of lower external P loading coinciding with the general deterioration in the lake water quality ( i . e , higher concentrations of soluble reactive phosphorus, total phosphorus and biomass of cyanobacteria). Increase in wave action between the two studied periods appeared to cause more frequent sediment resuspension, and thus be the most likely reason for the variations in internal P loading. Our short-term measurements indicated that resuspension events can be followed by a considerable increase in the diffusive fluxes. [ABSTRACT FROM AUTHOR]

An artificial increase of phosphorus (P) retention in lakes with a long residence time and/or a large mobile sediment P pool by adding P binding chemicals can drastically shorten the time these lakes require to reach water quality targets. Suitable tools to optimize timing and extent of external and internal measures are lacking. The one-box model, a mass balance tool for predicting the P trend in the water under different management options was applied to highly eutrophic Lake Arendsee (a = 5.14 km 2 , z max = 49 m), Germany. Mass developments of blue green algae and increasing hypolimnetic oxygen deficiencies are urgent reasons for restoring Lake Arendsee. Detailed studies of P cycling and scenario analyses with the one-box model led to the following conclusions: i) immediate improvement of the trophic state is only possible by in-lake P inactivation because of the long water residence time (56 years); ii) a gradual external P load reduction, even if the effect is delayed, will assure the sustainability of the scheduled Al application beyond one decade; iii) a twofold precipitation reduces the risk of failure compared to a singular application with an overdose related to the relevant internal P pools. [ABSTRACT FROM AUTHOR]

Phosphorus (P) sorption processes in soils contribute to important problems in agriculture: a deficiency of this plant nutrient and eutrophication in aquatic systems. Soil organic matter (SOM) plays a major role in sorption processes, but its influence on P sorption remains unclear and needs to be elucidated to improve the ability to effectively manage soil P. The aim of this research was to investigate the influence of SOM on P sorption. The study was conducted in sandy soil profiles and in topsoils before and after removal of SOM with H2O2. The results were interpreted with the Langmuir and Freundlich isotherms. Our results indicated that SOM affected P sorption in sandy soils, but that P sorption also depended on specific soil properties (e.g. values of the degree of P saturation (DPS), P sorption capacity (PSC) and pH) often related to land use. Removal of SOM decreased PSC in most of the topsoils tested; other soil properties became important in controlling P sorption. An increase in P desorption observed after SOM removal indicated that SOM was potentially that soil constituent which increased P binding and limited P leaching from these sandy soils. [ABSTRACT FROM AUTHOR]

Some dairy cows excrete large amounts of P through their urine; thus, it was speculated that a genetic defect related to their efficiency in uptake of P or recirculation of P could cause such an effect. This speculation was pursued in a cross sectional study on 139 cows (103 Holstein and 36 Jersey) from an experimental herd using repeated sampling of urine (301 samples) to investigate sources of variation in urinary P concentration (Pu). Urine samples were taken on 6 testing sessions spread over 2 mo. Each sample was obtained by mild manual stimulation of the rear udder escutcheon area. The samples were immediately assayed for pH, stored frozen, and assayed for inorganic P and creatinine. Concentrations of P and creatinine in urine, the ratio of Pu to creatinine, and pH were analyzed using a linear mixed model. The model included fixed effects of breed, parity number, and sampling session. Stage of lactation was fitted as Wilmink-type lactation curves. Random effects included additive polygenic ancestry, permanent animal effects, and residual. The distribution of Pu approximated normality except for a single sample with very high Pu and very low pH. This sample came from a cow diagnosed independently with ketosis. For the remaining samples, it was shown that Pu has low to moderate heritability (0.12) and is only moderately repeatable (0.21). Based on a small data set, it is tentatively concluded that individual differences between cows exist in their Pu, and individual differences presumably result from genetic differences. However, it remains unclear if cows with genetically lower or higher Pu will perform better on a low-P diet. [ABSTRACT FROM AUTHOR]

The main objective was to determine the nitrogen and P retention and energy digestibility of immunological castrates (IC), entire males (EM), physical castrates (PC), and gilts (G) during 3 growth phases. A second objective was to compare growth performance among the sexes. The final objective was to determine the carcass iodine value (IV) among the sexes. Twelve individually housed pigs (PIC 337 ? C22/29) of each sex with an initial mean BW of 35.7 ± 0.6 kg and a final BW of 145.0 ± 1.3 kg were evaluated. Anti-gonadotropin-releasing factor injections were administered at d 23 and 15 for groups 1 and 2, respectively. The second injection was given on d 56 of the 98-d experiment. Nitrogen, P, and energy digestibility were measured the last 3 d of the 10-d metabolism period starting at mean BW of 39.5 ± 0.6, 73.7 ± 0.8, and 105.5 ± 0.9 kg for periods 1, 2, and 3, respectively. The third collection started 14 d after the second injection. Entire males and IC had superior overall ADG compared to PC and G (P < 0.05). Entire males and G had the lowest overall ADFI, and PC had the greatest, with IC being intermediate (P < 0.05). Entire males were overall the most efficient, followed by IC, with PC and G being the least efficient (P < 0.05). Immunological castrates and EM had similar nitrogen retention (g/d) for the first 2 collection periods (P > 0.05). In the third collection period, nitrogen retention of IC was similar to that of both EM and PC (P < 0.05). Phosphorus retained (g/d) was not different among the sexes in the first collection; during the second collection, EM retained the greatest amount of P, G and PC retained the lowest, with IC being similar to all sexes. For the third collection, IC had P retention similar to that of EM, EM had retention similar to that of PC, and PC had retention similar to that of G (P > 0.05). However, G retained less P than EM or IC (P < 0.05). Apparent total tract digestibility of DM and GE and the DE of the diet did not differ among the sexes in any of the collection periods (P > 0.05). The jowl IV was the lowest in IC and PC and highest in EM, with G being similar to all sexes (P < 0.05). For the belly, EM had the highest IV, with the other 3 sexes being similar. In conclusion, 2 wk after the second injection, IC transition to become more similar to PC in terms of nitrogen utilization but are still similar to EM in P utilization. These data suggest a feeding program for IC that is intermediate between EM and PC is required to meet their nutritional requirements. [ABSTRACT FROM AUTHOR]

Periphyton was sampled from an artificial substrate in situ at 8-day intervals in the littoral zone of four shallow lakes with different trophic status. Phosphorus and chlorophyll a were determined including different phosphorus fractions. There was a strong correlation between periphyton chl a levels and the amount of total phosphorus in the lakes, indicating that the phosphorus retention ability of periphyton increased with periphyton mass. The amounts of total phosphorus and chemically extractable phosphorus in periphyton were greater in two of the lakes, Nanhu and Donghu, than in the other two lakes, Niuchaohu and Liangzihu. The greatest chl a and total phosphorus concentrations in periphyton were 103 and 129 μg cm −2 , respectively, in Nanhu. The amount of total phosphorus was significantly associated ( r > 0.881) with the chl a concentration and amounts of Fe/Al-bound phosphorus and Ca-bound phosphorus in the periphyton. Most of the total phosphorus in the periphyton was inorganic phosphorus, which mainly consisted of Fe/Al-bound phosphorus and Ca-bound phosphorus; the organic phosphorus fraction only made up 20%, on average, of total phosphorus. Fe/Al-bound phosphorus was the dominant fraction and its relative contribution to total phosphorus in the lakes was 59% (Nanhu), 46% (Donghu), 44% (Niuchaohu), and 38% (Liangzihu). These data demonstrated that periphyton in eutrophic lakes could retain considerable amounts of phosphorus and that high levels of Fe/Al-bound phosphorus are an important early warning symptom of eutrophication. [ABSTRACT FROM AUTHOR]

Seven constructed wetlands (0.05–0.69 ha), situated in agricultural catchments (22–267 ha) in the south of Sweden, were studied for two years with two aims: to (i) quantify their function as sinks for particles and phosphorus (P) lost from the catchments, and (ii) investigate to what degree catchment and wetland characteristics and modeled loads (using hydrochemical catchment models) could be used to explain differences in retention between the wetlands. The wetland areas ranged from 0.04 to 0.8% of the respective catchment area, and they were situated in areas dominated by fine-textured soils with relatively high P losses and the main proportion of P transported in particulate form. Net P and particle retention were estimated during two years from annual accumulation of particles on sedimentation plates (40 × 40 cm) on the bottom of the wetlands. There was an annual net retention of particles and P, but with a large variation (for particles 13–108 t ha −1 yr −1 and for P 11–175 kg ha −1 yr −1 ), both between wetlands and between years. The difference between the two years was larger than the difference in mean P retention between the seven wetlands. There was a positive relationship between P and particle retention and three catchment factors, i.e. P status (P-AL) of agricultural soils, average slope in the catchments and the livestock density, and a negative relationship with the agricultural soil clay content. In addition, there was a positive relationship with the wetland length:width ratio. Contrary to expectations, neither the modeled hydraulic load nor P load was significantly correlated with the measured particle and P retention. There was also a positive relationship between P concentration in the sediment and soil P status in the catchment. The results imply that considerable errors are introduced when down-scaling modeled regional nutrient losses to estimate the P loads to small wetlands in agriculturally dominated catchments. A more qualitative approach, using catchment characteristics for identification of hot-spot fields, may be equally good to identify suitable locations for constructed wetlands to reduce diffuse P loads. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the efficiency of an intensified process of vertical flow constructed wetland having the following particularities: (i) biological pretreatment by trickling filter, (ii) FeCl3 injection for dissolved phosphorus removal and (iii) succession of different levels of redox conditions along the process line. A pilot-scale set-up designed to simulate a real-scale plant was constructed and operated using real wastewater. The influences of FeCl3 injection and water saturation level within the vertical flow constructed wetland stage on treatment performances were studied. Three different water saturation levels were compared by monitoring: suspended solids (SS), total phosphorus (TP), dissolved chemical oxygen demand (COD), ammonium, nitrate, phosphate, iron, and manganese. The results confirmed the good overall efficiency of the process and the contribution of the trickling filter pretreatment to COD removal and nitrification. The effects of water saturation level and FeCl3 injection on phosphorus removal were evaluated by analysis of the correlations between the variables. Under unsaturated conditions, good nitrification and no denitrification were observed. Under partly saturated conditions, both nitrification and denitrification were obtained, along with a good retention of SSs. Finally, under saturated conditions, the performance was decreased for almost all parameters. [ABSTRACT FROM AUTHOR]

Catch crops are a potential option to reduce phosphorus (P) losses, but little is known about their establishment success and capacity to retain P on clayey soils in regions with short autumns, e.g. Sweden. This study screened biomass production and P retention by eight catch crop species: the perennials chicory ( Cichorium intybus L.), cocksfoot ( Dactylis glomerata L.), perennial ryegrass ( Lolium perenne L.) and red clover ( Trifolium pratense L.) and the annuals phacelia ( Phacelia tanacetifolia L.), white mustard ( Sinapis alba L.), oilseed radish ( Raphanus sativus L. oleiformis ) and white radish ( R. longipinnatus ). The catch crops were grown at six field sites, where the perennial species were under-sown with barley and the annual species were after-sown following barley harvest. Biomass production, P content in above-ground and below-ground plant parts and content of available P in the soil were determined in autumn and survival rate of the catch crops in the following spring. Biomass production and P retention in autumn both differed significantly between species ( p < 0.0001), and were greatly affected by site-specific conditions and time of sowing, which differed between experiments. Growth of catch crops can also be suppressed by low precipitation. Content of P in roots varied substantially between species, a factor which must be considered in species comparisons. The under-sown species produced more or equivalent amounts of biomass, retained more or equivalent amounts of P in autumn and survived better over winter than the after-sown species. Thus under-sown catch crops generally seem more suitable as catch crops for P. [ABSTRACT FROM AUTHOR]

The use of vertical flow constructed wetlands (VFCW) is growing rapidly in Europe for domestic wastewater treatment in small communities. In order to improve denitrification and dephosphatation as compared to classical VFCW, the Azoé-NP ® process has been developed. The process line consists of: a biological aerobic trickling filter as a primary treatment stage, ferric chloride (FeCl 3 ) addition for phosphorus (P) treatment and two stages of partially saturated VFCW. A municipal wastewater treatment plant using Azoé-NP ® process has been monitored during eight years through 44 campaigns of 24 h time-proportional inlet–outlet sampling followed by analyses of TSS, BOD 5 , COD, TKN, NO 3 –N and TP concentrations. The results revealed good performances of the overall treatment. To better characterize the performance of each treatment step, five additional 24 h monitoring campaigns were performed with samples taken from four different points along the treatment line. Results showed a good performance in dissolved carbon removal and nitrification by the trickling filter. The main part of the treatment was found to be done by filtration throughout the first filtration stage. Nitrate removal was achieved principally at the second filtration stage. Phosphorus migration through the first stage and its slight retention at the second stage was observed. [ABSTRACT FROM AUTHOR]

Phytase, a widely used feed additive in poultry diets, increases P availability and subsequently reduces inorganic-P supplementation and P-excretion. Phytase supplementation effect on P-retention in poultry has been investigated, but the effect sizes were highly variable. The present study's objective was to conduct several meta-analyses to quantitatively summarize the phytase effect on P-retention in broilers and layers. Data from 103 and 26 controlled experiments testing the phytase effect on P-retention were included in 2 separate meta-analyses for broilers and layers, respectively. The mean difference calculated by subtracting the means of P-retention for the control group from the phytase-supplemented group was chosen as an effect size estimate. Between-study variability (heterogeneity) of mean difference was estimated using random-effect models and had a significant effect (P < 0.01) in both broilers and layers. Therefore, random-effect models were extended to mixed-effect models to explain heterogeneity and obtain final phytase effect size estimates. Available dietary and bird variables were included as fixed effects in the mixed-effect models. The final broiler mixed-effect model included phytase dose and Ca-to-total-P ratio (Ca:tP), explaining 15.6% of the heterogeneity. Other variables such as breed might further explain between-study variance. Broilers consuming control diets were associated with 48.4% P-retention. Exogenous phytase supplementation at 1,039 FTU/kg of diet increased P-retention by 8.6 percentage units on average. A unit increase of phytase dose and Ca:tP from their means further increased P-retention. For layers, the final mixed-effect models included dietary Ca, age, and experimental period length. The variables explained 65.9% of the heterogeneity. Layers receiving exogenous phytase at 371 FTU/kg were associated with a 5.02 percentage unit increase in P-retention. A unit increase in dietary Ca from its mean increased P-retention, whereas an increase in the experiment length and layer's age decreased P-retention. Phytase supplementation had a significant positive effect on P-retention in both broilers and layers, but effect sizes across studies were significantly heterogeneous due to differences in Ca contents, experiment length, bird age, and phytase dose. [ABSTRACT FROM AUTHOR]

The total phosphorus (TP) removal efficiency from organic wastewater (pig farm and distillery wastewater) were estimated by using filamentous green algae (FGA) and benthic algal mats (BAM) treatment systems under laboratory conditions, and the contents of periphyton phosphorus fractions were determined by using a sequential extraction. The removal rates of TP reached 59-78% within the first 8 days of all treatment systems and could achieve average 80% during 30 day period, and the phosphorus removal rates by using BAM was higher than that of FGA. The ability of retention TP of periphyton enhanced gradually, the BAM TP contents were higher than that of FGA, the highest TP concentrations of BAM and FGA were 26.24 and 10.52 mg P g-1·dry weight. Inorganic phosphorus (IP) always exceeded 67.5% of TP, but the organic phosphorus fraction only made up less than 20% of TP. The calcium-binding phosphorus (Ca-P) was the dominant fraction and its relative contribution to TP was more than 40%. The TP was also strongly and positively correlated with the IP and Ca-P (p <0.01) in periphyton. It showed that the periphyton had a potential ability of rapid phosphorus removing and remarkable retention from wastewater with high load phosphorus. [ABSTRACT FROM AUTHOR]

Abstract: Two trials were conducted to evaluate the nutrient digestibility of river crab (RC) (Procambarus clarkii) and marine crab (MC) (Chaceon affinis) meals in diets for red porgy (Pagrus pagrus) and the effect on ammonia-N excretion and P and Ca retentions. In trial I, the apparent digestibility coefficient (ADC) of nutrients and energy contents in RC and MC meals were determined. Results showed that, the ADC values for protein, lipids, ash, dry matter and gross energy were significantly higher for MC than for RC meal. Both crab meals were efficiently digested despite their high chitin and ash contents. In trial II, red porgy were fed over 6months with five diets: a control diet (CD) based on high quality fish meal (FM), and four diets where FM protein was replaced at a rate of 10% or 20% by protein derived from either RC or MC meal (RC10, RC20, MC10 and MC20). Replacement of the FM protein by RC or MC proteins had no effect both on protein utilisation and ammonia-N excretion rates, which ranged from 105 to 119mg N–NH4 + kg−1 day−1 for all diets. A linear increase was observed in the dietary Ca/P ratio by the increase of the dietary RC and MC meal inclusions, resulting in a reduction in the whole fish body content of P, Ca and ash with interesting similar whole body Ca/P ratio (1.59–1.63) for all treatments. Accordingly, Ca, P and ash retention rates were significantly reduced by increasing the dietary proportion of both crab meals. Moreover, a negative relationship between fish growth and final whole body Ca, P and ash contents was obtained. However, no significant differences were observed in total P excretion value (kgPt−1). [Copyright &y& Elsevier]

Highlights: [•] Newly established helophytes in rewetted fens strongly influence the P cycle. [•] P uptake from helophytes compensates for P release from highly decomposed peat. [•] Most P in aboveground biomass will be released due to leaching and decomposition. [•] To achieve low nutrient conditions rewetting should be combined with above-ground plant biomass removal. [•] Plant-available P might be exhausted in 20–50y if biomass removal is performed. [ABSTRACT FROM AUTHOR]

The study aimed to determine the ileal phosphorus (P) digestibility (iPD) and the excreta P retention (ePR) of 5 monodicalcium phosphate (MCP) samples and 3 dicalcium phosphate (DCP) samples in broiler chickens and in Pekin ducks using the substitution method. A total of 720, 21-d-old Arbor Acres broiler chickens in experiment 1 and 720, 15-d-old Pekin ducks in experiment 2 were randomly allocated to 9 dietary treatments with 8 replicate cages (10 birds/cage) based on the similar mean body weight, respectively. The collection of excreta (for 72 h after a 3-d acclimation) and ileal digesta (after 6 d of feeding experimental diets) was done. The results showed the average iPD/ePR of MCP and DCP for broilers were 83.11%/74.52% and 75.34%/69.46% and for ducks were 79.37%/80.02% and 75.74%/76.44%, respectively. The iPD/ePR of MCP in broilers and the ePR of MCP in ducks were markedly higher (P < 0.05) than those of DCP. Our data suggest that using the substitution method to evaluate the bioavailability of feed phosphates has its own advantages; MCP has higher biological availability than DCP for broilers and ducks. [ABSTRACT FROM AUTHOR]

Frequent freeze–thaw cycles (FTCs) can profoundly affect the chemical properties of soils. We conducted laboratory experiments to explore the effects of freeze–thaw treatments on phosphorus (P) adsorption (Pads) and desorption (Pdes) and to determine the capacity of P retention (Pret) via Padsand Pdesin the fertile black soil of northeastern China. The effects of 0, 1, 3, 6, and 10 FTCs on soil P adsorption and desorption were determined. Each cycle consisted of freezing for 12 h at −10 °C and thawing for 12 h at +7 °C, mimicking a diurnal pattern, at initial soil-moisture contents of 20%, 30%, 40%, and 50% and at amounts of added P of 10, 20, 40, 60, and 80 mg P L−1. Padsincreased significantly with increasing amounts of added P. The freeze–thaws of black soils significantly decreased Padsand buffering capacities, which would promote the release of adsorbed P and increase the risk of reducing soil P. High moisture content also affected the behavior of soil P adsorption by reducing adsorbed P as the number of FTCs increased. The P-isotherm data for all soils at equilibrium-P concentrations fit the Langmuir equation well (R2= 0.93 or higher). Padshad exponential and linear relationships with Pdescapacity and Pretcapacity, respectively. [ABSTRACT FROM AUTHOR]

Nutrient ratios have been related to nutrient limitation of algal growth in lakes. Retention of nutrients in lakes, by sedimentation and by denitrification, reduces the nutrient concentrations in the water column, thereby enhancing nutrient limitation. Differential retention of nitrogen and phosphorus alters their ratios in lakes and thereby contributes to determine whether nitrogen or phosphorus limits algal growth. We examined the relationships between differential nutrient retention, nutrient ratios, and nutrient limitation in Lake Brunner, a deep oligotrophic lake. The observed retention of nitrogen (20%) and phosphorus (47%) agreed with predictions by empirical equations from literature. As a result of differential retention with a much larger proportion of phosphorus retained than that of nitrogen, the nitrogen:phosphorus ratio was higher in the lake (69) than in the inflows (46). While the mean ratio in the inflows suggested no or only moderate phosphorus limitation, the lake appeared to be severely phosphorus limited. Combining empirical equations from literature that predict nitrogen and phosphorus retention suggests that the nitrogen:phosphorus ratio is enhanced by greater retention of phosphorus compared to nitrogen only in deep lakes with relatively short residence times, such as Lake Brunner. In contrast, in most lakes differential retention is expected to result in lower nitrogen:phosphorus ratios. [ABSTRACT FROM AUTHOR]

Plant availability and risk for leaching and/or runoff losses of phosphorus (P) from soils depend among others on P concentration in the soil solution. Water-soluble P in soil measures soil solution P concentration. The aim of this study was to understand the effect of wheat residue char (biochar) addition on water-soluble P concentration in a wide range of biochar-amended soils. Eleven agricultural fields representing dominant soil texture classes of Swedish agricultural lands were chosen. Concentrations of water-soluble P in the soils and in biochar were measured prior to biochar incorporation to soils in the laboratory. Experiments with three dominant soil textures-silt loam, clay loam, and an intermediate loam soil with different rates of biochar addition (i.e., 0.5, 1, 2, and 4 %; w/ w) showed that the highest concentration of water-soluble P was achieved at an application rate of 1 %. At higher application rates, P concentrations decreased which coincided with a pH increase of 0.3-0.7 units. When the 11 soils were amended with 1 % ( w/ w) biochar, water-soluble P concentrations increased in most of the soils ranging from 11 to 253 %. However, much of the water-soluble P added through the biochar was retained (33-100 %). We concluded that wheat residue char can act as a source of soluble P, and low and high additions of biochar can have different effects on soil solution P concentration due to possible reactions with Ca and Mg added with biochar. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to develop an input/output mass balance to predict phosphorus retention in a five pond constructed wetland system (CWS) at Greenmount Farm, County Antrim, Northern Ireland. The mass balance was created using 14-months of flow data collected at inflow and outflow points on a weekly basis. Balance outputs were correlated with meteorological parameters, such as daily air temperature and hydrological flow, recorded daily onsite. The mass balance showed that phosphorus retention within the system exceeded phosphorus release, illustrating the success of this CWS to remove nutrients from agricultural effluent from a dairy farm. The last pond, pond 5, showed the greatest relative retention of 86%. Comparison of retention and mean air temperature highlighted a striking difference in trends between up-gradient and down-gradient ponds, with up-gradient ponds 1 and 2 displaying a positive quadratic relationship and down-gradient ponds 3 through 5 displaying a negative quadratic relationship. [Copyright &y& Elsevier]

We analysed phosphorus retention as a function of external loading, hydraulic turnover time, area and relative depth on the basis of published data from 54 lakes and reservoirs in different climate regions around the world. Our analysis demonstrated that reservoirs and lakes that received higher areal loading of phosphorus (TP) also retained more P per m but the proportion of the external P loading retained in the waterbody (retention coefficient, R) remained generally independent of TP. The waterbodies with longer hydraulic residence times ( T) retained larger proportions of external P and the correlation between R and T was much stronger in lakes with areas larger than 25 km than in the whole data set. TP and T together determined 78% of the variation in R in large lakes. We also partially confirmed our hypothesis that waterbodies with bigger relative depths ( Z) retain more of the external phosphorus than larger and shallower waterbodies with lower Z. The hypothesis was, however, validated only for lakes larger than 25 km and for those with T <0.3 year, where R increased significantly with increasing Z. In stratified lakes, increasing relative depth correlated with reduced P retention capacity, demonstrating the complex nature of phosphorus biogeochemistry in lake ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Social, economic and environmental coherence is sought in the management of livestock wastewater. Wetlands facilitate the biogeochemical processes that exploit livestock wastewater and provide opportunities to achieve such coherence and also to deliver on a range of ecosystem services. The Integrated Constructed Wetland (ICW) concept integrates three inextricably linked objectives: water quantity and quality management, landscape-fit to improve aesthetic site values and enhanced biodiversity. The synergies derived from this explicit integration allow one of the key challenges for livestock management to be addressed. An example utilizing twelve ICW systems from a catchment on the south coast of Ireland demonstrates that over an eight year period mean reduction of total and soluble phosphorus (molybdate reactive phosphorus) exceeded 95% and the mean removal of ammonium-N exceeded 98%. This paper reviews evidence regarding the capacity of ICWs to provide a coherent and sustainable alternative to conventional systems. [Copyright &y& Elsevier]

Abstract: The 2nd International Symposium on Wetland Pollutant Dynamics and Control (WETPOL 2007), organised by the Department of Geography of the University of Tartu (Estonia) in co-operation with partners from the Estonian University of Life Sciences (Tartu, Estonia), Ghent University (Belgium), and the UNESCO-IHE (Delft, The Netherlands), was held 16–20 September 2007, in Tartu, Estonia. At this meeting, 140 oral presentations (including 9 keynote speeches) and 70 posters by representatives from 38 countries were presented. About half of the presentations considered purification processes in both semi-natural and constructed wetlands. The editorial paper highlights trends in studying the cycling of nitrogen, phosphorus, carbon, heavy metals, and organic pollutants in wetlands, but also in the modelling of pollutant removal and the functioning of plants in the wetland environment. It also describes the WETPOL 2007 meeting, which served as the source of the selected papers, and briefly explains the main aspects of these papers. [Copyright &y& Elsevier]

In streams, coarse particulate organic matter (CPOM) acts as a substrate for microbial activity, which promotes nutrient retention. However, in urban areas, increased peak flows within streams lead to decreased retention of CPOM. The aim of this study was to investigate whether the reintroduction of CPOM, in the form of leaf litter, into a degraded urban stream would increase biofilm activity and phosphorus retention, two ecosystem functions that reflect the integrity of the ecosystem. Stream metabolism and nutrient retention were assessed in treated (T) and control (C) channels of the Torrens River Catchment, South Australia, before and after CPOM addition. Gross primary production and community respiration (CR) were measured as oxygen production and consumption within benthic chambers. Phosphorus retention was measured through a series of short-term filterable reactive phosphorus (FRP) addition experiments. Before CPOM addition, there were no differences in CR, but C retained 6.8% more FRP than T. After CPOM addition, CR was greater in T than in C (572 and 276 mg O2·m−2·day−1, respectively), and T retained 7.7% more FRP than C. The increase in FRP retention in T compared to C was attributed to phosphorus limitation of the CPOM and increased demand for phosphorus of the attached microbial heterotrophic community. The reintroduction of CPOM into degraded streams will be an important step in the restoration of stream metabolism and nutrient retention. Maintenance of CPOM may be achieved through restoration of riparian vegetation, a reduction in the increased peak flows, and rehabilitation of stream morphology. [ABSTRACT FROM AUTHOR]

Inputs of available nitrogen (N) to ecosystems have grown over the recent past. There is limited general understanding of how increased N inputs affect the cycling and retention of other potentially limiting nutrients. Using a plant-soil nutrient model, and by explicitly coupling N and phosphorus (P) in plant biomass, we examine the impact of increasing N supply on the ecosystem cycling and retention of P, assuming that the main impact of N is to increase plant growth. We find divergent responses in the P cycle depending on the specific pathway by which nutrients are lost from the ecosystem. Retention of P is promoted if the relative propensity for loss of plant available P is greater than that for the loss of less readily available organic P. This is the first theoretical demonstration that the coupled response of ecosystem-scale nutrient cycles critically depends on the form of nutrient loss. P retention might be lessened, or reversed, depending on the kinetics and size of a buffering reactive P pool. These properties determine the reactive pool's ability to supply available P. Parameterization of the model across a range of forest ecosystems spanning various environmental and climatic conditions indicates that enhanced plant growth due to increased N should trigger increased P conservation within ecosystems while leading to more dissolved organic P loss. We discuss how the magnitude and direction of the effect of N may also depend on other processes. [ABSTRACT FROM AUTHOR]

The effect of phytase supplementation to a low fish meal based diet on growth performance and phosphorus utilisation was investigated in sex-reversed red tilapia. Diets were prepared without phytase or inorganic phosphorus supplementation, with phytase, with supplemented inorganic phosphorus and with both phytase and supplemental inorganic phosphorus. Available phosphorus was set below requirement and the total phosphorus set to meet requirement for tilapia. After 8 weeks, there were significant differences in weight gain and protein utilisation between diets. There was an effect of phytase addition and inorganic phosphorus supplementation on bone phosphorus and whole-body phosphorus (p<0.05). A significant effect was also observed on phosphorus digestibility, phosphorus retention efficiency and phosphorus load of the water. Phosphorus digestibility and retention efficiency were significantly (p<0.05) higher, and phosphorus load of the water was significantly (p<0.05) lower in fish fed the phytase supplemented diet compared with diets containing supplemental inorganic phosphorus and the basal diet. In conclusion, phytase increased phosphorus availability, therefore reducing the need to add inorganic phosphorus and reducing phosphorus waste from low fish meal based diets for tilapia. [ABSTRACT FROM AUTHOR]

The current best option to upgrade constructed wetlands (CWs) for phosphorus (P) retention, in terms of efficiency, cost and simplicity, consists in using media having a strong P affinity. The media can be used either in the planted beds or in a filtration system downstream of the beds. The use of slag filters was shown to be efficient for removing P from wastewater as it represented a slow release source of calcium and hydroxide, favouring the formation of hydroxyapatite. Our study aimed at maximising the P retention capacity of slag filters located at the outlet of CWs since electric arc furnace slag has been shown to inhibit the growth of macrophytes when used in the filtration matrix. Bench-scale columns (Vtot = 6.2 L) filled with various combinations of filter media (slag, granite, limestone) of different sizes (2-5, 5-10, 10-20 mm) were fed on-site during four months with a CW effluent (in mg/L: 30 COD, 30 TSS, 10 Pt). Results showed that the best media combination enabling the maximum o-PO4 retention (more than 80% removal without clogging) consisted in a series of a ternary mix column (slag 5-10 mm, granite 2-5 mm, limestone 5-10 mm) followed by a slag column (slag 5-10 mm). Pilot scale columns (Vtot = 300 L), filled with the best media combination, were installed at the outlet of a 28m² CW. These columns showed more than 75% removal efficiency during one year and were designed to be easily replaced each year. [ABSTRACT FROM AUTHOR]

Phosphate interacts with inorganic sediment particles through sorption reactions in streams. Collectively, this phosphorus (P) buffering mechanism can be an important determinant of soluble reactive P (SRP) concentrations. If sorption reactions control SRP concentrations in a stream, then differences in sediment characteristics may cause spatial differences in SRP concentrations. This prediction was tested by examining sediment-buffering characteristics and spatial variation in SRP among reaches with distinct sediment composition (i.e., fine versus coarse particles) in two tributaries of Boulder Creek, a headwater stream in central Wisconsin. SRP concentrations were significantly lower and algal available P and P sorption capacity were significantly higher in the reach dominated by fine sediments. Although fine particles such as sand had the greatest P sorption capacity, no retention could be attributed to biotic processes, whereas over 50% of P retention in coarse particles such as gravel could be linked to biotic uptake. Equilibrium P concentration (EPC0) assays from different sediment fractions also indicate that biotic uptake is relatively unimportant in sand particles (EPClive 10 μg/L: EPCkilled 10 μg/L) but very important in gravel or larger particles (EPClive 10 μg/L: EPCkilled 80 μg/L). Thus, sediment influence on stream water P concentrations can shift predictably from abiotic sorption in reaches with fine particles to biotic retention in areas dominated by coarse sediments. Consequently, changes in sediment composition due to natural or anthropogenic disturbance have the potential to alter the type and strength of sediment-associated processes determining ambient stream P concentrations. [ABSTRACT FROM AUTHOR]

Abstract: Controlling phosphorus (P) inputs to lakes remains a priority of lake management. This study develops watershed P balances for 11 recreational lakes in Minnesota. Areal P input rates to the watersheds ranged from 0.32 to 6.0kgPha−1 year−1 and was linearly related to the percentage of watershed in agriculture. Watershed P retention ranged from 10% to 89% of input P. Although many best management practices work to increase P retention (by trapping P in basins; reducing erosion; filtration), P retention is not sustainable indefinitely, particularly in “hot spots” such as septic leach fields and heavily manured fields. The watershed P balance tool is a framework that can allow watershed managers to develop novel strategies for managing P. P management strategies should be developed to keep P inputs and exports in balance so that P does not accumulate; long-term P accumulation is not sustainable and can eventually lead to lake eutrophication. [Copyright &y& Elsevier]

Abstract: Electric arc furnace (EAF) steel slag and serpentinite were tested in columns either alone or mixed with limestone to determine their capacity to remove phosphorus (P) from a solution containing initially 20mg P/L (for 114 days) than 400mg P/L (for 21 days). EAF steel slag was nearly 100% efficient due to specific P adsorption onto metal hydroxides and precipitation of hydroxyapatite. Serpentinite also showed a good performance that decreased with time, adsorption appearing to be the dominant mechanism for P removal. Mixing limestone with these two materials did not improve their performance and in the case of serpentinite, it actually even decreased it. In 114 days of experimentation, serpentinite alone and the mixture of serpentinite and limestone removed 1.0mg P/g while in 180 days of experimentation, EAF steel slag and the mixture of slag and limestone removed an average of 2.2mg P/g, without attaining their maximum P removal potential. The void hydraulic retention time (HRTv) was a key factor for growing hydroxyapatite crystals and had a significant effect on P removal efficiency by EAF steel slag. A temporary increase in HRTv caused by clogging resulted in an increase in EAF steel slag efficiency (from 80% to almost 100%) towards the end of investigation. Results from this study indicate that the use of EAF steel slag in constructed wetlands or filter beds is a promising solution for P removal via adsorption and precipitation mechanisms. [Copyright &y& Elsevier]

In order to verify methods for minimizing waste output of phosphorus (P) into the water and preserve an adequate growth rate in rainbow trout, a succession of two feeding trials were performed employing three test diets that were formulated with a low proportion of fish meal (FM), low-P ingredients (defatted soybean meal, corn gluten meal, feather meal, and blood meal), and varying levels of monocalcium phosphate (MCP) as a P supplement (0, 0.5 and 1% of diet which represent 0, 1 and 2 mg/g of available P, respectively). Total P concentrations achieved were 6.2, 8.7 and 9.6 mg/g, respectively. A control diet was formulated with FM as the main protein source and without MCP (total P content was 17.0 mg/g). Diets were fed until apparent satiation to duplicate groups of 50 (1.5 g) and 15 fish (147.8 g) during 24 and 14 weeks, respectively. In both cases, the lowest growth was observed in fish fed the basal diet without MCP. The test diet supplemented with 0.5% MCP provided growth and feed performance comparable to that obtained in fish fed the control diet. These results suggest that diets formulated with low-P ingredients should be supplemented with an adequate amount of P in order to meet the fish requirements and reduced diet-related P loading. [ABSTRACT FROM AUTHOR]

Abstract: Two international meetings on ecological engineering, with a focus on riparian buffer zones, served as the source for selected papers in this special issue: (1) an International Workshop on Efficiency of Purification Processes in Riparian Buffer Zones: Their Design and Planning in Agricultural Watersheds, jointly organised by Hokkaido University, Japan, the National Agricultural Research Center for Hokkaido Region, Japan, Civil Engineering Research Institute of Hokkaido, Japan, and the Institute of Geography, University of Tartu, Estonia, and held from 5 to 9 November 2001 in Kushiro City, Hokkaido, Japan; and (2) an International Conference on Ecological Engineering for Landscape Services and Products, jointly organised by the International Ecological Engineering Society (IEES) and Lincoln University, Christchurch, New Zealand, and held from 25 to 29 November 2001 in Christchurch, New Zealand. At these two meetings, altogether 94 oral presentations (17 from invited speakers) and 15 posters by representatives from 21 countries were presented. The editorial paper highlights trends in investigation of the purification processes in riparian buffer zones as well as planning, design and management aspects of riparian buffers regarding the wide spectrum of their ecological functions; it characterises the two international meetings which served as sources for the selected papers and briefly explains the main aspects of these papers. [Copyright &y& Elsevier]