Reactive Phosphate Research Articles

Evaluation of seawater composition in a vast area from the Monte Carlo simulation of georeferenced information in a Bayesian framework

The detection of composition or pollution trends of vast environmental water areas, from a river, lake or sea, requires the determination of the mean concentration of the studied component in the studied area at defined depth in, at least, two occasions. Mean concentration estimates of a large area are robust to system heterogeneity and, if expressed with uncertainty, allow assessing if observed trends are meaningful or can be attributed to the measurement process. Mean concentration values and respective uncertainty are more accurately determined if various samples are collected from the studied area and if samples coordinates are considered. The spatial representation of concentration variation and the subsequent randomization of this model, given coordinates and samples analysis uncertainty, allows an improved characterization of studied area and the optimization of the sampling process. Recently, this evaluation methodology was described and implemented in a user-friendly MS-Excel file. This tool was upgraded to allow determinations close to zero concentration and “bottom-up” uncertainty evaluations of collected samples analysis. Since concentrations cannot be negative, this prior knowledge is merged with the original measurements in a Bayesian uncertainty evaluation that improves studied area description and sampling modelling. The Bayesian assessment avoids the underestimation of concentrations distribution by assuming that negative concentrations are impossible. This tool was successfully applied to the determination of reactive phosphate concentration in a vast ocean area of the Portuguese coast. The new version of the developed tool is made available as Supplementary Material.

Phosphorus Sources Combined with Doses of Organic Compost Increased the Population of Soil Microorganisms and P Level in the Soil and Plant and the Dry Matter of Sugarcane

The aim of the study was to evaluate the effect of P sources and filter cake, enriched or not with biofertilizers and liquid peat, on the microbial population and the soil available P levels and shoot dry matter and P accumulation by sugarcane. The experiment was conducted in a greenhouse in a completely randomized design with factorial arrangement 4 × 3 + 1 and three replications. The treatments consisted in four sources of P: simple superphosphate, triple superphosphate, monoammonium phosphate and reactive natural phosphate combined with three levels of organic compound: without filter cake, decomposed filter cake (30 t ha−1, dry basis) and decomposed filter cake enriched with liquid peat (4 mL kg−1 of filter cake) and biofertilizers (480 mL kg−1 of filter cake) and a control treatment without organic compound and without phosphorus. At 45 and 110 days after planting the total population of bacteria and fungi, phosphate-solubilizing microorganisms and total microorganisms were evaluated. After 60 and 110 days, the soil available P, plants’ P and dry matter and P accumulation were evaluated. The organic compound increased the population of soil microorganism, the soil P levels, the accumulation of P and dry matter by the plants, regardless of the source of P, although the enrichment with biofertilizer and liquid peat did not enhance this effect. In conclusion, the presence of organic compost enhances the effects of phosphate fertilization.

Soluble reactive phosphorous determination in wastewater treatment plants by automatic microanalyzers

The analysis of soluble reactive phosphate (SRP) in water is key to control water quality. In order to continuous monitor orthophosphate content in water during treatment processes and in the effluents of wastewater treatment plants, conventional procedures, usually performed in a laboratory, must be adapted. This means pursuing efforts on miniaturizing systems to operate in situ and automating analytical methods to work on-line. The design, construction and evaluation of an automatic and low cost cyclic olefin copolymer (COC)-based spectrophotometric microanalyzer, capable of operating in unattended conditions, is presented to monitor soluble reactive phosphorous, as orthophosphate ion, in wastewater samples coming from sewage treatment plants. The microsystem, constructed by CNC micromilling and using a multilayer approach, integrates microfluidics to carry out the phosphomolybdenum blue (PMB) reaction and an optical flow-cell for the spectrophotometric orthophosphate determination in a single polymeric substrate smaller than a credit card. It is connected to a compact optical detection system composed by a LED emitting at 660 nm and a PIN-photodiode, both integrated in a PCB. Flow management is automatically performed by programmed microvalves and micropumps, which control autocalibration processes and allow unattended operation. Analytical features after the optimization of the microfluidic platform and the chemical and the hydrodynamic variables, were a linear range from 0.09 to 32 mg L−1 P and a detection limit of 0.03 mg L−1 P with a sampling rate of 24 samples h−1, demonstrating the microanalyzer suitability for SRP monitoring in water. Moreover, real samples were analyzed obtaining promising results.

Assessing nutrient salts and trace metals distributions in the coastal water of Jeddah, Red Sea.

In this study, eighteen sites at Jeddah coastal area, Red Sea, have been assessed for water quality status, depending on nutrients, metals, Chlorophyll-a (Chl-a) and physical variables during 2018 and 2019. The investigated parameters of the Water Quality Index (WQI) are temperature, pH, salinity, dissolved oxygen (DO), DO saturation, oxidizable organic matter (OOM), suspended particulate matter (SPM), Chl-a, ammonium, nitrite, nitrate, total nitrogen, reactive phosphate, total phosphorus, silicate, Zn, Fe, Mn Cu, Cd, Pb, and Ni. The results revealed that the pH values were slightly alkaline with a range of 7.85–8.20. The results of other parameters were as follow: salinity (36.95–42.61PSU), DO (5.22–6.67 mg/L), OOM (0.40–1.23 mg/L), SPM (12.39–21.5 mg/L), Chl-a (0.10–0.83 µg/L). The range of nutrients (μM) were 0.07–0.22, 0.45–1.47, 9.62–18.64, 23.31–57.65, 0.05–0.15, 0.55–2.78 and 2.54–5.51 for NH4/N, NO2/N, NO3/N, TN, PO4/P, TP and SiO4/Si, respectively. Cluster analysis was used to classify the stations studied. From the current study, five clusters were found, indicating the need to perform cluster analysis in the water quality assessment process to confirm the durability and consistency of the data discovered in the current application.

Lanthanum based metal organic frameworks as a new binding agent material for diffusive gradient in thin film (DGT) technique in bioavailability of phosphate removal

High concentration of bioavailable phosphorus in aquatic system has been resulting in the eutrophication phenomenon that can trigger algae bloom. The measurement of bioavailable phosphorus in water body is needed. The diffusive gradient in thin film (DGT) is a well-developed in-situ analytical tool for separation and determination if bioavailable phosphorus or dissolver reactive phosphate (DRP). Using lanthanum based metal organic frameworks (La-MOF) with high surface area and tuneable pore might attribute the capacity of DRP adsorption in binding film. The surface area analysis of La-MOF powder was 84.957 m2 g−1. La-MOF then dispersed in gel solution to perform a binding film La-MOF then used in DGT tool for DRP uptake. The swelling activity of diffusive film was 2.24 and 1.93 for binding film La-MOF. The elution efficiency of DRP from binding film La-MOF was 95 % using HNO3 0.05 mol.L−1 as an eluent. The diffusion coefficient of DRP from La-MOF DGT was 2.216 × 10−6 cm2.s−1. Optimum DRP uptake capacity was up to 37.83 μg P with optimum time of deployment of 24 h. This research shows that the DRP uptake on DGT La-MOF was depended on the time deployment and DRP solution concentration.

Characterizing the water quality and microbial communities in different zones of a recirculating aquaculture system using biofloc biofilters

Recirculating aquaculture systems (RAS) using biofloc biofilters can address the high accumulation of nitrate (NO3−-N) and total suspended solids (TSS) in in-situ biofloc technology (BFT) aquaculture systems. A RAS was divided into the following four zones: reaction zones of the BFT biofilters, settling zones of the BFT biofilters, culture tanks, and a buffer tank. During the 95-day experimental period, the water quality parameters and microbial communities in different zones of the RAS were compared. The NO3−-N, nitrite (NO2−-N), total ammonia nitrogen (TAN), and TSS in the culture tanks were continuously controlled at average concentrations of 9.84 ± 5.15, 0.28 ± 0.15, 0.10 ± 0.18, and 96.92 ± 33.82 mg·L−1, respectively. Because denitrification produced alkalinity in the BFT biofilters, the alkalinity of the culture tanks reached an appropriate concentration of 109.40 ± 10.57 mg CaCO3·L−1 without intentional adjustment. The concentrations of NO3−-N, NO2−-N and TAN in the reaction zones were significantly lower than those in the influent (buffer tank) and culture tanks. However, there was no significant difference found for major water quality parameters between the reaction zones and the settling zones. There was also some removal of soluble reactive phosphate by the BFT biofilters, although there was no significant difference between the biofilters and influent. Microbial communities in the reaction zones were more diverse than those in the culture tanks, buffer tank and settling zones. Denitrifiers, nitrifying bacteria and important functional microbial populations for phosphorus removal were all present in the reaction zones, and at higher levels than those in other zones. Nitrogen and phosphorus removal were mainly achieved in the reaction zones of the BFT biofilters, and the microbial communities in the other three zones were similar. Besides, Scortum barcoo grew from an individual weight of 347.7 ± 73.0 to 472.1 ± 106.2 g, achieving a final stocking density of 32.81 kg·m−3 at the end of the experiment.

İzmir Körfezi’nden izole edilen Cylindrotheca closterium (Ehrenberg) Reimann & J. Lewin, 1964 türünün büyümesi üzerine ışık, sıcaklık, nütrient ve tuzluluğun etkileri

Cylindrotheca closterium is one of the diatom species that is dominant particularly in spring and summer in Izmir Bay and Aegean Sea. In this study, growth kinetics of Cylindrotheca closterium have been studied under different temperature, light intensity, nutrient concentrations and salinity conditions. Initially, temperature-light experiments were carried out and optimum temperature is determined to be 18 0C for this species. Obtained results at 18 0C are µmax= 1.97±0.167 d-1 for the maximum specific growth rate and KI=0.048± 0.028 for the half saturation constant. Then, six light intensities (0.9, 0.88, 0.74, 0.46, 0.2, 0.07 *100 μmol photon/m2s) and seven salinity concentrations (5, 10, 15, 20, 25, 30 ve 35 %0) were investigated on the growth rate of Cylindrotheca closterium under optimum temperature. The specific growth rate has been calculated to be 2.012 d-1 at 15 %0 salinity which is determined to be the optimum concentration. Exponential growth rates are obtained in semi-batch culture by measuring Chl a values and corresponded nutrient concentrations which are statistically valid (p<0,05) in regard to Monod equation (µ=µmax*S/KS+S) and µmax values, a parameter of Monod equation, are calculated for different concentrations of ammonium, nitrate, reactive phosphate and reactive silica are 2.48±0.61 d-1, 1.92 ±0.3 d-1, 2.1± 0.05 d-1 and 1.97± 0.20 d-1, respectively. KS values, which are another parameter of Monod equation, that are obtained for each nutrient are 17.84±14.4 μM NH4+-N, 27.3± 19.04 μM NO3--N, 0.25±0.04 μM PO4-P and 0.3±0.24 μM Si, respectively. As a result of global warming, temperature is expected to be risen 6 0C in 2100. The impacts of this increase on the growth rate of Cylindrotheca closterium species in Izmir Bay is calculated, considering this scenario. Nitrogen is determined to be the only restricting compound that inhibits growth during 52 weeks by a study that is conducted by Sunlu et al., (2007). Consequently, the growth rate of the species didn’t decline under 1.5 d-1 during this period of time.

Eficiência de Fertilizante Organomineral enriquecido com Ácido Cítrico em Milho (Zea Mays L.) cultivado em Casa de Vegetação

Este trabalho teve como objetivo avaliar o efeito do fertilizante organomineral enriquecido com ácido cítrico na acumulação de matéria seca e fósforo (P) em plantas de milho cultivadas em casa de vegetação. Utilizou-se o delineamento em blocos ao acaso, com fatorial 6x3, combinando seis fontes de P (superfosfato triplo, fosfato natural reativo de Bayóvar, superfosfato + cama de aviário, fosfato Bayóvar + cama de aviário, superfosfato + cama de aviário + ácido cítrico, fosfato Bayóvar + cama de aviário + ácido cítrico), três doses de P aplicado (40, 80 e 120 kg ha-1 de P2O5), com quatro repetições. Os fertilizantes organominerais produzidos com superfosfato triplo propiciaram maior acumulação de matéria seca e P na parte aérea de milho, do que os fertilizantes organominerais com fosfato Bayóvar. As plantas que receberam os fertilizantes organominerais com superfosfato apresentaram maior acumulação de biomassa e P na parte aérea que as plantas que receberam apenas superfosfato, sem efeito do ácido cítrico. O ácido cítrico adicionado ao fertilizante organomineral produzido com fosfato de Bayóvar aumentou a acumulação de P na raiz. Conclui-se que a incorporação de matéria orgânica ao fosfato solúvel aumenta o crescimento do milho e que a adição de ácido cítrico aos fertilizantes organominerais produzidos com fosfato natural aumenta a matéria seca de raiz.

Ammonium sulfate enhances the effectiveness of reactive natural phosphate for fertilizing tropical grasses

Reactive natural phosphate is a slow and gradual solubilizing fertilizer, which makes it difficult to use in neutral to alkaline soils. Nitrogen fertilizers which acidify the soil may increase the possibility of using this phosphate fertilizer commercially. Two greenhouse experiments were conducted to compare responses of Xaraés palisadegrass (Urochloa brizantha syn. Brachiaria brizantha cv. Xaraés) and Mombasa guineagrass (Megathyrsus maximus syn. Panicum maximum cv. Mombasa), when different combinations of P and N fertilizers were applied during the establishment phase in non-acidic soils or with corrected acidity. The experiments were carried out in a completely randomized design with 3 fertilizer combinations (simple superphosphate plus urea, SSU; natural reactive phosphate plus urea, RPU; and natural reactive phosphate plus ammonium sulfate, RPAS). There was no difference in tiller density, leaf numbers, forage mass, leaf mass and stem mass for either forage on SSU and RPAS treatments but they exceeded those on RPU. Soil pH was lower in soil fertilized with ammonium sulfate than in soil fertilized with urea. Applying natural reactive phosphate plus ammonium sulfate seems as effective as simple superphosphate plus urea in promoting increased growth in tropical grasses on low-P soils. Longer-term and more extensive field studies are needed to determine if these results can be reproduced in the long term, and the level of soil acidification over time.

Composted sewage sludge with sugarcane bagasse as a commercial substrate for Eucalyptus urograndis seedling production

Sewage sludge can be used as a source of organic matter and nutrients, whereas sugarcane bagasse can be used as a decompaction material; by composting a mixture of the two, a low-cost substrate for forest nurseries can be obtained. This research investigated the use of composted sewage sludge with sugarcane bagasse (CSB) as a commercial substrate in nurseries to grow seedlings of the hybrid clone Eucalyptus urograndis. Several CSB treatments were evaluated in comparison with a control (no P addition) and a commercial substrate (CS). Before composting, CSB was conditioned with P to increase its final concentration: CSB+1.5, 3.0, and 4.5% triple superphosphate (TP) or reactive phosphate (RP). After 120 d, the Eucalyptus response to all eight substrates was assessed by: i) plant morphological traits (H, height; D, diameter; SB, shoot biomass; RB, root biomass; TB, total dry biomass; GCI, green color intensity; and root system quality) and ii) chemical parameters of shoots and roots. Significant differences among treatments were ascertained using an ANOVA, and variability was interpreted using principal factor analysis (PFA). The treatment with CSB+3% TP (TP3.0) exhibited statistically (p < 0.05) higher performance in regards to morphological parameters (H, D, SB, TB) and the nutrient contents of shoots and roots (N, P, Ca, Na, Mn, Zn, and Cu) than the other treatments and control. The results suggest that B and K could play a fundamental role in both the observed variability and the improved plant performance in the TP3.0 substrate. PFA also showed i) the key role of OM as the primary source/sink of some pivotal macronutrients/heavy metals and ii) the existence of important antagonistic/synergistic effects between elements as a primary driver affecting the concentration/behavior of elements in the shoot/root system. Overall, the research demonstrated that with an addition of only 3.0% TP, the CSB performance was better than the most commonly used and widespread commercial substrate in industrial forest nurseries.

Multivariate Behavior of Irrigated Sugarcane with Phosphate Fertilizer and Filter Cake Management: Nutritional State, Biometry, and Agroindustrial Performance

Increases in production and final quality of the sugarcane crop require the search for new management and evaluation techniques within the production system, which can range from water and nutritional management, such as the application of water saving irrigation associated with sources (conventional and alternative) and phosphorus doses combined with the use of a sophisticated mathematical method, such as multivariate analysis. It can explain the variations caused by the application of irrigation and the sources and doses of phosphorus throughout the crop cycle. Due to the complex relationships and interactions of the soil-water-plant-atmosphere system, the use of multivariate analysis is able to indicate the best management options to be used. The experiment was carried out in a dystrophic Red Yellow Latosol, medium texture. The experiment consisted of randomized blocks and three replications in a 3 × 4 × 2 factorial design comprising three sources of phosphorus (triple superphosphate, Bayovar natural reactive phosphate, and Araxa natural phosphate) and different doses (0, 90, 180, and 360 kg of P2O5 ha−1) in the presence and absence of filter cake (7.5 Mg ha−1, dry basis). Irrigation with rescue equipment was applied in a single blade of 80 mm. Biometrics, nutritional status, and agroindustrial performance of sugarcane were evaluated. The principal component analysis evidenced that the phosphate fertilization associated with filter cake is responsible for increases in sugarcane biometrics, specially tillers at 6 months (0.589) and final tillering (0.577); nutritional status of iron (0.349), manganese (0.348), boron (0.347), sulfur (0.332), and phosphorus (0.331); and agroindustrial performance of sucrose (0.476), stalk yield (0.470), and total recoverable sugar (0.439). The water saving irrigation potentiated the use of phosphate fertilizer associated with filter cake, increasing the nutritional status of the plants. However, the correlation was irrelevant and or negative for levels of potassium and calcium. In addition, it favored biometrics and agroindustrial performance by expressing a direct and positive correlation with stalk yield, sucrose, and total recoverable sugar, but an inverse correlation between final tillering and plant height, tons of pol per hectare, and total recoverable sugar.

Effect of reactive phosphate rock to corn on acid sulphate soil in South Kalimantan

In South Kalimantan, acid sulphate soil rich in total phosphorus (P), but poor in available P, because of fixing. Most of the crops on the soil have a symptom of P deficiency. Reactive Phosphate Rock (phosphateR) was a slow-release P fertilizer and has a longer residual effect. This is to research on the effect of phosphateR to corn on acid sulphate soil in South Kalimantan. This research was carried out to determine the effects of reactive rock phosphate and planting method of corn on acid sulphate soil. This study used a factorial randomized block design with two factors. The first factor of P fertilizer, namely: P Fertilizer (SP 36), farmer practice, phosphate rock, phosphate rock + Manure, phosphate rock+ organic fertilizer+ phosphate rock+compost. The second factor is the planting method i.e: exsisting planting method (70x25 cm), Zig Zag Method (70x12,5 cm). The N and K doses are determined based on soil nutrient status. The results showed that phosphate treatment gave the weight of corncob where phosphate treatment with zig zag method reached 21% compared SP-36 with zig zag method treatment. And the lowest results are shown in the treatment of farmer practice with exsisting methods reached 10.07 t/ha corncob of weight.

Nutrient cycling in the Lower St. Lawrence Estuary: Response to environmental perturbations

We investigated the response of nutrient cycling in the Lower St. Lawrence Estuary (LSLE) to perturbations, using a linear three-box model that reflects summer stratification. The model is used to (i) test the sensitivity of each layer’s nutrient concentration (fixed-nitrogen, phosphorus, and silica) to perturbations in nutrient and water volume inputs to the LSLE, (ii) compute the response time of the system to a new steady state following a perturbation, and (iii) estimate the amount of oxygen consumed by respiration as bottom waters are advected through the LSLE. We find that the system adjusts rapidly to perturbations (half a year to reach 90% of the new steady state under a doubling of river input nutrient concentration). Most of the dissolved nutrients (60% of the fixed-nitrogen, 85% of the soluble reactive phosphate) that reach the surface waters in the LSLE originate from deeper waters. This dampens the effect of nutrients of anthropogenic origin on eutrophication (a doubling of river input nutrient concentration will lead to less than a doubling of bottom-water respiration rates). Our nutrient budget suggests that the Lower St. Lawrence Estuary acts as a nutrient pump for the Gulf of St. Lawrence and nitrate appears to be the limiting nutrient to surface productivity in the LSLE. This model can be used to test the impact of natural or anthropogenic perturbations on nutrient in the LSLE and oxygen concentrations in its bottom waters.

Distribution Characteristics and Spatial Differences of Phosphorus in the Main Stream of the Urban River Stretches of the Middle and Lower Reaches of the Yangtze River

Excessive phosphorus is the main problem of water pollution in the main stream of the Yangtze River, while it is not clear about the distribution characteristics and spatial differences of phosphorus in the urban river stretches of the middle and lower reaches of the Yangtze River. In this study, a field survey in June 2014 revealed that the average particulate phosphorus (PP) concentration ranged from 0.195 mg/L to 0.105 mg/L from Wuhan (WH) in the middle reaches of the Yangtze River to Shanghai (SH, 1081 km from WH) in the lower reaches of the Yangtze River, and the average PP-to-the total phosphorus (TP) ratio decreased from 85.71% in WH to 45.65% in SH, while the average soluble reactive phosphate (SRP) concentration ranged from 0.033 to 0.125 mg/L, and the average SRP-to-total dissolved phosphorus (TDP) ratio increased from 60.73% in WH to 88.28% in SH. In general, PP was still an important form of TP in the middle and lower reaches of the Yangtze River. The concentrations of PP and SRP at different sampling locations and water depths in the same monitoring section showed differences, which might be related to the transportation and sedimentation of suspended sediment (SS) and differences in the location of urban sewage outlets. Historical data showed that the concentration and particle size of the SS decreased over time, while the discharge of wastewater also increased over time in the Yangtze River Basin. The measured results showed that there was a significant positive correlation between SS and PP. As a result, the concentration of SRP might increase in the middle and lower reaches of the Yangtze River. If the SRP concentration is not properly controlled, the degree of eutrophication of water body could significantly increase in the Yangtze River estuary, the riparian zone of the urban river stretches, the tributary slow-flow section, and the corresponding lakes connected with the Yangtze River.

Combined Electrocoagulation and Chemical Coagulation in Treating Brewery Wastewater

Significant over-strength discharge fees are often imposed on breweries for the disposal of high-strength effluent to sanitary sewers. In this research work, the removal performances of electrocoagulation (EC) compared with operating electrocoagulation and chemical coagulation in sequence (EC-CC) or vice-versa (CC-EC) was examined to determine the capability of treatment in reducing the strength of the wastewater. Optimal operating parameters regarding electrolysis time, initial pH, and applied power were determined in conjunction with nutrient removal performance, electrode consumption and energy usage. Combined EC-CC treatment has been demonstrated to be economically feasible for brewery wastewater applications from an energy consumption perspective due to the efficiency of nutrient removal and the reduction of sewer discharge costs. Treatment by EC-CC at 5 W for 20 min using aluminum electrodes resulted in enhanced and consistent removal efficiencies of 26%, 74%, 76%, and 85% for chemical oxygen demand (COD), reactive phosphorous (RP), total phosphorous (TP) and total suspended solids (TSS), respectively. Energy consumption was the main contributor to operating cost. By considering potential recovered over-strength discharge fees (ODF), EC-CC treatment is economically feasible and beneficial in a brewery wastewater application. The results demonstrated the effectiveness of the CC-EC process to remove phosphorous, organics and solids from brewery wastewater at lower power supply, so that the recovered ODF cost for CC-EC at 5 W-EC is 23% higher than at 10 W-EC.

Analysis of the characteristics of Eco-Exergy-based indices and diversity indices in the Zhoushan archipelago, China.

Anthropogenic disturbance of coastal ecosystems has increased the need for comprehensive methods and indicators to assess the health status of marine ecosystems. Biotic indices are important as they indicate different ecological states. In this study, Eco-Exergy-based indices (Exergy and Structural Exergy) and diversity indices (Shannon-Wiener index and Margalef index) were applied in the seas around the Zhoushan archipelago, and correlation analysis between biotic indices and environmental factors was used to test the robustness of these indices in capturing the environment changes, aimed to provide reference in selecting the indices for assessing marine eco-environment quality. Results showed that the benthic indices of Exergy, Shannon-Wiener, and Margalef increased with the distance from the mainland. The Eco-Exergy-based indices and Margalef index were significantly, negatively correlated with dissolved inorganic nitrogen and reactive phosphate, and significantly, positively correlated with the salinity of seawater. Overall, the marine ecosystem was more stable further away from the coast, where salinity was higher, and pollutants such as nutrients in seawater were lower. In addition, biodiversity and Eco-Exergy was also higher. Generally, Eco-Exergy-based indices were observed to be good indicators for detecting the environment changes in the study area.

Sedimentary phosphorus cycling and budget in the seasonally hypoxic coastal area of Changjiang Estuary

Anthropogenic activities have greatly accelerated phosphorus (P) inputs from land to coastal seas. The increased P inputs from major rivers can cause adjacent coastal areas to experience seasonal hypoxia with the enhancing coastal eutrophication, which can subsequently increase P cycling and alter long term preservation. Analysis of sediment core measurements including SEDEX P speciation coupled with diagenetic kinetic models were performed on two cores in the coastal area under the Changjiang river plume, that experiences seasonal hypoxia. It was found that the benthic flux of dissolved reactive phosphate (DRP) in the Changjiang Estuary (CJE) was higher than that of adjacent areas of the Chinese coastal shelf. Sedimentary phosphorus transformations of Fe-bound P and organic P resulted in the in-situ formation of authigenic P (probably apatite), which was the major form of reactive P buried in the sediment. P burial efficiency (PBE) was lower than that of the oxic Chinese shelf but higher than that of other seasonally hypoxic areas in the world away from major river inputs. An exponential relationship between PBE and bottom water dissolved oxygen was developed, which suggested a positive feedback mechanism of increased hypoxia increasing P recycling, and hence intensifying eutrophication. The relatively high input of sediment including detrital P from the adjacent major river can explain many of the observed differences in P cycling from other seasonally hypoxic areas.

Assessment of Water and Sediments Pollution in Maruit Lake, Egypt

The Egyptian Mediterranean Coast has five lakes; all of them, except Lake Maruit, are directly connected to the Sea. The objective of the present study in 2016 is assessing the environmental statement of Lake Maruit (water and sediment quality). The sample from 10 monitoring points distributed along the lake in addition to 3 samples from the main drains and for water samples (temperature, salinity, pH, BOD, DO, COD, eutrophication parameters (ammonia, TSM, nitrate, nitrite, reactive phosphate , silicate, TP and TN), heavy metals and microbiological parameters in addition to Total pesticides, PCBs and PHC) while for sediment samples (Sediment Types, Organic Carbon, Organic Matter Content, Water Content, TN, TP, heavy metals and Total pesticides, PCBs and PHC) were analyzed. The results revealed that water temperature of the Lake Basins showed variations and ranged from (12.8 - 31.5 °C) while the annual average concentration of Drains 22.5 oC, Salinity of the Lake ranged between (1.84 - 6.45 Ppt), while the annual average concentration of Drains 1.69 Ppt, the distribution pattern of seasonal variations of pH values was ranged between (7.24 - 9.04), while the annual average concentration of Drains 7.923, Distribution of DO showed a considerable wide range between(0.00 - 15.84 mg/l) , while the annual average concentration of Drains 4.54 mg/l, BOD in the Lake was ranged between (9.54 - 224.25 mg/l), while the annual average concentration of Drains 76.15 mg/l. Lake Maruit was considered a major source of pollution to the Mediterranean Sea through El-Mex Bay because it receives a huge amount of polluted water from three major sources. On the other hand, the lake water at present has no metal pollution problem. The main pollution problem is due to the oxygen-consuming wastes and the plant nutrients, which had led to depletion in DO.

Zooplankton communities in a river downstream from a lake restored with hypolimnetic withdrawal

Restoring lakes with hypolimnetic withdrawal can severely threaten water quality and biocenosis downstream. The objective of this study was to evaluate the effect of lake restoration on riverine zooplankton during a period of intense hypolimnion water inflow. Zooplankton density and biomass were determined in water samples. The water samples were also analyzed to determine the following physicochemical parameters: flow rate, dissolved oxygen, hydrogen sulphide, sulphate, ammonium nitrogen, nitrate nitrogen, total phosphorous, soluble reactive phosphorus, total organic carbon, and temperature. The results of multiple regression indicated that water flow was the most significant variable and was the best predictor of total zooplankton and rotifer density. Soluble reactive phosphorous was the main predictor of copepod biomass and density. Our study showed that hypolimnetic withdrawal disturbed the natural process of planktic community transformation, which was linked to the environmental shift from lacustrine to riverine. During the study, zooplankton density and biomass were low, but not as low as when the pipeline was operating at maximum output. At present, this lake restoration method has become more sustainable, because the adverse effects of hypolimnetic withdrawal on the recipient river have been minimized and limited to several weeks.

Rice-duck co-culture integrated different fertilizers reduce P losses and Pb accumulation in subtropical China.

Double pollution with phosphorus (P) losses and potential lead (Pb) accumulation in rice fields could lead to eutrophication and crop toxicity, respectively, and affect people's health. To promote the sustainable and environmentally friendly development of agriculture, we conducted field experiments using a randomized block design to explore P losses, Pb accumulation and any potential association between P and Pb forms in rice-duck (RD) co-culture system and rice monoculture (RM) system combined with different fertilizers applied: the no fertilizer (RD and RM), chemical fertilizer (RDF and RMF), organic fertilizer (RDO and RMO), and a mixture of 70% chemical and 30% organic fertilizers (RDFO and RMFO) treatments with consistent P inputs. The results showed that RDFO had the best advantages in reducing the losses of TP (total phosphorous) (by 6.67%) and DRP (dissolved reactive phosphate) (32.72%) as well as the contents of available Pb (by 7.57%) and the accumulation of Pb in grains (26.32%) compared with RMF. RDFO also achieved the highest grain yield, reaching 10.97tha-1, and exhibited a lower soil weak-acid-extracted Pb (readily be taken up by plants) concentration than RDF and RMF. RDO resulted in greater TP leaching (increase by 10.62%) and lower DRP leaching (decrease by 36.57%) than RMF. It also exhibited the lowest concentration of weak-acid-extracted Pb and higher the concentration of grain Pb than that in other treatments. RDF reduced TP (by 5.33%) and DRP (by 16.36%) losses to a greater extent and the concentration of available and grain Pb were respectively 6.58% and 25.57% lower than RMF. Therefore, RDFO was the most recommended agricultural system for the studied region. Furthermore, different soil Pb forms were correlated with different P forms of soil and leakage and runoff water, which depended mainly on the fertilizer type and specific soil redox environment in the rice fields. The ratio of organic to inorganic fertilizer, the choice of organic fertilizer type, the assessment and timing of the detection of potential farmland pollution risks and association between different forms of P and Pb are worthy of further discussion.