Phosphorus Release Characteristics Research Articles

Spent coffee ground biochar for phosphate adsorption in water: Influence of pyrolysis temperature and iron-coating activation method

A substantial portion of the phosphorus utilized in crop and food production is dispersed into soil and water, posing a challenge to the management of eutrophication and sustainable nutrient recovery. This research focuses on the reclamation of phosphate from polluted water through affinitive adsorption on biochar derived from spent coffee grounds (SCG). SCG were subjected to pyrolysis within a N2-purged vertical furnace across a temperature range of 300–550 °C, with a 1-h holding time. The adsorption capability of SCG biochar was systematically investigated and experimental data were interpreted using Langmuir and Freundlich isotherm models. Notably, the biochar pyrolyzed at 450 °C and activated with a Fe/biochar mass ratio of 2:1 demonstrated the highest adsorption capacity (0.87 mg P/g biochar) when exposed to the highest initial phosphate concentration in the solution (15 mg P/L). Comparative analyses revealed that the removal efficiency of non-activated SCG biochar was considerably lower (5.7%) compared to the corresponding activated biochar (up to 17.3%). This highlights the significant increase in adsorption capacity facilitated by the introduction of ferric chloride. Furthermore, phosphate desorption experiments were conducted to assess the biochar's phosphorus release characteristics and stability. The results demonstrate the positive outcomes of upcycling SCG waste material as a pollutant sorbent and the potential to diminish reliance on chemical fertilizers through the recovery of Fe-phosphate-enriched SCG biochar.

Carbon, nitrogen, and phosphorus release characteristics and underlying mechanisms in fish manure from recirculating aquaculture systems under alternating aerobic-anaerobic conditions

To mitigate the adverse environmental impacts of aquaculture operations, recirculating aquaculture systems (RASs) have emerged as promising alternatives to traditional aquaculture methods. Fish manure is the primary pollutant in RASs, and oxygen fluctuations significantly influencing the release of pollutants. However, the release characteristics and underlying mechanisms of carbon (C), nitrogen (N), and phosphorus (P) during alternating aerobic-anaerobic conditions in RASs remain poorly understood. This study conducted batch incubation experiments to examine the release dynamics of C, N, and P from fish manure under simulated alternating aerobic-anaerobic conditions. Results showed that the overlying water exhibited anaerobic and reductive conditions, with both COD and TOC concentrations decreasing over time. NH4+-N levels significantly decreased from days 1–9, while NO3--N concentrations peaked on day 16. Furthermore, the alternating aerobic-anaerobic conditions significantly increased TP concentration in the overlying water. Soluble microbial byproduct-like substances in the overlying water transformed into humic acid-like substances over time. The relative abundance of Proteobacteria and Firmicutes decreased by 13.6 % and 6 %, respectively, while the relative abundance of Actinobacteria, Bacteroidota, and Chloroflexi increased by 7 %, 12.8 %, and 1.4 %, respectively. Overall, both abiotic and biotic factors influenced the release of C, N, and P from fish manure. The coupled effects of abiotic factors, specific bacterial communities, and functional genes played a critical role in the release and transformation of these elements. These findings provide new insights into the release behaviours and mechanisms of pollutants in RASs, contributing to improved environmental risk management in RASs.

Effect of Phosphate Rock Powder, Active Minerals, and Phosphorus Solubilizing Microorganisms on the Phosphorus Release Characteristics of Soils in Coal Mining Subsidence Areas

Effect of Phosphate Rock Powder, Active Minerals, and Phosphorus Solubilizing Microorganisms on the Phosphorus Release Characteristics of Soils in Coal Mining Subsidence Areas

Promoting effect and mechanism of residual feed organic matter on the formation of cyanobacterial blooms in aquaculture waters

Cyanobacterial blooms and eutrophication often occur in aquaculture waters where feeds are used. We hypothesize that residual feed organic matter (RFOM) can contribute to increased dissolved reactive phosphorus (SRP) concentrations in the water column by altering sediment phosphorus release characteristics (PRCS), including phosphorus fractions (i.e., Fe–P) and phosphorus adsorption (i.e., Qmax, EPC0), which is ultimately conducive to the formation of cyanobacteria blooms. Three types of aquaculture waters that were never feeding (NF), long-term feeding (LF), and stopped feeding (SF) for several years were studied to verify the above hypothesis. The results showed that the concentrations of SRP and chlorophyll-a in LF were significantly higher than those in SF and NF (P < 0.05). RFOM significantly affects PRCS with a power function relationship with EPC0 and a linear relationship with Qmax. Similarly, SRP in the water column was positively correlated with PRCS (i.e., Fe–P, EPC0), cyanobacterial biomass, and trophic state index (P < 0.01). This suggested that SRP may be an essential link between sediment and algal community structure. Simulation experiments further confirmed the above hypothesis, With the increase in RFOM (94.36 g/kg), PRCS (i.e., Fe–P, EPC0, and Qmax) increased significantly, which were 6.60, 282.36, and 2.47 times that of the control group, respectively. The sediment bacterial community and the partial least squares path model indicated that RFOM could regulate the SRP concentration in the water body and promote the formation of cyanobacterial blooms through PRCS, in which Firmicutes played an important role. This study revealed the driving process and mechanism of feeding behavior on the formation of cyanobacterial blooms and eutrophication in aquaculture waters, which provided a basis for the health management and cleaning strategy of aquaculture waters.

Cyanobacterial organic matter (COM) positive feedback aggravates lake eutrophication by changing the phosphorus release characteristics of sediments

Phosphorus is a key nutrient that causes eutrophication in lakes. Our investigation of 11 eutrophic lakes found that the concentrations of soluble reactive phosphorus (SRP) in the water column and EPC0 in sediments decreased with aggravated eutrophication. There was a significant negative correlation between the SRP concentrations and eutrophication parameters such as chlorophyll a (Chl-a), total phosphorus (TP) and algal biomass (P < 0.001). In addition, SRP concentrations were significantly affected by EPC0 (P < 0.001), while EPC0 was significantly affected by the content of cyanobacterial organic matter (COM) in sediments (P < 0.001). Based on these findings, we hypothesized that COM can alter the phosphorus release characteristics of sediments, including the phosphorus adsorption parameters of sediment (PAPS) and the phosphorus release rate of sediment (PRRS), thereby stabilizing SRP concentrations at lower levels and rapidly replenishing them when depleted by phytoplankton, which in turn benefits cyanobacteria due to their low SRP adaptation strategies. Simulation experiments were conducted to confirm this hypothesis by adding higher plant OM and COM to sediments. The results showed that all types of OM could significantly increase the maximum phosphorus adsorption capacity (Qmax), but only COM could reduce sediment EPC0 and promote PRRS (P < 0.001). Changes in these parameters (i.e., Qmax, EPC0, and PRRS) resulted in a larger SRP adsorption quantity and faster SRP release rate at low SRP concentrations. This promotes the competitive edge of cyanobacteria due to they have a higher affinity for phosphorus than other algae. As an important component of cyanobacteria, EPS can change the phosphorus release characteristics (i.e., PAPS and PRRS) by reducing sediment particle size and increasing sediment surface functional groups. This study revealed the positive feedback effect of COM accumulation in sediments on lake eutrophication from the perspective of phosphorus release characteristics of sediments, which provides a basic reference for the risk assessment of lake eutrophication.

Nitrogen and Phosphorus Release Characteristics of Pipeline Sediments on Entering Different Water Bodies

Differences in the physical and chemical properties of reclaimed water (RW) and natural surface water (SW) lead to further differences in nitrogen and phosphorus release when pipeline sediments enter these water bodies. The release kinetics of nitrogen and phosphorus from pipe sediments with different particle sizes have been investigated. The results demonstrated that both SW and RW had a pH buffering effect after sediment addition, and the final pH (approximately 8.1) of RW was lower. The release of total phosphorus (TP) and ammonia nitrogen (NH4+-N) fitted the first-order kinetic model in which the release of TP reached equilibrium. TP release was inhibited in both SW and RW, with RW exhibiting the lowest (by a factor of 1.23~2.44) release (0.002 mg/g). The release of NH4+-N was promoted in both SW and RW; the maximum release in RW was 0.0188 mg/g. The amounts of NH4+-N released in SW and RW were 1.02–1.40 and 1.30–1.80 times that of the control group (CG), respectively. The percentage of TP and NH4+-N release in the three groups was highest in 75–154 μm pipe sediment, reaching 34.53% and 43.51% in SW and RW, respectively. These results can assist in the development of water quality evolution models for specific urban scenarios and provide important guidance for the precise regulation of water recharge quality during and after rainfall.

Release characteristics of phosphate from ball-milled biochar and its potential effects on plant growth

Ball-milled biochar could potentially supply phosphorus, an essential element for plant growth. To realize resource reuse and phosphorus recovery, three feedstocks (rice straw, distillers grains, and Eupatorium adenophorum) were used to prepare ball-milled biochar to evaluate its release characteristics of phosphorus and potential effects on germination and growth. The results showed that the phosphate release performance of ball-milled distillers grains biochar (DM) at 300 and 600 °C was better than that of other biochars ball-milled for 12 h. The DM prepared at 600 °C and incubated for 12 (DM-12) or 24 h (DM-24) had the best phosphate release capacity. The solution with pH 3.0 was beneficial to the release of phosphate from DM-12. The pseudo-second-order model could better fit the phosphate release of DM-12. A germination and seedling growth experiment suggested that adding 2.5 wt% DM-12 was beneficial to the height of mung beans. This study shows that DM-12 can be used as a slow-release fertilizer for the growth of mung beans, which provides a new way for resource utilization of distillers grains and phosphorus-rich biochar.

Characteristics of Phosphorus Adsorption and Release in Different Types of Sediments

Taking different types of sediments as the research object, this research studied the adsorption and release characteristics of phosphorus under different conditions of different temperatures, coexisting heavy metal ion system, organic matter content and sediment particle size. Through used correlation analysis and principal component analysis, it discussed the influence of various factors on the adsorption and release of phosphorus in sediments. The results show that the adsorption of phosphorus by five different types of sediments from different sources reached saturation equilibrium in about 10 hours, and the increasing rates of 0 ℃, 15 ℃ and 30 ℃ are 17.5% ~ 23.7% and 18.2% ~ 38.3%, respectively. The addition of coexisting heavy metal ion solution accelerated the adsorption of phosphorus in the sediment and reduced the total amount of phosphorus adsorption, that is, heavy metal ions inhibited the adsorption of phosphorus in the sediment; the presence of organic matter in the sediment would reduce its adsorption of phosphorus , Taihu farm and wetland sampling points have the largest sediment organic matter content. Compared with the other three points, the adsorption of phosphorus of these two points accounted for 20.6% and 22.1%; the adsorption and release of phosphorus by sediment increased with the decrease of particle size. The maximum release rate was 5.216mg/kg-1·h-1. The result of principal component analysis shows that the order of influence on the adsorption and release of phosphorus by sediments is temperature&gt; disturbance&gt; organic matter content&gt; heavy metal ion influence&gt; particle size of sediments.

The Effects of Sugarcane-Derived Biochar on Phosphorus Release Characteristics in a Calcareous Soil

The main aim of this study was to investigate how phosphorous (P) release would change after the addition of combined sinfluence upon soil properties sugarcane residues – derived biochar (B) and P fertilizer in a calcareous clay loam soil after 7 and 120 days of incubation. Biochar was produced from sugarcane residues (S) at the temperature of 400 °C under limited oxygen condition. A full-factorial experiment was performed in a completely randomized design to evaluate the effects of amendment (without amendment, 1% S, and 1% B) and P (0 and 50 mg kg−1) on availability and P release characteristics over incubation period (7 and 120 days). After incubation, the kinetics of P release in soils was determined by successive extraction with Olsen solution in a period of 2 to 768 h at 25 ± 1 °C. Results showed that the difference between cumulative P release in soil treated with S and B, at two incubation times, was not significant (P > 0.05). At both times, the cumulative P release increased by 5 up to 23% as influenced by amendments and P fertilizer. Difference between treatments at 7 and 120 days of incubation was not significant (P > 0.05). The lowest and highest initial amount of P release was found in control soil (14.62 mg kg−1 h−1) and soil treated with P + B (38.26 mg kg−1 h−1), respectively. The maximum and minimum rates of P release were in control soil (0.328 (mg kg−1)−1) and soil treated with P + B (0.203 (mg kg−1)−1), respectively. Also, the lowest and highest initial release rates were observed in control soil (4.79) and soil treated with P + B (7.76), respectively. Biochar addition to soil treated with P increased initial amount of P release and initial release rate of P. Therefore, addition of sugarcane residues –derived biochar to soil treated with P fertilizer can increase P availability in similar calcareous soils.

Remobilization mechanism and release characteristics of phosphorus in saline sediments from the Pearl River Estuary (PRE), South China, based on high-resolution measurements

The internal loading of phosphorus (P) is commonly considered an essential factor contributing to eutrophication in freshwater bodies. However, investigation of the lability and remobilization characteristics of P in estuarine saline sediments has been limited. In this study, a sequential chemical extraction procedure and high-resolution measurement using the diffusive gradients in thin film (DGT) technique were employed to explore the lability, potential remobilization mechanism and release characteristics of sediment P in the Pearl River Estuary (PRE), South China. The P accumulated significantly in sediments along the west coast of the PRE due to the combined effects of terrestrial P inputs and specific hydrological conditions. The geochemical fractions of sediment P followed the order of organic P (Org-P) (mean: 58.6%) > iron-bound P (Fe-P) (23.4%) > calcium-bound P (Ca-P) (17.4%) > loosely bound P (LS-P) (0.63%). Synchronous vertical variations in DGT-labile Fe and P in the upper and middle parts of the sediment profiles confirmed that Fe-coupled P mobilization occurred in saline sediments. In contrast, sulfate reduction in bottom sediments supposed to decouple the Fe-P cycling relationship. Additionally, the formation of an “iron curtain” (Fe oxyhydroxides) in the oxic surface sediments efficiently prevented upward diffusion of P, leading to relatively low effluxes of P (0.098–6.59 ng cm−2 d−1) across the sediment-water interface.

Numerical Simulation of Phosphorus Release with Sediment Suspension under Hydrodynamic Condition in Mochou Lake, China

Phosphorus is a major cause of lake eutrophication. Understanding the characteristics regarding the release of phosphorus from sediments under hydrodynamic conditions is critical for the regulation of lake water quality. In this work, the effects of sediment suspension on the release characteristics of phosphorus from sediment were investigated under different hydrodynamic conditions. The experimental results showed that in the experimental process, the phosphorus was at first released quickly into the overlying water but then slowed down. Furthermore, the process of dissolved phosphorus (DP) release under hydrodynamic conditions with and without sediment suspension was simulated using a lattice Boltzmann method. The simulation showed satisfying results.

Distribution and Release Characteristics of Phosphorus in a Reservoir in Southwest China

Dam construction changes the nutrient transport of a river system. Phosphorus is an important fundamental material in the global biochemical cycle and is always a limiting factor in the primary productivity of reservoirs. Extending the study of phosphorus in reservoirs is necessary given the dam construction in southwest China. Zipingpu Reservoir was chosen as the research site in this study. The form and distribution of phosphorus in the reservoir’s surface sediments and overlying water were analyzed. The results showed that overall, the total phosphorus (TP) content of surface sediments in the Zipingpu Reservoir decreased from the tail to the front of the dam. The TP content ranged from 682.39 to 1609.06 mg/kg, with an average value of 1121.08 mg/kg. The TP content at some sampling points was affected by exogenous input. Inorganic phosphorus (IP) was the main form of phosphorus in surface sediments and had a proportion of 89.38%. Among the forms of IP, the content of Ca-P was larger than that of O-P; Ex-P, Fe-P, and Al-P had the lowest contents. Particulate phosphorus (PP) was the main form of phosphorus in the overlying water of the Zipingpu Reservoir and was strongly affected by hydrodynamic conditions. The content of total dissolved phosphorus (TDP) in the overlying water was relatively low. To further understand the risk of phosphorus release in the surface sediments in the reservoir, the rate and flux of phosphorus exchange at the sediment-overlying water interface were investigated through laboratory experiments. The results showed that both water temperature and pH significantly affected the sediment release rate, but the influence of water temperature was more significant. Acidic and alkaline conditions were conducive to the release of phosphorus from sediment, while a neutral environment was not. The release rate significantly increased with increasing water temperature, and a positive linear relationship was found between these two parameters. The sediment exhibited absorption characteristics when the water temperature was extremely low and exhibited releasing characteristics at a high temperature. These results could provide a theoretical basis for the management and protection of reservoir water environments.

三峡消落带落羽杉人工幼林叶片分解及磷释放特征

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡消落带落羽杉人工幼林叶片分解及磷释放特征 DOI: 10.5846/stxb201808091698 作者: 作者单位: 三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715 作者简介: 通讯作者: 中图分类号: 基金项目: 重庆市林业重点科技攻关项目（渝林科研2016-8，2019-16）；国家科技部国际合作专项（2015DFA90900）；中央财政林业科技推广示范项目（渝林科推2014-10） Foliar decomposition and phosphorus release in a Taxodium distichum young forest stand rehabilitated in the hydro-fluctuation belt of the Three Gorges Reservoir Author: Affiliation: SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究三峡消落带人工重建植被落羽杉（Taxodium distichum）幼林叶片在不同水文条件下的分解特征及其对土壤-水体磷的贡献潜力，本实验在控制条件下，模拟三峡库区消落带土壤水分变化设置了常规生长水分条件（CK）、轻度干旱水分胁迫（T1）、潮湿（T2）、2 cm水淹（T3）、10 cm水淹（T4）5个不同处理，研究落羽杉叶片分解及磷释放特征。研究结果表明：（1）在整个试验期间（90 d），T3、T4两个水淹处理的叶片失重率分别达51%（T3）和55%（T4），显著高于CK、T1、T2三个未水淹处理；（2）未分解残留叶片中的全磷含量在CK、T1、T2三个未水淹的处理组呈现增加趋势，而水淹处理（T3、T4）呈减少趋势；（3）土壤全磷含量在试验过程中呈现波动性变化特征，但至试验结束时，各处理中土壤全磷含量与CK相比均无显著差异；（4）T3、T4处理中叶片添加显著增加了上覆水体中总磷含量，试验过程中呈现出在分解初期迅速上升，在分解10 d时达到峰值，之后逐渐降低并趋于稳定，但试验结束时仍显著较高，分别是对应无叶片组的17.15倍（T3）和5.81倍（T4）。这些结果说明水淹通过促进落羽杉叶片的分解从而增加上覆水体中磷的含量，因此有必要在水淹前对消落带的落羽杉幼林叶片进行适时采收，以尽可能减少其对库区水体的磷负荷。 Abstract:To explore traits related to leaf decomposition and the potential contribution of the phosphorus of the leaves of Taxodium distichum to the soil-water system in the fluctuation zone of the Three Gorges Reservoir, an indoor experiment was conducted upon simulation of the water change of the hydro-fluctuation belt in the reservoir. Five different kinds of water treatments were applied to investigate leaf decomposition processes of T. distichum and phosphorus release characteristics. Five water treatments included normal growth water condition (CK), light drought water stress (T1), water saturation (T2), 2 cm flooding (T3), and 10 cm flooding (T4). The results showed that:1) During the entire experiment period (90 d), the rate of leaf weight loss of the two flooding groups reached 51% (T3) and 55% (T4), which were significantly higher than that of the three unflooded treatment groups of CK, T1, and T2; 2) The total phosphorus content in leaves increased in the CK, T1, and T2 treatment groups, but decreased in the flooding treatments (T3 and T4); 3) The total phosphorus content of the soil showed fluctuation characteristics during the experiment period, but at the end of experiment there was no significant difference in soil total phosphorus content between the treatment groups and the CK group; 4) During the experiment period, total phosphorus content of the overlying water of the T3 and T4 treatment groups with addition of leaves increased significantly compared with that of the respective treatment groups without addition of leaves and showed a rapid increase in the initial decomposition rate followed by a gradual decrease and finally a stable state. The peak value of leaf decomposition was observed on the 10th day, after which leaf decomposition decreased. However, at end of the experiment the total phosphorus content of T3 and T4 treatment groups with addition of leaves was still significantly higher than that of the respective treatment groups without addition of leaves, reaching 17.15 (T3) and 5.81 (T4) times higher, respectively. These results indicated that:water flooding can promote the decomposition of the leaves of the T. distichum; the decomposition of leaves under different water conditions did not significantly affect the phosphorus content in the soil; and the decomposition of the leaves of the T. distichum during flooding may increase the phosphorus content in the water. Therefore, it is necessary to collect the leaves of the T. distichum in the hydro-fluctuation belt in a timely manner in order to reduce the phosphorus load of the water body in the reservoir area as much as possible. 参考文献 相似文献 引证文献

Variation laws and release characteristics of phosphorus on surface sediment of Dongting Lake.

The variation trend and growth rate of P were analyzed by the concentration of the phosphorus fraction on surface sediment of Dongting Lake from 2012 to 2016, to reveal the cumulative effect of P in the actual environment. Meanwhile, the adsorption kinetics and adsorption isotherm were employed to examine the P-release possibility of sediment, which predicts the yearly released sediment phosphorus in Dongting Lake. The actual growth rate of TP (Total Phosphorus) is 53mg·(kg·year)-1 in East Dongting Lake, 39mg·(kg·year)-1 in South Dongting Lake, and 29mg·(kg·year)-1 in West Dongting Lake, while the sum of the phosphorus fraction growth rates has little difference from the rate of TP in sediments of the three areas of Dongting Lake. Furthermore, the Elovich model and the Langmuir crossover-type equations are established to present the adsorption characteristic of sediment in Dongting Lake; the result shows that the sediments play a source role for phosphorus in East and South Dongting Lake from zero equilibrium phosphorus concentration (EPC0) in the present situation, but an adsorption effect on TP is shown in West Dongting Lake. When the conditions of environment change are ignored, the maximum P-sorption level in sediments of East Dongting Lake will reach in 2040 according to the actual growth rate of sediments, while that in West Dongting Lake and South Dongting Lake will be in 2046 and 2061, respectively.

Vertical distribution and release characteristics of phosphorus forms in the sediments from the river inflow area of Dianchi Lake, China

Columnar sediment samples were collected from five representative river inflow areas of Dianchi Lake, China. The vertical distribution of each form of P were tested. Results showed that the concentration of TP in the sediments from areas A, B, C, D and E in the order of D > B > A > C > E, and the average concentration of D, B, A, C and E were 2991, 2064, 1308, 879, and 759 mg•kg−1, respectively. The concentration of Ex-P, Fe/Al-P, Ca-P and Org-P all decreased with increasing depth. The release of Ex-P was significantly related to TP whereas the Fe/Al-P was not significantly related to TP in the samples from areas polluted by domestic sewage. However, the release of Ex-P and Fe/Al-P were both significantly related to TP in the samples from areas polluted by phosphate mining and phosphate fertilizer application. The results of equilibrium P concentration (EPC0) analysis showed that P in the sediments of areas A, D and E were the source of P in Dianchi Lake, and the P in the sediments of areas B and C were in relative equilibrium with the overlying water.

Simulation on phosphorus release characteristics of Poyang Lake sediments under variable water levels and velocities

Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake varied. Water level dropped, the velocity decreased and water exchange time lengthened, which changed the release of phosphorous from sediments. In order to investigate how the hydrodynamic factors influence the release of phosphorous from sediments, we used a two-way annular flume device to simulate the release characteristics of phosphorous from sediments under variable water levels and velocities. We found that both water level rising and velocity increasing could enhance the disturbance intensity to sediments, which caused the increase of suspended solids (SS) concentration, total phosphorus (TP) concentration in the overlying water, and the ability that phosphorus released to overlying water from sediments enhanced as well: when overlying water velocity maintained 0.3 m/s, SS concentration increased to 4035.85 mg/L at the water level 25 cm which was about 25 times compared to the minimum value and TP concentration in the overlying water also reached the maximum value at the water level 25 cm which was 1.2 times that of the value at 10 cm; when water level maintained 15 cm, SS concentration increased to 4363.35 mg/L at the velocity of 0.5 m/s which was about 28 times compared to the value of 0 m/s, and TP concentration in the overlying water increased from 0.11 mg/L to 0.44 mg/L. When the water level maintained 15 cm, the phosphorous release rate reached the maximum value of 4.86 mg/(md) at 0.4 m/s. The concentration of total dissolved phosphorous (TDP) and soluble reactive phosphate (SRP) both in overlying water and sediment-water interface were negatively correlated with pH. Using the parabolic equation, the optimum water level at a velocity of 0.3 m/s was calculated to be 0.57 cm, and the optimum velocity at water level of 15 cm was found to be 0.2 m/s.

Distribution patterns and dynamics of phosphorus forms in the overlying water and sediment of Dongting Lake

Abstract Dongting Lake is a typical shallow lake in the lower Yangtze region and is the second largest freshwater lake in China. The distribution, speciation, and sediment release characteristics of phosphorus (P) were investigated by analyzing sediment and water samples collected during high and low flow periods. The average concentration (range) of total phosphorus (TP) in the water was 0.05 mg L − 1 (0.02 ~ 0.09 mg L − 1 ), while the value in sediment was 703 mg kg − 1 (466 ~ 869 mg kg − 1 ). The concentrations of TP and different P forms decreased as depth increased. Inorganic phosphorus was the dominant form of P, accounting for 72% of TP. The bioavailable P was a relatively large portion of TP, indicating a high risk of P release to overlying water. The Langmuir equation can well describe the P isotherm adsorption characteristics in sediment. The amount of P desorption from sediment tended to increase with increasing concentrations of adsorbed P.

Phosphorus release characteristics of sediments in Erhai Lake and their impact on water quality

In view of the problems of high P concentration in the sediments and low P concentration in the overlying waters of Erhai Lake (EH), an indoor static incubation experiment was performed to determine the P release characteristics of sediments at different depths. The differences in the P forms of the sediments before and after the incubation experiment were compared, and the impact of such forms on the characteristics of the P release of sediments at different depths and that of P release on the water quality of EH were also investigated. Results were as follows: (1) Dissolved organic P (DOP) is the main form of P released at the sediment–water interface of EH, which is approximately six times that of soluble reactive P (SRP), which indicates that the DOP release of sediments may have a more important impact on P composition and the content of the overlying water of EH than SRP. The release flux of the DOP of sediments at the surface layer is higher than that at the bottom layer. The vertical distribution of the release flux of SRP is characterized by an increase at the surface layer and a decline at the lower layer. (2) Different P release potentials exist for different forms of P in the sediments of EH. Among the different P forms, the loosely absorbed inorganic P (NH4Cl-rp) is the main source of SRP that is released from the sediments into the overlying waters. (3) The release flux of total P (TP) at the sediment–water interface of EH amounts to 114.2 t/a, which accounts for 87.2 % of the total external P input in the lake. Although the amount of the P release of sediments under indoor static simulation conditions is higher than that under real conditions, the trend of the P release of the sediments of EH is accurate. According to this result, the contribution of the sediment P release to the TP concentration of the overlying water is up to 31 %, reaching a concentration of 9.4 µg/L. The annual P release of the sediments of EH influences the P concentration in the overlying water. The contribution of the sediment P release to the TP concentration of overlying water in the northern part of EH is obviously higher than to that of the other parts. The water quality of this kind of lake can be improved by controlling the P release of sediments, particularly the release of OP.

Selective release of phosphorus and nitrogen from waste activated sludge with combined thermal and alkali treatment

Selective release characteristics of phosphorus and nitrogen from waste activated sludge (WAS) were investigated during combined thermal and alkali treatment. Alkali (0.001–1.0N NaOH) treatment and combined thermal-alkali treatment were applied to WAS for releasing total P(T-P) and total nitrogen(T-N). Combined thermal-alkali treatment released 94%, 76%, and 49% of T-P, T-N, and COD, respectively. Release rate was positively associated with NaOH concentration, while temperature gave insignificant effect. The ratio of T-N and COD to T-P that released with alkali treatment ranged 0.74–0.80 and 0.39–0.50, respectively, while combined thermal-alkali treatment gave 0.60–0.90 and 0.20–0.60, respectively. Selective release of T-P and T-N was negatively associated with NaOH. High NaOH concentration created cavities on the surface of WAS, and these cavities accelerated the release rate, but reduced selectivity. Selective release of P and N from sludge has a beneficial effect on nutrient recovery with crystallization processes and it can also enhance methane production.

Distribution and release characteristics of phosphorus in water-sediment interface of Lake Dianchi

The distribution status and release characteristics of phosphorus were investigated by studying the lease kinetics characteristics and phosphorus forms from thirty-five sediment samples collected in Lake Dianchi. Results indicated that: The rank order of phosphorus contents in the surface sediment of Lake Dianchi was organic P( OP)( 1482. 49 ± 1156. 82 mg / kg) calcium-bound P( Ca-P)( 865. 54 ± 558. 40 mg / kg) metal oxide-bound P( Al-P)( 463. 77 ± 662. 18 mg / kg) residual P( Res-P)( 218. 52 ±83. 11 mg / kg) Fe-bound P( Fe-P)( 128. 13 ± 101. 56 mg / kg) weakly absorded P( NH4Cl-P)( 2. 26 ± 3. 05 mg / kg); The amount of total phosphorus in overlying water exceed V class in Caohai and between Class Ⅳ and Class Ⅴ in other sections. The amount of particulate P( PP) is the highest among total phosphorus( TP); The process of phosphate release from the surface sediment to the water in Lake Dianchi mainly occurred in the first 8 h and the kinetics were divided into the rapid-stage and the slowstage. The rank order of mean values of maximal phosphorus adsorption rate( Vmax),maximal phosphours adsorption capacities( Qmax),the release potential of sedimentary phosphorus( IDE-P) were Caohai northern coast southern coast lake center;From the correlation parameters,phosphorus release can be inferred to obtain the contribution degree of different forms of phosphorus on release potential of phosphorus in the sediments of Lake Dianchi. Therefore,the evaluation of sediment phosphorus releaserisk should not be only limited to the analyse of the basic physical and chemical properties. Great attention should be paid to the contents of different forms of phosphorus content and their proportions of total phosphorus.