The addition of FeOOH binds phosphate in organic matter-rich sediments

Due to climate change and anthropogenic nutrients’ runoff into freshwater or shallow lakes, eutrophication caused by phosphorus (P) can be seen in the frequent occurrence of cyanobacterial blooms and excessive growth of macrophytes. Subsequently, decomposition of cyanobacterial bloom biomass (CBB) and macrophytes leads to massive autochthonous organic matter (OM) and creates hypoxia in bodies of water. In this study, we investigated the effects of OM and iron on phosphorus release from lake sediments under anaerobic conditions. As with CBB, the addition of cellulose also enhanced P release from sediments during microcosm experiments, while total phosphorus (TP) concentration in the overlying water displayed an inverse relationship to cellulose amendment, with high TP concentration (0.41?±?0.07?mg?L^?1) observed in the treatment of less cellulose amendment (1?g of cellulose). In addition, P release from OM-rich sediments was effectively inhibited when amorphous FeOOH was added to the microcosms. P release was inhibited by 66–92% when the weight ratio between total Fe and total P in sediments varied from 18 to 60. Thus, iron treatment was useful to inhibit P release from OM-rich sediments, and could alleviate eutrophication problems.     

Fraction distribution and migration of heavy metals in mangrove-sediment system under sulphur and phosphorus amendment

In this study, mangrove seedlings (Kandelia obovata (S. L.)) were cultivated in rhizo-boxes, which contain sediments collected from natural mangrove forest and modified with different rates of sulphate and phosphate. The fraction distributions of Zn, Cd, Cu, Ni and Pb in rhizosphere and non-rhizosphere sediments were studied by using a sequential extraction method. Metal concentrations in plant tissues and iron plaque on root surface were also determined to reveal migration variation of heavy metals in the plant-sediment system. The results showed that the activities of K. obovata roots enhance the reducible metals while reducing acid-extractable and oxidisable metals; sulphur amendment benefits the combination of metal ions with S^2– and therefore reduces the bioavailability of metal pollutants; addition of sulphur also improves the content of iron plaque on the root surface, which plays an important role in metal accumulation by K. obovata root tissue; the addition of sulphur markedly reduces the concentration of Cd in roots, but significantly enhanced the concentrations of Cu, Zn, Ni and Pb in roots. The results indicate that sulphur and phosphorus content in mangrove sediment, and the growth of mangrove plant can significantly influence the migration of heavy metals in the mangrove wetland ecosystem.     

零价铁原位控制底泥磷释放及联合磁性分离除磷技术

水体富营养化是常见的世界性水体生态系统障碍问题之一,给人类生产、生活造成了广泛而严重的影响,同时也是造成世界各地结构性缺水的重要原因之一。底泥磷释放是水体富营养化的重要原因,但目前常用的控磷技术往往成本较高,内源磷再释放风险仍然较大。该研究按铁-泥质量比1.00%、3.33%、5.00%、10.00%,分别向富磷底泥投加的铁粉来模拟零价铁控磷过程,通过分析3、7、14、21、28、35d内底泥磷形态的变化趋势,研究零价铁控磷过程及磁性分离除磷技术的应用前景。结果表明:底泥中水溶性磷、弱结合态磷是水体磷元素的主要来源,零价铁对底泥中高生物活性的弱吸附态磷(NH4Cl-P)去除率最高可达75%,对水溶性磷的去除率可达90%以上,向富磷底泥投加零价铁能够原位富集、降低内源磷生物有效性,阻断底泥向水体释磷的过程;零价铁原位控制底泥磷释放主要依赖于零价铁氧化形成的铁离子和铁氧化物与磷酸根的沉淀和共沉淀过程,加入零价铁后水溶性磷和弱结合态磷主要向铁结合态(Fe-P)转化,联合外加磁场后大部分可随铁粉拔出,最终达到安全高效地去除水体和底泥表层中高生物有效性磷的目的。该方法可以有效解决挖掘清淤、疏浚等控磷方法高成本、易反复的问题,为高效原位治理水体富营养化,保障湖泊、水库生态环境安全提供有价值的技术方法。     

滇池典型区域磷与铁的形态分布规律

通过调查滇池三个湖湾不同深度水层磷与铁的形态分布,研究三个湖湾内源磷的释放规律,结果表明,在海埂湾间隙水中,磷的释放强度远高于另外两个湖湾,根据水体中各种形态磷和铁的关系,推测出在这三个湖湾中,铁结合态磷是湖水悬浮物和沉积物中一种重要的可释放磷。     

Sulphur compounds—their environmental aspect and their elimination from waste water

The sulphur content of domestic waste water is similar to its phosphorus and nitrogen content. In conventional treatment processes sulphur compounds are converted to sulphate, thus all reaching the recipients and the oceans. In the aquatic metabolic cycle sulphate then acts as a catalyst towards anaerobiosis. Therefore, besides its efforts for removal of other nutrients, waste water technology should look for possibilities of minimizing the discharge of sulphurous effluents into the water course. Here, a new treatment process for sulphur elimination is introduced, the Root Zone method.     

蔬菜地土壤磷提取及模拟径流中磷素潜在流失的影响

蔬菜地磷素流失是一种典型农业非点源污染类型。通过观测地表径流中溶解态反应磷(DRP)、生物可利用磷(BAP)可以监测土壤磷素流失程度。受到各种客观条件的限制,这两个指标比较难于获取,而土壤中的总磷(TP)、Olsen(OP)、Mehlich-1(M-1P)和水溶性磷(Pw)可以通过常规分析手段获取。本文选取27个典型蔬菜样地,分析测定各样地土壤中的总磷(TP)、Olsen(OP)、Mehlich-1(M-1P)和水溶性磷(Pw)四个磷提取变量,采用了经典方法计算土壤磷流失潜能指标——磷吸持饱和度(DPS)。同时采用模拟径流实验得出典型蔬菜样地地表径流样中溶解态反应磷(DRP)、生物可利用磷(BAP)。结果表明:M-1P、Pw与DPS呈极显著正相关,相关系数分别达到了0.85和0.74(p<0.01);而M-1P、Pw与DRP浓度相关系数(r2=0.843和0.786,p<0.01)大于TP、OP与DRP浓度的相关系数(r2=0.554和0.722,p<0.01)。结论认为,通过测定M-1P、Pw和计算DPS能比较准确、便捷地预测土壤径流磷素流失风险程度。     

Impacts of mussel dredging on sediment phosphorus dynamics in a eutrophic Danish fjord

Effects of mussel dredging on sediment metabolism (oxygen uptake and sulfate reduction rates) and phosphorus dynamics (flux across sediment-water interface and sequential extraction) were examined in Limfjorden (Denmark) during spring (May) and summer (August). Sediment samples were taken during mussel dredging and in addition an experimental simulation of the dredging was performed to investigate short-term changes in phosphorus (P) dynamics. Iron-bound P was reduced by up to 2/3 in the surface layer in the dredging track (from 31 to 8?mmol?P?m^?2), whereas the dissolved P-pools and less reactive particulate pools were not affected by dredging. Sediment oxygen consumption was enhanced immediately after dredging, but returned to the initial level after 4 days (20–40?mmol?m^?2?d^?1). The enhanced consumption was attributed to reoxidation of reduced compounds released during dredging. Sulfate reduction rates were high in the area (13–15?mmol?m^?2?d^?1) and sulfides competed with P for oxidized iron resulting in low iron-bound pools in the area (<4% of total P pools). Sulfate reduction rates were stimulated by the resuspension of sediments, especially in August, where a subsurface maximum was found, possibly due to a mixing of labile organic matter into these layers. In contrast sulfate reduction rates were reduced in the dredging track due to removal of labile organic matter from the surface layers. The loss of P during dredging was to some extent counteracted by regeneration of iron-bound P pools in the surface layers. The release of P due to mussel dredging was estimated to be in the same order of magnitude as the annual loading from the catchments and point sources to Limfjorden.     

附生假单胞菌存在下不同光照时间对铜绿微囊藻生长与磷代谢的影响

通过设置8/16、12/12、16/8不同光暗比,分析了附生细菌存在下不同光照时间对铜绿微囊藻(M icrocystis aeruginosa)生长及其与附生假单胞菌(Pseudom onassp.)磷代谢之间关系的影响。结果表明:光照时间越长,铜绿微囊藻生长越快,16 h光照下的比增长速率为8 h光照下的1.6倍。铜绿微囊藻的快速生长促进了附生细菌中磷的释放;藻细胞增殖越快,附生细菌释放的磷越多。铜绿微囊藻对数生长期末,8、12、16 h光照下附生细菌磷含量分别降至对数生长初期的87.8%、78.6%和64.9%。铜绿微囊藻对附生细菌磷释放的促进作用是由藻细胞生长对磷的消耗再吸收导致的。     

根系分泌物及其在植物营养中的作用

论述了根系分泌物的种类和影响因素，根系分泌物在植物营养中的调节作用、异种克生作用，根系分泌物与根际微生物的相互作用。在铁胁迫条件下，许多高等植物都能产生一系列生理和形态方面的适应性反应，禾本科植物通过根际特定分泌物——麦根酸类物质来自动调节其体内的铁营养状况；在磷胁迫条件下，根系分泌的低分子有机酸种类主要有柠檬酸、草酸、酒石酸和苹果酸，它们在植物根际的富集能明显促进土壤中磷的释放，提高作物对磷的吸收，缓解植物的磷胁迫；在锌胁迫条件下，双子叶植物的根系分泌物对锌的活化作用不明显，而禾本科植物的根系分泌物可以活化石灰性土壤中难溶性锌。     

Species diversity and leaf functional traits of understory vegetation one year after severe burning北大核心CSCD

以北京油松(Pinus tabuliformis)人工林为研究对象,采用独立样本T检验、冗余分析等方法,分析重度火烧1年后林下植被(灌木层和草本层)的物种多样性、叶功能性状及其与土壤因子的关系.结果显示:(1)与对照样地相比,重度火烧后灌木层物种丰富度指数极显著降低(P <0.01),但Shannon指数、Simpson指数以及Pielou指数虽呈下降趋势但未达显著水平(P> 0.05);草本层除Pielou指数外,各物种多样性指数均显著增加(P <0.05).(2)重度火烧样地灌木层和草本层的叶厚度(LT)、叶干物质含量(LDMC)、叶碳含量(LCC)、叶磷含量(LPC)均高于对照样地,而比叶面积(SLA)、叶氮含量(LNC)、叶片氮磷比(N:P)、叶绿素含量(CHL)低于对照样地,除灌木层LPC和N:P及草本层SLA、LCC和LPC外,其他各叶功能性状在火烧与对照间差异均达显著水平.对于不同生活型而言,对照样地的LDMC、LNC、LCC、CHL存在显著差异,而在重度火烧后差异不显著;LT、SLA在重度火烧和对照样地上均呈现显著差异;而LPC、N:P在重度火烧与对照样地上均无显著差异.(3)重度火烧后1年,灌木层和草本层的叶功能性状均仅与土壤含水率、容重和非毛管孔隙度密切相关.本研究表明在油松人工林重度火烧后1年,灌木层物种多样性降低,而草本层物种多样性增加,灌草层的各叶功能性状主要受土壤物理性质的影响呈现不同的变化规律.(图4参45)     

微生物作用对太湖沉积物磷释放影响的模拟实验研究

以太湖沉积物为研究对象,通过沉积物-湖水体系的好氧厌氧连续模拟实验,研究添加和不添加抑菌剂条件下该体系对磷的释放和积聚的影响,以及微生物作用下内源磷的释放过程.结果表明:好氧环境下,微生物作用有助于磷的积聚;而在厌氧环境下,微生物作用强化了磷的释放.沉积物磷形态的分析结果表明微生物作用下,铁结合态的磷更容易释放出来.     

鄱阳湖沉积物中磷吸附释放特性及影响因素研究

沉积物是氮磷营养盐的主要蓄积库,它不仅是外来污染物的归宿地,同时其自身营养盐的释放也可对水环境产生重大影响。针对鄱阳湖存在的沉积物磷释放问题,关键环境因子对基质磷吸附的影响规律进行了探讨。通过控制在不同环境因素条件下,上覆水中磷的变化规律探讨,阐明磷在上覆水-底泥界面迁移转化的规律和环境因素对迁移转化过程的影响。研究结果表明,吸附初始阶段,两者含量相差较大,起始吸附速率很高;随着反应时间的推进,两者含量差随之减小;当吸附时间达到30 min时,此时上覆水的平衡质量浓度为8.648 mg·L^-1,两者含量达成平衡。由磷的吸附等温试验同样可看出,随着平衡质量浓度逐渐增加,土壤吸磷量刚开始增加较快,随后增加趋势逐渐减缓直至磷饱和。pH越小,上覆水质量浓度越低,沉积物对磷的吸附作用越强;pH越大,上覆水中TP质量浓度越大,强碱条件下,TP吸收量剧减。在好氧条件下,沉积物对磷的吸附远远高于厌氧条件下沉积物的吸附。好氧条件下,反应在4 h内,沉积物对磷的吸附速率最高,随后吸附量很小直至逐渐饱和。厌氧条件下,吸附作用不明显;当反应时间达到24 h后,上覆水磷质量浓度保持不变,此时沉积物磷吸附达到饱和。高溶解氧水平对于控制底泥向上覆水体释放磷,维持水体较低总磷是必要的。温度为30℃,20℃和5℃3种条件下,当反应24 h后,三者均达到吸附平衡。因此,当上覆水的磷质量浓度较低时,高温条件下基质的磷释放速度会高于低温条件下的磷释放速度。研究结果旨在为正确认识、合理评估环境因素对湖泊水体磷的影响提供更为充分恰当的试验依据和理论解释。     

Kinetic analysis of anaerobic phosphorus release during biological phosphorus removal process

Enhanced biological phosphorus removal (EBPR) is a commonly used and sustainable method for phosphorus removal from wastewater. Poly-β-hydroxybutyrate (PHB), polyphosphate, and glycogen are three kinds of intracellular storage polymers in phosphorus accumulation organisms. The variation of these polymers under different conditions has an apparent influence on anaerobic phosphorus release, which is very important for controlling the performance of EBPR. To obtain the mechanism and kinetic character of anaerobic phosphorus release, a series of batch experiments were performed using the excessively aerated sludge from the aerobic unit of the biological phosphorus removal system in this study. The results showed that the volatile suspended solid (VSS) had an increasing trend, while the mixed liquid suspended sludge (MLSS) and ashes were reduced during the anaerobic phosphorus release process. The interruption of anaerobic HAc-uptake and phosphorus-release occurs when the glycogen in the phosphorus-accumulating-organisms is exhausted. Under the condition of lower initial HAc-COD, HAc became the limiting factor after some time for anaerobic HAc uptake. Under the condition of higher initial HAc-COD, HAc uptake was stopped because of the depletion of glycogen in the microorganisms. The mean ratio of Δρ _P/Δρ _PHB, Δρ _GLY/Δρ _PHB, Δρ _P/ΔCOD, was 0.48, 0.50, 0.44, and 0.92, respectively, which was nearly the same as the theoretical value. The calibrated kinetic parameters of the HAc-uptake and phosphorus-release model were evaluated as follows: Q _HAc,max was 164 mg/(g · h), Q _P,max was 69.9 mg/(g · h), K _gly was 0.005, and KCOD was 3 mg/L. An apparently linear correlation was observed between the ratio of Δρ _P/ΔCOD and pH of the solution, and the equation between them was obtained in this study.     

Prediction of sulphur removal with Acidithiobacillus sp. using artificial neural networks

Artificial neural network (ANN) model was used to predict the extent of sulphur removal from three types of coal using native cultures of Acidithiobacillus ferrooxidans. The type of coal, initial pH, pulp density, particle size, residence time, media composition and initial sulphur content of coal were fed as input to the network. The output of the model was sulphur removal. The resulting ANN showed satisfactory prediction of sulphur removal percentages with mean absolute deviations varying from 0.003 to 0.5. A three layer feed forward neural network model consisting of an input layer, one hidden layer and an output layer was found to give satisfactory results. Although the number of data sets were limited, the parity plot shows that the model estimations for the test set was good.     

Identification of a dynamic lake model by the group method of data handling: An application to lake ontario

A revised algorithm of the group method of data handling (GMDH) is used to model and identify water quality dynamics in Lake Ontario. The state variables in the model are corrected chlorophyll a, volume-averaged over the top 20 m, and soluble reactive phosphorus in three layers, 0–20 m, 20–40 m and from 40 m to bottom. Inputs are the average quarterly temperatures for each layer and the total phosphorus loadings. Two kinds of model are developed: recursive and iterative; they are used to simulate long-term predictions for three different hypothetical rates of phosphorus loading. Results show that GMDH can be usefully employed to develop lake models with a very low expense of manpower and computer time. This exercise compares well with other large-scale modelling efforts of Lake Ontario, even if necessarily more limited in scope.     

厌氧条件下剩余污泥中磷及相关指标的释放和变化规律

污水处理过程中产生的剩余污泥富含大量的氮磷元素,从剩余污泥中回收磷是解决磷资源日益缺乏的一种有效途径。探寻出剩余污泥中磷的释放规律是实现剩余污泥中磷回收的首要前提。因此,以实际污水处理厂污泥为研究对象,建立污泥停留时间为5d的中试模型系统。通过系统分析5d停留时间的厌氧条件下污泥中污泥浓度、上清液总磷和氨氮浓度的变化情况,为后续的污泥磷回收提供支撑条件。研究结果表明,在中试系统污泥停留时间5d的厌氧条件下,剩余污泥微生物衰亡自溶或被分解,胞内物质释放,从而使固态物质转化为液态,污泥中磷及相关的氮等物质得到了较大的释放,污泥上清液总磷和氨氮质量浓度可分别达到100和40 mg·L^-1以上。所释放出的氮磷浓度足以满足鸟粪石回收氮磷方法所需的最低经济性要求,为污泥进行厌氧消化后采用鸟粪石的方法回收释放的氮磷提供了重要的基础依据。研究中还发现5d停留时间下, SS和VSS都有不同程度的降低,二者分别减少8.34%和10.14%以上,其中VSS的减少量占SS减少量的65%左右。同时,进入厌氧反应系统的初始污泥浓度对于氮磷的释放有着较大的影响,反应系统的SS在6300~7200 mg·L^-1的条件下,磷和氮的单位质量污泥释放量达到最佳,分别达到单位干污泥0.015和0.006 mg·mg^-1。研究结果为剩余污泥中回收氮磷提供了重要的依据。     

集约化蔬菜地土壤磷素累积特征及流失风险

以南京市郊集约化蔬菜长期种植基地为对象,采集蔬菜种植年限分别为3~5、15~20、25~30 a的土壤,测定土壤全磷(TP)、速效磷(Olsen-P)、水溶性磷(CaCl2-P)、生物有效磷(NaOH-P)的含量,并对0—20 cm土层磷素吸附特性进行分析,通过研究土壤磷吸附饱和度(DPS)、最大缓冲容量(MBC)来对土壤磷素流失风险进行评估。结果表明,在0—20 cm土层,除NaOH-P外,其余各形态磷(TP、Olsen-P、CaCl2-P)都随种植年限延长呈增加趋势。不同种植年限土壤TP、Olsen-P、CaCl2-P、NaOH-P主要积累在0—20 cm土层,且随着土层深度的增加土壤磷的累积量逐渐降低。DPS随种植年限延长而升高,种植年限25~30 a的菜地0—5 cm土层DPS超过土壤磷素流失环境敏感指标临界值(25%),其MBC也最低,表明随着蔬菜种植年限的延长土壤磷素流失风险加剧,且流失风险主要体现在0—5 cm土层。     

A test of two models of different levels of complexity for predicting changes of phosphorus concentration in a lake's outflow

The objective of this investigation is to compare the ability of a one-box model and a two-box model to predict the temporal variations of total phosphorus in the outflow of several lakes. The one-box model considers only total phosphorus and treats the lake as well-mixed, all year round. The two-box model considers two phosphorus fractions and the epilimnion and hypolimnion. For five shallow Canadian Shield lakes, some of the temporal variability in lake phosphorus concentrations can be explained on the basis of changes in hydraulic inflows and phosphorus loadings. Both models give roughly similar predictions for shallow lakes with high hydraulic loadings (1–200 m/year) and small variations in total phosphorus concentrations. In comparing the settling and hydraulic outflow mechanisms, a sensitivity analysis shows that both models are more sensitive to the settling rate if the lake's hydraulic loadings are less than 1 m/year, and more sensitive to the outflow rate if the lake's hydraulic loadings are greater than 100 m/year. This analysis suggests a priority for concentrating economic and other resources in conducting field measurement programs for testing phosphorus models.     

Measuring mucus thickness in reef corals using a technique devised for vertebrate applications

A method previously used to measure thickness of the surface mucus layer (SML) of the mammalian gastrointestinal tract has been applied to the SML of reef corals. It involves manual measurement of mucus thickness using a micromanipulator and fine glass needle (micropipette) and is non-destructive to the coral, meaning that repeated measurements can be taken. A measurable mucus layer was recorded in all cases in the study, which comprised 450 individual thickness measurements from four coral species. Mucus thickness ranged from 145 to 700 μm. Thus, whatever dynamic processes control mucus synthesis, secretion to the tissue surface and subsequent release into the water column, a continuous mucosal barrier is maintained. A change in SML thickness was recorded as a response to aerial exposure during the natural tidal cycle and to solar exposure-induced bleaching, although the response due to bleaching varied between two studied species. The technique is rapid, cost-effective and a simple means of assessing coral SML thickness, a variable that shows significant variation in relation to environmental conditions and is likely to be an important health indicator in these organisms.     

Phosphorus flow analysis of the socioeconomic ecosystem of Shucheng County, China

Human activities disturb the long-term phosphorus (P) cycle in nature, whereby the resulting intensive release of P contributes to the eutrophication of surface water. Hence, a detailed understanding of P flow as it relates to socioeconomic systems is essential for effective nutrient management. This study develops a substance-flow-analysis model for P metabolism for the socioeconomic ecosystem of Shucheng County in Anhui Province in central China as a case study. We estimate P flow using data from questionnaires, face-to-face interviews, published literature, and official statistical databases. Our results show that P flow in Shucheng's current socioeconomic system is linear and openly metabolic. The total P input into Shucheng in 2008 reached 12 748 Mg, mainly as P ores and crops. In all, 43.83% of the total P input was exported, and 30.44% was discharged into surface water. More-balanced nutrient management and options for improving nutrient use efficiency are discussed. The quantifiable, science-based methods used in this study may be applied to neighboring regions of central China for sustainable development and water management.