Phosphorus fractionation in lake sediments--lakes Volvi and Koronia, N. Greece

Sediments from two lakes, the meso-to-eutrophic Volvi and the hypertrophic Koronia, located in N. Greece were examined on the basis of P-fractionation. In both lakes, the rank order of P-fractions was HCl-P > NaOH-P > BD-P > NH4Cl-P. The loosely sorbed phosphorus (NH4Cl-P) represented < 1% of the sedimentary inorganic phosphorus, while the reductant phosphorus (BD-P) ranged 5-6%. The calcium bound phosphorus (HCl-P) showed considerable contribution (59-74%) to the sedimentary inorganic P-loads. The metal oxide bound phosphorus (NaOH-P) was higher in the hypertrophic (30-35%) than in the meso-to-eutrophic system (19-28%). Fine-sized sediments exhibited significantly higher concentrations of HCl-P in Volvi and NH4Cl-P in Koronia. Sampling month had significant effect in variance of most P-fractions and other sediment features in both lakes. Use was also made of multivariate statistics to identify the factors which influence the sedimentary phosphorus. NaOH-P was the most reactive fraction in Lake Volvi. Iron compounds and organic matter seem to play a significant role in regulating this labile P-budget. NH4Cl-P was the more reactive fraction in Lake Koronia which was influenced by sedimentation of P-absorbed on clay/silt fine particles.     

城市富营养化水体底泥净化磷效果

以城市富营养化水体底泥和上覆水为材料,研究了扰动状态下底泥对外源磷的净化效果。结果表明,扰动状态下,200 g湿底泥从上覆水中共吸收外源磷19.92 mg,而静止状态下,200 g湿底泥仅吸收了13.61 mg。然而,厌氧状态下,前者内源磷释放量仅占吸收磷量的43%,而后者则高达63.4%。说明底泥扰动不仅强化了底泥对外源磷的吸收,而且也强化了内源磷的固定能力。这与扰动状态下外源磷在不同形态磷间的数量分布有关。底泥扰动和静止状态下,难释放态磷(HCl-P、闭蓄态Fe/Al-P)的增加量分别占底泥吸收外源磷量的36%和21%。     

红枫湖底泥磷负荷释放

为了研究高原湖泊底泥沉积物中磷的释放负荷,对贵州红枫湖区10个地区的沉积物进行了磷形态分析。选取10个采样点中5个典型区域,研究结果表明,底泥中各形态磷占总磷比例Org-P为58.6%,NaOH-P为29.91%,Ca-P为11.48%,底泥中主要的磷形态为有机磷。上覆水溶解性总磷酸盐(TSP)与底泥中各形态磷的相关性研究表明,底泥中的Ca-P与上覆水中的TSP几乎没有相关性,NaOH-P与Org-P与上覆水的TSP有较高的相关性(R2>0.94),而底泥中的总磷(TP)与上覆水中的TSP相关性最高(R2>0.98),底泥中这种形态的结构有利于抑制底泥的释放。研究表明,在10点位样品中,间隙水中TP和SRP(溶解性正磷酸)浓度远大于上覆水体中相应磷形态的浓度,间隙水中TP平均浓度为0.37 mg/L,SRP平均浓度为0.18 mg/L,上覆水体中TP平均浓度为0.10 mg/L,SRP平均浓度为0.02 mg/L,间隙水中TP、SRP与上覆水中TP、SRP存在了一种浓度梯度。     

Characteristics of phosphorus components in surface sediments from a Chinese shallow eutrophic lake (Lake Taihu): new insights from chemical extraction and <Superscript>31</Superscript>P NMR spectroscopy

As a primary factor responsible for lake eutrophication, a deeper understanding of the phosphorus (P) composition and its turnover in sediment is urgently needed. In this study, P species in surface sediments from a Chinese large eutrophic lake (Lake Taihu) were characterized by traditional fractionation and ³¹P nuclear magnetic resonance (NMR) spectroscopy, and their contributions to the overlying water were also discussed. Fractionation results show that NaOH-P predominated in the algal-dominated zone, accounting for 60.1% to total P in Zhushan Bay. Whereas, refractory fractions including HCl-P and residual-P were the main P burial phases in the macrophyte-dominated zone, the center and lakeshore. Recovery rates of the total P and organic P were greatly improved by using a modified single-step extraction of NaOH-EDTA, ranging from 22.6 to 66.1% and from 15.0 to 54.0%. Ortho-P, monoester-P, and pyro-P are identified as the major P components in the NaOH-EDTA extracts by ³¹P NMR analysis. Trace amount of DNA-P appeared only in sediments from algal- and macrophyte-dominated zones, ascribing to its biological origin. The relative content of ortho-P is the highest in the algal-dominated zone, while the biogenic P including ester-P and pyro-P is the highest in the macrophyte-dominated zone. Moreover, ortho-P and pyro-P correlated positively with TP and chlorophyll a in the overlying water, whereas only significant relationships were found between monoester-P, biogenic P, and chlorophyll a. These discrepancies imply that inorganic P, mainly ortho-P, plays a vital role in sustaining the trophic level of water body and algal bloom, while biogenic P makes a minor contribution to phytoplankton growth. This conclusion was supported by the results of high proportion of biogenic P in algae, aquatic macrophytes, and suspended particulate from the published literature. This study has significant implication for better understanding of the biogeochemical cycling of endogenous P and its role in affecting lake eutrophication.     

Effects of oxygen on the release and distribution of phosphorus in the sediments under the light condition

Effects of oxygen on the release and distribution of phosphorus (P) in the sediments in the presence of light were investigated, using sediment cores and overlying water from Lake Taihu, in China. The results show that P can be released from sediments to the overlying water in both anoxic and aerobic conditions. But more P was released in the anoxic condition. The transformation of P between various fractions in the sediments was observed during the release experiments. Concentrations of Ca-bound P and organic P in the sediments decreased in both conditions, but Fe/Al-bound P increased in the aerobic condition. The decrease of total P and P fractions in the sediments is consistent with the accumulative increase in quantity (AIQ) of total P (TP) in the overlying water, but is contrary with the AIQ of dissolved inorganic P. This is due to the uptake of algae by the dissolved inorganic P. Total nitrogen in the sediments in the anoxic condition was lower than that in the aerobic condition, and pH in the overlying water increased in the anoxic condition.     

Enhancement of dissolved phosphorus release from sediment to lake water by Microcystis blooms--an enclosure experiment in a hyper-eutrophic,subtropical Chinese lake

To clarify the possible influence of Microcystis blooms on the exchange of phosphorus (P) between sediment and lake water, an enclosure experiment was conducted in the hypereutrophic subtropical Lake Donghu during July-September 2000. Eight enclosures were used: six received sediment while two were sediment-free. In mid-August, Microcystis blooms developed in all the enclosures. There was a persistent coincidence between the occurrence of Microcystis blooms and the increase of both total P (TP) and soluble reactive P (SRP) concentrations in the water of the enclosures with sediments. In sediment-free enclosures, TP and SRP concentrations remained rather stable throughout the experiment, in spite of the appearance of Microcystis blooms. The results indicate that Microcystis blooms induced massive release of P from the sediment, perhaps mediated by high pH caused by intense algal photosynthesis, and/or depressed concentrations of nitrate nitrogen (NO3-N).     

Seasonal variations in phosphorus species in the surface sediments of the Gulf of Riga, Baltic Sea.

The redox-dependent variations in concentrations of phosphorus at two different accumulation bottom areas were investigated in the Gulf of Riga (Baltic Sea) between December 1993 and January 1995. The sediment samples from nine sampling occasions were analyzed for phosphorus forms and redox potential. The average concentrations of total phosphorus measured in 0-1 cm (65 and 89 micromol P g(-1) for sites G5 and T3, respectively) were among the highest reported from the entire Baltic Sea. Redox-dependent "mobile" phosphorus (MP) contributed more than 50% of total in the uppermost-oxidized centimeter, whereas in reduced layers it was 16-18% throughout the year. The significant differences (ANOVA, P<0.01) among months of inorganic phosphorus (IP) concentration at 0-1 cm were observed at site G5 due to temporary accumulation of mobile phosphorus mediated by redox-dependent bacteria activity during summer. On the contrary no accumulation was observed at T3 probably as a result of low redox potential caused by high accumulation rates and low bioturbation. Although the water column above sediments remained oxic throughout the investigation period, the redox potential at site T3 was close to the redoxcline (i.e., +230 mV) during summer. Further increase of eutrophication might lead to development of anoxic conditions at sediment-water interface and that in turn will result in rapid release of redox-dependent phosphorus stored in surface sediments. The availability of excess phosphorus will further enhance eutrophication in partly phosphorus-limited Gulf of Riga.     

Sedimentation and seasonal variation of hexachlorocyclohexanes in sediments in a eutrophic lake, China

Hexachlorocyclohexane (HCH) concentrations in sediments and sediment trap fluxes of particulate organic carbon and HCHs were measured bi-weekly from March 31 to October 18, 2006 in an urban eutrophic lake in Tianjin, China, in order to investigate sedimentation and seasonal variation of HCHs in sediments. HCH concentrations (dry weight basis) ranged from 2.2 to 20.2 ng/g (mean 7.7 ng/g) in surface sediments and from 26.6 to 972.7 ng/g (mean 187.0 ng/g) in settling particles, respectively. A clear seasonal variation in HCH sedimentation and HCH concentrations in sediments was observed. The maximal HCH deposition occurred following a spring phytoplankton bloom. The average flux of HCHs to sediment was approximately 21-fold higher in April to mid-June as compared to late June to October. This was attributed to the high vertical fluxes at the end of the spring phytoplankton bloom. The maximum values of HCH concentrations in sediments were observed in mid-June to late July. Concentrations of HCHs in sediments from the eutrophic lake were well-correlated with organic carbon contents in sediments. The annual sediment trap flux of HCHs in the eutrophic lake, which was estimated using data obtained in the eutrophic lake, was 117 microg/m2 yr, about 72% of which was attributed to the sedimentation corresponding to spring bloom phytoplankton deposition in late May to mid-June. The high sediment trap flux of HCHs in the eutrophic lake was related to serious local contamination.     

合肥市南淝河不同排口表层沉积物磷形态分布特征

对合肥市南淝河不同排口处表层沉积物进行了采样,并采用修正后的标准测试程序SMT和钼锑抗紫外分光光度法测定了其中的总磷(TP)、无机磷(IP)、有机磷(OP)、铁/铝磷(Fe/Al-P)和钙磷(Ca-P),同时分析了各形态磷之间以及与沉积物有机质之间的相关性。结果表明,由于各排口附近不同的水动力条件,污染状况以及沉积环境,各排口表层沉积物总磷(TP)的质量分数存在显著差异,其值在771.23~3 065.36 mg/kg之间,除二里河排口(S15)沉积物磷以钙磷(CaP)为主外,其他采样点表层沉积物磷均以铁/铝磷(Fe/Al-P)为主,各形态P的最低值均在位于南淝河上游的S4点,TP、IP、Fe/Al-P的最大值均出现在位于望塘污水厂排口下游60 m处的S6点,潜在释放磷比例最大值在南淝河上游受农业面源污染影响较大的S3点。沉积物各形态磷之间存在着不同程度的相关性,各形态磷与有机质存在着显著的正相关。以上结果表明,南淝河沉积物磷形态分布特征受排口类型影响显著,其中城市污水处理厂尾水可能是受纳水体沉积物重要的磷源。     

Sedimentation and seasonal variation of hexachlorocyclohexanes in sediments in a eutrophic lake,China

Hexachlorocyclohexane (HCH) concentrations in sediments and sediment trap fluxes of particulate organic carbon and HCHs were measured bi-weekly from March 31 to October 18, 2006 in an urban eutrophic lake in Tianjin, China, in order to investigate sedimentation and seasonal variation of HCHs in sediments. HCH concentrations (dry weight basis) ranged from 2.2 to 20.2 ng/g (mean 7.7 ng/g) in surface sediments and from 26.6 to 972.7 ng/g (mean 187.0 ng/g) in settling particles, respectively. A clear seasonal variation in HCH sedimentation and HCH concentrations in sediments was observed. The maximal HCH deposition occurred following a spring phytoplankton bloom. The average flux of HCHs to sediment was approximately 21-fold higher in April to mid-June as compared to late June to October. This was attributed to the high vertical fluxes at the end of the spring phytoplankton bloom. The maximum values of HCH concentrations in sediments were observed in mid-June to late July. Concentrations of HCHs in sediments from the eutrophic lake were well-correlated with organic carbon contents in sediments. The annual sediment trap flux of HCHs in the eutrophic lake, which was estimated using data obtained in the eutrophic lake, was 117 μ g/m² yr, about 72% of which was attributed to the sedimentation corresponding to spring bloom phytoplankton deposition in late May to mid-June. The high sediment trap flux of HCHs in the eutrophic lake was related to serious local contamination.     

盐碱地区沉积物磷释放特性及影响因素

为研究沉积物磷释放对盐碱地区景观水体富营养化的影响,以天津滨海新区泰达河道为对象,应用沉积物中磷形态的标准测试方法（SMT）,分析了沉积物中磷的形态;研究了沉积物中磷的解吸动力学,并探讨了水力扰动、pH和盐度对沉积物中磷解吸的影响。结果表明,无机磷（IP）为沉积物中磷的主要形态,总量为0.637 mg/g,IP中又以钙磷（Ca-P）为主,约占IP的80%,而铁/铝磷（Fe/Al-P）仅占20%。0-4 h为磷的快速解吸阶段,4-24 h为慢速解吸阶段,并逐渐达到平衡。泰达河道沉积物对磷具有一定的吸持能力,不易解吸。增强水力扰动的强度会促进磷的解吸,但影响不大;在碱性条件下,增加pH对磷的解吸没有显著影响;增加水体盐度,能促进磷的解吸。     

Spatial distribution and ecological assessment of nickel in sediments of a typical small plateau lake from Yunnan Province,China

Nickel (Ni) in small plateau lake sediments plays an important role in influencing the quality of lake ecosystems with a high degree of endemism and toxicity. This paper focuses on the spatial distribution and ecological risks of nickel in the sediments of Jianhu Lake, a small plateau lake in China, and the influence of pH and total organic carbon (TOC) on nickel concentrations. The results showed that average total nickel concentrations were 138.99 ± 57.57 mg/kg (n = 38) and 184.31 ± 92.12 mg/kg (n = 60) in surface sediments (0–10 cm top layer) and sediment cores (0–75 cm depth), respectively, and that the residual fraction was the main form of nickel. Simultaneously, through a semivariogram model, strong spatial dependence among pH, TOC, and the oxidizable fraction was revealed, whereas total nickel, exchangeable and the weak acid soluble fraction, reducible fraction, and residual fraction showed moderate spatial dependence. The vertical distribution revealed that nickel accumulated mainly in the bottom 5 cm (70-75 cm) of the sediment layer and that the pH was higher there, whereas TOC was concentrated mainly in the top 5 cm of sediment. Using geoaccumulation and a potential ecological risk index, moderate nickel pollution and moderate risk levels were found in most surface sediments, but moderate nickel pollution and high risk levels were observed in most sediment cores. In addition, pH and TOC were found to have a strong effect on the distribution and concentration of nickel and its fractions in the small plateau lake. In summary, nickel posed a certain degree of pollution and ecological risk, which deserves attention in the sediments of small plateau lakes.

     

Application of principal component analysis for the estimation of source of heavy metal contamination in surface sediments from the Rybnik Reservoir

The concentrations of metals, loss of ignition and nutrient (N, P) were determined in the bottom sediments of the Rybnik Reservoir (southern Poland). The mean concentrations of the metals in the bottom sediments were: Cd 25.8 microgram/g, Cu 451.7 microgram/g, Zn 1583.4 microgram/g, Ni 71.1 microgram/g, Pb 118.6 microgram/g, Cr 129.8 microgram/g, Fe 38782 microgram/g and Mn 2018.7 microgram/g. The bottom sediments are very heavily loaded with zinc, manganese, copper, nickel, phosphorus and lead (percentage enrichment factor), and cadmium, phosphorus and zinc (index of geoaccumulation). The increase of cadmium, lead, nickel and zinc concentrations was connected with the inflow of the contaminated water of the river Ruda and long-range transport. The contamination of the reservoir with copper and manganese resulted mainly from atmospheric precipitation. The variability of the bottom sediment loading with metals during the investigations was affected in the first place by changes in the concentration of iron, but also those elements whose concentrations in the bottom sediment were elevated compared to the concentrations in shale--cadmium, nickel and lead.     

Effect of overlying water pH, dissolved oxygen, salinity and sediment disturbances on metal release and sequestration from metal contaminated marine sediments

Experiments were undertaken to examine the key variables affecting metal release and sequestration processes in marine sediments with metal concentrations in sediments reaching up to 86, 240, 700, and 3000 mg kg(-1) (dry weight) for Cd, Cu, Pb and Zn, respectively. The metal release and sequestration rates were affected to a much greater extent by changes in overlying water pH (5.5-8.0) and sediment disturbance (by physical mixing) than by changes in dissolved oxygen concentration (3-8 mg l(-1)) or salinity (15-45 practical salinity units). The physical disturbance of sediments was also found to release metals more rapidly than biological disturbance (bioturbation). The rate of oxidative precipitation of released iron and manganese increased as pH decreased and appeared to greatly influence the sequestration rate of released lead and zinc. Released metals were sequestered less rapidly in waters with lower dissolved oxygen concentrations. Sediments bioturbated by the benthic bivalve Tellina deltoidalis caused metal release from the pore waters and higher concentrations of iron and manganese in overlying waters than non-bioturbated sediments. During 21-day sediment exposures, T. deltoidalis accumulated significantly higher tissue concentrations of cadmium, lead and zinc from the metal contaminated sediments compared to controls. This study suggests that despite the fact that lead and zinc were most likely bound as sulfide phases in deeper sediments, the metals maintain their bioavailability because of the continued cycling between pore waters and surface sediments due to physical mixing and bioturbation.     

Influence of algal bloom degradation on nutrient release at the sediment–water interface in Lake Taihu, China

Algal bloom could drastically influence the nutrient cycling in lakes. To understand how the internal nutrient release responds to algal bloom decay, water and sediment columns were sampled at 22 sites from four distinct regions of China’s eutrophic Lake Taihu and incubated in the laboratory to examine the influence of massive algal bloom decay on nutrient release from sediment. The column experiment involved three treatments: (1) water and sediment (WS); (2) water and algal bloom (WA); and (3) water, sediment, and algal bloom (WSA). Concentrations of dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), ammonium (NH ₄ ⁺ -N), and orthophosphate (PO ₄ ^3? -P) were recorded during incubation. The decay of algal material caused a more rapid decrease in DO than in the algae-free controls and led to significant increases in NH ₄ ⁺ -N and PO ₄ ^3? -P in the water. The presence of algae during the incubation had a regionally variable effect on sediment nutrient profiles. In the absence of decaying algae (treatment WS), sediment nutrient concentrations decreased during the incubation. In the presence of blooms (WSA), sediments from the river mouth released P to the overlying water, while sediments from other regions absorbed surplus P from the water. This experiment showed that large-scale algal decay will dramatically affect nutrient cycling at the sediment–water interface and would potentially transfer the function of sediment as “container” or “supplier” in Taihu, although oxygen exchange with atmosphere in lake water was stronger than in columns. The magnitude of the effect depends on the physical–chemical character of the sediments.     

Polybrominated diphenyl ethers in sediments of the Daliao River Estuary, China: levels, distribution and their influencing factors

The concentrations, compositional profiles, possible sources of polybrominated diphenyl ethers (PBDEs) in sediments of the Daliao River Estuary as well as the factors influencing the distribution of PBDEs were investigated. The total concentrations of PBDEs ranged from 0.13 to 1.98 ng g⁻¹ d.w. BDE209 was the dominating congener in all sediment samples, indicating the pollution of PBDEs in the Daliao River Estuary mainly came from the use of deca-BDE commercial mixtures. The intrusion of sea waters promoted the deposition of the colloid-associated PBDEs in the estuary. There were significantly negative correlations between PBDE concentration in sediment with pH value and salinity in the bottom water. The higher river flow in the flood season (summer) obviously accelerated the transport of PBDEs, and thereby increased the risk of PBDE contamination to the deep ocean. Moreover, a positive correlation between TOC and PBDE distributions was observed, suggesting that TOC regulated the distributions of PBDEs in sediments of Daliao River Estuary.     

Effects of experimental acidification on mobilisation of metals from sediments of limed and non-limed lakes

In order to study the influence of pH on the mobilisation of metals from lake sediments, intact sediment cores with overlying water were sampled from one lime treated lake and one acidified lake. The overlying water of two cores from each lake was successively acidified to pH 4.2 over a period of 3 months. In the acid treated samples from the limed lake, the initial concentrations of Al, Cd, Mn, Pb and Zn in the overlying water were generally lower and the final concentrations were higher than in the acid treated samples from the acidified lake. The labile inorganic fraction of Al (Al(i)) was increasingly dominating as pH decreased. Redox potential and pH in the sediment indicated that the upper two centimetres were involved in the exchange reactions. The experiment showed that mobilisation of metals from sediments can occur and the results indicated that mobilisation could contribute to increased concentrations of metals in lake water during reacidification of formerly lime treated lakes.     

Effects of light, microbial activity, and sediment resuspension on the phosphorus immobilization capability of drinking water treatment residuals in lake sediment

Drinking water treatment residuals (WTRs), nonhazardous by-products generated in a drinking water treatment plant, can be reused to immobilize phosphorus (P) to control the internal P loading from lake sediments for eutrophication control. Reasonably, before practical application, it is essential to determine the P immobilization capability of WTRs in lake sediments under various conditions. In this work, laboratory scale experiments were conducted to investigate the effects of light, microbial activity, and sediment resuspension on the P immobilization capability of WTRs. The results suggested that absence of light, low microbial activity, and sediment resuspension can increase the internal P loading from lake sediments. WTRs can, however, reduce the internal P loading significantly. Further analysis demonstrated that WTRs can stabilize P, decreasing the P bioavailability in the sediments under varied conditions. WTRs also presented little undesirable effects on the dissolved oxygen levels and pH of overlying water. Therefore, light, microbial activity, and sediment resuspension have little effect on the P immobilization capability of WTRs in lake sediments.     

水葫芦对滇池底泥氮磷营养盐释放的影响

为了探讨水葫芦对富营养湖泊底泥氮磷营养盐释放的影响,通过原位采集滇池柱状底泥,以蒸馏水为上覆水,进行了25d的室内静态模拟实验。实验比较了水葫芦处理组和空白对照组底泥氨氮（NH4-N）、硝态氮（NO3^-N）、溶解性总氮（DTN）、正磷酸盐（PO4^3--P）等的释放特征。结果表明,与对照组相比,水葫芦处理组上覆水溶解氧、pH显著性降低,而PO4^3-P浓度显著性升高;在实验前2d,水葫芦处理组上覆水NH4^＋N和DTN浓度显著性高于对照组,而在5～25d时,其显著性低于对照组。根据上覆水营养盐浓度、水葫芦植株吸收营养盐总量,推算底泥氮磷营养盐释放的平均速率,表明水葫芦加速了滇池底泥氮、磷营养盐的释放速率,处理组氮、磷释放速率分别为对照组的5．3～170．2和1．5～21．6倍。     

底泥污染物释放动力学研究

采用模拟试验方式和新型微生物数量测定方法 ,研究了沼泽化湖泊底泥和受污染河流底泥在不同扰动状态下 ,底泥耗氧速率、氮和磷污染物释放动力学过程。结果表明 :( 1)底泥耗氧速率是同样条件下上覆水耗氧速率的 48倍 ,而在扰动状态下 ,底泥耗氧速率达到上覆水耗氧速率的 5 96— 93 6倍 ,扰动底泥显著增大其耗氧速率 ,底泥污染越严重 ,其耗氧速率越大 ,对水体产生的影响也越大。 ( 2 )扰动底泥可以显著增大底泥的氮磷释放速率 ,氮的释放受有机氮的氨化、氨氮的硝化、硝酸盐氮的反硝化以及氨氮被微生物吸收转化为有机氮等的影响 ;磷的释放过程受厌氧过程和底泥颗粒吸附的影响 ,耗氧速率高的底泥具有更大的氮磷释放潜力。 ( 3 )微生物数量在底泥污染物释放动力学中起着关键性作用 ,新型方法可以快速检测微生物总量。试验结果对于水环境的管理、受污染水体的修复 ,以及底泥的处理处置等都具有重要的指导意义