Pore Water Phosphorus Research Articles

Longevity and efficacy of lanthanum-based P remediation under changing dissolved oxygen availability in a small eutrophic lake.

We set out to study the seasonal variations in porewater phosphorus and lanthanum concentrations in the dated sediment cores from a small eutrophic lake that has been treated with Phoslock, a lanthanum-modified bentonite (LMB) amendment. Three sites were sampled when the hypolimnion was either oxygenated or anoxic: (i) the lake's deepest point, (ii) a littoral site receiving inflows from the catchment, and (iii) a littoral site influenced by nearby septic tanks. Phosphate (PO43--P), lanthanum (La), iron (Fe), dissolved organic carbon (DOC) and sulfate (SO42-) were measured in porewater samples. An inverse diagenetic model was used to quantify fluxes of dissolved elements across the sediment-water interface as well as the net rate of their reactions along the porewater concentration gradients. Results show that porewater P and Fe underwent strong seasonal dynamics, while La did not. P fluxes, 20-fold higher at the deepest site than elsewhere in the basin, were influenced by anoxic conditions in the hypolimnion during summer and winter, suggesting that P mobility remained sensitive to redox fluctuations despite the addition of La. At the deepest site, fluxes of P across the sediment-water interface increased from 1 to 9 × 10-9 μmol cm-2 s-1 between spring and summer, while the rate of P production to the porewater also increased a hundredfold. These increases were concurrent with Fe mobilization. Finally, sediment dating shows that the fraction of P sequestered by La is buried under freshly deposited sediment at a rate of 2-3 mm per year. These results indicate that external P fluxes and erosion control remain crucial to maintain the longevity of the LMB treatment.

Spatio-temporal variability of porewater phosphorus concentrations in streambed sediments of an agricultural stream

Streambed sediment and groundwater represent important stores of soluble reactive phosphorus (SRP) in freshwater catchments yet their contributions to watershed SRP loads remain unclear. This study evaluates the spatio-temporal variability and geochemical and hydrologic controls on porewater SRP in the streambed along an agricultural reach, including the influence of groundwater-surface water interactions. High porewater SRP (>1000 µg/L) and high available sediment-bound SRP were observed in low groundwater discharge zones, specifically in the shallow (≤0.1 m) streambed sediments. Porewater SRP concentrations were linked to iron and possibly manganese redox cycling with more-reducing conditions consistently coinciding with high SRP. Porewater SRP varied temporally but distinct seasonal changes across the stream reach were not observed. A shallow oxic cap that may limit SRP release to the stream was observed in the very shallow streambed but its presence was spatially and temporally discontinuous. Finally, data indicate P-rich shallow streambed sediments are the likely source of the observed high SRP porewater concentrations in the streambed rather than incoming groundwater from the adjacent fields. Overall, the findings highlight the complexity of SRP dynamics in agricultural streambeds and provide insight into processes governing the timing and location of SRP loading streams.

九龙江河口区养虾塘沉积物-水界面营养盐交换通量特征

PDF HTML阅读 XML下载 导出引用 引用提醒 九龙江河口区养虾塘沉积物-水界面营养盐交换通量特征 DOI: 10.5846/stxb201603130448 作者: 作者单位: 福建师范大学,福建师范大学,湿润亚热带生态-地理过程教育部重点实验室,福建师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 福建省基本科研专项重点资助项目（2014R1034-1）；国家自然科学基金资助项目（41671088，41371127）；福建师范大学校级创新团队资助项目（IRTL1205）；福建师范大学地理科学学院研究生出国（境）访学资助计划和地理科学学院研究生科研创新资助项目（GY201601） Temporal variation of nutrients fluxes across the sediment-water interface of shrimp ponds and influencing factors in the Jiulong River Estuary Author: Affiliation: Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education,School of Geographical Sciences,Research Centre of Wetlands in Subtropical Region,Fujian Normal University,Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education,School of Geographical Sciences,Research Centre of Wetlands in Subtropical Region,Fujian Normal University,Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education,School of Geographical Sciences,Research Centre of Wetlands in Subtropical Region,Fujian Normal University,Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education,School of Geographical Sciences,Research Centre of Wetlands in Subtropical Region,Fujian Normal 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:通过对九龙江河口区陆基养虾塘水样和沉积物样品采集分析及结合室内模拟实验，探讨了虾塘在不同养殖阶段沉积物-水界面营养盐通量时间变化特征及其主要影响因素。虾塘沉积物向上覆水体释放NOx--N（NO2--N和NO3--N）、NH4+-N和PO43--P能力均呈现随养殖时间推移而降低的特征。沉积物在养殖中期和后期分别呈现对上覆水体NOx--N和PO43--P的吸收现象，但总体表现为释放（平均通量分别为（1.87±1.15）、（1.58±0.52）mg m-2 h-1和（1.22±0.62）mg m-2 h-1）。沉积物-水界面溶解无机氮交换以NH4+-N为主（沉积物平均释放通量为（46.18±13.82）mg m-2 h-1）。沉积物间隙水与上覆水间的营养盐浓度差（梯度）及温度对上述交换通量的时间动态特征具有重要调控作用。研究结果表明养殖初期或中期沉积物较高的无机氮（尤其是NO2--N和NH4+-N）释放是养殖塘水质恶化的一个极具潜力的污染内源，可能会对虾的健康生长产生负面效应，控制沉积物无机氮释放是养虾塘养殖初期和中期重要的日常管理活动之一。 Abstract:Eutrophication is increasingly challenging the sustainability and healthy development of aquaculture. The effects of variations in nutrient dynamics remain unclear, including porewater nutrient concentrations and nutrient fluxes at the sediment-water interface (SWI), from aquaculture ponds globally, and particularly in China. In this study, temporal variation of the concentrations of nitrogen and phosphorus in porewater and their fluxes across the interface of sediment-water was investigated in the Jiulong River estuary, a subtropic estuary on the southeast coast of China. Overlying water, intact sediments, and sediment porewater were collected using sediment samplers from three shrimp ponds in June, August, and October 2015. Overlying water and sediment porewater nutrient analyses were performed using an automatic continuous flow analyzer. SONE (sediment oxygen and nutrient exchanges) incubation techniques were used to measure rates of nutrient fluxes (NO2--N, NO3--N, NH4+-N, and PO43--P). NO2--N, NO3--N, NH4+-N, and PO43--P concentrations in porewater ranged from 0.01 to 0.06, 0.06 to 0.22, 10.31 to 14.13, and 0.05 to 0.35 mg/L, respectively, with mean values of 0.04, 0.15, 11.83, and 0.17 mg/L. Higher NO2--N and NO3--N concentrations in porewater occurred during June and higher NH4+-N and PO43--P concentrations occurred during August. The NO2--N, NO3--N, NH4+-N, and PO43--P fluxes across the interface of sediment-water ranged from -2.96 to 7.60, -1.00 to 3.15, -0.79 to 4.95, and 19.23 to 91.73 mg m-2 h-1, respectively. The fluxes of nitrogen and phosphorus nutrients across the interface of sedimentwater showed significant temporal variation, with higher nutrient release fluxes during June and lower fluxes during October. The mean fluxes of NO2--N, NO3N, and PO43--P from the sediment to overlying water were (1.87±1.15), (1.58±0.52), and (1.22±0.62) mg m-2 h-1, respectively, indicating that the shrimp pond sediment acted as a nitrogen and phosphorus release source. Dissolved inorganic nitrogen (DIN) release dominated by excess NH4+-N, and the NH4+-N flux from sediment was (46.18±13.82) mg m-2 h-1. Pearson's correlation analysis showed that the temporal variation of nitrogen and phosphorus fluxes were significantly positively correlated with sediment temperature (P < 0.05), but significantly negatively correlated with shrimp biomass (P < 0.05). The results suggest that the temporal variation of nutrients fluxes across the sediment-water interface in shrimp ponds was controlled by the nutrient concentration gradient, sediment temperature, and the foraging and metabolic activity of shrimp. This study highlighted that the relatively high DIN (NO2--N and NH4+-N) release from sediment during the initial and middle stages of aquaculture could be a potential pollution source in shrimp ponds, which might increase the risk of shrimp mortality. 参考文献 相似文献 引证文献

Alkaline Phosphatase: An Appraisal of its Critical Role in C-Limited Deep-Sea Sediments of Central Indian Basin

ABSTRACTAlkaline phosphatase (ALP) is a hydrolase that releases phosphate, a crucial nutrient supporting formation of many macromolecules. The oligotrophic sediments of Central Indian Basin (CIB) were examined for the extent of ALP activity in 20 cores up to 20 cm depth along with other biogeochemical parameters. Northern and southern stations distinctly clustered based on pore water phosphorus (P) concentrations. ALP appeared more active in south due to more P and organic carbon (C) limitation. Central transition profiles revealed interesting mixed diagenetic and geothermal influence. Inter- and intrazonal differences suggest that broadly established paradigms applicable to water columns may deviate in space and time in sedimentary systems. Gross differences in redox status could govern differential response in ALP activity under similar hydrostatic pressure. Hydrothermal scavenging reactions striping soluble P from pore water might be widespread in CIB albeit at extreme low intensities. ALP might redissolve the precipitated P and make it reavailable to microbes.

Distribution and migration characteristics of nitrogen and phosphorus in sediment-water interface from unstable coal mining subsidence area

以淮南后湖非稳沉采煤沉陷区沉积物-水体界面为研究对象,分析该湖未开发区(A区)、水产养殖区(B区)和水生蔬菜种植区(C区)3个功能区上覆水-间隙水-沉积物体系中氮、磷分布及其迁移特征.结果表明,氮、磷在不同水体界面的分布差异较大.其中上覆水中氮、磷浓度表现为A区>B区>C区;间隙水中氮、磷分布差异不显著,然而各功能区间隙水的氮、磷浓度明显高于上覆水,氮、磷主要由间隙水向上覆水中移动;沉积物中氮、磷含量以C区最高.后湖采煤沉陷区水体表现出氮污染、磷限制的现象.;Three water bodies of different functionalities, i.e., undeveloped (A), aquaculture (B), and aquatic vegetable planting (C), in Lake Houhu unstable coal mining subsidence area, were studied to address the distribution and migration of nitrogen and phosphorus in a column system of overlying water column, sediment pore water and sediments. The results showed that the contents of nitrogen and phosphorus were quite different in different sediment-water interface. The concentrations of nitrogen and phosphorus in overlying water column were in the order of A>B>C. Although no significant difference in concentrations of nitrogen and phosphorus in pore waters of these three water bodies were observed, they were distinctly higher than those in overlying water columns. This suggested an upward migration of nitrogen and phosphorus from pore waters to overlying water columns. The highest concentrations of nitrogen and phosphorus were examined in the sediments of aquatic vegetable planting water body. Overall, the study found that water bodies were polluted by nitrogen but had limited availability of phosphorus.

Hurricane-Induced Sedimentation Improves Marsh Resilience and Vegetation Vigor under High Rates of Relative Sea Level Rise

During the next century coastal marsh sustainability will largely depend on whether or not marshes can keep pace with rising sea levels while weathering more frequent and/or intense storms. In particular, hurricanes have the potential to inflict widespread damage to coastal systems, but can also deliver nourishing inorganic sediment. To determine if hurricane-induced sedimentation can enhance marsh condition and promote marsh sustainability, even in regions of high relative sea level rise (RSLR), we experimentally assessed primary productivity and marsh resilience in marshes that were subject to various levels of hurricane-induced sedimentation in 2005 and 2008 in coastal Louisiana, where RSLR is accelerated due to land subsidence. Primary production and marsh resilience, i.e., recovery rate of plant cover after an experimental disturbance, increased in response to hurricane-induced sedimentation. Sedimentation led to a more oxidized soil environment, reduced porewater sulfide concentrations, and increased porewater phosphorus and exchangeable soil iron and manganese concentrations. Improved soil physicochemical conditions were likely responsible for the increased productivity and resilience, even with the high rates of RSLR the area experiences. This suggests that when storm-induced sedimentation is sufficient, stability of coastal marshes may be enhanced, at least for some time, helping to cope with sea level rise.

Ikaite Abundance Controlled by Porewater Phosphorus Level: Potential Links to Dust and Productivity

AbstractGlendonites are pseudomorphs of the mineral ikaite (CaCO3·6H2O) after loss of hydration water and occur in distinctive euhedral crystalline forms, sometimes clustered as rosettes of up to tens of centimeters in diameter. While it is generally accepted that organic-rich environments, methane seeps, and high phosphate levels are important for ikaite formation, glendonite occurrences in ancient sedimentary sequences are widely considered to reflect near-freezing temperatures, even at high latitudes during periods of greenhouse climates. To fully understand the paleoenvironmental significance of glendonites, a comprehensive examination of the modern ikaite setting is necessary. Temperature is the most important parameter that has been quantitatively constrained for the presence of ikaite. Low bottom-water temperature, while a required condition for formation of the mineral, is not adequate for its growth; other controls are necessary to explain the absence of ikaite in many cold environments. In this ...

两种沉水植物对间隙水磷浓度的影响

两种沉水植物对间隙水磷浓度的影响

Linking Stoichiometric Homeostasis of Microorganisms with Soil Phosphorus Dynamics in Wetlands Subjected to Microcosm Warming

Soil biogeochemical processes and the ecological stability of wetland ecosystems under global warming scenarios have gained increasing attention worldwide. Changes in the capacity of microorganisms to maintain stoichiometric homeostasis, or relatively stable internal concentrations of elements, may serve as an indicator of alterations to soil biogeochemical processes and their associated ecological feedbacks. In this study, an outdoor computerized microcosm was set up to simulate a warmed (+5°C) climate scenario, using novel, minute-scale temperature manipulation technology. The principle of stoichiometric homeostasis was adopted to illustrate phosphorus (P) biogeochemical cycling coupled with carbon (C) dynamics within the soil-microorganism complex. We hypothesized that enhancing the flux of P from soil to water under warming scenarios is tightly coupled with a decrease in homeostatic regulation ability in wetland ecosystems. Results indicate that experimental warming impaired the ability of stoichiometric homeostasis (H) to regulate biogeochemical processes, enhancing the ecological role of wetland soil as an ecological source for both P and C. The potential P flux from soil to water ranged from 0.11 to 34.51 mg m−2 d−1 in the control and 0.07 to 61.26 mg m−2 d−1 in the warmed treatment. The synergistic function of C-P acquisition is an important mechanism underlying C∶P stoichiometric balance for soil microorganisms under warming. For both treatment groups, strongly significant (p<0.001) relationships fitting a negative allometric power model with a fractional exponent were found between n-HC∶P (the specialized homeostatic regulation ability as a ratio of soil highly labile organic carbon to dissolved reactive phosphorus in porewater) and potential P flux. Although many factors may affect soil P dynamics, the n-HC∶P term fundamentally reflects the stoichiometric balance or interactions between the energy landscape (i.e., C) and flow of resources (e.g., N and P), and can be a useful ecological tool for assessing potential P flux in ecosystems.

High-Resolution Profiles of Dissolved Reactive Phosphorus in the Porewaters of Lake Sediments Assessed by DGT Technique

The technique of DGT (diffusive gradients in thin films) was applied to obtain high-resolution vertical profiles of dissolved reactive phosphorus (DRP) in sediment porewater of Lake Chaohu, a shallow eutrophication lake. Three kinds of DGT probes (with three thicknesses of diffusive gel: 0.38 mm, 0.78 mm and 1.18 mm) measured vertical concentration and induced flux from solid to solution phase which had intricate variations with depth. The results indicated that higher concentrations and induced fluxes of DRP were achieved by using DGT probe with thicker diffusion layer (CDGT1.18 > CDGT0.78 > CDGT0.38) and relatively stable DRP concentration profiles using DGT probes with 0.78 mm diffusive gel were obtained in each sediment core. The DRP concentrations displayed a clear gradient from Core C1 to Core C3 in sediment porewaters due to different sources and exchange degrees of reactive phosphorus. Compared to the concentrations obtained by the centrifugation technique, the concentrations of DRP resulting from the DGT technique were higher because some dissolved reactive phosphorus compounds have always been neglected using conventional centrifugation method.

Dynamics of P-binding forms in sediments of a mesotrophic hard-water lake: Insights from non-steady state reactive-transport modeling, sensitivity and identifiability analysis

Sediments can act both as a source or sink of contaminants and nutrients in lakes. In this study, we developed a non-steady state reactive transport diagenetic model to gain insights into the dynamics of phosphorus binding forms in the sediments of Lake Simcoe, a mesotrophic hard-water lake located in Southern Ontario, Canada. We investigate three basins of the lake with differences in their phosphorus binding forms, reflecting the distinct spatiotemporal patterns of land use and urbanization levels in the watershed. In the model, total phosphorus is divided into loosely adsorbed phosphorus, phosphorus bound with aluminum, organic phosphorus, redox sensitive and apatite phosphorus, and dissolved phosphorus in pore water. Using the fluxes of organic and inorganic matter along with the concentrations of dissolved substances as dynamic boundary conditions, we simulated the depth profiles of sixteen solute and solid components. The model closely reproduced the fractionation data of phosphorus binding forms. The impact of the interplay between sedimentation fluxes and geochemical conditions on phosphorus diagenesis was then studied under a range of anthropogenic disturbances and natural variability in Lake Simcoe. We also conducted sensitivity analysis that pinpointed the most influential processes underlying the mechanistic foundation of the model. The non-steady state diagenesis model reveals that apatite P dominates the P forms in Cook's Bay, which has been overwhelmingly influenced by agricultural activities in the corresponding watershed during the last 100years. In contrast, Kempenfelt Bay has been primarily impacted by urbanization and experienced oxygen depletion in the deep water. Thus, we found that organic P binding forms dominated over redox sensitive P when urban loading was intensified. Finally, our study offers insights into the identifiability of the model as well as into the factors that will be critical to monitor in order to improve its credibility. The model outputs are sensitive to the concentrations of dissolved oxygen and pH at the sediment–water interface. The sensitivity with respect to these factors overwhelmingly dominates over all other parameters. Furthermore, the characterization of the sedimentation fluxes; namely, the composition of settling organic matter, expressed as the ratio of degradable to inert organic matter is the second strongest factor that can influence the inference drawn by our modeling exercise.

An investigation of submarine groundwater—borne nutrient fluxes to the west Florida shelf and recurrent harmful algal blooms

A cross‐shelf, water‐column mass balance of radon‐222 (222Rn) provided estimates of submarine groundwater discharge (SGD), which were then used to quantify benthic nutrient fluxes. Surface water and groundwater were collected along a shore‐normal transect that extended from Tampa Bay, Florida, across the Pinellas County peninsula, to the 10‐m isobath in the Gulf of Mexico. Samples were analyzed for 222Rn and radium‐223,224,226 (223,224,226Ra) activities as well as inorganic and organic nutrients. Cross‐shore gradients of 222Rn and 223,224,226Ra activities indicate a nearshore source for these isotopes, which mixes with water characterized by low activities offshore. Radon‐based SGD rates vary between 2.5 and 15 cm d−1 proximal to the shoreline and decrease offshore. The source of SGD is largely shallow exchange between surface and pore waters, although deeper groundwater cycling may also be important. Enrichment of total dissolved nitrogen and soluble reactive phosphorus in pore water combined with SGD rates results in specific nutrient fluxes comparable to or greater than estuarine fluxes from Tampa Bay. The significance of these fluxes to nearshore blooms of Karenia brevis is highlighted by comparison with prescribed nutrient demands for bloom maintenance and growth. Whereas our flux estimates do not indicate SGD and benthic fluxes as the dominant nutrient source to the harmful algal blooms, SGD‐derived loads do narrow the deficit between documented nutrient supplies and bloom demands.

Spatial and seasonal variability of pore water phosphorus concentration in shallow Lake Swarzędzkie, Poland

Pore waters play an important role in phosphorus dynamics in aquatic ecosystems. Phosphorus concentrations in pore waters are much higher than above the bottom. This is confirmed by the results of this study concerning the hypereutrophic lake. Pore water was analyzed at 11 sampling stations in the upper layer of bottom sediments. This water was separated by centrifugation and phosphorus level was measured spectrophotometrically with ascorbic acid as a reducer. Total phosphorus concentration in pore waters ranged from 0.5 to 8.1 mgP l(-1) (mean 3.2 mgP l(-1)). Mean phosphorus concentration in pore water samples of this lake was the highest in summer and the lowest in winter. High concentrations were observed in samples from the pelagial and low from the macrophyte zone.

Environmental effects of yellowtail kingfish aquaculture in South Australia

The culture of yellowtail kingfish Seriola lalandi in South Australia is one of the most rapidly growing aquaculture sectors in Australia. To date, there is a paucity of information on the environmental impacts of this industry, due to its relatively small size in comparison to other industry sectors. Here, we report on a study examining the response of a range of environmental variables to yellowtail kingfish aquaculture in Fitzgerald Bay, northern Spencer Gulf, South Australia. The clearest response occurred in several chemical variables, with an 81% increase in ammonia con- centrations adjacent to cages relative to controls, increased sediment organic carbon (7 to 46%) and increased porewater phosphorus in the sediments (80 to 3077%). While there were also statistically significant effects on infaunal and epifaunal assemblages, results for both groups were equivocal because of high small-scale variability. For the infauna, assemblages at the sites furthest from cages tended to be similar to those adjacent to cages, while those at intermediate distances differed. No impacts were detected on phytoplankton, or on seagrasses (although the latter only occurred >250 m from any aquaculture cage). The lack of clear responses in the biotic datasets is probably related to the relatively low production levels (<2000 t yr -1 at the time of the study), although the responses in the chemical variables provide a valuable early warning as production increases.

Determination of soluble reactive phosphorus in porewaters of sediments using the technique of diffusive equilibration in thin films

沉积物间隙水溶解态反应性磷(SRP)是反映沉积物磷地球化学特征的敏感指标,对其高分辨率获取一直是难点.基于薄膜扩散平衡(DET)原理,以琼脂糖为原料制备薄膜,通过平衡、切片、提取、测定等步骤,获得溶解态反应性磷的含量信息.实验确定薄膜在磷溶液中的平衡时间为24h,通过0.25mol/L硝酸提取16h可将薄膜萃取的磷提取完全.利用DET技术对不同沉积物间隙水SRP进行了分析,与实际浓度的差异在±5%以内;对沉积物剖面的分析结果与Rhizon、微型Peeper等采样技术基本一致,垂直分辨率可达到3mm左右.利用DET技术对太湖草型和藻型湖区沉积物间隙水SRP进行了分析,发现草型湖区间隙水剖面SRP呈峰形分布,且横向空间分异明显;藻型湖区间隙水SRP随沉积深度的增加呈升高趋势,扩散梯度随水温升高而增强.;Distribution of soluble reactive phosphate (SRP) in pore waters is a sensitive indicator showing geochemical properties ofphosphorus in sediments. Concentration of SRP in synthetic solutions was obtained based on the principle of diffusive equilibration inthin films (DET). Analytical procedure generally includes equilibration of the gels in solutions or pore waters, section of the gels afterretrieval, back elution of phosphorus in the gels, and analysis of SRP in the eluents. Equilibrium and extraction times weredetermined at 24h and 16h, respectively, with 0.25mol/L HNO₃ used as an extractant. Concentrations of SRP in pore waters ofdifferent sediments measured by using the established DET technique agree well with its actual values, and the variations aregenerally within ±5%. Analytical results for sediment profiles with this technique, which has a vertical resolution at about 3mm, alsoshow comparison with those using sampling techniques of Rhizon and Mini-Peeper. The established DET technique was used tomeasure SRP profiles in sediments of macrophyte- and algal-dominated regions in Lake Taihu. Peak-shape distribution and horizontalheterogeneity of SRP were observed in macrophyte-dominated region, while an upward and increasing movement of SRP wasobserved in algal-dominated region with an increase in water temperature.

Early diagenesis of inner-shelf phosphorite and iron-silicate minerals, Lower Cretaceous of the Orpheus graben, southeastern Canada: Implications for the origin of chlorite rims

Wells in the Orpheus graben encountered the most proximal part of the deltaic Lower Cretaceous rocks of the Scotian Basin. More distal sandstones are important gas reservoir rocks, with good reservoir quality where Fe-rich chlorite (chamosite) rims on framework grains have inhibited quartz cementation. Cutting samples from the Orpheus graben show the presence of Fe-rich sheet silicates (berthierine or chamosite) and early diagenetic phosphorite. These minerals were analyzed by electron microprobe, and their textures were mapped with backscattered electron images. Studies in the North Sea have shown a relationship between high phosphorus and the presence of good chlorite rims in reservoir rocks. The mineralization of pore-water phosphorus, instead of its return to seawater, is favored by Fe-rich sediments and sorption on iron oxides during shallow sea-floor diagenesis. The Fe, Ti, and P contents are uncommonly high in Scotian Basin shales compared with global average shale compositions. The uncommon occurrence of inner-shelf phosphorite in this study is interpreted to be a consequence of the same high Fe content of the sediment that also favors the formation of Fe-rich sheet silicates. In rapidly deposited deltaic sandstones of the offshore reservoirs, the dominance of type 3 kerogen led to sulfate depletion occurring at depths of tens of meters and a corresponding great thickness for overlying Eh (oxidation potential)-controlled diagenetic zones. The thick Fe-reduction zone allowed the formation of early diagenetic berthierine, which on burial formed the chamosite rims that resulted in the improved reservoir quality in sandstones. The distribution of phosphorus minerals may be an indicator of conditions suitable for berthierine formation.

Combined Gel Probes for the In Situ Determination of Dissolved Reactive Phosphorus in Porewaters and Characterization of Sediment Reactivity

Diffusive equilibrium in thin films (DET) and diffusive gradients in thin films (DGT) were applied in situ to obtain high spatial resolution dissolved reactive phosphorus (DRP) sediment porewater profiles in two lagoons of the Gippsland Lakes (SE Australia) during summer. Although the DRP depth profiles were different in each lake, highlighting the sensitivity of DRP to the redox state of the sediment spatial DRP variations obtained from DET and DGT showed striking similarities with depth in each lake. Comparison of DRP concentrations obtained from DGT and DET allows an assessment of the reactivity of the sediment. A dynamic numerical model of DGT-induced flux in sediments (DIFS) quantified reactivity kinetics. Sediment response time (Tc) related to sedimentary phosphorus resupply resulting from DGT-induced lowering of the porewater DRP concentration was calculated. Values of Tc ranged from 4128 to 183 400 s and from 55 to 149 400 s for Lakes Victoria and Wellington, respectively. These results indicate the limited capacity of the sediment to quickly resupply DRP to the porewater, especially in surface sediment which was always characterized by the highest Tc. Adsorption and desorption rate constants were also calculated from DIFS with values ranging from 2 x 10(-3) to 2 x 10(-2) day(-1) and from 0.3 to 21 day(-1) for Lake Victoria and from 2 x 10(-4) to 0.8 day(-1) and from 0.6 to 1558 day(-1) for Lake Wellington, respectively. Diffusive fluxes estimated from the in situ DRP gradient at the sediment-water interface by DET were 558 and 1.2 micromol m(-2) day(-1) in lakes Victoria and Wellington, respectively. Despite only a single measurement, these fluxes highlight a substantial contribution of P from the sediment to the water column in summer for Lake Victoria which is likely to contribute to the recurring blooms of blue-green algae. These calculated fluxes obtained with minimal sediment disturbance and high spatial resolution were substantially different (by a factor of 6-180) from other reported values using more conventional quantitative assessments such as diffusive fluxes (from core slicing) and benthic chambers.

Modeling interactions of submersed plant biomass and environmental factors in a stream using structural equation modeling

This study investigated the interactions of submersed plants with environmental factors using structural equation modeling (SEM) and evaluated the effect strength of respective factors in an aquatic ecosystem using a data set collected at a fourth order stream in Japan. A model that simultaneously examines the relative importance of factors of the system has developed. The investigated factors included plant biomass (Biomass) of submersed macrophytes (Potamogeton malaianus and Potamogeton oxyphyllus) and other environmental factors, i.e. water velocity and water depth (Hydraulic), pore water nitrogen (TNL), pore water phosphorus (TPL), sediment organic matter (Organic) and sediment particle size (Texture). The estimated model showed that the Biomass was negatively correlated with Hydraulic but positively correlated with Organic whilst TNL and TPL affected the Biomass with almost equal strength. The effects caused by Hydraulic to Texture were greater than the ones caused by Biomass. At the narrow ranges of water velocity (0–7 cm s−1) and shallow depth (0–35 cm), the effect of wash-away of Organic by Hydraulic were smaller than the retention effect of Organic by Biomass. These results provide more insights into interactions of the submersed macrophytes with environmental factors.

Experimental study on phosphorus release from sediments of shallow lake in wave flume

Influence of wave on sediment resuspension and nutrients release from sediments, collected from Lake Taihu and Lake Chaohu, was studied in flume experiments. Under strong-wave conditions, concentrations of suspended solids (SS), total phosphorus (TP) and dissolved total phosphorus (DTP) in overlying water were increased significantly following the sediments re-suspension. During the experiments on sediments of Lake Taihu and Lake Chaohu, TP concentrations increased 6 times and 3 times, and DTP concentration increased 100% and 70% more than it in presuspension, respectively. Concentration of soluble reactive phosphorus (SRP) of experiment on sediment of Lake Taihu increased 25%. During the massive sediment suspension, the dissolved phosphorus in pore water and much of the phosphorus adsorbed by the sediment particles were released into overlying water. The phenomena in this wave flume experiment are quite similar to the situation observed in situ of Lake Taihu. The critical wave stresses of sediment re-suspension are nearly equal. The change of concentrations of SS, TP, and SRP was the same as that in situ situation. This study showed that concentrations of TP and SRP in lake water could be increased significantly by wave disturbance. Phosphorus release was significantly enhanced by wave disturbance at the beginning of massive sediment re-suspension, but decreased later.

Impact of Macrozoobenthos on Two-Dimensional Small-Scale Heterogeneity of Pore Water Phosphorus Concentrations: in-situ Study in Lake Arendsee (Germany)

An in-situ study was conducted in Lake Arendsee to study the influence of macrozoobenthos on pore water phosphate concentrations, and to investigate the importance of macrozoobenthos in causing small-scale heterogeneity. Two-dimensional pore water samplers with a high spatial resolution were exposed for 14 days at two sampling points with different water depths. Macrozoobenthos densities and the corresponding pore water phosphate concentrations were determined. In profundal sediments with chironomids (mean density: 480 m−2) the pore water phosphate concentration showed more patchiness (heterogeneity index 0.69) than in sediments without chironomids (heterogeneity index 0.38). Macrozoobenthos might affect the sediment environment mainly through bioirrigation, bioturbation, secretion, and digestion. It is most likely that the hot spots are caused by secretions from chironomids which intensify the microbially mediated P-release. The small-scale horizontal heterogeneity of pore water concentrations due to macrozoobenthos activities is insufficiently considered in many limnological studies focusing on vertical changes of pore water concentrations to investigate biogeochemical processes in sediment and to estimate internal nutrient loading. In sediments inhabited by macrozoobenthos the number of replicates should be high due to the extreme variability of single profiles of the two-dimensional sampler, as well as of averaged profiles simulating classical one-dimensional pore water analysis techniques. In cases where the profundal sediment is macrozoobenthos-free, single deployments of one-dimensional pore water samplers are well suited to describing pore water chemistry. Thus, determination of macrozoobenthos density is essential for study design.