Interstitial Water Samples Research Articles

Spatial distribution of sediment dissolved organic matter in oligotrophic lakes and its binding characteristics with Pb(II) and Cu(II).

Dissolved organic matter (DOM), the most active component in interstitial waters, determines the stability of heavy metals and secondary release in sediments. However, little is known about the composition and metal-binding patterns of DOM in interstitial water from oligotrophic lakes affected by different anthropogenic perturbations. Here, 18 interstitial water samples were prepared from sediments in agricultural, residential, tourist, and forest regions in an oligotrophic lake (Shengzhong Lake in Sichuan Province, China) watershed. Interstitial water quality and DOM composition, properties, and Cu(II)- and Pb(II)-binding characteristics were measured via physicochemical analysis, UV-vis spectroscopic, fluorescence excitation-emission matrix-parallel factor analysis (EEM-PARAFAC), and fluorescence titration methods. The DOM, which was produced mainly by microbial activities, had low molecular weights, humification degrees, and aromaticity. Based on EEM-PARAFAC results, the DOM was generally composed of tryptophan- (57.7%), terrestrial humic- (18.7%), microbial humic- (15.6%), and tyrosine-like (8.0%) substances. The DOM in the metal complexes was primarily composed of tryptophan-like substances, which accounted for ~42.6% of the DOM-Cu(II) complexes and ~72.0% of the DOM-Pb(II) complexes; however, microbial humic-like substances primarily contributed to the stability of DOM-Cu(II) (logKCu = 3.7-4.6) and DOM-Pb(II) (logKPb = 4.3-4.8). Water quality parameters did not significantly affect the stability of DOM-metal complexes. We demonstrated that the metal-binding patterns of DOM in interstitial water from oligotrophic lakes are highly dependent on microbial DOM composition and are affected by anthropogenic perturbations to a lesser extent.

Changing Sub‐Surface Chemistry Resulting From a 26‐Million‐Year Unconformity: Porewater Chemistry From IODP Site U1553 in the South Pacific

AbstractWhereas changes in pore water chemistry are known to impact carbonate sediment geochemistry, little is known about the impact of long unconformities on carbonate alteration. IODP Site 378‐U1553 on the southern Campbell Plateau, with a 26‐million‐year, erosional unconformity, provides a key location for examining the impact of long‐term unconformities on sub‐surface chemistry and carbonate archives. This study examined 76 interstitial water samples for sulfate sulfur and oxygen isotopes, as well as 28 bulk carbonate samples for carbonate associated sulfate (CAS) sulfur isotopes, to quantify the effects of this unconformity on the sub‐surface redox chemistry of the Site. The current state of the system suggests limited influence of redox processes on the CAS archive. Manganese reduction reaches 30 mbsf, with a decrease in manganese reduction between 20 and 30 mbsf. Below 30 mbsf, the system transitions to iron reduction to a depth of approximately 140 mbsf where sulfate reduction begins. Dissolved sulfate sulfur and oxygen isotope values suggest repeated oxygenation of sulfides. The CAS record from the Site deviates from previously published seawater values. However, the lack of a relationship between the dissolved sulfate and CAS records suggests most of the alteration of the CAS record likely occurred before the unconformity when the carbonate sediments were more reactive. This further supports the CAS record as a relatively robust archive, withstanding most post‐depositional mechanisms of carbonate alteration.

Disposition of trace elements in the mangrove ecosystem and their effects on Ucides cordatus (Linnaeus, 1763) (Crustacea, Decapoda).

The tropical mangrove at the Estação Ecológica do Lameirão (Southeastern Brazil), an ecosystem of high socio-economic value, receives a large load of pollutants from domestic, industrial, and agricultural sources. Samples of interstitial water, sediments, and crustacean specimens were collected at different periods and regions throughout the study area to measure the concentrations of copper (Cu), cadmium (Cd), lead (Pb), and tin (Sn) along the mangrove, as well as the bioaccumulation behavior in the crab Ucides cordatus. Subsequently, we correlated the accumulation of metals in U. cordatus with the concentrations of metals in the environment and physicochemical and climatic factors. Furthermore, we compared the bioconcentration factors (BFCs) of trace elements with the concentration levels obtained from the mangrove sediment. The fluctuation of rain and tide throughout the study period caused oscillations in the concentrations of trace elements. This condition induced bioconcentration records (BFC > 1), influencing the bioaccumulation trend in U. cordatus. We also identified that the lowest metal concentration values in the sediment were close to the river, indicating that the rivers cause a dilution effect. Finally, we found that the hepatopancreas had the highest levels of bioaccumulated heavy metals, explained by its detoxifying ability. In females of U. cordatus, we found a slightly lower accumulation of trace elements when compared to males, possibly related to the high rate of ecdysis in females. Ucides cordatus is a species widely used for human consumption. Our results show that the mangrove environment influences the concentration of trace elements in this organism, which the authorities should consider in mapping safer fishing areas.

DETERMINACIÓN DE LA DISTRIBUCIÓN DE CONTAMINANTES EMERGENTES EN AGUA INTERSTICIAL EN SEDIMENTOS DE HUMEDAL MEDIANTE LA OPTIMIZACIÓN Y VALIDACIÓN DE UN MÉTODO ANALÍTICO

The present work shows the methodology (study of a method) for the analysis of four emerging pollutants. Each studied pollutant represents a family from emerging pollutants (an estrogenic compound, an antibacterial, a pharmaceutical and a fragrance). The method was optimized to be used in a complex environmental matrix such as sediment interstitial water of a wetland with high organic matter content. The extraction of the compounds was carried out by solid phase extraction technique and quantified by gas chromatography with mass spectrometry in single ion monitoring mode. The method was validated using the “Single Laboratory Method Validation Process” through the determination of the performance parameters of the method. The optimized method was applied to the analysis of sediment interstitial water from the canals of the periurban agricultural zone of Xochimilco, Mexico. This preliminary study showed that the sampling point close to the wastewater discharge area from the secondary treatment wastewater plant had the highest concentration of emerging pollutants. Also, an inversely proportional relationship was observed between the concentrations of ibuprofen and musk with the concentration of organic matter in the sediments. The optimization of the method and the ratification with sediment interstitial water samples from the wetland, showed the worthiness of the method for the evaluation of the presence and distribution of emerging pollutants.

Advances and prospect in sediment-water interface of lakes: A review

湖泊沉积物-水界面是以水层/沉积层物相为基础、具有一定立体尺度的交接面，界面上所发生的由生物积极参与的物理、化学和生物学微小反应和环境变化，都会对界面附近物质的状态和迁移转化行为产生着复杂影响.本文首先回顾了沉积物-水界面研究100多年来的发展历程及国内外近20年发展.然后系统介绍了国际上对沉积物-水界面的物理尺度与结构的宏观和微观认识；重点综述了沉积物间隙水的取样、物化性质的多维测定与结构表征、过程的静态和动态模拟等湖泊沉积物-水界面研究技术与方法；分析和展示了氮磷等营养物、重金属和持久性有机污染物在湖泊沉积物-水界面迁移转化过程的研究进展；总结和归纳了在沉积物-水界面过程的模型研究、沉积物-水界面物质交换的定量化、界面过程与湖泊生态环境灾害关系等模型与过程效应方面的研究成果.最后对沉积物-水界面信息获取技术的研发方向、界面物质交换定量化研究的关注点，以及加强模型的应用和构建等方面进行了展望.;The sediment-water interface in freshwater lakes is a three-dimensional interface based on the water/sediment facies. The micro-reactions, which are actively participated by organisms, and micro-environmental changes of physical, chemical and biological reactions on the interface will have a complex impact on the state and migration-transformation behavior of substances near the interface. In this paper, the courses of sediment-water interface research in the past 100 years, especially the development in the recent 20 years, both at home and abroad are reviewed from a comprehensive perspective. Firstly, the international macro-and micro-understanding of the physical scale and structure of sediment-water interface is introduced. The techniques and methods applied in the aquatic sediment-water interface research and practice, which are the sampling of interstitial water, multi-dimensional measurement of physicochemical properties in sediments and their structure characterization, static/dynamic processes simulation and others are selected for detailed analysis. Moreover, the advances on the migration and transformation process of phosphorus and nitrogen and other nutrients, heavy metals and persistent organic pollutants in aquatic sediment-water interface are discussed, especially in respects of modelling study of sediment-water interface process, quantification of substance exchange across the sediment-water interface, and relationships between the interface processes and lake eco-environmental disasters. Finally, the development trend for the future research of information acquisition technology for sediment-water interface analysis, the focus of quantitative research on interfacial substance exchange, and the application and construction of more efficient models etc. are favorably suggested.

Contenido nutrimental en hojas de Laguncularia racemosa (Combretaceae), relacionado con su fenología en una laguna tropical del Golfo de California, México

Antecedentes y Objetivos: Los eventos fenológicos en manglares suelen estar influidos por factores como la salinidad del agua, fotoperiodo y/o temperatura ambiental. Esto se ha documentado principalmente para especies de la familia Rhizophoraceae y Acanthaceae; sin embargo, son limitados los estudios accesibles para la familia Combretaceae, p. ej. Laguncularia racemosa.Métodos: Se colectaron durante un año, mensualmente, de tres a cuatro hojas del antepenúltimo y penúltimo entrenudo de las ramas de 10 árboles de Laguncularia racemosa. La colecta de hojas se realizó teniendo en cuenta ocho etapas fenológicas. Los nutrientes analizados en las hojas fueron: N total, PO, K+, Ca2+, Mg2+, SO, Na+, Fe2+, Cu2+, B (H3BO3), Mn2+ y Zn2+. Adicionalmente, 10 muestras de agua intersticial (para medir iones mayores) y sedimento (para medir el pH y cuantificar el contenido de materia orgánica) se tomaron a una profundidad de entre 0.3 a 0.6 m.Resultados clave: Los nutrientes K+, Ca2+, Fe2+, Mg2+, y N total presentaron valores máximos a lo largo del desarrollo de la brotación vegetativa hasta el desarrollo de “frutos”, lo cual significa que la mayor importancia de estos nutrientes es en la producción de “frutos”. El Na+ mostró su mayor concentración (22.8 g kg-1) en la fase de inicio de floración y la mínima durante la quiescencia (8.7 g kg-1). En contraste, el SO, PO, Cu2+, B (H3BO3), Zn2+ no presentaron diferencias. Finalmente, el Mn2+ presentó 109 mg kg-1 al final de la brotación vegetativa y 34 mg kg-1 en la madurez y caída de “frutos”.Conclusiones: En la absorción de nutrientes son importantes las etapas fenológicas y las condiciones climáticas locales.

Characteristics of Nitrogen Release at the Sediment-Water Interface in the Typical Tributaries of the Three Gorges Reservoir During the Sensitive Period in Spring

Overlying water and sediment interstitial water samples were acquired to study the nitrogen release between sediments and water interfaces in Xiangxi Bay in April 2016 during the Sensitive Period in spring. The spatial distribution of different forms of nitrogen in the sediment was analyzed, the diffusion fluxes of different forms of nitrogen in the sediments and water systems were also measured, and a correlation analysis with environmental factors was conducted. The results show that overlying water and sediment interstitial water ρ(TN) ranges from 1.10 to 6.90 mg·L-1 and 6.19 to 32.57 mg·L-1 respectively; indicating the nitrogen concentrations in the overlying and interstitial water of sediments have a certain variation along the process and vertically. The interstitial water nitrogen concentrations in the upstream area are higher than those in the downstream area. The interstitial water ρ(NH4+-N) in the sediment is significantly larger than that in the overlying water, but the interstitial water ρ(NO3--N) in the sediment is slightly smaller than that in the overlying water. Xiangxi Bay sediment acts as a source of NH4+-N; however, for NO3--N it is a sink. The diffusive fluxes of NH4+-N range from 2.70 to 4.72 mg·(m2·d)-1; and the diffusive fluxes of NO3--N range from -1.61 to -0.62 mg·(m2·d)-1. Nitrogen is mainly present in the form of ammonium nitrogen in the sediment of Xiangxi Bay. The ρ(NH4+-N) in the sediment ranges from 69.97-1185.97 mg·kg-1, ρ(NO3--N) ranges from 2.78-38.17 mg·kg-1, and the ρ(NH4+-N) in sediments in the surface at 0-8 cm changes with the same trend.

Environmental forcing of intertidal benthic macrofauna of Bodo Creek, Nigeria: Preliminary index to evaluate cleanup of Ogoniland

Pristine and before-disturbance baseline data are essential tools in monitoring and measurement of progress and net success or otherwise of restoration of degraded ecosystems. These are usually lacking in regions such as the Niger Delta where demands for such data is pressing due to impending pollution. We present a rare case of available pre-spill data of how distribution and abundance of macrobenthic infauna were structured by some physical and chemical variables of interstitial water in Bodo Creek, lower eastern Niger Delta, Nigeria, before two major oil spills impacted the creek in 2008. Monthly composite samples of macrobenthos and interstitial water in four soft-bottom unvegetated intertidal flats were analysed for one year. Thirty six taxa, twenty-two families and four classes of macrozoobenthos were recorded. The bivalves Lorepis aberrans, Macoma innominata, Senilia senilis, and polychaetes Nereis diversicolor, N. virens, N. pelagic and Clymenella torquata were eurizonal in distribution and abundant, attaining sub-dominant and dominant status at the sites. The observed pattern of reduction in rainy season macrofauna abundance in some river systems of the Niger Delta due to sediment instability was counterbalanced by increased recruitment of the dominant taxa. Canonical Correspondence Analysis (CCA) showed the explanatory (physicochemical) variables only accounted for 31.8% of variation in the species data. The species–environmental correlations were: 0.64, 0.74 and 0.72 for the first, second and third axes, respectively. Plans for cleanup, remediation and ‘restoration’ of Bodo Creek, have reached implementation stage as the Federal Government of Nigeria flagged off cleanup of Ogoniland on June 2, 2016. The usefulness of these data as potential template for monitoring and evaluation of water quality response to the proposed cleanup and restoration is highlighted.

Water geochemistry of shallow lakes from the southeastern Pampa plain, Argentina and their implications on mollusk shells preservation

A seasonal sampling of sediments, column and interstitial water for physico-chemical analysis were performed in littoral and open water areas in three freshwater shallow lakes (Nahuel Rucá, Las Mostazas and Los Carpinchos) from Southeastern Pampa plain, Argentina. The main objective of the present study is to evaluate how the characteristics of the depositional environments could be affecting mollusk shell preservation. These lakes are very shallow (2m) and are characterized by an extensive littoral area, dominated by the emergent macrophyte Schoenoplectus californicus, which forms a complete ring around the lake, and an open water area, in general free of vegetation. Five samples of sediments in each compartment were extracted for analysis of pH, moisture, organic matter and carbonates content using a gravity corer, while five samples from column and interstitial water were extracted for chemical analysis (pH, conductivity, major ions, minor ions and hardness). Besides, calcite and aragonite saturation indices and the redox potential were calculated for each lake. The results show the significant impact of water chemistry and redox conditions on the preservation potential of freshwater mollusk and consequently in the quality of paleonvironmental reconstruction based on the biological record from the study region. The higher concentration of organic matter and lower pH registered in the littoral area, mainly during warm months (autumn and summer), suggest worst environments for mollusk preservation, compared to open waters. Moreover, water geochemistry analysis showed aragonite and calcite indices near equilibrium or slightly subsaturated in interstitial water associated with more acid pHs, while column water is strongly oversaturated related to alkaline pHs. These results suggest that carbonate remains within sediments will be subject to dissolution affecting negatively their preservation potential. However, mollusk shells in contact with the column water are not expected to be dissolved.

Functionality of microbial communities in constructed wetlands used for pesticide remediation: Influence of system design and sampling strategy

The objective of this study was to compare the microbial community metabolic function from both unsaturated and saturated constructed wetland mesocosms (CWs) when treating the pesticide tebuconazole. The comparison was performed for both interstitial water and substrate biofilm by community level physiological profiling (CLPP) via BIOLOG™ EcoPlates. For each CW design (saturated or unsaturated), six mesocosms were established including one unplanted and five planted individually with either Juncus effusus, Typha latifolia, Berula erecta, Phragmites australis or Iris pseudacorus. Microbial activity and metabolic richness of interstitial water from unsaturated CWs were significantly lower than that from saturated CWs. However, in general, the opposite result was observed for biofilm samples. Wetland plants promoted significantly higher biofilm microbial activity and metabolic richness than unplanted CWs in both CW designs. Differences in the microbial community functional profiles between plant species were only found for saturated CWs. Biofilm microbial metabolic richness was generally statistically higher than that of interstitial water in both unsaturated (1.4–24 times higher) and saturated (1.2–1.7 times higher) CWs. Carbon source (guild) utilization patterns were generally different between interstitial water and biofilm samples. Functionality of the biofilm microbial community was positively correlated to the removal of all pollutants (TN, NH4+-N, TP, TOC and tebuconazole) for both unsaturated and saturated CWs, suggesting the biofilm plays a more important role in pollutant removal than the interstitial water microbial community. Thus, merely observing the interstitial water microbial communities may underestimate the role of the microbial community in CW performance. Interestingly, the ability for the biofilm microbial community to utilize amino acids and amines/amides was positively correlated with tebuconazole removal in all system types.

Pore Water Collection, Analysis and Evolution: The Need for Standardization.

Investigating the ecological impacts of contaminants released into the environment requires integration of multiple lines of evidence. Collection and analysis of interstitial water is an often-used line of evidence for developing benthic exposure estimates in aquatic ecosystems. It is a well-established principle that chemical and toxicity data on interstitial water samples should represent in-situ conditions; i.e., sample integrity must be maintained throughout the sample collection process to avoid alteration of the in-situ geochemical conditions. Unfortunately, collection and processing of pore water is not standardized to address possible geochemical transformations introduced by atmospheric exposure. Furthermore, there are no suitable benchmarks (ecological or human health) against which to evaluate adverse effects from chemicals in pore water; i.e., empirical data is lacking on the toxicity of inorganic contaminants in sediment interstitial water. It is clear that pore water data is best evaluated by considering the bioavailability of trace elements and the partitioning of contaminants between the aqueous and solid phases. It is also evident that there is a need for sediment researchers and regulatory agencies to collaborate in developing a standardized approach for sediment/pore water collection and data evaluation. Without such guidelines, the number of different pore water collection and extraction techniques will continue to expand, and investigators will continue to evaluate potentially questionable data by comparison to inappropriate criteria.

Anthropic effects on the meiofauna and physicochemical characteristics of the hyporheic zone in a Mediterranean stream

We examined the effects of the discharge from a wastewater treatment plant (WWTP) on the interstitial water chemistry and structure of the hyporheos in two sections of the La Tordera stream, one upstream and one downstream of the effluent from the treatment plant. Interstitial water samples were collected to determine the vertical hydraulic gradient (VHG) and hydraulic conductivity (K) at six sites in each of the two sections on six occasions between November 2006 and September 2007. Samples of the interstitial meiofauna were collected in upwelling zones in both sections of the river. There were no patterns in the hydraulic gradient either in its direction or its magnitude along the longitudinal axis. There were no differences in VHG recorded at the sites sampled indicating that the two sections were similar in terms of geomorphology. The hydraulic conductivity was greatest in the control section (upstream of the effluent) of the stream. There were no significant differences in specific conductance, phosphates, nitrates or ammonia in the upwelling and downwelling zones. In the upwelling zones in the section of the river downstream from the effluent the concentrations of nitrates were greater than in the downwelling zones, but levels of phosphates and ammonia were lower. There was a decrease in the interstitial nutrient concentrations along a longitudinal gradient downstream of the effluent. A total of 24 taxa were collected from the hyporheos, with Chironomids and Oligochaetes being the most abundant groups. A higher Shannon diversity index (2.86) was recorded in the downstream section of the river even though a greater taxa richness (18) was recorded in the control section. This is probably due to the fact that a larger number of rare or unusual species was found in this section. According to the BMWP biological index the water quality in the control and downstream sections was polluted and heavily polluted, respectively. The shifts in hydraulic exchange processes and the bio-physicochemical environment of the hyporheic zone are the main effects of the discharge from the Santa Maria Palautordera wastewater treatment plant on the two sections of the river studied.

Venerupis decussata under environmentally relevant lead concentrations: Bioconcentration, tolerance, and biochemical alterations.

The edible clam Venerupis decussata is widely distributed in European aquatic systems, some of which are under strong anthropogenic pressure, which can contribute to trophic transfer of xenobiotics to humans. Accordingly, the present study focused on the tolerance, bioconcentration, and biochemical responses of V. decussata after exposure to ecologically relevant concentrations of lead. Health risks to humans after consumption of clams was also explored. An acute toxicity assay (96 h) was conducted with wild clams, using Pb exposure concentrations ranging from 0 mg L(-1) to 1.80 mg L(-1). Lethality, bioconcentration factor (BCF), intracellular partitioning, and a relevant set of biomarkers were used as endpoints. Clams, interstitial water, water column, and sediment samples were collected to analyze Pb concentration. The Pb concentration in wild clams was below international consumption guidelines. Under laboratory conditions, clams revealed high sensitivity to Pb (median lethal concentration of 0.65 mg L(-1)), with a high bioconcentration ability (bioconcentration factor > 1) during exposure. The intracellular partitioning data showed that most of the Pb had accumulated in the insoluble fraction (>80%). Several significant biochemical changes were observed, namely on catalase and glutathione-S-tranferase activities and metalothionein content. Overall, it was demonstrated that the European clam has a reduced tolerance to Pb, compared with other bivalves. However, consumption of clams from the Ria de Aveiro lagoon (Portugal) does not raise public health concerns in terms of Pb.

Accuracy of Lysimeters for Dissolved Copper, Antimony, Lead, and Zinc Sampling under Small Arms Backstop

Three assays were conducted to evaluate the reliability of lysimeters in detecting concentrations of Cu, Pb, Sb, and Zn in interstitial water of the vadose zone. Two box lysimeters (BLs) made from polyvinyl chloride (PVC) and polyvinylidene fluoride (PVDF) and three tension lysimeters (TLs) of different types were used. Assays were conducted with two concentrations of dissolved metals, undiluted and diluted in a 1:10 ratio, and at three different pHs. The assays were made to evaluate the sorption induced by the lysimeter material itself, by standard quartz sand added to the BLs, and by two types of glass beads placed around the porous cup of the TLs. Generally, BLs were more suitable for interstitial water sampling than TLs. Among the TLs, the one made of nylon was more reliable than the two others. Box lysimeters are a good choice to obtain accurate and comparable results for Cu, Pb, Sb, and Zn analysis. However, they have to be backfilled with natural soil found at the exact location of the lysimeter and not with standard quartz sand. Nylon TLs can also be used for water sampling for Sb, Pb, and Zn analysis but not for Cu. Glass beads may interact with dissolved metals and their use around the suction cup in TLs can be avoided by using the fine fraction of natural sediments (<125 μm) found at the location of the porous cup. Water samples from TLs do not need to be filtered for dissolved metal analysis because they are already filtered by the porous cup.

Rhizon sampler alteration of deep ocean sediment interstitial water samples, as indicated by chloride concentration and oxygen and hydrogen isotopes

AbstractDespite their potential to inform past ocean salinity, δ18O, and temperature, high‐resolution depth profiles of interstitial water chloride concentration and hydrogen and oxygen isotopes exist in very few locations. One of the primary limitations to the recovery of these depth profiles is that traditional interstitial water sampling requires 5–10 cm whole rounds of the sediment core, which has the potential to interfere with stratigraphic continuity. The Rhizon sampler, a nondestructive tool developed for terrestrial sediment interstitial water extraction, has been proposed for efficient and nondestructive sampling of ocean sediment pore waters. However, there exists little documentation on the reliability and performance of Rhizon samplers in deep ocean sediments, particularly in regard to their effect on chloride concentration and oxygen and hydrogen isotopic measurements. We perform an intercomparison of chloride concentration and oxygen and hydrogen isotopic composition in samples taken using traditional squeezing versus those taken with Rhizon samplers. We find that samples taken with Rhizons have positive biases in both chloride concentration and stable isotopic ratios relative to those taken by squeezing water from sediments in a hydraulic press. The measured offsets between Rhizon and squeeze samples are consistent with a combination of absorption by and diffusive fractionation through the hydrophilic membrane of the Rhizon sampler. These results suggest caution is needed when using Rhizons for sampling interstitial waters in any research of processes that leave a small signal‐to‐noise ratio in dissolved concentrations or isotope ratios.

Dissolved nutrients (NO3-N and PO4-P) and Fe in the interstitial and overlying waters of two tropical freshwater lakes in Southern Kerala, India

Studies on the geochemical reactions between sediments and overlying waters of freshwater systems have received considerable attention in the past few decades as these reactions impart significant changes in the quality of overlying waters. Although many studies are available in the global scientific scenario, not much effort has been made in India and practically very little information is available about Kerala, a state endowed with numerous lakes and backwaters. Here we report the level variabilities of dissolved nutrients such as NO3-N and PO4-P, and Fe in the surface, bottom and interstitial waters of the Sasthamkotta and Vellayani lakes– two important perennial freshwater sources in southern Kerala. Further the Lake Sasthamkotta, the largest fresh water lake of Kerala, is declared as a Ramsar site of international importance. NO3-N, PO4-P and Fe exhibit marked increase in the interstitial water compared to overlying waters. Among these two lake systems, the content of NO3-N is higher in the Vellayani lake than the Sasthamkotta lake, whereas the concentrations of PO4-P and Fe are marginally higher in the overlying waters of the Sasthamkotta lake. However the interstitial water samples of Vellayani lake record higher PO4-P and Fe values. Although fertilizer intensive agricultural activities around the lake systems are one of the major causative factors for the enhanced concentrations of nutrients in the overlying waters, early diagenetic release of nutrients and Fe also plays a pivotal role in enriching these hydrochemical signals in the lake systems.

Preliminary results for geochemical analysis of interstitial water samples from IODP Expedition 343 (JFAST)

Preliminary results for geochemical analysis of interstitial water samples from IODP Expedition 343 (JFAST)

Stable isotope geochemistry of pore waters and marine sediments from the New Jersey shelf: Methane formation and fluid origin

Interstitial water and sediment samples of Integrated Ocean Drilling Program (IODP) Expedition 313 (New Jersey Shallow Shelf) were analyzed for chemical composition and stable isotope ratios. The analyses indicate a previously unknown complex geometry of the underlying fresh-water lens with alternating fresh-water–salt-water intervals divided by sharp boundaries in the upper part of the cores. Three fluid sources were identified: (1) meteoric fresh water, (2) marine seawater, and (3) brine. The pore-fluid stable isotope values define a mixing line with end members that have δ18O and δ2H values of –7.0‰ and –41‰ for fresh water, and –0.8‰ and –6‰ for salt water, respectively. This is similar to the modern mean value of New Jersey precipitation and today’s New Jersey shelf water. For fresh water, this either indicates modern meteoric recharge via aquifers that crop out on mainland New Jersey or emplacement at a time with climatic and hydrologic conditions similar to modern. An origin from Pleistocene glacial meltwaters with depleted isotope values is not confirmed by stable isotope data of this study. Salt water also represents modern isotope values suggesting an infiltration along permeable, coarse-grained sandy units. The lower core parts are characterized by mixing with brine fluids that originate from evaporites in the deep underground. Stable carbon isotope analyses of gas and fluids prove the existence of methane formation from degradation of marine organic matter and CO2 reduction in the lower core parts below ∼350 m below seafloor. Methane concentrations above 10000 ppm and δ13Cmethane values of ∼–80‰ were measured. Methane formation is also indicated by authigenic carbonates with low δ13Ccarbonate values. Although not reaching the surface at present conditions, the venting out of variable fluxes of methane from passive continental margins due to sea-level fluctuations is significant for the long-term carbon cycle. Authigenic carbonates indicate the precipitation from pore fluids with marine oxygen stable isotope ratios at low temperatures. The geochemical data and interpretations presented in this study supply the missing link between existing onshore and offshore data and may provide the basis for an integrated approach to construct a geochemical transect across the New Jersey shallow shelf.

Major cation/chlorine ratio and stable chlorine isotopic compositions of sediment interstitial water in the Brazos-Trinity Basin IV from the Gulf of Mexico (IODP 308)

Interstitial water from the Integrated Ocean Drilling Program Expedition 308 (IODP 308), drilling in the Brazos-Trinity Basin IV on the slope of Gulf of Mexico, were analyzed for major anion and cation concentrations and δ37Cl isotopic compositions. In the Brazos-Trinity Basin IV, interstitial water samples from the Hole U1319 show chlorine content mostly centering around 560mM, and δ37Cl values from −0.81‰ to +0.71‰ with an average of −0.18‰, which are close to the seawater values (0‰). Integrated with the Na/Cl and Br/Cl ratios, the low δ37Cl of interstitial water show no relationship with the dissolution of halite or addition of relict brine. The concentrations of K+, Na+, Ca2+ and Mg2+ in the interstitial water show a similar decreasing pattern at shallow depths, reaching minima at ∼13.5m, corresponding to the alkalinity maximum. Relationships between alkalinity and Na+, K+, Ca2+, Mg2+ concentrations suggest that only Ca2+ concentration being controlled by the precipitation of diagenetic carbonates, while Na+, K+ and Mg2+ concentrations can be used as a geochemical indicator to reveal the fluid processes in the sedimentary basin. Abnormity low Na/Cl, K/Cl, and Mg/Cl ratios of interstitial water show a strong link to well-known cycles of sea level change to well imaged deposits in the fill of Brazos-Trinity Basin IV, which suggests that a lateral fluid with low cation/Cl ratios was probably intruded in the sediment strata during low stand sea level period in the basin.

The effects of stream substratum texture on interstitial conditions and bacterial biofilms: Methodological strategies

Hyporheic substrates play a key role in aquatic ecosystems, and increasing loads of fine sediment are considered one of the major threats to stream ecosystems. Knowledge concerning the interaction of stream substratum properties with habitat quality and microbial community structure is essential for a comprehensive understanding of the functionality of the hyporheic zone. To date, there is a lack of optimal field sampling methods for hyporheic microbial communities in streams. We systematically tested the effects of defined substratum textures on the physicochemical properties of interstitial water and on bacterial communities utilising T-RFLP fingerprinting. We also tested the representativeness of different methodological approaches of investigating bacterial diversity comparing sampling of substratum, interstitial water, and exposed coupons made of granite, carbonate and glass. The temporal development of physicochemical habitat characteristics in the interstitial zone, especially of fish-toxic nitrogen compounds and oxygen supply, significantly depended on substratum texture and was strongly correlated with bacterial community composition. Multivariate analyses of bacterial community data indicated strong differences in community composition between direct (substratum samples) and indirect (interstitial water samples, coupons) sampling strategies. Substratum samples yielded highest richness of operational taxonomic units (OTUs) and the most pronounced temporal dynamics of bacterial community composition. Consequently, this technique appears most representative for assessing bacterial community structure and diversity in hyporheic habitats. The observed couplings between substratum texture, physicochemical habitat conditions and bacterial community structure expand current knowledge of previously described negative effects of fine sediments on taxa from higher levels of biological organization.