Interstitial Water Samples Research Articles

Amino acids in interstitial waters of marine sediments

DISEQUILIBRIA within the mixture of organic matter, mineral particles and seawater in near-surface sediments result in extensive reaction, often biologically mediated. Variations in interstitial water composition are very sensitive indicators of the chemical and biological reactions in this zone of transition and the interaction between the water column and the permanent deposit1,2. Although most studies have been confined to inorganic ions, the few measurements of pore water DOC in marine sediments3–6 show large gradients in dissolved organic matter concentration within sediments and across the sediment–water interface. We describe here our study of dissolved amino acids in interstitial waters, which were used to trace some of the biogeochemical processes affecting organic matter in marine sediments. We have analysed the dissolved free amino acids in 15 interstitial water samples from four cores obtained in Buzzards Bay, Massachusetts; the Gulf of Maine; and the North-west Atlantic continental rise. These pore waters have very high amino acid concentrations, of the order of 1 mg l−1. In addition, the distribution of individual amino acids differs substantially from that reported for seawater7,8, particularly in the large relative abundance of glutamic acid and β-aminoglutaric acid. β-aminoglutaric acid (HOOCCH2CH(NH2)CH2COOH) is an isomer of glutamic acid which, to our knowledge, has not been previously reported in the marine environment.

Vertical and horizontal distribution of sub-littoral meiofauna in Algoa Bay, South Africa

Meiofauna was sampled using SCUBA along 4 transects from 5 to 30 m depth in Algoa Bay, South Africa. Substrates were well-sorted medium to fine sands with traces of sewage pollution in some areas. Meiofauna numbers recorded in the upper 10 cm of sediment were 55 to 584 10 cm-2, but total numbers, including deeper-living animals, were 680 to 2090 10 cm-2 at 6 stations. Longer cores showed meiofauna to be abundant down to at least 35 cm, and samples of interstitial water taken from this depth in the sediment were 7% saturated with oxygen. This is the first detailed record of meiofauna penetration into sub-littoral sand and stresses the need for long cores for quantitative work. Nematode numbers were found to be significantly related to nitrogen in the sand while interstitial harpacticoid numbers were related to median particle diameters, which determine pore space. Effects of sewage were slight and only one station showed notable enrichment, increased meiofaunal numbers and extreme dominance by nematodes.

A Critical Review of Core Analysis Techniques

Abstract Considerations are presented for a coordinated program to secure and analyze cores that will yield desired objective; i.e. (1) porosity, permeability, lithology, residual fluid saturations – and probable production, (2) areal changes in porosity, permeability and lithology to characterize the reservoir, (3) interstitial water saturation and (4) samples unaltered in wetness and suitable for special core analysis tests. A review is made of currently used techniques for conventional core analysis with discussions of the strength and weakness of each. Included are comments on full-diameter, plug-size, sidewall, rubber sleeve core and combined core analysis approaches required in sands containing hyrdratable clays. Special core analysis tests available to assist in defining solutions to various reservoir problems are listed in tabular form for easy reference. Selected tests are discussed and illustrations of the effect of core wettability on certain results arc presented. INTRODUCTION CORE ANALYSIS remains the cornerstone upon which formation evaluation rests. Rock samples recovered by coring furnish information concerning lithology, storage capacity (porosity), and fluid content and deliverability (permeability). (See Table 1). Many of the basic principles used in core analysis today are the same as those originally established by the pioneers in the field. Techniques have been expanded and improved and instrumentation has undergone change; however, attention to detail and selection of the proper analytical technique for the rock type recovered are still essential to secure valid data. Changes occur in the in-situ saturations during (1) the coring operation and (2) the subsequent pressure reduction and gas expansion that occurs as the core is brought from reservoir temperature and pressure to atmospheric conditions. Core residual saturations determined in the laboratory reflect (1) coring fluid used and, hence, the filtrate lost, (2) the degree of flushing, (3) reservoir fluid properties, (4) rock relative permeability characteristics, (5) core packaging and preservation after removal from the core barrel to the time of analysis and (6) in some cases, the analytical technique. Control of the coring fluid, the core packaging and preservation, the analytical technique and to some degree the flushing, is within the grasp of the person establishing the coring program. The procedures followed should correspond to the objectives to be obtained. The remaining factors are inherent reservoir properties and are beyond control. Controllable factors are normally recorded and become an important part of the information needed for data analysis. The remaining factors influence residual gas, oil and water values and establish the ranges of saturation that indicate to the analyst whether a given formation will produce gas, oil or water. Wettability of cores is of little consequence in conventional core analysis. It is important when special tests are to follow core analysis, because certain tests made on cores non-representative of reservoir wettability yield invalid data. Objectives of the core analysis program Ideally, objectives of a core analysis program should be carefully defined before coring commences. In some cases the objectives conflict and it is impossible to satisfy all requirements on a given well.

FLUORIDE CONCENTRATION IN COASTAL AND ESTUARINE WATERS OF GEORGIA

More than 150 coastal and estuarine water samples and 48 samples of interstitial water from salt marsh sediments were analyzed for fluoride using a specific‐ion electrode method. Surface waters show that fluoride: chlorinity ratios do not attain normal ocean values until a chlorinity of 10–11‰ is reached. Interstitial waters are enriched in fluoride relative to surface waters of the same chlorinity. A mechanism for enrichment involving uptake by salt marsh plants, with subsequent release in the sediments due to bacteriological breakdown, is proposed.

The Oxygen Content of Interstitial Water in Sandy Shores

Several field investigations have been made into the nature and variations of environmental factors in the beach, both physical and chemical. The classical survey of such factors was made by Bruce (1928a, b). Other authors, for example Reid (1932), Perkins (1957), Chapman (1949) and Webb & Hill (1958), have studied specific factors in more detail than Bruce, such as salinity, the black layer, thixotropy, and the relationships between sand grain size, pore space, and drainage. Investigations into the oxygen content of the interstitial water, however, are rare. The scarcity of data concerning the oxygen content of the interstitial water is clearly demonstrated by the fact that Deboutteville (1960) in his extensive volume on the fauna and ecological factors of both freshwater and marine beaches, is compelled to deal with the oxygen content of the latter in one sentence: 'Le taux d'oxygene dissous dans les eaux interstitielles ou souterraines littorales est encore fort mal connu.' The oxygen regime existing in lakeside beaches is rather better understood, chiefly as a result of the studies by Wiszniewski (1934), Pennak (1940, 1951) and Angelier (1953). Unfortunately these workers gave few details of their methods of analysis. Nor did they report other features such as the grain size distributions of the beaches studied. A summary of studies on the oxygen content of marine beaches is given in Table 1. All except those of Jones (1955) are rather imperfect, either because the method of collecting the water sample was such that atmospheric oxygen was allowed to invade the sample, so causing errors of unknown size, or because the method of analysis failed to take into account the sources of error arising from the possible presence of chemical pollutants in the beach. The temperature of the samples was not always given. Jones (1955) used a reliable method, but a rather lengthy and cumbersome one. He gave few details of the physical characteristics of the beaches. Consequently it was considered necessary in the present work on the oxygen content of the interstitial water of marine beaches to attempt three main objects. Firstly, to devise a reliable method whereby samples of interstitial water could be collected without exposing them to the air at any stage. Secondly, to establish a reliable method of determining the amount of dissolved oxygen in an interstitial water sample. Such a method, which takes due account of all the potentially disturbing factors, was devised and used in nearly all the studies undertaken. Thirdly, using these methods of collection and oxygen determination, to make accurate investigations of the oxygen content of a number of beaches under differing conditions, in an attempt to discover the relative importance of the various factors which affect the oxygen content and control its level.

Uptake of organic material by aquatic invertebrates—II. Accumulation of amino acids by the bamboo worm, Clymenella torquata

1. 1. The maldanid worm, Clymenella torquata, is capable of removing glycine, lysine, phenylalanine and valine from dilute solution in the surrounding medium. 2. 2. The rate of uptake of these compounds from solutions of the order of 10 −6 moles/l depends on the compounds and is linear with time for at least 30 min. 3. 3. This uptake represents an accumulation of amino acid by the worm since the concentration per unit volume of body water is approximately four to ten times greater than the concentration in the medium after a 15 min exposure to an ambient solution. 4. 4. This process takes place across the body wall and does not require the participation of the digestive tract. Removal or ligation of the head or tail of the organism does not modify the rat of uptake. The rate of uptake under given conditions is an exponential function of the wet weight of the organism. 5. 5. The uptake process for these compounds exhibits kinetics which are similar to those for an enzyme-catalyzed process, indicating that uptake is probably limited by an adsorptive step at higher concentrations. 6. 6. The rate of accumulation of amino acids is independent of the oxygen tension of the medium for periods as long as 24 hr. 7. 7. Radioactivity appears in other compounds in the worms and labeled carbon dioxide can be recovered from the medium. Hence at least a portion of the amino acid taken up from solution enters functional metabolic pools. 8. 8. Samples of interstitial water, from the mud flat where the worms are abundant, were collected and free amino acids were estimated. Five estimates of ninhydrin-positive material in an extract of such samples range from 60 to 104 μmoles/l expressed as amino acid equivalents. An inventory of neutral and acidic amino acids in one sample totalled 74 μmoles/l. 9. 9. The oxygen consumption of Clymenella was measured and found to be 0·09 ml O 2/hr per g wet weight for 100 mg animals. 10. 10. Calculations, based on the amino acid levels found in the environment and the rate of uptake measured in the laboratory indicate that the amino acids obtained by the process under natural conditions may represent a significant supplement to food obtained by other methods.