Apparatus for the simultaneous collection of pore water specimens from adjacent areas of aquatic sediments

Abstract

A specimen collection apparatus for the simultaneous collection of pore water from adjacent areas of aquatic sediments provided with a plurality of miniaturized tubular specimen collectors in a vertical array mounted for horizontal movement into and out of a housing relative to the sediment. A Benthin chamber may be provided spaced from the specimen collection apparatus such that the specimen collectors thereof may be moved into the sediment below the Benthin chamber.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention, in general, relates to a novel apparatus for simultaneously collecting specimens of pore water from adjacent areas of aquatic sediments, and, more particularly, to an apparatus of the kind referred to provided with a plurality of miniature specimen collectors arrayed in a housing and provided with a hydrophillic micro-porous plastic hose connected, at its pore water intake side, to a support rail and, at its pore water discharge side, to a vacuum device and a storage device.

2. The Prior Art

Such a specimen collection apparatus is used for simultaneously collecting of pore water specimens from aquatic sediments for geochemical and bio-geochemical examinations of the transition zone between, or at the interface of, sediment and water. Processes in the sediments and in the bottom water generate gradients in the pore water, for instance in the concentration of its. Especially the decay of organic substances and the dissolution of minerals generate a gradient in the pore water. Pore water is often examined ex situ by taking a sediment core onboard a ship or ashore where it is divided into sub-samples. They are squeezed out under pressure and centrifuged to yield their pore water. However, such a process may change the chemistry of the pore water as a result of temperature and pressure changes as well as of undesirable oxidation and contamination.

For that reason, in situ systems which examine the sediment in its natural environment are being used more and more. A so-called “whole core squeezing” process is known from the paper “The ROLAI²D lander: A benthic lander for the study of exchange across the sediment-water interface” by F. L. Sayles et al. (Deep-Sea-Research, Vol 38, No. 5, pp. 505-529, 1991)’, hereafter sometimes referred to as “Publication I”, which discloses depositing on the sediment a free-falling support system (“lander”) for apparatus for examining the bottom of the sea by capturing a sediment core in a sampling tube. The sediment is squeezed out from below and from above. The pore water escapes through openings in the tube into collection containers. Not only is the very complicated and complex modus operandi of the specimen collector disadvantageous, but the sediment can only be examined once since the sediment compound is destroyed during the collection of the sediment. In view of the fact that the sediment is being compacted during its compression and is thus moved by the openings in the specimen tube, it is at best difficult to assign the taking sites to a defined horizon (depth of sediment).

The paper “An in situ sampler for close interval pore water studies” by R. H. Hesslein (Limnology and Oceanography 21(6), Nov. 1976, pp. 912-914), hereafter sometimes referred to as “Publication II”, discloses the so-called “peeper” method which operates on the principle of diffusion. The sediment receiving apparatus consists of a corpus with many chambers which are filled with distilled water and covered my a diaphragm. The specimen collection apparatus is installed in the sediment and thereafter an equilibrium is established between the water in the chambers and the pose water. After an equilibrium has been established the specimen collection apparatus is retrieved for analyzing the pore water within the chambers. A drawback inherent in this process may be seen in the fact that for proper examination of the sediment the specimen collection apparatus must remain therein for rather a long time. Moreover, only one examination can be performed so that abrupt parameter changes in the sediment cannot be detected. Furthermore, there remains the risk of the equilibrium not having been established when the specimen collector is being retrieved.

A third in situ process has been disclosed by the paper “A new device for in-situ-pore-water sampling” by A. Bertolin et al. (Marine Chemistry 49 (1995), 233-239), hereafter referred to from time to time as “Publication III”, and involves a suction specimen collector. The specimen collection device consists of a blade-like housing the narrow front surface of which defines its size and which is usually equipped with openings protected by filters or gauze through which pore water is sucked into storage containers provided behind the openings, upon application of vacuum pressure. One disadvantage of this process is the very long adaptation time of about two weeks the specimen collector requires after being placed in the sediment before the sediment can be examined. Furthermore, the pore water is sucked in through relatively large opening surfaces so that the possible vertical and lateral resolution are rather poor. Also, the quantity of pore water which can be taken in is quite limited in cases where it is to be taken in free of any contamination.

Every one of the mentioned three apparatus for in situ processing suffers from the fact that they disturb or destroy the surface of the sediment when they penetrate into it. The result will thus be undesirable artificial mixing zones, and the simultaneous use of a so-called “Benthin chamber” is rendered impossible. A Benthin chamber is a cylindrical chamber without a bottom which is placed on the sediment. Any change in the concentration of substances in the volume of water incubated within the chamber yields an indication about any exchange or interaction about the interface of sediment and water. By rotating the lid of the Benthin chamber or a stirrer within the chamber below its lid a three-dimensional current can be generated in the interior of the chamber which will also flow through areas of the sediment. This arrangement is based upon the recognition that advective currents greatly affect the movement of dissolved and particulate matter at the bottom of the sea. A Benthin chamber is a suitable apparatus for conducting experimental studies of such movements.

An article “Pore water sampling with Rhizon sampler” by M. Koelling, hereafter sometimes referred to as “Publication IV”, has been published by the University of Bremen, Germany, and may be down-loaded at http://www.geochemie.uni-bremen.de/koelling/rhizon p.html (status 20 October 2004) and relates to the use of miniaturized specimen collectors with a hydrophillic micro-porous plastic hose which at its pore water intake side is connected to a support rail and with a vacuum removal device at its pore water discharge side. This so-called Rhizon bottom moisture specimen collector is a miniaturized filter tube with a micro-porous polymeric hose at its intake side and a vacuum-pressure proof PVC hose at its discharge side and which represents an artificial root developed for collecting bottom moisture in unsaturated bottom zones (see Prospectus P2.30 of the Eijkelkamp company “Soil Moisture Sampling” pp. 183-186 which may be down-loaded at http//:www.waterland.com.cn/PDF/P2-30e.pdf, status 20 October 2004 and Prospectus Doc. No. 1190 “Techinfo Ben Meadows Company: Rhizon Soil Moisture Sampler”, 2002 Lab Safety Supply Inc.).

According to Publication IV by the University of Bremen, the specimen collector described is used in a specimen collection apparatus for simultaneously collecting pore water from adjacent aquatic sediment areas for the ex-situ examination of water-saturated marine sediment. Hence, the known filter tubes may be said in some ways to be misused. The sediment to be examined is initially gathered in a tubular housing which is then moved ashore and closed by a lid. In the wall of the housing there is provided a series of small bores disposed parallel to the longitudinal axis of the housing through which the supported plastic hoses may be injected into the sediment. The specimen collectors are thus arranged in a row and each individual pore water specimen gathered in a storage tube either by way of a small connected vacuum pressure tube or by way of an injection syringe functioning as a suction device, can be assigned to an area of the sediment. Publication IV does not, however, disclose whether the sediment area extends vertically of laterally relative to the bottom of the body of water. A disadvantage of this known specimen collecting apparatus is that it is designed for ex situ pore water examination and that the injection of the tubular housing into the area of sediment to be examined results in a substantial disturbance of the natural ambient conditions. The ex situ measuring process and the disturbance or destruction of the sediment surface preclude any measurements accompanying the specimen collection, for instance by a Benthin chamber.

OBJECTS OF THE INVENTION

Proceeding upon the apparatus known from Publication IV, it is an object of the instant invention so to improve a specimen collecting apparatus with miniaturized specimen collectors that it can perform in situ examinations of aquatic sediments in vertical high-resolution.

Another object resides in the provision of an apparatus of the kind referred to which is capable of performing examinations without disturbing the surface of the sediment to allow in situ accompanying examinations.

SUMMARY OF THE INVENTION

In the accomplishment of the aforesaid objects the invention provides for a specimen collection apparatus for simultaneously collecting pore water from a plurality of adjacent aquatic areas of sediment and provided with a plurality of miniaturized specimen collectors arrayed within a housing with a hydrophillic micro-porous plastic hose provided at the pore water intake side thereof with a support rail and at the pore water discharge side thereof with a suction removal device and a storage device, the specimen collectors being vertically disposed in a support device within a narrow side of a blade-like housing and connected to a process unit in which the specimen collectors by the intake side thereof may be moved into and out of the sediment areas relative to the housing in the area of the narrow side thereof.

Other object will in part be obvious and will in part appear hereinafter.

An advantageous application of the specimen collection apparatus of the invention relates to an in situ interaction with a Benthin chamber placed upon the bottom of the body of water at a distance from the specimen collection apparatus sufficient to allow movement of the specimen collectors into the sediment area below the Benthin chamber without disturbing the sediment surface within the Benthin chamber.

The specimen collection apparatus in accordance with the invention is provided with a number of sample collectors structured as miniaturized filter tubes of the kind referred to above disposed vertically within a support device in a blade-like housing. The support device is arranged within a housing which extends downwardly in a conical pointed configuration. The blade-like configuration allows the housing simply to penetrate in a vertical direction into the surface of the sediment without significantly damaging the surface of the sediment. Once the housing has reached its vertical depth of penetration—which is usually within the upper several decimeters of the layer of sediment—the individual specimen collectors disposed vertically of each other within the sediment and thus make possible high-resolution vertical profile measurements, may be actuated. For this purpose they are horizontally injected by their supported intake sides from the narrow front surface of the blade-like housing into the sediment area adjacent the housing. Thus, the examination is not performed within the housing, but rather within an undisturbed neighboring area which as a result of the small diameter of the protruding specimen collectors is not unduly disturbed. Taking a specimen does not require a long dwell time. Directly the specimen collectors have been injected into the sediment the examination may commence. Several specimens may be collected from the same sediment area by actuating the suction removal device at predetermined intervals of time. The pore water specimens may be mixed or stored separately in appropriate storage devices. Multiple actuation may also take place by repeated injection and withdrawal of the specimen collectors so that the chronologically observable conditions within the sediment may adjust themselves without disturbance by the specimen collectors,

In summary, the specimen collection apparatus makes possible the collection, under in situ conditions, of pore water specimens from different levels or horizons in the upper decimeters of an undisturbed aquatic sediment. It allows an examination of pore water within the sediment in a vertical high-resolution which may take place once or repeatedly at predetermined intervals of time in order to allow for examination of chronological changes. The pore water profiles provided by the specimen collection apparatus may provide new insight into the motion an reaction processes within the sediment and at the interface of sediment and water. For examining the interaction at this interface, the use of the claimed specimen collection apparatus makes it possible to apply a Benthin chamber. Hitherto it has not been possible directly to examine the pore water below such a chamber. By laterally ejecting the specimen collectors from the blade-like housing of the specimen collection apparatus it has, however, become possible in view of the fact that the sediment surface disposed immediately above the specimen collector is not disturbed or damaged by the specimen collecting apparatus. In this fashion, it is possible to conduct further examinations in this area. Accordingly, the specimen collecting apparatus combines high functionality in keeping with theoretical demands for a high-quality examination of pore water by an anoxic examination, a low dead volume in the apparatus and, by the fact that the pore water is collected in a filtered state because of the specimen collectors structured as miniaturized filter tubes with a micro-porous plastic hose for taking in pore water, with a high suitability for use in the field because of the low disturbance of the sediment to be examined.

The basic components of the in situ specimen collection apparatus are specimen collectors structured as rhizons. Rhizons are commercially available soil moisture specimen collectors. At their pore water intake side they usually consist of a piece of hydrophillic micro-porous polymeric hose glued to a support rail which may be a stainless steel wire or plastic. Their discharge side is connected to a PVC hose by means of which a pore water sample may be sucked by vacuum pressure into a storage device. In the simplest case, the storage device may be structured as small tubes; but multiple-chamber storage containers may be used as well. An unequivocal association of each separate storage container with its specimen collector is important for establishing a correct profile curve of every parameter. The suction device may be manually operable injection syringes or motor-driven peristaltic pumps. Each specimen collector may be associated with its own separately actuable suction element. Alternatively, the specimen collectors may share a common suction device. Manual operation as well as motorized and automatic actuation of the section device are possible.

The specimen collectors are mounted into a support device such that they may be mechanically moved into the sediment once the blade-like housing has been pressed into the sediment. A distinction may be made between two variants: First, each specimen collector is separately supported and may be separately pushed into the sediment or, second, all sample collectors are mounted in a common support device and are pushed into the sediment together. In the first case, the support for each specimen collector is provided with a support element for each specimen collector, and for each support element there is provided a separately actuable movement element in the movement device. Each support element may be structured as a tube which is rigidly connected to the support device and which receives the specimen collector in its withdrawn state. Hence, the tube function as protective tubes for the specimen collectors in their withdrawn state. The specimen collectors are supported by angular rails such that by moving the angular rails they may be moved as a component of the movement element out of the forward end of the tubes. For forward and reverse movement each movement element may be provided with a bidirectional cable drive. These may be some kind of a “fishing line” attached by bores at the forward and rear ends of a tube on the angular rail of each specimen collector. By pulling the corresponding end of the fishing line (or of separate fishing lines) and the ensuing movement of the angular rail the specimen collector may be pushed into or pulled out of the sediment. Each specimen collector may be actuated separately. However, all cable drives may alternatively be guided by a common support block so that, in the manner of a puppet control, that may be actuated at the same time.

In the second case of a common support, the support device is rigidly connected to all specimen collectors, with the specimen collectors extending out of the support device by their intake sides, and is structured so as to be movable. In this embodiment, too, a bidirectional cable drive may be used. It would engage the forward and rear ends of the support device and by actuation of the appropriate cable it may move out of and into the support device. It is also possible to provide motorized as well as automatic movement by separate or common drives.

DESCRIPTION OF THE SEVERAL DRAWINGS.

The novel features which are considered to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, in respect of its structure, construction and lay-out as well as its manufacturing techniques, together with other advantages and objects thereof, will be best understood from the following description of preferred embodiments when read in connection with the appended drawings, in which:

FIG. 1A is a side elevation in cross-section of the specimen collection apparatus in accordance with the invention;

FIG. 1B is a frontal view of the specimen collection apparatus of FIG. 1A;

FIG. 2 is a detailed view of a specimen collection apparatus in accordance with the prior art; and

FIG. 3 is a measuring diagram of two parameters recorded with the specimen collection apparatus in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.

FIG. 1A depicts in side elevational cross-section a specimen collection apparatus PNG for the simultaneous collection of pore water PW from adjacent aquatic sediment areas SB during its used on the bottom of an ocean. The specimen collection apparatus PNG is provided with a substantially closed housing SG the downwardly tapered blade-like configuration and weight of which facilitate a substantially vertical and stable penetration of the specimen collection apparatus PNG into the sediment area SB. The frontal view of FIG. 1 B of the specimen collection apparatus PNG clearly depicts the blade-like configuration of the housing SG. In a small forward side SSS of the housing SG six specimen collectors PN are horizontally arranged within a support device TE. The vertically stacked arrangement of the specimen collectors PN makes it possible to determine a vertical measuring profile of predetermined parameters in the sediment area SB. For this purpose, the specimen collectors PN may by their intake side ANS be horizontally moved into and out of the sediment areas SB by the narrow forward surface SSS of the blade-like housing SG.

In the embodiment shown in FIG. 1A each specimen collector PN is movably mounted in a tube RO or support element TEL of its own which is rigidly connected to a support device TE. The figure shows the intake sides ANS of the specimen collectors PN supported by support rails SS in their position extended into the sediment areas SB. This is accomplished by a movement device VE constructed of individual movement elements VEL of a number equal to that of the number of tubes. In the selected embodiment the movement element VEL is a manually or motor (also automatically) driven bidirectional cable drive NSZ which is connected to the forward and rear ends of an angular rail WS rigidly connected to the specimen collector PN. By actuation of the appropriate end of the cable drive BSZ the specimen collector PN is pushed out of the protective tube RO i.e. the support element TEL, so that its intake side ANS penetrates into the sediment areas SB, or withdrawn from it.

In another embodiment not shown in FIG. 1A all specimen collectors PN are rigidly connected to the support device TE. This may be a simple perforated piece of sheet metal and a central support rod. All specimen collectors PN extend over the support device TE by their intake sides ANS. By moving the entire support device TE the intake sides ANS of the specimen collectors PN may be moved into and out of the sediment areas SB. The movement device VE may again be actuated manually or by a motor (also automatically), for instance by a single bidirectional cable drive BSZ which engages the support device TE.

In addition to the specimen collection apparatus PNG FIG. 1A depicts a Benthin chamber BK placed upon the bottom of the body of water. Since it has no bottom, it penetrates into the sediment area SB. By a stirrer RUH, a circulating current affecting the exchange or interactive processes in the sediment area SB. These may be detected by the specimen collecting apparatus PNG by the specimen collectors PN in their laterally expended state examining the sediment area SB below then Benthin chamber BK without damaging or destroying the bottom of the water GB within the Benthin chamber BK and affecting the interactive or exchange processes at the interface between the water and the sediment. Additional water specimens WP for comparative measurements may be obtained in the Benthin chamber BK by way of collective lines SA.

The specimen collectors PN used are miniaturized filter tubes, so-called “Rhizon bottom moisture specimen collectors”, see FIG. 2. They are commercially available, but in the specimen collecting apparatus PNG in accordance with the invention they are not being used in connection with unsaturated bottoms but, rather, with bottoms saturated by water. In accordance with FIG. 2 a specimen collector PN in accordance with the prior art at its pore water intake side ANS consists of a hydrophillic micro-porous plastic or polymeric hose KS of a length of, for instance, 5 or 10 cm and a diameter of 2.2 mm with a pore size of 0.2 μm stabilized by a supportive rail SS. This may be metallic or plastic stiffening wire. At its pore water PW discharge side ABS the specimen collector is provided with a PVC hose PVCS by which it is connected, by way of a connector VB with an injection syringe IS functioning as a suction removal device ASV with an inter=grated storage device LV. By means of connecting hoses VSS made of silicon extension hoses VLS may be connected to the PVC hose PVCS.

FIG. 3 by way of example depicts two chloride profiles (chloride in mmol/l above the sediment depth in cm) and two silicate profiles (silicic acid in μmol/l above the sediment depth in cm) which resulted from measurements made by the stationary specimen collection apparatus PNG at the same location in a sediment area SB on the bottom of a body of water GB at times A and B. The chronological changes which may be considered to result from interactive or exchange processes may be clearly seen in the curves.

Claims

1. A specimen collection apparatus for simultaneously collecting pore water from adjacent aquatic sediment areas, comprising:

a plurality of miniaturized specimen collectors comprising a hydrophillic micro-porous plastic hose having means comprising a pore water intake side and a pore water discharge side;

a support rail at the pore water intake side;

a suction device and a storage device connected therewith at the pore water discharge side;

a housing of substantially blade-like structure with a vertical narrow surface and provided with a support device for receiving the specimen collectors with their pore water intake side in alignment with the narrow surface; and

means for horizontally moving the specimen collectors relative to the sediment areas between a position out of and a position within the blade-like housing.

2. The apparatus of claim 1, wherein the support device is provided with a support element for each specimen collector and wherein each specimen collector is provided with its own means for moving.

3. The apparatus of claim 2, wherein each support element is structured as a tube rigidly connected to the support device and wherein the tube receives the specimen collector in its position within the housing and wherein each means for moving comprises an angular rail rigidly connected to the specimen collector and a cable drive.

4. The apparatus of claim 1, wherein the support device is rigidly connected to and moveable with every specimen collector.

5. The apparatus of claim 4, wherein the means for moving is provided with a bidirectional cable drive.

6. The apparatus of claim 1, wherein the support device comprises a support wire made of one of stainless steel and plastic.

7. The apparatus of claim 1, wherein the suction device of each specimen collector comprises a separate suction element.

8. The apparatus of claim 1, wherein the suction device is associated with every specimen collector in common.

9. The apparatus of claim 1, wherein the specimen collectors are structured as Rhizon bottom moisture specimen collectors.

10. A method of using an apparatus of claim 9 comprising the step of positioning a Benthin chamber at a distance from the specimen collection apparatus such that the specimen collectors may be moved into the sediment area below the Benthin chamber.