Environ. Sci. Technol. 1983, 17, 47-49
(12) Hoffman, E. J.; Quinn, J. G.; Jadamec, J. R.; Fortier, S. H. Bull. Environm. Contam. Toxicol. 1979,23, 536. (13) Pancirov, R. J.; Searl, T. D.; Brown, R. A. In “Petroleum in the Marine Environment”;Petrakis, L., Weiss, F. T., Us.; American Chemical Society, Washington, D.C., 1980; Adv. Chem. Ser. No. 185, p 123.
(14) Williams, A. T. R.; Slavin, N. Chromatogr. Newsl. 1976, 4, 28. (15) Sorrell, R. K.; Reding, R. J . Chromatogr. 1979, 185, 655.
Received f o r review November 11, 1981. Revised manuscript received July I , 1982. Accepted August 2, 2982.
A Deep-Towed Pumping System for Continuous Underway Sampling Patrlck J. Setser, Norman L. Gulnasso, Jr., Ne11 L. Condra,+Denis A. Wlesenburg,s and David R. Schlnk” Department of Oceanography, Texas A&M University, College Station, Texas 77843
The system described here uses a hose-cable combination to tow a fishlike body containing a pump and a CSTD (conductive-salinity-temperature-depth) probe at depths of 135 m (or less) while the towing vessel is underway at speeds in excess of 5 m d ( 1 0 kn). This survey unit has the capability of pumping 6 L/min of seawater to analytical equipment on deck while simultaneously measuring the salinity, temperature, and depth at which the towed body is deployed. An on-deck data acquisition system automatically records physical, chemical, and biological data and provides real-time displays that can be used to modify the design of the survey as it is conducted. Optimum utilization of this system requires a heavy investment in analytical equipment and is therefore best accomplished by multidisciplinary programs. Such operation generates far more data than are normally obtained by oceanographic vessels and can substantially increase the efficiency of research ship utilization for studies of the “mixed” layer.
Introduction Studies of variability in the mixed layer of the ocean require sampling techniques that differ from the conventional oceanographic hydrographic cast taken on station. A variety of physical techniques have been developed for underway measurements by using in situ sensors with varying success, e.g., towed thermistor chains or expendable bathythermographs. Chemical studies generally are limited by the absence of effective in situ sensors; notable exceptions include the salinometer, oxygen electrode, and pH electrode. In situ fluorometers have also been deployed ( I ) for the estimation of chlorophyll, but most chemical measurements can only be done in the laboratory. For such measurements, detailed studies are best accomplished by pumping water continuously while underway from some selected depth or from various depths. The problems of doing so, various procedures attempted, and some of the successes are described in ref 2. One system for underway sampling has been developed by the Department of Oceangraphy at Texas A&M University. The system described here has been modified from the original system described by Wiesenburg and Schink (3). The System Fish. The underwater vehicle (“fish”) (Figure 1) is constructed from aluminum alloy and is controlled by lowering or raising the hose-cable. Our design relies, for the most part, on dynamic depression by the wing, which ‘Present address: Datapoint Corp., 9725 Datapoint Dr., San Antonio, TX 78284. Present address: Naval Ocean Research and Development Activity (NORDA), NSTL Station, MS 39529. 00 13-936X/83/09 17-0047$0 1.50/0
gives it an effective weight of 225 kg at a speed of 5 m s-l. The fish has good stability when towed through the water. I t is convenient to handle and work on and is easy to launch and recover. Access is gained through a large hatch on top; space is available inside for additional sensors. In Situ Instruments. Instruments mounted in the fish include a CSTD (conductivity-salinity-temperaturedepth) unit and a pump-motor unit. The submersible pump, a 12-stage centrifugal (Berkeley Pump Co., Model 4AL12) is driven by a 1.5 HP submersible motor (Franklin Electric, Model 23431441) operating on 3-phase 220-V power. Seawater is pumped at the rate of 6 L mi&. The pump delivers water at about 180 psi (1240 kPa) to the hose, which forms the core of the tow cable. An inlet pipe extends forward through the nose of the fish to sample water that has not come in contact with the body. Cable and Fairing. The hose-cable (Consolidated Products) consists of 180 m of stainless steel armored jacket enclosing 20 electrical conductors (no. 20 copper wire) that are imbedded in plastic and are wrapped around a nylon hose. The two-layered armor braiding has a 4500-kg minimum breaking strength, far exceeding loads imposed by the fish. Power to, or signals from, the pump motor, CSTD, and other instruments mounted in the fish are provided through the conductors. The nylon hose (0.95 cm i.d.) transports water from the fish to the shipboard laboratory for analysis. The cable is enclosed in a segmented fairing (Fathom Oceanology Flexnose fairing),which reduces the cable drag coefficient from 1.2 to 0.13, approximately doubling the depth achieved by the fish. Winch and Framework. The winch and framework are shown in Figure 2. At its upper end the towing cable divides, with electrical connections passing through the drum axle to a slip-ring assembly and the cable hose connecting to a watertight rotary coupling on the drum hub. Only one layer of cable can be wound onto the winch drum because the rigid fairing stands straight out from the drum. The drum is 2.1 m in diameter and holds 27 turns of hose-cable plus fairing. An articulated U-frame provides flexibility in handling the fish. The upper frame holds a 0.9 m diameter sheave on a screw-geared shaft, that serves as a level-wind for the cable. Hydraulic rams adjust the position of the upper frame and connect to a pneumatic accumulator, which serves as a shock absorber for transient stresses on the cable. The lower part of the frame can be pivoted out (hydraulically) to extend substantially beyond the stern of the towing vessel. Other Shipboard Equipment. Analog signals from the CSTD are continuously recorded on a 12-pen strip chart recorder. The signals are also passed through an analogdigital converter and logged on a shipboard computer (Hewlett-Packard 2100A). During a recent cruise, water
0 1982 American Chemical Society
Environ. Sci. Technol., Vol. 17, No. 1, 1983
47
la L E M L WIND ASSEMBLY
TOP ARM-
I
ELECTRICAL SLIP RlNQS AND WATER JOINT
CABLE TAKEUP DRUM
-CHAIN
DECK O f TOWING VESSEL
DRIVE
LDEPLOYMENT HYDRAULIC CYLINDER
I Flgure 2. Towed pumping system winch, framework, and cable. System is -5.5 m long, 3 m high, and 2 m wide and weighs -2800 kg. System is bolted to deck of ship.
Ib
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37"55'N 69'14'W
36"02'N 69'13'W
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Flgure 1. Towed pumping system underwater vehicle. The cable termination and some of the instrumentation mounted in the vehicle are shown in c. Weight of the fish with instrumentation In alr is less than 100 kg.
0 3
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.
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from the submerged pump was supplied to a Turner Designs fluorometer fitted with a flow-through cuvette and to a 4-channel Technicon Autoanalyzer I1 system. Continuous fluorescence and nutrient measurements were logged on analog recorders and digitized by the computer system. Data management is accomplished by using TALK, an interactive data acquisition and display program that stores data on disk and also transfers the data to magnetic tape for later analysis. The program logs time, windspeed, wind direction, and the ship's position. Chemical, physical, and biological data can be displayed and plotted as they are recorded. TALK also generates maps of the cruise track and several data reports. Performance The modified system was first deployed from the R/V GYRE on Cruise 80-G-6B in the Atlantic Ocean off the 48
Environ. Scl. Technol., Voi. 17, No. 1, 1983
PHAEOPIGMENTS
E" 1.0
:
:
:
0900L
Table I. Properties of Turbulent Flow in a Hose Constants for TAMU Towed Pumping System uo = towing speed = 6 kn = 300 cm s-l L = length of hose = 200 m = 2 X cm
lo4
a = inside radius 318 in. i.d. = 0.5 cm radius Q = flow rate = 6 L min-' = 100 cm3 5-l R = Reynold's no. Equations u = mean flow velocity = &/nuz = lOO(3.14 x 0.52)-'cm3 5-l cm-' = 127 cm 5-l R = Reynolds no. = 2 au/v = 1 2 700 T = time delay through the hose = L / u = 2 x 104(127)-' c m cm-' s = 157 s S = sample smeara = (4.02 x a x L x R - 1 ' 8 ) 1 1 2 ~ O ~ - 1 = (4.02 x 0.5 x 20000 x 0.307)1'2x 300 x 127-l (cm cm)l/zcm s-l cm-' s = 262 cm T = smear duration = S / u , = 262( 300)-' cm cm-' s = 0.87 s a An impulse entering the hose exits approximately as a Gaussian distribution, Sample smear, S, is the standard deviation of that distribution. See Guinasso e t al. ( 5 )for the derivation of the samale smear eauation.
ship during retrieval. The fish could actually be lanched or recovered single-handed, although normal practice involves two or three persons. Deployment to maximum depth could be accomplished in 5 min, but recovery was slower because of the requirement that the fairing stand up perfectly straight as the hose is spooled onto the drum. When retrieving the fish the ship's speed was normally lowered to 4 kn (2 m s-'), substantially reducing the strain on the hose-cable. However, both deployment and retrieval could be accomplished at full speed (5 m s-l). Some data obtained during R/V GYRE Cruise 80-G-6B suggest the potential of continuous deep-towed sampling. The fish was towed into a transition zone between the Gulf Stream and slope water at selected depths for various periods of time. The OceanographicAnalysis for this time period ( 4 ) shows the northern edge of the Gulf Stream bounded by a tongue of cool water extending from the east; to the north of this tongue there is a stream of warm water apparently flowing westward. This interweaving of water types results in a transition zone between Gulf Stream and slope water. We entered this transition zone at -0700 as the ship steamed north. At 0730 the fish was lowered slightly and the ship turned around to steam south, leaving the transition zone and reentering the Gulf Stream proper at about 0800. Figure 3 shows a plot of depth, temperature, salinity, fluorescence, dissolved nitrate plus nitrite, chlorophyll and phaeopigments collected from 0600 to 0900. Corresponding changes can be observed in the various parameters as the fish is lowered and the Gulf Stream front is encountered. The chlorophyll a and phaeopigment concentrations were determined by standard laboratory analyses of water samples pumped from depth. The deep-towed pumping system can explore chemical and biological properties that cannot be observed by in situ sensors, as the ship steams over different waters. Some smearing of the variations in water properties occurs as water passes up through the hose. Guinasso et al. (5) have
described problems inherent to pumping samples through long hoses: smearing and mixing in dead volumes. Table I gives characteristics of our system. One important conclusion is evident from their treatment: longer hose systems inherently degrade the resolution; and ship's speed must be reduced in proportion to hose length if resolution is to be maintained. Very high pressure pumps might partially overcome the loss in resolution due to hose length, but that remedy is limited.
Conclusions Water samples and in situ measurements can be taken throughout the mixed layer while an oceanographic vessel is underway at speeds in excess of 5 m s-l. This capability provides the potential for a great increase in our understanding of mixed-layer processes. Deployment of this system requires a heavy investment in associated analytical equipment plus an appropriate team of analysts and operators. A substantial program of data management must also be provided to utilize the full potential of this sampling system. Acknowledgments The deep-towed pumping system was modified and the new fish was fabricated at the Research and Instrument Shop, Texas A&M University, under the direction of Joseph C. Brusse, who also provided many valuable suggestions and design features. Much of the machining and assembly of the modified system and construction of the fish was performed by Tobby Selcer. The fish was designed with critical advice provided by Reece Folb and Richard Knutson of the Towed System Branch, Naval Ship Research and Development Center, Bethesda, MD. Otis Eickenhorst also provided valuable assistance. Lynne Bergbreiter developed the TALK program. We thank the crew and technicians aboard the R/V GYRE for their efforts in deploying the system during Cruise 80-G-6B. We also thank Fathom Oceanology for their cooperation and for their tolerance of our modifications to their designed system.
Literature Cited (1) Herman, A. W.; Denman, K. L. Deep Sea Res. 1977, 24, 385-397. (2) Steering Committee, Underway Water Sampling Technology, "Water Sampling While Underway"; proceedings of a symposium and workshops, Washington, DC, 1980. National Academy Press: Washington, DC, 1981. (3) Wiesenburg, D. A.; Schink, D. R. "Use of the Texas A&M Deep Towed Pumping System in the Gulf of Mexico Aboard the Research Vessel GYRE During Cruise 77-G-14, 3-7 December 1977; Department of Oceanography, Texas A&M University, College Station, TX, Technical Report 78-4-T, 1978. ' (4) National Environmental Satellite Service, Oceanographic Analysis, July 28, 1980, D127-Ng8-No. 587, National Weather Service. (5) Guinasso, N. L., Jr.; Wiesenburg, D. A.; Schink, D. R. Submitted for publication in J. Mar. Res. Received for review October I , 2981. Revised manuscript received March 25, 1982. Accepted August 10, 1982. This work was supported by Office of Naval Research Contracts N00014-75C-0537 and NOOO14-80-C-0113, Office of Sea Grants, Institutional Grant 04-7-158-44105.
Environ. Sci. Technol., VoI. 17,No. 1, 1983 49
