Assessment of Sediment Contaminants from Ceramic Production, a Case Study of Farstaviken

Assessment of Sediment Contaminants from Ceramic Production, a Case Study of Farstaviken Ola Öberg Department of Land and Water Resources Engineering...
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Assessment of Sediment Contaminants from Ceramic Production, a Case Study of Farstaviken

Ola Öberg Department of Land and Water Resources Engineering KTH, Royal Institut of Technology

Stockholm 2001

TRITA-LWR LIC 2003 ISSN 1650-8629 ISRN KTH/LWR/LIC 2003-SE

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TABLE OF CONTENTS

TABLE OF CONTENTS ............................................................................................................................3 ACKNOWLEDGEMENT...........................................................................................................................5 SUMMARY ..................................................................................................................................................7 INTRODUCTION .......................................................................................................................................9 THE FARSTAVIKEN CASE. ...............................................................................................................9 OBJECTIVES. .................................................................................................................................11 WATER EXCHANGE MECHANISMS. ...............................................................................................11 FIELD INVESTIGATIONS. ...............................................................................................................16 CONCLUSIONS ........................................................................................................................................20 REFERENCES ..........................................................................................................................................21 APPENDED PAPERS ...............................................................................................................................22

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ACKNOWLEDGEMENT The following persons have contributed with information, advice and help: Klas Cederwall KTH, Torkild Carstens NTNU, Olle Wahlberg KTH, Per Johnsson UU, Lennart Toresjö Värmdö Kommun, Anders Engqvist SU, Christer Lännergren Stockholm Vatten, Joakim Irebjer Värmdö, Gunnar Lundmark Bertil Dahllöv Gustavsbergs Fabriker, Wibjörn Karlén SU, Christina Jonsson SU, Ingemar Cato SGU, Robert Hartwell Kristoffer Reinius Petter Stenström Ziji Zhang Britt Chow Aguisew Nigusse Hans Bergh Bijan Dargahi Fredrik Marelius KTH. Financial support has been given by: The Division of Hydraulic Engineering, Department of Land and Water Resources Engineering, Royal Institute of Technology - Stiftelsen J. Gust. Richert, SWECO - Centrum för Miljövård, KTH - JM Bygg AB Supporting comments during the work were given by: My family and my friends. Thank you, all above mentioned and all the other happy faces I met during this work! A special thought goes to my dog Catchina who accompanied me every day!

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SUMMARY This case study may hopefully promote the development of new strategies for management of marine engineering activities in an archipelago environment. The main objective has been to investigate the distribution and quantity of disposed material into a marine environment including the contaminants lead, zinc and cadmium. This was done by means of a material balance and a material sedimentation transport model. Another objective was to improve the understanding of the mechanisms for water ventilation of archipelago type basin systems. Hydraulic simulations were carried out by means of a model calibrated with existing field data. This thesis analyses some aspects on the water exchange of the Farstaviken basin and some aspects of the application of field investigations of sediments in the same area. Appended are three independent articles that deals with the material balance, a distribution model of the disposed material and a water-exchange model for a small semi-enclosed water basin. Investigation of the sediment in a vertical bottom profile can give a historical record of the activities and processes rendering disposed contaminates as well as oxygen consuming matter from the storm water catchment area of the water basin. The model for simulation of water exchange gives results that are in line with measured data. It can therefore, after some modifications be a useful tool to utilise in environmental impact assessments. The simulation shows also that the dominating mechanism for water exchange in this kind of water basin is fluctuations of density across the strait connecting to the outer archipelago.

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INTRODUCTION Urban areas are often situated along the waterfront of water basins with limited water exchange. The water quality of the marine environment in these basins may be significantly impaired by pollution and the result is likely to be a strong anthropogenic impact on biodiversity. Different activities in the urban area, historic or prevailing, are the sources of the impact. Examples are industrial wastewater discharges, storm water from urban areas where traffic and other activities add pollutants and nutrients to the water and even improper sewer systems. The marine environment is very sensitive and needs long time to recover from water quality degradation if the water exchange (the ventilation) of the basin is poor. As the number of inhabitants grows in an area, more and more of old industrial sites are restored and used for housing. Especially interesting are areas close to the water. Construction companies and other actors investing in an area often take initiatives for restoration of polluted land to provide a healthy living environment. The companies however do neither have economic advantage of restoring the marine ecosystem nor are they forced by legislation. The knowledge of how to pursue such rehabilitation measures is also often rather poor. The need for restoring degraded ecosystems can be site specific but more likely similar problems exist at many other places. To restore a degraded marine ecosystem to its original status provides several advantages like creating recreation areas, edible seafood from close to where one lives and an overall understanding that sound ecological life is possible. This puts an emphasis on the development of innovative approaches and integrated strategies for management of urban marine ecosystems and particularly for basins with limited water exchange. This case study was carried out to provide a basis for the development of strategies for management of marine engineering activity in an archipelago environment The Farstaviken case. A factory producing ceramics has discharged wastewater into a semi-enclosed water basin, Farstaviken situated within the Stockholm archipelago.

Ägnöfjärden

Nämdöfjärden

FIGURE 1. The central part of Stockholm Archipelago

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The water basin Farstaviken is situated 20 km east of Stockholm. It is connected to the larger basin Baggensfjärden through a strait, Farstasund. The length of Farstaviken is 1.7 km, the surface area 0.59 km2 and the drainage catchment area for storm water is 5.65 km2. Baggensfjärden has a surface area of 13.4 km3 and a connection to the Baltic Sea through another strait, Fällström and then further via the basins Ägnöfjärden and Nämndöfjärden. The wastewater was disposed to Farstaviken at the very inner part. A large part of the dry material included in the waste water settled close to the outlet in shallow water at an area about 15 000 m2. The thickness of this material is in average 1 m. Glazing agents as zinc oxide and lead oxide were used in the production. The glazing agents represented approximately 5 % of the glaze cover, which on average FIGURE 2. Baggensfjärden and represented 10% of the Farstaviken manufactured product (Lundmark 1999). Colouring agents, mostly different kind of metal oxide, were also used in the production and did give different colours to the recipient according to the fashion in production. Waves are eroding the bottom material in this inner shallow part especially when water level is low and the wind blows strong from the west. The suspended material is slowly transported to deeper bottoms. During the period of disposal, the fine material was transported out into the entire basin. Material was deposited on the sedimentation bottoms, more in the deeper parts then in shallow areas and beach slopes as illustrated in Figure 3. This indicates the importance of selecting a strategy for taking samples in the sediment to find the real spreading of contaminants.

Figure 3. The Farstaviken basin hypsography and the sediment distribution in principle

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The amount of material that has been disposed has changed the hypsography of the inner part of the basin so that the water there is relatively shallow. At the beginning of the 20th century large boats could navigate here.

FIGURE 4. Clay-transport ship at the early 20th century (Arvidsson 1997). Objectives. The main objective of this study was to investigate the distribution and quantity of the disposed material including the contaminants lead, zinc and cadmium. This was done by means of a material balance and a material sedimentation transport model. Another objective was to improve the understanding of the mechanisms for water exchange by means of a model, calibrated with existing field data. This thesis analyses some aspects on the water exchange of the Farstaviken basin and some aspects of the application of field investigations of the sediments in the same area. Appended are three independent papers that deal with the material balance, a distribution model of the disposed material and a water-exchange model for a small semi-enclosed water basin. Water exchange mechanisms. The water level at some specific location in the archipelago is affected by the sea water level outside the archipelago and by the local wind tilting the surfaces of inter linked basins in the direction of the open sea.

FIGURE 5. Local wind affecting water levels in an archipelago system of linked basins 11

This tilting is due to a balance between gravity forces and wind shear stress at the water surface which is dependent on the wind velocity field, wind fetch length and depth of the basin and on the hydrographical situation in the system of basins. The water density is dependent on temperature and salinity. When the density profile of the water column indicates stratification the interface between two layers in a twolayer system of the basin is called a pycnocline. The pycnocline will act as a bottom for wind generated turbulence, which will make the upper layer normally well mixed. The lower layer has higher density and will in most situations have significantly reduced water exchange with the upper layer. The pycnocline will tilt in the opposite direction relative to the water surface as indicated in Figure 6 and the size of the tilting of the pycnocline is also magnified relative to the tilting of the surface. Strong wind can however break up the pycnocline due to the eroding effect of upper layer turbulence.

ρ1 ρ2

FIGURE 6. Wind caused interfacial tilting in density stratified water If the density profile is measured in the middle of a basin, the tilting of the pycnocline has to be considered when estimating the vertical density profile at the end of the basin. In the case of two connected basins it clarifies to first study them in an assumed situation with a locked strait. Both the basin surfaces may now be tilted separately and a level difference will be created across the lock. The adjacent sea will affect this difference if one of the basins has a sea connection.

FIGURE 7. Two basins affected by wind If the lock is suddenly removed a water-exchanging mechanism starts to even out the water level differences between the two linked basins.

FIGURE 8. Water exchange through a strait due to surface level differences

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When the water level difference is relaxed the wind will continue to maintain a current pattern as illustrated in Figure 9. No significant transport of water is maintained through the straight.

FIGURE 9. Steady state situation When the wind stops the tilting is no longer in balance and gravity forces the water to establish a horizontal surface. A reversed current situation occurs in the strait, which may encompass the whole depth of the strait. Because of the kinetic and potential energy of the water system, the surface of a basin will oscillate around the horizontal some time before the energy is damped out. This phenomenon is called seiching and it FIGURE 10. Counter current will also cause water to flow through the strait forced by the seiching within the two basins. Seiching occurs also in the lower layer and will possibly lead to the appearance of internal waves. In the case of baroclinic flow the ρ2 ρ1 water of the basins have different density across the strait connecting the basins but no water level differences. Two equally big currents will be established in the strait in FIGURE 11. Baroclinic flow, ρ2>ρ1 opposite directions, the lighter water flows on top. These currents continue until density differences vanish. If the wind is strong enough or if the pycnocline is situated relatively close to the surface the tilting pycnocline will cause denser water to flow over the sill. This water will enter the basin and sink to the level with equal density. An equally big flow occurs in the upper part of the strait to maintain water balance in the basins.

FIGURE 12. Bottom water exchange

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Maximum depth in Farstaviken is 20 m, and in Baggensfjärden 80 m. The straight Farstasund has a depth 6 m and the straight Fällström a depth of 11 m. This means that the bottom water of Baggensfjärden and particularly Farstaviken is poorly ventilated. The consequence is significantly denser water below sill level in each basin compared to the next basin in the direction of the open sea, Figure 13. It also means that the bottom water can be oxygenated at occasions when strong wind stirs up denser water from the deep sea and transports it all the way into the specific basin.

2,5

3,0

3,5

4,0

Sigma- T 4,5 5,0

0 depth m4 8 12 16

Baggensfjärden Farstaviken Ägnöfjärden

FIGURE 13. Mean density profiles in Baggensfjärden, Farstaviken and Ägnöfjärden for 33 measurment surveyings during the period Jun-94 to Nov-97. Sigma-T is the density in kg/m3 minus 1000

Because of the poor ventilation of the bottom water, Farstaviken is very sensitive to oxygen consuming organic matter disposed together with the municipal wastewater. A strong anaerobic condition was observed in the bottom water. The interface between oxygenated water and anaerobic conditions is called a redoxcline, see figure 14, which in Farstaviken often is situated deeper than the pycnocline (Lännergren 1997). This means that the basin water can be divided into three different chemical water qualities: oxygen saturated water with low salinity at the surface, water of higher salinity containing oxygen and water of higher salinity with anaerobic conditions.

FIGURE 14. Pycnocline and redoxcline When the water body is oscillating the different water types are interacting with the sediment interface. During the period of municipal wastewater discharge (1950-1968) the organic compounds consumed more oxygen during decomposition than was mixed in by the wind and consequently an anaerobic condition was permanently established in the bottom water. As seen in figure 15 the depth of the interfaces between the different water layers are fluctuating several meters up and down. This means that a large area of the sediment surface is exposed to a changing chemical environment.

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depth redoxcline

depth (m) 0

depth pycnocline

4 8 12 16 20 feb93

aug93

feb94

aug94

feb95

aug95

feb96

aug96

feb97

aug97

feb98

aug98

feb99

aug99

Figure 15. The depth at which the pycnocline and the redoxcline occurred during the period Feb-93 to Nov-99 (Lännergren 1999) Oxygen mixed in by the wind and transported down in the water is consumed by decomposing organic mater. A balance will occur and the redoxcline will move up and down depending on wind and organic production. If extra organic matter is added e.g. with wastewater discharge, the balance will be changed. The transport of oxygen is obstructed by density stratification such as indicated by the pycnocline. In Figure 15 the redoxcline occurs closest to the surface in summer when organic production is high. At the same time the density stratification is strong, due to higher temperature in the surface water. The pycnocline occurs at a deeper water depth in the autumn, probably due to strong wind this time of the year. The deeper the pycnocline is situated the less strong turbulence induced by the wind will reach that depth and the less oxygen will cross the pycnocline. The sediment in deep layers that has the strongest anaerobic conditions also contains methane gas. This could clearly be seen on side-scan sonar images. (Anonymous. 1998a)

Hard echo

Soft echo

Soft echo with gas

FIGURE 16. Side scan sonar map of Farstaviken (Cato 1999)

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Field investigations. The inner shallow part was investigated (Öberg 1999) to compare with samples from 1976 and 1984. Core sampling plastictubes had a diameter of 50 mm. They were pressed down 2 meters below sediment surface. The upper 30 cm of the cores was mixed separately. Five cores were analysed. A known volume and weight of about 100 grams of the sediment where boiled 1 minute with 100 ml 2M HCL. After depositing, 40 ml was used for analysing with ICP equipment (Inductively Coupled FIGURE 17. Inner shallow area Plasma). The sediments were dried with sampling points from 1976, and weighed to achieve the dry 1984 and 1999 weight. An estimated amount of Pb, Zn and Cd was calculated from the average of the five samples. Similar techniques were used in the 1976 and 1984 studies. The deeper bottom was investigated to find out how far the pollutant had spread from the source point and how the deposition have changed historically on the accumulation bottoms. Farstaviken and the neighbouring basin Baggensfjärden were investigated. (Anonymous. 1998a). First the bottom was mapped with Side-Scan Sonar technique for detecting soft accumulation bottoms. A map showing the area of the soft bottoms was drawn and core samples were taken in sediment accumulation areas. The sediment surface at the accumulation areas is assumed to be representative for recent year. FIGURE 18. Map with sample points (Anonymous. 1998a).

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Analysis of the Zn, Pb and Cd content from 4 different investigations are displayed in order from the inner east part of Farstaviken, Fig 19. The concentration of Ni is added as a reference. mg/kg ds 1200 Cd*100 1000

Pb Zn

The strait

800

Ni*10

600 400

200 0 ÖC

UFA

SGU SW F 55

UFB

ÖB

UFC

ÖA

UBA

UBB

SGU 54

UBC

UBD

UBF

UBG

UBH

UBI

UBJ

UBK

SW B

UBL

UBM

UBN

UBO

Sample points

Figure 19. Concentrations of Zn, Pb and Cd in the surface of the sediment at 24 different locations in a gradient from the inner East part of Farstaviken. The data noted ÖC,ÖB and ÖA refer to "Öjermark 1997", SGU to "Cato 1999", SW to "Lännergren 2000"and the rest to"Anonymous 1999". Samples in the deeper areas were taken in a gradient from the source point (Fig 20). The equipment used was a "Gemini-sampler" which gives two parallel cores of which one was used for analyses and the other was cut by length to show the vertical profile (Anonymous 1998a). Depth profile

Farsta C

Farsta B

Farsta A

Baggen A

Figure 20. Sample points in Farstaviken and the first one in Baggensfjärden The vertical profile of the sediment cores (Fig.21) shows layers undisturbed from biologic activity, which is a typical sign of pure oxygen conditions. The yearly sedimentation includes more organic matter in the summer when more light and higher temperature improve the reproduction of algae and plankton. When they die and settle to the sedimentation bottoms they consume oxygen while decomposing. This enhances sulphide forms of metal compounds in the sediment. Especially the iron sulphides give a black appearance with the consequence that summer layers are more black than winter layers. During the period of municipal wastewater discharge 17

(containing a lot of organic matter) the whole yearly layer appears black. This is clearly seen in Fig 21, Farsta B. The thickness of the layer corresponding to this period is decreasing with the distance from the source point, which is in line with what is illustrated in Fig 3. In the sample Baggen A this black sedimentation period is not visible, which indicates that more oxygen was present here but still not enough for the bottom fauna to actively disturb the yearly layers.

Farsta A

Farsta B

Farsta C

Baggen A

Figure 21. Vertical sample profiles from sampling points Farsta A, Farsta B, Farsta C and Baggen A

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The layers are much thinner inside Farstaviken than in Baggensfjärden, indicating less yearly sedimented material. A 2 meter long sample core was taken at 15 meters depth close to "Farsta A" (Fig 20) in the winter of 2001. It showed that the layered sediment started at a depth corresponding to about year 1900. Before that the sediments were olive green without layers.

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CONCLUSIONS The field investigation shows that the surface layer of sediment still has higher concentrations inside Farstaviken. This indicates resuspension and spreading from the inner shallow part or from matter settled on slopes. Investigation of the sediment in a vertical profile gives a historical record of the activities disposing contaminates as well as oxygen consuming matter to the storm water catchment area of the water basin. The discovery of the "black sedimentation era" in the history of Farstaviken is of high interest for dating of the vertical profile of sediment sample cores in similar areas. The conclusion presented in paper 1 is that the mass balance evaluation as a method gives the right order of magnitude and an adequate distribution of disposed material including contaminant components, even when the historical discharge is embedded in more recent layers of sediment. The uncertainty depends mainly on lack of production data from the factory, few bottom samples and the fact that sediment and waste material temporarily are stored on hard bottoms and on different precision for applied analysis procedures. The simulation in paper 2 shows how the discharged clay particles followed the water movements in Farstaviken. The magnitude and the character of the exchange of water through the strait determines to which extent small particles were “flushed” out. The disposed material was graded, large particles concentrate near the source, smaller particles can settle far away, even in the outer basin. This is an important feature of the spreading of pollutants. From the modelling efforts in paper 3 it is shown that the results are comparable with measured data. This procedure can therefore, after some modifications, be a useful tool to utilise in Environmental Impact Assessments. It is also clearly shown that the water exchange of Farstaviken is mainly governed by the changes of density (salinity) and surface level fluctuations in the adjacent basin Baggensfjärden, which has a surface area 20 times larger than that of Farstaviken. According to the simulation in paper 2 the spreading of disposed particles during the disposal period, mainly 1950 -1970, most likely reached Baggensfjärden. The particles that could have been flushed out have been of small size and with a low sedimentation velocity. This means that they have been distributed over a large area of the sedimentation bottoms of Baggensfjärden. In paper 1 the missing part of lead in the mass balance, 16 tons, represents the upper limit for what could have been transported out from Farstaviken. If this was evenly distributed over the sedimentation bottoms of Baggensfjärden, 6 km2 (Anonymous. 1998a) during the period 1950 1970, it amounts to about 100 mg/m2year of lead. This is of the same order of magnitude as the background value, which means that if spreading to Baggensfjärden occurred, it would be difficult to detect it by sampling.

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REFERENCES Anonymous. 1998a. "Methods of Sedimentologic Investigations in Coastal Areas", Uppsala University, Report from PhD student course, Sweden Anonymous. 1998b. “Environmental Report of the Gustavsbergs Ceramic Factory", Gustavsbergs Fabriker, Report made for the Local Environmental Authority, Värmdö, Sweden Arvidsson, E.S., Aspfors, J., Gullmert, L. 1997. The Ceramic Factory of Gustavsberg, ISBN: 91-971577-3-2. 17-114 Cato, I. 1999, Surveyance Programme for Marine Geology, Swedish Geological Survey Hägg, G 1973, Allmän och oorganisk kemi, ISBN 91-20-03706-6 Lännergren, C., Johansson, P. 1997, Investigations in Stockholm Archipelago 1996. Stockholm Water Company Report. 36, 49-51 Lundmark, G. 1999, Personal interview, Environmental manager at the Gustavsbergs fabriker Öberg, O. 1999, Report from PhD course in water chemistry, Royal Institute of Technology, Stockholm, unpublished Öjermark, R. 1997 Metalls in the sediment of Farstaviken, Department of Natural Geography, Stockholm University.

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APPENDED PAPERS 1. Öberg, O., 2001, ASSESSMENT OF SEDIMENT CONTAMINANTS FROM CERAMIC PRODUCTION, A CASE STUDY OF FARSTAVIKEN. Presented at and accepted in proceedings from the 1st International Conference on Remediation of Contaminated Sediments, Oct, 10-12, 2001, Venice, Italy 2. Zhang, Z., Öberg O., 2000, A BAROCLINIC MODEL WITH SEDIMENT DEPOSITION IN A SMALL BASIN IN THE STOCKHOLM ARCHIPELAGO. Presented at and accepted in proceedings from the 4th International Conference on Hydro-science & -engineering, Sept., 26-29, 2000, Seoul, Korea 3. Öberg, O., 2001, WATER EXCHANGE IN FARSTAVIKEN - A SEMIENCLOSED BASIN WITHIN THE STOCKHOLM ARCHIPELAGO. Prepared for possible publication.

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