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Organic Rich freshwater Sediments (Sapropel) as Potential Soil Amendment for Recultivation of Areas Contaminated with Heavy Metals

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Sapropel is organic rich freshwater lake sediment with broad range of applications. Firstly it was named as "gyttja" in 1862 when Swedish scientist Hampus von Post called so a light-colored coprogenic deposit consisting of a mixture of plankton particles, mollusk shells, chitin remains from the exoskeletons of insects, pollen and spores of higher plants and mineral particles, formed in eutrophic water bodies. Term "sapropel" means "decayed sludge" -it was proposed by Lautenberg in 1901 and by G. Potogne in 1904. Sapropel relates to renewable natural resources and is typically found only in freshwater basins; however, usually this term is used in saline aquifer stratigraphy studies. Sapropel's chemical composition and peculiarities of different minefields are significantly different and defined by its formation conditions and by lakes' flora and fauna. Sapropel as it contains organic matter is able to bind metal ions and change their speciation forms in soils forming stable complexes. The ability to form complexes with metal ions depends on the type of soil, type of metal, as well as quantity of sapropel as soil amendment. The main sapropel reserves are found in the lake-bottom sediments -reserves in Latvia are estimated as 800-900 million m 3 or 170-190 million tons (with moisture content of 60%). In 1957-1967 more than 250 lakes in Latvia have been studied in detail on sapropel reserves and properties, later from 1990-2000 more than 1300 lakes were studied additionally. There are 56 strongly and more than thousand potentially contaminated sites with heavy metals in Latvia. The aim of this paper is to give overview status description on theoretical possibilities to use sapropel as the agent for remediation of contaminated with heavy metals soil.
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Section Soils
595
ORGANIC RICH FRESHWATER SEDIMENTS (SAPROPEL) AS POTENTIAL
SOIL AMENDMENT FOR RECULTIVATION OF AREAS CONTAMINATED
WITH HEAVY METALS
Karina Stankevica
Juris Burlakovs
Maris Klavins
University of Latvia, Latvia
ABSTRACT
Sapropel is organic rich freshwater lake sediment with broad range of applications.
Firstly it was named as “gyttja” in 1862 when Swedish scientist Hampus von Post
called so a light-colored coprogenic deposit consisting of a mixture of plankton
particles, mollusk shells, chitin remains from the exoskeletons of insects, pollen and
spores of higher plants and mineral particles, formed in eutrophic water bodies. Term
"sapropel" means "decayed sludge" - it was proposed by Lautenberg in 1901 and by
G. Potogne in 1904.
Sapropel relates to renewable natural resources and is typically found only in freshwater
basins; however, usually this term is used in saline aquifer stratigraphy studies.
Sapropel’s chemical composition and peculiarities of different minefields are
significantly different and defined by its formation conditions and by lakes’ flora and
fauna. Sapropel as it contains organic matter is able to bind metal ions and change their
speciation forms in soils forming stable complexes. The ability to form complexes with
metal ions depends on the type of soil, type of metal, as well as quantity of sapropel as
soil amendment.
The main sapropel reserves are found in the lake-bottom sediments - reserves in Latvia
are estimated as 800-900 million m3 or 170-190 million tons (with moisture content of
60%). In 1957-1967 more than 250 lakes in Latvia have been studied in detail on
sapropel reserves and properties, later from 1990-2000 more than 1300 lakes were
studied additionally.
There are 56 strongly and more than thousand potentially contaminated sites with heavy
metals in Latvia. The aim of this paper is to give overview status description on
theoretical possibilities to use sapropel as the agent for remediation of contaminated
with heavy metals soil.
Keywords: remediation, soil amendments, gyttya, resources, Latvia
INTRODUCTION
Sapropel is known with its properties already from the 19th century when Swedish
scientist Hampus van Post defined this class of bottom sediments of freshwater basins
originated as a result of anoxic decaying of faded aquatic vegetation, biota reminders
GeoConference on Water Resources, Forest, Marine and Ocean Ecosystems
596
and soil pieces drifted by water. Organic rich lake sediments studies can be related to
their application possibilities since sedimentary deposits of eutrophic lakes generally
have a high organic matter content (above 15%) [1], and therefore can be used as
equivalent to peat in different fields balneology, agriculture, livestock farming and
building.
Sapropel have finely dispersed and plastic structure; the colour from light pink to dark
brown, in natural state with high content of phosphorus it has dark blue colour; after
drying it becomes bright blue [2]. It relates to renewable natural resources and is a
unique natural organic feedstock - its sediments are typical only for freshwater basins.
Organic matter content determines sapropel value and application potential the more
is the organic matter in the sapropel, the more valuable it is and the better are
opportunities for its use. Combustion at different temperatures provides information on
mass losses moisture, organic matter and carbonate content. Higher concentrations in
Latvian organic lake sediments are common for metals of natural origin Ca, Fe and
Mg, which are discharged into water bodies as a result of rock weathering in the lake
catchment area. Heavy metal concentrations have been studied in sapropel, typically,
upper layers of sediments indicate larger anthropogenic impacts and higher
concentrations of metallic elements, but generally metal concentration is low and does
not cause adverse effects to aquatic organisms in the lakes [3].
Soil is a variable mixture of minerals, organic matter and water, what is capable of
supporting the most fundamental requirements for sustainable land use. Therefore the
quality of soil is fundamentally important and different technologies are used for the
remediation of industrial contamination. Contamination causes loss of land as a resource
as well as loss of property [4]. Heavy metal pollution of soil is an increasingly urgent
problem all over the industrialized world. Excessive concentrations of heavy metals in
soils result often from anthropogenic activities, such as from the mining industry and
treatment of metal ores, waste incineration, road transport, and the use of fertilizers and
agrochemicals [5]. Toxic heavy metal ions are non-biodegradable and tend to
accumulate in living organisms, causing severe disorders and diseases [6], [7]. Metal
ion complex formation is one of the most prominent interactions in nature and metal
complexation is of widespread interest. The strength of the interaction between organic
ligands and metals is usually expressed in terms of a stability constant of formed
complexes. Knowledge of stability constants enables the behavior of a metal ion with
one or more ligands to be modeled as a function of pH and reactant concentration [8].
Sapropel use as the soil amendment for treatment of contaminated soils had been
studied already at the end of 80-ties in 20th century, when radiocesium retention in soils
were studied. Application of selective to radionuclides amendments, based on organic
and mineral raw materials, including clay minerals, zeolites, sapropels, turf and other, is
very perspective agrochemical measure. Such countermeasures result in increase of soil
sorption ability to radionuclides and, therefore, decrease their availability to plant [9].
Later many works were conducted in Russian Federation, Ukraine and Belarus by
Konoplev, Moskalchuk et al [10], [11], [12], [13]. Development of composition and
technology of additives production for rehabilitation of soils contaminated by
radionuclides and assessment of their application efficiency was conducted [14], as the
topicality of domain raised after Fukushima event on 11th of March, 2011.
Section Soils
597
As amendment sapropel improves soil’s mechanical structure, it’s water consuming and
water retaining ability, gives humus increasing in soil on 2nd-3rd year, activates soil
processes. Product is providing to plants balanced nutrition with all fertilizers. It should
be mentioned that during mutual application of mineral fertilizers simultaneously with
sapropel toxicity of heavy metals is decreased, tubers remain clean and do not
accumulate heavy metals [10], [11], [12], [13].
This article is reporting on the opportunity of sapropel application as possible
amendment in soil for remedial actions in case of heavy metal contamination as it is of
great concern in Latvia and many other lands.
RESEARCH AND DISCUSSION ON APPLICATIONS OF SAPROPEL IN
REMEDIAL ACTIVITIES
The main terrestrial reserves of sapropel in Latvia are found in eastern part where most
of lakes are situated. There are estimated around 800-900 milj.m3 or 170-190 milj.t with
relative moisture content of 60%. In 1957-1967 more than 250 lakes in Latvia have
been studied in detail on sapropel reserves and properties [14], later from 1990-2000
more than 1300 lakes were studied additionally [15]. Map of fresh-water lake sapropel
potential of Latvia (Fig. 1) shows that main part of the sapropel prospects in Latvia are
situated in eastern part of Latvia and organic-silica sapropel is dominating mostly
everywhere. Only in Greater Riga Region, the very north and southwestern part of
Latvia silica sapropel is more widespread.
Fig. 1. Distribution of fresh-water lake sapropel and allocation of its types in Latvia compiled
by the main author according [15])
However, only some little part is studied in more detail and theoretically can be used as
the source for extraction for industrial needs. Last years more and more private
companies, land owners and universities (Fig. 2) are increasing their interest about
GeoConference on Water Resources, Forest, Marine and Ocean Ecosystems
598
sapropel potential in their properties and mostly ideas are concerning the use in
cosmetics and medicals production in future. However, the analysis of sapropel
sediments must be done in a complex way and as the soil amendment for contaminated
areas it can also show properties as the valuable material.
Fig. 2. Research of sapropel properties at the University of Latvia
Assessment of sapropel use for immobilization of heavy metals should include
determination of the main parameters of soils, sorbents and additives (composition of
soil solution, sorption properties of the solid phase, kinetic and equilibrium parameters
of heavy metal fixation), development of the methods to estimate the key parameters of
soil-additives mixtures using properties and ratio of the components as well as
determination of the efficiency of additives application for typical soils of contaminated
areas in Latvia. These studies would be with practical significance for developing
recommendations for their use in a wider scale.
Methods and procedures for the ascertaining of polluted and potentially polluted sites in
Latvia, as well as the procedures for financing, conditions for data collection and
utilization are regulated by the specific legislation [16], [17]. The applicability of
remediation technology is dependent on site-specific conditions, type of contaminants
and other factors. In Latvia there are outlined 56 territories [18], [19] contaminated with
heavy metals of 242, that now are numbered as contaminated and fixed in the National
Register of Contaminated Territories in Latvia [20].
The applicability of remediation technology is dependent on site-specific conditions,
type of contaminants and other factors. The immobilization of heavy metals is to be
considered with the use of amendments [19], [21], e.g., sapropel. Table 1 is giving the
Section Soils
599
list where soil amendments can be theoretically used as soil remediation agents. 13 of
these areas are situated in Riga or in Greater Riga region.
Table 1. List of main contaminated sites can be treated using organic soil amendments
No.
Location, name
Type of contamination
1
JSC Lokomotīve, Daugavpils, industrial area
HM1, OP2
2
Liquid toxic substances dump, Jelgava
HM, elements in anionic form,
OP
3
Zvārde tank polygon, former military area
OP, HM
4
Former Pesticides Warehouse, Viļāni
DDT3, HM
5
Olaine dump site
HM
6
Priedaine dump site
COD, ammonia, OP, HM, N
7
Bangas, former Soviet Army missile base,
former military area
OP, HM
8
Lacon Ltd., former Soviet Army fuel base, Riga Port
OP, HM (Pb)
9
Mekora, Ltd., Former 145. Military Factory
OP, COD, HM (Ni, Zn, Cu, Pb)
10
Kleisti dump site, Riga
HM (Zn, Pb, Cr), COD, N,
elements in anionic form
11
Bieķengrāvis, former hazardous waste dump
COD, OP, N, HM (Cu)
12
Riga Gardening Pesticide Warehouses (former)
OP, HM
13
”Energoautomātika” former industrial area, Riga
Pb, As
14
Vega Stividors, Riga Port, industrial area
HM, As
15
BLB, Riga Port, industrial area
HM, OP, HM (As)
16
Magnāts Ltd., Riga Port, industrial area
OP, HM (Pb)
17
Grand Ltd. former light bulb factory, brownfield
OP, HM (Pb, Cu)
18
SJSC Latvenergo TEC-1, Riga, brownfield
OP, elements in anionic form,
ammonia, HM
19
Former mordant site, Ancene
Amines, HM (Cu, Zn)
1 heavy metals and their compounds
2 oil products
3 dichlorodiphenyltrichloroethane, 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane
4 contamination with organic substances, creating a high level of chemical oxygen demand
The objective of the possible assessment would be to develop effective and ecologically
safe amendment based on natural raw material - sapropel and to develop methods and
models for forecasting effectiveness of countermeasures as part of remediation of soils
contaminated by heavy metals. Bottom sediments of freshwater lakes or sapropels
surpassing by content of nutrients and microelements could be of special interest among
such amendments in areas with a little distance between perspective mining place of
sapropel and areas of potential remediation. This sapropel could be used in a sustainable
way some part in production of medicine and cosmetics, some as fertilizers in
agriculture and the remaining part as remediation agent helping to immobilize heavy
metals in contaminated areas. The influence of sapropel to immobilization process must
be studied better in order to understand better the sorption capacity based on ion
exchange and ligand formation processes.
GeoConference on Water Resources, Forest, Marine and Ocean Ecosystems
600
CONCLUSIONS
The in situ and ex situ technologies are used for remediation of contaminated sites. The
future of site remediation in Latvia can be done by using soil amendments,
separation/concentration, chemical treatment, soil washing and flushing,
phytoremediation technologies or combined. In the National Register of Contaminated
Territories in Latvia there are included 242 contaminated sites, 56 of which can be
counted as mainly contaminated with heavy metals. Sapropel reserves in Latvia
Republic are estimated as 800-900 milj.m3 or 170-190 milj.t with relative moisture
content of 60%. Sapropel use for immobilization of heavy metals should be done by
determination of the main parameters of soils, sorbents and additives (composition of
soil solution, sorption properties of the solid phase, kinetic and equilibrium parameters
of heavy metal fixation), development of the methods to estimate the key parameters of
soil-additives mixtures using properties and ratio of the components as well as
determination of the efficiency of additives application for typical soils of contaminated
areas in Latvia. The opportunity to collaborate within the EU remediation framework of
historically contaminated territories can help to run-up with remediation projects in
problematic areas. The remediation will demand multidisciplinary approach in order to
have the successful result.
Acknowledgements
Financial support by the European Regional Development Fund (ERDF) project
“Innovation in Peat Studies for Development of New Applications” is acknowledged.
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