Jean B. Diatta*, Witold Grzebisz* CALCIUM AS A FACTOR

Ochrona Środowiska i Zasobów Naturalnych
nr
41, 2009 r.
Jean B. Diatta*, Witold Grzebisz*
CALCIUM AS A FACTOR MITIGATING NEGATIVE IMPACT OF HEAVY
METALS ON SOIL AND PLANT
I. SOIL CHEMICAL CHANGES AS INDUCED BY CALCIUM-BEARING COMPOUNDS
WAPŃ JAKO CZYNNIK ŁAGODZĄCY UJEMNE DZIAŁANIE METALI
CIĘŻKICH NA GLEBĘ I ROŚLINĘ
I. ZMIANY CHEMICZNE GLEB WYWOŁANE ZWIĄZKAMI ZAWIERAJĄCYMI WAPŃ
Słowa kluczowe: zanieczyszczenie metalami, łagodzący wpływ Ca, wapno palone, fosforyt, wapno jeziorne, wapno krzemianowe.
Key words: metal contamination, Ca mitigation effect, quicklime, phosphate rock, lacustrine lime, silicate lime.
Głównym założeniem przy przygotowaniu niniejszego doświadczenia było wykazanie celowości stosowania wapnia jako pierwiastka przeciwnego do metali ciężkich na glebach
nimi zanieczyszczonych. W tym celu zastosowano następujące związki zawierające wapń
(CaBC): wapno palone (QL), fosforyt (PR), wapno jeziorne (LL) i wapno krzemianowe (SL),
na glebę kwaśną (pHCaCl = 5,5), bardzo zanieczyszczoną przez hutę miedzi. Związki za2
wierające wapń (CaBC), po uprzednim oznaczaniu ich ogólnej zasadowości (CaO), dodawano do gleby na podstawie kwasowości hydrolitycznej gleb (0,5 i 1,0 HA). Każdy obiekt
(CaBC x HA) składał się z 600 g gleby i powtórzony był czterokrotnie. To samo dotyczyło
obiektu kontrolnego. Całkowity czas inkubacji trwał 28 tygodni, próbki gleb pobierano co
7 tygodni. Oceny zawartości wapnia w obiektach dokonano na podstawie ekstrakcji wodą
(Ca wodnorozpuszczalny) i 1 mol CH3COONH4, pH 7,0 (Ca wymienny). Metale ciężkie
ekstrahowano przy użyciu chemicznych testów 0,10 mol NaNO3 (biodostępny) i 0,005 mol
DTPA, pH 7,3 (chelatowany). Wyniki doświadczenia wykazały, że dodanie do gleby CaBC
doprowadziło do zmniejszenia stężeń metali w roztworze glebowym wraz z upływem czasu, przy czym najbardziej fosforytu (PR) przy obu dawkach 1,68 i 3,36 g na 600 gleby od* Prof. nadzw. dr hab. Jean B. Diatta i prof. dr hab. Witold Grzebisz – Katedra Chemii Rolnej,
Uniwersytet Przyrodniczy w Poznaniu, ul. Wojska Polskiego 71F, 60-625 Poznań;
tel.: 61 848 77 83; e-mail: [email protected]
64
Calcium as a factor mitigating negative impact of heavy metals on soil and plant
powiednio do 0,5 i 1,0 HA oraz wapna krzemianowego przy dawce 0,74 g na 600 gleby
(czyli 1,0 HA). Ten ostatni był mniej skuteczny w porównaniu do fosforytu przy dawce 1,68
g na 600 gleby (0,5 HA). Miedź występująca w największej ilości w badanej glebie była silnie związana przez kompleks sorpcyjny gleby, na równi z ołowiem, którego ilość w glebie
w dużym stopniu zmniejszyło zastosowanie CaBC. Zastosowanie związków zawierających
wapń na podstawie kwasowości hydrolitycznej okazało się niedostatecznym czynnikiem
do skutecznego złagodzenia negatywnego działania metali na gleby, zwłaszcza w stosunku do miedzi.
1. INTRODUCTION
The natural capacity of soils usually develops for counteracting and mitigating threatening substances and chemicals is a resultant of interactions of a bulk of mineral as well
as organic colloids. These along with the soil reaction (pH) create a specific buffering
power, whose efficiency has been frequently ascribed to the prevailing levels of alkaline versus acid ions. Several decades ago, Graham [1959] has introduced the concept
of ‘ideal soil’, where he suggested, that 65 per cent of the exchange complex should
be occupied by calcium (Ca), 10 per cent by magnesium (Mg), 5 per cent by potassium
(K), and 20 per cent by hydrogen (H). In the same way Liebhardt [1981] relaxed the optimum specific ratios by proposing, that 65 to 85 percent of the cation exchange complex should be occupied by Ca, 6 to 12 percent by Mg, and 2 to 5 percent by K. Later
on, Eckert [1987] defined normal values for the exchangeable cations as 60 to 80% for
Ca, 10 to 20% for Mg, and 2 to 5% for K. The order reported for these alkaline elements
explicitly reveals, that calcium should be considered as the real factor responsible geochemical exchange processes. Thus the magnitude of these processes is strictly related
to the substantial fact, that its level predominates in the exchange complex [Critter and
Airoldi 2003].
The progressive loadings of heavy metals into agricultural and forest ecosystems may
affect the soil chemistry of alkaline cation, basically. Several studies [Abd-Elfattah and
Wada 1981; Gao 1997; Diatta et al., 2003] have been carried out on heavy metal inputs
into soil ecosystems, their reactions (adsorption-desorption) with soil colloids and possible environmental concerns. The direct negative impact of heavy metals in soils as well
as to living biota (i.e. the fauna and flora) is a resultant of the capacity of soils to mitigate
the harmful effect via processes boosting the buffering capacity [Atanassova and Okazaki 1997; Diatta et al., 2000]. Soils are an important sink for heavy metals due to their high
or relatively high retention capacities. In many cases, much of these metals in soils is not
present in readily available fractions, which may vary from <1 to 10% for Pb, for instance
[Boruvka et al. 1997; Kabala and Sing 2001]. Therefore their persistence and mobility in
soils should be dictated by the extent to which their are retained to solid phases. This par-
65
Jean B. Diatta, Witold Grzebisz
ticularity is a function of reactions affecting surface charge and ion density [Sokołowska
1989; Diatta 2002].
Since metals contained in soils may be released simultaneously as a result of chemical and microbial processes, it is then expectable that their competitive and selective retention by soils may be of major importance in determining their phytoavailability [Berti and
Jacobs 1996; Fontes et al. 2000]. Hence understanding mechanisms of metals, particularly
Cu and Pb retention in soils is particularly important as these reactions dictate the strength
of the metal-soil surface interaction. On a relative basis, exchange reactions may render
these metals most labile, whereas inner sphere complex formation and coprecipitation with
soils surface cause Cu and Pb to be retained strongly and in many cases nearly irreversible
[McBride 1989].
Several factors are involved in the process of the mitigation of metal negative effects
under conditions of contamination or even pollution. These are based on the natural capacity/power of metals impacted soils to neutralize or attenuate the labile i.e., active as well
exchangeable metals forms [Mulligan and Yong 2004; Odencrantz et al. 2003; Brady et al.
2003]. In many cases the levels of labile metals forms become significantly high to be maximally buffered by soil colloids. Therefore the „strengthening” of buffer properties is assisted
by the application of so-called stabilizer on the basis of primarily established criteria. However, the focus on the direct of indirect role of calcium, solely in the mitigation process is
generally omitted. Some attempts have been undertaken through equilibrium studies [Diatta et al. 2000; Critter and Airoldi 2003], which in fact exhibit the role of calcium more at colloids interface level.
The purpose of the investigation was to evaluate the efficiency of calcium from calcium
bearing compounds (CaBC) for mitigating the impact of copper and lead in a soil polluted by
Cu smelter activity. The specific assumption was to exhibit the role of Ca as a counter element for metals earlier retained by the soil sorptive complex.
2. MATERIALS AND METHODS
Location of the soil sampling. The soil used in the current study was collected at
0–20 cm (500 m East from the main emitter) in 2002 within the area impacted by the
Glogow Copper Smelter (51°39’32.6’’ N 16°04’49.9’’ E, Poland). The smelter was established in 1970’s and the zone mostly contaminated by heavy metals (copper mainly) was
taken out of agricultural utilization and afforested (poplars, maples) to create the so called
the „Sanitary Belt”.
Physical and chemical analysis. Prior to basic analyses the soil sample were airdried and crushed to pass through a 2.00 mm mesh sieve. Particle size distribution was
determined according to the method of Bouyoucos-Casagrande modified by Prószyński
66
Calcium as a factor mitigating negative impact of heavy metals on soil and plant
[Mocek et al. 2000]. Organic carbon was determined by the dichromate wet oxidative method according to Tiurin [Filipek 1999] and soil pH potentiometrically, according to Polish
standard [1994]. The cation exchange capacity was obtained by summation of exchangeable alkaline cations and acidity according to Thomas [1982]. Iron (Fe) and manganese
(Mn) were extracted by using both the citrate-bicarbonate-dithionite (CBD) and the acidammonium-oxalate (Ox) methods according to McKeague and Day [1966] and Mehra and
Jackson [1960]. The assessment of the specific surface area was undertaken by applying
the EGME saturation (Ethylene Glycol Monoethyl Ether) method as reported by Carter et
al. [1986].
Heavy metals were assayed by using 6 moles HCl·dm-3 (extracted fractions designated as the „pseudo total” content) and additionally by the 0.005 moles DTPA dm-3 method according to Lindsay and Norvell [1978], (chelated fractions). Unbuffered soil tests like
0.10 moles NaNO3·dm-3 [Gupta and Hani 1989] and deionized water were additionally used
for extracting respectively bioavailable (Bio) and active (Act) metal fractions. Physical and
chemical details of the investigated soil are listed in Tables 1 and 2.
Table 1. Selected physical and chemical characteristics of the investigated soil
Tabela 1. Wybrane właściwości fizyczne i chemiczne badanej gleby
Sand
(2.0–0.02
mm)
660
a
Silt
Clay
(0.02–0.002
<0.002 mm
mm)
g·kg-1
220
120
Corg.
8.8
pHCaCl
2
5.5
SSAa
(m2·g-1)
CECb
cmol(+)·kg-1
9.8
10.1
– Specific surface area; b – Cation exchange capacity.
Table 2. Metals extracted by different chemical tests from the investigated soil
Tabela 2.Metale ekstrahowane z badanej gleby przy użyciu różnych testów
Cu
2041.3
1
Pb
Zn
6 moles HCl·dm-3
540.0
Cd
68.7
0.80
S-SO4
mg·kg-1
76.0
Fe
Mn
CBD1
Ox2
CBD
Ox
2533
1931
171
194
Citrate-Bicarbonate-Dithionite; Acid ammonium Oxalate.
2
Concept, experimental design and incubation process. It was assumed, that the
low pH (tab. 1), i.e., high protons level favors metals activity and both may be counteracted
by appropriated concentrations of calcium ions in the soil. Therefore calcium-bearing compounds (CaBC): quicklime (QL), phosphate rock (PR), lacustrine lime (LL) and silicate lime
(SL) were incorporated into the acid soil on the basis of the hydrolytic acidity (HA). Prior to
CaBC addition, their acid neutralizing capacity was determined and converted to CaO. Table 3 resumes basic information dealing with these details.
67
Jean B. Diatta, Witold Grzebisz
Table 3. Amounts of CaBC-based CaO incorporated to the investigated soil on the basis of hydrolytic acidity (HA)
Tabela 3.Ilości związków zawierających wapń (CaBC) dodane w oparciu o CaO do badanej gleby na podstawie kwasowości hydrolitycznej (HA)
Calcium-bearing compounds
(CaBC)
CaO
(%)
Quicklime (QL)
Phosphate rock (PR)
Lacustrine lime (LL)
Silicate lime (SL)
83.7
9.0
40.7
41.1
Amount of CaBC added on the basis of
0.5 HA*
1.0 HA
0.5 HA
1.0 HA
t CaBC·ha-1
g CaBC 600 g-1·soil
0.18
0.36
0.905
1.81
1.68
3.36
8.39
16.78
0.38
0.76
1.86
3.71
0.37
0.74
1.84
3.68
* Hydrolytic acidity (HA); for convenience, 0.5 HA and 1.0 HA are designated a and b, respectively in
Graphs 1, 2, 3 and 4.
Each treatment (i.e. CaBC x HA) consisted of 600 g soil and was replicated 4 times. The
same applies for the control. These treatments were kept moist at 75% FWHC (Field water
holding capacity) and incubated for 28 weeks at 18±2oC. The whole incubation period lasted
28 weeks of which soil sampling (120 g) was performed at each 7 weeks time interval. The
collected soil samples were chemically analysed as described in the sub-section „Physical
and chemical analysis”. All performed chemical tests were run in duplication and metals as
well as other elements were determined by the FAAS method (Flame Atomic Absorption
Spectrophotometry, Varian 250 plus). Simple statistical evaluations were done by using the
Statgraphics® software and Excel® sheet facilities.
3. RESULTS AND DISCUSSION
The investigated soil is classified as loamy sand [Soil Taxonomy – USDA 1975] and
Dystri – Gleyic Fluvisols according to WRB-84 [1998], which implies that its natural capacity for buffering cationic elements should be appreciable (Tab. 1). This is supported
by the relatively high level of the sum: silt+clay amounting to 340 g·kg-1 and the content
of organic carbon, 8.8 g·kg-1. These parameters are practically invaluable in creating and
shaping the size of both the specific surface area (SSA) and cation exchange capacity
(CEC), which in turn are the core of several geochemical processes involved in the alleviation of heavy metal (Cu, Pb and Zn among others) direct impact on soil as well as living organisms.
It should be mentioned, that the recorded soil reaction, i.e., pH 5.5 (in 0.01 mole CaCl2)
may be considered as acidic and then quite incompatible with the magnitude of SSA and
CEC. In fact, the levels of Cu, Pb basically and Zn slightly (Tab. 2) may have been responsible for the low pH value. Additional care should be given to the significantly high level of
sulphate (76.0 mg·kg-1) originating from the processing of Cu ores. Therefore the cumula-
68
Calcium as a factor mitigating negative impact of heavy metals on soil and plant
tive effect of both of Cu, Pb and S-SO4 are directly concerned in this matter. Further geo-
chemical interactions are intended to govern or modify the chemistry of Ca versus metals
and these are mediated by the soil reaction.
Effect of calcium-bearing compounds (CaBC) on soil pH and Ca status. The
incorporation of CaBC induced both pH changes in one hand and led to a raise in the
content of labile Ca fractions accordingly to treatments (Fig. 1). It should be decidedly
mentioned that pH varied along with CaBC rates, i.e., 0.5 HA and 1.0 HA and reached
its highest value (pH = 6.2) in the treatment receiving phosphate rock (PR) at 1.0 HA.
Amounts of Ca incorporated leveled at 215.4 and 430.8 mg·kg-1 for the quicklime (QL) and
1090.7 and 2181.4 mg·kg-1 for PR treatments, at 0.5 HA and 1.0 HA, respectively. This
is explicitly outlined by the progressive increase, as compared to the control (O). The dynamics of labile forms of Ca reported by Critter and Airoldi [2003], has pointed out on the
particular role of Ca in the so-called exchangeability and interference mechanisms versus
other metallic ions. If we assume the water extractable Ca (Ca-H2O) to play the interfer-
ence role, therefore the ammonium acetate Ca (Ca-Exch) decidedly should be involved
in the second process.
The chemical composition of CaBC relies by essence on the fact, that calcium is not
the sole element to be taken under consideration, otherwise the dominating one (71.4% in
CaO; ca 40% Ca and 19.5% P in Ca3(PO4)2; Lacustrine lime (LL), 28.8%, ca 35% Ca and
24% Si in CaSiO3). In the case of PR treatments, calcium release may be related chemically
to the concentration of phosphates ions [Ma and Rao 1999] and the latter ones to be indirectly and intermediately involved in the reaction with heavy metals. The chemical efficiency
of phosphates ions seems to be substantially hampered due to the high levels of labile Ca
forms as reported in Figure 1.
Fig. 1. Effect of calcium-bearing compounds (CaBC) on pH changes and calcium status of treatments; 0.5 HA = a, 1.0 HA = b, (More details, see Table 3)
Rys. 1. Wpływ związków zawierających wapń (CaBC) na zmiany pH oraz stan wapnia w obiektach; 0,5 HA = a, 1,0 HA = b (więcej szczegółów w tabeli 3)
69
Jean B. Diatta, Witold Grzebisz
Ca aqueous and exchangeable versus Cu bioavailable and chelated. Geochemical changes induced by Ca incorporation may proceed via hydrolysis reactions of the concerned metal species (Ca, Cu and Pb) and most frequently are decidedly dictated by the
levels of the so-called labile forms, i.e., aqueous, bioavailable, exchangeable and chelated.
Under conditions of the current study, it should not be omitted the physical and chemical
feature of metals, which seems to be pertinently decisive in assessing the role of Ca in the
direct or intermediary alleviation of Cu, and Pb negative effect on soils. According to Sanderson [1983], the electronegativity of the above mentioned metals varies as follows: Ca –
1.0, Cu – 1.90 and Pb – 2.33, which implies, that lead and copper are decidedly strongly
attracted by soil colloids [Abd-Elfattach and Wada 1981; Christophi and Axe, 2000; Diatta
et al. 2003] as compared to Ca. Therefore the levels of Ca in contaminated or polluted soil
must be higher enough to counteract investigated contaminants.
Data reported in Figure 2, explicitly showed the direct quantitative effect of Ca source
on its labile as well as exchangeable forms in the soils. The mitigation process may be formulated as follows:
·
·
Ca water extractable (Ca-H2O) versus biological (Cu – Bio) and chelated (Chel – Cu),
Ca exchangeable (Ca-Exch) versus biological (Cu – Bio) and chelated (Chel – Cu).
The Ca-mitigation assessment based on the first case is particularly interesting due to
the fact that Ca-H2O occupies the intermediary position, i.e., between Chel – Cu and Cu –
Bio. This implied that, irrespective of CaBC rates, the level of Ca-H2O was sufficient enough
to control only active Cu forms, hence to reduce their resorption to the soil phase.
Fig. 2. Changes of Ca aqueous (Ca-H2O) and exchangeable (Ca-Exch) levels and Cu bioavailable (Cu-Bio) and chelated (Cu-Chel) as induced by CaBC incorporation
Rys. 2.Zmiany w ilości Ca wodnorozpuszczalnego (Ca-H2O) i wymiennego (Ca-Exch) oraz Cu
biodostępnego (Cu-Bio) oraz schelatowanego (Cu-Chel) pod wpływem CaBC
70
Calcium as a factor mitigating negative impact of heavy metals on soil and plant
Such interactions of Ca-Cu in extremely polluted soils have been a topic of detailed
equilibrium/kinetic study [Diatta et al. 2000]. Authors have reported that the presence of Ca
shaped Cu sorption/ retention by soil colloids via non-specific processes and the higher the
Ca levels the strongest the processes become. The practical significance of these mechanisms relies on the efficient competitivity of Ca for retention sites under its high levels. Then,
the displaced or desorbed Cu ions hardly are sorbed back and strongly interfere with Ca
ions in the bulk solution, where the latter one undergoes hydrolysis reactions significantly
decreasing the activity of Cu. The pertinence of the approach reported in the current study
is supported by data of McBride [1989] and Critter and Airoldi [2003].
The evaluation made on the basis of Ca-Exch outlined the specific role of exchangeability processes in controlling quite the whole level of both Cu-Bio and Cu-Chel for all
CaBC. Most importantly is the quantitative prevalence of Ca over Cu and the geochemical
significance of this state. In fact the Cu-Chel fraction involves two sub-fractions, i.e. Cu-Biol
and namely, exchangeable Cu (Cu-Exch). Reactions and interactions occurring at this level
are of prime importance for further evaluation of Ca-based mitigation effect on copper and
heavy metals, in general. According to Christophi and Axe [2000], the competition established between heavy metals for active colloid sites and the resulting impact on the whole
chemical status of colloids may not be limited to the „pure” electronegativity feature, solely,
but also the bulk amounts of exchangeable Ca. Data reported in Table 4 decidedly shows
the difference in the amount of total Ca incorporated into particular treatments and their post
effect in the system.
Table 4. Amounts of Ca incorporated to the investigated soil on the basis of hydrolytic acidity (HA)
Tabela 4. Ilości Ca wprowadzonego do badanej gleby na podstawie kwasowości hydrolitycznej (HA)
Calcium-bearing compounds
(CaBC)
CaO
(%)
Quicklime (QL)
Phosphate rock (PR)
Lacustrine lime (LL)
Silicate lime (SL)
83.7
9.0
40.7
41.1
Amount of Ca incorporated on the basis of:
0.5 HA*
1.0 HA
0.5 HA
1.0 HA
kg Ca·ha-1
mg Ca·600 g-1
120.0
240.0
601.2
1202.4
672.0
1344.0
3366.6
6733.2
110.0
220.0
551.1
1102.2
130.0
260.0
651.3
1302.6
* Hydrolytic acidity (HA).
It may be assumed, that the capacity of the investigated soil was significantly high to
adsorb additional amounts of Ca, which in turn could be expected to control and shape Cu
chemistry. The observed process may be summarized consequently as follows: the relatively weak attraction of Ca by soil colloids must be compensated strictly by its high amounts in
order to control efficiently high Cu concentrations [Abd-Elfatach and Wada 1981; Atanassova and Okazaki 1997].
71
Jean B. Diatta, Witold Grzebisz
Ca aqueous and exchangeable versus Pb bioavailable and chelated. The degree
of soil pollution by Pb was significantly lower as compared to copper, whose amounts were
ca 4 times higher. This implies therefore, that any quantitative as well as qualitative calcium
effect towards Pb may be more pronounced under conditions of the current study.
Fig. 3. Changes of Ca aqueous (Ca-H2O) and exchangeable (Ca-Exch) levels and Pb bioavailable (Pb-Bio) and chelated (Pb-Chel.) as induced by CaBC incorporation
Rys. 3. Zmiany w ilości Ca wodnorozpuszczalnego (Ca-H2O) i wymiennego (Ca-Exch) oraz Pb
biodostępnego (Pb-Bio) oraz schelatowanego (Pb-Chel.) pod wpływem CaBC
Amounts of Pb bioavailable (Pb – Bio) as illustrated in the Fig. 3 explicitly show, that both
Ca forms i.e., water extractable (Ca-H2O) and exchangeable (Ca-Exch) efficiently control-
led Pb chemistry in the investigated soil. This effect proceeded irrespective of the rates and
the type of CaBC incorporated. Lead is reported to exhibit high affinity for most soil functional
groups [McBride 1989; Diatta 2002] as a result of small hydrated radius (0.401 nm, electronegativity = 2.33) which in turn creates suitable conditions for electrostatic and inner-sphere
surface complexation reactions [Rawat et al. 1990]. Processes involved in Pb sorption should
be of two basic types: specific and nonspecific exchange reactions particularly. It was demonstrated by Schulthess and Huang [1990], that the first degree of hydrolysis of Pb2+ ions (Pb2+
→ PbOH+) occurs at pH = 5.90. According to Altin et al. [1999], in neutral to alkaline soil conditions, amounts of hydrated metals at the first degree of hydrolysis increase, which simultaneously enhances metal adsorption/retention. The following reaction is generally suggested:
Me2+(aq) + n H2O → Me(OH)n2-n + n H+
Most of soil solutions pH (Fig. 1) fluctuated between 5.5 and 6.2, particularly in treatments with phosphate rock (PR). Therefore it can be expected, that significant concentrations of Pb2+ may potentially undergo hydrolysis process to generate PbOH+ ions preferentially adsorbed over Pb2+ ones as pointed out by some researchers [Sauvé et al. 1998b].
72
(aq) ++ nnHH2O
→ Me(OH)n
Me(OH)n2-n2-n ++nnHH+ +
Me
Me2+2+(aq)
2O →
Most
Most ofof soil
soil solutions
solutions pH
pH (Fig.
(Fig. 1)1) fluctuated
fluctuated between
between 5.5
5.5 and
and 6.2,
6.2, particularly
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ittheir
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that the amounts
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and
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inTable
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Most
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1)pH
(Fig.
1)5,itbetween
fluctuated
5.5
between
and
5.5particularly
and 6.2, particularly
in
not in position to alleviate the negative effect of Cu and Pb.
treatments
treatments
with calcium
phosphate
with
phosphate
rock
(PR).
rock
Therefore
(PR). itTherefore
can were
be itexpected,
canininbe that
expected,
significant
that signific
amounts ofof soil-born
soil-born
exchangeable
calcium
i.e.,
before
CaBC
incorporation,
were
not
amounts
exchangeable
i.e.,
before
CaBC
incorporation,
not
+
concentrations
concentrations
of Pb2+ mayofpotentially
Pb2+ may undergo
potentially
hydrolysis
undergo process
hydrolysis
to generate
process to
PbOH
generate
ionsPbOH+ io
position
alleviatethe
thenegative
negative
effect
Cuand
and
Pb.
position
alleviate
ofofCu
Pb.
Table 5. Ratios
oftotoexchangeable
Ca effect
to
chelated
Cu
and
the particular treatments
2+ Pb for 2+
preferentially
preferentially
adsorbed over
adsorbed
Pb ones
over as
Pb pointed
ones as
outpointed
by some
outresearchers
by some researchers
[Sauvé et al.,
[Sauvé et
Tabela 5. Stosunki Ca wymiennego
do
schelatowanych
Cu
i Pb dla
poszczególnych
obiektów
1998b]. This1998b].
explains
This
theexplains
complexthe
role
complex
of Ca in
role
processes
of Ca inleading
processes
to the
leading
mitigation
to theof
mitigation
heavy of hea
Table5.5.Ratios
Ratiosofofexchangeable
exchangeable
Ca
chelated
Cuand
andPb
Pbfor
forthe
the
particular
treatments
Table
Ca
totochelated
Cu
particular
treatments
0.5
HA*
1.0
HA
0.5 HA
1.0 HA
metals, copper
metals,
and
lead
copper
among
and
lead
others.
among
others.
sly
enhances metal
metal adsorption/retention.
adsorption/retention.
The following
following reaction
reaction
generally
y enhances
The
Calcium-bearing compounds
CaOisis generally
CaCu
Ca
Ca Exch
Ca
Tabela
StosunkiCa
Ca
wymiennego
doschelatowanych
schelatowanych
Cui iPb
Pbdla
dlaand
poszczególnych
obiektów
Tabela
5.5.Stosunki
wymiennego
do
poszczególnych
Exch
Exch
Exch conceptual
Copper
andCopper
lead
mitigation:
and lead mitigation:
and obiektów
ratios
ratios conceptual
approach. approac
(CaBC)
(%)
CuChel .
CuChel . PbChel .
PbChel .
2-n
2+2+
2-n
++
**
(aq)++nnHH
O
→
Me(OH)n
+
n
H
Me (aq)
Me
O
→
Me(OH)n
+
n
H
1.0
1.0
HA
HA
0.5
0.5
HA
HA
1.0
1.0
HA
HA
0.5
HA
0.5
HA
22
Control
–reported
0.40 andcalcium
4.09
CaO
CaO
reportedAs
above,
exchangeable
above, exchangeable
calcium
chelatedand
copper
chelated
as well
copper
as lead
as well
are those
as lead
forms,
are those form
Calcium-bearingAs
compounds
Calcium-bearing
compounds
Ca
Ca
CaExch
83.7
0.76
1.23
7.53
10.92
f soil
soil solutions
solutions pH
pH (Fig.
(Fig. 1)1)Quicklime
fluctuated (QL)
between
5.5 and
and 6.2,
6.2,
particularly
in Ca
fluctuated
between
particularly
in
Exch
Exch
Exch
(CaBC)5.5
(%)
(CaBC)
(%)
Pb
Pb
Cu
Cu
Chel
Chel
. . any
Chel
. . decisive
which strongly
which
interact
strongly
andinteract
hence play
and Chel
hence
the
play the
role.
decisive
Therefore
role.
Therefore
quantitative-based
any quantitative-bas
Phosphate
(PR)
1.33
2.73
15.30
30.91
with
phosphate rock
rock (PR).
(PR).
Thereforerock
can bebe expected,
expected,9.0
that significant
significant
ith phosphate
Therefore
itit can
that
Lacustrine
lime
(LL)
40.7
1.12
1.51
10.96
14.41
2+2+
Control
Control
-PbOH
- + +be
0.40
0.40information
4.09
4.09
Pb
maypotentially
potentiallyundergo
undergo
hydrolysisprocess
process
togenerate
generate
ions
snsofofPb
may
hydrolysis
ions
ratios
should
of
valuable
for CaBC
classifying
CaBC (Cainbasically)
terms of th
ratios toshould
be ofPbOH
valuable
information
for classifying
(Ca basically)
terms of in
their
Silicate
lime (SL)
41.183.7
1.28
1.85
12.78 10.92
15.95
2+2+
Quicklime
Quicklime
(QL)
(QL)
83.7
0.76
0.76
1.23
1.23
7.53
7.53
10.92
yadsorbed
adsorbedover
overPb
Pb ones
onesasaspointed
pointedout
outbybysome
someresearchers
researchers[Sauvé
[Sauvéetetal.,
al.,
effect in controlling
effect in Cu
controlling
and Pb in
Cuthe
andsoil.
Pb From
in the data
soil.reported
From data
in Table
reported
5, it
in appeared
Table 5, it
that
appeared
the
that
* Hydrolytic acidity
(HA).rock
Phosphate
Phosphate
rock
(PR)
(PR)
9.0
9.0ofofheavy
1.33
1.33
2.73
2.73
15.30
15.30
30.91
30.91
sexplains
explainsthe
thecomplex
complexrole
roleofofCa
Cainin
processes
leading
themitigation
mitigation
heavy
processes
leading
totothe
ofexchangeable
soil-born
i.e.,
before
CaBC incorporation,
ofamounts
soil-born
calcium
before
CaBC
incorporation,
were not inwere not
Lacustrine
Lacustrinelime
limeamounts
(LL)
(LL)
40.7
40.7
1.12
1.12exchangeable
1.51
1.51i.e.,calcium
10.96
10.96
14.41
14.41
andlead
leadamong
amongothers.
others.
rerand
This is decidedly shown by the significantly low ratios values, 0.40 and 4.09 for
dlead
leadmitigation:
mitigation:
Silicate
Silicate
lime
lime(SL)
(SL)
41.1
41.1
1.28
1.28
1.85
1.85
12.78
12.78
15.95
position to alleviate
position
the
to alleviate
negative
the
effect
negative
of Cu
effect
and Pb.
of Cu
and Pb. 15.95
CaExch
Ca Exch
Ca
Ca
Exch
and Exch
conceptualapproach.
approach. calculations have revealed, that the tarratios
conceptual
and
and
,ratios
respectively.
Tentative
CuChel
Pb
Cu
Pb
Chel
.
Chel
.
.
Chel
.
**
Hydrolytic
Hydrolyticacidity
acidity(HA)
(HA)
geted ratio for efficient mitigation of Cu and Pb effects under conditions of this study vary
above,exchangeable
exchangeablecalcium
calciumand
andchelated
chelatedcopper
copperasTable
aswell
wellas
lead
are
those
forms,
bove,
lead
are
forms,
5.asRatios
Table
ofthose
5.
exchangeable
Ratios
of exchangeable
Ca to chelated
Ca Cu
to chelated
and Pb for
Cuthe
andparticular
Pb for thetreatments
particular treatments
between 11 and 15. None of the tested CaBC treatments has revealed such evidence to-
glyinteract
interactand
andhence
hence
playcopper,
thedecisive
decisive
role.Therefore
Therefore
quantitative-based
ly
play
the
role.
quantitative-based
wards
particularly.
Thisany
means
that
the levels
of Ca incorporated
onposzczególnych
ofobiektów obiektów
Tabela
5.any
Stosunki
Tabela
Ca
5.
Stosunki
wymiennego
Ca wymiennego
do schelatowanych
do schelatowanych
Cu i Pb dla
Cuthe
i Pbbasis
dla poszczególnych
hydrolytic
acidity
(HA)
were
far
not sufficient.
Therefore
o potential *phytotoxicity
of Cu ions
dbebeofofvaluable
valuableinformation
information
forclassifying
classifying
CaBC
(Cabasically)
basically)
termsofoftheir
their
for
CaBC
(Ca
ininterms
1.0HA
HA*
1.0
0.5HA
HA
0.5
1.0HA
HA
1.0 HA
0.5 HA
0.5
CaO
CaO
may be fully expected, contrarily
to Pb,
where
onlycompounds
the control and QL treatment were found
Calcium-bearing
Calcium-bearing
compounds
trollingCu
Cuand
andPb
Pbininthe
thesoil.
soil.From
Fromdata
datareported
reportedininTable
Table5,5,ititappeared
appeared
thatthe
the
rolling
that
Ca Exch
Ca Exch
Ca Exch
(CaBC)
(CaBC)
(%)
(%)Ca Exch
inappropriate for plant growth.
PbChel .
PbChel .
CuChel .
CuChel .
soil-bornexchangeable
exchangeablecalcium
calciumi.e.,
i.e.,before
beforeCaBC
CaBCincorporation,
incorporation,were
werenot
notinin
soil-born
Control
Control
0.40
0.40
4.09
4.09
lleviate
thenegative
negativeeffect
effectofofCu
Cuand
andPb.
Pb.
eviate the
CONCLUSIONS
Quicklime4.(QL)
Quicklime
(QL)
83.7
83.7
0.76
0.76
1.23
1.23
7.53
7.53
10.92
10.92
Phosphate rock
Phosphate
(PR) rock (PR) 9.0
9.0
1.33
1.33
2.73
2.73
15.30
15.30
30.91
1.
The
incorporation
ofthe
CaBC
induced
both
changes
to a raise
in the content
iosofofexchangeable
exchangeable
Catoto
chelated
Cuand
andPb
Pbfor
for
the
particular
treatments
os
Ca
chelated
Cu
particular
treatments
Lacustrine
lime
Lacustrine
(LL) pH
lime
(LL) 40.7and led
40.7
1.12
1.12
1.51
1.51
10.96 of 10.96
14.41
labile Ca fractions accordingly
to Silicate
CaBC
type.
It should
mentioned
that pH 12.78
Silicate lime
(SL)
lime
(SL)
41.1 be decidedly
41.1
1.28
1.28
1.85
1.85
12.78
15.95
osunkiCa
Cawymiennego
wymiennegododoschelatowanych
schelatowanychCu
Cui iPb
Pbdla
dlaposzczególnych
poszczególnych
obiektów
sunki
obiektów
varied along with CaBC
rates,
i.e.,
0.5
HA
and
1.0
HA
and
reached
its
highest
value
*
*
Hydrolytic
acidity
Hydrolytic
acidity
**
1.0HA
HA
0.5HA
HA (HA)
1.0HA
HA (HA)
0.5HA
HA
1.0
0.5
1.0
0.5
(pH
CaOCaCl = 6.2) in the treatment receiving phosphate rock (PR) at 1.0 HA.
CaO
2
bearingcompounds
compounds
earing
CaExch
Ca
CaExch
Exch
2. The
Ca
water extractable
(Ca-H
O) was sufficient enough to control only active
Exch
(CaBC)
(%) level ofCa
(CaBC)
(%)
2
Pb
Pb
CuChel
Cu
Chel
Chel
. .
Chel
. .
Cu forms, hence to reduce their resorption to the soil phase, irrespective of CaBC rates.
--
0.40
0.40
4.09
4.09
me
(QL)
e (QL)
83.7
83.7
0.76
0.76
1.23
1.23
7.53
7.53
10.92
10.92
ate
rock(PR)
(PR)
e rock
9.0
9.0
1.33
1.33
2.73
2.73
15.30
15.30
30.91
30.91
lime(LL)
(LL)
enelime
40.7
40.7
1.12
1.12
1.51
1.51
10.96
10.96
14.41
14.41
lime
(SL)
me (SL)
41.1
41.1
1.28
1.28
1.85
1.85
12.78
12.78
15.95
15.95
73
30.91
14.4
15.95
simultaneously
simultaneously
enhances
metal
metal adsorption/retention.
adsorption/retention. The
The following
following reaction
reaction isis generally
generally
Jean
B. Diatta,enhances
Witold Grzebisz
suggested:
suggested:
2-n
(aq) ++ nnHH2O
→ Me(OH)n
Me(OH)n2-n
++nnHH++
Me
Me2+2+(aq)
2O →
The evaluation made on the basis of Ca exchangeable (Ca–Exch) outlined the specific
Most
Most ofof soil
soil solutions
solutions pH
(Fig.
(Fig. 1)1) fluctuated
between
between 5.5
5.5 and
and 6.2,
6.2, particularly
particularly inin
role of exchangeability processes
in controlling
quitepH
the
whole fluctuated
level of both
Cu bioavail-
treatments
treatments with
with phosphate
phosphate rock
rock (PR).
(PR). Therefore
Therefore itit can
can be
be expected,
expected, that
that significant
significant
able (Cu-Bio) and Cu chelated (Cu-Chel) for all CaBC treatments.
concentrations
concentrations ofof Pb
Pb2+2+ may
may potentially
potentially undergo
undergo hydrolysis
hydrolysis process
process toto generate
generate PbOH
PbOH++ ions
ions
3. Amounts of Pb bioavailable (Pb–Bio) explicitly show,
that both Ca water extractable
2+
2+
preferentially
preferentially adsorbed
adsorbed over
over Pb
Pb ones
ones asas pointed
pointed out
out by
by some
some researchers
researchers [Sauvé
[Sauvé etet al.,
al.,
(Ca-H2O) and exchangeable (Ca–Exch) efficiently controlled Pb chemistry in the inves-
1998b].
1998b].This
Thisexplains
explainsthe
thecomplex
complexrole
roleofofCa
Caininprocesses
processesleading
leadingtotothe
themitigation
mitigationofofheavy
heavy
tigated soil. This effect proceeded irrespective of the rates and the type of CaBC incorporated.
metals,
metals,copper
copperand
andlead
leadamong
amongothers.
others.
Copperand
andlead
leadmitigation:
mitigation:
4. Tentative calculations have Copper
revealed,
that
the
ratios
Ca
CaExch
Ca
CaExch
Exch
Exch
and
ratios
and
ratiosconceptual
conceptualapproach.
approach.
Cu
CuChel
Pb
PbChel
Chel
. . and
Chel
. . used for
evaluating the efficient mitigation of Cu and Pb effects varied between 11 and 15. None
As
Asreported
reportedabove,
above,exchangeable
exchangeablecalcium
calciumand
andchelated
chelatedcopper
copperasaswell
wellasaslead
leadare
arethose
thoseforms,
forms,
of the tested CaBC treatments has revealed such evidence towards copper, particular-
which
the
role.
which strongly
strongly interact
interact and
and hence
hence play
the decisive
role. Therefore
Therefore any
any quantitative-based
quantitative-based
ly. This means, that the levels
of Ca
incorporated
on
the play
basis
ofdecisive
hydrolytic
acidity
(HA)
were far not sufficient.
ratios
ratiosshould
shouldbe
beofofvaluable
valuableinformation
informationfor
forclassifying
classifyingCaBC
CaBC(Ca
(Cabasically)
basically)ininterms
termsofoftheir
their
5. The observed Ca versus Cu
andininPb
interactions
summarized
consequently
as
effect
controlling
Cu
Pb
the
ininTable
ititappeared
effect
controlling
Cuand
andmay
Pbininbe
thesoil.
soil.From
Fromdata
datareported
reported
Table5,5,
appearedthat
thatthe
the
follows: the relatively weak attraction of Ca by soil colloids must be compensated strictly
amounts
amounts ofof soil-born
soil-born exchangeable
exchangeable calcium
calcium i.e.,
i.e., before
before CaBC
CaBC incorporation,
incorporation, were
were not
not inin
by its high amounts in order to control efficiently high Cu concentrations.
position
positiontotoalleviate
alleviatethe
thenegative
negativeeffect
effectofofCu
Cuand
andPb.
Pb.
The realization of investigations was possible owing to the financing support
from means allocated to theTable
Science
for
years 2006–2009;
Research
Project
No.treatments
5.5.Ratios
ofofexchangeable
Ca
Cu
the
Table
Ratios
exchangeable
Catotochelated
chelated
Cuand
andPb
Pbfor
for
theparticular
particular
treatments
2 P06 L 02430: „Analysis of the
process
of differentiation
ofschelatowanych
a pine (Pinus sylvestris
L.)
Tabela
Cu
Tabela5.5.Stosunki
StosunkiCa
Cawymiennego
wymiennegodo
doschelatowanych
Cui iPb
Pbdla
dlaposzczególnych
poszczególnychobiektów
obiektów
population gene pool as a result of environmental stress induced by** industrial con-
taminants”.
Calcium-bearing
Calcium-bearingcompounds
compounds
(CaBC)
(CaBC)
REFERENCES
Control
Control
CaO
CaO
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1.0
1.0HA
HA
0.5
0.5HA
HA
0.5
0.5HA
HA
Ca
CaExch
Exch
Pb
PbChel
Chel
..
Ca
CaExch
Exch
Cu
CuChel
Chel
..
--
0.40
0.40
4.09
4.09
Quicklime
Quicklime(QL)
(QL)
83.7
83.7
0.76
0.76
1.23
1.23
7.53
7.53
10.92
10.92
Phosphate
Phosphaterock
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(PR)
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15.30
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30.91
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��������������������������������������
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