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Section 10. Chemistry
DOI: http://dx.doi.org/10.20534/ESR-17-5.6-84-87
Denaj Astrit, University of Vlora "Ismail Qemali" Msc. in Physics, Faculty of Technical Sciences E-mail: astrit.denaj@yahoo.com Dritan Spahiu, University of Tirana Prof. Dr. in Physics, Faculty of Natural Sciences E-mail: dspahiu12@yahoo.com Ramosagaj Miftar, University of Vlora "Ismail Qemali" PhD. in Mathematics, Faculty of Technical Sciences E-mail: miftar.ramosaco@gmail.com
REVALUATION OF SOILS IN THE AREA AROUND THE LANDFILL, IN THE TERRITORY OF FORMER SODA PVC PLANT VLORA, AFTER ITS REHABILITATION
Abstract: This paper refers to the revaluation of soils contaminated with mercury, in the area around landfill, built on the territory of the former Soda PVC plant in Vlora (Albania), after its rehabilitation. The territory of the former Plant of Soda-PVC is described as an "Hot Spot" area in handling the UNEP report, enabling the implementation of the rehabilitation processes, which were finalized with the creation of a landfill. From December 2015 to March 2017 after the rehabilitation of the area around the landfill, several measurements of mercury concentration in the soil have been conducted, to analyze the evolution of the pollution.
Keywords: Soda PVC plant, mercury, contamination, revaluation, CVAAS method.
Introduction taminated with mercury up to 1.0-1.5 meters depth. High enough
Five kilometers to the north of the city of Vlora and four kilo- mercury vapor levels were measured in the air [2]. meters to the Narta Lagoon is the territory of the former industrial Studies carried out showed a high level of pollution, hence this
complex of Soda PVC, which included the Klor-Alkaline Plant. area was declared as the "Hot Spot" area by UNEP. In 2007-2008, a
The PVC Soda Plant has started its normal production in Febru- rehabilitation project was conducted for this area. The project envis-ary 1967 with two products: chaotic soda and alkaline soy. Its main aged several stages ofwork that would have aimed thorough cleaning products were chaotic soda (produced by ammonia method), soda of the area [4].
(produced by limestone method) and PVC (produced by polym- To re-check the state of pollution in this area, after its rehabilita-
erization method of liquid monomers) [1]. tion, our study, was conducted. For this purpose, during the period
Mercury was used as a cathode during the electrolysis process for of December 2015-March 2017 after the rehabilitation, we analyzed, the production ofNaCl in electrolysis baths. During the operation of the the evolution of the pollution in this area. plant, as well during periodic cleaning of electrolysis baths and activated Materials and Methods
carbon filters, periodic pollution of the mercury zone was caused. Sampling Procedure
During the period of operation of the Plant (1976-1992) about Area included in this study is the surrounds of the former Soda
500m 3/hour ofliquid waste containing about 1.1mg/L mercury are PVC plant, located 5 km North of the city of Vlora. spilled into the sea without any cleaning process. The amount of The sampling has been done at 15 points within the study area.
spilled mercury directly into the environment from 1967 to 1983, is Each point are formed by one sample at 30cm depth. The geographi-estimated at about 65 tons. The territory of the former plant is con- cal coordinates of the points have been measured using GPS. Soil
samples were collected up to 150 cm deep from the surface, were air dreid, sieved through a 2.0 mm screen, and then grounded and sieved through a 0.063 mm screen. The homogenised samples eere stored in airtight pure plastic bags. [3]
Analytical Procedure of soil samples
A procedure based on UNEP/IAEA Reference Method for Pollution Studies was used [6, 12-13]. A 0.3-0.5 g sub samples were treated with a mixture of HNO3+HCl (9:1) in a hot plate at 7080 °C for 3 hours in closed PTFE vessels. After cooling, 1ml of 5% K2Cr2O7 was added and water up to 50ml. Depending on mercury content on the sample, an aliquot of clear solution was used for mercury determination by Cold Vapor Atomic Absorbtion Spectrom-
etry (CV-AAS) [5, 81-82]. All measurements were carried out using a Varian SPECTRAA 10 Plus instrument equipped with a homemade schema having a sensitivity about 0.2ppb Hg. All reagents used for mercury analyses are "low in Hg" quality (from Merck).
Reagents
All reagents were of analytical grade and met the requirements for determination of mercury. Tin (II) chloride was used as a 10% solution in HCl for reduction of Hg 2+ to Hg a The solution was purified in the gas wash bottle for 10min with airflow of 2.0 L/min.
Results and discutions
In Table 1 are presented concentrations of Hg (mg/kg DW) in soils taken at 30cm depth, around landfill.
Table 1. - Concentration of Hg (mg/kg DW), in soil samples around landfill, area of former Soda PVC plant in Vlora (Albania)
Points K1 K2 K3 K4 K5 K6 K7 K8
Hg (mg/kg DW) 100 3.495 1.194 13.092 46.384 4.471 1.327 87
Points K9 K10 K11 K12 K13 K14 K15
Hg (mg/kg DW) 3.1 1.024 12.98 43.54 4.76 1.323 1.289
Referring to Table 1, we note that the mercury concentration in the soils of this zone ranges from the minimum value of 1.024 mg/kg
DW to the maximum value of 100 mg/kg DW; with an average of about 21.67 mg/kg DW.
Concentration of Hg in soil at depths of 30cm, the area of Soda PVC plant
100
JE
£ o
£
Ol
£ o
I
Point Ki
—•— Hg(mg/kg)
■ UNEP Chimicals limit
10mg/kg
4 6 8 Points Ki for i =
10 1,2,.
Figure 1. The Hg concentrations Graph in soils, depth 30cm, the area around the landfill in the territory of the former Soda PVC plant in Vlora (Albania)
The above graph depicts, in the same system, the concentration of Hg in the area around the landifill (blue graph), the preliminary concentration limit of Hg in the soil, determined by UNEP Chemicals (0.3mg/kg) (red graph) and the concentration limit of Hg purified in this area (10mg/kg) (green color graph). Graphically it is noticed that about 30% of the values are above 10mg/kg, while all values (100%) are above the 0.3mg/kg level defined by UNEP Chemicals.
From the graph of the distribution of values of mercury concentration in this area we observe a discrete data distribution with
significant value fluctuations. The highest values are observed at points 1,5,8 and 12.
If we look at the distribution of mercury concentration values it is far from the parameters of a normal distribution.
If we look at the standard deviation (stDev=32.72mg/kg), it is far from normal distribution values because its values should be as small as possible.
This fact is also an indication that we have a disproportion of value distribution.
The table above presents a static estimate of the data obtained from the measurements. The confidence interval for the average is 3.5mg/kg to 39.7mg/kg, with 95% confidence. We note that 25% of the values are smaller than 1.3mg/kg, while 25% of these values are greater than 43.5mg/kg.
Confidence interval for the Median is (1.3mg/kg, 32.1mg/kg), and the confidence interval for the standard devia-
tion is (23.9mg/kg, 51.6mg/kg) both with 95% confidence. On the database we can also make a statistical estimate of the hypotheses, although the amount of data is not very large. The following table presents precisely this argument.
We have tested the baseline hypothesis Ho: avarage=0.3mg/kg (the pre-defined limit of UNEP Chemicals) with confidence level of 95%, or for a=0.5. Alternative hypothesis Average > 0.3mg/kg.
Probability Plot of Hg(mg/kg)(landifill)
Normal - 95% CI
0 50
Hg(mg/ kg)(landifill)
Mean 21.67
StDev 32.72
N 15
AD 2.100
P-Value <0.005
150
Figure 2. Probability Plot of Hg (mg/kg)
Summary for Hg(mg/kg)(landifil
0 20 40 60 80 100
95% Confidence Intervals
)
Anderson-Darling Normality Test
A-Squared 2.10
P-Value < 0.005
Mean 21.665
S tDev 32.719
Variance 1070.532
Skewness 1.69153
Kurtosis 1.76899
N 15
M inim um 1.024
1st Q uartile 1.323
M edian 4.471
3rd Q uartile 43.540
Maximum 100.000
95% Confidence Interval for Mean
3.546 39.784
95% Confidence Interval for Median
1.324 32.167
95% Confidence Interval for StDev 23.954 51.601
Figure 3. Statistical evaluation of the data obtained from measurements of mercury concentrations in soils around landifillit in the territory of the former Soda PVC plant in Vlora (Albania)
1-Sample t Test for the Mean of Hg(mg/kg)(la Summary Report
Is the mean less than 0.3?
0 0.05 0.1 > 0.5
Yes I
No
P = 0.9
The mean of Hg(mg/kg)(la S not significantly less than the target (p > 0.05).
Statistics
Sample size Mean
90% CI Standard deviation Target
15
21.665 (6.7857, 36.545) 32.719 0.3
Distribution of Data
Where are the data relative to the target?
Comments
-- Test: There S not enough evdence to conclude that the mean S less than 0.3 at the 0.05 level of significance. -- CI: Quantifies the uncertainty associated with estimating the mean from sample data. You can be 90% confident that the true mean s between 6.7857 and 36.545. -- Distribution of Data: Compare the location of the data to the target. Look for unusual data before interpreting the test results.
Figure 6. 1 — Sample t Test for the Mean of Hg (mg/kg)
From the table we notice that p-value = 0.98> 0.05 = a. This indicates that H0 falls, and with 95% confidence, we can state that the average concentration of mercury in this area is above the permissible norms level.
Conclusions
Mercury is one of the most known toxic metals, which can appear in nature in various inorganic and organic forms. Elementary mercury in gaseous state is the most dangerous of all kinds.
Mercury and its components are liberated from a multitude of natural and anthropic sources.
A typical example of an anthropic source in our country is the area of the former industrial complex PVC Soda in Vlora, Albania.
This area represents the area with the highest mercury pollution. This contamination has come as a result ofuncontrolled technological waste.
During 2007-2008, rehabilitation of this area was carried out.
Mercury contaminated soil (>10mg/kg DW) has been replaced
by clean ground (unpaved with mercury) and the entire surface will be covered with greenery and trees.
Area measurements, in the 30cm depth, include precisely these ground.
Although the area has been rehabilitated, the results of measurements carried out, results an average value of Hg concentration of 21.67mg/kg.
About 30% of the analyzed samples result in a concentration higher than 10mg/kg, indicating that the mercury concentration in the former PVC Soda plant area is still high compared to the rates allowed by UNEP.
Also the average is significantly higher in relation to the claimed value.
As a conclusion we can say that the concentration of mercury in the study area is higher in relation to accepted values, but also in relation to the claimed degree of purity, again we can say that the degree of concentration is higher.
References:
1. Lazo P., Bushati S., 2008 Tirana, "Environmental situation of Vlora Bay after mercury pollution", - Tirana - 2008, - Albania, ISBN 978-99956-10-12-8.
2. Kotorri P., Qomo A., "Covering of the soils eith mercury content is a choice or a solution of the problem of pollution in the former Soda PVC", Vlora.
3. Beqiraj A., Qullaj A., Kotorri P., "High-contaminated soil eith mercury in the bay of Vlora (Albania) and its possible remediation".
4. UNEP Chemicals: "Global Mercury Assement" IOMC, Geneva, Seitzerland, December - 2002.
5. Qullaj A., Qelo V. and Babi D., "Analytical investigation of heavy metals content in sediments of Albanian coast". Journal of Environmental and Ecology. - 2000.
6. Prusa J., "Distribution of mercury in saturated and unsaturated zones at PVC-Soda site in Vlora and its vicinity". Exploration Geophysics, Remote Sensing and Environment, XIII. - 2006.
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