CHLORINE ISOTOPES DETERMINATION FOR TRACKING
ORGANIC POLUTANTS REMEDIATION
V. R. DJORDJEVIĆ, S. R. VELIČKOVIĆ, J. M. CVETIĆANIN,
J. B. DJUSTEBEK, M. V. VELJKOVIĆ and O. M. NEŠKOVIĆ
Vinča Institute of Nuclear Sciences, Department of Physical Chemistry,
P. O. Box 522, Belgarde, Serbia, vesipka@vin.bg.ac.yu
ABSTRACT
A procedure for the determination of chlorine isotopic ratios by positive
thermal ionization mass spectrometry of the Cs2Cl+ ion has been
investigated. The chlorine isotopic composition in CsCl spectroscopically
pure has been measured with a precision of 0.034. The chlorine composition
in sea water samples has also been determined. The positive thermal
ionization mass spectrometric procedure based on measurement of Cs2Cl+
reported here is accurate, precise and simple to implement. The addition of
graphite in filament loading significantly enhances Cs2Cl+ emission from
CsCl, thus increasing the sensitivity. This increased sensitivity and the
demonstrated ratio measurement precision are significant improvements over
other mass spectrometric methods. The combined separation – mass
spectrometry procedure is simple to apply when compared to the other high
precision gas mass spectrometric method for chlorine measurement. The
method is ideally suited to studding the organic pollutants remediation.
Keywords: Chlorine isotopes, Remediation, Mass spectrometry
Introduction
Water pollution is a major problem in the global context. It has been suggested that it is
the leading worldwide cause of deaths and diseases, and that it accounts for the deaths of more
than 14,000 people daily [1]. Water pollution is a large set of negative effects upon water bodies
such as lakes, rivers, oceans, and groundwater caused by human activities. Although natural
phenomena such as volcanoes, algae blooms, storms, and earthquakes also cause major changes in
water quality and the ecological status of water, these are not deemed to be pollution. Water is
only called polluted when it is not able to be used for what one wants it to be used for. Water
pollution has many causes and characteristics. Pollutants in water include a wide spectrum of
chemicals, pathogens, and physical chemistry or sensory changes. Many of the chemical
substances are toxic.
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Remediation means providing a remedy, so environmental remediation deals with the
removal of pollution or contaminants from environmental media such as soil, groundwater,
sediment, or surface water for the general protection of human health and the environment.
Remediation technologies are many and varied but can be categorised into ex-situ and
in-situ methods. Ex-situ methods involve excavation of impacted soils and subsequent treatment at
the surface, In-situ methods seek to treat the contamination without removing the soils.
The more traditional remediation approach (used almost exclusively on contaminated
sites from the 1970s to the 1990s) consists primarily of soil excavation and disposal to landfill "dig
and dump" and groundwater "pump and treat".
The water emerging from some deep ground water may have fallen as rain many
thousands of years ago. Soil and rock layers naturally filter the ground water to a high degree of
clarity before it is pumped to the treatment plant. Such water may emerge as springs, artesian
springs, or may be extracted from boreholes or wells. Deep ground water is generally of very high
bacteriological quality but the water typically is rich in dissolved solids, especially carbonates and
sulfates of calcium and magnesium. Depending on the strata through which the water has flowed,
other ions may also be present including chloride, and bicarbonate.
Chlorinated organic compounds, along with other halogenated organics, are believed to
cause health risks such as cancer, endocrine system disruption, birth defects, immune system
disorders, and reduced fertility (many chlorinated organics mimic sex hormones such as estrogen
in many vertebrates, including humans). Examples of chlorinated organics include
trichloroethylene, ethylene dichloride, vinyl chloride, PCBs, chlorobenzene, and many chlorinated
solvents, insecticides, and herbicides. Maybe the best known Persistent Organic Pollutant (POP) is
Dichlorophenyl ethane (DDT). POPs properties, such as persistency, bioaccumulation, toxicity,
volatility, long range migration, bioaccessibility affords their presence in all trophic chains. Shortterm exposure does not induce acute effects, however long-term exposure are associated with
chronic illness and breast cancer risk. Human are exposed to DDT by eating certain contaminated
foods. DDT has been found in all foods (eggs, meat etc), including maternal milk.
Chlorine has the two naturally occurring isotopes, 35Cl and 37Cl, with relative
abundances of about 0.7553 and 0.2547, respectively [2,3]. The first measurement of the isotopic
abundance of chlorine has been reported in 1941, and it has bean much improved since.
Chlorine isotopic determination for tracking organic pollutants remediation via thermal
ionization mass spectrometry is proposed as a simple procedure. The information provided in such
way can prove chlorine stable isotope variation in contaminated nature samples to be significant,
judging the origin of pollutant and paths of its remediation.
Experimental
In this study, a positive thermal ionization mass spectrometric method for chlorine
measurement based on the ion CsrCl+ has been developed. The method is based on the ratio
37
Cl/35Cl ions, since it is known that the ratio is remarkably constant in nature. Isotopic
compositions are reported in per mil (‰) deviation from isotopic standard reference materials
using the conventional δ notation:
δ = [(Rsample/Rstandard)-1] x 1000
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where R = 37Cl/35Cl. The isotopic reference standard material was commercial NaCl working
standard relative to Arizona laboratory seawater standard (δ37Cl/35Cl = 0.00 ‰).
The evaporation (sample) filament was doped with water samples and Cs 2CO3 was used
as a reagent directly to develop Cs2Cl+ ions. Cs is monoisotopic, therefore ratio of 303/301 masses
of Cs237Cl+/Cs235Cl+ correspond to ratio of 37Cl /35Cl. The Cs2Cl+ ion has low ionization potential
suitable for thermal ionization analysis.
Impurities in the sample can cause interferences, poisoning the ionization process that
will result in changes of natural isotopic fractionation. The presence of nitrate and sulphate anions
was examined and no peaks were observed in the mass spectrum. Ba and Ca are the major
ingredients of sea waters and their presence did not significantly affect the ionization process.
Mass spectrometer used in this investigation was a 12-inch radius, 90° sector, magnetic
instrument of local design. A triple Rhenium filament thermal ionization source was used in
experimental setup, Figure 1.
Fig. 1. The structure of combined ionization source used in this work
The filaments were treated with 3 µl of the graphite slurry or to coat the whole filament.
The addition of graphite in filament loading significantly enhances Cs 2Cl+ emission from CsCl,
thus increasing the sensitivity.
The filaments were loaded into the source of the mass spectrometer and the isotopic
analysis is begun when the base pressure in the instrument was 10 -7 torr. The data were collected
by switching magnetically between the masses 301 and 303.
Conclusion
The aim of this work was the application of this high measurement precision to study the
possible variation in chlorine isotopic abundances in sea water samples. Chlorine isotopic
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determination for tracking organic pollutants remediation via thermal ionization mass
spectrometry is proposed as a simple procedure. Obtained results for various samples of sea water
were in correlation with the expected ones. The information provided in such way can prove
chlorine stable isotope variation in contaminated nature samples to be significant, judging the
origin of pollutant and paths of its remediation. With addition of some isotopic analysis such as
carbon isotopic content, this method could be very useful in environmental application of ground
water analysis.
References
[1] L. West, “World Water Day: A Billion People Worldwide Lack Safe Drinking Water”, 2nd
UN World Water Development Report, March 26, 2006.
[2] A. W. Boyd, F. Brown, M. Loundsbury, “Mass spectrometric study of natural and neutronirradiated chlorine” Can J Phys 3, 1995, p. 35-42
[3] R. Kaufmann, A. Long, H. Bentley, S. Davis, “Natural chlorine isotope variations” Nature
309, 1984, p. 338-340
[4] Y-K Xiao, C-G Zhang, “High precision isotopic measurement of chlorine by thermal
ionization mass spectrometry of the CsrCl+ ion” Int J Mass Spectrom Ion Process 116, 1992,
p. 183-192
[5] O. M. Nešković, M. V. Veljković, S. R. Veličković, A. J. Djerić, N. R. Miljević, D.D.
Globočanin, “Precise measurement of chlorine isotopes by thermal ionization mass
spectrometry” Nukleonika 47(Supplement 1), 2002, p. S85-S87
Acknowledgments
This work was financially supported by the Ministry of Science, Serbia, under Project
No. 142001.
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