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Detection of Lead in Soil with Excimer Laser Fragmentation Fluorescence Spectroscopy

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Abstract

The detection of atomic Pb emission from solid PbNO 3 and PbNO 3 mixed into a soil, by excimer laser fragmentation fluorescence spectroscopy (ELFFS) using a 193 nm ArF excimer laser, was discussed. The time-resolved emission from Pb(NO 3) 2 at 405.8 nm and the background signal at 415 nm were presented. The lead emission spectrum shows five distinctive emission lines of lead atoms at 357.2, 364.0, 368.3, 373.9 and 405.8 nm. It was shown that different types of soil interact differently with photons during laser-induced plasma formation, and in turn, the recorded signals have different characteristics.
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Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory
Title:
Detection of lead in soil with excimer laser fragmentation fluorescence spectroscopy (ELFFS)
Author:
Choi, J.H.
Damm, C.J.
O'Donovan, N.J.
Sawyer, R.F.
Koshland, C.P.
Lucas, D.
Publication Date:
03-01-2004
Publication Info:
Lawrence Berkeley National Laboratory
Permalink:
http://escholarship.org/uc/item/3qk515j0
Detection of Lead in Soil with Excimer Laser Fragmentation
Fluorescence Spectroscopy (ELFFS)
J. H. Choi1, C. J. Damm2, N. J. O’Donovan1, R. F. Sawyer1, C. P. Koshland2,
and D. Lucas3†
1Mechanical Engineering Department, University of California, Berkeley, CA 94720
2Science & Technology Department, Sierra Nevada College, NV 89451
3School of Public Health, University of California, Berkeley, CA 94720
4Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory
Berkeley, CA 94720
Date: 2/2/04
† Corresponding Author
D_Lucas@lbl.gov
PH: (510) 486-7002
FAX: (510) 486-7303
Index Headings: Photofragmentation; Fluorescence; Photochemistry; Plasma; Lead.
1
ABSTRACT
Excimer laser fragmentation fluorescence spectroscopy (ELFFS) is used to monitor lead
in soil sample and investigate laser-solid interactions. Pure lead nitrate salt and soil
doped with lead nitrate are photolyzed with 193 nm light from an ArF excimer at
fluences from 0.4 to 4 J/cm2. Lead emission is observed at 357.2, 364.0, 368.3, 373.9
and 405.8 nm. Time-resolved data show the decay time of the lead emission at 405.8
nm grows with increasing fluence, and a plasma is formed above fluences of 2 J/cm2,
where a strong continuum emission interferes with the analyte signal. Fluences below
this threshold allow us to achieve a detection limit of approximately 200 ppm in soil.
INTRODUCTION
Lead (Pb) poisoning from environmental and occupational exposure remains one of
the most common and preventable diseases. There are numerous serious and detrimental
health effects from inhalation or ingestion of lead, including poisoning or even death in
extreme circumstances1. Various in situ, real-time methods to measure heavy metals in
soil have been developed as a replacement for conventional wet-chemistry techniques
that require laborious and time consuming processes, such as preparation, dissolution,
chelation, and ion exchange2,3. Chemical analysis of soil sample with spectroscopic
methods is often achieved with much less sample preparation and time, but there are
often difficulties with calibration, matrix effects, and sensitivity4.
Here we apply excimer laser fragmentation fluorescence spectroscopy (ELFFS) to
pure lead nitrate salts and soils doped with lead nitrate. We and other groups have used
2
ELFFS to monitor various gaseous hydrocarbons, ammonia, combustion generated
metal species, and soot particles from diesel and other combustion exhausts5-9. The
main difference between this method and other direct solid ablation analysis techniques,
such as laser induced breakdown spectroscopy (LIBS) or laser ablation, is that the
surface is photolyzed at laser fluences below the threshold where plasma formation
occurs. The method benefits from an increased signal to noise (S/N) ratio compared
with LIBS since the lack of a plasma eliminates the strong continuum emission that
interferes with the analyte signals. The emission from the sample surface is recorded
during the laser pulse without gating, and the emission peak is normally proportional to
the concentration of the emitting species10.
EXPERIMENTAL
A schematic of the experimental apparatus is shown in Fig. 1. 193 nm photons with a
pulse duration of 20 ns are emitted from an ArF excimer laser (Lambda Physik LPX
210i). The laser beam is focused with a 3.8 cm diameter, 25 cm focal length UV grade
fused silica lens, and a 5 cm diameter mirror redirects the beam onto the solid surface of
the sample. Laser fluences range from 0.4 to 4 J/cm2. The fluence is varied by changing
the voltage of the laser and/or by introducing screens in the beam path. Fluorescence is
collected with a 3.8 cm biconvex lens (f# of 1.0) onto the entrance slit of a 0.3 m
CGA/McPherson scanning monochromator. The slit width of the monochromator is 0.4
mm, corresponding to a 1.1 nm bandpass. The light from the monochromator is detected
3
by a Pacific 508 photomultiplier tube, and the signal is digitized by a LeCroy LT 342
digital oscilloscope and transferred to a PC through a GPIB cable for further analysis.
Two different sample plates are used: the first plate is a flat anodized aluminum
plate; the second has two wells machined 2 mm into the surface to hold the solid
samples. The wells allow us to reproducibly fill the sample to the same level, and
contains the solids when ablating at high laser fluences. The sample plate is on a
mounting system in the laser interrogation region that includes a magnetic connection
and vertical translational stage to insure repeatability of a desired position and the
optimal height of the test plate, respectively. The sample plate can be also horizontally
translated with a motor or manually to introduce a fresh sample into the laser
interrogation region. The aluminum plate was found to have a low scattering
background, with no atomic or ionic Al peaks evident at the energy levels used here.
Lead nitrate (Pb(NO3)2), (Aldrich, 99+ %) is used pure and in a mixture with soil. Pure
lead nitrate is dissolved in water and applied to one of the sample wells. The solution is
dried with a heat lamp or gun. Soil is obtained from a residential garden in Berkeley,
CA. It is ground using a mortar and pestle and sifted using a coarse screen (1.5 x 1.5
mm2). A measured amount of a known concentration lead nitrate solution is added to
the soil to obtain a slurry. The slurry is applied to the other sample well, and then dried.
RESULTS AND DISCUSSION
The emission spectrum from Pb(NO3)2 and the background signal are shown in Fig.
2. The peak value of the emission during a time window of approximately 100 nsec
4
around the laser pulse is recorded for each single shot. The spectrum presented was
collected at a laser fluence of 0.4 J/cm2. The monochromator was scanned at a rate
corresponding to 5 shots/nm, and a rolling average of 5 shots was used to smooth the
data. The background signal is obtained directly from the anodized surface and contains
both optical and electrical noise. In the background spectrum the only peak observed is
the 2nd harmonic of the laser scattering at 386 nm. The lead emission spectrum also
shows 5 distinctive emission lines of lead atoms at 357.2, 364.0, 368.3, 373.9 and 405.8
nm. The 405.8 nm peak, a commonly used emission line for Pb analysis owing to its
strong emission, involves electronic transitions from 7s1 3P to 6p2 3P. Note that at this
fluence there is little broadband emission associated with plasma formation.
The time resolved emission from Pb(NO3)2 at 405.8 nm and the background signal
at 415 nm are presented in Fig. 3. The signals are shifted in time to a common scale, as
the different laser conditions affect the time where lasing actually occurs. The full width
at half maximum for these signals is shown in Table 1.
There are several points to consider in these results. During the first microsecond
(Fig. 3a) at the lowest fluence, 0.53 J/cm2, the background signal is relatively low (0.05
V), and lasts about as long as the laser pulse. Similar signals are observed at other
wavelengths not associated with known transitions. The background is mainly due to
193 nm laser light leaking through the monochromator (its rejection ratio is
approximately 4000:1). The signal from lead at these conditions peaks near 0.3 V, and
lasts longer. At higher fluences, the peak of the lead emission does not increase, but the
emission tail grows. The background signal increases dramatically, reaching the same
5
peak value as the lead emission at the highest fluence (3.29 J/cm2). Others and we have
previously observed that the peak signal is not a strong function of laser fluence,
presumably since the process has a step that can be saturated9,11.
Even more dramatic changes are observed at longer times (Fig. 3b). At fluences
below 2 J/cm2 the signal is a single peak with a near exponential decay. At higher
fluences, a second peak emerges at longer times, peaking in the 3 – 5 µsec range. At the
lower fluences, atoms or molecules are released from the matrix through direct
photochemical bond-breaking rather than through photothermal processes, since the 193
nm photons are energetic enough to break the most of the molecular bonds. As the
fluence increases, more species are liberated and electronically excited, and a larger
fraction of species are ionized. Above the threshold, the extent of fragmentation and
ionization increases, and the liberated and ionized species absorb the incoming light,
forming a plasma. Plasma formation has been widely studied using laser ablation or
laser breakdown techniques12-14.
Once a plasma plume is formed by accumulation of photon energy at high fluence,
incoming light is absorbed and emission is trapped within a plasma so that the plume
grows, reaching an elevated temperature (5,000 ~ 15,000 K) and triggering broadband
emission from air, electrons, atomic or ionic species, and ablated fragments. After the
plume of the fully grown plasma cools, the analyte emission forms another peak as
shown in Fig. 3(b), which is characteristic of Pb emission in LIBS. The lifetime of the
signal in this case extends to 10 µs. Note that the magnitude of the background peak
linearly increases with the fluence and reaches the same as that from Pb(NO3)2 while
6
lead signal intensities are almost unchanged. Therefore, it can be expected that if the
background is subtracted from the lead emission, the net signal will decrease with
increasing fluence. By using lower fluences and avoiding plasma formation, we
significantly achieve better signal to noise ratios. The temperature increase in the gas
phase and changes in collisional quenching are not significant compared to cases with a
plasma. Finally, photon energy transfer to the target material is more efficient and there
is no need for signal gating and time-resolved data analysis.
The same measurement procedure is applied to soil samples with lead nitrate salt
added, where the sample surface is significantly rougher. The spectrum of lead in soil is
shown in Fig. 4. The spectrum of pure soil does not contain any obvious distinct peaks
except ones from laser scattering (not shown here). However, the noise level from
background soil is often considerably higher than that from anodized Al plate, so the
laser energy is reduced to optimize S/N, and the five emission lines of lead are still
observed. As with the pure lead nitrate, the lead signal increases with laser fluence, but
the background increases at a faster rate.
Direct application of spectroscopic techniques for metal detection in soils without
any sample preparation has limits since soil is inherently inhomogeneous in nature. It is
not expected that the target species is contained uniformly in soil, so variations could
easily occur in different locations from a sample. The surface roughness and material
properties of the soil is also not uniform. When focused on a single point, the laser
eventually craters the soil surface, which affects both the laser-soil interaction and the
detection sensitivity. We minimized the crater effect by introducing a fresh sample into
7
the probe volume approximately at the translational rate of 0.11 mm/sec. In addition,
Eppler et al.15, Wisbrun et al.16, Bulatov et al.4, and Capitelli et al.3 showed that various
types of soil interact differently with photons during laser induced plasma formation,
and in turn, the recorded signals have different characteristics.
Fig. 5 shows the relationship between the peak emission amplitude with the lead
concentrations in soil. The values shown are the difference in maximum lead emission
and background peaks at 405.8 and 345 nm, respectively. The resulting signal is
roughly linear with concentration, and indicates that the method could be used to
quickly screen samples without significant preparation. The detection limit is lower than
the regulatory standards imposed by US EPA for the presence of lead in soil (400
ppm17). The sensitivity of the system is dominated by optics and sample conditions,
such as alignment, laser fluence, sample preparation and the soil matrix. While
additional work is needed to ascertain the robustness of the analytical method, the lack
of interferences from plasma-type emission is certainly promising.
CONCLUSIONS
Excimer laser fragmentation fluorescence spectroscopy has been successfully
applied to the detection of lead in soil samples using a 193 nm ArF excimer laser. The
detection method differs from other solid ablation processes in that lower laser fluences
are used, and there is no plasma generation and subsequent broadband emission. A
fluence threshold of approximately 2 J/cm2 is found for plasma formation. The
8
detection limit for Pb in soil samples is about 200 ppm, achieved with minimal sample
preparation and an analysis time on the order of a minute.
ACKNOWLEDGEMENT
This work was supported by the Environmental Health Sciences Superfund Basic
Research Program (Grant Number P42ESO47050-01) from the National Institute of
Environmental Health Sciences, NIH, with funding provided by the EPA. Its contents
are solely the responsibility of the authors and do not necessarily represent the official
views of NIEHS, NIH, or EPA.
REFERENCES
1. USEPA, 747-R-97-006 (1998)
2. F. Hilbk-Kortenbruck, N. Reinhard, P. Wintjens, F. Heinz and C. Becker,
Spectrochimica Acta Part B 56, 933 (2001).
3. F. Capitelli, F. Colao, M. R. Provenzano, R. Fantoni, G. Brunetti and N. Senesi,
Geoderma 106, 45 (2002).
4. V. Bulatov, R. Krasniker and I. Schechter, Analytical Chemistry 70, 5302
(1998).
5. C. J. Damm, D. Lucas, R. F. Sawyer and C. P. Koshland, Chemosphere 42, 655
(2001).
6. S. G. Buckely, D. Lucas, C. P. Koshland and R. F. Sawyer, Combustion Science
and Technology 118, 169 (1996).
9
7. C. S. McEnally, D. Lucas, C. P. Koshland and R. F. Sawyer, Applied Optics 33,
3977 (1994).
8. B. L. Chadwick, G. Domazetis and R. J. S. Morrison, Analytical Chemistry 67,
710 (1995).
9. R. C. Sausa, A. J. Alfano and A. W. Miziolek, Applied Optics 26, 3588 (1987).
10. N. J. O'Donovan, M.S., Mechanical Engineering Department, University of
California at Berkeley (2002)
11. S. G. Buckley, C. J. Damm, W. M. Vitovec, L. A. Sgro, R. F. Sawyer, C. P.
Koshland and D. Lucas, Applied Optics 37, 8382 (1998).
12. W. F. Ho, C. W. Ng and N. H. Cheung, Applied Spectroscopy 51, 87 (1997).
13. D. S. Tomson and D. M. Murphy, Applied Optics 32, 6818 (1993).
14. J. E. Carranza and D. W. Hahn, Analytical Chemistry 74, 5450 (2002).
15. A. Eppler, D. A. Cremers, D. D. Hickmott, M. J. Ferris and A. C. Koskelo,
Applied Spectroscopy 60, 1175 (1996).
16. R. Wisbrun, I. Schechter, R. Nlessner, H. Schroder and K. L. Kompa, Analytical
Chemistry 66, 2964 (1994).
17. USEPA, 40 CFR Part 745 (2001)
10
Table 1: Full width at half maximum of the signals produced by photofragmentation
fluorescence (* FWHM of the first peak).
Fluence 0.53 J/cm22.05 J/cm23.29 J/cm2
Lead 42 ns 109 ns 254 ns*
Background 16 ns 22 ns 81 ns
11
Figure 1: Schematic of the experimental apparatus
Focusing Lens
193 nm ArF
Monochromator
Collection Lens
Mirror
Pb(NO3)2
Pb(NO3)2
in Soil
Test Plate
Focusing Lens
193 nm ArF193 nm ArF
Monochromator
Collection Lens
Mirror
Pb(NO3)2
Pb(NO3)2
in Soil
Test Plate
12
Figure 2: Emission spectra of background from the anodized Al surface and lead from
Pb(NO3)2 at the laser fluence of 0.4 J/cm2.
0.00
0.05
0.10
0.15
0.20
0.25
330 340 350 360 370 380 390 400 410 420 430
Wavelength (nm)
Emission Amplitude (V)
Lead Signal
Background
386, 2
nd
harmonic
405.8
364.0
357.2
368.3
373.9
13
Figure 3: Time resolved emission from Pb(NO3)2 (405.8 nm) and background (415 nm)
at various fluence conditions. (a) Emission during the first µsecond.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 0.10.20.30.40.50.60.70.80.9 1
Time (µs)
Emission Amplitude (V)
Lead: 3.29 J/cm
2
Lead: 2.05 J/cm
2
Lead: 0.53 J/cm
2
Background: 0.53 J/cm
2
Background: 3.29 J/cm
2
Background: 2.05 J/cm
2
14
(b) Lead emission at longer time scales. Note that plasma formation threshold appears
approximately 2 J/cm2.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0123456789
Time (us)
Emission Amplitude (V)
10
3.29 J/cm
2
2.05 J/cm
2
0.53 J/cm
2
15
Figure 4: Emission spectrum of Pb in soil for the laser energy of 30 mJ.
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
330 340 350 360 370 380 390 400 410 420 430
Wavelength (nm)
Emission Amplitude (V)
16
Figure 5: Correlation curve for lead emission and concentration of lead in soil. The
presented values are maximum lead emission peaks subtracted by background scattering
measured at 415 and 345 nm, respectively.
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 100 200 300 400 500 600 700 800 900 1000 1100
Concentration (ppm)
Emission Amplitude (V)
17
... susceptible to elevated Pb concentrations in dust and soil because of their successive hand-tomouth and pica conduct [2]. The negative wellbeing impacts related with the component incorporate restrained mental health and hematological impacts, for example, weakness [3], because of Pb accumulation in the kidney, liver, teeth and bones [4,5]. ...
... A study by Zartarian et al. [13] expressed that paints, drinking water, soil, and residue that contain Pb are the great wellsprings of Pb presentation in the wake of eliminating of leaded fuel other than Pb smelters and mechanical procedures [13]. An expanding number of studies detailed appropriate indications of Pb-initiated neurological or potentially conduct impacts in youngsters starting at around 10 ug/dL or even lower, with populace impacts getting to be more clear and progressively positive in the scope of 30-40 ug/dL [2]. It is important to refer to that a few scientists have an uncommon worry about the impacts of Pb on neurobehavioral execution, heme union, and fetal advancement. ...
... Since appropriate input data is as of now from accessible in literature, this research does not have to include any child participants. Indeed, incorporated evaluation incorporates two stages: [1] recreate the Pb concentration distribution in different condition media model, [2] estimate Pb consumption and the BLLs. Related objectives were to evaluate the coupled model estimates using real-world blood lead data, to quantify relative contributions by the various media, and to identify key model inputs. ...
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... The injury depending on age, socioeconomic status, the population of a given community and race, [1]. Long-term exposure to the lead may contribute to elevated blood Pb levels, especially in young children, who are more susceptible to elevated Pb concentrations in dust and soil because of their repetition of hand-to-mouth and pica behavior, [2]. The negative health effects associated with the element include the development of inhibited brain and hematological effects, like anemia [3], due to Pb that accumulating in the kidney, liver, teeth and bones, [4,5]. ...
... An increasing number of studies report suitable signs of lead-induced neurological and/or behavioral effects in children starting at about 10 ug/dL or less, in the range of 30-40 ug/dL the population effects being clearer, [2]. The claims by some researchers with special interests that neurobehavioral performance is effected by lead, and the effects are longlasting and may not have a threshold value especially heme synthesis, and fetal development, [4]. ...
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For decades, human health was threaten (especially that of children) by what considered as a potential sources of lead exposure which are: lead-contaminated water, soil, and air. The proposed of the research involve developing an integrated exposure, uptake, and biokinetic (IEUBK) model as a human health risk model to predict the blood lead levels BLL in children. The data set of this project for human health risk posed by Pb contamination in air, water and soil were obtained from previous study achieved in 2014 which carried out on 108 school children (School children in rural areas (n=76 child) and School children in urban areas (n=32child) matched for age. The environmental samples demonstrated that the concentration of lead for air and soil exceeded the international acceptable threshold values. However, the concentration of lead in water was below the threshold value. The BLL value from currently result of IEUBK model was above the agency’s threshold of concern, 10 μg/dL which was documented as children’s BLL lowest level of concern. This predicted values result of BLL was in agreement with actual value of BLL in blood samples of school children for the chosen study. Also, the results of this research confirmed that the high BLL could be attributed to the high lead level in both air and soil of contaminate environment
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... The injury depending on age, socioeconomic status, the population of a given community and race, [1]. Long-term exposure to the lead may contribute to elevated blood Pb levels, especially in young children, who are more susceptible to elevated Pb concentrations in dust and soil because of their repetition of hand-to-mouth and pica behavior, [2]. The negative health effects associated with the element include the development of inhibited brain and hematological effects, like anemia [3], due to Pb that accumulating in the kidney, liver, teeth and bones, [4,5]. ...
... An increasing number of studies report suitable signs of lead-induced neurological and/or behavioral effects in children starting at about 10 ug/dL or less, in the range of 30-40 ug/dL the population effects being clearer, [2]. The claims by some researchers with special interests that neurobehavioral performance is effected by lead, and the effects are longlasting and may not have a threshold value especially heme synthesis, and fetal development, [4]. ...
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... An increasing number of studies report suitable signs of lead-induced neurological and/or behavioral effects in children starting at about 10 ug/dL or less, in the range of 30-40 ug/dL the population effects being clearer, [2]. The claims by some researchers with special interests that neurobehavioral performance is effected by lead, and the effects are longlasting and may not have a threshold value especially heme synthesis, and fetal development, [4]. ...
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... The injury depending on age, socioeconomic status, the population of a given community and race, [1]. Long-term exposure to the lead may contribute to elevated blood Pb levels, especially in young children, who are more susceptible to elevated Pb concentrations in dust and soil because of their repetition of hand-to-mouth and pica behavior, [2]. The negative health effects associated with the element include the development of inhibited brain and hematological effects, like anemia [3], due to Pb that accumulating in the kidney, liver, teeth and bones, [4,5]. ...
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Full-text available
  • Mar 2015
Exposure to Lead (Pb) from soil and dust in urban areas continues to threaten human health; especially that of children, who are more likely to absorb a higher fraction of ingested Pb from contaminated soil. However, to date methods available to remotely evaluate the distribution and severity of soil Pb contamination across large urban areas in a timely manner are lacking and new techniques are required to address this important issue. Therefore, this study evaluated both spectroscopic and geostatistical approaches for prediction of soil Pb concentrations leading to models of spatial distributions in the contaminated area. This study thus supports ongoing investigation and monitoring of Pb contamination by providing digital mapping options for studying the environmental and health impact of Pb contamination which can substantially reduce the time and costs associated with traditional soil contaminant analysis. NIR spectroscopy in conjunction with multivariate analysis demonstrated that spectral reflectance could potentially be used to predict soil Pb concentrations in long-term atmospheric smelter emission Pb contaminated soils. Partial least square regression (PLSR) was utilised to correlate NIR with log transformed Pb concentrations, which indicated a strong linear relationship between soil Pb and spectral reflectance between 500 - 612 nm. The relative accuracies of the developed predictive models were assessed via inter-comparison of coefficients of determination (R2) and the root mean square error (RMSE) based on the cross validation method (leaving one out). The final model chosen exhibited the greatest accuracy as indicated via comparison between predicted and traditional soil measurements. While reflectance spectroscopy compared favourably to wet chemical techniques and thus could be used to rapidly predict Pb especially in a uniform soil over a large area, XRF spectroscopy was also highly correlated with ICP-MS determinations of Pb concentration obtained from traditionally wet chemical acidic digestion of soils. Thus XRF could provide less expensive, on-site measurements of soil Pb with the advantage of allowing chemical assessment of contamination in close to real time. This research also confirmed that geostatistical methods (kriging and cokrging) using a GIS had the ability to rapidly estimate soil Pb distributions which can be used in environmental health risk assessment. However, to be truly effective, both spectral and spatial analysis required knowledge of some auxiliary soil variables (e.g. total carbon, iron content and other heavy metals). For example, while ordinary kriging resulted in unreliable predictions of soil Pb, the correlation between Pb and Zn was a useful mechanism for iii obtaining better predictions of Pb using co-kriging. Similarly, soil carbon as a spectrally active soil component, improved the predicted of Pb using VNIR. For assessing environmental risk and health impact of Pb contamination in Port Pirie, probability kriging (PK) was used to determine the probability of exceeding a specific soil Pb bioavailability threshold of 19% where an in vitro method was also used to determine the bioavailable (bioaccessible) fractions of soil Pb which could be potentially absorbed by humans under simulated gastrointestinal conditions. When mapped as a probability surface the PK technique allowed areas of higher risk to be instantly identified, and since such areas were well correlated with the historic areas of high Pb contamination and previously reported elevated BPb in children from Port Pirie, this technique was a useful practical tool for identifying populations at risk from Pb exposure.
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... Lead (Pb) is a toxic heavy metal and common environmental contaminant which can pose significant threats to public health at high concentration levels (Kachenko and Singh, 2006;WHO, 2010). Elevated Pb concentrations in dust and soil may contribute to elevated blood Pb (BPb) levels, especially in children due to their frequent hand-to-mouth and pica behaviour (Choi et al., 2005). The negative health effects associated with Pb include inhibited brain development and haematological effects, such as anaemia (Bray et al., 2009), due to accumulation of Pb in the kidney, liver, teeth and bones (WHO, 2010). ...
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... The method can simultaneously detect multiple airborne elements and compounds down to very low levels (in the parts per billion range), including chlorinated hydrocarbons, barium, chromium, manganese, nickel, lead, and tellurium. The assay detects chemicals in real time and also in situ (Choi et al. 2005). ...
The NIEHS Superfund Research Program: Twenty-Five Years of Translational Research for Public Health
Article
Full-text available
  • May 2015
  • ENVIRON HEALTH PERSP
The Superfund Research Program (SRP) is an academically based, multidisciplinary, translational research program that for 25 years has sought scientific solutions to health and environmental problems associated with hazardous waste sites. SRP is coordinated by the National Institute of Environmental Health Sciences (NIEHS). It supports multi-project grants, undergraduate and post-doctoral training programs, individual research grants, Small Business Innovation Research (SBIR) and Technology Transfer Research (STTR) grants. SRP has had many successes: discovery of arsenic's toxicity to the developing human central nervous system; documentation of benzene toxicity to hematologic progenitor cells in human bone marrow; development of novel analytic techniques such as the Luciferase Expression assay and laser fragmentation fluorescence spectroscopy; demonstration that PCBs can cause developmental neurotoxicity at low levels and alter the genomic characteristics of sentinel animals; elucidation of the neurodevelopmental toxicity of organophosphate insecticides; documentation of links between antimicrobial agents and alterations in hormone response; discovery of biological mechanisms through which environmental chemicals may contribute to obesity, atherosclerosis, diabetes and cancer; tracking the health and environmental effects of the attacks on the World Trade Center and Hurricane Katrina; and development of novel biological and engineering techniques to facilitate more efficient and lower-cost remediation of hazardous waste sites. SRP must continue to address the legacy of hazardous waste in the United States, respond to new issues caused by rapid advances in technology, and train the next generation of leaders in environmental health science, while recognizing that most of the world's worst toxic hotspots are now located in low- and middle-income countries.
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... Recent studies show that many urban children have high blood Pb levels due to exposure of soil-borne Pb (figure 1). Small children are more susceptible to increased levels of Pb intake due to frequent hand-to-mouth behaviour (Mielke 1999) after playing in an environment with hazards such as elevated levels of Pb in house dust or yard soils (Bellinger 2004, Choi et al. 2005. ...
Estimation of heavy-metal contamination in soil using reflectance spectroscopy and partial least-squares regression
Article
Full-text available
  • May 2010
Lead (Pb) poisoning from anthropogenic sources continues to threaten the health of urban children. Mapping Pb distribution on a large scale is imperative to identify hotspots and reduce Pb poisoning. To assess the feasibility of using reflectance spectroscopy to map soil Pb and other heavy metal abundance, the relationship between surface soil metal concentrations and hyperspectral reflectance measurements was examined via partial least-squares regression (PLSR) modelling. Soil samples were taken from four study sites. Metal concentrations were determined by inductively coupled plasma-atomic-emission spectrometry (ICP-AES) analysis, and reflectance was measured with an ASD (Analytical Spectral Devices) field spectrometer covering the spectral region of 350-2500 nm. Pb displayed an exponential decrease as a function of distance from the roadway, demonstrating the depositional patterns from leaded gas combustion which remain on the landscape 20 years after the phase-out of leaded gasoline. Calibration samples were used to derive the PLSR algorithm, and validation samples assessed the model's predictive ability. The correlation coefficients between the lab-determined abundance and the abundance predicted from PLSR calibration for all metals except copper were at or above 0.970, with the correlation coefficient for Pb the highest of all metals (0.992). Manganese, zinc and Pb had significant coefficients of determination (0.808, 0.760 and 0.746, respectively) for the validation samples. These results suggest that Pb and other heavy metal concentrations can be retrieved from spectral reflectance at high accuracy. Reflectance spectroscopy thus has potential to map the spatial distribution of Pb abundance with the aim of improving children's health in an urban environment.
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Elemental composition of Arctic soils and aerosols in Ny-Ålesund measured using laser-induced breakdown spectroscopy
Article
  • Jun 2017
  • SPECTROCHIM ACTA B
Two laser-induced breakdown spectroscopy (LIBS) systems (soil LIBS and aerosol LIBS) were used to determine the elemental composition of soils and ambient aerosols less than 2.5 μm in Ny-Ålesund, Svalbard (the world's most northerly human settlement). For soil LIBS measurements, matrix effects such as moisture content, soil grain size, and surrounding gas on the LIBS response were minimized. When Ar gas was supplied onto the soil sample surfaces, a significant enhancement in LIBS emission lines was observed. Arctic soil samples were collected at 10 locations, and various elements (Al, Ba, C, Ca, Cu, Fe, H, K, Mg, Mn, N, Na, O, Pb, and Si) were detected in soils. The elemental distribution in arctic soils was clearly distinguishable from those in urban and abandoned mining soils in Korea. Moreover, the concentrations of most of anthropogenic metals were fairly low, and localized sources in extremely close proximity affected the elevated level of Cu in the soil samples derived from Ny-Ålesund. The number of elements detected in aerosols (C, Ca, H, K, Mg, Na, and O) was lower than those determined in soils. The elements in aerosols can mainly originate from minerals and sea salts. The elemental distribution in aerosols was also clearly distinguishable from that in soils, suggesting that the resuspension of local soil particles by wind erosion into aerosols was minimal. The daily variation of particle number concentration (RSD = 71%) and the elements in aerosols (RSD = 25%) varied substantially, possibly due to fluctuating air masses and meteorological conditions.
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Matrix Effects in the Detection of Pb and Ba in Soils Using Laser-Induced Breakdown Spectroscopy
Article
Full-text available
  • Sep 1996
With the use of laser-induced breakdown spectroscopy (LIBS), the effects of chemical speciation and matrix composition on Pb and Ba measurements have been investigated by using sand and soil matrices. A cylindrical lens was used to focus the laser pulses on the samples because it yielded higher measurement precision than a spherical lens for the experimental conditions used here. The detection limits for Pb and Ba spiked in a sand matrix were 17 and 76 ppm (w/w), respectively. In spiked soil, the detection limits were 57 and 42 ppm (w/w) for Pb and Ba, respectively. Measurement precision for five replicate measurements was typically 10{percent} RSD or less. Two factors were found to influence emissions from Pb and Ba present in sand and soil matrices as crystalline compounds: (1) compound speciation, where Ba emission intensities varied in the order carbonate{gt}oxide{gt}sulfate{gt}chloride{gt}nitrate, and where Pb emission intensities varied in the order oxide{gt}carbonate{gt}chloride{gt}sulfate{gt}nitrate; and (2) the composition of the bulk sample matrix. Emissions from Ba(II) correlated inversely with the plasma electron density, which in turn was dependent upon the percent sand in a sand/soil mixture. The analytical results obtained here show that a field-screening instrument based on LIBS would be useful for the initial screening of soils contaminated with Pb and Ba. {copyright} {ital 1996 Society for Applied Spectroscopy.}
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Sensitive in situ detection of chlorinated hydrocarbons in gas mixtures
Article
Full-text available
  • Jun 1994
We detect chlorinated hydrocarbons (CHC’s) in gas mixtures by dissociating the CHC’s with a 193-nm laser and measuring the subsequent concentration of the CCl fragmentation by means of laser-induced fluorescence. Sub-ppm detection, where ppm indicates parts in 10⁶, is achieved for C2H5Cl with a 10-mm³ measurement volume and integration over 50 laser shots. Every other CHC tested is also detectable, with the same or better detection limits. The CCl forms promptly during the fragmentation laser pulse through unimolecular dissociation of the parent CHC’s. The technique should be a useful diagnostic for CHC incineration systems.
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Ammonia detection and monitoring with photofragmentation fluorescence
Article
  • Jan 1998
Excimer laser fragmentation-fluorescence spectroscopy is an effective detection strategy for NH3 in combustion exhausts at atmospheric pressure and high temperatures. Two-photon photofragmentation of NH3 with 193-nm light yields emission from the NH(A-X) band at 336 nm. There are no major interferences in this spectral region, and the sensitivity is at the parts per billion (ppb) level. Quenching of the NH(A) state radical by the major combustion products is measured and does not limit the applicability of the detection method. Detection limits in practical situations are of the order of 100 ppb for a 100-shot (1-s) average. This technique could prove useful in monitoring ammonia emissions from catalytic and noncatalytic NOx reduction processes involving ammonia injection.
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Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength
Article
  • Jan 1997
The plasma plume emissions produced by pulsed ( ~ 10 ns) laser ablation of liquid jets were monitored for spectrochemical analysis. Laser wavelengths at 532 and 193 nm were used, and sodium was the test analyte. As expected, the 532-nm laser pulse produced very intense plasma continuum emissions that masked the sodium signal for the first hundred nanoseconds, especially near the bright core of the vapor plume. Neither time-gating nor spatial masking could significantly improve the single-shot signal-to-noise ratio, since the transient nature of the emissions placed stringent demands on timing precision while the small size of the plume required accurate mask positioning-both antithetical to the inherent instability of jet ablation. In sharp contrast, the 193-nm laser pulse produced relatively dim plasma flash but intense sodium emissions, rendering it ideal for analytical applications.
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Metal Emissions Monitoring Using Excimer Laser Fragmentation-Fluorescence Spectroscopy
Article
Photofragmentation of molecules using an excimer laser with subsequent detection of fluorescence from metal atoms formed in excited states is a viable detection strategy for many metal species. Excimer laser fragmentation-fluorescence spectroscopy (ELFFS) can provide continuous, real-lime monitoring information for metals which evolve from a variety of high-temperature processes, including combustion, Here we apply ELFFS to lead, manganese, nickel and chromium species in the postflame gases of a laboratory burner. Using a 193-nm argon fluoride laser we obtain quantitative relationships between signal strength and concentration in hot combustion products for metals injected into a flame; representative spectra are shown. The effects of quenching environment and laser power on the signal are discussed. The ELFFS technique is sensitive, providing ppb detection limits for these metals in a one-second measurement time.
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Study of Matrix Effects in Laser Plasma Spectroscopy by Combined Multifiber Spatial and Temporal Resolutions
Article
  • Nov 1998
Understanding the matrix effects in laser plasma spectroscopy is of considerable importance, since these effects actually limit the performance of the method. Thus, a new multifiber imaging spectrometer, coupled with an ICCD detection system, was developed and applied to this task. A special sample holder which enables simultaneous observation of single-shot plasmas through eight optical fibers was constructed. The fibers collect the emission at several locations from single-shot plasma, perpendicularly to its expansion axis. In this way, high-resolution spectra of the analyte and the matrix are simultaneously obtained with spatial and temporal resolutions. Results on investigation of matrix effects in analysis of Pb in natural soils, using this setup, are reported. The matrix effect due to the sand content in the examined samples is presented, and explanations are suggested. It was found that the optimum location in the plasma for spectral analysis depends on analyte concentration in such a way that, at higher concentration ranges, the spectra should be measured closer to the surface. A clear global optimum was observed for analyte signal as a function of location and time, indicating the best experimental conditions. The matrix dependence of that optimum is addressed. The spatial distribution of the internal plasma temperature and the related matrix effects are also discussed.
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Multiwavelength Monitoring of Photofragment Fluorescence after 193 nm Photolysis of NaCl and NaOH: Application to Measuring the Sodium Species Released from Coal at High Temperatures
Article
  • Feb 1995
Excimer laser photodissociation of gas-phase NaCl and NaOH, and monitoring of the subsequent Na photofragment fluorescence, are used to determine the concentration of the species in coal-derived gaseous environments. Detection limits lower than 1 ppb of NaCl have been achieved under atmospheric conditions using 193 nm photodissociation. It is shown that monitoring two Na emission wavelengths (at 819 and 589 nm) allows speciation between NaOH and NaCl in the gas phase. In particular, emission from the Na 3[sup 2]D levels (at 819 nm) has been unambiguously attributed to photodissociation of NaOH. This emission results from hot-band absorption of the excimer laser, and thus its intensity is temperature dependent and weaker than 3[sup 2]P (589 nm) emission. The technique has been applied to the detection of NaCl and NaOH released during the pyrolysis and gasification of samples of Loy Yang (Australian brown) coal. 13 refs., 9 figs., 1 tab.
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Detector for Trace Elemental Analysis of Solid Environmental Samples by Laser Plasma Spectroscopy
Article
  • Sep 1994
Analysis of heavy metals in soils, sand, and sewage sludge samples has been studied by means of time-resolved optical emission spectrometry from laser-induced plasma. The instrumental setup has been developed as a fast screening detector for future application as an on-line and in situ method. Several experimental parameters had to be optimized. Various factors affecting the detection limits and the quality of the analysis have been investigated. These include aerosol production, crater formation, size effects, timing effects, laser intensities, and humidity. In order to improve reproducibility of elemental analysis, a special data analysis program has been developed. It consists of a data analysis program and of the principal component regression calibration technique, which utilizes many spectral lines for each element. A special renormalization algorithm has been tested for internal calibration. The computer program provides good calibration plots and detection limits in the 10 mu g/g range, which are usually below the ecological requirements.
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Analysis of heavy metals in soils using laser-induced breakdown spectrometry combined with laser-induced fluorescence
Article
  • Jun 2001
  • SPECTROCHIM ACTA B
The investigation of a hyphenated technique combining laser-induced breakdown spectrometry (LIBS) with laser-induced fluorescence (LIF) for the analysis of heavy metals in soils is described. In order to evaluate the applicability of the technique for fast in-situ analytical purposes, measurements were performed at atmospheric pressure. The plasma radiation was detected using a Paschen–Runge spectrometer equipped with photomultipliers for the simultaneous analysis of 22 different elements. The photomultiplier signals were processed by a fast gateable multichannel integrator. Calibration curves were recorded using a set of spiked soil samples. Limits of detection were derived from these curves for As (3.3 μg/g), Cd (6 μg/g), Cr (2.5 μg/g), Cu (3.3 μg/g), Hg (84 μg/g), Ni (6.8 μg/g), Pb (17 μg/g), Tl (48 μg/g) and Zn (98 μg/g) using the LIBS signals. LIBS-LIF measurements were performed for Cd and Tl. The excitation wavelength as well as the detected fluorescence wavelength for Cd was 228.8 nm. Alternatively, Tl was excited at 276.8 nm, where the observed fluorescence wavelength was 351.9 nm. The calibration curves based on the LIF signals showed significantly improved limits of detection of 0.3 and 0.5 μg/g for Cd and Tl, respectively.
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Determination of heavy metals in soils by Laser Induced Breakdown Spectroscopy
Article
  • Mar 2002
  • GEODERMA
Laser Induced Breakdown Spectroscopy (LIBS) is a recent analytical technique that is based upon the measurement of emission lines generated by atomic species close to the surface of the sample, thus allowing their chemical identification. In this work, the LIBS technique has been applied to the determination of total contents of heavy metals in a number of reference soil samples. In order to validate the technique, LIBS data were compared with data obtained on the same soil samples by application of conventional Inductively Coupled Plasma (ICP) spectroscopy. The partial agreement obtained between the two sets of data suggested the potential applicability of the LIBS technique to the measurement of heavy metals in soils.
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