California State University, Sacramento: Lead Study

Transcription

1 California State University, Sacramento: Lead Study Chemistry Department Justin Miller-Schulze, Ph.D. Hector Ceja, Undergraduate Environmental Studies Department Jeffery Foran, Ph.D. Amaryl Griggs, Undergraduate 016

2 Background Lead exposure from drinking water is a hazard to adults and especially women and children. Can be accumulated over a lifetime and be stored in bones. It is released into blood during pregnancy. According to CDC, there is no safe level of lead even at low exposure levels. EPA has set the maximum contaminant level goal (MCLG) for lead in drinking water at 0. EPA s action level for lead is 15 ppb 017

3 Potential Health Risk 15 μg/l is the EPA s action level for drinking water, but the CDC has not yet determined there to be a safe level of lead exposure, especially for children. New reference level of 5 ug/dl to identify children with blood lead levels that are much higher than most children s levels. T Level is based on the U.S. population of children ages 1-5 years who are in the highest 2.5% of children when tested for lead in their blood. Nearly 310,000 US children between 1-5 years may have blood lead levels at or greater than 10 μg/dl blood Effects of exposure are cumulative and come from many sources. Primary Routes of exposure: Ingestion, inhalation Drinking water, air, foods, swallowing dust or dirt Risk for Children and Pregnant Mothers Only about 32% of lead taken into a child s body will be processed as waste. Continued exposure results in accumulation in body tissue and bone For children, high lead exposure may cause: anemia, brain damage, kidney damage and muscle weakness Low levels of exposure in children may still negatively affect physical and mental growth High levels of exposure may lead to miscarriage Exposure to fetuses may have slow mental development and lower IQs past childhood Brown, M., S. Margolis (2012) Lead in Drinking Water and Human Blood Lead Levels in the United States. U.S. Department of Health and Human Services. (2007) Toxicological Health Profile for Lead

4 Sampling Locations Buildings at risk for lead contamination are those built before 1986 when the amendment to the Safe Drinking Water Act banned lead and lead solder used in plumbing. For initial sampling, 6 buildings built prior to 1986 were chosen Douglass (1953), Alpine (1957), Sequoia (1967), Humboldt (1967), Tahoe (1979), Amador (1981) 2 buildings built after 1986 were chosen Mendocino (1990), Mariposa (2000) We hypothesized that older buildings will have a higher concentration of lead compared to newer buildings. 019

5 Preparations Glassware and sample bottles were cleaned with 5% nitric acid solution prior to use for sample preparation All samples and standards were treated to 1% nitric acid of the final solution All graduated cylinders, pipettes, large 4.5L solvent bottles were sitting in 5% nitric acid solution Nitric acid reagent grade for spectral analysis 020

6 Sampling Methods Eight buildings were sampled between 6-7am on Mondays to ensure little usage from over the weekend ml of water from drinking fountains was collected in 250mL bottles. Bottles conditioned with fountain water for 3 seconds before collection. Immediately placed on ice. Field replicates and nanopure water blanks were collected in each building. All samples were acidified with 1mL of 1% Nitric Acid. 021

7 Atomic Absorption Spectrometer Aanalyst 800 With Perkin Elmer Auto- Sampler 800 -The Atomic Absorption Spectrometer (AAS) has different techniques -Transverse Heated Graphite Atomizer (THGA): can measure in the ppb range, requires small sample volumes (20μL), and takes about 2.5-3min per sample. -With the auto-sampler, it has the capability of generating it s own standards by diluting high semi-stock solutions -Problems arose when using the autosampler, so standards made manually 022

8 023 Overview of Mechanics and Furnace Program

9 Matrix Problem The matrix is composed of everything in the sample other than the analyte (solvent, organic material, metals, etc) and can lead to inconsistent and low absorbance readings. Matrix Modifier, Palladium Nitrate: -makes the matrix more volatile so that it vaporizes before the atomization step -stabilizes lead until the atomization step -Spring only 5μL of Palladium matrix modifier per 20μL of sample -Summer required 20μL matrix modifier per 20μL of sample Had to adjust furnace temperature settings in order to get narrow and strong absorbance peaks 024

10 Duplicate Spiked: Modifier vs No Modifier Corrected Abs Sample #0013 Spikes: Modifier vs No Modifier y = x R² = #0013 #0013 5uL MM y = x R² = Sample #0014 Spikes: Modifier vs No Modifier Corrected Absorbance y = x R² = #0014 y = x R² = #0014 5uL MM Concentration Pb ppb Concentration Pb ppb 025

11 Absorption Optimization Altering Atomization Temperature in Furnace Program 1800 C Steps of Furnace programmed for each sample 1. First Drying (removes water/solvent) 2. Second Drying (removes water solvent) 3. Charring (removes organic material) 4. Atomization (metal becomes into gas phase) 5. Clean out (cleans tube for next sample) Right shows absorbance peaks of 10ppb nanopure sample using 20μL modifier. Increasing temperature gives high absorbance and narrow peaks to give higher slopes for the regression line 1600 C 1500 C 026

12 Lowering LOD and LOQ by Optimizing Absorbance Optimization of Absorbance 5μL vs 20μL y = x R² = Corrected Abs uL Matrix Modifier 20uL Matric Modifier y = x R² = Concentration ppb 027

13 Quality Control For Final Method Results Standard curve equation was y= x with a R^2 of Accuracy of concentration using equation for standards ranged % Both spikes and non spikes were used to check precision with a value less than 7.3% RSD (Alpine drinking FT water) Accuracy for Alpine 1 st floor spikes at 2ppb and 10ppb ranged from % (neglecting one trial %) Accuracy for 10ppb standard repeats was average of 110, with a precision of %RSD Level of Detection (LOD): [3*SD(blanks)]/slope 0.17ppb Level of Quantification (LOQ): [10*SD(blanks)]/slope 0.57ppb 028

14 Initial Sampling Building Date Start Time # Fountains Collected From Sequoia 3/7/2016 6:29 AM 6 Humboldt 3/7/2016 6:44 AM 2 Alpine* 3/7/2016 6:52 AM 2 Douglass 3/7/2016 6:54 AM 2 Amador* 3/14/2016 6:28 AM 5 Mendocino 3/14/2016 6:38 AM 5 Tahoe 3/14/2016 6:42 AM 3 Mariposa* 3/14/2016 7:01 AM 5 029

15 Total Sampling Results Sample ID Location Lead Concentration (ug/l) Uncertainty ug/l Sample ID Location Lead Concentration (ug/l) #0001 Sequoia 5th Floor <LOD #0026 Douglas 1st Floor <LOD #0002 Sequoia 4th Floor <LOD #0027 Douglas 1st Floor <LOD #0003 Sequoia 3rd Floor <LOQ #0029 Tahoe 2nd Floor <NQ #0004 Sequoia 3rd Floor <LOD #0031 Tahoe 3rd Floor (Long Pull) <LOD #0006 Sequoia 2nd Floor (Bottle Filler) <LOD #0032 Tahoe 1st Floor <NQ #0007 Sequoia 2nd Floor <LOD #0033 Amador 3rd Floor #0008 Sequoia 1st Floor <LOD #0035 Amador 4th Floor <LOQ #0009 Humbolt 1st Floor <LOD #0036 Amador 2nd Floor <NQ #0010 Humbolt 2nd Floor <LOD #0037 Tahoe 2nd Floor <LOQ #0012 Humbolt 2nd Floor <LOD #0038 Amador 2nd Floor (Long Pull) <LOQ #0013 Alpine 1st Floor #0039 Amador 2nd Floor <LOQ #0014 Alpine 1st Floor #0040 Tahoe 3rd Floor <LOQ #0016 Alpine 2nd Floor <LOD #0061 Mendocino 5th Floor (#3) <NQ #0017 Amador 1st Floor <LOD #0062 Mariposa 1st Floor (Right) <LOD #0018 Amador 5th Floor <LOD #0065 Mendocino 4th Floor (#3) <LOD #0019 Mendocino 1st Floor (Middle) <LOD #0069 Mariposa 5th Floor (Right) #0020 Mendocino 3rd Floor (Middle) <LOD #0070 Mariposa 2nd Floor (Right) <LOD #0021 Douglas 2nd Floor <LOQ #0071 Mariposa 2nd Floor (Right) <LOD #0022 Douglas 1st Floor <LOD #0073 Mariposa 3rd Floor (Left) <LOD #0023 Mendocino 2nd Floor (Middle) <LOD #0074 Mariposa 4th Floor (Right) <LOD #0024 Mendocino 3rd Floor (Middle) <LOD #0025 Douglas 1st Floor <LOD Uncertainty ug/l 030

16 CSUS Quantifiable Results Location CSUS 3/7 & 3/14 CSUS 6/13 CSUS 6/16 CSUS 6/23 Alpine Fl Alpine Fl 2 ND NQ Amador Fl Mariposa Fl Sequoia Fl 4 ND

17 BSK Contract Lab To further confirm and compare our results, samples with detectable levels were sent to BSK Associates BSK specializes in potable water quality chemistry EPA certified methods 032

18 Resampling Results & BSK Associates Lab Comparison Drinking fountains with detectable and quantifiable levels of lead (>0.5ug/L) were resampled and analyzed. These samples along with the original samples that had detections were sent to BSK Associates to compare results. Sample Set Collection Date Results ug/l Location CSUS 3/7 & 3/14 BSK 3/7 & 3/14 CSUS 6/13 BSK 6/13 CSUS 6/16 BSK 6/16 CSUS 6/23 BSK 6/23 Alpine Fl Alpine Fl 2 ND 0.29 NQ ND Amador Fl Not Analyzed 2.40 Mariposa Fl Sequoia Fl 4 ND *ND: Not detected at reporting limit *NQ: Below limit of quantification 033

19 034 CSUS vs. Contract Lab Results

20 Statistical Evaluation of CSUS vs. BSK To investigate if our methodology ( CSUS ) gave statistically significant different concentrations than the contract lab ( BSK), we used a paired t-test (95% confidence, 11 degrees of freedom) This test did not disprove the null hypothesis (that both methods are equivalent) at 95% confidence, 2-tailed Non-detects for either method were excluded from this analysis Methods are equivalent statistically 035

21 Future work What to do with the data? What is the impact of this data? Is there a health risk? 036

22 037 Results

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