Tag Archives: Lead

01Feb 2012

LEAD Geochemistry-Eh-pH-Solubility and remedial technologies

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Lead is one of the RCRA metals. Low concentration of lead is found in sedimentary and rocks soils. This page documents the very basic geochemistry and important concepts that you should be aware of when dealing with lead contamination. I like to think about this page as LEAD 101!

What is the Maximum Contaminant Limit (MCL) for lead?

  • EPA has set the maximum contaminant level for lead at 0.015 mg/L

Lead concentration in common geologic strata:

Average Lead Cponcentration Concentration Source
Shale 20 mg/Kg Turekian and Wedepohl, 1961
Sandstone 7 mg/Kg Turekian and Wedepohl, 1961
Carbonates 9 mg/Kg Turekian and Wedepohl, 1961
Soil 17-26 mg/Kg Pendias and Pendias (1984)

Lead is similar to K in in ionic size. Ionic substitution is common between lead and potassium in silicates (K-feldspars and biotite in particular). Lead content generally increases from ultramafic to granitic  rocks. Average lead concentration in granites is about 23 mg/Kg

Did you know these FACTS about LEAD?

  • Lead was ranked second on the CERCLA Priority List of Hazardous Substances in 1999 and 2001 (First being Arsenic).
  • Lead is the most commonly RECYCLED metal – 50% of lead production is secondary in nature.
  • 70% of lead produced is used in lead-acid storage batteries.
  • Lead was widely used in the construction of water pipes in 20th century.
  • Lead picments were common in paints prior to 1978!
  • Leaded gasoline (tetraethyl lead) was available between 1923 to 1980s .
  • Most of the lead produced in the USA comes from Missouri.

Sources of lead contamination:

  • fall out of atmospheric dust
  • Industrial/municipal discharge
  • fertilizers
  • lead based paints
  • mining waste

Lead geochemistry is controlled by

  • adsorption at the solid/water interface.
  • Precipitation
  • complexation with organic components

RULE of LEAD: Lead has strong affinity towards soils (adsorbed to soils) and rarely released to surface or ground water.

  • Exception to the rule – low pH system or high dissolved organic carbon (DOC).
Important Lead minerals commonly found:
  • Lead Hydroxide – Pb(OH)2
  • Cerussite -PbCO3
  • Hydrocerussite – Pb3(CO3)2(OH)2)
  • Angelsite – PbSO4
  • Galena – PbS
  • Lead Oxide – PbO

Remedial technologies for lead contamination:

  • Containment (caps and vertical barriers)
  • Solidification/ stabilization
  • Separation/ concentration

Solubility of Lead:

Lead is highly soluble in water over a wide range of pH conditions. In pure water lead forms stable cation Pb+2 below about pH 7. Lead can also form aqueous complexes with OH-, Cl-, SO4– etc. As the pH increases of the solution, lead forms more stable species such as PbOH+, Pb(OH)2, and Pb(OH)3-.

Lead geochemistry and solubility is highly controlled by solution pH and Eh of the environment.

  • Lead is MOBILE in LOW pH and HIGH Eh conditions.
  • Lead is usually NOT a metal of concern in at mining related sites. Acid mine drainage produces sulfate apart from low pH condition which allows lead to precipitate as angelsite (PbSO4).
  • Lead carbonate (Cerrussite) is highly soluble below pH 6; but highly insoluble above pH 8.
  • Thermodymanic data predicts lead hydroxide and lead oxide to be stable. However, kinetically they are difficult to precipitate in room temperature.
  • Lead phosphate minerals are highly insoluble and remedial technologies uses this strategy.
Lead Solubility Diagram

Figure 1: Lead Solubility Diagram (HCO3=SO4=.001 activity)

 

Eh-pH diagram for Lead:

Eh-pH diagrams are not specific to every field conditions that you would encounter. The Eh-pH diagram for lead generated below uses the following activities -

  • Pb activity = 1e-5
  • HCO3- activity= .001
  • SO4– activity = .001
Lead Eh-pH Diagram

Figure 2: Lead Eh-pH Diagram

It is evident from the Eh-pH diagram that lead is mobile at low pH condition (pH<2). With increasing pH, the lead sulfate Anglesite becomes first to precipitate if enough sulfate is available below pH 6. Above pH 6, the carbonates cerussite and hydrocerussite stable. In a reducing condition, galena could also be stable over wide range of pH.

Lead Eh-pH Diagram-2

Fig 3: Lead Eh-pH Diagram-2

Figure 3 is generated with lead activity = 1.E-6. Notice, how lower concentration of lead leads to higher field of soluble phase.

Any Eh-pH diagram could be easily converted in to a pe-pH diagram. The figure below converts the Eh-pH diagram from figure 3 to a pe-pH diagram:

Lead pe-pH Diagram-3

Lead pe-pH Diagram-3

 

Adsorption of LEAD:

  • Hydrous Ferric Oxide (HFO) plays major role in lead mobility as lead adsorbs to HFO stronger than any other divalent metal ions.
  • Adsorption increases as pH in increased between 3 (0% adsorbed) to 6 (100% adsorbed).
  • Lead could also adsorbs to iron sulfide in reducing environment.

Lead Valence states

  • 0, + 2 and +4

Lead Transport:

  • Lead transport in colloidal form could be significant in both surface and ground water. Colloidal particles could be either organic or inorganic.
  • If you are high dissolved lead in your sample, try using 0.1 micron filters for “dissolved” samples.

 

References: 

http://www.epa.gov/nrmrl/pubs/600R07140/600R07140.pdf.

 

26Dec 2011

Fiscal Year 2012 Omnibus Bill Cuts CDC’s Lead Poisoning Prevention Program by 94%

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COLUMBIA, Md., Dec. 26, 2011 /Coal Geology-PRNewswire/ – Ending the federal budgeting process last week, Congress dealt a devastating blow to the fight against childhood lead poisoning. The Omnibus Appropriations Bill cut funding for the CDC’s Healthy Homes Lead Poisoning Prevention Program to $2million—a 94% reduction from FY11.

Lead poisoning still remains a significant environmental public health threat that affects over 30 million homes and nearly a half-million children annually.

Today, parents of lead poisoned children can rely on their state or local health departments for help. A nurse or trained professional will come to their house and find the source of lead poisoning. The program may connect parents to resources to remove hazards and can compel rental property owners to fix hazards. The program also prevents the disease through policies, community education and outreach.

“Congress gave our children a lump of lead this holiday season,” said Rebecca Morley, Executive Director of the National Center for Healthy Housing.

“Studies show that educating a child with lead poisoning costs an extra $38,000. If even half of the children with lead poisoning incur these costs, that’s a $10 billion price tag,” continued Morley. “The cost of eliminating this program is staggering.”

The decision will result in the near-elimination of the program and massive job loss at the state and local levels. The move follows an advisory committee’s recommendation to CDC to lower the threshold for when a child is considered to have enough lead in his or her blood that follow-up action is needed. This change in the “action level” will more than double the caseload of poisoned kids that need the health department’s help.

“The burden on the most vulnerable families just got heavier. Too many children with lead poisoning already go undiagnosed. Without this program, we will return to the era of children being hospitalized for lead. Why is Congress treating our children like canaries in a coal mine?” said Liz Colon, parent and organizer for the Childhood Lead Action Project in Rhode Island.

The impact of these proposed cuts will also fall directly on the backs of low-income families and communities of color that are disproportionately impacted by environmental health hazards. Nationally, African American children are three times more likely to suffer from lead poisoning. In some locales, African American and Latino children are eight to nine times more likely to enter school with a history of lead poisoning. Children poisoned by lead are seven times more likely to drop out of school and six times more likely to end up in the juvenile justice system.

“Lead poisoning is preventable. We are taking a huge step back in protecting our children’s health, safety, and future by eliminating the resources communities need to prevent and address lead exposures,” said Nsedu Witherspoon, Executive Director of the Children’s Environmental Health Network.

The National Center for Healthy Housing (NCHH) is the only national scientific and technical nonprofit organization dedicated to creating healthy and safe homes for America’s children through practical and proven steps. NCHH develops scientifically valid and practical strategies to make homes safe from hazards, to alert low-income families about housing-related health risks, and to help them protect their children.

Media Contact:
Rebecca Morley
(P) 703.868.0554 rmorley@nchh.org

09Nov 2011

EPA Announces Most Areas Meet Air Quality Standards for Lead

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November 9, 2011 (Coal Geology) WASHINGTON – The U.S. Environmental Protection Agency (EPA) has determined that available air quality information indicates that 39 states are meeting the health-based national air quality standards for lead set in 2008. Based on 2008 to 2010 air quality monitoring data, EPA also determined that Illinois, Iowa, Kansas, Michigan and Puerto Rico each have one area that does not meet the agency’s health based standards for lead. Exposure to lead may impair a child’s IQ, learning capabilities and behavior.

 

The agency also is identifying three areas located in Tennessee, Arizona and New York as “unclassifiable,” meaning that available information is insufficient to confirm whether or not the areas are meeting the standards. EPA will take further action once additional information is available.

 

In October 2008, EPA strengthened the nation’s air quality standards for lead ten-fold to 0.15 micrograms of lead per cubic meter of air. EPA also finalized requirements for new monitors to be located near large sources of lead emissions. EPA designated areas as meeting or not meeting the standards in two rounds. Using air quality data from existing monitors, EPA completed the first round of designations in November 2010. This second round in today’s announcement relies on data from the new monitors to classify the remaining areas.

 

Last year, EPA designated 16 other areas in 11 states as not meeting the standards because their 2007 to 2009 air quality monitoring data showed that their emissions were above the agency’s health-based standards. Based on new air quality monitoring information, and recommendations from Pennsylvania, EPA is expanding the size of one of those areas, Lower Beaver Valley, Pa to ensure that the entire area that exceeds the standard is properly identified.

 

Areas designated as not meeting the standards will need to develop plans within 18 months and implement them within five years to reduce pollution to meet the lead standards. No areas in Indian Country are being designated nonattainment.

Lead emitted into the air can be inhaled or can be ingested after it settles. Ingestion is the main route of human exposure. Children are the most susceptible because they are more likely to ingest lead, and their bodies are developing rapidly. There is no known safe level of lead in the body.

National average concentrations of lead in the air have dropped 93 percent nationwide since 1980, largely the result of the agency’s phase-out of lead in gasoline. Lead in the air comes from a variety of sources, including smelters, iron and steel foundries, and piston-engine aircraft operating on leaded aviation gasoline.

More information on the designations: http://www.epa.gov/leaddesignations

 

08Feb 2011

Former Detroit Lead Inspector Donald Patterson Sentenced for Fraud

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February 8, 2011, WASHINGTON(Coal Geology) – Former city of Detroit Health Department lead inspector Donald Patterson was sentenced to three years and 10 months in prison and 24 months of supervised release on wire fraud charges stemming from an U.S. Environmental Protection Agency (EPA) investigation. In July 2010, Patterson pleaded guilty and admitted he accepted cash to provide a clean bill of health to homes in which he had either done no inspection or provided fraudulent lead removal training. Lead is a serious public health issue causing a range of health effects from behavioral problems and learning disabilities, to seizures and death. Children six years old and under are most at risk.

“The actions of this public official put the health and lives of children at risk,” said Cynthia Giles, assistant administrator for EPA’s Office of Enforcement and Compliance Assurance. “In this case, the local government inspector failed to do his job by submitting false reports for personal gain. Today’s sentencing shows that those who knowingly put the public at risk, particularly our most vulnerable citizens, our children, will be prosecuted to the fullest extent of the law.”

Patterson, 50, was employed by the city of Detroit as a lead paint inspector. His job was to ensure that all paint-based lead hazards were safely removed from the homes he inspected. Instead, Patterson used his position to obtain cash from the owners or renters of these homes in exchange for falsely certifying that the homes were free of lead or for providing fraudulent lead removal training. Patterson admitted that between October 2008 and August 2009 he had accepted cash totaling $1,350 in connection with fraudulent abatement of lead hazards to which children were being exposed at four separate properties.

The Patterson case was investigated by EPA and the FBI, with assistance from the city of Detroit and the state of Michigan.

Michigan residents who have concerns about possible lead hazards in their homes should call the Michigan Department of Community Health Hotline at 800-648-6942.
More information on EPA’s criminal enforcement program: http://www.epa.gov/compliance/criminal/index.html
To report an environmental violation: http://www.epa.gov/compliance/complaints/index.html
More information on lead: http://www.epa.gov/lead/pubs/leadinfo.htm#health