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EPA Proposes 90 Day Public Comment Period Concerning Revisions to the National Contingency Plan; Subpart J which Allows the Use of Oil-Dispersing Agents during Oil Spills

EPA Proposes 90 Day Public Comment Period Concerning Revisions to the National Contingency Plan; Subpart J which Allows the Use of Oil-Dispersing Agents during Oil Spills

 

On January 22, 2015, EPA released proposed revisions to the National Contingency Plan; specifically Subpart J (Product Schedule) which governs the use of spill-mitigating substances (including dispersants and other biological and chemical agents) in response to oil discharged into navigable U.S. waters. The agency’s proposal adds new criteria to the NCP Product Schedule, revises toxic testing protocols; amends requirements for authority notifications, monitoring, and data reporting; and clarifies the evaluations needed to remove products from the schedule. The last revision to the National Contingency Plan occurred in response to the passage of the Oil Pollution Act of 1990. To learn more, check out the Subpart J Proposed Rule Summary.

Public comments will be accepted only through the official docket: EPA-HA-OPA-2006-0090.

Photo above courtesy of NASA's Tara Satellites. The photo was taken on May 24, 2010 of Deepwater Horizon Oil Spill.

 

 

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ANAMAR Crew Completes Assessment of the Columbia River ODMDS

ANAMAR Crew Completes Assessment of the Columbia River ODMDS

ANAMAR scientists have been working off the coast of Oregon at the mouth of the Columbia River monitoring the chemical, physical, and biological aspects of an ocean dredged material disposal site (ODMDS). Part of the goal for this project was to calculate the health and abundance of epifauna and infauna in the area, including an important species, the Dungeness crab.

Pictured is the crew preparing crab traps.

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Port Aransas Sampling Expected to Begin Tomorrow

Port Aransas Sampling Expected to Begin Tomorrow

 

ANAMAR’s sampling team, Terry Cake and Manager Michelle Rau, is in Corpus Christi Bay area and will start sampling operations tomorrow. The sampling will be performed at the federally maintained Corpus Christi Ship Channel and the offshore ocean dredged material disposal site (ODMDS). Good luck to the sampling crew!

 

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Data Reporting for Chemical Testing

(Excerpted from the Southeastern Regional Implementation Manual [SERIM])

 

7.3   Data Reporting for Chemical Testing

All chemical data should be summarized and presented in tabular format. Additionally, all laboratory data should be provided in the Testing Report (see Appendix D) and in electronic tabular format (e.g., spreadsheet, delineated text file). Analytical data reported by the laboratories [with National Environmental Laboratory Association Conference (NELAC) standard qualifiers] must be included in the appendix section of the report.

PCB congeners should be reported as individual congeners as well as total PCBs. Total PCBs should be reported as EPA Region 4 PCBs and as NOAA PCBs. EPA Region 4 PCBs represents the sum of all the PCBs listed in Table 5-6. NOAA PCBs represents the sum of the PCB congeners identified by an asterisk in Table 5-6 and are calculated by the following equation:

              cem. testing photo 1(NOAA, 1989)           [Eq. 7-1]

In addition to the individual PAHs, total PAHs should also be provided as total low molecular weight (LMW) PAHs and total high molecular weight (HMW) PAHs, as described in Table 5-5.

Organotin must be reported as the individual compounds and total organotin. Total organotin should be reported on a tin basis as follows:

chem. testing photo 2[Eq. 7-2]

Refer to Section 5.2 for information on reporting data to the TDLs and LRLs. All data should be certified to be accurate by the analytical laboratory or by a third-party data validator.

Source:

USEPA/USACE. 2008. Southeast Regional Implementation Manual (SERIM) for Requirements and Procedures for Evaluation of the Ocean Disposal of Dredged Material in Southeastern U.S. Atlantic and Gulf Coast Waters. EPA 904-B-08-001. U.S. Environmental Protection Agency Region 4 and U.S. Army Corps of Engineers, South Atlantic Division, Atlanta, GA.

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Sampling Reference Stations

Sampling Reference Stations

Excerpted from the Southeastern Regional Implementation Manual (SERIM)

4.3 Sampling Reference Stations

For dredged material evaluations for ocean disposal, the test results from proposed dredging site samples are compared to test results from appropriate reference site sediments. Reference sediment is defined as “A sediment, substantially free of contaminants, that is as similar to the grain size of the dredged material and the sediment at the disposal site as practical, and reflects conditions that would exist in the vicinity of the disposal site had no dredged-material disposal ever occurred, but had all other influences on sediment condition taken place” (1991 Green Book, Section 3.1.2). Reference sediment sampling stations are selected to simulate conditions at the proposed disposal site in the absence of past dredged material disposal. Reference sediments must be collected for each evaluation. Results from previous evaluations are not acceptable. Test organisms should be selected to minimize sensitivity to possible sediment grain size differences among the reference site, the control site, and the proposed dredging site.

Using historical reference sites and EPA Region 4 studies of reference areas, EPA Region 4 has identified preferred reference sites for each ODMDS for various grain size distributions. These sites are identified in Appendix K. One or more of these sites may be used and should be selected based on the grain size of the proposed dredged material. These reference areas shall be utilized. Alternative reference sites will be approved on a case-by-case basis.

Reference sediments may be collected from (1) a single reference-sediment sampling location; or (2) from a number of approved locations. Reference samples may be composited and tested according to guidance provided in Chapter 8 of the 1991 Green Book.

Replicate sediment samples should be collected at the reference site(s) using an appropriate collection device [see Table 5 for the EPA QA/QC Guidance (EPA, 1995)]. In most cases, a grab sample is adequate for reference sediment stations. Replicates may be composited into a single sample [see Chapter 8 of the 1991 Green Book or Chapter 4 of EPA (2001b) for guidance]. The collected sediment should be of sufficient quantity to conduct all required testing. A minimum of three replicate sediment samples from the reference site(s) should be collected for all testing [i.e., three grabs at one site or one grab at three sites or any other combination for a minimum of three grabs].

Citation: USEPA/USACE. 2008. Southeast Regional Implementation Manual (SERIM) for Requirements and Procedures for Evaluation of the Ocean Disposal of Dredged Material in South­eastern U.S. Atlantic and Gulf Coast Waters. EPA 904-B-08-001. U.S. Environmental Protection Agency Region 4 and U.S. Army Corps of Engineers, South Atlantic Division, Atlanta, GA. http://www.epa.gov/region4/water/oceans/documents/SERIM_Final_August 2008.pdf

 

 

 

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NOAA Publishes Data Collected from the Deepwater Horizon Oil Spill

On April 20, 2010, the Deepwater Horizon offshore oil drilling rig exploded and started leaking oil 5,000 feet below the ocean’s surface in the Gulf of Mexico. A process known as a Natural Resource Damage Assessment (NRDA) was set in motion under the Oil Pollution Act of 1990. With the combined help of many federal and state agencies, private industries, and academic institutions, years’ worth of data have been collected and the analytical chemistry results from the Deepwater Horizon oil spill have finally been made available to the public.

Here is a link to the site where you can find those results:

http://www.nodc.noaa.gov/deepwaterhorizon/specialcollections.html

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Physical and Chemical Testing of Dredged Material

Physical and Chemical Testing of Dredged Material

Note: This blog is an excerpt from the SERIM* (Southeastern Regional Implementation Manual) concerning the physical and chemical testing of dredged material.

5.0    PHYSICAL AND CHEMICAL TESTING OF DREDGED MATERIAL

Testing is frequently required to characterize the physical and chemical properties of sediments proposed for dredging and disposal. The following information supplements Section 9.0 of the 1991 Green Book and Section 2.8.1 of the QA/QC Manual (EPA, 1995). Strict adherence to established testing protocols and detection limits while conducting all analyses will aid in expediting review and concurrence for projects. Any deviation from these protocols should be approved by the USACE SAD district and EPA Region 4 prior to analysis. Such deviation should be clearly defined in the SAP (see Sections 2.2 and 4.1). Established QA/QC procedures must be followed (see Section 8.0).

5.1   Physical Analysis

Sediment proposed for dredging and disposal and reference sediments should be analyzed for grain size distribution, TOC, and total solids/percent moisture (Table 5-1). In addition, specific gravity, bulk density, and Atterberg limits may be required on a case-by-case basis. Atterberg limits should be determined when clumping of dredged material is expected during disposal (e.g., new work projects in cohesive clays). The grain size analysis should be conducted according to the methods described in Plumb (1981) or ASTM (2002) and reported as percentages retained by weight in the following size classes, at a minimum:

  • Gravel
  • Coarse Sand
  • Medium Sand
  • Fine Sand
  • Silt/Clay (expressed as “Fines”)

Gravel and sand fractions should be separated using the standard sieve sizes indicated in Table 5‑1 and reported as cumulative frequency percentages (Section 7.1). The USCS should be utilized and each sample assigned the appropriate two-letter group (see ASTM, 2006). There may be cases where silt and clay fractions will need to be distinguished. USACE SAD districts and EPA Region 4 will provide guidance on a case-by-case basis on whether it is needed. Silt and clay fractions should be quantified by hydrometer (ASTM, 2002), pipette, or Coulter Counter (Plumb, 1981). Use of a laser diffraction grain size analyzer is also acceptable (Loizeau et al., 1994). Total solids and percent moisture should be measured as described by Plumb (1981) or APHA (1995).

It should be noted that the results of the above physical analyses may be used to support compliance with one or more of the three exclusionary criteria in 40 CFR 227.13(b) for ocean disposal (see Section 3.1.1).

 

Table 5-1. Parameters Used for the Physical Characterization of Sediments

Parameter

Method

Measure/Quantitation Limit

Grain Size Distribution

Plumb, 1981; ASTM, 2002

 

Gravel (>4.75mm)

Retained on No. 4 sieve

Coarse Sand (2.0-4.75mm)

 

Passing through No. 4 sieve and retained on No. 10 sieve

Medium Sand (0.425-2.0mm)

 

Passing through No. 10 sieve and retained on No. 40 sieve

Fine Sand (0.075-0.425mm)

 

Passing through No. 40 sieve and retained on No. 200 sieve

Silt (0.005-0.075mm)

 

As determined by hydrometer, pipette or Coulter counter/laser particle size analyzer

Clay (<0.005mm)

 

As determined by hydrometer, pipette or Coulter counter/laser particle size analyzer

Total (percent) Solids

Plumb, 1981

Value based on mass. 1.0%

Total Organic Carbon

9060 (SW846)

0.1%

Specific Gravity

Plumb, 1981

 

Atterberg Limits*

ASTM 4318D

 

*Not needed in all cases. Consult your USACE district and EPA prior to analysis.

5.2   Chemical Analysis of Sediments

As discussed in Section 3.2.1.1, chemical analysis of sediments can be used to document compliance with applicable EPA WQC or state WQS. However, it cannot be used for determination of water column toxicity or the assessment of contaminant toxicity and bioac­cumulation from the material to be dredged. As discussed in Section 3.2.2, sediment chemistry can be used to screen out sediments that are not likely to meet the LPC or to assist in selecting a compositing or testing scheme under Tier III. It can also be used in Tier I as part of confirmatory analysis (see Section 3.1.2). It should be noted that chemical analysis of sediments is not required to document compliance with the ocean dumping criteria, but can be a beneficial tool in evaluating current and future projects.

The COCs that should be analyzed on a routine basis are listed in Tables 5-3 through 5-7. The routine metals, polychlorinated biphenyls (PCBs), polynuclear aromatic hydrocarbons (PAHs), and pesticides listed in these tables were chosen based on the requirements of 40 CFR 227.6, their toxicity, their persistence in the environment, their ability to bioaccumulate, and their widespread and consistence occurrence in the estuarine, marine, and freshwater sediments and organisms of the southeastern United States. These lists can be reduced or expanded based on site-specific knowledge of pollution sources or historical testing showing the presence or lack of presence of specific contaminants. Table 3-2 provides a list of resources for determining COCs. It should be explicitly stated in the SAP when listed contaminants will not be analyzed. One of the primary sources of dioxin-like compounds [chlorinated dibenzo‑p‑dioxins (CDDs), chlorinated dibenzofurans (CDFs), and certain PCBs] in surface water is bleached pulp and paper mills (EPA, 2001c). Dioxin-like compounds will be added to the analyte list when pulp and paper mills are or were present upstream in the watershed of the proposed dredging area unless it has been previously documented that these compounds are not present within the sediments in the vicinity of the project. Other major sources of dioxin-like substances to the air and land that could deposit in sediments include solid and medical waste incineration, secondary copper smelting, and cement kilns (EPA, 2001c). If any of these activities are present in the project vicinity, dioxin-like compounds should be considered. Appropriate methods and target detection limits for the dioxin-like compounds and any other supplemental COCs can be found in Appendix M of this document, the EPA QA/QC Guidance (EPA, 1995), the Inland Testing Manual, or the 1991 Green Book. If sediment chemistry is to be used in the screening method (Section 3.2.1.1) to document compliance with the WQC, analyses must be performed for all analytes listed in Appendix F.

The target detection limits (TDLs) listed in the tables are performance goals (EPA, 1995). Laboratory reporting limits (LRL) for each project should be at or below these values (Jones and Clarke, 2005). LRLs are the minimum levels at which a lab will report analytical chemistry data with confidence in the quantitative accuracy of that data. LRLs are adjusted for sample-specific parameters such as sample weight, percent solids, or dilution. As routine data acceptance criteria, the LRLs for each analyte should be below the listed TDL, with the caveat that some sediments with higher percent moisture content may have LRLs above the TDLs. It is the applicant’s (USACE SAD district for Civil Works projects) responsibility to meet the TDLs. Some laboratories have had difficulties in the past meeting the required TDLs because of inappropriate sample preparation and clean-up procedures to remove interfering substances typically found in marine sediments (e.g., elemental sulfur). If the TDLs cannot be attained, a detailed explanation should accompany the data providing the reasons for not attaining the required TDLs. Re-analysis may be necessary or the contaminant may have to be assumed to be present at the reported LRL. Appropriate sample preparation, clean-up, and analytical methods have been developed for estuarine/marine sediments by the National Oceanic and Atmospheric Administration (NOAA) (1993) and the EPA research laboratory at Narragansett, RI (EPA, 1993a). Established sample and clean-up procedures are presented in Table 5-2.

*Source:

USEPA/USACE. 2008. Southeast Regional Implementation Manual (SERIM) for Requirements and Procedures for Evaluation of the Ocean Disposal of Dredged Material in South­eastern U.S. Atlantic and Gulf Coast Waters. EPA 904-B-08-001. U.S. Environmental Protection Agency Region 4 and U.S. Army Corps of Engineers, South Atlantic Division, Atlanta, GA. http://www.epa.gov/region4/water/oceans/documents/SERIM_Final_August 2008.pdf

 

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Word from the Field: Oregon ODMDS Sampling

Word from the Field: Oregon ODMDS Sampling

 

Congratulations to the ANAMAR crew working on the Ocean Dredged Material Disposal Sites off the Oregon coast. They completed sampling eight stations in and around the Chetco ODMDS yesterday and are collecting samples from the Coquille site today. While sampling, the crew spotted a grey whale and witnessed some picturesque fog rolling through.

Pictured above is the box corer the crew used to collect samples from the Chetco ODMDS, and below is a photo of the Oregon fog.

michportlpic2 FILEminimizer

 

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A Brief History of the Gulf Sturgeon

A Brief History of the Gulf Sturgeon

 

sturgeon 1The Gulf Sturgeon (Acipenser oxyrinchus desotoi) are modern descendants of a group of ancient freshwater fish called Chondrostei which, along with alligators and crocodiles, were able to survive the mass extinction of the Mesozoic Era. Gulf Sturgeon have been known to swim into both fresh and saltwater to feed and uniquely possess a protruding suction mouth that makes it easy to obtain food from riverbeds, lakebeds, and the bottom of the Gulf of Mexico. Gulf Sturgeon have an average lifespan of 20 to 25 years and grow to a maximum length of 7½ feet, with an average body weight of 150 to 200 lbs., but have been known to reach weights of up to 300 lbs. Gulf Surgeon males become sexually mature at about age 8 and spawn every year after that, while the females become sexually mature at age 12 and spawn only three to four times during their lifespan. Females require 3 years to develop each batch of 200,000 to 500,000 eggs, of which only few will actually survive. Disease, water quality, predators, and a number of other factors claim 99.999% of eggs, hatchlings, and juveniles. USGS calculates that females need to successfully produce only two offspring to maintain a stable population.

In 1991 the federal government granted protection to the Gulf Sturgeon under the Endangered Species Act after a massive population decline occurred due in part to over fishing, damming of rivers, and pollution. Thanks to the many agencies, organizations, and private citizens that have continued to work together to help maintain accurate scientific research and field data, this species that links back 200 million years can still be found among today’s aquatic fauna.

 

A word from the field from ANAMAR’s Christine Smith:sturgeon 2

“Here are some photos from today’s USGS sturgeon-tagging effort.  We caught about 15 fish on the Suwannee near Manatee Springs.  Normally they catch more, but the DO [dissolved oxygen] was pretty low in the area.  We scanned for previous tags, weighed, measured fork and total length, tagged, and took blood samples.  Prior to fishing we ran a few sidescan transects to try to identify individual sturgeon as well as habitat.”

–Christine Smith on July 30, 2013

 

(Photos courtesy of Christine Smith)

 

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Significant Figures Part III

How Many Significant Figures or Decimal Places Are Correct?

The number of sig figs or decimal places that should be presented is often a decision to be made by the end user. In many instances, showing one or two sig figs is adequate; for example, in a simple comparison determining whether a result is less than or greater than a benchmark value. If the results will undergo substantial statistical evaluation or other arithmetic calculations, then more sig figs would be recommended. As a general rule, it is better to keep at least one additional sig fig through all calculations and round afterwards rather than rounding first.

One famous example for keeping extra sig figs and decimal places for calculations is the original “butterfly effect.” In 1961, a mathematician/meteorologist named Edward Lorenz was using a computer to simulate weather effects. He entered a value that had been rounded from six decimal places to only three, which represented about a 0.025% difference in the value. After he ran the program, he realized that the result represented a completely different weather pattern than if he had used all six decimal places. During later presentations, this effect took on its more popular meaning, which is still in use today.

At the other end of the spectrum, it is possible to provide far too many sig figs. Since computers and calculators became common, they have been used more and more frequently for data collection and analysis. If the data are being calculated using mathematical formulae (e.g., linear or quadratic regression), the computer could easily provide 32 or more sig figs in its evaluation. If this were presented as a single whole number, for example, it would be the equivalent of counting the number of grains of sand in a pile the size of Earth.

Some things to keep in mind when determining how many sig figs should be presented is how the data will be collected, limits in the ability to precisely measure a value, and if the data collected represents an exact measurement or is instead measuring a sample. For example, counting the number of children enrolled at each elementary, middle, and high school in a state is relatively straightforward. An exact count can be provided fairly easily, so a number that has six or seven sig figs would be appropriate.

On the other hand, counting the total number of people living in a state would be more challenging, since it would include births, deaths, and people moving into and out of the state. In addition, there may be a certain number of people who are temporary residents. Since all these changes can happen hundreds or even thousands of times per day, it would be more appropriate to provide only three or four sig figs for a statewide population count.

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The HMS Challenger; One of the Earliest Scientific Expeditions That Changed the Course of Scientific History

The HMS Challenger; One of the Earliest Scientific Expeditions That Changed the Course of Scientific History

The HMS Challenger set sail on December 21, 1872, from Portsmouth, England, containing an impressive crew of physicists, chemists, biologists, artists, and expert navigators, all of which shared the common goal of circumnavigating the globe while studying the flora and fauna that live within our oceans. On its 68,890-nautical-mile-voyage, the Challenger obtained 492 deep-sea soundings, 133 bottom samples, 151 open-water trawls, and 263 serial water temperature readings. It is estimated that on this voyage nearly 4,700 new species of marine life were discovered. Among some of the instruments used during this voyage were a shallow-water dredge, a deep-sea trawl (that had no closing device), specimen jars containing alcohol for preservation, thermometers and water sampling devices such as the Buchanan water sampler, 144 miles of Italian hemp rope, and 12.5 miles of piano wire for sampling gear, as well as many microscopes and instruments for the on-board laboratories. The ship contained a natural history laboratory where specimens were examined, identified, dissected, and drawn, and a chemistry laboratory containing a (then) state-of-the-art boiling device called a carbonic acid analysis apparatus, used for analyzing carbonic acid contained in samples.

References:

  1. Oceanography: An Introduction to the Marine Environment (Peter K. Weyl, 1970)
  2. Rice, A.L. (1999). "The Challenger Expedition". Understanding the Oceans: Marine Science in the Wake of HMS Challenger. Routledge.27–48
  3. http://en.wikipedia.org/wiki/Challenger_expedition
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Sediment Testing Interference Series – Part IV

Specific Types of Interferences and Solutions (continued from Part III)

Toxicological Interferences

Whereas chemical testing is used to determine the concentration of target contaminants in a sediment sample, toxicological testing is used to determine the effects of the sediment on the survival and development of multiple representative species. Since the organisms will be affected by the sediment as a whole, and since the material is typically a mixture of sand, silt, and clay with numerous chemical contaminants present, it may be difficult or impossible to determine the exact cause of high mortality or abnormal development. Several interferences, or confounding factors, have been identified, however, and are described below.

Ammonia

Above certain levels, ammonia is highly toxic to most marine organisms. It is also a non-persistent toxicant in the environment, and procedures have been developed to help reduce ammonia to more tolerable levels for the test organisms. These procedures were initially developed for the more sensitive benthic species, but, with EPA approval, can also be applied to other organisms under certain circumstances.

Total Organic Carbon (TOC) Availability and Quality

Changes in the nature of TOC in the dredge material may pose limitations to test organism survival. Organic compounds can change over time, particularly with changes in temperature, moisture content, and oxygen availability. If the quality of TOC degrades over time, it can affect the survival of certain species, e.g., for Leptocheirus plumulosus due to poor quality food in the sediment. Though the sediment may have low toxicity, survival can be substantially reduced. Providing a small amount of food for the organisms during analysis alleviates the problem and allows for a more accurate determination of toxicity.

Salinity

Marine organisms are sensitive to the salinity of the test sediment. Sediment collected from far upstream or from terrestrial locations will often have much lower saline levels than sediment from offshore locations and could cause stress to the test organisms and increase mortality. An acclimatization period for the sediment, typically lasting a few days to 3 weeks, will gradually expose the sediment to saline. Once the acclimatization is completed, the test organisms can be added and testing can commence.

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Sediment Testing Interference Series – Part III

Specific Types of Interferences and Solutions (continued from Part II)

Organic Interferences

Organic compounds (PAHs, pesticides, PCBs) are typically measured by either mass spectroscopy or retention time. Because of a preliminary extraction procedure, salt does not interfere in the analysis of organic compounds, but sediment can still be affected by matrix interferences in a number of ways.

  • Complex organic molecules can bind together or degrade over time and form non-target compounds.
  • New contaminants that have the same characteristic mass or retention time as the target analyte can be introduced into the environment (from leaking vessels or industrial runoff, for example).
  • Sediment will likely settle into separate layers, leading to different chemical and physical characteristics in each layer. The sediment will require thorough homogenization prior to analysis to ensure that it is representative of the site.

There are a variety of solutions to eliminate or minimize potential interferences during preparation and analysis.

  • Commercially available cartridges are used to remove or “clean up” interfering (non-target) compounds for most organic analytical groups, such as PAHs, pesticides, and PCBs.
  • Using more-sensitive equipment can help distinguish target compounds from interfering compounds. High resolution mass spectroscopy (HRMS) is often used for testing parameters such as dioxins and PCBs to narrowly target specific compounds. Results from these procedures will often be much more sensitive than when ordinary mass spectrometer tests are applied, but these procedures are also considerably more costly. As one example, the cost for analyzing PCBs by gas chromatography is around $200 per sample, but for HRMS it is around $800 per sample.
  • Different types of detectors are available for different analyses. For example, an electron capture detector is useful for pesticide and PCB analysis.
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Sediment Testing Interference Series – Part II

Specific Types of Interferences and Solutions

 

Metals Interferences

Most metals analyses are performed by spectroscopy, generally by inductively coupled plasma (ICP) with or without a mass spectrometer attached. A small volume of prepared sample will be introduced into the instrument and energized using an argon plasma. The resulting plume will emit light at specific wavelengths in proportion to the concentration of contaminants present in the sample and is read using a detector measuring across a narrow band pass. For example, copper will emit light at a wavelength of 324.7 nm. When dealing with high-saline samples, various cations (including sodium, calcium, and magnesium) will be present. Calcium is a potential interfering element because it emits at a wavelength peak of 316.9 nm and with a band pass that overlaps that of copper.

Several options exist for dealing with these interferences:

  • Extract the metals into an organic reagent, such as methyl isobutyl ketone, effectively removing the salt interferences.
  • Change instrumentation. For example, use a borohydride generator for selenium analysis.
  • Prepare instrument standards in the same matrix as the project samples. This procedure will work if the interfering metals or compounds are of moderate concentrations.

A 2010 project audited by ANAMAR provides a good example that saline interferences can produce false positive readings. Based upon historical results, background levels for copper are typically around 1 µg/L. The results found for this project were in the range of 150 to 170 µg/L, and further evaluation by the ADDAMS model was indicated since the sample levels were above the federal water quality criteria. A review by the contractor and the analytical laboratory indicated that all batch QC was within limits, and the data appeared to have been analyzed and reported correctly. After some investigation, it was found that the contractor for this project did not include any procedures to reduce the saline interferences before analysis.

After discussion among the contractor, USACE, and EPA, it was determined that the copper analysis would be re-done using a saline-reduction procedure. Due to holding times and an insufficient volume of sample collected on the first sampling event, the contractor had to return to the project site to collect additional sediment and site water. Upon analysis of the elutriate using the saline-reduced sample, copper levels fell in line with historical levels, and further evaluation of the elutriate by the ADDAMS model was no longer necessary.

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Sediment Testing Interference Series – Introduction - Part I

During the course of an environmental dredging project, samples will be collected and sent to one or more laboratories for analysis. For most dredging projects, the samples collected will be of a complex nature and will often contain various types of interferences that must be addressed during analysis to ensure that the most accurate results are reported to the client and to the regulatory agency reviewing the results for final sediment disposal options.

Interferences may be found in any type of analytical testing. For dredging projects, such as those falling under MPRSA Section 103 protocols, testing will be required for physical, chemical, and toxicological parameters. This four-part blog will describe the most typical and lesser-known types of interferences.

Chemical Interferences during Chemical Analysis

Chemical matrix interferences are encountered when the project sample contains a constituent that either produces a signal indistinguishable from a target analyte or attenuates the target signal. Elutriate samples for ocean dredging projects have many common types of matrix interferences (e.g., saline) for trace metals analysis. In addition, the chemical composition of the project samples may have interfering compounds specific to the sampling location.

The most common interference found when analyzing dredge material is saline interference with the analysis of metals. Other analyses prone to matrix interferences include pesticides, PCBs, and PAHs. Laboratory methodology has been developed to address the most common interferences, either through laboratory sample preparation or by adjusting instrument settings for specific sample matrices. If such procedures cannot completely eliminate an interference, the data will be qualified or the method detection limit will be elevated, and an explanation for the interference will be provided by the laboratory.

 

Author: Paul Berman, B.S - QA Officer/Staff Scientist

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