Natural Organic Matter Characterization and Lead Speciation as Indicators of Potential Lead Bioavailability in Aquatic Environments

Trace metals and natural organic matter (NOM) are ubiquitous in aquatic environments. Some trace metals are essential for aquatic life, while other non-essential metals (like lead) can be toxic if present in great enough concentrations. Natural waters contain a combination of inorganic, and organic ligands capable of binding metals. While the chemistry of inorganic Pb species is well understood, and National Institute of Standards and Technology (NIST) certified K values are readily available, the interactions between metals and organic matter is not so clearly defined. It is important to understand how NOM interacts with metals in the environment, as the properties of NOM vary with source. If these differences in NOM chemistry induce source-dependent Pb binding, the industrial and environmental implications would be significant. This study aimed to characterize a variety of NOM sources of diverse origin, measure Pb speciation in order to determine if Pb-NOM binding is indeed source-dependent, and to determine which property/ies would best explain Pb-NOM binding. NOM sources were characterized using: total organic carbon/dissolved organic carbon (TOC/DOC), fluorescence excitation-emission matrices (FEEM), parallel factor analysis (PARAFAC), fluorescence index (FI), specific absorption coefficient (SAC340), chromium-reducible sulfide (CRS), thiol, dissolved organic nitrogen (DON), and proton binding index (PBI). These methods allowed for a quantification of organic carbon; humic acid-, fulvic acid-, tyrosine-, and tryptophan-like components; origin; aromaticity; sulfide ligands; nitrogen ligands; and oxygen ligands. SAC340, FI, %HA, %FA, %Trp, %Tyr, CRS, thiol, DON, and PBI values ranged from: 7.76 – 40.84, 1.04 – 1.84, 46.41 – 82.41%, 13.32 – 39.21%, 1.02 – 16.21%, 1.34 – 14.99%, 2.03 – 89.0 nmol/mgC, 71.8 – 186.5 nmol/mgC, 35.76 – 253.8 μgN/mgC, and 0.33 – 1.72 respectively. No one parameter, or simple series of parameters was able to discriminate NOM source. However, CRS, Trp, and Tyr may be able to discriminate saltwater from freshwater sources, while SAC340, CRS, thiol, DON, Trp, Tyr, and PBI may be able to discriminate between freshwater sources. Sources of terrestrial origin had significant SAC340 and PBI, while sources of microbial origin had significant CRS, DON, Trp, and Tyr. Free lead was then measured using flow-through titrations with a commercially available Pb ion-selective electrode (ISE) and an internal calibration method. To confirm that this method was applicable for trace-level analysis in NOM, ethylenediamine (EN) was used as a model ligand in both artificial freshwater (AFW) and artificial seawater (ASW), and the speciation modelled using certified logK values from NIST. In both AFW and ASW, the ISE accurately and reproducibly (within a factor of two) measured Pb2+ speciation with EN as a model ligand. However, when this method was applied to speciation measurement in NOM, measured values did not agree well with WHAM. This indicates that the fundamental assumption (that Pb-NOM binding will not occur at low pH) made by the internal calibration method is not effective at predicting speciation in NOM, as WHAM predicts that Pb-NOM binding will occur at low pH. An alternate calibration method was tested – forcing measured values to agree with WHAM at low pH – and gave much better agreement. However, speciation measurements in NOM demonstrated reproducible variation with source(indicating source-dependent Pb-NOM binding) which was not described by WHAM within a factor of two, regardless of the calibration method. DON and SAC340 for the titrated sources are significantly different, and may potentially explain differences in source-dependent Pb speciation in freshwater environments. This is of immense industrial and environmental importance, as current water quality guidelines (WQG) do not account for NOM, DON, or SAC340. Consequently, current guidelines could overestimate toxicity in highly aromatic sources, or underestimate toxicity in sources with high DON

River Run Red: The Fort Pillow Massacre in the American Civil War

Civil War Atrocity Nathan B. Forrest raid on Fort Pillow Andrew Ward is a professional writer whose previous works included Fits and Starts: The Premature Memoirs of Andrew Ward; The Blood Seed: A Novel of India; Our Bones Are Scattered: The Cawnpore Massacres in the Indian ...

The Civil War and the Limits of Destruction

The Destructive War? Mark E. Neely, Jr., McCabe-Greer Professor of the History of the Civil War Era at Pennsylvania State University, has written numerous books, primarily on political, cultural, and legal aspects of the period. As a senior figure in the field, he has unquestionably read e...

Effects of Weather on Autumn Hawk Movements at Fort Morgan, Alabama

Migrating hawks were observed at Fort Morgan, Alabama during autumn 1995-1998. The three most abundant migrants were Sharp-shinned Hawk (Accipiter striatus), Broad-winged Hawk (Buteo platypterus) and American Kestrel (Falco sparverius). The three species accounted for 84% of all observations. Most individuals (\u3e 80%) were seen heading west. Compared with days with east and south winds, days with north winds were associated with significantly higher passage rates for all species, and passage rates of Broadwinged Hawks were significantly higher on days when both a cold front and north winds occurred than on days with north winds only. Hawks flew higher on east winds than on north and south winds, suggesting that hawks fly lower in winds that may blow them out over the Gulf of Mexico

The Attentional Function Index—a self-report cognitive measure

Objective : Cognitive assessment in individuals with cancer requires both measured performance on neuropsychological tests and self-report of effectiveness in functioning. Few instruments are available to assess the perceived impact of cognitive alterations on daily functioning in individuals treated for cancer. In this study, we investigated the psychometric properties of a theoretically based instrument, and the Attentional Function Index (AFI), designed to measure perceived effectiveness in common activities requiring attention and working memory, particularly the ability to formulate plans, carry out tasks, and function effectively in daily life. Methods : Women ( N =172), ages 27–86 years, completed the questionnaire before primary treatment for early stage breast cancer. Construct validity was established using exploratory principal component factor analysis with varimax rotation. Results : A 13-item instrument emerged with 3 subscales, namely effective action, attentional lapses, and interpersonal effectiveness, which explained 74.69% of total variance. The internal consistency coefficients (Cronbach's α ) were 0.92 for the total instrument, and ranged from 0.80 to 0.92 for the 3 subscales. Further examination of validity indicated that the scores on the AFI (1) showed expected correlations with established measures of ability to concentrate, cognitive failures, states of confusion, and mental fatigue, and (2) could distinguish differences in perceived cognitive functioning between younger and older age groups. AFI scores were not significantly associated with years of education or presence of comorbid conditions. Conclusion : The brief AFI has demonstrated usefulness for assessment of perceived cognitive functioning in populations with life-threatening and chronic illness, such as breast cancer. Copyright © 2010 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79422/1/1729_ftp.pd

Helen Keating

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Noctor

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Mideast of the Briar Patch

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Evan Shelby, born 1828

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