Determination of metals in soils and sewage sludges by ion chromatography and the effect of cropping systems on metal adsorption by soils

An accurate and precise ion chromatographic (IC) method for determination of total Cu, Ni, and Zn in soils was developed. The metals in soil digests were extracted with dithizone in CHCl[subscript]3, and the metal-dithizonate complexes were digested with HNO[subscript]3 before injection into the IC system. After separation on HPIC-CS5 column, the metals were determined by measuring the absorbance of metal complexes formed by postcolumn reaction with 4-(2-pyridylazo) resorcinol (PAR) at 520 nm. The results by this IC method agreed closely with those obtained by atomic absorption spectrophotometry (AA). Comparison of results of total Cu, Mn, Ni, Pb, and Zn with those obtained by AA showed that this method was accurate and precise for determination of metals in sewage sludges;The effect of cropping systems on adsorption of metals by soils was studied for two long-term rotation experiments, each having three crop rotations (continuous corn (CCCC), corn-soybean-corn-soybean, and corn-oats-meadow-meadow) and treatments with (+N) and without (O N) ammoniacal fertilizer. Results for soils under CCC rotations (+N) showed lower metal adsorption than those under CCCC (O N) and other crop rotations, which showed similar metal adsorption. Comparison of results obtained after adjusting the soil-solution pH with those for unadjusted solution pH showed that differences in metal adsorption by these soils were due to solution pH. Plots of the logarithm of the metal distribution coefficient (log K[subscript] d) vs. pH suggested competition of protons with metal ions for exchange sites. In general, proton coefficient values ( H[superscript]+/M[superscript]2+ ratios) followed the sequence: Pb \u3e Cu \u3e Cd = Ni = Zn. Calculated H[superscript]+/M[superscript]2+ ratios of Cu \u3e Ni ≥ Cd = Zn. Competition between metals for common adsorption sites was enhanced as the M[subscript]i increased

Ecological Risks from Agricultural Land Treated with Biosolids

Author Institution (Arvai and Basta): School of Environment and Natural Resources, The Ohio State University; Author Institution (Lanno): Department of Entomology, The Ohio State Universit

Online media scans: Applying systematic review techniques to assess statewide human papillomavirus vaccination activities

Background. Although the human papillomavirus (HPV) vaccine has been approved for use in adolescents in the US for over a decade, vaccination uptake remains low. Of concern, HPV vaccine coverage is below the national average in Minnesota, USA. To understand the reach of current HPV programming and research, we use an online media scan; this method may be applied to other jurisdictions to gain insight about various public health issues.Design and Methods. This online media scan describes the nature and scope of ongoing activities to increase HPV vaccination in Minnesota. The media scan included: a) structured internet searches of HPV vaccine health education/promotion activities ongoing in Minnesota since 2013, and b) searches in research databases of the published literature on HPV vaccination in Minnesota from 2013 to 2018. Results. Searches resulted in 880 online and 142 research article matches, with 40 and 36 meeting selection criteria. Results were categorized by activities focusing on race/ethnicity, sex, health providers, parents, lesbian, gay, bisexual, transgender and queer or questioning (LGBTQ) populations, geographic location, catchup vaccination, and insurance status. Most activities were statewide (52% health education/promotion and 35% research), followed by activities located in entirely urban areas (15% health education/promotion and 41% research) with only 6% of health education/promotion activities and 2% of research activities carried out in entirely rural areas.Conclusions. A range of local and statewide HPV vaccine health education/promotion and research activities were identified in Minnesota. Several efforts partnered with American Indian and Somali/Somali-American communities, but fewer activities focused on HPV vaccination among LGBTQ youth and HPV vaccination in rural areas

Bioaccessibility Tests Accurately Estimate Bioavailability Of Lead To Quail

Hazards of soil-borne lead (Pb) to wild birds may be more accurately quantified if the bioavailability of that Pb is known. To better understand the bioavailability of Pb to birds, the authors measured blood Pb concentrations in Japanese quail (Coturnix japonica) fed diets containing Pb-contaminated soils. Relative bioavailabilities were expressed by comparison with blood Pb concentrations in quail fed a Pb acetate reference diet. Diets containing soil from 5 Pb-contaminated Superfund sites had relative bioavailabilities from 33% to 63%, with a mean of approximately 50%. Treatment of 2 of the soils with phosphorus (P) significantly reduced the bioavailability of Pb. Bioaccessibility of Pb in the test soils was then measured in 6 in vitro tests and regressed on bioavailability: the relative bioavailability leaching procedure at pH 1.5, the same test conducted at pH 2.5, the Ohio State University in vitro gastrointestinal method, the urban soil bioaccessible lead test, the modified physiologically based extraction test, and the waterfowl physiologically based extraction test. All regressions had positive slopes. Based on criteria of slope and coefficient of determination, the relative bioavailability leaching procedure at pH 2.5 and Ohio State University in vitro gastrointestinal tests performed very well. Speciation by X-ray absorption spectroscopy demonstrated that, on average, most of the Pb in the sampled soils was sorbed to minerals (30%), bound to organic matter (24%), or present as Pb sulfate (18%). Additional Pb was associated with P (chloropyromorphite, hydroxypyromorphite, and tertiary Pb phosphate) and with Pb carbonates, leadhillite (a lead sulfate carbonate hydroxide), and Pb sulfide. The formation of chloropyromorphite reduced the bioavailability of Pb, and the amendment of Pb-contaminated soils with P may be a thermodynamically favored means to sequester Pb

Arsenic Metabolism by Human Gut Microbiota upon in Vitro Digestion of Contaminated Soils

BACKGROUND: Speciation analysis is essential when evaluating risks from arsenic (As) exposure. In an oral exposure scenario, the importance of presystemic metabolism by gut microorganisms has been evidenced with in vivo animal models and in vitro experiments with animal microbiota. However, it is unclear whether human microbiota display similar As metabolism, especially when present in a contaminated matrix. OBJECTIVES: We evaluated the metabolic potency of in vitro cultured human colon microbiota toward inorganic As (iAs) and As-contaminated soils. METHODS: A colon microbial community was cultured in a dynamic model of the human gut. These colon microbiota were incubated with iAs and with As-contaminated urban soils. We determined As speciation analysis using high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry. RESULTS: We found a high degree of methylation for colon digests both of iAs (10 mu g methylarsenical/g biomass/hr) and of As-contaminated soils (up to 28 mu g/g biomass/hr). Besides the formation of monomethylarsonic acid (MMA(V)), we detected the highly toxic monomethylarsonous acid (MMA(III)). Moreover, this is the first description of microbial thiolation leading to monomethylmonothioarsonic acid (MMMTA(V)). MMMTA(V), the toxicokinetic properties of which are not well known, was in many cases a major metabolite. CONCLUSIONS: Presystemic As metabolism is a significant process in the human body. Toxicokinetic studies aiming to completely elucidate the As metabolic pathway would therefore benefit from incorporating the metabolic potency of human gut microbiota. This will result in more accurate risk characterization associated with As exposures

Determination of metals in soils and sewage sludges by ion chromatography and the effect of cropping systems on metal adsorption by soils

An accurate and precise ion chromatographic (IC) method for determination of total Cu, Ni, and Zn in soils was developed. The metals in soil digests were extracted with dithizone in CHCl[subscript]3, and the metal-dithizonate complexes were digested with HNO[subscript]3 before injection into the IC system. After separation on HPIC-CS5 column, the metals were determined by measuring the absorbance of metal complexes formed by postcolumn reaction with 4-(2-pyridylazo) resorcinol (PAR) at 520 nm. The results by this IC method agreed closely with those obtained by atomic absorption spectrophotometry (AA). Comparison of results of total Cu, Mn, Ni, Pb, and Zn with those obtained by AA showed that this method was accurate and precise for determination of metals in sewage sludges;The effect of cropping systems on adsorption of metals by soils was studied for two long-term rotation experiments, each having three crop rotations (continuous corn (CCCC), corn-soybean-corn-soybean, and corn-oats-meadow-meadow) and treatments with (+N) and without (O N) ammoniacal fertilizer. Results for soils under CCC rotations (+N) showed lower metal adsorption than those under CCCC (O N) and other crop rotations, which showed similar metal adsorption. Comparison of results obtained after adjusting the soil-solution pH with those for unadjusted solution pH showed that differences in metal adsorption by these soils were due to solution pH. Plots of the logarithm of the metal distribution coefficient (log K[subscript] d) vs. pH suggested competition of protons with metal ions for exchange sites. In general, proton coefficient values ( H[superscript]+/M[superscript]2+ ratios) followed the sequence: Pb > Cu > Cd = Ni = Zn. Calculated H[superscript]+/M[superscript]2+ ratios of Cu > Ni ≥ Cd = Zn. Competition between metals for common adsorption sites was enhanced as the M[subscript]i increased.</p

Modifying Effect of Soil Properties on Bio-Accessibility of As and Pb from Human Ingestion of Contaminated Soil

Exposure to soils contaminated with heavy metals can pose human health risk to children through ingestion of contaminated soil. Soil properties such as soil pH, reactive Fe and Al oxide content, clay content, soil organic matter (SOM), and cation exchange capacity (CEC) can reduce contaminant bio-accessibility and exposure. In vitro bio-accessibility (%IVBA) of As and Pb in 19 soils was determined using U.S. EPA Method 1340. Soil properties reduced the bio-accessibility of As by 17–96.5% and 1.3–38.9% for Pb. For both As and Pb, bio-accessibility decreased with increasing Al and Fe oxide content. Al oxides were found to be the primary driver of As and Pb bio-accessibility. Multiple regressions with AlOx, soil pH, %clay and/or FeOx predicted %IVBA As (p &lt; 0.001). The multiple regression including log (FeOx + AlOx) and %clay explained 63% of the variability in %IVBA Pb (p &lt; 0.01). Fe and Al oxides were found to be important drivers of As and Pb bio-accessibility, regardless of in vitro method. These findings suggested soil pH should be used in addition to reactive oxides to predict bio-accessible As. Risk-based adjustments using soil properties for exposure via incidental ingestion should be considered for soils contaminated with As and/or Pb

What is required for the validation of in vitro assays for predicting contaminant relative bioavailability? Considerations and criteria

A number of studies have shown the potential of in vitro assays to predict contaminant in vivo relative bioavailability in order to refine human health exposure assessment. Although the term ‘validated’ has been used to describe the goodness of fit between in vivo and in vitro observations, its misuse has arisen from semantic considerations in addition to the lack of defined criteria for establishing performance validation. While several internal validation methods may be utilised, performance validation should preferably focus on assessing the agreement of model predictions with a set of data which are independent of those used to construct the model. In order to achieve robust validated predictive models, a number of parameters (e.g. size of data set, source of independent soils, contaminant concentration range, animal model, relative bioavailability endpoint) need to be considered in addition to defined criteria for establishing performance validation which are currently lacking.