Poultry litter is a mixture of excreta, feed, feathers, and bedding material. Poultry litter is useful as a fertilizer due to the presence of nitrogen, phosphorus, and potassium. Litter is commonly used for growing corn, soybeans, potatoes, tomatoes, leafy vegetables, and cover crops. The aqueous leachate of poultry litter has been shown to exhibit toxicity to a variety of indicator organisms. The objective of this research was to identify classes of toxicants in the litter aqueous leachate. The aqueous extract of poultry litter was subjected to toxicity identification tests approved by the United States Environmental Protection Agency that use Ceriodaphnia dubia as the test organism. Tests performed included pH adjustment, filtration, aeration, C18 solid-phase extraction, EDTA addition, sodium thiosulfate addition, and extraction through zeolite. Zeolite extraction, filtration at low pH, and aeration at low pH reduced overall toxicity by 68, 20, and 22%, respectively. The major sources of toxicity appear to be ammonia and anionic organic compounds. Toxicity was apparently not due to the presence of heavy metals or oxidants.
Although most researches with non-essential metals (NEMs) have been done with single or individual metals, in reality, organisms are often exposed to multiple contaminants at the same time through the air, food and water. In this study, we tested the toxicity of four NEMs, As, Cd, Pb, and Hg, individually and as a composite mixture using the microtox bioassay. This assay uses the reduction of bioluminescence of the bacterium Vibrio fischeri as a measure of toxicity. The concentrations of each chemical in the mixture were based on multiples of their maximum contaminant levels (MCLs) set by the U.S. EPA. The highest concentration of exposure was 20 times the MCL, which translated into 200, 100, 40 and 300 ppb for As, Cd, Hg and Pb, respectively. The ratio for the mixture from these concentrations was 10:5:2:15 for As, Cd, Hg and Pb, respectively. Among the individual metals tested, the ranking of toxicity was Hg>Pb>Cd>As based on the EC50 values of 109, 455, 508 and 768 ppb for Hg, Pb, Cd and As, respectively. The EC50 for the composite mixture was 495% MCL which translated into nominal concentrations of 49, 25, 10 and 74 ppb for As, Cd, Hg, and Pb, respectively. Overall, the EC50 value of each NEM within the mixture was lower than the EC50 of the individual chemical; an evidence of synergism for the mixture. The individual toxic units (TU) were 0.06, 0.05, 0.09, and 0.16 for As, Cd Hg, and Pb, respectively and the summed toxic unit (TU) was 0.37 (less than 1). This study provides needed scientific data necessary for carrying out complete risk assessment of As, Cd, Hg, and Pb mixtures of some priority compounds.
Dinitrotoluenes (DNTs) are nitroaromatic compounds appearing as pale yellow crystalline solids at room temperature. Dinitrotoluenes exist as a mixture of 2 to 6 isomers, with 2,4-DNT, and 2,6-DNT being the most significant. About 500 persons are estimated to be potentially exposed yearly to 2,4-DNT and 2,6-DNT during the production of munitions and explosives. The main route of human exposure at ammunition facilities is inhalation, but dermal contact and inadvertent ingestion can also be substantial. In factory workers, exposure to DNTs has been linked to many adverse health effects, including cyanosis, vertigo, headache, metallic taste, dyspnea, weakness and lassitude, loss of appetite, nausea, and vomiting. Other symptoms including pain or parasthesia in extremities, abdominal discomfort, tremors, paralysis, chest pain, and unconsciousness have also been reported. The primary targets of DNT toxicity are the hematopoietic system (pallor, cyanosis, anemia, and leukocytosis), the cardiovascular system (ischemic heart disease), the nervous system (muscular weakness, headache, dizziness, nausea, insomnia, and tingling pains in the extremities) and the reproductive system (reduction of sperm counts, alteration of sperm morphology, and aspermatogenesis). An association between DNT exposure and increased risk of hepatocellular carcinomas and subcutaneous tumors in rats, as well as renal tumors in mice, has been established. Epidemiologic studies of DNT toxicity have been limited to small groups of workers who had been occupationally exposed at various ammunitions production facilities. Clearly defining the health effects of DNTs with a high degree of confidence has therefore been difficult because of the multigenic nature of occupational exposure. In an attempt to update the toxicologic profile of the DNTs, we hereby provide a critical review of the environmental and toxicologic pathology of DNTs, with a special emphasis on their potential implications for public health.
A new method for preparing black birnessite nanoparticles is introduced. The initial synthesis process resembles the classical McKenzie method of preparing brown birnessite except for slower cooling and closing the system from the ambient air. Subsequent process, including wet-aging at7∘Cfor 48 hours, overnight freezing, and lyophilization, is shown to convert the brown birnessite into black birnessite with complex nanomorphology with folded sheets and spirals. Characterization of the product is performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), andN2adsorption (BET) techniques. Wet-aging and lyophilization times are shown to affect the architecture of the product. XRD patterns show a single phase corresponding to a semicrystalline birnessite-based manganese oxide. TEM studies suggest its fibrous and petal-like structures. The HRTEM images at 5 and 10 nm length scales reveal the fibrils in folding sheets and also show filamentary breaks. The BET surface area of this nanomaterial was found to be 10.6 m2/g. The TGA measurement demonstrated that it possessed an excellent thermal stability up to400∘C. Layer-structured black birnessite nanomaterial containing sheets, spirals, and filamentary breaks can be produced at low temperature (−49∘C) from brown birnessite without the use of cross-linking reagents.
The effect of Hoffmeister anions , , and on the structure and morphology of birnessite and cryptomelane-type manganese dioxide nanostructures, produced by the reduction reaction of and in aqueous acidic media, was studied. The syntheses were based on the decomposition of aqueous in presence of HCl for birnessite-type and acidified for cryptomelane-type manganese dioxide under soft hydrothermal conditions. They were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) techniques. XRD patterns show the formation of birnessite for the first synthesis and a mixture of cryptomelane and birnessite-types for the second synthesis. XRD data revealed that the Hoffmeister anions have a significant effect on the nanostructures of birnessite. The sulphate ion-treated birnessite has the smallest crystals, whereas the chloride ion-treated birnessite has the largest crystals. Their TEM and HRTEM studies revealed a transformation from nanoplatelet morphology for chloride-treated samples to nanofibrous morphology for sulphate-treated birnessite. For the cryptomelane nanostructures, Hoffmeister anions also show a profound effect on their crystalline structures as determined by XRD analyses revealing a transformation of the cryptomelane phase to birnessite phase of . This transformation is also supported by TEM and HRTEM studies.
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