Relating pollutant and water quality parameters to landuse in a subwatershed in the Choptank River watershed

Agriculture and animal feeding operations have been implicated as sources of water pollution along the Choptank River, an estuary and tributary of the Chesapeake Bay. This survey examined a subwatershed within the Choptank River watershed for impacts of a poultry facility on its adjacent surface water. Water and sediment samples were collected May - October 2009 under mostly baseflow conditions and analyzed for antibiotics, nutrients, heavy metals, and selected bacteria. Of the antibiotics recovered, no significant difference was observed spatially, but a significant difference emerged between spring and fall/winter. For nutrients, the greatest phosphorus concentrations were at the subwatershed outlet (4) and at two branches not containing the poultry house (3 and 5); nitrogen concentrations at sites 2 and 5 were as high as site 4. Arsenic concentrations at 2 were lower than both the low-agriculture (control) site and a site neighboring 3. Bacterial counts in water and sediment remained fairly constant throughout the sampling regime

EFFECTS OF LIVESTOCK ANTIBIOTICS ON NITRIFICATION, DENITRIFICATION, AND MICROBIAL COMMUNITY COMPOSITON IN SOILS ALONG A TOPOGRAPHIC GRADIENT

Several types of antibiotics (roxarsone, virginiamycin, and bacitracin) are widely included in poultry feed to improve animal growth yields. Most of the antibiotics are excreted in manure which is subsequently applied to soils. One concern with this practice is that antibiotics may affect several microbially-mediated nutrient cycling reactions in soils that influence crop productivity and water quality. The main objectives of this study were to determine the effects of livestock antibiotics on nitrification, denitrification, and microbial community composition in soils along a topographic gradient. These objectives were addressed in a series of lab experiments by monitoring changes in inorganic N species and ester-linked fatty acid methyl ester profiles after exposing soil microorganisms collected from different topographic positions to increasing levels of antibiotics. It was discovered that roxarsone and virginiamycin inhibited nitrification and soil microbial growth and also influenced microbial community composition, but only at levels that were much higher than expected in poultry litter-applied soils. Bacitracin did not affect nitrification, microbial growth, or microbial community composition at any concentration tested. None of the antibiotics had a strong affect on denitrification. Thus, it is unlikely that soil, water, or air quality would be significantly impacted by the antibiotics contained in poultry litter

Arsenic Contamination in Groundwater in Vietnam: An Overview and Analysis of the Historical, Cultural, Economic, and Political Parameters in the Success of Various Mitigation Options

Although arsenic is naturally present in the environment, 99% of human exposure to arsenic is through ingestion. Throughout history, arsenic is known as “the king of poisons”; it is mutagenic, carcinogenic, and teratogenic. Even in smaller concentrations, it accumulates in the body and takes decades before any physical symptoms of arsenic poisoning shows. According to the World Health Organization (WHO), the safe concentration of arsenic in drinking water is 10 µg/L. However, this limit is often times ignored until it is decades too late and people begin showing symptoms of having been poisoned. This is the current situation for Vietnam, whose legal arsenic concentration limit is 50 µg/L, five times higher than the WHO guidelines. Groundwater in Vietnam was already naturally high in arsenic due to arsenic-rich soils releasing arsenic into groundwater. Then, in the past half century, with the use of arsenic-laden herbicides dispersed during the Vietnam War and subsequent industrial developments, the levels of bio-available arsenicals has dangerously spiked. With the proliferation of government-subsidized shallow tube-wells in the past two decades, shallow groundwater has become the primary source for drinking and irrigation water in Vietnam. This is a frightening trend, because this groundwater has arsenic concentrations up to 3050 µg/L, primarily in the +3 and +5 oxidation states, the most readily available oxidation states for bioaccumulation. This thesis argues that measures must be taken immediately to remedy the high concentration of arsenic in groundwater, which in Vietnam is the primary and, in some cases, the sole source of water for domestic consumption and agricultural production. Although there are numerous technologies available for treating arsenic in groundwater, not all of them are suited for Vietnam. By analyzing the historical, cultural, economic, and political parameters of Vietnam, several optimal treatments of groundwater for drinking water emerged as most recommended, a classification that is based on their local suitability, social acceptability, financial feasibility, and governmental support. Further research on irrigation water treatment is proposed due to the need for sustainable crop production, the safe ingestion of rice and vegetables, and the continued growth of Vietnam’s economy, which is heavily dependent on agriculture

Biochemical characterization of ArsI: a novel C-As lyase for degradation of environmental organoarsenicals

Organoarsenicals such as methylarsenical methylarsenate (MAs(V)) and aromatic arsenicals including roxarsone (4-hydroxy-3-nitrophenylarsenate or Rox(V)) have been extensively used as an herbicide and growth enhancers in animal husbandry, respectively. They undergo environmental degradation to more toxic inorganic arsenite (As(III)) that contaminates crops and drinking water. We previously identified a bacterial gene (arsI) responsible for aerobic MAs(III) demethylation. The gene product, ArsI, is a Fe(II)-dependent extradiol dioxygenase that cleaves the carbon-arsenic (C-As) bond in MAs(III) and trivalent aromatic arsenicals. The objective of this study was to elucidate the ArsI mechanism. Using isothermal titration calorimetry, we determined the dissociation constants (Kd) and ligand-to-protein stoichiometries (N) of ArsI for Fe(II), MAs(III) and aromatic phenyl arsenite. Using a combination of methods including chemical modification, site-directed mutagenesis, and fluorescent spectroscopy, we demonstrated that amino acid residues predicted to participate in Fe(II)-binding (His5-His62-Glu115) and substrate binding (Cys96-Cys97) are all involved in catalysis. Finally, the products of Rox(III) degradation were identified as As(III) and 4-hydroxy-2-nitrophenol, demonstrating that ArsI is a dioxygenase that incorporates one oxygen atom from dioxygen into the carbon and the other to the arsenic to catalyze the cleavage of the C-As bond. These results augment our understanding of the mechanism of this novel C-As lyase

Risk assessment of the use of alternative animal and plant raw material resources in aquaculture feeds

A wide range of raw materials are now used routinely in aquaculture feeds throughout the world, primarily to supply protein and energy in the form of lipid from edible oils. Protein meals and oils used can generally be divided into those of plant or animal origin and many have considerable potential to supply the required dietary nutrients required by aquaculture species. However, the use of any raw material introduces a suite of risks that need to be considered to enable the production of safe, sustainable and functional feeds to underpin this sector. A lack of understanding of some of those risks can result in failure of dietary specifications being met and/or negative nutritional elements being introduced (e.g. antinutritional factors). Importantly, it is this feed that when fed to food‐producing animals is such an important element of food safety, and as such any undesirable aspects relating to feed production can also have a negative impact on the rest of the food chain. However, there is some disparity internationally among raw materials that are used and the perceptions surrounding the risk of their use. It is the scientific assessment of these risks that is the basis of this review

Distribution of Heavy Metals from Flue Gas in Algal Bioreactor

Algae are microscopic organisms with a great potential to produce biomass and lipids at productivities several times higher than terrestrial crops. To grow, these organisms consume carbon dioxide (CO2), a greenhouse gas. This gas, emitted primarily by power plants after coal burning, can be effectively used for algae production, thus resulting in CO2 remediation and biomass beneficial utilization as feedstuff, industrial filler and biodiesel feedstock. However, since coal is a fuel mined from the earth’s crust, it contains heavy metals that are released during coal burning and inevitably enter the algal cultivation system, contaminating the water were algae is grown, the algal biomass and the products derived from such biomass. The distribution of heavy metals from flue gas in algal cultivation systems is unknown, yet necessary to advance this industry. This study focused on quantifying the distribution and effects that ten coal-derived heavy metals (Cu, Co, Zn, Pb, As, Se, Cr, Hg, Ni and Cd) will have on algae strain Scenedesmus obliquus and on the potential products derived from this algae