Gravitational friction from d'Alembert's principle.

The least action principle played a central role in the development of modern physics. A major drawback of the principle is that its applicability is limited to holonomic constraints. In the present work, we investigate the energy lost by particles as a result of the gravitational interaction in a homogeneous low-density medium subject to non-holonomic constraints. We perform the calculation for an arbitrary particle and outline the specific result for photons. The energy lost is calculated from first principles based on the principle of virtual work and the d'Alembert principle. Under the formalism mentioned above, the dissipative nature of the effect is established. Furthermore, we show that the results agree with an alternative derivation based on continuum mechanics and the Euler-Cauchy stress principle.

Influence of flow on phosphorus-dynamics and particle size in agricultural drainage ditch sediments.

Particle size is one factor affecting phosphorus (P) dynamics in soils and sediments. This study investigated how flow facilitated by hydraulic pumps and aquatic vegetation species water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes) affected particle size and P-dynamics in organic sediments in agricultural drainage ditches. Sediments with finer particle size (>0.002 mm) were hypothesized to contain greater total P (TP) and less labile P than sediments with coarser particle size. Particle size was determined using a LS 13 320 Laser Diffraction Particle Size Analyzer. Sediments were tested for pH, TP, and organic matter. Fractions of P were determined using a sequential fractionation experiment and 31P Nuclear Magnetic Resonance (NMR) Spectroscopy. Larger average particle size and lower average total P concentrations were found in the inflows of the field ditches compared to the outflows. Presence of flow and aquatic vegetation did not have a significant impact on particle size, TP, or labile P fractions. Median (p = 0.10) particle size was not significantly correlated to TP. Overall, there was an average trend of coarser particle size and lower P concentrations in the inflow compared to the outflow. The presence of inorganic limerock could have affected results due to increased P adsorption capacity and larger average particle size compared to the organic fraction of the sediment.

Adsorption and oxidation of 3-nitro-1,2,4-triazole-5-one (NTO) and its transformation product (3-amino-1,2,4-triazole-5-one, ATO) at ferrihydrite and birnessite surfaces.

The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently being used to replace conventional explosives such as 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), but the environmental fate of this increasingly widespread IMC remains poorly understood. Upon release from unexploded solid phase ordinances, NTO exhibits high aqueous solubility and, hence, potential mobilization to groundwater. Adsorption and abiotic transformation at metal oxide surfaces are possible mechanisms for natural attenuation. Here, the reactions at ferrihydrite and birnessite surfaces of NTO and its biotransformation product, 3-amino-1, 2, 4-triazol-5-one (ATO), were studied in stirred batch reactor systems at controlled pH (7.0). The study was carried out at metal oxide solid to solution ratios (SSR) of 0.15, 1.5 and 15 g kg-1. The samples were collected at various time intervals up to 3 h after reaction initiation, and analyzed using HPLC with photodiode array and mass spectrometric detection. We found no detectable adsorption or transformation of NTO upon reaction with birnessite, whereas ATO was highly susceptible to oxidation by the same mineral, showing nearly complete transformation within 5 min at 15 g kg-1 SSR to urea, CO2(g) and N2(g). The mean surface-area-normalized pseudo-first order rate constant (k) for ATO oxidation by birnessite across all SSRs was 0.05 ±â€¯0.022 h-1 m-2, and oxidation kinetics were independent of dissolved O2 concentration. Both NTO and ATO were resistant to oxidation by ferrihydrite. However, NTO showed partial removal from solution upon reaction with ferrihydrite at 0.15 and 1.5 g kg-1 SSR and complete loss at 15 g kg-1 SSR due to strong adsorption. Conversely, ATO adsorption to ferrihydrite was much weaker than that measured for NTO.

Oxidation of reduced daughter products from 2,4-dinitroanisole (DNAN) by Mn(IV) and Fe(III) oxides.

Abiotic transformation of anthropogenic compounds by redox-active metal oxides affects contaminant fate in soil. The capacity of birnessite and ferrihydrite to oxidize the insensitive munitions compound, 2,4-dinitroanisol (DNAN), and its amine-containing daughter products, 2-methoxy-5-nitro aniline (MENA) and 2,4-diaminoanisole (DAAN), was studied in stirred reactors at controlled pH (7.0). Aqueous suspensions were reacted at metal oxide solid to solution mass ratios (SSR) of 0.15, 1.5 and 15 g kg-1 and solutions were analyzed after 0-3 h by high performance liquid chromatography coupled with photodiode array or mass spectrometry detection. Results indicate that DNAN was resistant to oxidation by birnessite and ferrihydrite. Ferrihydrite did not oxidize MENA, but MENA was susceptible to rapid oxidation by birnessite, with nitrogen largely mineralized to nitrite. This is the first report on mineralization of nonphenolic aromatics and the release of mineralized N from aromatic amines following reaction with birnessite. DAAN was oxidized by both solids, but ca. ten times higher rate was observed with birnessite as compared to ferrihydrite at an SSR of 1.5 g kg-1. At 15 g kg-1 SSR, DAAN was removed from solution within 5 min of reaction with birnessite. CO2(g) evolution experiments indicate mineralization of 15 and 12% of the carbon associated with MENA and DAAN, respectively, under oxic conditions with birnessite at SSR of 15 g kg-1. The results taken as a whole indicate that initial reductive (bio)transformation products of DNAN are readily oxidized by birnessite. The oxidizability of the reduced DNAN products was increased with progressive (bio)reduction as reflected by impacts on the oxidation rate.

(Bio)transformation of 2,4-dinitroanisole (DNAN) in soils.

Recent studies have begun to assess the environmental fate and toxicity of 2,4-dinitroanisole (DNAN), an insensitive munition compound of interest to defense agencies. Aerobic and anaerobic DNAN biotransformation in soils was evaluated in this study. Under aerobic conditions, there was little evidence of transformation; most observed removal was attributed to adsorption and subsequent slow chemical reactions. Under anaerobic conditions, DNAN was reductively (bio)transformed and the rate of the transformation was positively correlated with soil organic carbon (OC) up to a threshold of 2.07% OC. H2 addition enhanced the nitroreduction rate compared to endogenous treatments lacking H2. Heat-killed treatments provided rates similar to the endogenous treatment, suggesting that abiotic factors play a role in DNAN reduction. Ten (bio)transformation products were detected by high-resolution mass spectrometry. The proposed transformation pathway involves reduction of DNAN to aromatic amines, with putative reactive nitroso-intermediates coupling with the amines to form azo dimers. Secondary reactions include N-alkyl substitution, O-demethylation (sometimes followed by dehydroxylation), and removal of an N-containing group. Globally, our results suggest that the main reaction DNAN undergoes in anaerobic soils is nitroreduction to 2-methoxy-5-nitroaniline (MENA) and 2,4-diaminoanisole (DAAN), followed by anaerobic coupling reactions yielding azo-dimers. The dimers were subsequently subject to further (bio)transformations.

Biotransformation and Degradation of the Insensitive Munitions Compound, 3-Nitro-1,2,4-triazol-5-one, by Soil Bacterial Communities.

Insensitive munitions (IM) are a new class of explosives that are increasingly being adopted by the military. The ability of soil microbial communities to degrade IMs is relatively unknown. In this study, microbial communities from a wide range of soils were tested in microcosms for their ability to degrade the IM, 3-nitro-1,2,4-triazol-5-one (NTO). All seven soil inocula tested were able to readily reduce NTO to 3-amino-1,2,4-triazol-5-one (ATO) via 3-hydroxyamino-1,2,4-triazol-5-one (HTO), under anaerobic conditions with H2 as an electron donor. Numerous other electron donors were shown to be suitable for NTO-reducing bacteria. The addition of a small amount of yeast extract (10 mg/L) was critical to diminish lag times and increased the biotransformation rate of NTO in nearly all cases indicating yeast extract provided important nutrients for NTO-reducing bacteria. The main biotransformation product, ATO, was degradable only in aerobic conditions, as evidenced by a rise in the inorganic nitrogen species nitrite and nitrate, indicative of nitrogen-mineralization. NTO was nonbiodegradable in aerobic microcosms with all soil inocula.

Cobalt distribution and speciation: effect of aging, intermittent submergence, in situ rice roots.

The speciation and distribution of Co in soils is poorly understood. This study was conducted using x-ray absorption spectroscopy (XAS) techniques to examine the influence of soluble cobalt in the +2 oxidation state (Co[II]) aging, submergence-dried cycling, and the presence of in vivo rice roots on the speciation and distribution of added Co(II) in soils. In the aging and submerged-dried cycling studies, Co was found to be associated with Mn oxide fraction (23 to 100% of total Co) and Fe oxide fractions (0 to 77% of total Co) of the soils as either Co(II) species or a mixed Co(II), and Co in the +3 oxidation state (Co[III]) species. The surface speciation of Co in the Mn oxide fraction suggests an innersphere complex was present and the speciation of Co in the Fe oxide fraction was an innersphere surface complex. The in vivo root box experiments showed similar Co speciation in the Mn oxide fraction (13 to 76% of total Co) as the aging and submerged-dried cycling studies. However, the Fe oxide fraction of the soil was unimportant in Co retention. A significant amount (24 to 87% of total Co) of the Co in root box treatments was identified as a Co precipitate. The importance of this finding is that in the presence of rice roots, the Co is redistributed to a Co precipitate. This work confirmed earlier macroscopic work that Mn oxides are important in the sequestration of Co in soils and the influence of roots needs to be taken into account when addressing Co speciation. The information gained from this study will be used to improve models to predict the lability and hence the availability of Co in terrestrial environments.