Mobilisation of arsenic from bauxite residue (red mud) affected soils: effect of pH and redox conditions

The tailings dam breach at the Ajka alumina plant, western Hungary in 2010 introduced ~1 million m3 of red mud suspension into the surrounding area. Red mud (fine fraction bauxite residue) has a characteristically alkaline pH and contains several potentially toxic elements, including arsenic. Aerobic and anaerobic batch experiments were prepared using soils from near Ajka in order to investigate the effects of red mud addition on soil biogeochemistry and arsenic mobility in soil–water experiments representative of land affected by the red mud spill. XAS analysis showed that As was present in the red mud as As(V) in the form of arsenate. The remobilisation of red mud associated arsenate was highly pH dependent and the addition of phosphate to red mud suspensions greatly enhanced As release to solution. In aerobic batch experiments, where red mud was mixed with soils, As release to solution was highly dependent on pH. Carbonation of these alkaline solutions by dissolution of atmospheric CO2 reduced pH, which resulted in a decrease of aqueous As concentrations over time. However, this did not result in complete removal of aqueous As in any of the experiments. Carbonation did not occur in anaerobic experiments and pH remained high. Aqueous As concentrations initially increased in all the anaerobic red mud amended experiments, and then remained relatively constant as the systems became more reducing, both XANES and HPLC–ICP-MS showed that no As reduction processes occurred and that only As(V) species were present. These experiments show that there is the potential for increased As mobility in soil–water systems affected by red mud addition under both aerobic and anaerobic conditions

Polyphosphates as a source of enhanced P fluxes in marine sediments overlain by anoxic waters: Evidence from (31)P NMR

Sedimentary phosphorus (P) composition was investigated in Effingham Inlet, a fjord located on the west coast of Vancouver Island in Barkley Sound. Solid-state (31)P nuclear magnetic resonance (NMR) spectroscopy was applied to demineralized sediment samples from sites overlain by oxic and anoxic bottom waters. The two sites were similar in terms of key diagenetic parameters, including the mass accumulation rate, integrated sulfate reduction rate, and bulk sediment organic carbon content. In contrast, P benthic fluxes were much higher at the anoxic site. (31)P NMR results show that P esters and phosphonates are the major organic P species present at the surface and at depth in sediments at both sites. Polyphosphates were only found in the surface sediment of the site overlain by oxic waters. The varying stability of polyphosphates in microorganisms under different redox conditions may, in part, explain their distribution as well as differences in P flux between the two sites

Biogeochemical Stoichiometry of Antarctic Dry Valley Ecosystems

Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in proportions far above or below ratios necessary to support balanced microbial growth. This polar desert provides an opportunity to evaluate stoichiometric approaches to understand nutrient cycling in an ecosystem where biological diversity and activity are low, and controls over the movement and mass balances of nutrients operate over 10–10⁶ years. The simple organisms (microbial and metazoan) comprising dry valley foodwebs adhere to strict biochemical requirements in the composition of their biomass, and when activated by availability of liquid water, they influence the chemical composition of their environment according to these ratios. Nitrogen and phosphorus varied significantly in terrestrial and aquatic ecosystems occurring on landscape surfaces across a wide range of exposure ages, indicating strong influences of landscape development and geochemistry on nutrient availability. Biota control the elemental ratio of stream waters, while geochemical stoichiometry (e.g., weathering, atmospheric deposition) evidently limits the distribution of soil invertebrates. We present a conceptual model describing transformations across dry valley landscapes facilitated by exchanges of liquid water and biotic processing of dissolved nutrients. We conclude that contemporary ecosystem stoichiometry of Antarctic Dry Valley soils, glaciers, streams, and lakes results from a combination of extant biological processes superimposed on a legacy of landscape processes and previous climates

Historical changes in sediments of Pyramid Lake, Nevada, USA: consequences of changes in the water balance of a terminal desert lake

Sediment cores from the shallow and deep basins of Pyramid Lake, Nevada, revealed variations in composition with depth reflecting changes in lake level, river inflow, and lake productivity. Recent sediments from the period of historical record indicate: (1) CaCO 3 and organic content of sediment in the shallow basin decrease at lower lake level, (2) CaCO 3 content of deep basin sediments increases when lake level decreases rapidly, and (3) the inorganic P content of sediments increases with decreasing lake volume. Variations in sediment composition also indicate several periods for which productivity in Pyramid Lake may have been elevated over the past 1000 years. Our data provide strong evidence for increased productivity during the first half of the 20th Century, although the typical pattern for cultural eutrophication was not observed. The organic content of sediments also suggests periods of increased productivity in the lake prior to the discovery and development of the region by white settlers. Indeed, a broad peak in organic fractions during the 1800's originates as an increase starting around 1600. However, periods of changing organic content of sediments also correspond to periods when inflow to the lake was probably at extremes (e.g. drought or flood) indicating that fluctuations in river inflow may be an important factor affecting sediment composition in Pyramid Lake.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43069/1/10933_2004_Article_BF00678089.pd

The effect of free or restricted acidified milk feeding of Finnish Ayrshire bull calves on the subsequent fattening and slaughter performance

The aim of the research was to study whether the anticipated added weight gain from ad libitum acidified milk feeding compared to restricted milk feeding during the preweaning period can be maintained after weaning until slaughter. The study was conducted by comparing first the growth performance of eleven bull calves until an average age of 126 days (Phase 1) when the five calves were fed acidified milk either ad libitum (FM) for 17 weeks or when six calves were given acidified milk restrictively (5 l per day, RM) for nine weeks. Bulls had ad libitum access to grass silage and concentrate. Secondly, the performance of bulls having an average age of 175 days until slaughter (at an average age of 429 days) at a carcass weight of approximately 290 kg was assessed (Phase 2). All animals were fed grass silage ad libitum and concentrate at a level of 620 g kg-1 of dietary dry matter. Calves fed acidified milk ad libitum grew significantly (P < 0.01) faster than those fed restrictively during the first nine weeks of Phase 1 (1003 vs. 725 g per day). The bulls in the RM group grew a little but not significantly faster during Phase 2, the growth rates being 1197 vs. 1207 g per day. The feed conversion, weight (535 vs. 533 kg at slaughter) and slaughter results were equal. Similarly the life-time gains did not differ being 1174 (FM) and 1141 (RM) g per day, respectively. It can be concluded that the improved performance during early life did not improve growth during the fattening period.;Tässä tutkimuksessa selvitettiin, vaikuttaako vasikkakaudenvapaa maitojuotto maitorotuisten lihanautojen kasvuun ja teurastuloksiin. Kokeessa oli yhteensä 11 vasikkaa, jotka jaettiin kahteen ryhmään. Toinen ryhmä sai koko vasikkakauden ajan eli 17 viikkoa vapaasti hapatettua maitoa. Toinen ryhmä sai kahdesti päivässä 2,5 litraa hapatettua maitoa 9 viikon ajan, jonka jälkeen ne vieroitettiin. Molemmat ryhmät saivat vasikkakaudella vapaasti väki- ja säilörehua. Vasikkakauden jälkeen molemmat ryhmät ruokittiin samalla lailla. Väkirehun osuus rehuannoksen kuiva- aineesta oli 620 g/kg ja säilörehua annettiin vapaasti. Sonnit teurastettiin keskimäärin 429 pv ikäisinä, jolloin niiden ruhot olivat keskimäärin 292 kg painoisia. Vapaasti maitoa saaneet vasikat joivat ensimmäisten 9 viikon ajan enemmän maitoa kuin rajoitetustjuotetut (1.09 vs. 0.59 kg kuiva-aineena) ja ne kasvoivat nopeammin (1003 vs. 725 g/pv). Vasikkakauden loppupuoliskolla molemmat ryhmät kasvoivat yhtä nopeasti (vapaasti juotetut 1361 g/pv ja rajoitetusti juotetut 1447 g/pv). Kasvatuskauden alkaessa keskimäärin 175 pv iässä vapaasti juotetut sonnit olivat keskimäärin 14 kg painavampia (ei merkitsevä ero) kuin rajoitetusti juotetut sonnit. Kasvatuskauden aikana ryhmien välillä ei ollut merkitseviä eroja päiväkasvussa, rehun muuntosuhteessa, kasvatusajan pituudessa eikä teurastuloksissa. Tulokset osoittavat, että runsaan maidonjuonnin aiheuttama kasvun nopeutuminen vasikkakaudella ei vaikuttanut myönteisesti lihanautojen kasvuun koko kasvatuskautta tarkasteltaessa

The effect of free or restricted acidified milk feeding of Finnish Ayrshire bull calves on the subsequent fattening and slaughter performance

The aim of the research was to study whether the anticipated added weight gain from ad libitum acidified milk feeding compared to restricted milk feeding during the preweaning period can be maintained after weaning until slaughter. The study was conducted by comparing first the growth performance of eleven bull calves until an average age of 126 days (Phase 1) when the five calves were fed acidified milk either ad libitum (FM) for 17 weeks or when six calves were given acidified milk restrictively (5 l per day, RM) for nine weeks. Bulls had ad libitum access to grass silage and concentrate. Secondly, the performance of bulls having an average age of 175 days until slaughter (at an average age of 429 days) at a carcass weight of approximately 290 kg was assessed (Phase 2). All animals were fed grass silage ad libitum and concentrate at a level of 620 g kg-1 of dietary dry matter. Calves fed acidified milk ad libitum grew significantly (P < 0.01) faster than those fed restrictively during the first nine weeks of Phase 1 (1003 vs. 725 g per day). The bulls in the RM group grew a little but not significantly faster during Phase 2, the growth rates being 1197 vs. 1207 g per day. The feed conversion, weight (535 vs. 533 kg at slaughter) and slaughter results were equal. Similarly the life-time gains did not differ being 1174 (FM) and 1141 (RM) g per day, respectively. It can be concluded that the improved performance during early life did not improve growth during the fattening period.