Influence of Citrate and Phosphate on the Adsorption of Adenosine-5′-Monophosphate at the Hematite Water Interface

Nucleic acid derived organic phosphorus (Po) is an important source of plant available P when degraded to inorganic phosphate (P(V)i). It is known that when nucleic acids or components are adsorbed on mineral surfaces, the enzymatic degradation is hindered or delayed. Thus, understanding adsorption/desorption mechanisms of nucleic acids and their derivatives are key to assess the biogeochemical pathways of Po cycling. Here we report adsorption mechanisms of adenosine-5′-monophosphate (AMP) on hematite, a common iron oxide mineral, under various solution properties using macroscopic and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic probes. The effects of citrate, mimicking organic acids from roots exudates, and the influence of P(V)i, representing inorganic fertilizer application, were also evaluated on the release of adsorbed AMP under various solution properties. The results suggested that AMP adsorbed with the hematite surface via the phosphate moiety, N7 atom and the π electron systems of the adenine moiety. The presence of citrate significantly decreased the AMP adsorption, which was also corroborated by the negative phosphate IR bands in the results of AMP and citrate competitive adsorption experiments monitored by in situ ATR-FTIR probe. Like citrate, P(V)i also reduced AMP adsorption on hematite. Our findings suggest a potential novel pathway of nucleic acid derived Po cycling in the soil environment

Antimony (V) Adsorption at the Hematite–Water Interface: A Macroscopic and In Situ ATR-FTIR Study

The environmental mobility of antimony (Sb) is largely unexplored in geochemical environments. Iron oxide minerals are considered major sinks for Sb. Among the different oxidation states of Sb, (+) V is found more commonly in a wide redox range. Despite many adsorption studies of Sb (V) with various iron oxide minerals, detailed research on the adsorption mechanism of Sb (V) on hematite using macroscopic, spectroscopic, and surface complexation modeling is rare. Thus, the main objective of our study is to evaluate the surface complexation mechanism of Sb (V) on hematite under a range of solution properties using macroscopic, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic, and surface complexation modeling. The results indicate that the Sb (V) adsorption on hematite was highest at pH 4–6. After pH 6, the adsorption decreased sharply and became negligible above pH 9. The effect of ionic strength was negligible from pH 4 to 6. The spectroscopic results confirmed the presence of inner- and outer-sphere surface complexes at lower pH values, and only outer-sphere-type surface complex at pH 8. Surface complexation models successfully predicted the Sb (V) adsorption envelope. Our research will improve the understanding of Sb (V) mobility in iron-oxide-rich environments

Field-Grown Transgenic Switchgrass (Panicum virgatum L.) with Altered Lignin Does Not Affect Soil Chemistry, Microbiology, and Carbon Storage Potential

Cell wall recalcitrance poses a major challenge on cellulosic biofuel production from feedstocks such as switchgrass (Panicum virgatum L.). As lignin is a known contributor of recalcitrance, transgenic switchgrass plants with altered lignin have been produced by downregulation of caffeic acid O-methyltransferase (COMT). Field trials of COMT-downregulated plants previously demonstrated improved ethanol conversion with no adverse agronomic effects. However, the rhizosphere impacts of altering lignin in plants are unknown. We hypothesized that changing plant lignin composition may affect residue degradation in soils, ultimately altering soil processes. The objective of this study was to evaluate effects of two independent lines of COMT-downregulated switchgrass plants on soils in terms of chemistry, microbiology, and carbon cycling when grown in the field. Over the first two years of establishment, we observed no significant differences between transgenic and control plants in terms of soil pH or the total concentrations of 19 elements. An analysis of soil bacterial communities via high-throughput 16S rRNA gene amplicon sequencing revealed no effects of transgenic plants on bacterial diversity, richness, or community composition. We also did not observe a change in the capacity for soil carbon storage: There was no significant effect on soil respiration or soil organic matter. After five years of establishment, δ13C of plant roots, leaves, and soils was measured and an isotopic mixing model used to estimate that 11.2 to 14.5% of soil carbon originated from switchgrass. Switchgrass-contributed carbon was not significantly different between transgenic and control plants. Overall, our results indicate that over the short term (two and five years), lignin modification in switchgrass through manipulation of COMT expression does not have an adverse effect on soils in terms of total elemental composition, bacterial community structure and diversity, and capacity for carbon storage

The small pelagic fishery of the Pemba Channel, Tanzania: what we know and what we need to know for management under climate change

Small pelagic fish, including anchovies, sardines and sardinellas, mackerels, capelin, hilsa, sprats and herrings, are distributed widely, from the tropics to the far north Atlantic Ocean and to the southern oceans off Chile and South Africa. They are most abundant in the highly productive major eastern boundary upwelling systems and are characterised by significant natural variations in biomass. Overall, small pelagic fisheries represent about one third of global fish landings although a large proportion of the catch is processed into animal feeds. Nonetheless, in some developing countries in addition to their economic value, small pelagic fisheries also make an important contribution to human diets and the food security of many low-income households. Such is the case for many communities in the Zanzibar Archipelago and on mainland Tanzania in the Western Indian Ocean. Of great concern in this region, as elsewhere, is the potential impact of climate change on marine and coastal ecosystems in general, and on small pelagic fisheries in particular. This paper describes data and information available on Tanzania's small pelagic fisheries, including catch and effort, management protocols and socio-economic significance

Soil And Water Chemistry

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Soil and plant response to applications of phosphorus fertilizers and sulfuric acid

Research report containing the results of experiments to determine the effectiveness of phosphorus fertilizers and sulfuric acid in increasing phosphorus availability to plants in soils common in the Southwest

The cation exchange behavior of tylosin in loess-derived soil

Tylosin (Tyl) is a veterinary antibiotic commonly used in swine and poultry production. Due to metabolic inefficiencies, it enters the environment through manure applications. Ion exchange is an important retention mechanism for Tyl, particularly for smectite clay. The objectives of this study are to characterize the exchange interactions of Tyl with common soil cations in subsoil horizons that contain smectite and to investigate the interactions using in situ Fourier transform infrared (FTIR) spectroscopy. Adsorbed Tyl in pH neutral, smectitic subsoil horizons is divided into exchangeable and nonexchangeable forms. The percentage of adsorbed Tyl that is exchangeable varies from 36% to 43% when Na+ is the competing cation, and from 57% to 66% when Ca2+ competes. In NaX-TylX binary exchange systems, neither Na+ nor Tyl+ is preferred by the clay exchange phase, and the Vanselow selectivity coefficients (KV) for the NaX→TylX exchange reaction range between 0.79 and 1.41. In the CaX2-TylX systems, Tyl+ is preferred by the clay exchange phase when the equivalent fraction of TylX (ETylX) is less than 0.4. The KV values for the CaX2→TylX exchange reaction are at a maximum at the lowest ETylX values, with 17.6 \u3c KV \u3c 58.1, then decrease with increasing ETylX to 1.34 \u3c KV \u3c 6.28. Adsorbed Tyl masks the CEC of the soil clays; the effect is greatest in systems that are initially Tyl-saturated, and is attributed to the steric effects of the large Tyl molecule. In situ FTIR indicates that Tyl interacts with soil iron oxides through the dimethylamine moiety