Long-term experimental diagenesis of aragonitic biocarbonates: from organic matter loss to abiogenic calcite formation

Carbonate biological hard tissues are valuable archives of environmental information. However, this information can be blurred or even completely lost as hard tissues undergo diagenetic alteration. This is more likely to occur in aragonitic skeletons because bioaragonite commonly transforms into calcite during diagenesis. For reliably using aragonitic skeletons as geochemical proxies, it is necessary to understand in depth the diagenetic alteration processes that they undergo. Several works have recently investigated the hydrothermal alteration of aragonitic hard tissues during short term experiments at high temperatures (T > 160 °C). In this study, we conduct long term (4 and 6 months) hydrothermal alteration experiments at 80 °C using burial-like fluids. We document and evaluate the changes undergone by the outer and inner layers of Arctica islandica shell, the prismatic and nacreous layers of Haliotis ovina shell, and the skeleton of Porites sp. combining a variety of analytical tools (X-ray diffraction, thermogravimetry analysis, laser confocal microscopy, scanning electron microscopy, electron backscatter diffraction and atomic force microscopy). We demonstrate that this approach is the most adequate to trace subtle, diagenetic alteration-related changes in aragonitic biocarbonates. Furthermore, we unveil that the diagenetic alteration of aragonitic hard tissues is a complex multi-step process where major changes occur even at the low temperature used in this study and well before any aragonite into calcite transformation takes place. Alteration starts with biopolymer decomposition and concomitant generation of secondary porosity. These processes are followed by abiogenic aragonite precipitation that partially or totally obliterates the secondary porosity. Only afterwards any transformation of aragonite into calcite takes place. The kinetics of the alteration is highly dependent on primary microstructural features of the aragonitic biomineral. While the skeleton of Porites sp. remains virtually unaltered within the time spam of the experiments, Haliotis ovina nacre undergoes extensive abiogenic aragonite precipitation, the outer and inner layers of Arctica islandica shell are significantly affected by aragonite transformation into calcite and this transformations extensive in the case of the prismatic layer of Haliotis ovina shell. Our results suggest that most aragonitic fossil archives may be overprinted, even those free of clear diagenetic alteration signs. This finding may have major implications for the use of these archives as geochemical proxies.

Changes in Chemical Properties of Banana Pseudostem, Mushroom Media Waste, and Chicken Manure through the Co-Composting Process

Co-composting is an effective approach to biowaste management. The co-composting potential of banana pseudostem (BPS) and mushroom media waste (MMW) with chicken manure (CM) has not been explored, let alone their suitable ratios of co-composting being determined. Meanwhile, the imbalance ratios of the feedstocks used in the process severely restrict the physicochemical properties and quality of the finished product. For this reason, six different ratios of BPS, MMW, and CM, viz. 1:1:1, 1:2:1, 1:3:1, 2:1:1, 2:2:1, and 2:3:1, respectively (T1–T6), were composted together in aerobic conditions to identify the suitable ratio by evaluating the changes in the physicochemical properties in the composting process. According to the ratio of treatments, the feedstocks were mixed on fresh weight basis. The turning process of co-composting piles was repeated at seven-day intervals to maintain the uniform aeration throughout the composting period. The piles having BPS, MMW, and CM at ratios of 1:2:1, 1:3:1, and 2:3:1, respectively, demonstrated a longer thermophilic phase, indicating more complete decomposition and earlier maturity compared to piles with higher amount of BPS. Of the ratios, BPS:MMW:CM at 1:2:1 ratio (T2) resulted in the highest total nitrogen (1.53%), lowest C:N ratio (12.4), organic matter loss (54.5%), and increased CEC (41.3 cmol/kg). The highest germination index (129%) was also recorded in the T2 compost, indicating that it was toxic-free and safe for seed germination. The nutrient-rich compost with high alkaline pH (≥10) can effectively ameliorate soils of an acidic nature, for example, the acidity of Ultisols and Oxisols.

Reconciling Reduced Red Meat Consumption in Canada with Regenerative Grazing: Implications for GHG Emissions, Protein Supply and Land Use

This paper reconciled the soil ecology benefits of forages and ruminants with reducing GHG emissions from beef. A scenario analysis compared four integrated systems for beef, pork and broilers. Slaughter cattle diets were either business as usual (BAU) or grass fed (GF), and the combined red meat consumption could not exceed the recommendation for human health. The four consumption scenarios included (PS1) equal beef and pork with BAU beef, (PS2) equal beef and pork with GF beef, (PS3) more pork and less beef with GF beef and (PS4) more pork and less beef with BAU beef. Broiler consumption was increased to force all four scenarios to provide the same amount of protein. All four scenarios required similar feed grain areas (2.5 to 3 Mha). At 2.3, 4.4, 2.2 and 1.2 Mha for PS1, PS2, PS3 and PS4, respectively, the areas in harvestable forage showed much greater variation. From high to low GHG emissions, the ranking of scenarios was PS2, PS1, PS3 and PS4. Although allowing for avoidance of soil organic matter loss changed this ranking, the carbon footprint of beef production was still double or more that of pork in all four PS. To reconcile the agro-ecological benefits of beef with reducing GHG emissions, PS3 may be better than PS4. Along with eating more pork and broilers, and less red meat overall, consumers can choose GF beef as an occasional alternative.

Microplastics have shape- and polymer-dependent effects on soil aggregation and organic matter loss – an experimental and meta-analytical approach

Microplastics are a diverse and ubiquitous contaminant, a global change driver with potential to alter ecosystem properties and processes. Microplastic-induced effects in soils are manifold as microplastics differ in a variety of properties among which the shape is of special interest. Our knowledge is limited regarding the impact of various microplastic shapes on soil processes. Therefore, we conducted this two-part research comprising a meta-analysis on published literature and a lab experiment focusing on microplastic shapes- and polymer-induced effects on soil aggregation and organic matter decomposition. We here focus on fibers, films, foams and particles as microplastic shapes.In the meta-analysis, we found a strong research focus on fibrous and particulate microplastic materials, with films and foams neglected.Our experiment showed that microplastic shapes are important modulators of responses in soil aggregation and organic matter decomposition. Fibers, irrespective of their chemistry, negatively affected the formation of aggregates. However, for other shapes like foams and particles, the polymer identity is an important factor co-modulating the soil responses.Further research is needed to generate a data-driven foundation to permit a better mechanistic understanding of the importance and consequences of microplastics added to soils.

ENTROPY PRODUCTION AND STABILITY OF DYNAMICS IN MODELS OF OPEN EXPLOITED TROPHIC CHAINS WITH EXPLICIT RESOURCE AND OMNIVORY EFFECT

Connection between stability of stationary states and such a thermodynamic property as an entropy production is studied for open trophic chains with explicit resource and omnivory effect. Entropy production is minimal in stable steady states under condition of non-negativity for their components. Marine trophic chains with “microbial loop” serve as examples of that kind of ecosystems with vertical structure. One of them is the pelagial of the Okhotsk Sea in Russian Far East. Additional organic matter passing through the loop facilitates the entropy production decrease, more organized trophic functioning and less organic matter loss comparing to the chain without omnivory

Co-Composting of Khat-Derived Biochar with Municipal Solid Waste: A Sustainable Practice of Waste Management

Biochar is a way to improve the performance of the composting process and the quality of compost. This study was aimed to investigate the optimum ratio of khat straw (Catha edulis) biochar and organic municipal solid waste mixtures to improve the quality of the resulting co-composts. Khat-derived biochar during pyrolysis at 350 °C was added to organic municipal solid waste mix and four co-composting treatments were prepared with the compositions (% w/w): control compost (no biochar) and 5%, 15%, and 25% co-composted biochar in three replicates. The total organic carbon, organic matter, total nitrogen, available phosphorus, and potassium values ranged as 16.76–21.45%, 30.77–40.26%, 0.97–1.68%, 0.58–0.76%, and 12.72–15.29%, respectively. The results confirmed that 5% and 15% co-composted khat biochars had significantly reduced (p < 0.05) organic matter loss and increased the contents of cation exchange capacity, pH, phosphorous, potassium, calcium, magnesium, and zinc compared to the control compost, while some heavy metals (Fe, Cu, and Mn) and EC values in co-composted biochars are lower than the control compost. Khat-derived biochar could be added to municipal organic waste mix at 5–15% (w/w) in order to get better quality of compost, which can be used as biofertilizer.

Effectiveness of preserving agents in alfalfa ensiling

Проведены исследования по силосованию люцерны, убранной в ранней фазе вегетации, с использованием биологического и химического консервантов. Цель работы — определить эффективность использования химического и биологического консервантов при силосовании люцерны. Исходным сырьём для проведения исследований служила зелёная масса люцерны в фазе бутонизации. Консерванты вносили при закладке массы из расчёта 5 л/т. В качестве консервантов использовали экспериментальные препараты: биологический — на основе смеси молочнокислых и пропионовокислых бактерий, химический — на основе смеси органических кислот. Интенсивность протекания биохимических процессов определяли в течение месяца после закладки посредством учёта воды, вытесненной газами. Установлено, что консерванты снижают интенсивность биохимических процессов, протекающих при силосовании. По сравнению с контролем объём выделившихся газов при внесении биологического консерванта оказался меньше на 15,3%, с использованием химического консерванта — в 3,2 раза. Энергетическая ценность исходного сырья составила 2,26 МДж обменной энергии, силоса без консерванта — 1,84, с биологическим и химическим консервантами — 1,96 и 2,06 МДж обменной энергии соответственно. В контрольном варианте потери органического вещества по сравнению с исходным сырьём составили 14,7%, что больше в 1,24 раза, чем в варианте с биологическим консервантом и в 4,17 раза — с химическим консервантом. Примерно такая же тенденция отмечена и по потерям протеина и БЭВ. В расчёте на 1 т силоса применение биологического консерванта позволило дополнительно получить 119,6 МДж обменной энергии, с химическим консервантом — 246,4 МДж обменной энергии по сравнению с контролем. При скармливании 1 т консервированного корма молочным коровам дополнительно можно получить 13,3 и 27,4 кг молока, а дополнительная выручка может составить 279 и 442 руб. соответственно. The research aimed at testing the effect of chemical and biological preservation when ensiling alfalfa. Green mass was collected at the budding stage. Application rate — 5 l/t. Preparation were composed of either the mixture of lactic and propionic acid bacteria or organic acids. Intensity of biochemical processes was determined as water loss via gas formation. Preserving agents negatively affected biochemical reactions in silage. The bacterial preparation reduced gasification by 15.3%, chemical preservative — by 3.2 times. Row mass contained 2.26 MJ of exchange energy, untreated silage — 1.84, mass treated with the bacterial and chemical preparations — 1.96 and 2.06 MJ, respectively. Organic matter loss amounted to 14.7% in the control silage, exceeding bacterial and chemical ensiling by 1.24 and 4.17 times, respectively. The same tendency was observed for protein and nitrogen-free extractive substances. Bacterial agents provided exchange energy increase of 119.6 MJ per 1 t of silage mass, the chemical preparation — 246.4 MJ. Feeding cows with 1 t of experimental silage resulted in milk yield increase of 13.3 and 27.4 kg, additional revenue reached 279 and 442 RUB, respectively.

Vegetated Ditch Habitats Provide Net Nitrogen Sink and Phosphorus Storage Capacity in Agricultural Drainage Networks Despite Senescent Plant Leaching

The utility of vegetated ditch environments as nutrient sinks in agricultural watersheds is dependent in part on biogeochemical transformations that control plant uptake and release during decomposition. We investigated nitrogen (N) and phosphorus (P) uptake and release across four P enrichment treatments in ditch mesocosms planted with rice cutgrass (Leersia oryzoides) during the summer growing and winter decomposition seasons. Measured N retention and modeled denitrification rates did not vary, but P retention significantly increased with P enrichment. At the end of the growing season, root biomass stored significantly more N and P than aboveground stem and leaf biomass. Decomposition rates were low (<10% organic matter loss) and not affected by P enrichment. Nitrogen and P export during winter did not vary across the P enrichment gradient. Export accounted for <10% of observed summer N uptake (1363 mg m−2), with denitrification potentially accounting for at least 40% of retained N. In contrast, net P retention was dependent on enrichment; in unenriched mesocosms, P uptake and release were balanced (only 25% net retention), whereas net retention increased from 77% to 88% with increasing P enrichment. Our results indicate that vegetated ditch environments have significant potential to serve as denitrification sinks, while also storing excess P in agricultural watersheds.