Dissolution of Ag Nanoparticles in Agricultural Soils and Effects on Soil Exoenzyme Activities

To assess environmental risks related to the mobility and toxicity of AgNPs, the chemical availability of AgNPs and polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs) in three agricultural soils was quantified in a pot experiment. Porewater collection and soil extractions with 0.01 M CaCl2, 0.4 M Glycine (pH 1.5) and 0.05 M NH4-EDTA were performed. The effect on soil exoenzyme activities was also assessed. Porewater concentration was low (<0.4% and <0.04% of dosed Ag, for AgNPs and PVP-AgNPs, respectively) and only detected in acidic soils (pH 4.4 and 4.9). The PVP-coating reduced the downward mobility of AgNPs in soil and possibly also their dissolution rate (and subsequent release of dissolved Ag+ ions into porewater). The effect of variation in organic matter on soil enzymatic activity was larger than that of AgNPs, as no significant additional inhibitory effect from Ag could be observed. Only at low pH and in the presence of complexing ligands that form very stable Ag complexes (0.4 M Glycine extraction at pH 1.5) up to 58% of the Ag added to soil was released (independently of PVP coating). An extraction with glycine is proposed as a useful indicator of potentially available Ag in soils.

Optimized and scalable synthesis of magnetic nanoparticles for RNA extraction in response to developing countries' needs in the detection and control of SARS-CoV-2

Ecuador is one of the most affected countries, with the coronavirus disease 2019 (COVID-19) infection, in Latin America derived from an ongoing economic crisis. One of the most important methods for COVID-19 detection is the use of techniques such as real time RT-PCR based on a previous extraction/purification of RNA procedure from nasopharyngeal cells using functionalized magnetic nanoparticles (MNP). This technique allows the processing of ~ 10,000 tests per day in private companies and around hundreds per day at local Universities guaranteeing to reach a wide range of the population. However, the main drawback of this method is the need for specialized MNP with a strong negative charge for the viral RNA extraction to detect the existence of the SARS-CoV-2 virus. Here we present a simplified low cost method to produce 10 g of nanoparticles in 100 mL of solution that was scaled to one litter by parallelizing the process 10 times in just two days and allowing for the possibility of making ~ 50,000 COVID-19 tests. This communication helps in reducing the cost of acquiring MNP for diverse biomolecular applications supporting developing country budgets constraints and chemical availability specially during the COVID-19 International Health Emergency.

Level, Source, and Spatial Distribution of Potentially Toxic Elements in Agricultural Soil of Typical Mining Areas in Xiangjiang River Basin, Hunan Province

The concentrations, chemical availability, distribution, and sources of potentially toxic elements (PTEs) in the soil of Xiangjiang Basin in Hunan Province, China were investigated at 85 sites. The highest mean concentrations of Cd, Cu, Zn, As, and Pb were observed in Hengyang, whereas those for Mn, Co, and Hg were observed in Changde. The pollution index values followed the order: Cd > Hg > Cu > Zn > As > Pb; the mean geo-accumulation index values were in the order: Cd > Hg > Pb > Cu > Zn > As > Co > Mn. Cd was associated with moderate contaminated level, Hg and Pb were associated with moderate contaminated to uncontaminated level, and Cu, Zn, As, Co, and Mn were associated with uncontaminated level of pollution. Furthermore, 64.5% of Cd was water-soluble and exhibited exchangeable fractions; its chemical availability posed a risk to the ecosystem. Spatial analysis, principal component analysis, and a positive matrix factorization model were used to assess the PTE sources. Four principal components contributed to 88.8% of the 8 PTEs concentrations. Mining, smelting, industrial, and agricultural activities, alongside sewage irrigation, the use of agrochemicals, and vehicular emissions are the possible anthropogenic sources that pollute agricultural products and threaten human health in the Xiangjiang Basin.

Optimized and scalable synthesis of magnetic nanoparticles for RNA extraction in response to developing countries' needs in the detection and control of SARS-CoV-2

Ecuador is one of the most affected countries, with the coronavirus disease 2019 (COVID-19) infection, in Latin America derived from an ongoing economic crisis. One of the most important methods for COVID-19 detection is the use of techniques such as real time RT- PCR based on a previous extraction/purification of RNA procedure from nasopharyngeal cells using functionalized magnetic nanoparticles (MNP). This technique allows the processing of ~10,000 tests per day in private companies and around hundreds per day at local Universities guaranteeing to reach a wide range of the population. However, the main drawback of this method is the need for specialized MNP with a strong negative charge for the viral RNA purification to detect the existence of the SARS-CoV-2 virus. Here we present a simplified low cost method to produce 10 g of nanoparticles in 100 mL of solution that was scaled to one litter by parallelizing the process 10 times in just two days and allowing for the possibility of making ~50,000 COVID-19 tests. This communication helps in reducing the cost of acquiring MNP for diverse biomolecular applications supporting developing country budgets constraints and chemical availability specially during the COVID-19 International Health Emergency.

Chemical Speciation of some Heavy Metals in Sand Filter Media [SFM] Waste Dumpsite in Yenagoa, Nigeria

The chemical speciation of five heavy metals [HMs] in spent sand-filter-media [SFM] waste dumpsite was investigated with a view to ascertain their distribution and chemical availability of the heavy metals in the dumpsite. Samples were collected at the surface, 100cm depth of the dumpsite and 100m away from the dumpsite and analysed using FAAS for total concentration of Cr, Fe, Mn. Ni and Pb. Speciation analysis was carried out usingmodified Tessier’s sequential extraction method. The percentage concentrations showed that Pb occurred more at the exchangeable fraction with 90.6% at the top, 91.34% at 100cm depth. This signifies that Pb is biochemically available for in-take by living organisms. Fe had the highest concentration by mass 12mg/g but its occurrence of between 22- 28% is in the residual/inert fraction. Ni had 40% in the exchangeable and carbonate fractions at the surface and at 100cm depth. Cr had highest exchangeable fraction of 46.29% and 45.59% at the surface and 100cm depth of the SFM. Mn had 37.30% and 42.26% at the surface and at 100cm depth of the SFM. Although Fe had highest concentration by mass, it is least biochemically available occurring more at the residual/inert fraction while the other four metals [Pb, Ni, Cr, Mn] are all biochemically available for intake by organisms and may enhance biochemical accumulation overtime and finally become harmful to living organisms around that dumpsite. Keywords: Speciation, Heavy metals, Sand Filter Media, Waste Dumpsite

Distribution and Restricted Vertical Movement of Nematodes in a Heavy Clay Soil

A large part of Australia’s broad acre irrigation industry, which includes cotton, is farmed on heavy clay Vertosols. Recent changes in nematicide chemical availability, changes in rotations and the observation of the reniform nematode in central Queensland has highlighted that we need to improve our understanding of nematodes in these soils. We undertook preliminary investigations into distribution by depth under a cotton-cotton and cotton-maize rotation as well as vertical movement experiments in microcosms to better understand nematode distribution and movement in heavy clay soils. Analysis revealed that field populations decreased with soil sample depth, but there were also differences between rotations. In microcosm experiments, vertical movement of nematodes in these heavy clay soils was restricted, even in the presence of plant roots and moisture, both of which were hypothesised to improve nematode migration. The results imply that crop rotation currently remains a plausible option for nematode control, and that we still have a lot to learn about the ecology of nematode populations in Vertosols.

PSVI-9 Nutrient and energy digestibility of steam-exploded canola meal in cannulated grower pigs

Nutrient digestibility is lower in canola meal (CM) than soybean meal due to its fiber matrix. High steam pressure processing may increase nutrient digestibility of CM in pigs. To explore, Brassica napus CM was processed at 700 or 1,100 kPa followed by sudden release of pressure to ambient and yielded steam-exploded CM7 and CM11, respectively. The CM, CM7, and CM11 were included at 40% in 3 test diets. An N-free diet was fed to pigs to measure basal endogenous losses of crude protein (CP) and amino acids (AA) and served as basal to measure energy digestibility of CM. Seven ileal cannulated grower pigs (initial BW, 29 kg) were fed the 4 diets over three 9-d periods in 2 Youden squares. Pigs were fed diets at 3.0 × maintenance (110 kcal of DE per kg of BW0.75). Compared to CM, CM7, and CM11 had reduced chemical availability of lysine (87.6 vs. 83.1 and 85.7%), but lower glucosinolate content (1.14 vs. 0.99 and 0.92 µmol/g). Apparent ileal and total tract digestibility of energy was lower (P < 0.05) for CM7 than CM and intermediate for CM11, resulting in lower (P < 0.05) predicted net energy for CM7 and CM11 than CM (1.88 and 1.91 vs. 1.94 Mcal/kg, respectively). Standardized ileal digestibility (SID) of lysine was lower (P < 0.05) for CM7 and CM11 than CM (67.1 and 70.3% vs. 74.3, respectively). The SID of threonine was lower (P < 0.05) for CM7 than CM and intermediate for CM11. In summary, steam-explosion of CM damaged lysine reducing its digestibility and did not increase energy digestibility. In conclusion, steam-explosion of CM did not increase nutrient digestibility of CM for pigs.

Chemical Availability of Bromide Dictates CsPbBr3 Nanocrystal Growth

Lack of detailed understanding of the growth mechanism of CsPbBr3 nanocrystals has hindered sophisticated morphological and chemical control of this important emerging optoelectronic material. Here, we have elucidated the growth mechanism by slowing the reaction kinetics. When 1-bromohexane is used as an alternative halide source, bromide is slowly released into the reaction mixture, extending the reaction time from ~3 seconds to greater than 20 minutes. This enables us to monitor the phase evolution of products over the course of reaction, revealing that CsBr is the initial species formed, followed by Cs4PbBr6, and finally CsPbBr3. Further, formation of monodisperse CsBr nanocrystals is demonstrated in a bromide-deficient and lead-abundant solution. The CsBr can only be transformed into CsPbBr3 nanocubes if additional bromide is added. Our results indicate a fundamentally different growth mechanism for CsPbBr3 in comparison with more established semiconductor nanocrystal systems and reveal the critical role of the chemical availability of bromide for the growth reactions.<br>