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In recent decades, there has been a growing interest in the recycling of organic materials such as paper mill biosolids (PB) and biochar for use as soil amendments. However, the benefits of co-application of PB and biochar and its effects on soil phosphorus (P) availability remain unknown. An incubation study was conducted on two acidic soils to assess the effect of two PB types (2.5% w/w) co-applied with three rates (0%, 2.5%, and 5% w/w) of pine (Pinus strobus L.) biochar on soil P fractions. An unfertilized control and a mineral NP fertilizer were used as a reference. Soil P fractions were determined by Hedley procedure after 2 and 16 wk of incubation. Material fractionation indicated that the PB containing the highest total P and the lowest Al content had the highest proportion of labile P, whereas most P in the biochar was in a stable form. The incubation study revealed that the P-rich PB increased P availability in both soils to a level comparable to mineral fertilizer at the end of the incubation. The addition of biochar to PB, however, did not affect soil P availability, but the highest rate induced a conversion of P fixed to Al and Fe oxides towards recalcitrant forms, particularly in the sandy loam soil. We conclude that co-applying biochar and PB could be more beneficial than application biochar alone and soils amended with such a mixture would be expected to release part of their P slowly over a longer period of time.

Amending croplands with forest residues may help in restoring soil properties in fields subject to intensive land management. Despite their known benefits when applied separately, co-application of wood biochar with paper mill biosolids (PB) has seen little investigation under field conditions. A study was initiated in Québec, QC, Canada, to determine the effect of a single application of wood biochar with and without PB on the nitrogen (N) and phosphorus (P) availability of two pH-neutral to alkaline loamy soils. Biochar at 0, 10, and 20 Mg dry weight·ha−1 and PB at 30 Mg wet weight·ha−1 were applied before planting of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] in 2018. Residual effect of this co-application was determined under soybean and corn in the subsequent year. In both years, corn received supplemental N and P from mineral fertilizers according to local agronomic recommendations. Co-applying biochar and PB reduced soil NO3-N availability in the year of application and decreased corn yield by 1.0 Mg·ha−1 compared with biochar or PB applied alone, but these amendments did not affect soybean yields. In the following year, the previous biochar addition increased soybean yield by 0.6 Mg·ha−1 but had little effect on corn. For both years, biochar addition induced a large increase in soil Mehlich-3 P. This study revealed that wood biochar positively impacted P status of these soils but was not a source of N to crops even when co-applied with PB.

Acidification and metal mobility may present challenges in soil receiving paper mill biosolids (PB). Co-applying biochar and PB could help prevent these issues, but its effect must be assessed. The objective of this 224 d incubation study was to evaluate the effect of amending two acidic soils, a clay and sandy loam, with two PB types varying in pH (PB1, pH = 7.80; and PB2, pH = 4.51) co-applied with three rates (0%, 2.5%, and 5% w/w) of pine (Pinus strobus L.) biochar on soil pH and macro- (P, K, Ca, and Mg) and micronutrients (Cu, Zn, Fe, and Mn). In both soils, co-applying biochar and PB significantly increased soil pH and extractable K concentration compared with PB-only application, whereas amending with PB significantly increased soil extractable P concentration compared with the unamended soil. In comparison with PB only, co-applying 5% biochar and PB decreased extractable Cu concentration in both soils and extractable Fe concentration in the sandy loam soil. This study showed that co-applying biochar and PB can be more beneficial to agricultural soils than application of PB alone by supplying nutrients and helping prevent metal toxicity by raising pH, especially in acidic sandy soils.

Non-cyanobacteria diazotrophs (NCDs) were shown to dominate in surface waters shifting the long-held paradigm of cyanobacteria dominance and raising fundamental questions on how these putative heterotrophic bacteria thrive in sunlit oceans. Here, we report an unprecedented finding in the widely used model diatom Phaeodactylum tricornutum (Pt) of NCDs sustaining diatom cells in the absence of bioavailable nitrogen. We identified PtNCDs using metagenomics sequencing and detected nitrogenase gene in silico and/or by PCR. We demonstrated nitrogen fixation in PtNCDs and their close genetic affiliation with NCDs from the environment. We showed the wide occurrence of this type of symbiosis with the isolation of NCDs from other microalgae, their identification in the environment, and predicted their associations with photosynthetic microalgae. Overall, this study provides evidence for a previously overlooked symbiosis using a multidisciplinary model-based approach, which will help understand the different players driving global marine nitrogen fixation.

Adding biochar to paper mill biosolids (PB) amendments may affect PB mineralization rate and nitrogen (N) availability. The objective of this 224-day incubation study was to evaluate the effect of amending two PB types varying in carbon (C)/N ratio (PB1, C/N = 24; and PB2, C/N = 13) with three rates (0%, 2%, and 5%) of pine (Pinus strobus L.) biochar produced at 700 °C on the dynamics of total C, total N, mineral N, N mineralization rate, and microbial biomass C (MBC) and N (MBN) in two agricultural soils (Kamouraska clay and St-Antoine sandy-loam). Two reference treatments were also included, namely, mineral fertilization and unamended soil. Total soil C concentration remained stable over the incubation period, whereas a decrease in total soil N was observed in both soils. In comparison with the unamended soil, the application of PB significantly increased total N, NH4-N, NO3-N, net mineralized N, applied N mineralization rate, and MBC in both soils. In comparison with the application of PB alone, biochar addition increased total C and MBC but decreased NH4-N, NO3-N, net N mineralization, and applied N mineralization rate in both soils. The co-application of biochar and PB1 resulted in the sequestration of mineral N released, which was more pronounced in the Kamouraska clay soil. The co-application of biochar and PB2 resulted in moderate release of mineral N. This study showed that the co-application of biochar and PB can benefit agricultural soils by improving NO3-N retention in agroecosystems while increasing organic matter and promoting microbial biomass.

Co-applying biochar and paper mill biosolids (PB) improves the potential of these by-products as soil amendments. Assessing the response of soil microbial communities to the co-application of biochar and PB is of great importance to further understanding their effectiveness. This hypothesis was tested in a 112-day incubation study performed separately on two acidic soils (Kamouraska clay and St-Antoine sandy loam) using two PB types (PB1 with C/N = 24 and PB2 with C/N = 13), co-applied with one of three rates (0%, 2.5%, and 5% w/w) of pine (Pinus strobus L.) biochar. An unamended control and a mineral-fertilized treatment were used as a reference. In the Kamouraska clay soil, co-applying 5% biochar and any PB increased microbial activity compared to PB-only application, as indicated by the fluorescein diacetate (FDA) hydrolysis assay. In both soils, co-applying biochar and PB did not affect microbial diversity and community structure compared with PB only. The application of any PB, however, increased microbial activity in both soils, while only PB2 shifted microbial community structure. Within each amendment and in both soils, microbial activity was lower at day 112 than at days 28 and 56, while major temporal shifts were observed only for bacterial community structure. Indeed, the difference in bacterial community structure between amendments was more pronounced at day 112. This study suggests that co-applying biochar and PB can improve soil properties than application of PB alone by increasing soil microbial activity without side effects on microbial diversity and community structure, especially in acidic clay soils.

Charging characteristics of carbon nanofibers (CNFs) with a 241-Am charge neutralizer were investigated using diameter- and length-controlled CNF particles, which were generated by a floating catalyst CVD method. The neutral fraction and charge distribution of CNF measured by aerosol techniques suggested that the fraction of neutral particles is much lower than that predicted by the conventional charging theory for spherical particles and that there exist a large number of multiply charged particles in charge equilibrium. Furthermore, it was found that the charge equivalent diameter that is twice the one proposed in a previous work gives a good prediction for the charge distribution of CNF with a diameter smaller than 20 nm and aspect ratio between 5 and 40. © 2014 The Society of Chemical Engineers, Japan., 出版社照会後に全文公開

Our group developed a high-performance unipolar charger for sub-10-nm particles using a surface-discharge microplasma by increasing the charging time and minimizing the electrostatic deposition loss of the charged particles. An investigation of the discharge voltages of various discharge voltage waveforms demonstrated that a sinc function of time, t, that is, (sin ωt)/ωt with a bias voltage, achieved a high extrinsic charging efficiency (a high yield of charged particles) by generating a high concentration of ions and suppressing the electrostatic deposition of the charged particles. In trial operation at the optimal discharge voltage and an aerosol flow rate of 2.5 L/min, the charger attained intrinsic and extrinsic charging efficiencies of 79.3 and 61.4% for 10-nm particles and intrinsic and extrinsic charging efficiencies of 48.0 and 34.6% for 5-nm particles, respectively. Copyright 2013 American Association for Aerosol Research

In order to evaluate the potential of surface-discharge microplasma devices (SMDs) as ion sources for high-efficiency electrical charging of nanoparticles, a long SMD was installed in a surface-discharge microplasma aerosol charger (SMAC), and the charging performance of the SMD for aerosol nanoparticles was measured. The intrinsic charging efficiency for 5-nm-diameter particles was approximately 60%, and that for 10-nm-diameter particles was 90% at an aerosol flow rate of 1.5 L · min−1 because a long SMD is capable of generating a uniform concentration of ions over a wide area. The size-dependent charging efficiencies for these aerosol nanoparticles with diameters ranging between 3 nm and 30 nm were in good agreement with those predicted using the diffusion charging theory. The product of ion concentration (N) and charging time (t), estimated via the diffusion charging theory, was 3.0×1013 s · m−3, which is one order of magnitude higher than that for previously reported chargers. These results confirm the high potential of SMDs as ion sources for charging aerosol nanoparticles.