Impact of iron-modified biochars on soil nitrous oxide emissions: Variations with iron salts and soil fertility.

Nitrous oxide (N2O) emissions from soils are a significant environmental concern due to their contribution to greenhouse gas emissions. Biochar has been considered as a promising soil amendment for its potential to influence soil processes. Iron modification of biochar has been extensively discussed for its ability to enhance adsorption of pollutants, yet its impact on mitigating soil N2O emissions remains poorly understood. In the present study, corn straw (CB) and wood (WB) biochars were treated with FeSO4/FeCl3 (SCB and SWB) and Fe(NO3)3 (NCB and NWB). The effects of these biochars on soil N2O emissions were investigated using soils with varying fertility levels over a 35-day incubation period at 20 °C. Results revealed significant variations in biochar surface chemistry depending on biochar feedstock and iron salts. Compared to pristine biochars, NWB and NCB exhibited higher pH, total N content, and dissolved NO3-N concentrations (246 ± 17 and 298 ± 35 mg kg-1, respectively), but lower bulk and surface C content. In contrast, SWB and SCB demonstrated acidic pH and elevated dissolved NH4-N concentrations (5.38 ± 0.43 and 4.19 ± 0.22 mg kg-1, respectively). In forest soils, NWB and NCB increased cumulative N2O emission by 28.5% and 67.0%, respectively, likely due to the introduction of mineral nitrogen evidenced by significant positive correlation with NO3-N or NH4-N. Conversely, SWB and SCB reduced emissions in the same soil by 28.5% and 6.9%, respectively. In agricultural soil, most biochars, except SWB, enhanced N2O emissions, possibly through the release of labile organic carbon facilitating denitrification. These findings underscore the significance of changes in biochar surface chemistry and the associated potential risk in triggering soil N2O emissions. This study highlights the need for a balanced design of biochar that considers both engineering benefits and climate change mitigation.

Combined effects of biochar and biogas slurry on soil nitrogen transformation rates and N2O emission in a subtropical poplar plantation.

It has been widely accepted that biochar has a great potential of mitigating soil nitrous oxide (N2O) emission. However, the underlying mechanism about how biochar affects nitrogen transformation and the pathways of soil N2O production is under discussion. A 15N-tracer incubation experiment was conducted to investigate the short-term effects of biochar on soil N transformation rates and source partitioning of N2O emissions in soils from a poplar plantation system. A two-factor experimental design was adopted using biogas digestate slurry and biochar as soil amendments. In total, there were 12 treatments, including three rates of biochar: B0 (control), B2 (80 t ha-1), and B3 (120 t ha-1), and four rates of biogas digestate slurry: C (0 m3 ha-1), L (125 m3 ha-1), M (250 m3 ha-1), and H (375 m3 ha-1). We observed significantly lower rates of net nitrification (Nn) and mineralization (Mn) in biochar-treated soils. The 15N tracer analysis revealed a significant decrease in gross autotrophic (ONH4), heterotrophic nitrification (ONrec), and mineralization (MNorg) rates while an increase in gross immobilization (INH4 and INO3) rates in biochar amended soils. When biogas slurry was applied, biochar only significantly reduced ONH4 except in the moderate slurry treatment. Regardless of the slurry application, biochar consistently suppressed N2O emission by 58-89 %, and nitrification was the dominant pathway accounting contributing >90 % to cumulative N2O emissions. Moreover, soil cumulative N2O emissions significantly negatively correlated with soil ammonium contents and positively with MNorg, Mn, and Nn, showing that biochar decreased N2O emission via a reducing effect on nitrification rates and associated N2O emissions. Our results also highlight that application of N fertilizer greatly influence the biochar's impacts on soil N transformation rates and N2O emission, calling for further studies on their interactions to develop mitigate options and to improve N use efficiency.

Pain and side effects associated with 4-dimensional hysterosalpingo-contrast sonography for evaluating of the fallopian tubes patency.

4-Dimensional hysterosalpingo-contrast sonography (4 D HyCoSy) using SonoVue is regarded as a really good option available for evaluating fallopian tubal patency. This study was designed to assess the pain and adverse effects incurred by women undergoing 4 D HyCoSy. Through evaluating the pelvic pain immediately after 4 D HyCoSy and 30 min after 4 D HyCoSy, the circumstances of the pain relief was also observed. The predictive factors of pain were assessed simultaneously. 827 consecutive women as part of infertility evaluation were included. The pain experienced was then assessed on a 10-cm visual analogue scale (VAS). Each patient was questioned to rate the pain at two different points of time (T1, immediately after 4 D HyCoSy; T2, 30 min after 4 D HyCoSy). 818/827 (98.9%) patients completed the procedure. Pain was experienced by 757/818 (92.5%) of subjects. 30 min after HyCoSy procedure, only 0.5% (4/818) patients feel severe pelvic pain and after 15-30 minutes of rest, these patients were relieved of pain. Age, cycle length, duration of menses, and duration of infertility were not significantly correlated with pain associated with 4 D HyCoSy as assessed by VAS. Women with tubal obstruction experienced a significant increase in 4 D HyCoSy-associated pain. There were significant differences in the degree of pain between different tubal patency (p <0.01). Overall, 4 D HyCoSy, a user-friendly, multidimensional technology, has the advantage of real-time, dynamic, well tolerated, and low serious complications, which make it a good way for evaluating fallopian tubal patency. The technique aids in making choices concerning further procedures for the diagnosis and treatment of infertility. Most of women experience pain associated with the procedure and 30 minute period of observation is useful.