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Global agricultural ecosystems, the largest biospheric sources of atmospheric carbon dioxide (CO 2 ), may turn into considerable net carbon (C) sinks through adopting management strategies advised by research. As C sequestration is usually coupled with the silicon (Si) cycle, strategic manipulation of the biogeochemical Si cycle in agricultural ecosystems offers a not yet fully explored possibility to enhance C sequestration. This review summarizes current knowledge of C sequestration coupled with the Si cycle and its management in agricultural ecosystems. Carbon sequestration is coupled with the Si cycle through many processes including dynamics of phytoliths and aggregates, and silicate weathering at different temporal and spatial scales. Cultivation of deep rooting crops, erosion mitigation with buffer strips, fertilization of Si-rich materials are some of the potential management strategies to increase both crop production and C sequestration coupled with the Si cycle. Further questions such as identifying the controlling factors of bioavailable Si pools and C sequestration, and quantifying the cost-efficiency of different management strategies to manipulate the Si cycle with the aim to enhance C sequestration should be investigated. [ABSTRACT FROM AUTHOR]

Abstract: We hypothesized that elevated atmospheric carbon dioxide concentration [CO2] as a feature of climate change promotes the occurrence of soil water repellency (SWR) which reduces soil carbon mineralization and thus increases carbon sequestration. Soil surface transects under elevated (475μLL−1) and ambient atmospheric [CO2] in a long-term Free Air Carbon Dioxide Enrichment experiment were sampled at a high spatial resolution. All samples were hydrophobic at the time of the sampling. At the micro-scale, the differences in degree and persistence of SWR, soil organic matter (SOM) content, microbial respiration rates (MRR) and water content between the treatments were not significant. SWR was not correlated with SOM or MRR. A strong correlation between water contents and SWR parameters demonstrated the importance of SWR for water redistribution. At the meso-scale of disc infiltrometry, infiltration rates were reduced by SWR, and were higher under ambient than under elevated [CO2]. This corroborates the tendency of reduced SWR under elevated [CO2] observed at the micro-scale. SWR showed a spatial structure, exhibiting short ranges. SOM and MRR showed no spatial pattern at the scale analyzed, emphasizing that SWR did not contribute to an increase of the long-term terrestrial C sink in response to increased atmospheric [CO2]. [ABSTRACT FROM AUTHOR]

Abstract The terrestrial biogeochemical silicon (Si) cycle may significantly influence the stabilization of soil organic carbon (SOC), and thus plays an important role in regulating the global carbon (C) balance and climate change. Processes involved in Si-enhanced SOC stability at a decadal or centennial scale include protection of SOC through amorphous Si and interactions of Si-iron and Si-aluminum. Strategic manipulation of the Si cycle in terrestrial ecosystems offers a new opportunity to enhance soil C sequestration. Rock powder amendment, establishment of Si-rich plant buffer strips and innovative management practices that return Si-rich biomass materials to soil can be implemented as strategies to enhance soil C sequestration through regulating the terrestrial Si cycle. However, quantifying (i) the contribution of different processes to the enhancement of soil dissolved Si and secondary Si minerals, (ii) the relative importance of different SOC stabilization mechanisms, and (iii) the potential and cost of different measures has not been attempted. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to evaluate the effect of biochars on the bioavailability of di-(2-ethylhexyl) phthalate (DEHP) in two soils using Brassica chinensis L. as an indicator plant. The residual concentrations of DEHP tended to be higher in the biochar-amended soils than in the control soils. They were lower ( p < 0.05) in the high organic carbon content soil (HOC; 2.2%C) than in the low organic carbon content soil (LOC; 0.35%C). The DEHP concentrations in plant shoots grown in the HOC soils were lower than those in the LOC soils ( p < 0.05). Compared to the control, the biochar addition decreased the DEHP concentrations in shoots grown in the LOC soils; whereas there was no significant difference in the HOC soils. Our results showed that soil OC content as well as biochar properties are the key factors influencing the bioavailability of DEHP in soils. [ABSTRACT FROM AUTHOR]

Pollution of water by single antibiotics has been investigated in depth. However, in reality, a wide range of different contaminants is often mixed in the aquatic environment (contaminant cocktail). Here, single and competitive sorption dynamics of ionizable norfloxacin (NOR), sulfamerazine (SMR) and oxytetracycline (OTC) by both pristine and modified biochars were investigated. Sorption kinetics of the three antibiotics was faster in ternary-solute than single-solute system. Sorption efficiency was enhanced in the competitive system for NOR by the pristine biochar, and for OTC by both the pristine biochar and the modified biochar, while SMR sorption by the pristine biochar and the KOH-modified biochar was inhibited. Sorption was governed by electrostatic interactions, π-π EDA and H-bonds for antibiotics sorption by biochar. SMR and OTC sorption by biochar was influenced by cation bridging and surface complexation, respectively. This research finding will guide the development of treatment procedures for water polluted by multiple antibiotics. [ABSTRACT FROM AUTHOR]