Biochar: a synthesis of its agronomic impact beyond carbon sequestration

Biochar has been heralded as an amendment to revitalize degraded soils, improve soil carbon sequestration, increase agronomic productivity, and enter into future carbon trading markets. However, scientific and economic technicalties may limit the ability of biochar to consistently deliver on these expectations. Past research has demonstrated that biochar is part of the black carbon continuum with variable properties due to the net result of production (e.g., feedstock and pyrolysis conditions) and postproduction factors (storage or activation). Therefore, biochar is not a single entity but rather spans a wide range of black carbon forms. Biochar is black carbon, but not all black carbon is biochar. Agronomic benefits arising from biochar additions to degraded soils have been emphasized, but negligible and negative agronomic effects have also been reported. Fifty percent of the reviewed studies reported yield increases after black carbon or biochar additions, with the remainder of the studies reporting alarming decreases to no significant differences. Hardwood biochar (black carbon) produced by traditional methods (kilns or soil pits) possessed the most consistent yield increases when added to soils. The universality of this conclusion requires further evaluation due to the highly skewed feedstock preferences within existing studies. With global population expanding while the amount of arable land remains limited, restoring soil quality to nonproductive soils could be key to meeting future global food production, food security, and energy supplies; biochar may play a role in this endeavor. Biochar economics are often marginally viable and are tightly tied to the assumed duration of agronomic benefits. Further research is needed to determine the conditions under which biochar can provide economic and agronomic benefits and to elucidate the fundamental mechanisms responsible for these benefits.     

The ecological apparency hypothesis and the importance of useful plants in rural communities from northeastern Brazil: an assessment based on use value

The ecological apparency hypothesis in ethnobotanical studies predicts that the apparent plants (i.e., the most easily found in the vegetation) would be the most commonly collected and used by people. To test this hypothesis, it has been used the concept of use value (VU), which measures the relative importance of useful plants for a group of people. However, the use value has got some limitations, including the fact that it does not distinguish "current use" (plants which are effectively used) from "potential use" (well known plants, however not used). Therefore, this study has tested whether the obtained results through three different use value calculations could be useful in testing the ecological apparency hypothesis. These calculations have included the current use value, the potential use value, and the general use value. It has been carried out a vegetation survey and an interview for residents from the rural communities from Barrocas and Cachoeira (Soledade, Paraíba, Brazil). It has been used Spearman's coefficient to correlate phytosociological and ethnobotanical data. It has been observed that phytosociological parameters in Cachoeira were not correlated with any of the use values calculations, except the relationship between the current use value and the relative dominance (r(s)?=?0.57; p?相似文献   

Use of rainwater for non-potable purposes in the Amazon

The Brazilian Amazon has about 69 % of available freshwater in Brazil, an amount that ends up creating the illusion that no lack of water and not lacking in the region, the large supply of this resource becomes a problem when it comes to the Management and Planning Water Resources in the Amazon, according to the wasteful use and lack of maintenance of stocks, compounded by the release of untreated wastewater. Speaking of water conservation programs in the Amazon a few decades ago and still today, with less intensity, is somewhat strange, given the large amount of water available and the culture of abundance. Thus, this research discusses the importance of the use of rainwater for non-potable purposes, since the potential for exploitation, throughout the year, due to this high rainfall in the Amazon region, ranging from, on average, 119.6 mm in months from November to 441.6 mm in March. The methods used for sizing of the reservoir were the Rippl and interactive, and economic viability checking done by the methods of net present value and discounted payback. As a result, there was a volume exceeding 1,000 m³ obtained by the method of Rippl, while the interactive method was a maximum of 75 m³. The economic viability presented fragile as a function of time to return exceeds the useful life of the utilization system for rainwater.     

Continuous flow photo-Fenton treatment of ciprofloxacin in aqueous solutions using homogeneous and magnetically recoverable catalysts

The degradation of ciprofloxacin was studied in aqueous solutions by using a continuous flow homogeneous photo-Fenton process under simulated solar light. The effect of different operating conditions on the degradation of ciprofloxacin was investigated by changing the hydrogen peroxide (0–2.50 mM) and iron(II) sulphate (0–10 mg Fe L^?1) concentrations, as well as the pH (2.8–10), irradiance (0–750 W m^?2) and residence time (0.13–3.4 min) of the process. As expected, the highest catalytic activity in steady state conditions was achieved at acidic pH (2.8), namely 85 % of ciprofloxacin conversion, when maintaining the other variables constant (i.e. 2.0 mg L^?1 of iron(II), 2.50 mM of hydrogen peroxide, 1.8 min of residence time and 500 W m^?2 of irradiance). Additionally, magnetite magnetic nanoparticles (ca. 20 nm of average particle size) were synthesized, characterized and tested as a possible catalyst for this reaction. In this case, the highest catalytic activity was achieved at natural pH, namely a 55 % average conversion of ciprofloxacin in 1.8 min of residence time and under 500 W m^?2. Some of the photocatalytic activity was attributed to Fe²⁺ leaching from the magnetic nanoparticles to the solution.     

The spatial distribution of eubacteria and archaea in sand-clay columns degrading carbon tetrachloride and methanol

The spatial distribution of microbial communities was investigated in anaerobic sand-clay columns fed methanol and carbon tetrachloride (CT). Microbial communities were characterized through analysis of soil samples with denaturing gradient gel electrophoresis (DGGE) and quantitative polymerase chain reaction (qPCR) for archaea and eubacteria. Increasing CT inlet concentrations to 29 microM lead to complete inhibition of methanol consumption in both columns. Although low levels of eubacteria and archaea were initially present in the clay soils in both columns, there was no significant microbial growth over 400 days in the clays beyond the interface with the sand zone. Thus, the potential for increased contaminant attenuation in heterogeneous sand-clay systems through biodegradation in the clay matrix zones may be limited in many systems.     

Characterization of Atrazine-Loaded Biodegradable Poly(Hydroxybutyrate-Co-Hydroxyvalerate) Microspheres

Polyhydroxybutyrate-co-hydroxyvalerate microspheres (PHBV-MS) were prepared as a delivery system for the herbicide atrazine (ATZ). Characterization of the system included investigation of in vitro release properties and genotoxicity. ATZ − PHBV-MS particle diameters showed a size distribution range of 1–13 μm. Differential scanning calorimetry analyses indicated that ATZ was associated with the PHBV microparticles. The release profiles showed a different release behavior for the pure herbicide in solution, as compared with that containing ATZ-loaded PHBV-MS. Korsmeyer–Peppas model analyses showed that atrazine release from the microparticles occurred by a combination of diffusion through the matrix and partial diffusion through water-filled pores of the PHBV microparticles. A Lactuca sativa test result showed that the genotoxicity of ATZ-loaded PHBV-MP was decreased in relation to ATZ alone. The results demonstrate a viable biodegradable herbicide release system using atrazine for agrochemical purposes.     

Soil quality assessment in rice production systems: establishing a minimum data set

Soil quality, as a measure of the soil's capacity to function, can be assessed by indicators based on physical, chemical, and biological properties. Here we report on the assessment of soil quality in 21 rice (Oryza sativa) fields under three rice production systems (semi-direct, pre-germinated, and conventional) on four soil textural classes in the Camaqu? region of Rio Grande do Sul, Brazil. The objectives of our study were: (i) to identify soil quality indicators that discriminate both management systems and soil textural classes, (ii) to establish a minimum data set of soil quality indicators and (iii) to test whether this minimum data set is correlated with yield. Twenty-nine soil biological, chemical, and physical properties were evaluated to characterize regional soil quality. Soil quality assessment was based on factor and discriminant analysis. Bulk density, available water, and micronutrients (Cu, Zn, and Mn) were the most powerful soil properties in distinguishing among different soil textural classes. Organic matter, earthworms, micronutrients (Cu and Mn), and mean weight diameter were the most powerful soil properties in assessing differences in soil quality among the rice management systems. Manganese was the property most strongly correlated with yield (adjusted r2 = 0.365, P = 0.001). The merits of sub-dividing samples according to texture and the linkage between soil quality indicators, soil functioning, plant performance, and soil management options are discussed in particular.     

Bark regeneration and tannin content in Myracrodruon urundeuva Allem?o after simulation of extractive damages��implications to management

Due to the current exploitation and consequent extinction of native medicinal plants around the world, new strategies have been proposed to address the sustainable use of this resource. Accordingly, the goal of this study is to assess the speed of bark regeneration of Myracrodruon urundeuva Allem?o and to compare the tannin content before and after tissue regeneration. Twenty individuals from an area of Caatinga in Caruaru, Pernambuco State (NE Brazil), were selected. To evaluate the speed of bark regeneration, four treatments were established, according to the area of bark removed (10 × 2, 6 × 5, 8 × 5 and 10 × 5 cm), with five replicates (five individuals of M. urundeuva Allem?o) and three treatments of tannin content (bark removed before damage, as regenerated tissue, and non-impacted bark or control). At the end of 23 months of monitoring the regeneration, we found that only seven of the 20 individuals analyzed did not fully heal. No significant correlation between the monthly percent regeneration and average monthly precipitation was found. The tannin content varied according to the quantified tissue (after damage, regenerated and control) as well as between damage classes (20 cm(2)-41.64 to 63.53 mg; 30 cm(2)-49.25 to 67.54 mg; 40 cm(2)-31.69 to 67.44 mg; 50 cm(2)-34.08 to 48.53 mg). Despite the variations found, there was no significant difference between the measurement periods (p > 0.05) or damage classes (p > 0.05). The results showed that the regeneration rate was higher in individuals belonging to the 10 × 2 and 10 × 5 cm groups and that there is no correlation between precipitation and regeneration speed. Tannin levels did not vary significantly in the tissues before damage and after regeneration.     

Applications of chitosan to the roots and shoots change the accumulation pattern of cadmium in Talinum patens (Talinaceae) cuttings

Environmental Science and Pollution Research - Chitosan induces tolerance to abiotic stress agents in plants. However, studies on the different application forms of this biopolymer are limited....