Environmental monitoring plays a central role in diagnosing climate and management impacts on natural and agricultural systems; enhancing the understanding of hydrological processes; optimizing the ...allocation and distribution of water resources; and assessing, forecasting, and even preventing natural disasters. Nowadays, most monitoring and data collection systems are based upon a combination of ground-based measurements, manned airborne sensors, and satellite observations. These data are utilized in describing both small- and large-scale processes, but have spatiotemporal constraints inherent to each respective collection system. Bridging the unique spatial and temporal divides that limit current monitoring platforms is key to improving our understanding of environmental systems. In this context, Unmanned Aerial Systems (UAS) have considerable potential to radically improve environmental monitoring. UAS-mounted sensors offer an extraordinary opportunity to bridge the existing gap between field observations and traditional air- and space-borne remote sensing, by providing high spatial detail over relatively large areas in a cost-effective way and an entirely new capacity for enhanced temporal retrieval. As well as showcasing recent advances in the field, there is also a need to identify and understand the potential limitations of UAS technology. For these platforms to reach their monitoring potential, a wide spectrum of unresolved issues and application-specific challenges require focused community attention. Indeed, to leverage the full potential of UAS-based approaches, sensing technologies, measurement protocols, postprocessing techniques, retrieval algorithms, and evaluation techniques need to be harmonized. The aim of this paper is to provide an overview of the existing research and applications of UAS in natural and agricultural ecosystem monitoring in order to identify future directions, applications, developments, and challenges.
While a large-scale soil amendment of biochars continues to receive interest for enhancing crop yields and to remediate contaminated sites, systematic study is lacking in how biochar properties ...translate into purported functions such as heavy metal sequestration. In this study, cottonseed hulls were pyrolyzed at five temperatures (200, 350, 500, 650, and 800 °C) and characterized for the yield, moisture, ash, volatile matter, and fixed carbon contents, elemental composition (CHNSO), BET surface area, pH, pHpzc, and by ATR-FTIR. The characterization results were compared with the literature values for additional source materials: grass, wood, pine needle, and broiler litter-derived biochars with and without post-treatments. At respective pyrolysis temperatures, cottonseed hull chars had ash content in between grass and wood chars, and significantly lower BET surface area in comparison to other plant source materials considered. The N:C ratio reached a maximum between 300 and 400 °C for all biomass sources considered, while the following trend in N:C ratio was maintained at each pyrolysis temperature: wood cottonseed hull ≈ grass ≈ pine needle broiler litter. To examine how biochar properties translate into its function as a heavy metal (NiII, CuII, PbII, and CdII) sorbent, a soil amendment study was conducted for acidic sandy loam Norfolk soil previously shown to have low heavy metal retention capacity. The results suggest that the properties attributable to the surface functional groups of biochars (volatile matter and oxygen contents and pHpzc) control the heavy metal sequestration ability in Norfolk soil, and biochar selection for soil amendment must be made case-by-case based on the biochar characteristics, soil property, and the target function.
Contamination of soil interstitial waters by labile heavy metals such as Cu(II), Cd(II), and Ni(II) is of worldwide concern. Carbonaceous materials such as char and activated carbon have received ...considerable attention in recent years as soil amendment for both sequestering heavy metal contaminants and releasing essential nutrients like sulfur. Information is currently lacking in how aging impacts the integrity of biochars as soil amendment for both agricultural and environmental remediation purposes. Major contributors to biochar aging in soils are: sorption of environmental constituents, especially natural organic matter (NOM), and oxidation. To investigate the impact of NOM and organic fractions of chars, we employed broiler litter-derived chars and steam-activated carbons that underwent varying degrees of carbonization, in the presence and absence of NOM having known carboxyl contents. For aging by oxidation, we employed phosphoric acid activated carbons that underwent varying degrees of oxidation during activation. The results suggest that the organic fractions of biochars, and NOM having high carboxyl contents can mobilize Cu(II) retained by alkaline soil. Base treatment of broiler litter-derived char formed at low pyrolysis temperature (350°C) improved the immobilization of all heavy metals investigated, and the extent of immobilization was similar to, or slightly greater than pecan shell-derived phosphoric acid activated carbons. Portions of total sulfur were released in soluble form in soil amended with broiler litter-derived carbons, but not pecan shell-derived phosphoric acid activated carbons.
Biochar has been recently 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 technicalities 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 post-production 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 following 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 a vital 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 specific conditions under which biochar can provide real economic and agronomic benefits and to elucidate the fundamental mechanisms responsible for these benefits.
Chars, a form of environmental black carbon resulting from incomplete burning of biomass, can immobilize organic contaminants by both surface adsorption and partitioning mechanisms. The predominance ...of each sorption mechanism depends upon the proportion of organic to carbonized fractions comprising the sorbent. Information is currently lacking in the effectiveness of char amendment for heavy metal immobilization in contaminated (e.g., urban and arms range) soils where several metal contaminants coexist. The present study employed sorbents of a common biomass origin (broiler litter manure) that underwent various degrees of carbonization (chars formed by pyrolysis at 350 and 700 degrees C and steam-activated analogues) for heavy metal (Cd(II), Cu(II), Ni(II), and Pb(II)) immobilization in water and soil. ATR-FTIR, (1)H NMR, and Boehm titration results suggested that higher pyrolysis temperature and activation lead to the disappearance (e.g., aliphatic -CH(2) and -CH(3)) and the formation (e.g., C-O) of certain surface functional groups, portions of which are leachable. Both in water and in soil, pH increase by the addition of basic char enhanced the immobilization of heavy metals. Heavy metal immobilization resulted in nonstoichiometric release of protons, that is, several orders of magnitude greater total metal concentration immobilized than protons released. The results suggest that with higher carbonized fractions and loading of chars, heavy metal immobilization by cation exchange becomes increasingly outweighed by other controlling factors such as the coordination by pi electrons (C=C) of carbon and precipitation.
Bio-oil and bio-char were produced from corn cobs and corn stover (stalks, leaves and husks) by fast pyrolysis using a pilot scale fluidized bed reactor. Yields of 60% (mass/mass) bio-oil (high ...heating values are ∼20
MJ
kg
−1, and densities >1.0
Mg
m
−3) were realized from both corn cobs and from corn stover. The high energy density of bio-oil, ∼20–32 times on a per unit volume basis over the raw corn residues, offers potentially significant savings in transportation costs particularly for a distributed “farm scale” bio-refinery system. Bio-char yield was 18.9% and 17.0% (mass/mass) from corn cobs and corn stover, respectively. Deploying the bio-char co-product, which contains most of the nutrient minerals from the corn residues, as well as a significant amount of carbon, to the land can enhance soil quality, sequester carbon, and alleviate environmental problems associated with removal of crop residues from fields.
In this work, extractive desulfurization of model fuel containing dibenzothiophene (DBT) and thiophene (Th) as sulfur compounds was carried out using 16 different Deep Eutectic Solvents (DES) based ...on polyethylene glycol (PEG) and its precursors. The aim of this study is the reduction of the sulfur content of fuels below the environmental regulation (10 ppm), using PEG-based DES as low-cost extraction media under mild conditions and to compare their extractive performance with that of PEG alone, which by itself is a green solvent. For that purpose, 7 different quaternary ammonium and phosphonium salts were combined with four different molecular weight grades of PEG and PEG precursors such as ethylene glycol and triethylene glycol. The best results were obtained for the DES composed of tetrabutylammonium chloride (TBAC) and PEG400, which showed that it is possible to achieve, in single extraction step, 85% and 68% of extraction efficiency, and deep desulfurization in 2 and 3 cycles, for DBT and Th, respectively. In addition, this DES is not soluble in the model fuel and its extraction capacity is independent on the starting sulfur concentration. Finally, after being reused six times, TBAC:PEG400 DES still maintained 53% and 17% of its capacity, for DBT and Th removal, respectively, and after a regeneration step the performance of the DES was fully recovered.
Coffee is one of the world's most traded agricultural products. Modeling studies have predicted that climate change will have a strong impact on the suitability of current cultivation areas, but ...these studies have not anticipated possible mitigating effects of the elevated atmospheric CO2 because no information exists for the coffee plant. Potted plants from two genotypes of Coffea arabica and one of C. canephora were grown under controlled conditions of irradiance (800 μmol m(-2) s(-1)), RH (75%) and 380 or 700 μL CO2 L(-1) for 1 year, without water, nutrient or root development restrictions. In all genotypes, the high CO2 treatment promoted opposite trends for stomatal density and size, which decreased and increased, respectively. Regardless of the genotype or the growth CO2, the net rate of CO2 assimilation increased (34-49%) when measured at 700 than at 380 μL CO2 L(-1). This result, together with the almost unchanged stomatal conductance, led to an instantaneous water use efficiency increase. The results also showed a reinforcement of photosynthetic (and respiratory) components, namely thylakoid electron transport and the activities of RuBisCo, ribulose 5-phosphate kinase, malate dehydrogenase and pyruvate kinase, what may have contributed to the enhancements in the maximum rates of electron transport, carboxylation and photosynthetic capacity under elevated CO2, although these responses were genotype dependent. The photosystem II efficiency, energy driven to photochemical events, non-structural carbohydrates, photosynthetic pigment and membrane permeability did not respond to CO2 supply. Some alterations in total fatty acid content and the unsaturation level of the chloroplast membranes were noted but, apparently, did not affect photosynthetic functioning. Despite some differences among the genotypes, no clear species-dependent responses to elevated CO2 were observed. Overall, as no apparent sign of photosynthetic down-regulation was found, our data suggest that Coffea spp. plants may successfully cope with high CO2 under the present experimental conditions.
Acid weathered soils often require lime and fertilizer application to overcome nutrient deficiencies and metal toxicity to increase soil productivity. Slow‐pyrolysis chicken manure biochars, produced ...at 350 and 700°C with and without subsequent steam activation, were evaluated in an incubation study as soil amendments for a representative acid and highly weathered soil from Appalachia. Biochars were mixed at 5, 10, 20, and 40 g kg−1 into a Gilpin soil (fine‐loamy, mixed, active, mesic Typic Hapludult) and incubated in a climate‐controlled chamber for 8 wk, along with a nonamended control and soil amended with agronomic dolomitic lime (AgLime). At the end of the incubation, soil pH, nutrient availability (by Mehlich‐3 and ammonium bicarbonate diethylene triamine pentaacetic acid AB‐DTPA extractions), and soil leachate composition were evaluated. Biochar effect on soil pH was process‐ and rate‐dependent. Biochar increased soil pH from 4.8 to 6.6 at the high application rate (40 g kg−1), but was less effective than AgLime. Biochar produced at 350°C without activation had the least effect on soil pH. Biochar increased soil Mehlich‐3 extractable micro‐ and macronutrients. On the basis of unit element applied, increase in pyrolysis temperature and biochar activation decreased availability of K, P, and S compared to nonactivated biochar produced at 350°C. Activated biochars reduced AB‐DTPA extractable Al and Cd more than AgLime. Biochar did not increase NO3− in leachate, but increased dissolved organic carbon, total N and P, PO43−, SO42−, and K at high application rate (40 g kg−1). Risks of elevated levels of dissolved P may limit chicken manure biochar application rate. Applied at low rates, these biochars provide added nutritional value with low adverse impact on leachate composition.
For the first time, two distinct trends are clearly evidenced for the enthalpies and entropies of vaporization along the CnmimNtf2 ILs series. The trend shifts observed for Δ(l)(g)H(m)(o) and ...Δ(l)(g)S(m)(o), which occur at C6mimNtf2, are related to structural modifications. The thermodynamic results reported in the present article constitute the first quantitative experimental evidence of the structural percolation phenomenon and make a significant contribution to better understanding of the relationship among cohesive energies, volatilities, and liquid structures of ionic liquids. A new Knudsen effusion apparatus, combined with a quartz crystal microbalance, was used for the high-accuracy volatility study of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide series (CnmimNtf2, where n = 2, 3, 4, 5, 6, 7, 8, 10, 12). Vapor pressures in the (450–500) K temperature range were measured, and the molar standard enthalpies, entropies, and Gibbs energies of vaporization were derived. The thermodynamic parameters of vaporization were reported, along with molecular dynamic simulations of the liquid phase structure, allowing the establishment of a link between the thermodynamic properties and the percolation phenomenon in ILs.
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