Accumulation In Surface Research Articles

Methodology for the Identification of Dust Accumulation Levels in Photovoltaic Panels Based in Heuristic-Statistical Techniques

The use of renewable energies is increasing around the world in order to deal with the environmental and economic problems related with conventional generation. In this sense, photovoltaic generation is one of the most promising technologies because of the high availability of sunlight, the easiness of maintenance, and the reduction in the costs of installation and production. However, photovoltaic panels are elements that must be located outside in order to receive the sun radiation and transform it into electricity. Therefore, they are exposed to the weather conditions and many environmental factors that can negatively affect the output delivered by the system. One of the most common issues related to the outside location is the dust accumulation in the surface of the panels. The dust particles obstruct the passage of the sunlight, reducing the efficiency of the generation process and making the system prone to experimental long-term faults. Thus, it is necessary to develop techniques that allow us to assess the level of dust accumulation in the panel surface in order to schedule a proper maintenance and avoid losses associated with the reduction of the delivered power and unexpected faults. In this work, we propose a methodology that uses a machine learning approach to estimate different levels of dust accumulation in photovoltaic panels. The developed method takes the voltage, current, temperature, and sun radiance as inputs to perform a statistical feature extraction that describes the behavior of the photovoltaic system under different dust conditions. In order to retain only the relevant information, a genetic algorithm works along with the principal component analysis technique to perform an optimal feature selection. Next, the linear discrimination analysis is carried out using the optimized dataset to reduce the problem dimensionality, and a multi-layer perceptron neural network is implemented as a classifier for discriminating among three different conditions: clean surface, slight dust accumulation, and severe dust accumulation. The proposed methodology is implemented using real signals from a photovoltaic installation, proving to be effective not only to determine if a dust accumulation condition is present but also when maintenance actions must be performed. Moreover, the results demonstrate that the accuracy of the proposed method is always above 94%.

Experimental study on simultaneous heat-water-salt migration of bare soil subjected to evaporation

Evaporation in shallow soil has a great influence on the properties of surface soil. Therefore, under evaporation conditions, research on the rule and mechanism of heat-water-salt migration in surface soil has great significance for engineering geology and environmental science. In this study, with full consideration of the initial water content, salt content, atmospheric temperature, and groundwater supply, a series of indoor evaporation tests were performed on shallow saline soil to observe the heat-water-salt migration process. In addition, before and after the evaporation test, the soil microstructure at different depths was observed and analysed to explore the influence of heat-water-salt migration on the soil. The results show that during the evaporation process, salt carried by water migrates in the soil column, and the water-vapour phase transition causes salt accumulation, which also leads to the electrical conductivity (EC) profile showing a V-shape, and the salt content in the middle of the soil column is lower than that in the end. In addition, high atmospheric temperature significantly reduces the surface water content but alleviates salt accumulation. Under the condition of groundwater supplementation, the salt accumulation in the soil column surface is rapid. By observing the microstructure, it can be seen that a flocculent structure exists in the soil before evaporation. After evaporation, the surface microstructure changes significantly, and pores and salt crystals can be observed. The results provide a reference for understanding heat-water-salt transport in arid areas.

Chemical surface modification of beaded activated carbon: A strategy to inhibit heel accumulation from VOC

This study elucidates the factors responsible for the deterioration of beaded activated carbon (BAC), used in the abatement of volatile organic compounds that stem from painting processes in industries. In practice, continuous use of adsorbents during periodic adsorption–desorption results in the formation of heel (non-desorbable polymeric complex) in its pore structures, rendering the adsorbent eventually unusable. Here, the adsorption–desorption characteristics of VOCs from porous BAC are investigated, and an effective surface modification strategy is developed to impede heel formation and extend the operational life of the BAC. This modification protocol increases porosity by up-to 55 % and modifies the functional groups on the BAC surface without altering its structural integrity. Consequently, the adsorption capacity of the BAC increased by nearly 38% while decreasing the peak desorption temperature by as much as 50 °C due to lowered adsorption strength. Additionally, to provide mechanistic insights, the resultant changes in porosity, surface morphology, and adsorption–desorption characteristics of the BAC are investigated by N2 physisorption, SEM, TGA, and DRIFTS. Finally, cyclic adsorption–desorption studies conducted under conditions mirroring the industrial setup proved that the percentage heel accumulation in surface modified BAC is significantly lower (≤ 3%) compared to unmodified BAC.

Enhancement of continuous flow cooling using hydrophobic surface treatment

This study examined the effect of hydrophobic-surface treatment of tubular heat exchangers on cooling of viscous foods, namely sweet potato puree, banana puree, and cheese sauce. For the foods tested, cooling efficiency was compared between two identical tube-in-tube stainless-steel heat exchangers either untreated or treated with a hydrophobic chemical coating, Aculon. The average overall heat transfer coefficient, U, was calculated and compared between the two heat exchangers. Cooling of banana puree was improved when using the Aculon-treated heat exchanger, revealing a U of 115 W/(m 2 ·K) compared to 105 W/(m 2 ·K) for the untreated heat exchanger. Cheese sauce cooling was influenced the most, with a U value of 187 W/(m 2 ·K) for the Aculon-treated heat exchanger, compared to 133 W/(m 2 ·K) for the untreated case. Finally, Aculon-treatment showed no difference in the cooling of sweet potato puree, with U of 193 W/(m 2 ·K) and 195 W/(m 2 ·K) for the untreated and the Aculon-treated heat exchangers, respectively. • Enhancement of the cooling efficiency of viscous foods • More uniform thermal treatment of viscous products during cooling • Reduction of product accumulation in the heat-exchanger surface • Potential improvement of the CIP process by reducing time and chemical use

A high-efficiency salt-rejecting solar evaporator with optimized porous structure for continuous solar desalination

Solar interfacial evaporation technology has been advanced rapidly in recent years due to its high efficiency and environment friendliness. However, the salt accumulation in the evaporation surface severely limits the stable evaporation performance of interfacial evaporator, especially for high-salinity brine. Here, we prepared a salt-rejecting solar evaporator with carbon blacks deposited on the super-hydrophilic polystyrene/lignocellulose (PS/LF) skeleton. By analyzing the factors that affect antifouling ability of evaporators, like the skeleton porosity and pore size, we obtained a continuous salt-rejecting porous structure with the porosity of about 70.4% and the pore size of 150–300 μm. This evaporator with optimized porous structure could achieve continuous salt rejection in the high-salinity environment (15% NaCl), and exhibit a stable evaporation rate of 1.90 kg·m−2·h−1 and a high evaporation efficiency of 85.5% under a 1.5-sun irradiation. The good salt-rejecting property comes from the high porosity of evaporator which means numerous water channels to promote salt exchange, and large pores which means large hydraulic diameter and small tortuosity of pore channels to shorten the migration distance of salt ions back to bulk water. These two factors together promote the rapid reflux of salt ions, enabling the continuously self-cleaning of evaporator. Given the salt accumulation on the surface could contaminate the sunlight absorption, the high evaporation efficiency of the evaporator benefits from the salt rejecting. At the same time, the thermal insulation structure which was used to support the evaporator further ensures the high evaporation efficiency.

Priorities of Ecologically Oriented Economic Development of the Agricultural Sector

The article considers the main factors of anthropogenic impact that affect the environment; a number of major environmental challenges in the agricultural sector that affect the stable economic growth of agricultural production are identified. It is established that the transformation processes in the life of society are contradictory in relation to the interaction of nature and society, significantly exacerbate the degrading changes in the environment. Violations of the technology of cultivation, storage and application of mineral fertilizers, their properties and chemical composition, imperfection of their use have led to increased negative impact on certain components of the biosphere, soil environment, the environment and man. Practice shows that intensive technologies for growing field crops increase the possibility of soil contamination with fertilizer residues, pesticides, herbicides and other toxicants. The presence of toxic substances in the soil is accompanied by their accumulation in surface and groundwater. This is one of the main environmental factors that affect the quality of products and soil quality. Ensuring environmental safety should be decided in the light of world experience, taking into account the specifics of the country’s geographical location, ensuring that the economic interests of agricultural producers are aligned with the environmental requirements of environmental protection. In view of this, the problem of increasing the efficiency of agricultural production through its greening, starting with the organization of the rational use of natural resources as the main means of production, becomes especially relevant. An important element of economic activity of agricultural enterprises is to take into account environmental factors in order to increase the economic efficiency of agricultural production and preserve ecosystems.

Evaluation of the effectiveness of in situ stabilization in the field aged arsenic-contaminated soil: Chemical extractability and biological response.

The effectiveness of in situ stabilization in the long-term As-contaminated soil was assessed. In situ stabilization of As was conducted through a Fe-based sorbent amendment. Chemical extractability of As was first determined by solubility/bioavailability research consortium extraction method and any change in human health risk through oral ingestion was characterized. Also, nonspecifically bound As in soil was determined by five-step sequential extraction. The results indicate that such extractable fractions of As decreased, and consequently risk through oral ingestion decreased probably due to hematite transformed from both the goethite in the original soil and the Fe-based sorbent, which was identified through the X-ray absorption spectroscopy. In ecotoxicity test with Hordeum vulgare, root and shoot elongation and germination rate decreased which was contrary to the chemical extraction data. Such increase in As toxicity is because of increased exchangeable Ca2+ concentration causing As accumulation in the membrane surface of H. vulgare. Also, adsorption of phosphorus onto the Fe-based sorbent decreased available phosphorus concentration causing phosphorus deficiency for growth. Our results demonstrate that the effectiveness of in situ stabilization should be evaluated by means of both chemical extractability and biological response, as chemical analysis alone may not be sufficient to assess the ecotoxicity.

Long-term fertilization effects on soil organic carbon sequestration in an Inceptisol

Limited information is available on long-term fertilization impacts on soil organic carbon (SOC) sequestration in deep soils and C pools within bulk soils and aggregates. Hence, the major objectives of this study were to evaluate long-term (44 years) fertilization impacts on: (i) soil aggregation, labile and recalcitrant C pools within bulk soils and aggregates and (ii) deep soil C accumulation versus sequestration. Treatments were: no mineral fertilizer or manure (control), 100% recommended dose of nitrogen (N), N and phosphorus (NP), N, P and potassium (NPK), 150% recommended NPK (150% NPK), and NPK + farmyard manure (FYM) (NPK + FYM). Labile C, recalcitrant C, total SOC and glomalin in bulk soils and their aggregates were determined in the 0–15 and 15–30 cm soil layers. In addition, total SOC, labile and recalcitrant C contents were measured in the 30–60 and 60–90 cm soil layers. Results revealed that C accumulation and sequestration in NPK + FYM over control plots were 0.74 and 0.22 Mg C ha−1 yr−1, respectively, in 0–90 cm soil layer with >50% of the accumulated C in deep soil layers (30–90 cm). In 0–15 cm layer, despite NPK + FYM and NPK plots had similar amounts of soil macroaggregates, microaggregates were 27% higher with NPK + FYM than NPK, causing higher aggregate stability. Plots with NPK and NPK + FYM had more labile: recalcitrant C ratios in bulk soils than control, NP and N plots. The NPK + FYM plots also had highest recalcitrant C pools within macro- and microaggregates. Glomalin was generally positively correlated with all labile C pools in both soil layers. Additionally, mean weight diameter (MWD) was positively correlated with aggregate-associated C and glomalin within bulk soils. Overall, NPK + FYM management practice not only had higher C accumulation and sequestration in surface and deep soils, but also had better aggregation and ∼26% greater carbon management index than NPK in soil surface and hence should be adopted.

Metabolic differentiation of surface and invasive cells of yeast colony biofilms revealed by gene expression profiling

BackgroundYeast infections are often connected with formation of biofilms that are extremely difficult to eradicate. An excellent model system for deciphering multifactorial determinants of yeast biofilm development is the colony biofilm, composed of surface (“aerial”) and invasive (“root”) cells. While surface cells have been partially analyzed before, we know little about invasive root cells. In particular, information on the metabolic, chemical and morphogenetic properties of invasive versus surface cells is lacking. In this study, we used a new strategy to isolate invasive cells from agar and extracellular matrix, and employed it to perform genome wide expression profiling and biochemical analyses of surface and invasive cells.ResultsRNA sequencing revealed expression differences in 1245 genes with high statistical significance, indicating large genetically regulated metabolic differences between surface and invasive cells. Functional annotation analyses implicated genes involved in stress defense, peroxisomal fatty acid β-oxidation, autophagy, protein degradation, storage compound metabolism and meiosis as being important in surface cells. In contrast, numerous genes with functions in nutrient transport and diverse synthetic metabolic reactions, including genes involved in ribosome biogenesis, biosynthesis and translation, were found to be important in invasive cells. Variation in gene expression correlated significantly with cell-type specific processes such as autophagy and storage compound accumulation as identified by microscopic and biochemical analyses. Expression profiling also provided indications of cell-specific regulations. Subsequent knockout strain analyses identified Gip2p, a regulatory subunit of type 1 protein phosphatase Glc7p, to be essential for glycogen accumulation in surface cells.ConclusionsThis is the first study reporting genome wide differences between surface and invasive cells of yeast colony biofilms. New findings show that surface and invasive cells display very different physiology, adapting to different conditions in different colony areas and contributing to development and survival of the colony biofilm as a whole. Notably, surface and invasive cells of colony biofilms differ significantly from upper and lower cells of smooth colonies adapted to plentiful laboratory conditions.

Iron-mediated mineralogical control of organic matter accumulation in tropical soils

Tropical forest soils contribute disproportionately to the poorly-characterized and persistent deep soil carbon (C) pool. These soils, highly-weathered and often extending one to two meters in depth, may contain an abundance of iron-(Fe) bearing mineral phases. Short-range-order (SRO) minerals are of particular interest due to their high reactive surface areas and capacity for soil C stabilization through sorption or co-precipitation. We hypothesized that SRO minerals might serve as primary contributors to soil C accumulation and storage in surface (0–20cm) and subsurface (50–80cm) soils of the Luquillo Critical Zone Observatory (LCZO) in northeast Puerto Rico. Oxisol and Inceptisol soils obtained from 20 quantitative soil pits, stratified across quartz-dominated granodiorite and clay-rich volcaniclastic parent materials, were subjected to selective dissolution procedures to extract Fe-C associations: sodium pyrophosphate (PP) to isolate colloidal or dispersable Fe, HCl-hydroxylamine (HH) and ammonium oxalate (AO) to isolate SRO Fe, and inorganic dithionite-HCl (DH) to isolate more crystalline pedogenic Fe. Pyrophosphate extraction of colloidal or dispersable Fe also extracted the greatest concentrations of soluble C across all samples. Dissolved molar C:Fe ratios >1 observed solely in the PP extracts indicated the presence of organic-rich non-sorptive associations, the stability of which may have stronger control on accumulation of total soil C in these soils than those of extractable SRO and pedogenic Fe. Pedogenic and SRO Fe phases were the dominant extractable minerals in both soil types, at the surface and at depth, and notably, correlated well with extracted C. This suggests that these phases are strongly associated with a smaller, but substantial, fraction of total soil C. Direct observations of the limited extractability of soil C (<50% in surface soils) during selective dissolution of Fe and the lack of correlations between extractable Fe minerals and total soil C concentrations did not support the common hypothesis that SRO mineral phases provide a dominant mechanism for soil C accumulation. Instead, SRO phases may control only a fraction of total soil C, and non-extractable Fe-bearing minerals and non-sorptive mechanisms may play more important roles than previously thought.

Rinsing effect of 60% bay leaf (Syzygium polyanthum wight) aqueous decoction in inhibiting the accumulation of dental plaque during fixed orthodontic treatment

Background: Fixed orthodontic appliance patients have a high risk to increasing plaque accumulation in tooth surface due to the presence of fixed appliance components. Using mouthwash with antibacterial agent from herbal material can control dental plaque accumulation. Bay leaf (BL) contains active compounds such as essential oil, tannin and flavonoid that have been known as an antibacterial agent. Purpose: The purpose of this study was to determine the effect of rinsing with 60% of BL aqueous decoction to the accumulation of dental plaque in fixed orthodontic appliance patients. Method: This research was an experimental clinical research with pretest and post-test control group design conducted on 20 subjects with age ranged between 18-25 years old. All subjects were undergoing the last stage (finishing) of fixed active orthodontic treatment. The subjects were instructed to rinse with 60% of BL aqueous decoction and 0.2% chlorhexidine as a control. Wash out period that needed between rinsing with 60% of BL aqueous decoction and rinsing with 0.2% chlorhexidine was 7 days. Each mouthwash used routinely for 7 days with same duration and intensity. Plaque scoring was measured before and after each treatment using Orthodontic Plaque Index (OPI). Result: One-way Anova test showed that there was a significant difference in the plaque index before and after treatment between the group of rinsing with 60% of BL aqueous decoction and group of rinsing with chlorhexidine (p&lt;0.05). Conclusion: Rinsing with 60% BL aqueous decoction can decrease the accumulation of dental plaque in fixed orthodontic appliance patients.

Effect of crack opening and recovery on chloride penetration into reinforced concrete hollow piles

This study explores the chloride penetration characteristics of reinforced concrete (RC) hollow piles. Special splitting tests were designed to produce different crack widths in the inner and outer surfaces of RC hollow piles. The cracked specimens were then immersed in 5 % NaCl solution for 180 days. The chloride concentration profiles in the cracked zones were obtained by potentiometric titration. This study indicates that the rate of chloride accumulation in the inner pile surface is faster than that in the outer surface for the same exposure time. This may be attributed to differences in the material compositions of the inner and outer surfaces, which are caused by centrifugal processing during specimen preparation. The critical value for V-shaped cracks on the outer surface of RC hollow piles was found to be around 70 µm; however, a critical value was absent for cracks on the inner surface because these present parallel-wall characteristic. In addition, the characteristics of crack development and recovery in the inner and outer pile surfaces were evaluated. The analysis indicates that the depth at which chloride affects the concrete significantly increases with the crack-recovery rate for the apparent crack widths around 130 µm on the outer surface of the concrete layer.

Nitrate Accumulation and Leaching in Surface and Ground Water Based on Simulated Rainfall Experiments.

To evaluate the process of nitrate accumulation and leaching in surface and ground water, we conducted simulated rainfall experiments. The experiments were performed in areas of 5.3 m2 with bare slopes of 3° that were treated with two nitrogen fertilizer inputs, high (22.5 g/m2 NH4NO3) and control (no fertilizer), and subjected to 2 hours of rainfall, with. From the 1st to the 7th experiments, the same content of fertilizer mixed with soil was uniformly applied to the soil surface at 10 minutes before rainfall, and no fertilizer was applied for the 8th through 12th experiments. Initially, the time-series nitrate concentration in the surface flow quickly increased, and then it rapidly decreased and gradually stabilized at a low level during the fertilizer experiments. The nitrogen loss in the surface flow primarily occurred during the first 18.6 minutes of rainfall. For the continuous fertilizer experiments, the mean nitrate concentrations in the groundwater flow remained at less than 10 mg/L before the 5th experiment, and after the 7th experiment, these nitrate concentrations were greater than 10 mg/L throughout the process. The time-series process of the changing concentration in the groundwater flow exhibited the same parabolic trend for each fertilizer experiment. However, the time at which the nitrate concentration began to change lagged behind the start time of groundwater flow by approximately 0.94 hours on average. The experiments were also performed with no fertilizer. In these experiments, the mean nitrate concentration of groundwater initially increased continuously, and then, the process exhibited the same parabolic trend as the results of the fertilization experiments. The nitrate concentration decreased in the subsequent experiments. Eight days after the 12 rainfall experiments, 50.53% of the total nitrate applied remained in the experimental soil. Nitrate residues mainly existed at the surface and in the bottom soil layers, which represents a potentially more dangerous pollution scenario for surface and ground water. The surface and subsurface flow would enter into and contaminate water bodies, thus threatening the water environment.

Biomass production and soil organic carbon accumulation in a free water surface constructed wetland treating agricultural wastewater in North Eastern Italy

Free water surface constructed wetlands (FWSs) play an important role in wastewater pollutants removal and, at the same time, vegetated wetlands can act as carbon sinks.In this study we measured biomass production and soil carbon content variations over five years in a FWS with fluctuating hydroperiod treating agricultural drainage water to evaluate its role in the carbon dioxide cycle.During the study flooding occurred with a yearly average of 28 days. Annual dry matter production, from 2008 to 2011, ranged between 50 and 60Mgha−1. The highest C storage was concentrated in the belowground biomass. 83% of total belowground biomass was measured in the 0–20cm soil layer. During the 2007–2012 period the organic carbon (OC) concentration in the 0–20cm soil layer slightly increased from 12.3 to 13.1gkg−1 and bulk density from 1.38 to 1.66Mgm−3. In the 20–50cm soil layer, monitored only in 2009 and 2012, OC concentration was lower and steady (8.8gkg−1). The total soil C accumulation in the five years was 110.73Mgha−1 of equivalent CO2(eq). Given the positive C balance FWSs can be considered a CO2 sink.

Soil fauna community in the black soil of Northeast China under different tillage systems

Soil fauna is an important component in soil ecosystems. This study tested whether conservation tillage or conventional tillage of a black soil (Udic Mollisol) field in Northeast China could affect its soil fauna communities. Two different conservation tillage systems, no-tillage (NT) and reduced tillage (RT), as well as a conventional rotary tillage system (CT), were chosen for this study. There were 4562 individuals isolated from this study, which included two orders and 35 families. Acariformes was the most abundant family and represented 91.56% of the total faunal abundance. The abundance and the number of faunal families were higher in conservation tillage systems than in the CT. The RT system had the highest individual number of soil fauna among three tillage methods. The faunal accumulation in the soil surface also was significantly higher in the two conservation tillage systems than in the CT. Our results indicate that the conservation tillage systems could protect the soil fauna in the soil ecosystem better than the CT.

Millennial-scale versus long-term dynamics in the surface and subsurface of the western North Atlantic Subtropical Gyre during Marine Isotope Stage 5

Subtropical Gyres are an important constituent of the ocean–atmosphere system due to their capacity to store vast amounts of warm and saline waters. Here we decipher the sensitivity of the (sub)surface North Atlantic Subtropical Gyre with respect to orbital and millennial scale climate variability between ~140 and 70ka, Marine Isotope Stage (MIS) 5. Using (isotope) geochemical proxy data from surface and thermocline dwelling foraminifers from Blake Ridge off the west coast of North America (ODP Site 1058) we show that the oceanographic development at subsurface (thermocline) level is substantially different from the surface ocean.Most notably, surface temperatures and salinities peak during the penultimate deglaciation (Termination II) and early MIS 5e, implying that subtropical surface ocean heat and salt accumulation might have resulted from a sluggish northward heat transport. In contrast, maximum thermocline temperatures are reached during late MIS 5e when surface temperatures are already declining. We argue that the subsurface warming originated from intensified Ekman downwelling in the Subtropical Gyre due to enhanced wind stress.During MIS 5a-d a tight interplay of the subtropical upper ocean hydrography to high latitude millennial-scale cold events can be observed. At Blake Ridge, the most pronounced of these high latitude cold events are related to surface warming and salt accumulation in the (sub)surface. Similar to Termination II, heat accumulated in the Subtropical Gyre probably due to a reduced Atlantic Meridional Overturning Circulation. Additionally, a southward shift and intensification of the subtropical wind belts lead to a decrease of on-site precipitation and enhanced evaporation, coupled to intensified gyre circulation. Subsequently, the northward advection of this warm and saline water likely contributed to the fast resumption of the overturning circulation at the end of these high latitude cold events.

Soil water and salt distribution under furrow irrigation of saline water with plastic mulch on ridge

Furrow irrigation when combined with plastic mulch on ridge is one of the current uppermost water-saving irrigation technologies for arid regions. The present paper studies the dynamics of soil water-salt transportation and its spatial distribution characteristics under irrigation with saline water in a maize field experiment. The mathematical relationships for soil salinity, irrigation amount and water salinity are also established to evaluate the contribution of the irrigation amount and the salinity of saline water to soil salt accumulation. The result showed that irrigation with water of high salinity could effectively increase soil water content, but the increment is limited comparing with the influence from irrigation amount. The soil water content in furrows was higher than that in ridges at the same soil layers, with increments of 12.87% and 13.70% for MMF9 (the treatment with the highest water salinity and the largest amount of irrigation water) and MMF1 (the treatment with the lowest water salinity and the least amount of irrigation water) on 27 June, respectively. The increment for MMF9 was gradually reduced while that for MMF1 increased along with growth stages, the values for 17 August being 2.40% and 19.92%, respectively. Soil water content in the ridge for MMF9 reduced gradually from the surface layer to deeper layers while the surface soil water content for MMF1 was smaller than the contents below 20 cm at the early growing stage. Soil salinities for the treatments with the same amount of irrigation water but different water salinity increased with the water salinity. When water salinity was 6.04 dS/m, the less water resulted in more salt accumulation in topsoil and less in deep layers. When water salinity was 2.89 dS/m, however, the less water resulted in less salt accumulation in topsoil and salinity remained basically stable in deep layers. The salt accumulation in the ridge surface was much smaller than that in the furrow bottom under this technology, which was quite different from traditional furrow irrigation. The soil salinities for MMF7, MMF8 and MMF9 in the ridge surface were 0.191, 0.355 and 0.427 dS/m, respectively, whereas those in the furrow bottom were 0.316, 0.521 and 0.631 dS/m, respectively. The result of correlation analysis indicated that compared with irrigation amount, the irrigation water salinity was still the main factor influencing soil salinity in furrow irrigation with plastic mulch on ridge.

Heavy metals in soils and plants in mango orchards in Petrolina, Pernambuco, Brazil

The monitoring of heavy metal concentrations in areas under intensive agriculture is essential for the agricultural sustainability and food safety. This paper evaluates the total contents of heavy metals in soils and mango trees in orchards of different ages (6, 7, 8, 9, 10, 11, 14, 16, 17, 19, and 26 years) in Petrolina, Pernambuco, Brazil. Soil samples were taken from the layers 0-20 cm and 20-40 cm, and mango leaves were collected in the growth stage. Areas of native vegetation (Caatinga) adjacent to the cultivated areas were used for comparison. The total concentrations of heavy metals (Cu, Cr, Fe, Zn, Mn, Ni, and Pb) were determined in soils and leaves. In general, mango cultivation led to Cu and Zn accumulation in the soil surface and to a reduction in the contents of Ni, Pb, Mn, and Fe in surface and subsurface. Since contamination by Cu, Zn, and Cr was detected, these areas must be monitored to prevent negative environmental impacts. For instance, the presence of Cr in mango tree leaves indicates the need to investigate the source of the element in these orchards. The management strategies of the different companies led to deficiency or excess of some metals in the evaluated areas. However, the Fe and Mn levels were adequate for the mineral nutrition of mango in all areas.

Sodium chloride stress induces nitric oxide accumulation in root tips and oil body surface accompanying slower oleosin degradation in sunflower seedlings

Present work highlights the involvement of endogenous nitric oxide (NO) in sodium chloride (NaCl)-induced biochemical regulation of seedling growth in sunflower (Helianthus annuus L., cv. Morden). The growth response is dependent on NaCl concentration to which seedlings are exposed, they being tolerant to 40 mM NaCl and showing a reduction in extension growth at 120 mM NaCl. NaCl sensitivity of sunflower seedlings accompanies a fourfold increase in Na(+) /K(+) ratio in roots (as compared to that in cotyledons) and rapid transport of Na(+) to the cotyledons, thereby enhancing Na(+) /K(+) ratio in cotyledons as well. A transient increase in endogenous NO content, primarily contributed by putative NOS activity in roots of 4-day-old seedlings subjected to NaCl stress and the relative reduction in Na(+) /K(+) ratio after 4 days, indicates that NO regulates Na(+) accumulation, probably by affecting the associated transporter proteins. Root tips exhibit an early and transient enhanced expression of 4,5-diaminofluorescein diacetate (DAF-2DA) positive NO signal in the presence of 120 mM NaCl. Oil bodies from 2-day-old seedling cotyledons exhibit enhanced localization of NO signal in response to 120 mM NaCl treatment, coinciding with a greater retention of the principal oil body membrane proteins, i.e. oleosins. Abolition of DAF positive fluorescence by the application of specific NO scavenger [2-phenyl-4,4,5,5-tetramethyllimidazoline-1-oxyl-3-oxide (PTIO)] authenticates the presence of endogenous NO. These novel findings provide evidence for a possible protective role of NO during proteolytic degradation of oleosins prior to/accompanying lipolysis.

Distribution of organic carbon in physical fractions of soils as affected by agricultural management

Soil organic carbon (SOC) is distributed heterogeneously among different-sized primary particles and aggregates. Further, the SOC associated with different physical fractions respond differently to managements. Therefore, this study was conducted with the objective to quantify the SOC associated with all the three structural levels of SOC (particulate organic matter, soil separates and aggregate-size fractions) as influenced by long-term change in management. The study also aims at reevaluating the concept that the SOC sink capacity of individual size-fractions is limited. Long-term tillage and crop rotation effects on distribution of SOC among fractions were compared with soil from adjacent undisturbed area under native vegetation for the mixed, mesic, Typic Fragiudalf of Wooster, OH. Forty five years of no-till (NT) management resulted in more SOC accumulation in soil surface (0–7.5 cm) than in chisel tillage and plow tillage (PT) treatments. However, PT at this site resulted in a redistribution of SOC from surface to deeper soil layers. The soils under continuous corn accumulated significantly more SOC than those under corn–soybean rotation at 7.5–45 cm depth. Although soil texture was dominated by the silt-sized particles, most of the SOC pool was associated with the clay fraction. Compared to PT, the NT treatment resulted in (i) significantly higher proportion of large macroaggregates (>2,000 μm) and (ii) 1.5–2.8 times higher SOC concentrations in all aggregate-size classes. A comparative evaluation using radar graphs indicated that among the physical fractions, the SOC associated with sand and silt fractions quickly changed with a land use conversion from native vegetation to agricultural crops. A key finding of this study is the assessment of SOC sink capacity of individual fractions, which revealed that the clay fraction of agricultural soils continues to accumulate more SOC, albeit at a slower rate, with progressive increase in total SOC concentration. However, the clay fraction of soil under native woodlot showed an indication for SOC saturation. The data presented in this study from all the three structural levels of SOC would be helpful for refining the conceptual pool definitions of the current soil organic matter prediction models.