Low Retention Capacity Research Articles

Exploring soil nitrogen and sulfur dynamics: implications for greenhouse gas emissions on the Qinghai-Tibet Plateau.

The Qinghai-Tibet Plateau is particularly vulnerable to the effects of climate change and disturbances caused by human activity. To better understand the interactions between soil nitrogen and sulfur cycles and human activities on the plateau, the distribution characteristics of soil nitrogen and sulfur density and their influencing factors for three soil layers in Machin County at depths of 0-20cm, 0-100cm, and 0-180cm are discussed in this paper. The results indicated that at depths of 0-180cm, soil nitrogen density in Machin County varied between 1.36 and 16.85kg/m2, while sulfur density ranged from 0.37 to 4.61kg/m2. The effects of three factors-geological background, land use status, and soil type-on soil nitrogen and sulfur density were all highly significant (p < 0.01). Specifically, natural factors such as soil type and geological background, along with anthropogenic factors including land use practices and grazing intensity, were identified as decisive in causing spatial variations in soil nitrogen and sulfur density. Machin County on the Tibetan Plateau exhibits natural nitrogen and sulfur sinks; However, it is crucial to monitor the emissions of N2O and SO2 into the atmosphere from areas with high external nitrogen and sulfur inputs and low fertility retention capacities, such as bare land. On this basis, changes in the spatial and temporal scales of the nitrogen and sulfur cycles in soils and their source-sink relationships remain the focus of future research.

Oued Lakhdar watershed (Morocco), monitoring land use/cover changes: remote sensing and GIS approach

ABSTRACT Landsat is a series of Earth-observation satellites jointly managed by NASA and the United States Geological Survey (USGS) that capture multispectral images of the Earth’s surface dating back to the 1970s, providing a valuable tool for tracking changes in land cover over time. In this study, Landsat satellite data were combined with remote sensing and Geographic Information System (GIS) technologies to monitor land cover changes in the Oued Lakhdar watershed, which covers an area of 1,638 km2. Landsat satellite data for the years 1987, 1994, 2004, 2014, and 2021 were used, and the maximum likelihood method was applied in ArcGIS software version 10.4.1 to classify land components. The classification was validated using total accuracy, the kappa index, Google Earth, and terrain knowledge. The results show remarkable changes in land cover, with an increase in bare soil and irrigated crops between 1987 and 2021, especially in the last six years, totaling 0.672 km2/yr and 15.028 km2/yr of the study area, respectively, and a decrease in water bodies and dense forests, totaling −0.941 km2/yr and −30.046 km2/yr, respectively. Water retention coefficient analysis indicates that the watershed is anthropized and has a low retention capacity. This study provides valuable information for land use planning and management in the Oued Lakhdar watershed (Morocco).

Pea grain shells as a raw material for sorptive treatment of polluted waters

In the complex processing of pea grain, as well as in the production of groats and flour, a number of wastes are generated, a significant part of which is utilized. The conversion of waste processing to secondary raw materials not only allows for the resolution of environmental problems but also expands the opportunities for raw materials in economic sectors. Pea grain shells, which contain biopolymers, vitamins and minerals, can be considered as one of the sources of raw materials for obtaining sorption materials. The object of the research in this work was the shells isolated from the grain of the Amior and Temp pea varieties of Russian selection. The aim of the study was to investigate the structure, physical properties, and component composition of the pea grain shells, as well as to evaluate the prospects of their use as raw materials for the production of sorbents for the treatment of polluted surface water and wastewater. To determine the quality indicators of pea grain shells, the generally accepted methods were used. The share of shells in pea grain was found to be 7.1-10.6%. The main components in the composition of pea grain shells are polysaccharides, with a predominance of fiber, largely determining the structure and properties of this raw material. Pea grain shells are characterized by low density, good hygroscopicity and moisture retention capacity. The proteins and pectins present in the composition of the pea shells have sorption properties. It is possible to increase the degree of purification of surface and waste water from harmful impurities by using extracts from pea shells containing biopolymers that form insoluble complexes with pollutants.

Design, optimization, and evaluation for a long-time-released transdermal microneedle delivery system containing estradiol.

Transdermal drug delivery systems (TDDS) have drawbacks such as poor absorption, low blood concentration, and delayed effects. Dissolving microneedle has sharp tips and short length, which overcome patients' pain and improve transdermal efficiency but has low mechanical strength and drug loading capacity. This study thereby proposes a microemulsion-encapsulated and long-time-released transdermal microneedle (MN) delivery system with estradiol (Es) as the model drug. The microemulsion (ME) was optimized by utilizing the pseudo-ternary phase diagram and D-optimal mixture design. The estradiol microemulsion-encapsulated microneedle (Es-ME-MN) was optimized by Box-Behnken design and prepared by freeze-thaw method. The Es-ME-MN obtained was characterized and evaluated through a large variety of studies. Es-ME-MN had sufficient mechanical strength to pierce skin and was safe enough, the length of which was 600 μm, and the Es content was 177.12 ± 0.72 μg/patch without drug-excipient chemical interaction. In vitro permeation study showed that Es-ME-MN has a higher transdermal efficiency and lower retention capacity than commercial estradiol patch and conventional MN. Es plasma concentration began to increase at 3 h and remained at 12.98-23.52 ng/mL until 72 h by pharmacokinetic experiments in the Es-ME-MN group. Es-ME-MN rapidly achieves effective blood concentrations through needle puncture and microemulsion delivery and maintains blood concentrations through the baseplate long-time release. Microemulsion-encapsulated, organic solvent-free, and long-time-released transdermal microneedle will make progress and provide a new idea for transdermal delivery of lipophilic drugs.

Land use and cover change and water quality of tropical wetlands under anthropogenic pressure: A case study of marshlands in the Kaziba chiefdom in South-Kivu province, Eastern DR Congo

Wetlands provide goods and ecosystem services to communities and play an important socio-economical role during dry seasons and/or droughts. However their role in nutrient stocking is poorly documented. These ecosystems are currently under anthropogenic pressure for the last decades. This study (i) assessed the land use and cover changes in and around wetlands located in the eastern Democratic Republic of Congo (DRC), (ii) characterized their water quality, and (iii) assessed the effect of those changes on the nutrients retention capacity (NRC). Based on a case study in three wetlands namely Luzinzi, Nkombo, and Kalamba, all located in the Walungu territory. Supervised classification based on Support Vector Machine (SVM) of very high spatial resolution satellite (of 1985, 2015, and 2021) was used to assess land use and land cover change. Water samples were taken (in 2018 and 2019) for characterization at the inlet and outlet of each marshland, and the nutrients retention capacity (NRC) was assessed. Results show that these wetlands have undergone significant changes in terms of land use and occupation, with previously woodland and herbaceous areas becoming bare soil, cultivated lands, and built-up areas, respectively. The ability of the marshes to purify the water and its quality is not affected by all these changes. The study shows that the water quality analysis of the streams draining the marshes was rather good, and a very good value was obtained for salt (Sodium Absorption Ratio: SAR). However, these marshes have a very low (if any) nutrient retention capacity. Future interventions should alleviate human pressure on these ecosystems while focusing efforts on ecological function maintenance or restoration.

Improving ultrafiltration of algae-laden water with chitosan quaternary ammonium salt enhanced by sodium percarbonate

Ultrafiltration (UF) is extensively used for algae removal because of its ability to retain algal cells with high efficiency, but it still faces the problem of membrane fouling and low retention capacity of dissolved organics. Hence, a strategy of coagulation with chitosan quaternary ammonium salt (HTCC) enhanced by sodium percarbonate (SPC) pre-oxidation was proposed to improve the UF performance. The fouling resistances were calculated by a resistance-in-series model based on Darcy's formula, and the membrane fouling mechanism was evaluated using a pore plugging-cake filtration model. The effect of SPC-HTCC treatment on the properties of algal foulants was explored, and the result showed that the water quality was improved with the maximum removal rates of 78.8 %, 52.4 % and 79.5 % for algal cells, dissolved organic carbon and turbidity, respectively. The SPC could achieve a mild oxidation effect that degraded the electronegative organics attached to algal cells without destroying the cell integrity, making the algal pollutants easier to agglomerate through subsequent HTCC coagulation by forming larger flocs. In terms of membrane filtration, the terminal normalized flux was increased from 0.25 to 0.71, with the reversible and irreversible resistances reduced by 90.8 % and 40.2 %, individually. The synergistic treatment reduced the accumulation of algal cells and algae-derived organics on the membrane surface as inferred from the interface fouling characteristics. The interfacial free energy analysis showed that the synergistic treatment reduced the adhesion of contaminants to the membrane surface, as well as the attraction among pollutants. Overall, the proposed process has high application prospects for algae-laden water purification.

Improving the Continuous Multiple Tube Reactor: an Innovative Bioreactor Configuration with Great Potential for Dark Fermentation Processes.

The continuous multiple tube reactor (CMTR) has been developed as a promising technology to maximize biohydrogen production (BHP) by dark fermentation (DF) by preventing excess biomass accumulation, leading to suboptimum values of specific organic loading rates (SOLR). However, previous experiences failed to achieve stable and continuous BHP in this reactor, as the low biomass retention capacity in the tube region limited controlling the SOLR. This study goes beyond the evaluation of the CMTR for DF by inserting grooves in the inner wall of the tubes to ensure better cell attachment. The CMTR was monitored in 4 assays at 25ºC using sucrose-based synthetic effluent. The hydraulic retention time (HRT) was fixed at 2h, while the COD varied between 2-8g L-1 to obtain organic loading rates in the 24 - 96g COD L-1 d-1. Long-term (90 d) BHP was successfully attained in all conditions due to the improved biomass retention capacity. Optimal values for the SOLR (4.9g COD g-1 VSS d-1) were observed when applying up to 48g COD L-1 d-1, in which BHP was maximized. These patterns indicate a favorable balance between biomass retention and washout was naturally achieved. The CMTR looks promising for continuous BHP and is exempt from additional biomass discharge strategies.

Pioneer Tree Bellucia imperialis (Melastomataceae) from Central Amazon with Seedlings Highly Dependent on Arbuscular Mycorrhizal Fungi.

Bellucia imperialis is one of the most abundant pioneer tree species in anthropized areas of the Central Amazon, and has ecological importance for the environmental resilience of phosphorus (P)-depleted areas. Thus, we investigated whether B. imperialis depends on symbiosis with arbuscular mycorrhizal fungi (AMF) to grow and establish under the edaphic stresses of low nutrient content and low surface moisture retention capacity of the substrate. We tried three AMF inoculation treatments: (1) CON-no mycorrhizae; (2) MIX-with AMF from pure collection cultures, and (3) NAT-with native AMF, combined with five doses of P via a nutrient solution. All CON treatment seedlings died without AMF, showing the high mycorrhizal dependence of B. imperialis. Increasing P doses significantly decreased the leaf area and shoot and root biomass growth for both the NAT and MIX treatments. Increasing P doses did not affect spore number or mycorrhizal colonization, but decreased the diversity of AMF communities. Some species of the AMF community showed plasticity, enabling them to withstand shortages of and excess P. B. imperialis was shown to be sensitive to excess P, promiscuous, dependent on AMF, and tolerant of scarce nutritional resources, highlighting the need to inoculate seedlings to reforest impacted areas.

Rice Soil Fertility Classification in the Mekong Delta, Vietnam

The rice crop intensification led to soil degradation and yield decline in the Mekong Delta, Vietnam. Therefore, it is necessary to classify soil fertility and identify the constraints for proper soil use. The soil legend classified by World Reference Based was converted to the Fertility Capability Classification system. The soil constraints and recommendations for appropriate services are suggested. The findings indicate seven primary soil categories, ten diagnostic layers, three diagnostic features, and three diagnostic materials in the rice soils of the Mekong Delta. Eleven soil constraints were found, most of which were associated with acid sulfate and saline soils. These constraints included low acidity, strong acidity, low available P, high P fixation, high potential Fe toxicity, slightly actual acid sulfate and shallow potential acid sulfate, deep potential acid sulfate, slight salinity, and strong salinity, low mineral supply capacity, limited organic carbon content, and low nutrient retention capacity. Reclamation of acid sulfate and saline soils by leaching soil toxicity and boosting soil nutritional status with organic matter and P, K treatment were recommended for degraded, acid sulfate, and saline soils.

Ecogeomorphic response of a coastal dune in southern Portugal regulated by extrinsic factors

Coastal dunes are complex landforms whose morphology results from various interactions between biotic and abiotic factors. Here, we explore the longshore variability of the morphological features, plant community distribution and accumulation patterns of a dune segment (1.4 km-long) located at the downdrift end of a sandy peninsula in the Ria Formosa, Portugal. To understand the main drivers of the observed variability and the implications for dune morphological response, this information was combined with recent multidecadal shoreline evolution data. The integrated results document significant differences in dune morphology, sedimentation patterns and plant zonation, with two distinct dune configurations or states identified in close proximity. One (western sector) shows a narrower dune system, vegetation cover characterised by pioneer species with low densities, and squeezed plant zonation. Conversely, the other (eastern sector) presents a wider dune system with a new foredune, a more developed plant zonation and relatively high vegetation density. Both states could be partially explained by the recent shoreline trends and inlet shifts, with stable to retreating trends in the western sector and shoreline progradation in the eastern one. Plant zonation and accumulation patterns suggest that the dune along the retreating sector is in a cycle of inland migration, encouraged by the reduced accommodation space and the low retention capacity of the vegetation across the dune stoss. Alternatively, observations along the prograding sector suggest that the greater accommodation space and the stabilising feedback between vegetation and topography promoted the seaward progradation of the system and the development of an incipient foredune. Outcomes support the importance of biogeomorphic feedbacks for the dune configuration, but they also evidence that the role of vegetation within the feedback is primarily regulated by physical factors that ultimately promote or inhibit vegetation effects on dune topography.

Assessment of soil fertility status in cotton-based cropping systems in Cote d’Ivoire

Cotton is the main cash crop in northern Côte d’Ivoire, where intensive cultivation along with low external inputs has led to a decline in crop yields due to soil degradation. The present study aims to assess the evolution of soil fertility during the 2013 and 2021 periods in the cotton basin area of Côte d’Ivoire. More specifically, the study (i) identified the limiting physico-chemical parameters of soil fertility, and (ii) analysed the state of evolution of soil fertility in 2013 and 2021 in the cotton basin of Côte d’Ivoire. For this purpose, a total of 64 soil samples were taken in 2013 and in 2021 on the same cotton plots on the 0-20 cm horizon. Chemical analyses of the soil samples in the laboratory were carried out on the following parameters: particle size distribution, pH water, total nitrogen (NT), Potassium (K+), Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+) and Cation exchange capacity (CEC). The results of the soil analyses showed that the sandy-clay textured topsoils dominate the whole study area in both years. This leads to a low retention capacity of exchangeable bases. Determination of the soil pH showed that the pH varies from slightly acidic to neutral (6.5&amp;lt;pH&amp;lt;7). The most limiting chemical properties are Cation exchange capacity (CEC) and the sum of the exchangeable bases (SEB) in the department of Korogho, Boundiali, and Ferkessedougou and the most limiting chemical properties in the department of Mankono are CEC. However, during the period from 2013 to 2021 the content of exchangeable cations (Ca2+, Mg2+ and K+) and the base saturation (BS) increased significantly in all the departments, more precisely in the department of Mankono. Although we observed a slight increase in the chemical properties of the soils in 2021 compared to 2013, the values were still below the minimum required threshold. This result implies that the soils have poor physico-chemical properties and consequently a low level of fertility, which compromises the sustainability of the cotton production system. The application of organic and mineral amendments is therefore essential to increase the nutrient content of these soils.

Monitoring the Quality of Soils around Rivers Wouri and Meme of Cameroon Using Plasticity and XRF

Mangroves play important roles in the environment such as sequestration, spawning of fishes and source of medicinal plants. Two rivers which feed the mangroves of Cameroon are Rivers Wouri and Meme. While River Wouri that feeds the Douala-Edea mangrove receives smaller water bodies that pass through an industrial environment, River Meme that feeds the Rio del Rey mangrove receives small water bodies that pass through an environment harbouring a lot of agricultural activities. The rural and urban communities use water from the rivers to grow vegetables (plant production). The quality of water that feeds the mangroves is of paramount importance. This in turn depends on the mineralogical content of the soils around the rivers and adjourning water sources. This is because soils act as sinks for pollutants. Different clay minerals have different capacities to retain and release chemical entities. Therefore, they contribute differently in the protection of catchment areas. This work was therefore aimed at investigating the role played by soils in controlling the movement of these chemical elements into the rivers. Clays extracted from soils around these water sources were analyzed for mineralogical composition. All analyses were carried out using standard plasticity and XRF methods. Clay content (2 to 7%) in Wouri was lower than in Meme (4 to 34%). The majority of the clay was dominated by SiO2, Al2O3, Fe2O3, and TiO2 and was a mixture of non-expandable (2:1 and 1:1) and sesquioxide clays. The soils have low pollutant retention capacity and are therefore vulnerable to anthropogenic activities. Hence, stringent measures should be taken to monitor soil/water quality with respect to waste disposal and use of agrochemicals. The use of compost in place of fertilizers by farmers should also be encouraged.

Cadmium and lead adsorption and desorption by coffee waste-derived biochars

Biochar derived from coffee waste has been reported as a promising material for heavy metal sorption. However, if the intended use is environmental remediation, knowing the extent to which desorption may occur is critical. Thus, the objective of this work was to evaluate the efficiency of spent coffee ground (SCG) and coffee parchment (CP) biochars pyrolyzed at 700 °C under laboratory conditions, in the sorption of Cd and Pb from aqueous solutions, in a pH range from 2 to 10, and their retention after an induced desorption process with a 2.9 pH acetic acid solution. Both biochars were alkaline, and the initial pH of the solution had a large effect on the sorption capacity of SCG but a small effect on the sorption capacity of CP. The Pb sorption capacity was higher for CP (18.6 mg·g–1) than for SCG (11.4 mg·g–1), while both biochars had low Cd retention capacities (1.18 mg·g–1). Coffee parchment also showed the highest Pb retention (30% to 87%), while for Cd there was no difference between CP and SCG biochars. Our results showed that metal precipitation was the main mechanism for metal immobilization and CP biochar proved to be more reliable than SCG, mainly for Pb, due to its higher sorption capacity and lower metal release by desorption than SCG. These characteristics are particularly important for the use of biochar in environmental remediation. Besides that, the biochar production represents an eco-friendly destination for these feedstocks, contributing to the circular economy.

Impact of climate change on land use dynamics along River Ona, Nigeria

Climate change has direct influence on environment and human existence. Climate change has been a monster posing threat to the hydrological cycle, hence the flow discharge of rivers. Therefore, it is necessary to study its effects on the flow of rivers thereby producing measures to alleviating its effects. In this study, the effects of land cover and weather conditions between 1967 and 2017 on the flow discharge of River Ona were investigated by making use of the climatic data (rainfall and temperature). The statistical variations in temperature and rainfall data were assessed using Statistical Program for Social Science (SPSS) in order to depict the linear variation, regression and correlation of the prevailing climate of the area The results showed that year 1998 and 1999 have the lowest and highest rainfall values respectively. The land-use maps show there is gradual increment in area of lands that are built-up but gradual reduction in the vegetal area. The runoff of River Ona would increase because of wetter climate caused by high rainfall in 1999. In addition, over the years, runoff severity tends to increase because of land development, giving rise to the replacement of vegetal areas by built up areas, which have low retention capacity in the area. The findings from this study can be used to predict the discharge of river given other weather and environmental factors.

Cadmium retention and microbial response in volcanic soils along gradients of soil age and climate on the Galápagos Islands.

The behavior of trace metals may vary strongly in the course of volcanic soil development. Cadmium retention in soils is specifically important for some Galápagos islands where agriculture is leading to anthropogenic Cd contamination. To assess the influence of soil development factors on soil Cd retention and toxicity, we performed Cd sorption-desorption experiments with volcanic topsoils from the Galápagos Islands sampled along gradients of (a) substrate age (chronosequence, 1.5-1,070 ka) and (b) climate (elevation sequence, 47-866 m asl) ranging from arid lowland areas to humid highland areas. Additionally, the effects of Cd toxicity on the soil microbial community composition were evaluated for two soils of the chronosequence. In young volcanic soils, the sorption capacity was very high but decreased rapidly with soil age and increasing elevation. These trends were coupled with decreases in soil weathering indicators (e.g., electrical conductivity, pH, and effective cation exchange capacity) as well as changes in soil mineralogy. Cadmium addition did not influence total phospholipid fatty acids and basal respiration in most soils. However, with increasing Cd concentration, a pronounced reduction in the Gram-negative/Gram-positive bacteria ratio (from 0.32 to 0.12) occurred in an old, highly weathered soil with low Cd retention capacity. Our results show that up to 60% of added Cd was only weakly sorbed in old volcanic soils. As a consequence, the old volcanic soils of Galápagos bear the potential risk that the mobile Cd fraction is taken up by soil microorganisms, transferring this element into the food chain.

COMPARISON OF MICROLEAKAGE IN CLASS V CAVITIES RESTORED BY GLASS IONOMER CEMENT AND COMPOSITE WITH OR WITHOUT PROTECTIVE COATING MATERIAL

Background: In order to treat cervical lesion of teeth, class V cavity is prepared and filled with restored materials. However, class V restoration is a common challenge to clinicians: low retention capacity, marginal defect and secondary caries due to microleakages. The aim of this study was to compare microleakage of class V cavities restored by glass ionomer cement and composite restoration with or without protective coating material. Materials and Methods: 60 extracted premolars were randomly divided into 6 groups (n=10/ group). Each group were prepared and restored with one of three materials: conventional glass ionomer (CGIC), resin-modified glass ionomer (RMGIC) and composite, with or without G-Coat Plus. All samples were thermocycled, immersed in 0.5% Fuschin solution and evaluated microleakage by dye penetration. Results: Gingival margin showed higher microleakage than occlusal margin in Composite group and CGIC groups with G-Coat Plus (p &lt; 0.05). RMGIC showed lower microleakage than CGIC and Composite when assessed on gingival margin (p &lt; 0.05). G-Coat Plus reduced the microleakage in the RMGIC and Composite groups when compared with the uncoated group (p &lt; 0.05). Conclusions: Microleakage depends on evaluated site and restored materials. Protective coating material reduces microleakage, especially on RMGIC and Composite restorations. Key words: microleakage, class V cavity, glass ionomer cement, composite, provetive coating

Effects on Interfacial Resistance Using LICGCTM in the Cathode

Lithium ion batteries are widely used in electric devices and electric vehicles due to their excellent performance at high power and the high energy density they provide compared to other conventional batteries. The application for electric vehicles is expanding worldwide as our society moves towards a lower carbon footprint but the lithium ion battery technology still needs further improvements in terms of physical properties, output, durability and safety. Current lithium ion batteries also degrade with charge–discharge cycles and storage time. In the cathode, low retention capacity, accompanied by the growth of resistive thin films and crystal structure deterioration on the surface of the active materials, remain unsolved problems. Modifications to the cathode surfaces have been researched and proven as effective measures to improve durability. Surface coatings on lithium‐ion battery cathodes improve their durability. Solid oxide materials like MgO, ZrO2 and SiO2 are applied or processed on to the cathode active materials by sol-gel, PVD or mechanochemical treatments and the solid oxide layer plays a role as an artificial solid electrolyte interface. The solid oxide coating layer prevents contact between the electrolyte and the active materials thus inhibiting the redox process and leading to an improvement in the cycle performance of the battery.We confirmed the LCO cathode containing a small % of Ohara lithium ion glass ceramic (LICGCTM ) PW-01 powder showed less deterioration and transition metal reduction at high temperature (60℃). The LICGCTM PW-01 powder was produced using a glass melting and ceraming method. A Li 2O-Al 2O 3-TiO 2-P 2O 5 glass was prepared and converted into glass-ceramics through heat-treatment. The lithium ion conductivity of the glass-ceramic with Li 1 + x Al x Ti 2 − x (PO 4) 3 phase is extremely high 1 × 10 −3 Scm −1 at room temperature. We found that adding LICGCTM PW-01 powder in the cathode had other significant effects, including increasing the battery capacity at high rate and at low temperature (-20℃). We also verified via by EIS measurement that the LICGCTM PW-01 powder additive significantly reduced the charge transfer resistance. The use of the LICGCTM PW-01 powder as a cathode slurry additive can serve an important role in improving the performance of lithium ion batteries.

Aggravation of reactive nitrogen flow driven by human production and consumption in Guangzhou City China

Human activities reshape the global nitrogen (N) cycle and affect environment and human health through reactive nitrogen (Nr) loss during production and consumption. In urbanized regions, the N cycle is greatly mediated by complex interactions between human and natural factors. However, the variations in sources, magnitude, spatiotemporal patterns and drivers of Nr flows remain unclear. Here we show by model simulations, anthropogenic perturbations not only intensify Nr input to sustain increasing demands for production and consumption in Guangzhou city, China, but also greatly change the Nr distribution pattern in the urban system, showing a substantial Nr enrichment in the atmosphere and a relatively low retention capacity of Nr in the terrestrial system. Our results highlight the strong anthropogenic effect of urban systems on the N cycle to suggest sustainable human activity changes to harmonize the relationship between Nr behaviors and human drivers.

Total concentration, contamination status and distribution of elements in a Nigerian State dumpsites soil

Abstract Recent happenings (like fire outbreak and soil contamination) on Nigerian dumpsites had reiterated the need to frequently monitor and assess these dumpsites in order to avert environmental disaster. This study was conducted to determine the concentration and distribution of elements in four selected dumpsites in Ondo State, Nigeria. Soils sampled from the dumpsite were tested for their particle size distribution, cation exchange capacity and elemental concentration. The statistical relationship between the elements present was also carried out by analyzing its concentrations. The results showed that sand and clay were the main particles present in the studied dumpsite soils. The low cation exchange capacity values of the soil from the studied dumpsite showed its low retention capacity and fertility. The elements (calcium, magnesium, potassium) needed as macronutrients for plant growth on the dumpsite soil were not present in a large concentration which may be due to the low nutrient retention capacity of the soil. The heavy metals present in the dumpsite though above recommended permissible limit (with the exception of chromium) showed (through the contamination indices) no immediate risk on man and the environment. Statistical analysis showed that there was a statistically significant difference in the concentration of the elements present on the studied dumpsite soils. There was, however, no statistically significant difference in the studied dumpsites. Whatever future plans the State government may have for these dumpsites, this study had pointed out some areas of the soil that may need to be improved and/or monitored for proper remediation.

High-rate anaerobic decolorization of methyl orange from synthetic azo dye wastewater in a methane-based hollow fiber membrane bioreactor

Anaerobic biological techniques are widely used in the reductive decolorization of textile wastewater. However, the decolorization efficiency of textile wastewater by conventional anaerobic biological techniques is generally limited due to the low biomass retention capacity and short hydraulic retention time (HRT). In this study, a methane-based hollow fiber membrane bioreactor (HfMBR) was initially inoculated with an enriched anaerobic methane oxidation (AOM) culture to rapidly form an anaerobic biofilm. Then, synthetic azo dye wastewater containing methyl orange (MO) was fed into the HfMBR. MO decolorization efficiency of ∼ 100 % (HRT = 2 to 1.5 days) and maximum decolorization rate of 883 mg/L/day (HRT = 0.5 day) were obtained by the stepwise increase of the MO loading rate into the methane-based HfMBR. Scanning electron microscopy (SEM) and fluorescence in situ hybridization (FISH) analysis visually revealed that archaea clusters formed synergistic consortia with adjacent bacteria. Quantitative PCR (qPCR), phylogenetic and high-throughput sequencing analysis results further confirmed the biological consortia formation of methane-related archaea and partner bacteria, which played a synergistic role in MO decolorization. The high removal efficiency and stable microbial structure in HfMBR suggest it is a potentially effective technique for high-toxic azo dyes removal from textile wastewater.