High Levels Of Electrical Conductivity Research Articles

Variations in macrofaunal communities along sand physico-chemical gradient across the intertidal zones on island beaches

Island beaches, once mistakenly considered as 'ecological deserts', are actually unique ecosystems that support abundant macrofaunal communities. However, limited studies have examined the variations and determinants of macrofaunal communities across the intertidal zones on island beaches, which is crucial for shedding light on the underlying ecological processes and enhancing biodiversity conservation efforts. Here, we explored the variations in macrofaunal communities along sand physico-chemical gradient across four intertidal zones on nine representative beaches, within the largest land-bridge archipelago in eastern China. Our findings revealed that species richness, density, and Shannon-Wiener diversity of macrofaunal communities were notably higher in the lower intertidal zones, exhibiting a positive correlation with elevated levels of sand moisture (M), electrical conductivity (EC), available potassium (AK), and grain size (GS). Conversely, macrofaunal Simpson diversity displayed an inverse pattern, with heightened values observed in the vegetation zone. The Saprophagous, Predaceous, and Omnivorous groups of macrofaunal communities demonstrated an increase with higher levels of EC, AK, and M in the lower intertidal zones. Furthermore, Phytophagous group of macrofaunal communities tended to inhabit the vegetation zones characterized by elevated levels of sand total phosphorus (TP), total nitrogen (TN), and organic carbon (OC). Primarily, our findings indicate that sand nutrition, moisture, and salinity play pivotal roles in shaping the variations of macrofaunal communities on island beaches. These insights offer valuable perspectives into the holistic responses of macrofauna on island beaches to changes in sand physico-chemical properties, serving as a crucial theoretical foundation for the assessment, conservation, and restoration of island beaches.

Effects of Variable Electrical Conductivity Levels in Hydroponic Nutrient Solutions on Morphological and Physiochemical Characteristics of Cucumber Plants in Advanced Greenhouse Cultivation

Cucumber (Cucumus sativus L.) is a fruit of the Cucurbitaceae family that is refreshing, low in calories, and offers various health benefits due to its rich nutritional profile. However, high-tech hydroponic greenhouse production of cucumber is nutrient-intensive and requires efficient management of electrical conductivity (EC) in the growing medium. In this study, three different EC levels (1.3, 2.6, and 3.6 dS/m) were applied to the nutrient medium of hydroponically grown Lebanese and Continental varieties of cucumber. The experiment did not have a significant impact on the number of fruits (p=0.744, p=0.163) or leaves per plant (p=0.252, p=0.377) at varying EC levels. However, in the Continental variety, pH (0.001***) and osmolality (0.005**) were significantly different among the three varied EC levels. High EC levels in the nutrient medium resulted in reduced TSS, pH, and osmolality of the fruit juice. Although the plants grown in low EC conditions produced almost the same number of fruits and leaves per plant as those grown in optimal EC conditions (2.6 dS/m), the physio-chemical attributes of the cucumbers were of inferior quality.

Groundwater quality and hydrochemical characteristics in the upper Seybouse sub-basin, Northeast Algeria.

The present study aims to evaluate the groundwater quality in an area characterized by significant human anthropic activities within the upper Seybouse. In order to assess the quality, a total of 20 samples were analyzed to identify the chemical and bacteriological composition of the water, its variations, and their potential impacts on the environment and human health. The results revealed concentrations of the chemical and bacteriological elements exceeding the WHO standards, with high levels of electrical conductivity (EC) (peak = 4210 μS/cm), Ca2+ (peak = 340.68mg/L), Na+ (peak = 360mg/L), HCO3- (peak = 287mg/L), Cl- (peak = 542mg/L), SO42- (peak = 687mg/L), NO3- (pek = 65.91mg/L), fecal coliforms (FC) (peak = 160 UFC/mL), fecal Streptococcus (FS) (peak = 43 UFC/mL), and Clostridium perfringens (CP) (peak = 29 UFC/mL). Within the basin, two different facies have been identified: Cl-SO4-Na type and Cl-SO4-Ca type. The calculated Water Quality Index (WQI) indicates that none of the groundwater samples are suitable for drinking or human consumption. The detection of pathogenic microorganisms through diverse molecular methods has revealed the existence of eight distinct species, encompassing pathogenic strains that can affect human health. Moreover, the dissolution of geologic formations can influence the water's chemistry. In this region, groundwater pollution seems to be influenced by anthropogenic and agricultural factors such as fertilizer application, irrigation practices, and the release of domestic sewage.

Investigation of the hydrocarbon contamination of the Dibdibba aquifer in Al-Zubair area, southern Iraq

The importance of Al-Zubair area in Basra governorate is highlighted by the presence of agricultural activities. The Dibdibba aquifer is the main supplier of water which used for irrigation, livestock and some different industries are scattered around the region. This research aims to investigate the extent and impact of hydrocarbon contamination of the Dibdibba aquifer in Al-Zubair region, southern Iraq, due to its proximity to oil fields sites. 18 groundwater samples from different locations within the aquifer were collected in dry and wet season to determine their chemical and physical properties and total petroleum hydrocarbon (TPH) including petroleum-based compounds and their derivatives. The analytical results revealed that the Dibdibba groundwater in this area is polluted with TPH and have high levels of electrical conductivity (EC) and total dissolved salts (TDS) due to the high content of salts along with the high concentrations of calcium and magnesium ions. The overall outcomes of the main elements of water showed that it is unfit for human use due to the high levels of the above parameters. All the water tests carried out indicate the presence of contamination with petroleum hydrocarbons, surpassing the allowable limits set by the World Health Organization (2008) and Iraqi Quality Standard (2009). This observed particularly in areas adjacent oil spills, where the TPH concentrations exceeding 35 μg/l in the northwest of Al-Zubair area near the Rumaila oil field. Significantly, this investigation indicated a clear evidence of hydrocarbon contamination in the study area.

Investigation of thermoelectric properties of high concentration PEDOT: PSS inks doped with graphene and multi-walled carbon nanotubes

The use of wearable technologies in various aspects of life, particularly in health and entertainment, is experiencing a remarkable increase. This intensity of usage brings with it the energy needs of these devices. Polymer-based thermoelectric generator solutions are one of the most emphasized issues in energy harvesting applications and stand out as a solution method. In this study, we introduce a high-concentration poly(3,4-ethylenedioxy-thiophene): polystyrene sulfonate (PEDOT: PSS)-based conductive polymer ink, which has been doped with graphene and multi-walled carbon nanotubes (MWCNT) for thermoelectric applications. We also explore the film properties derived from this ink. The fabrication process involves cryogenic freezing, lyophilization, and re-dispersion of a mixture of water and dimethyl sulfoxide (DMSO) with a commercial PEDOT: PSS aqueous solution, followed by the addition of specific additives. These added compounds have led to a significant increase in electrical conductivity, resulting in materials with high electrical conductivity levels ranging from 100 to 200 S/cm. Remarkably, even after subjecting the material to 100 bending cycles, no significant change in electrical conductivity was observed. All the materials produced exhibited p-type semiconductor properties, and the high concentration of PEDOT: PSS, along with the addition of graphene and multi-walled carbon nanotubes, notably enhanced the Seebeck coefficient, reaching a maximum of 25 μV K⁻1.

Appraisement of groundwater quality status within Enugu, Nigeria, using physicochemical evaluation and water quality indices

Enugu state is notorious for potable water scarcity which forces residents to depend on polluted water sources. In this study, an appraisement of the quality status of groundwater from some areas within Enugu was conducted. Physicochemical characteristics of groundwater sampled from 15 boreholes that supply domestic water to Aninri, Awgu, Ezeagu, Udi and Oji River Areas of Enugu, Nigeria, were determined. A total of 45 water samples were obtained across both rainy and dry seasons. Standard methods were used to determine the physicochemical parameters and trace metals. The physicochemical results showed values within the WHO safe limits, except sulphate (1670 ± 21.5 mg L−1) in Mpu water samples, and high chloride levels in Ndeaboh and Mpu (18088 ± 29.4 and 1095 ± 23.9 mg L−1 for dry and rainy seasons, respectively). The pH values were predominantly slightly acidic, ranging from 5 to 8.2. Groundwater within Ukaete, Ndeaboh, Oduma and Amankpunato had very high levels of electrical conductivity (2897.80 ± 173.38, 31000 ± 45.9, 1672 ± 9.3 and 1222 ± 8.1) in the dry season, respectively; and 1665.06 ± 326.6, 5410 ± 2.4, 4860 ± 9.4, 1872 ± 19.3 in the rainy season, respectively. The higher chloride values observed, possibly due to a geogenic origin, could also be responsible for the higher values of the electrical conductivity. There were traces of copper and lead in the samples during the dry season; however, lead was not detected in most borehole water samples during the wet season. Fe was the only metal that recorded values above the WHO standard. Traces of copper in the samples may have resulted from corrosion in the copper pipelines, reservoirs or other metallic fittings used in the construction of the boreholes. The water quality index (WQI) of the borehole water examined was above 100 in all except Ogugu Awgu samples, indicating that borehole water was generally not potable and therefore unsuitable for domestic application or drinking. The observed results revealed that the groundwaters from the study area were contaminated with chloride and lead, causing the water parameters to be above standard limits. Lead at any concentration is deemed toxic according to USEPA. There is a need to treat borehole water supplies in the area before its application for domestic use.

Road salt intrusion dynamics in an ex-urban native wetland complex

Inland freshwater wetlands throughout the northern U.S. and Canada are experiencing an increase in salinity due to road salt runoff during winter months. Salinization affects soil texture, contaminant transport, microbial activity, and plant growth in wetlands. Therefore, there is a pressing need to understand the dynamics of road salt intrusion in urbanized freshwater ecosystems. We used distributed high-resolution sensors to evaluate the dynamics of road salt intrusion into a wetland complex, Gensburg Markham Prairie (GMP), located in the ex-urban area outside Chicago, Illinois (USA). The in situ sensors measure electrical conductivity (EC), surface and groundwater level, precipitation, water temperature, and air temperature at 30-minute intervals. Water samples were collected monthly from 13 shallow groundwater wells and eight surface water locations and analyzed for Cl-, Mg2+, Na+, Ca2+, and K+. Two-years of continuous data show periodic spikes in EC during winter months, generally by an order-of-magnitude, due to intrusion of road salt applied on nearby roads. However, this behavior was not evident from monthly water samples, indicating that traditional water quality sampling methods likely miss such abrupt salt intrusion dynamics caused by rapid snowmelt runoff events. Higher levels of EC and Cl- occurred at the periphery of GMP near roadways, as well as in a preferential flow path to the interior of the wetland. Spectral analysis of EC time-series in ditches suggests that there is no correlation between salinity dynamics at super-annual timescales. This indicates that the salinity dynamics at GMP are event-driven, and the introduced solutes are rapidly exported from the site. This research supports development of improved de-icing strategies by local agencies and informs site-specific management of wetland ecosystems under anthropogenic stressors.

Interaction of climate, topography and soil properties with cropland and cropping pattern using remote sensing data and machine learning methods

Precision agriculture which facilitates and enables crop management through site-specific recommendations, is essential to optimize agricultural inputs in space and time. In this study, we used Landsat and MODIS-NDVI product data with climatic, topographic data and laboratory-analyzed soil samples to map the spatial distribution of seven soil properties; soil texture (T), electrical conductivity (EC), potential hydrogen (pH), nitrogen (N), phosphorus (P), potassium (K), and organic matter (OM) in the Punjab, Pakistan from 2000 to 2020. We examined and compared three statistical prediction models: the support vector machine (SVM), the random forest regression (RFR), and the multiple linear regression (MLR). The predictions were validated against a separate set of soil samples while considering the modeling region and an extrapolation area. Model performance statistics showed that the RFR often provided the highest accuracy, with the machine learning algorithms performing slightly better than the MLR. It was discovered that one obstacle to accurately forecasting soil parameters at unsampled areas with MLR was its inability to handle non-linear connections between independent and dependent variables. The results indicate that the cultivated area decreased from 43.16 % in 2000 to 38.24% in 2020. The soil has a high level of EC due to salinity. In general, the soils contained < 1% OM with lower N. However, the K and P contents were considered medium and adequate. Free remote sensing data has made it possible to improve soil knowledge at local and regional scales in data like Punjab with little outlays of time and money.

Effects of NaCl and CaCl2 as Eustress Factors on Growth, Yield, and Mineral Composition of Hydroponically Grown Valerianella locusta

Corn salad (Valerianella locusta) is a popular winter salad, cultivated as an ingredient for ready-to-eat salads. The application of mild salinity stress (eustress) can increase the flavor and reduce the nitrate content of certain crops but, at the same time, a wrong choice of the eustress type and dose can negatively affect the overall productivity. In this research, the effects of different isosmotic salt solutions, corresponding to two different electrical conductivity (EC) levels, were investigated on the yield and mineral composition of hydroponically grown Valerianella locusta "Elixir". Five nutrient solutions (NS) were compared, including a basic NS used as the control, and four saline NS were obtained by adding to the basic NS either NaCl or CaCl2 at two rates each, corresponding to two isosmotic salt levels at a low and high EC level. Corn salad proved moderately susceptible to long-term salinity stress, suffering growth losses at both low and high EC levels of saline solution, except from the low NaCl treatment. Hence, it appears that mild salinity stress induced by NaCl could be employed as an eustress solution and corn salad could be cultivated with low-quality irrigation water (20 mM NaCl) in hydroponic systems.

Assessment of genotoxic effects of wastewater of Kitchener pool, Nile Delta Region, North Egypt, using Allium test

BackgroundIn the present study, Allium test bioassay was utilized to evaluate the effects of mixed wastewater of agricultural and sewage effluents at Kitchener pool, Gharbia governate, Middle Delta region, North Egypt. Germination indices, mitotic index and aberrations, α, β-esterase isozymes and inter-simple sequence repeat (ISSR) fingerprinting were tested by different concentrations of the wastewater (tap water as control, 25%, 50% and 100% wastewater).ResultsWater analysis recorded high levels of electrical conductivity, cations and anions compared to control, but were in the permitted limits according to FAO (Food and Agricultural Organization) except Mg2+ and K1+ were above the limits. P, N and heavy metals as Pb, Mn and Ni were also higher than the control. Germination indices showed reduction for all parameters studied (root and shoot lengths, root and shoot fresh and dry weights, and tolerance index). Mitotic index decreased, and the percentage of mitotic aberrations increased as the concentration of treatments increased and the time prolonged. Different types of aberrations were recorded in all treatments and its percentage is time and dose independent. Goat cells are the most common type recorded after different times in all treatments. The expression of α, β-esterase enzymes showed variation in different treatments compared to control and ISSR profiles showed considerable polymorphism. Concentration of 25% mixed water induced different profiles for expression of both α- and β-esterase from other treatments, and the cluster analysis based on polymorphism in ISSR fingerprinting revealed the distinction of plants treated with this concentration and the control plants from those treated with high concentrations.ConclusionIt was suggested that concentration of 25% mixed water may be suitable for growth and act as fertilizer. Mixed water from this pool may be genotoxic for Allium cepa plants at early growth if it is used for irrigation in its present form and usage of this wastewater for agricultural purposes may be harmful and must be partially treated and biologically tested before use.

Exploring the Simultaneous Effect of Total Ion Concentration and K:Ca:Mg Ratio of the Nutrient Solution on the Growth and Nutritional Value of Hydroponically Grown Cichorium spinosum L.

Nutrient-efficient plants and agricultural systems could tackle issues resulting from conventional agriculture. Spiny chicory (Cichorium spinosum L.), a very adaptive, wild edible vegetable, is gaining commercial interest as a functional food. Floating-raft hydroponics is a method commonly used for the commercial cultivation of leafy vegetables due to numerous advantages compared to soil cultivation. In this paper, the simultaneous effects of different potassium, calcium and magnesium ratios and different electrical conductivity (EC) levels on the growth and mineral composition of hydroponically grown C. spinosum were investigated. Four nutrient solutions (NS) were compared, two NS with low EC (L, 2.4 dS/m) and two with high EC (H, 3.6 dS/m) with K:Ca:Mg ratios of either 50:40:10 or 40:50:10. The results showed no interactions between the two factors. No significant effects were observed on the fresh and dry weight, leaf number and leaf area. High EC levels increased the K content and decreased the Mn and Zn content in the leaf tissues. The 40:50:10 ratio led to increased Ca content in plant tissues. The Nitrate-N was only affected by the EC level and was increased under H conditions, whereas the total-N was not affected.

Morphological Responses of Viola Accessions to Nutrient Solution Application and Electrical Conductivity

Growing of ornamental flowering plants represents an important sector of horticulture. Viola × wittrockiana (garden pansy) is used in garden beds and borders due to their colorful blooming, which occurs in early spring and late autumn. Nowadays, breeders focus on applying different nutrient solutions to improve the quality, flowering, and ornamental properties of plants, yet electrical conductivity (EC) level is an important fact to know. It is known that higher EC levels can inhibit plants’ growth. In the present study, pansy seedlings were subjected to different EC nutrient solutions 1 (control), 2, 3.5, 5, and 6.5 mS cm−1 EC to assess the positive or negative effects regarding the plant’s growth and development. The results indicated that an appropriate EC level of nutrient solution can have a positive effect on growth parameters, as well as on the flowering of plants. According to the hierarchical clustering, the used EC nutrient solutions significantly influenced the growth, number of shoots and leaves and the inflorescences number. From the present study results, it can be concluded that even though all EC levels increased growth parameters compared with control, the greatest results were obtained in plants under the effect of the 5 mS cm−1 of EC.

Nutrient Concentrations Induced Abiotic Stresses to Sweet Pepper Seedlings in Hydroponic Culture.

The primary goal of this experiment was to investigate the effects of nutrient electrical conductivity (EC) on the growth and physiological responses of sweet pepper (Capsicum annuum L.) in hydroponic culture in a greenhouse. The plant growth parameters, leaf photosynthesis, root activity, soluble protein, malondialdehyde (MDA), proline, activities of antioxidant enzymes (AE), and the contents of plant mineral elements (PME) were measured in six different EC treatments. The results showed that very high or low EC treatments clearly decreased the plant height, stem diameter, shoot dry weight, and leaf net photosynthetic rate, while increasing the content of MDA and the activities of ascorbate peroxidase and guaiacol peroxidase. The contents of proline and soluble protein increased gradually from the low to high EC treatments. The root activities decreased significantly, and the main PME clearly did not increase or even decreased at high EC levels. Very high EC treatments suppressed growth even more than those of very low EC. Treatments that were too low or high EC suppressed plant growth, owing to abiotic stress (either nutrient deficiency or salinity), since the plants had to regulate the activities of AE and increase the accumulation of osmolytes to adjust to the abiotic stresses.

Value of dehydrated food waste fertiliser products in increasing soil health and crop productivity

Dehydration of food waste is a technique in which food waste is dewatered to form a low moisture product. This research characterised the physicochemical properties of different dehydrated food waste products and examined their value in improving physical, biological, and chemical properties of soils. Dehydrated food waste products were slightly acidic (4.7–5.1) with high levels of electrical conductivity (EC) (4.83–7.64 mS cm−1). The products were composed of complex carbohydrates, polysaccharides, alcohols, phenols, carboxylic acid, lipids, and fats and contained high levels of total and available nutrients. Dehydrated food wastes slightly impacted the soil pH; however, they significantly increased soil EC, which may cause soil salinity when applied repeatedly. The food waste products also increased macro-nutrients (N, P, and K) for plants across different soil types. Carbon and nutrients in dehydrated food waste increased microbial activity, measured by basal respiration. Delayed germination and reduced plant growth of corn (Zea mays) and wheat (Triticum aestivum) plants were observed at high application rates of dehydrated food waste. This may have resulted from a combination of phytotoxins, anoxic conditions, salinity as well as the water-repellent nature of dehydrated food waste. However, release of nutrients increased nutrient uptake and plant biomass in corn and wheat plants at low levels of food waste application. The dehydrated food waste products may require composting prior to soil application or incorporation into soil for a long duration prior to planting. These processes will overcome the limitations of phytotoxins, anoxic conditions, salinity, and water repellence. Further work is required to optimise the levels of dehydrated food waste application to improve soil health and crop productivity.

Maintaining electrical conductivity of microcellular MWCNT/TPU composites after deformation

Along with stretching ability, maintaining good electrical conductivity has become one of the most desirable properties for the next-generation electronics. Although various fabrication methods have been suggested, the greatest obstacle is their feasibility for large-scale production with low cost. In this study, highly stretchable and conductive MWCNT/TPU composite foams were fabricated by an industrially viable technique, melt compounding followed by supercritical fluid treatment and physical foaming. It was demonstrated that the introduction of a microcellular structure can significantly suppress increase in the electrical resistance with stretching. The 3.1 vol% MWCNT/TPU composite exhibited electrical conductivity of 9.5 × 10−4 S/cm, which reduced to 1.7 × 10−5 S/cm with 100% stretching. The creation of 26% void fraction increased the conductivity to 1.9 × 10−3 S/cm and assisted in maintaining a constant level of the electrical conductivity with 100% stretching. This is attributed to the localized deformation around the cells. Since the deformation is localized around the cells, the filler interconnections away from the cells are less deformed, and hence can maintain a high level of electrical conductivity. It was further found that the effect of localized deformation enhances the elongating ability of the MWCNT/TPU composites. This study shows that the generation of a microcellular structure offers a very effective way of fabricating highly stretchable and conductive polymeric materials for future electronics.

Performance of Hydroponically Cultivated Geranium and Common Verbena under Salinity and High Electrical Conductivity Levels

Abiotic factors in nutrient solutions (NSs), such as salinity and high electrical conductivity (EC), may adversely alter plant growth and crop performance. However, there are medicinal/aromatic plants which can not only withstand these adverse conditions, but which can also increase their productivity or even enhance their quality in such conditions. As fresh water sources suitable for irrigation are becoming more and more limited, the use of low-quality water sources and hydroponic growing systems have been suggested as the main alternatives. Towards that direction, this study aims to evaluate the effect of high EC levels in NSs on geranium (Pelargonium graveolens L’Hér.) and common verbena (Verbena officinallis L.) plants cultivated in a soilless (perlite) hydroponics system. Plants were irrigated with a full nutrient solution of EC 2.1 dS m−1 and pH 5.8 until they reached a uniform size. Then, three treatments were applied, namely: (a) a control treatment with an EC of 2.1 dS m−1 in the NS, (b) a high-salinity NS created by adding 75 mM of NaCl (EC under 8.5 dS m−1) and (c) a concentrated NS with an EC of 8.5 dS m−1. In pelargonium, high salinity decreased the total phenolic and total flavonoid contents; antioxidant capacity; N, K, Mg and P content; as well as chlorophyll fluorescence, compared to the control treatment. On the other hand, increased salinity levels increased the Na and Ca content and stomatal resistance. In common verbena, salinity decreased total phenolic content and chlorophyll fluorescence but increased total flavonoid content; antioxidants; leaf K, P, Na, Cu and Zn content; and stomatal resistance, compared to the control. In both species, high EC did not affect polyphenols, flavonoids or antioxidants, whereas it increased stomatal resistance and nutrient accumulation in the leaves, and decreased chlorophyll fluorescence compared to the control treatment. Damage indices, indicated by lipid peroxidation, hydrogen peroxide production and the elevation of enzymes’ antioxidant activities, were evidenced in both saline- and high-EC-treated plants. In conclusion, despite having the same EC levels in the nutrient solution, it seems that ionic stress caused by high mineral concentrations in the nutrient solution had less severe effects on the tested plants than the relevant osmotic stress caused by high salinity due to the addition of NaCl in the nutrient solution.

Bio-assessment of wastewater effluent conditions with algal pollution index and multivariate approach

Water scarcity and water pollution are important issues in the world. Therefore, reusing treated wastewater for irrigation can be a crucial approach in arid and semi-arid regions. There are still some concerns about the sustainability of wastewater irrigated agriculture. Thereby, the present study is aimed to evaluate responses of algal species to stressors in the central wastewater treatment plant using the modified algae pollution index and multivariate approaches to assess healthy sustainability of wastewater effluent quality and to give the suggestion for reusing such kind of waters, especially for irrigation. Samplings of water and algae were carried out twice a month between October 2019 and August 2020. Canonical correspondence analysis (CCA) explained 94.1% of the relationships between environmental factors and species. Water and air temperatures, precipitation, chemical oxygen demand (COD), electrical conductivity (EC), pH, and NO3 played important roles in the temporal occurrence/succession of algae composition in the wastewater treatment plant. Ordination of commonly encountered algae species relatively near the center of the CCA indicates their wide range of tolerance levels to the changes in environmental conditions in the system. Of the species, Navicula aitchelbee, Nitzschia fonticola, and Euglena oxyuris preferred high EC levels; Brachysira exilis, Chlorella vulgaris, G. parvulum, and C. ovata associated with high COD levels, and Navicula tripunctata, Nitzschia umbonata and C. vulgaris related to high NO3 levels (>75% of the percentile). The modified pollution index developed in the present study indicated that the wastewater treatment plant had mainly high organic pollution (>3.00) in the summer and fall seasons, when it had moderate organic pollution (>2.50) in the winter and spring seasons. Results of the study suggest that crucial algae-stressors relationships can be used as an assessment tool to ensure sustainable water supply for the irrigation purpose in arid and semi-arid regions.

Electrical Conductivity of Spark Plasma Sintered W-Cu and Mo-Cu Composites for Electrical Contact Applications

Tungsten copper and molybdenum copper composites, with weight percent copper in the range of 20% - 40%, have been produced using the spark plasma sintering (SPS) technique. Other specimens having similar compositions were also developed using the conventional techniques of Liquid Phase Sintering (LPS) and Infiltration. Electrical conductivity measurements showed that the specimens produced by the SPS process had substantially higher levels of electrical conductivity than those produced by the other methods. Relative density measurements showed that the SPS specimens achieved very high densification, with relative densities in the range of 99.1% - 100%. On the other hand, the specimens produced by LPS and infiltration had relative densities in the range of 88% - 92% and 96% - 98% respectively. The superior conductivity of the SPS specimens has been attributed to the virtually full densification achieved by the process. The effect of porosity on electrical conductivity has been discussed and three standard models were assessed using results from porous sintered skeletons of pure tungsten and pure molybdenum.

Performance of a Pilot Subsurface Flow Treatment Wetland System, Used for Arsenic Removal from Reverse Osmosis Concentrate, in the Municipality of Julimes, Chihuahua, Mexico

The objective of this study was to implement a pilot system of treatment wetlands, using phytoremediation as an alternative technology to remove arsenic from the concentrate of a reverse osmosis system. The pilot system was composed of two subsurface flow constructed wetlands, planted with Eleocharis macrostachya and Shoenoplectus americanus. The wetlands were fed concentrate from a reverse osmosis system for seven months, with an average flow of 962 Ld-1 and an average arsenic concentration of 0.241 mgL-1. Removal rates between 43 % and 86 % were obtained for wetland 1 and between 35 % and 79 % for wetland 2 throughout the experiment. The two plant species developed normally despite the high levels of electrical conductivity in the range of 3584 to 5455 µscm-1 in wetland intake waters. The pilot wetland system removed significant levels of arsenic from the reverse osmosis concentrate, resulting in arsenic levels in the output waters that meet Mexican standard for using water in agricultural irrigation.

In-Situ and Ion Implantation Nitrogen Doping on Near Stoichiometric a-SiC:H Films

In this work we study the nitrogen n-type electrical doping of a-Si0.5C0.5:H films obtained by plasma enhanced chemical vapor deposition (PECVD) utilizing and comparing two doping techniques: in-situ (during the material growth) and ion implantation. The in-situ doped a-SiC:H films were obtained adding different amounts of N2 to the precursor gas mixture. For ion implantation four different nitrogen implanted concentrations were studied (between 1018 and 1021 atoms/ cm3) using multiple energies and doses to define a homogeneously doped layer. The doping experiments are carried out on a-SiC:H samples that present different structural order. The results show that high levels of electrical conductivity can be obtained with ion implantation technique. For in-situ technique the doping effect is also observed but must be improved in order to attain higher electrical conductivities. In the best case the room temperature dark conductivity for the sample implanted with 1021 nitrogens/cm3 was ~10-7 (Ω.cm)-1 and the activation energy was 0.2 eV. For in-situ doping the electrical dark conductivity reached values near 10-10 (Ω.cm)-1 at high temperatures and the activation energy was ~0.6 eV. Despite of the apparent low values of the electrical conductivity, these results are promising because we are dealing with a wide gap material and the doping processes are still not optimized.