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Featured Application: This study produced biochars from a conventional lab tube furnace vs. a Do-It-Yourself (DIY) biochar maker and compared the biochar properties and their efficacy for aqueous lead removal. It tested four different biomasses as feedstock materials. It would be a good reference for those who are considering household-scale biochar production and its application as a sorbent for cationic heavy metal. Biochar has proven its potential in removing heavy metal ions from water. The objective of this study was to evaluate locally obtained biomass feedstocks for biochar production and their efficiency as a sorbent for aqueous lead (Pb2+) removal. The biomass feedstocks consisted of avocado seed, avocado peel, grapefruit peel, and brown seaweed, which represent agricultural and marine biomasses. The biochar materials were produced in two different methods: (1) a laboratory tube furnace at 300 °C and (2) a Do-It-Yourself (DIY) biochar maker, "BioCharlie Log". The biochars were characterized for selected physicochemical properties, and batch adsorption tests with 10 mg Pb2+ L−1 were conducted. All biochars exhibited >90% Pb2+ removal with the avocado seed and grapefruit peel biochars being the most effective (99%) from the tube-furnace-produced biochars. BioCharlie-produced-biochars showed similar Pb2+ removal (90–97%) with brown seaweed and avocado seed biochars being the most effective (97%). Land-based biochars showed a higher carbon content (>53%) than the brown seaweed biochar (28%), which showed the highest ash content (68%). Our results suggested that oxygen-containing surface functional groups in land-based biochar and mineral (ash) fraction in marine-based biochar play a key role in Pb2+ removal. [ABSTRACT FROM AUTHOR]

South Texas is located in a subtropical semiarid climate, and due to high temperature and irregular precipitation, farmers opt to leave their fields fallow during the summer months jeopardizing overall soil health. We evaluated whether sweet potato (Ipomoea batatas) cultivation coupled with drip irrigation could restore soil biological activities compared with bare fallow. Additionally, because sweet potatoes have high demand of soil nutrients, especially potassium (K), we evaluated the nutrient supply of locally sourced soil amendments. Sweet potato was cultivated during summer 2018 in McAllen, Texas, under control (no fertilizer), NPK (synthetic fertilizer), RC (yard-waste compost), and AC (compost produced under an enhanced composting process), and biochar (gasified walnut shell at 900°C), each with three replicates. Soil amendments were applied at different amounts to result in a rate of 80 kg K ha−1. Soil biological indicators were microbial biomass phosphorous, phosphatase activity, and the rate of fluorescein diacetate hydrolysis (FDA). Available nitrogen, phosphorus, potassium, and sodium were also quantified. Aboveground biomass and storage root yield estimated sweet potato's agronomic performance. Cultivation and irrigation stimulated soil enzyme activities and microbial biomass-phosphorous. Sweet potato yields were the highest in NPK treatment but still 2.8 times lower than variety's potential yield. Storage root yield was inversely related to aboveground biomass, suggesting that growing conditions benefited the production of shoot versus roots. Both biochar and AC treatments stimulated FDA rates and K availability. Soil pH and sodium concentration increased in all treatments over the growing season, possibly due to river-sourced irrigation water. Together, these findings show that crop cultivation promoted soil biological activities and the maintenance of nutrient cycling, compared to bare-fallow conditions. For a better agronomic performance of sweet potato, it would be necessary to identify management practices that minimize increase in soil pH and salinity. [ABSTRACT FROM AUTHOR]

The fractal dimension of random walker (FDRW) is an important parameter for description of electrical conductivity in porous media. However, it is somewhat empirical in nature to calculate FDRW. In this paper, a simple relation between FDRW and tortuosity fractal dimension (TFD) of current streamlines is derived, and a novel method of computing TFD for different generations of two-dimensional Sierpinski carpet and three-dimensional Sierpinski sponge models is presented through the finite element method, then the FDRW can be accordingly predicted; the proposed relation clearly shows that there exists a linear relation between pore fractal dimension (PFD) and TFD, which may have great potential in analysis of transport properties in fractal porous media. [ABSTRACT FROM AUTHOR]

Background and aims: Knowledge of plant water fluxes is critical for assessing mechanistic processes linked to biogeochemical cycles, yet resolving root water transport dynamics has been a particularly daunting task. Our objectives were to demonstrate the ability to non-invasively monitor individual root functionality and water fluxes within Zea mays L. (maize) and Panicum virgatum L. (switchgrass) seedlings using neutron imaging. Methods: Seedlings were propagated for 1-3 weeks in aluminum chambers containing sand. Pulses of water or deuterium oxide were then tracked through the root systems by collecting consecutive radiographs during exposure to a cold-neutron source. Water flux was manipulated by cycling on a growth lamp to alter foliar demand for water. Results: Neutron radiography readily illuminated root structure, root growth, and relative plant and soil water content. After irrigation there was rapid root water uptake from the newly wetted soil, followed by hydraulic redistribution of water through the root system to roots terminating in dry soil. Water flux within individual roots responded differentially to foliar illumination based on supply and demand of water within the root system. Conclusions: Sub-millimeter scale image resolution revealed timing and magnitudes of root water uptake, redistribution within the roots, and root-shoot hydraulic linkages-relationships not well characterized by other techniques. [ABSTRACT FROM AUTHOR]

There is significant concern in water utilities regarding the permeation of petroleum-based hydrocarbons from contaminated sites through potable drinking-water pipes made of polyvinyl chloride (PVC). Previous studies have addressed the impacts of hydrocarbons on the pipe materials, but the impacts of the hydrocarbons on gasket materials joining and sealing the pipes have not been investigated. This study investigated the permeation of benzene, toluene, ethylbenzene, and xylene (BTEX) compounds through PVC pipe joints equipped with 50-mm styrene-butadiene rubber (SBR) and nitrile-butadiene rubber (NBR) Rieber gaskets exposed to various levels of gasoline contamination. Results of permeation experiments with premium gasoline indicated that permeation occurred only through the gaskets and not through the intact pipe materials. For experiments with premium gasoline, benzene was the first compound detected with a breakthrough time of approximately 21 days. However, for experiments with various gasoline concentrations in water, including water saturated with gasoline, no significant amounts of BTEX compounds were detected in the pipe water after 9 months of exposure. The steady-state permeation rates of benzene when exposed to premium gasoline were found to be 0.73±0.29 and 0.38±0.32 mg/joint/day for SBR and NBR gaskets, respectively. The corresponding diffusion coefficients of benzene in SBR and NBR gaskets (which have not been reported before) were determined to be 1.1×10-7 and 6.0×10-8 cm2/s, respectively, by curve fitting the permeation data with a diffusion model. Although PVC pipe joints were found to be permeated by free-product gasoline, water flow in pipes would dilute the benzene in drinking water to below the maximum contamination level (MCL) of 5 μg/L. [ABSTRACT FROM AUTHOR]

Organic contaminants may permeate through plastic pipes in water distribution systems and adversely affect the quality of drinking water. In this study, we developed a microscopic visualization technique to investigate the permeation of common organic contaminants (benzene, toluene, ethylbenzene, xylene, and trichloroethene) through polyvinyl chloride (PVC) pipes. By observing the propagation of organic moving fronts in the pipe materials with a light microscope, the technique was able to predict the permeation breakthrough times through PVC pipes that were determined in the pipe-bottle test. The advance of an organic moving front was found to be linearly dependent on the square-root of time and the propagation rate increased with an increase in the external organic chemical activity. Permeation of organic mixtures into PVC pipes was found to be additive in proportion to the permeation rates and volume percents of each component. In combination with a 2-year pipe-bottle test for PVC pipes exposed to premium gasoline, mathematical extrapolations based on the microscopic visualization tests predicted that PVC pipe are likely to resist permeation by commercial gasoline for the service life of the pipe. [ABSTRACT FROM AUTHOR]

Background: Our recent publication (Warren et al., Plant Soil 366:683-693, ) described how pulses of deuterium oxide (DO) or HO combined with neutron radiography can be used to indicate root water uptake and hydraulic redistribution in maize. This technique depends on the large inherent differences in neutron cross-section between D and H atoms resulting in strong image contrast. Scope and Conclusions: However, as illustrated by Carminati and Zarebanadkouki () there can be a change in total water content without a change in contrast simply by a change in the relative proportions of DO and HO. We agree with their premise and detailed calculations (Zarebanadkouki at al. , ), and present further evidence that mixing of DO and HO did not confound evidence of hydraulic redistribution in our study. [ABSTRACT FROM AUTHOR]