Search Results (18)

Porcine reproductive and respiratory syndrome (PRRS) is an endemic disease affecting the swine industry. The disease is caused by the PRRS virus (PRRSV). Despite extensive biosecurity and control measures, the persistence and seasonality of the virus have raised questions about the virus’s environmental dynamics during the fall season when the yearly epidemic onset begins and when crop harvesting and manure incorporation into the field occur. Therefore, this study aimed to assess the potential for PRRSV to percolate through different soil types, simulating conditions that could lead to groundwater contamination which could represent a risk of herd introduction. An experimental soil column model was used to mimic field conditions. Three PRRSV-2 strains were tested across thirteen Minnesota soils with different physical and chemical characteristics. The findings revealed that PRRSV can percolate through all soil types and that the amount of virus percolated decreases with increased amounts of soil. These results suggest that PRRSV can percolate through different soil types. Further investigations should be undertaken to determine the associated implications for swine health and biosecurity measures. Full article

Natural laterite fixed-bed columns intercalated with two types of layers (inert materials, such as fine sand and gravel, and adsorbent materials, such as activated carbon prepared from Balanites aegyptiaca (BA-AC)) were used for As(III) removal from an aqueous solution. Investigations were carried out to solve the problem of column clogging, which appears during the percolation of water through a natural laterite fixed-bed column. Experimental tests were conducted to evaluate the hydraulic conductivities of several fixed-bed column configurations and the effects of various parameters, such as the grain size, bed height, and initial As(III) concentration. The permeability data show that, among the different types of fixed-bed columns investigated, the one filled with repeating layers of laterite and activated carbon is more suitable for As(III) adsorption, in terms of performance and cost, than the others (i.e., non-intercalated laterite; non-intercalated activated carbon, repeating layers of laterite and fine sand; and repeating layers of laterite and gravel). A study was carried out to determine the most efficient column using breakthrough curves. The breakthrough increased from 15 to 85 h with an increase in the bed height from 20 to 40 cm and decreased from 247 to 32 h with an increase in the initial As(III) concentration from 0.5 to 2 mg/L. The Bohart–Adams model results show that increasing the bed height induced a decrease in the k_AB and N₀ values. The critical bed depths determined using the bed depth service time (BDST) model for As(III) removal were 15.23 and 7.98 cm for 1 and 20% breakthroughs, respectively. The results show that the new low-cost adsorptive porous system based on laterite layers with alternating BA-AC layers can be used for the treatment of arsenic-contaminated water. Full article

Seaweeds, also known as marine macroalgae, are renewable biological resources that are found worldwide and possess a wide variety of secondary metabolites, including tannins. Drifted brown seaweed (DBSW) is particularly rich in tannins and is regarded as biological trash. The cotton leaf hopper Amrasca devastans (Distant) has caused both quantitative and qualitative losses in cotton production. Drifted brown seaweeds (DBSWs) were used in this study to extract, qualitatively profile, and quantify the levels of total tannins, condensed tannins, hydrolyzable tannins, and phlorotannins in the seaweeds; test their insecticidal activity; and determine the mechanism of action. The largest amount of tannin extract was found in Sargassum wightii Greville (20.62%) using the Soxhlet method (SM). Significantly higher amounts of hydrolyzable tannins (p = 0.005), soluble phlorotannins (p = 0.005), total tannins in the SM (p = 0.003), and total tannins in the cold percolation method (p = 0.005) were recorded in S. wightii. However, high levels of condensed tannins (CTAs) were observed in Turbinaria ornata (Turner) J. Agardh (p = 0.004). A. devastans nymphs and adults were examined for oral toxicity (OT) and contact toxicity (CT) against DBSW tannin crude extract and column chromatographic fractions 1 (Rf = 0.86) and 2 (Rf = 0.88). Stoechospermum polypodioides (J.V. Lamouroux) J. Agardh crude tannin was highly effective against A. devastans using the OT method (LC₅₀, 0.044%) when compared with the standard gallic acid (LC₅₀, 0.044%) and tannic acid (LC50, 0.122%). Similarly, S. wightii fraction 2 (LC₅₀, 0.007%) showed a greater insecticidal effect against A. devastans adults in OT than gallic acid (LC₅₀, 0.034%) and tannic acid (LC₅₀, 0.022%). The mechanism of action results show that A. devastans adults treated with crude tannin of T. ornata had significantly decreased amylase, protease (p = 0.005), and invertase (p = 0.003) levels when compared with the detoxification enzymes. The levels of glycosidase, lactate dehydrogenase, esterase, lipase, invertase, and acid phosphate activities (p = 0.005) of S. wightii were reduced when compared with those of the Vijayneem and chemical pesticide Monocrotophos. In adult insects treated with LC₅₀ concentrations of S. wightii tannin fraction 1, the total body protein (9.00 µg/µL) was significantly reduced (OT, LC₅₀—0.019%). The SDS-PAGE analysis results also show that S. wightii tannin fraction 1 (OT and CT), fraction 2 (OT), and S. polypodioides fraction 2 (CT) had a significant effect on the total body portion level, appearance, and disappearance of some proteins and polypeptides. This study shows that the selected brown macroalgae can be utilized for the safer management of cotton leaf hoppers. Full article

The permeability of crushed coal bodies plays a bottom neck role in seepage processes, which significantly limits the coal resource utilisation. To study the permeability of crushed coal bodies under pressure, the particle size distribution of crushed coal body grains is quantitatively considered by fractal theory. In addition, the parameters of the percolation characteristics of crushed coal body grains are calculated. Moreover, the permeability of the crushed coal body during recrushing is determined by the fractal dimension and porosity. A lateral limit compression test with the crushed coal bodies was carried out to illustrate the effect of the porosity on the permeability, In addition, a compressive crushed coal body size fractal–permeability model was proposed by combination of the fractal dimension and the non-Darcy equivalent permeability. The results show (1) the migration and loss of fine particles lead to a rapid increase in the porosity of the crushed coal body. (2) Increases in the effective stress cause the porosity and permeability to decrease. When the porosity decreases to approximately 0.375, its effect is undermined. (3) The migration and loss of fine particles change the pore structure and enhance the permeability properties of the skeleton, causing sudden seepage changes. (4) At low porosity, the permeability k is slightly larger than the non-Darcy equivalent permeability ke. Thus, the experimental data show an acceptable agreement with the present model. A particle size fractal–percolation model for crushed coal bodies under pressure provides a solution for effectively determining the grain permeability of the crushed coal bodies. The research results can contribute to the formation of more fractal-seepage theoretical models in fractured lithosphere, karst column pillars and coal goaf, and provide theoretical guidance for mine water disaster prevention. Full article

This paper examines the environmental impact of the use of compacted sewage sludge:red gypsum (SS:RG) mixture as intermediate landfill cover in terms of yield and quality of leachate as characterised by hydraulic conductivity and leaching behaviour. A series of column tests using the constant head method is carried out by percolating the synthetic leachate through samples that have been compacted at various degrees (60, 70, 75, 80 and 85%). The leachate quality is monitored at pre-determined days for pH, COD, Cu, Fe and Zn. In general, hydraulic conductivity decreases in three stages, in which the first stage is mainly attributed to the particle rearrangement and hydration of calcium silicate hydrate (CSH). The hydration of CSH increases the pH, which causes the heavy metal to precipitate and be entrapped within the matrices of CSH gel, thereby further reducing the porosity and hydraulic conductivity. A minimum of 75% compaction has shown favourable final porosity, hydraulic conductivity, and leachate quality, although a minimum of 80% compaction is recommended in order to achieve a satisfactory compressive strength of greater than 345 kPa for a landfill operation. Full article

In view of the potential soil leaching risk of the reuse of fertilizer reclaimed from micro-flush sanitary wastewater, the batch tests of soil adsorption and degradation, soil column percolation test and multi-stage soil box percolation test were adopted. The characteristics of leachate after the interaction between reclaimed fertilizer and soil, as well as the changes of soil attributes in the soil box system, were analyzed. After obtaining the correlation coefficients of solute transport in soil through the above experiments, the HYDRUS-1D model was constructed to simulate the solute migration and transformation in the soil with a duration of 1 year and a soil thickness of 5 m. The impacts of leachate on groundwater and soil were analyzed. The results showed that the adsorption intensity of total ammonia nitrogen (TAN) ($\frac{1}{n}=0.8009$) in the tested soil was lower than that of chemical oxygen demand (COD) ($\frac{1}{n}=1.1830$). The HYDRUS prediction showed that concentrations of TAN and COD at the soil depth of 5 m were 0, while total nitrogen (TN) still had a concentration of 0.11 mg/L. However, the TN leaching into the deep soil mainly came from the soil itself. The TAN at 3.4 m soil showed an upward trend in the prediction period. In addition, the reuse of reclaimed fertilizer can expand the soil nutrient inventory, which is conducive to the improvement of soil fertility. It can be concluded that the soil leaching risk of reuse of reclaimed fertilizer is not significant in the short term (one year). However, the risk of fertilization on soil with high-nitrogen background value should be paid attention to in the long term. Full article

Nanoscale titanium dioxide (nTiO₂ (Hombikat UV 100 WP)) was applied to sewage sludge that was incinerated in a large-scale waste treatment plant. The incineration ash produced was applied to soil as fertilizer at a realistic rate of 5% and investigated in pilot plant simulations regarding its leaching behavior for nTiO₂. In parallel, the applied soil material was subject to standard column leaching (DIN 19528) in order to test the suitability of the standard to predict the leaching of nanoscale contaminants from treated soil material. Relative to the reference material (similar composition but without nTiO₂ application before incineration) the test material had a total TiO₂ concentration, increased by a factor of two or 3.8 g/kg, respectively. In contrast, the TiO₂ concentration in the respective leachates of the simulation experiment differed by a factor of around 25 (maximum 91.24 mg), indicating that the added nTiO₂ might be significantly mobilisable. Nanoparticle specific analysis of the leachates (spICP-MS) confirmed this finding. In the standard column elution experiment the released amount of TiO₂ in the percolates between test and reference material differed by a factor of 4 to 6. This was also confirmed for the nTiO₂ concentrations in the percolates. Results demonstrate that the standard column leaching, developed and validated for leaching prediction of dissolved contaminants, might be also capable to indicate increased mobility of nTiO₂ in soil materials. However, experiments with further soils are needed to verify those findings. Full article

The recycling of mineral materials is a sustainable and economical approach for reducing solid waste and saving primary resources. However, their reuse may pose potential risks of groundwater contamination, which may result from the leaching of organic and inorganic substances into water that percolates the solid waste. In this study, column leaching tests were used to investigate the short- and long-term leaching behavior of “salts”, “metals”, and organic pollutants such as PAHs and herbicides from different grain size fractions of construction & demolition waste (CDW) and railway ballast (RB) after a novel treatment process. Specifically, silt, sand and gravel fractions obtained after a sequential crushing, sieving, and washing process (“wet-processing”) of very heterogeneous input materials are compared with respect to residual contamination, potentially limiting their recycling. Concentrations in solid fractions and aqueous leachate were evaluated according to threshold values for groundwater protection to identify relevant substances and to classify materials obtained for recycling purposes according to limit values. For that, the upcoming German recycling degree was applied for the first time. Very good agreement was observed between short and extensive column tests, demonstrating that concentrations at L/S 2 ratios are suitable for quality control of recycling materials. Different solutes showed a characteristic leaching behavior such as the rapid decrease in “salts”, e.g., SO₄²⁻ and Cl⁻, from all solid fractions, and a slower decrease in metals and PAHs in the sand and silt fractions. Only the gravel fraction, however, showed concentrations of potential pollutants low enough for an unlimited re-use as recycling material in open technical applications. Sand fractions may only be re-used as recycling material in isolated or semi-isolated scenarios. Leaching from heterogeneous input materials proved harder to predict for all compounds. Overall, column leaching tests proved useful for (i) initial characterization of the mineral recycling materials, and (ii) continuous internal (factory control) and external quality control within the upcoming German recycling decree. Results from such studies may be used to optimize the treatment of mixed solid waste since they provide rapid insight in residual pollution of material fractions and their leaching behavior. Full article

Arsenic in the soil can leach into groundwater and contaminate drinking water, posing a serious risk to human health. The stabilization of arsenic in contaminated soil is one of the immobilization technologies used to remediate contaminated lands. However, few studies have evaluated the long-term release of As and pH changes in stabilized soils. We compared different stabilization techniques in the field by mixing contaminated soil with 5% of either acid mine drainage sludge (AMDS), coal mine drainage sludge (CMDS), steel slag, or cement. We evaluated the results using an up-flow percolation column test to observe any pH changes and As releases from the stabilized soils up to a liquid–solid (L/S) ratio of 50 (approximately representing a 50 year period). At the initial stage of percolation (at an L/S ratio of 0.2 or 0.2 of a year of exposure), some alkaline components and any incompletely bound As in the soils washed out with the eluent. The pH of the cement-stabilized soil was approximately 12 throughout the experiment (up to 50 L/S). Adding stabilizers to the soil reduced As leaching by 54–81% (overall efficiency) compared to the control (contaminated soil only). The order of stabilization efficiency was: steel slag (55.0%) < AMDS (74.3%) < cement (78.1%) < CMDS (81.5%). This study suggests that the groundwater of the stabilized soil should be carefully monitored for the initial five years because the soluble ionic species can leach over this period. Full article

Initial conditions (pre-equilibrium or after the first flooding of the column), mass transfer mechanisms and sample composition (heterogeneity) have a strong impact on leaching of less and strongly sorbing compounds in column percolation tests. Mechanistic models as used in this study provide the necessary insight to understand the complexity of column leaching tests especially when heterogeneous samples are concerned. By means of numerical experiments, we illustrate the initial concentration distribution inside the column after the first flooding and how this impacts leaching concentrations. Steep concentration gradients close to the outlet of the column have to be expected for small distribution coefficients ($K_d<1$ L kg⁻¹) and longitudinal dispersion leads to smaller initial concentrations than expected under equilibrium conditions. In order to elucidate the impact of different mass transfer mechanisms, film diffusion across an external aqueous boundary layer (first order kinetics, FD) and intraparticle pore diffusion (IPD) are considered. The results show that IPD results in slow desorption kinetics due to retarded transport within the tortuous intragranular pores. Non-linear sorption has not much of an effect if compared to $K_d$ values calculated for the appropriate concentration range (e.g., the initial equilibrium concentration). Sample heterogeneity in terms of grain size and different fractions of sorptive particles in the sample have a strong impact on leaching curves. A small fraction (<1%) of strongly sorbing particles (high $K_d$) carrying the contaminant may lead to very slow desorption rates (because of less surface area)—especially if mass release is limited by IPD—and thus non-equilibrium. In contrast, mixtures of less sorbing fine material (“labile” contamination with low $K_d$), with a small fraction of coarse particles carrying the contaminant leads to leaching close to or at equilibrium showing a step-wise concentration decline in the column effluent. Full article

Adsorption parameters such as the distribution coefficient are required to predict the release behavior of contaminants using advection-dispersion models. However, for potentially contaminant-releasing materials (PCMs) such as dredged sludge and coal ash, these parameters cannot be obtained by conventional adsorption tests. This study developed a method to determine adsorption parameters for PCMs from a set of batch tests conducted in parallel as a function of the liquid-solid ratio (LS-parallel test). This LS-parallel test was performed on sandy soil derived from marine sediment using liquid-solid ratios from 1 to 300 L/kg. The water-contact time was also changed from 10 min to 28 d to elucidate the kinetics or equilibrium of contaminants released from the sample. Adsorption parameters were successfully obtained if the substance was under adsorption control. A column percolation test was performed to confirm the effectiveness of the obtained parameters. Good agreements were observed for SO₄²⁻ and B, but discrepancies remained for other substances such as F⁻ and As suggesting that improvements are necessary in both the LS-parallel test procedure and the advection-dispersion model. Full article

The behaviour of capillary barrier covers (CBCs) subjected to rainfall has been extensively studied by many researchers. However, the patterns of rainfall are seldom considered in previous studies, and therefore, the behaviour of CBCs subjected to rainfall with different patterns is still unknown. To this end, this study aims to investigate the effect of rainfall patterns on the behaviour and performance of CBCs, and identify the rainfall pattern, under which the performance of the CBC is the worst. Using a newly developed soil column test apparatus, a series of laboratory soil column experiments were conducted. The results indicated that when rainfall duration is short, the patterns of rainfall only affect the volume water content (VWC) and pore water pressure (PWP) significantly at the upper part of the column; when rainfall duration is long, the patterns of rainfall can significantly affect the VWC and PWP throughout the whole column. The percolation and breakthrough time of the CBC were also influenced by rainfall patterns; the advanced rainfall pattern produced the largest percolation, and resulted in the shortest time for CBCs to break through, whereas the delayed rainfall pattern generated the least percolation and resulted in the longest time for CBCs to break through. Based on the percolation and breakthrough time, it seems that the advanced pattern is the worst-case scenario for the CBCs subjected to rainfall. The obtained results not only imply the necessity of rainfall patterns to be involved in the study of the CBCs subjected to rainfall but they also can be helpful for the practical design of the CBCs. Full article

In this study, a granular material (GM) derived from wastes generated in waste-to-energy plants was developed. Weathered bottom ash (WBA) and air pollution control (APC) ashes obtained from municipal solid waste incineration (MSWI) were used as raw materials. A mortar (M) with 50 wt. % of APC and 50 wt. % of Ordinary Portland Cement (OPC) CEM-I was prepared. The GM formulation was 20 wt. % M and 80 wt. % WBA. At the laboratory scale, WBA, APC, M, and crushed GM were evaluated by means of dynamic leaching (EN 12457-4) tests, and WBA, M, and crushed GM by percolation column (CEN/TS 16637) tests. The metal(loid)s analyzed were below the non-hazardous limits, regarding the requirement of the metal(loid)s released for waste revalorization. In order to simulate a road subbase real scenario, the crushed GM was tested in an experimental section (10 × 20 × 0.2 m). During a 600-day period, the leachates generated by the percolation of rainwater were collected. This research shows outstanding results regarding the metal(loid)s released for both the “accumulated” and “punctual” leachates collected. An accomplishment in the immobilization of metal(loid)s from APC residues was achieved because of the encapsulation effect of the cement. The GM formulation from both MSWI wastes can be considered an environmentally safe procedure for revalorizing APC residues. Full article

Low-grade magnesium oxide (LG-MgO) was proposed as ordinary Portland cement (OPC) or lime substitute (CaO) for metal(loid)s remediation in contaminated soils. Some metal(loid)s precipitate at pH ≈ 9 in insoluble hydroxide form thus avoiding their leaching. LG-MgO avoids the re-dissolution of certain metal(loid)s at 9.0 < pH < 11.0 (pH-dependents), whose solubility depends on the pH. A highly contaminated soil with heavy metal(loid)s was stabilized using different LG-MgO by-products sources as stabilizing agents. Two of the three studied LG-MgOs were selected for the stabilization, by mixing 5, 10, and 15 wt.%. The effect of using LG-MgO not only depends on the size of the particles, but also on those impurities that are present in the LG-MgO samples. Particle size distribution, X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetric analysis, citric acid test, specific surface, bulk density, acid neutralization capacity, batch leaching tests (BLTs), and percolation column tests (PCTs) were techniques used to deeply characterize the different LG-MgO and the contaminated and remediated soils. The remediation’s results efficacy indicated that when the medium pH was between 9.0 and 11.0, the concentration of pH-dependent metal(loid)s decreases significantly. Although around 15 wt.% of a stabilizing agent was appropriate for the soil remediation to ensure an alkali reservoir that maintains optimal stabilization conditions for a long period, 5 wt.% of LG-MgO was enough to remedy the contaminated soil. When evaluating a polluted and decontaminated soil, both BLTs and PCTs should be complementary procedures. Full article

In this paper, an all-solid-state nitrate doped polypyrrole (PPy(NO₃⁻) ion-selective electrode (ISE) was prepared with a nanohybrid composite film of gold nanoparticles (AuNPs) and electrochemically reduced graphene oxide (ERGO). Preliminary tests on the ISE based in-situ soil nitrate–nitrogen (NO₃⁻-N) monitoring was conducted in a laboratory 3-stage column. Comparisons were made between the NO₃⁻-N content of in-situ soil percolate solution and laboratory-prepared extract solution. Possible influential factors of sample depth, NO₃⁻-N content, soil texture, and moisture were varied. Field-emission scanning electron microscopy (FESEM) and X-ray powder diffraction (XRD) characterized morphology and content information of the composite film of ERGO/AuNPs. Due to the performance excellence for conductivity, stability, and hydrophobicity, the ISE with ERGO/AuNPs illustrates an acceptable detection range from 10⁻¹ to 10⁻⁵ M. The response time was determined to be about 10 s. The lifetime was 65 days, which revealed great potential for the implementation of the ERGO/AuNPs mediated ISE for in-situ NO₃⁻-N monitoring. In-situ NO₃⁻-N testing results conducted by the all-solid-state ISE followed a similar trend with the standard UV-VIS method. Full article