Growth and phytoremediative capacity of Eleusine indica in a typical farmland soil under previous exposure to organochlorine pesticide

This study investigated the growth and phytoremediative response of Eleusine indica in a typical farmland soil that had been exposed to organochlorine pesticides. Different soil treatments were obtained by mixing pesticide polluted soil (P) with control soil (C) in ratios, 1P:99C, 5P:95C, 50P:50C, 25P:75C, 75P:25C, 100P and 100C. Three-leaf tillers of the test plant were sown in all the treatments for 3 months. The results revealed that there were no significant differences in all plant morphological parameters measured between plants in P impacted soils and C-soil. All the pH values were acidic, although an increase in pH and decrease in conductivity was observed with the introduction of the test plant. There was reduction in total pesticide residual (TPR) contents in the soil as a result of the plant activities. Significant reduction in q – BHC, α – chlordane and ϒ – chlordane was observed in the P1:C99 soil mix; a 90% remediation efficiency (1.663 mg kg-1 ) was registered in the all treatments. This study thus presents E. indica as a potential concentration-dependent phytoremediator of pesticide, with no significant morphological changes.

Vertical Barriers for Land Contamination Containment: A Review

Soil pollution is one of the major threats to the environment and jeopardizes the provision of key soil ecosystem services. Vertical barriers, including slurry trench walls and walls constructed with soil mix technology, have been employed for decades to control groundwater flow and subsurface contaminant transport. This paper comprehensively reviewed and assessed the typical materials and mechanical and permeability properties of soil–bentonite, cement–bentonite and soil mix barriers, with the values of mix design and engineering properties summarized and compared. In addition, the damage and durability of barrier materials under mechanical, chemical, and environmental stresses were discussed. A number of landmark remediation projects were documented to demonstrate the effectiveness of the use of barrier systems. Recent research about crack-resistant and self-healing barrier materials incorporating polymers and minerals at Cambridge University and performance monitoring techniques were analyzed. Future work should focus on two main areas: the use of geophysical methods for non-destructive monitoring and the optimization of resilient barrier materials.

Effect of Polypropylene Fibers on the Shear Strength–Dilation Behavior of Compacted Lateritic Soils

The stress–dilatancy relationship for fiber-reinforced soils has been the focus of recent studies. This relationship can be used as a foundation for the development of constitutive models for fiber-reinforced soils. The present study aims to investigate the effect of recycled polypropylene fibers on the shear strength–dilation behavior of two lateritic soils using the stress–dilatancy relationship for direct shear tests. Results show that fibers improved the shear strength behavior of the composites, observed by increases in the friction angle. Fibers’ orientation at the sheared interface could be observed. The volumetric change during shearing was altered by the presence of fibers in both soils. Overall, results indicate that the stress–dilatancy relationship is affected by inclusions in the soil mix. Results can be used to implement constitutive modeling for fiber-reinforced soils.

Experimental Investigation on Mechanical Properties of Compressed Soil Blocks Manufactured Using Waste Materials

This experimental investigation is done on the earth compressed block prepared by the Waste material. These waste materials are Rice Straw Fiber, marble powder, and Sugarcane Bagasse ash. This waste pollutesthe environment and creates the problem of disposal. Redbrick needs heat treatment which results in air pollution, cement bricks need water for curing which needs waterusage in huge quantity. Marble powder stabilized bricks need sun drying. An increase in marble content in the bricks results in the increment of compressive strength due to the presence of calcium content in the marble powder.it also increases the dry density of the brick because marble powder doesnot absorbs water and can easily fill the voids created by the soil,Sugarcene Bagasse ash andRice Straw fiber. Rice Straw Fiber reduces the compression of bricks reason is fiber cuts off on the pressure and it also creates voids when blended with the soil mix making usage of bagasse in the brick can help in increasing the strength of the concrete due to its pozzalonic action with cement but bagasse ash reduces the dry density of bricks and doesnot affect the strength of bricks because its creates voids and it is chemically neutral in bricks.

Impact of Green Stormwater Infrastructure Age and Type on Water Quality

Green stormwater infrastructure (GSI) has become increasingly common to mitigate urban stormwater runoff. However, there is limited research on the impact of age and type of GSI. This study evaluated nutrient and metals concentrations in the soil water of five different GSI systems located at the University of Portland in Portland, Oregon. The GSI systems included a bioretention curb extension (part of Portland’s Green Street project), a bioretention basin, a bioretention planter, an infiltration basin, and a bioswale ranging in age from 2 to 11 years. Samples were taken from each system during rain events over a 10-month period and analyzed for copper (Cu), zinc (Zn), phosphate (PO43−), and total phosphorus (TP). Copper and zinc concentrations were found to be impacted by GSI age, with lower concentrations in older systems. The same trend was not found with PO43− and TP, where almost all GSI systems had soil water concentrations much higher than average stormwater concentrations. Age likely played a role in phosphorus soil water concentrations, but other factors such as sources had a stronger influence. Phosphorus is likely coming from the compost in the soil mix in addition to other sources in runoff. This study shows that GSI systems can be effective for copper and zinc, but changes to the soil mix design are needed to reduce high levels of PO43− and TP in soil water.

Effects of Scarification, Phytohormones, Soil Type, and Warming on the Germination and/or Seedling Performance of Three Tamaulipan Thornscrub Forest Species

The Tamaulipan thornforests of south Texas and northeast Mexico are an ecologically and economically important conservation hotspot. Thornforest restoration is limited by native tree and shrub seedling availability for planting. Seedling shortages arise from low seed availability and knowledge gaps regarding best practices for germinating and growing the 70+ thornforest species desired for restoration plantings. To fill key knowledge gaps, we investigated three ecologically important thornforest species with low or highly variable germination or seedling survival rates: Ebenopsis ebano, Cordia boissieri, and Zanthoxylum fagara. For each, we quantified the effects of different dosages of chemical seed treatments used to promote germination (sulfuric acid, SA; gibberellic acid, GA; indole-3-butyric acid, IBA) on germination likelihood and timing. We also quantified the effects that these chemical seed treatments, soil media mixture type, and soil warming had on seedling survival, growth, and root morphology. Ebenopsis germination peaked (>90%) with 40–60 min SA treatment. Cordia germination peaked (40%) with 100 mg/L GA treatment. Zanthoxylum germination was negligible across all treatments. Seed molding was rare but stirring during SA treatment reduced Ebenopsis molding by 4%. Ebenopsis seedling survival, height, leaf count, and root morphology were minimally affected by seed treatments, generally reduced by warming, and influenced by soil mix, which also mediated responses to warming. These results suggest improvements to existing practices that could increase Ebenopsis germination by 10–20% and potentially double Cordia germination.

The effect of applied salinity and water stress on chemical suppression of Phytophthora ramorum from soilborne inoculum in Rhododendron

A serious concern for nurseries is the potential for Phytophthora ramorum and other Phytophthora species to colonize roots without inducing aboveground symptoms in plants that then serve as cryptic reservoirs of inoculum. Episodic abiotic stresses that reduce plant water potential can compromise host resistance to trigger disease development from root and crown infections in many Phytophthora-plant interactions. We conducted a series of experiments with root-inoculated Rhododendron plants in a potting soil mix to assess influence of excess salt or water deficit on ramorum blight development and the potential for these abiotic stresses to affect efficacy of oomycete-suppressive chemical soil treatments. In growth chamber trials, P. ramorum colonized roots in both non-salted and salt-treated plants. However, salt treatment offset the benefit realized from soil treatment with mefanoxam (Subdue Maxx) or mandipropamid (Micora), as evidenced by enhanced pathogen colonization of roots. A three-week episode of water stress imposed after chemical treatment but prior to inoculation eliminated protection against P. ramorum root colonization conferred by fosetyl-Al (Aliette). In an outdoor experimental nursery, foliar symptoms were apparent in 23% of root-inoculated plants in two trials and absent in one trial. However, the majority of inoculated plants in all trials had colonized roots with little or no aboveground symptoms. A single application of Subdue Maxx or Aliette reduced root colonization by P. ramorum in Rhododendron plants. Although salt stress did not enhance ramorum blight symptom expression in the nursery, salt partially offset protection from P. ramorum root colonization obtained by Subdue Maxx.