Contributing Area and Concentration Effects on Herbicide Removal by Vegetative Buffer Strips

Deteriorated water quality due to nonpoint source pollution from herbicides is one of the environmental problems receiving attention this decade. One off-site best management practice (BMP) being suggested to improve water quality is vegetative buffer strips. This study was conducted on a Storden loam soil, under simulated rainfall (6.35 cm/h), to determine the effects of nominal inflow concentration (0.1 and 1.0 mg/L) and the ratio of drainage area to vegetated buffer strip area (simulated to be 15:1 and 30:1) on the efficiency of vegetative buffer strips (12.2 m long) in removing herbicides dissolved in runoff water. Four treatments (2 ¥ 2 factorial) replicated three times were included in the study. Three inflow samples (each integrated over 15 min) and nine outflow samples (each integrated over 5 min) were collected from each plot and analyzed for three herbicides. Reductions of 41, 39, and 38% from plots having a relative area ratio of 15:1, and 37, 35, and 34% from plots having a relative area ratio of 30:1 were measured, respectively, for atrazine, metolachlor, and cyanazine. Although the percentage of removal decreased for the larger area ratios for each herbicide, the decreases were not significant. Reductions of 29, 30, and 28% from plots having 0.1 mg/L nominal inflow concentration, and 49, 44, and 45% from plots having 1.0 mg/L nominal inflow concentration were measured, respectively, for atrazine, metolachlor, and cyanazine. The differences between reductions for the nominal inflow concentrations were significant. Using a bromide tracer, it was determined that the major factor in reduction of herbicide transport was infiltration of inflow into the vegetative buffer strips

Agent-Based Model of Therapeutic Adipose-Derived Stromal Cell Trafficking during Ischemia Predicts Ability To Roll on P-Selectin

Intravenous delivery of human adipose-derived stromal cells (hASCs) is a promising option for the treatment of ischemia. After delivery, hASCs that reside and persist in the injured extravascular space have been shown to aid recovery of tissue perfusion and function, although low rates of incorporation currently limit the safety and efficacy of these therapies. We submit that a better understanding of the trafficking of therapeutic hASCs through the microcirculation is needed to address this and that selective control over their homing (organ- and injury-specific) may be possible by targeting bottlenecks in the homing process. This process, however, is incredibly complex, which merited the use of computational techniques to speed the rate of discovery. We developed a multicell agent-based model (ABM) of hASC trafficking during acute skeletal muscle ischemia, based on over 150 literature-based rules instituted in Netlogo and MatLab software programs. In silico, trafficking phenomena within cell populations emerged as a result of the dynamic interactions between adhesion molecule expression, chemokine secretion, integrin affinity states, hemodynamics and microvascular network architectures. As verification, the model reasonably reproduced key aspects of ischemia and trafficking behavior including increases in wall shear stress, upregulation of key cellular adhesion molecules expressed on injured endothelium, increased secretion of inflammatory chemokines and cytokines, quantified levels of monocyte extravasation in selectin knockouts, and circulating monocyte rolling distances. Successful ABM verification prompted us to conduct a series of systematic knockouts in silico aimed at identifying the most critical parameters mediating hASC trafficking. Simulations predicted the necessity of an unknown selectin-binding molecule to achieve hASC extravasation, in addition to any rolling behavior mediated by hASC surface expression of CD15s, CD34, CD62e, CD62p, or CD65. In vitro experiments confirmed this prediction; a subpopulation of hASCs slowly rolled on immobilized P-selectin at speeds as low as 2 µm/s. Thus, our work led to a fundamentally new understanding of hASC biology, which may have important therapeutic implications

Fate of fall and spring applied metolachlor

Fall application of metolachlor may reduce pollution because the gentle fall rains are ideal for incorporating metolachlor into the soil, and the lower intensity and total amount of precipitation in the fall reduces the chances of surface runoff loss. Application must be after October 15, when the soil has cooled and the microbial activity that breaks down the herbicide has slowed; however, the herbicide must be applied before the soil freezes for the season. The objectives of this study were to determine relative runoff losses of fall- and spring-applied metolachlor with water and sediment, and to monitor with time the relative amounts and location of fall- and spring-applied metolachlor in the top 35 cm of soil profile

Contributing Area and Concentration Effects on Herbicide Removal by Vegetative Buffer Strips

Deteriorated water quality due to nonpoint source pollution from herbicides is one of the environmental problems receiving attention this decade. One off-site best management practice (BMP) being suggested to improve water quality is vegetative buffer strips. This study was conducted on a Storden loam soil, under simulated rainfall (6.35 cm/h), to determine the effects of nominal inflow concentration (0.1 and 1.0 mg/L) and the ratio of drainage area to vegetated buffer strip area (simulated to be 15:1 and 30:1) on the efficiency of vegetative buffer strips (12.2 m long) in removing herbicides dissolved in runoff water. Four treatments (2 ¥ 2 factorial) replicated three times were included in the study. Three inflow samples (each integrated over 15 min) and nine outflow samples (each integrated over 5 min) were collected from each plot and analyzed for three herbicides. Reductions of 41, 39, and 38% from plots having a relative area ratio of 15:1, and 37, 35, and 34% from plots having a relative area ratio of 30:1 were measured, respectively, for atrazine, metolachlor, and cyanazine. Although the percentage of removal decreased for the larger area ratios for each herbicide, the decreases were not significant. Reductions of 29, 30, and 28% from plots having 0.1 mg/L nominal inflow concentration, and 49, 44, and 45% from plots having 1.0 mg/L nominal inflow concentration were measured, respectively, for atrazine, metolachlor, and cyanazine. The differences between reductions for the nominal inflow concentrations were significant. Using a bromide tracer, it was determined that the major factor in reduction of herbicide transport was infiltration of inflow into the vegetative buffer strips.This article is from Transactions of the ASAE, 39, no. 6 (1996): 2105–2111. Journal Paper No. J-16319 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2934. The mention of firm names or trade products does not imply that they are endorsed or recommended by Iowa State University over other firms or similar products not mentioned.</p