Kaixuan Bu

Effects of glyphosate on the mineral content of glyphosate-resistant soybeans (Glycine max).

There are conflicting claims as to whether treatment with glyphosate adversely affects mineral nutrition of glyphosate-resistant (GR) crops. Those who have made claims of adverse effects have argued links between reduced Mn and diseases in these crops. This article describes experiments designed to determine the effects of a recommended rate (0.86 kg ha(-1)) of glyphosate applied once or twice on the mineral content of young and mature leaves, as well as in seeds produced by GR soybeans (Glycine max) in both the greenhouse and field using inductively coupled plasma mass spectrometry (ICP-MS). In the greenhouse, there were no effects of either one application (at 3 weeks after planting, WAP) or two applications (at 3 and 6 WAP) of glyphosate on Ca, Mg, Mn, Zn, Fe, Cu, Sr, Ba, Al, Cd, Cr, Co, or Ni content of young or old leaves sampled at 6, 9, and 12 WAP and in harvested seed. Se concentrations were too low for accurate detection in leaves, but there was also no effect of glyphosate applications on Se in the seeds. In the field study, there were no effects of two applications (at 3 and 6 WAP) of glyphosate on Ca, Mg, Mn, Zn, Fe, Cu, Sr, Ba, Al, Cd, Cr, Co, or Ni content of young or old leaves at either 9 or 12 WAP. There was also no effect on Se in the seeds. There was no difference in yield between control and glyphosate-treated GR soybeans in the field. The results indicate that glyphosate does not influence mineral nutrition of GR soybean at recommended rates for weed management in the field. Furthermore, the field studies confirm the results of greenhouse studies.

Determination of elements in situ in green leaves by laser ablation ICP-MS using pressed reference materials for calibration

Laser ablation (LA) was used with double focusing sector field inductively coupled plasma mass spectrometry (ICP-MS) for direct elemental analysis of green leaves from seven species of desert plants. Pressed leaf standards (n = 7) were used as matrix matched standards for calibration and quality assurance. Nine elements (Mg, Ca, Mn, Cu, Sr, Cd, Ba, Hg and Pb) were determined in low mass resolution (m/Δm ≈ 400). Data was collected for three ablation line scans starting from near the stem to the tip of the leaf. The 213 nm laser ablation system was operated at the full energy setting (100%), with a repetition rate of 20 Hz, a spot size of 100 μm, and a scan rate of 50 μm min−1. Pressed cellulose was used for estimating detection limits, which were found to vary between 0.04 and 26 μg g−1 for Pb and Ca, respectively. Results suggest that the calibration approach is feasible for some elements (Mg, Ca, Mn, Cu, Sr, Cd, Ba) but problematic for others (Pb, Hg). Although somewhat element dependent, desert willow, autumn sage and brittle bush tended to have the highest concentrations of the elements monitored. Overall, LA-ICP-MS is a useful method for quantifying (in situ) the distribution of many elements in plant leaves.

Gill Histopathologies Following Exposure to Nanosilver or Silver Nitrate

Fish gill is the site for many crucial physiological functions. It is among the first sites of xenobiotic exposure, and gill histopathological alterations may be detected soon after toxicant exposure. Silver (Ag) is one of the most toxic metals to aquatic organisms mainly due to its ability to disrupt ionic regulation. The goal of this study was to determine the effect of ionic and nanoscale Ag on fathead minnow gills by examining gill histology and Na+/K+-ATPase immunoreactivity. Fathead minnows were exposed to two measured concentrations of silver nitrate (AgNO3: 1.3 or 3.7 μg/L as Ag+), citrate silver nanoparticles (citrate-AgNP: 15 or 39 μg/L), and polyvinylpyrrolidone-AgNP (PVP-AgNP) (AgNP: 11 or 50 μg/L). Circulatory disturbances were the most prevalent gill alterations detected and were significantly increased in all Ag treatment groups compared to control. AgNO3 (1.3 μg/L) was the only treatment that significantly elevated the number of total mucous goblet cells present. In all other Ag treatments, the percent of degenerated goblet cells was significantly increased compared to control. When the sum of all histopathological abnormalities (weighted index) was calculated, all Ag groups displayed a significantly higher index, with citrate-AgNP having the highest toxicity (index of 10 ± 0.32 versus 2.4 ± 0.6 in controls). Gill Na+/K+-ATPase immunoreactivity was decreased by Ag. These results indicated that both AgNO3 and AgNP created similar disruptions in gill structure and ionic regulation, possibly due to the ionic Ag portion of each treatment.

Elemental fingerprinting of soils using ICP-MS and multivariate statistics: A study for and by forensic chemistry majors

Students in an instrumental analysis course with a forensic emphasis were presented with a mock scenario in which soil was collected from a murder suspects car mat, from the crime scene, from adjacent areas, and from more distant locations. Students were then asked to conduct a comparative analysis using the soils elemental distribution fingerprints. The soil was collected from Lafayette County, Mississippi, USA and categorized as sandy loam. Eight student groups determined twenty-two elements (Li, Be, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Cs, Ba, Pb, U) in seven samples of soil and one sample of sediment by microwave-assisted acid digestion and inductively coupled plasma-mass spectrometry (ICP-MS). Data were combined and evaluated using multivariate statistical analyses. All eight student groups correctly classified their unknown among the different locations. Students learn, however, that whereas their results suggest that the elemental fingerprinting approach can be used to distinguish soils from different land-use areas and geographic locations, applying the methodology in forensic investigations is more complicated and has potential pitfalls. Overall, the inquiry-based pedagogy enthused the students and provided learning opportunities in analytical chemistry, including sample preparation, ICP-MS, figures-of-merit, and multivariate statistics.

Identification of silver nanoparticles in Pimephales promelas gastrointestinal tract and gill tissues using flow field flow fractionation ICP-MS

The environmental toxicity of silver nanoparticles (AgNPs) is of increasing concern due to their intensified production, use and subsequent environmental release. To further understand nanoparticle toxicity, more knowledge is needed about the particle fate upon uptake. AgNPs were identified in both the GI tract and gill of fathead minnows using field-flow-fractionation interfaced to inductively coupled plasma mass spectrometry (FFF-ICP-MS).