Bifenthrin is a pyrethroid insecticide used in urban and agricultural applications. Previous studies have shown that environmentally relevant (ng/L) concentrations of bifenthrin increased plasma concentrations of 17b-estradiol (E2) and altered the expression of dopaminergic pathway components. The dopaminergic neurons can indirectly regulate E2 biosynthesis, suggesting that bifenthrin may disrupt the hypothalamic-pituitary-gonadal (HPG) axis. Because embryos do not have a complete HPG axis, the hypothesis that bifenthrin impairs dopamine regulation was tested in embryonic and 1-mo-old juvenile zebrafish (Danio rerio) with exposure to measured concentrations of 0.34 and 3.1 mg/L bifenthrin for 96 h. Quantitative reverse transcriptase polymerase chain reaction was used to investigate transcripts of tyrosine hydroxylase (TH), dopamine receptor 1 (DR1) and 2A (DR2A), dopamine active transporter (DAT), estrogen receptor a (ERa), ERb1, ERb2, luteinizing hormone b (LHb), follicle-stimulating hormone b (FSHb), vitellogenin (VTG), cytochrome P450 cyp19a1a, and cyp19a1b. Levels of E2 were measured by enzyme-linked immunosorbent assay (ELISA). Dopamine and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) concentrations were measured by liquid chromatrography-tandem mass spectrometry (LC-MS/MS). Significant decreases in TH and DR1 transcripts and HVA levels, as well as ratios of HVA/dopamine and HVAþDOPAC/dopamine, in zebrafish embryos were observed after bifenthrin treatment. In juveniles, a significant increase in the expression of ERb1 and the DOPAC to dopamine ratio was noted. These results show a possible antiestrogenic effect of bifenthrin in embryos, and estrogenicity in juveniles, indicating life-stage-dependent toxicity in developing fish. Environ Toxicol Chem 2018;37:236-246. C 2017 SETAC
Micronucrient availability is important to crop production and can be affected by long-term application of P and organic amendments. This study was condutted to determine the effects ofthe long-term application of different sources and rates of P application on extracrable [DTPA-sorbitol (diethylenetriamine-pentaacetic acid and sorbitol] micronutrients. Soil extractable and total micronutrients (B, Cu, Fe, Mn, Mo, and Zn), pH, and organic matter content were determined from sites across Oklahoma that had received long-term applications of beet manure, swine effluent, biosolids, or commercial fertilizer. Three continuous inorganic P experiments diat had been conducted for 36 to 39 yr and three organic P experiments diat had been conducted for 11 to 12 yr were evaluated. Tlie long-term application of inorganic P had litde effect on micronutrient availability. However, long-term application of biosolids significandy {p < 0.05) increased extractable Cu, Fe, Mo, and Zn in soil, while long-term application of beef manure significandy increased all die micronutrients evaluated. Similarly, the long-term application of swine effluent significantly increased extractable B, Cu. Mo, and Zn in soil. The addition of micronutrients from organic amendments increased micronutrient availability, while long-term inorganic P application had litde effect. The result of our study indicates organic amendments make an ideal fertilizer source for areas with micronutrient deficiencies.Abbreviations: DTPA, diethylenetriamine-pentaacetic acid; EDTA, ethylenediamine-tctraacetic acid; ICP-AES, inductively coupled plasma atomic emission spectroscopy; SOM, soil organic matter; TSP, triple superphosphate.
Natural background concentrations of trace elements in soils must be determined to establish baseline levels for soil remediation and to avoid the establishment of inaccurate or unrealistic guideline levels. The objectives of this study were to establish the background total trace element concentrations including As, Cd, Cr, Cu, Mn, Mo, Ni, Se, Pb, and Zn in 28 Oklahoma benchmark soils and to determine the relationship between soil properties and natural trace element concentrations. Soil samples were analyzed for total trace elements, pH, organic C, clay content, and oxalate-extractable Al (Al^^) and Fe (Fe^^). Both multiple regression and path analysis were used to examine the relationship between total trace elements and soil properties. The background concentrations of trace elements were (mg kg"^): As (0.
The Mehlich 3 (M3) method is widely used to extract plant-available phosphorus from soil over a wide range of pH values. The method is also used by many laboratories to determine multiple plant-available nutrients simultaneously. However, except for P, this method has not been statistically validated within and among laboratories. The objective of this study was to determine the repeatability (within-laboratory performance) and reproducibility (among-laboratories performance) of the M3 method for several different nutrients by using a wide variety of soils. An in-house homogeneity test was conducted for 11 soils. Three replicates of each of the 11 soils were sent to 23 domestic and international laboratories for analyses primarily for K, Ca, Mg, Zn, Mn, Fe, and Cu. Samples were scooped, weighed, or both scooped and weighed for extraction. The various nutrients in the extracts were quantified by the participating laboratories by using inductively coupled plasmaatomic emission spectrometry. Ranges (in parentheses) of the repeatability relative standard deviation (RSDr) values for the scooped samples were K (3.886.14), Ca (2.1910.6), Mg (2.275.73), Zn (4.1142.7), Mn (3.158.53), Fe (2.327.74), and Cu (3.6511.2). For the weighed samples, the ranges (in parentheses) of the RSDr values were K (1.654.65), Ca (1.4316.9), Mg (1.379.83), Zn (2.6033.0), Mn (1.614.90), Fe (1.564.47), and Cu (2.9517.9). Ranges (in parentheses) of the reproducibility relative standard deviation (RSDR) values for the scooped samples were K (7.4420.0), Ca (7.1033.5), Mg (7.6326.4), Zn (11.648.7), Mn (10.519.7), Fe (12.422.0), and Cu (8.8645.3). Ranges (in parentheses) of the RSDR values for the weighed samples were K (3.4712.7), Ca (7.6134.6), Mg (7.5329.0), Zn (10.649.2), Mn (6.5420.7), Fe (11.021.5), and Cu (9.7343.0). The Horwitz ratios (HorRat) were also used to evaluate the repeatability, HorRatr, and the reproducibility, HorRatR. Overall, the M3 method appears to be both repeatable and reproducible across the two categories for K, Mg, Zn, Mn, and Cu, and the vast majority of the HorRat values for both repeatability and reproducibility were within the acceptable range. However, a large number of soils in both the weighed and scooped categories displayed unacceptable HorRat values for the reproducibility of Ca and Fe, indicating that the M3 is not suitable for the extraction and quantitation of Ca and Fe in soils. The results of this study indicate that the M3 method for the determination of K, Mg, Zn, Mn, and Cu in soils is both accurate and precise when standardized procedures are used. The method has been proven to be suitable for use as a reference method for testing soil materials for extractable P, K, Mg, Zn, Mn, and Cu. Further study may be needed to confirm the suitability of the M3 method for Ca and Fe.
Urban-use pesticides present a unique risk to non-target organisms in surface aquatic systems because impervious pavement facilitates runoff that may lead to serious contamination and ensuing aquatic toxicity. Fipronil is an insecticide used at high rates in urban environments, especially in regions such as California. This compound and its biologically active degradation products have been detected in urban runoff drainage and downstream surface water bodies at concentrations exceeding toxicity thresholds for sensitive aquatic invertebrates, necessitating a better understanding of the runoff sources and causes of this contamination at sites of application. In this study, we evaluated sorption of fipronil, fipronil desulfinyl, fipronil sulfide, and fipronil sulfone in urban dust, soil, and concrete, matrices commonly associated with the perimeter of a residential home. Samples were also collected from five single family homes treated with fipronil in Riverside, California, for five months to determine the occurrence of fipronil and its degradates in runoff water, urban dust, soil, and on concrete surfaces. Statistical analysis was performed to determine which urban matrices contributed more significantly to the contaminant levels in runoff water. Freundlich sorption coefficients for fipronil and its degradation products in dust were 3-to 9-fold greater than their values in soil. Fipronil and its degradates were detected in 100% of runoff samples and their presence was observed in dust, soil, and concrete wipe samples for 153 d after the treatment. Linear regression analysis showed that concrete surfaces were a primary source of all four compounds to runoff, and loose dust on concrete pavement also served as an important contributor. This study represents the first comprehensive investigation of the sources and causes for surface runoff contamination by fipronil and its degradation products. Findings highlight the
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