The lake-forming reactions of the oxidised and reduced forms of the logwood and brazilwood colouring matters with the more important mordanting metals have been investigated. The oxidised forms appear t o be the lake-forming species, the o-hydroxyquinone system of the molecule chelating with the mordanting metal atom; the leuco forma must first be oxidised by air or the mordanting salt before lake formation can take place. When a chromate or a dichromate is used tw mordant, this is first reduced to the chromic cation, at the expense of the total destruction of some of the colouring matter, before lake formation occurs.The logwood oplouring matter, when treated with a chromium salt in solution or on the fibre, forms a deep blue 2 : 1 (dye : metal) complex, which is preceded by a transient purple 1 : 1 complex. Aluminium, cobalt, and (ferric) iron also form 2 : 1 complexes, and copper appears to form E 1 : 1 complex.
Extensive in-stream studies were conducted to determine a scientifically defensible site-specific water quality standard for ammonia for Salt Creek which is a naturally saline waterbody on southeastern Nebraska. One component of the program was to design and conduct an in situ toxicity testing program to calculate 30-day IC20 values for fathead minnows and channel catfish, and use those data in combination with the other studies to determine a weight-of-evidence-based site-specific water quality criterion. The in situ toxicity tests used caged fish continuously exposed for 30-days at nine in-stream locations to more accurately characterize the complex interactions of ammonia in Salt Creek waters. Two fish species were selected for this program: fathead minnows (Pimephales promelas) and channel catfish (Ictalurus punctatus). The selection of exposure chamber locations was based on in-stream concentrations of total ammonia, and natural concentrations of salinity. The experimental design evaluated two toxicological endpoints: mortality and growth; which were combined into a "biomass" determination. The 30-day IC20 value for the channel catfish was calculated to be 3.85 mg N/L based on total biomass. The 30-day IC20 value for the fathead minnow was >9.98 mg N/L, because there was less than a 20 percent decrease in biomass at downstream stations versus the control at the highest 30-day average instream exposure concentration biomass. These in situ IC20 values were then used with the other site-specific assessments using a weight of evidence approach to a determine a numeric sitespecific water quality standard which will be fully protective of Salt Creek. These other sitespecific criterion components included: 5 years of winter and summer bioassessment data, whole effluent toxicity testing, and extensive ammonia modeling. The results of all of these components were integrated and used to determine seasonal (summer and winter) site-specific total ammonia water quality standards for Salt Creek. The in-situ testing component proved to be a very labor intensive but useful tool when evaluating the effects of ammonia in Salt Creek.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.