Perchlorate

In the current study, an analytical technique has been optimized for the analysis of disinfection by-products (perchlorate (ClO4
), bromate (BrO3
), nitrate (NO3
), nitrite and sulfite (SO32–) in drinking water obtained from spring, well and tap water (desalinated) sources. Methods: The ultra-performance liquid chromatography electrospray ionization mass spectrometry (UPLC ESI/MS) conditions have been optimized for oxyhalides ClO4
(isotopes, 37ClO4
and 35ClO4
) andBrO3
(isotopes, 81BrO3
and 79BrO3
), and inorganic anions NO3
, NO2
and SO32–. Separation was achieved by BEH C18 column with methanol (75%) and water (24.99%, HCOOH 0.01%) mobile phase at flow rate 0.2 mL/min.

Determining whether liquid water exists on the Martian surface is central to understanding the hydrologic cycle and potential for extant life on Mars. Recurring slope lineae, narrow streaks of low reflectance compared to the surrounding terrain, appear and grow incrementally in the downslope direction during warm seasons when temperatures reach about 250–300 K, a pattern consistent with the transient flow of a volatile species. Brine flows (or seeps) have been proposed to explain the formation of recurring slope lineae, yet no direct evidence for either liquid water or hydrated salts has been found. Here we analyse spectral data from the Compact Reconnaissance Imaging Spectrometer for Mars instrument onboard the Mars Reconnaissance Orbiter from four different locations where recurring slope lineae are present. We find evidence for hydrated salts at all four locations in the seasons when recurring slope lineae are most extensive, which suggests that the source of hydration is recurring slope lineae activity. The hydrated salts most consistent with the spectral absorption features we detect are magnesium perchlorate, magnesium chlorate and sodium perchlorate. Our findings strongly support the hypothesis that recurring slope lineae form as a result of contemporary water activity on Mars.

The WCL (Wet Chemistry Lab) instrument on board the Phoenix Lander identified the soluble ionic composition of the soil at the landing site. However, few studies have been conducted to understand the parent salts of these soluble ions. Here we studied the possible salt assemblages at the Phoenix landing site using two different thermodynamic models: FREZCHEM and Geochemist’s Workbench (GWB). Two precipitation pathways were used: evaporation (T>0°C using both FREZCHEM and GWB) and freezing (T<0°C using only FREZCHEM). Through applying three different models of initial ionic concentrations (from sulfate to chlorate/perchlorate dominated), we calculated the resulting precipitated minerals. The results—through both freezing and evaporation—showed some common minerals that precipitated regardless of the ionic initial concentration. These ubiquitous minerals are magnesium chlorate hexahydrate Mg(ClO3)2·6H2O, potassium perchlorate (KClO4) and gypsum (CaSO4·2H2O). Other minerals evidence specific precipitation pathway. Precipitation of highly hydrated salts such as meridianiite (MgSO4·11H2O) and MgCl2·12H2O indicate freezing pathway, while precipitation of the low hydrated salts(anhydrite, kieserite and epsomite) indicate evaporation. The present hydration states of the precipitated hydrated minerals probably reflect the ongoing thermal processing and recent seasonally varying humidity conditions at the landing site, but these hydration states might not reflect the original depositional conditions. The simulations also showed the absence of Ca-perchlorate in all models, mainly because of the formation of two main salts: KClO4 and gypsum which are major sinks for ClO4- and Ca2+ respectively. Finally, in consideration to the Martian life, it might survive at the very low temperatures and low water activities of the liquids formed. However, besides the big and widely recognized challenges to life posed by those extreme environmental parameters (especially low water activity), another main challenge for any form of life in such an environment is to maintain contact with the small droplets of the stable liquids in the regolith and to interact with life in other isolated droplets.

Chlorate (ClO3−) is an intermediate oxidation species between chloride (Cl−) and perchlorate (ClO4−), both of which were found at the Phoenix landing site by the Wet Chemistry Lab (WCL). The chlorate ion is almost as stable as perchlorate, and appears to be associated with perchlorate in most terrestrial reservoirs (e.g. Atacama and Antarctica). It is possible that chlorate contributed to the ion sensor response on the WCL, yet was masked by the strong perchlorate signal. However, very little is known about chlorate salts and their effect on the stability of water. We performed evaporation rate experiments in our Mars simulation chamber, which enabled us to determine the activity of water for various concentrations. From this we constructed solubility diagrams for NaClO3, KClO3, Mg(ClO3)2 and Ca(ClO3)2, and determined the Pitzer parameters for each salt. Chlorate salt eutectic temperatures range from 270 K (KClO3) to 204 K (Mg(ClO3)2). Modeling the addition of chlorate to the initial WCL solutions shows that it precipitates in concentrations comparable to other common salts, such as gypsum and epsomite, and implies that chlorates may play an important role in the wet chemistry on Mars.

Abstract: There has recently been great interest in the valorization of biomass waste in the context of the biorefinery. The biopolymer chitosan, derived from chitin, is present in large quantities of crustacean waste. This biomass can be converted into value-added products with applications in energy, fuel, chemicals and materials manufacturing. The many reported applications of this polymer can be attributed to its unique properties, such as biocompatibility, chemical versatility, biodegradability and low toxicity. Cost effective water filters which decontaminate water by removal of specific impurities and microbes are in great demand. To address this need, the development of ion exchange resins using environmentally friendly, renewable materials such as biopolymers as solid supports was evaluated. The identification and remediation of perchlorate contaminated water using an easy, inexpensive method has come under the spotlight recently. Similarly, the use of a low cost perchlorat...

Perchlorate has been known to be present in salt deposits from the Atacama Desert for over a century. Its presence is typically associated with NO3-, although relatively few samples from the Atacama have been evaluated. Perchlorate in the Atacama nitrate deposits has a substantial Delta17O anomaly strongly suggesting an atmospheric origin, or at least a production mechanism involving O3 (e.g. surface oxidation). Reports of natural ClO4- in North America have been increasing recently. These reports indicate that ClO4- is widely distributed in groundwater and in unsaturated surface soils. However, most reported occurrences have been at low concentrations. Because of the association of ClO4- with NO3- in the Atacama deposits, previously identified NO3- deposits with atmospheric components in North America were investigated for the occurrence of ClO4-. These nitrate deposits are located in the Death Valley region of the Mojave Dessert and have been previously characterized with respect ...

Activated carbon was tailored with both iron and quaternary ammonium surfactants so as to concurrently remove both arsenate and perchlorate from groundwater. The iron (hydr)oxide preferentially removed the arsenate oxyanion but not perchlorate; while the quaternary ammonium preferentially removed the perchlorate oxyanion, but not the arsenate. The co-sorption of two anionic oxyanions via distinct mechanisms has yielded intriguing phenomena. Rapid small-scale column tests (RSSCTs) with these dually prepared media employed synthetic waters that were concurrently spiked with arsenate and perchlorate; and these trial results showed that the quaternary ammonium surfactants enhanced arsenate removal bed life by 25-50% when compared to activated carbon media that had been preloaded merely with iron (hydr)oxide; and the surfactant also enhanced the diffusion rate of arsenate per the Donnan effect. The authors also employed natural groundwater from Rutland, MA which contained 60 μg/L As and traces of silica, and sulfate; and the authors spiked this with 40 μg/L perchlorate. When processing this water, activated carbon that had been tailored with iron and cationic surfactant could treat 12,500 bed volumes before 10 μg/L arsenic breakthrough, and 4500 bed volumes before 6 μg/L perchlorate breakthrough. Although the quaternary ammonium surfactants exhibited only a slight capacity for removing arsenate, these surfactants did facilitate a more favorably positively charged avenue for the arsenate to diffuse through the media to the iron sorption site (i.e. via the Donnan effect). © 2009.

http://www.ncbi.nlm.nih.gov/pubmed/19476961 
http://www.sciencedirect.com/science/article/pii/S0043135409002668

Sources of drinking water have been contaminated by military-related activity for decades, but such environmental pollution has not been recognized as a security threat in its own right. The case of perchlorate in the United States demonstrates the reflexive nature of environmental security risks, as well as the inconsistent burdens of proof required for responses to uncertain threats. A known endocrine disruptor, perchlorate blocks the uptake of iodide in the thyroid, and poses a differential risk to women, children, and other at-risk groups. Despite a conclusion by the National Research Council that known studies of perchlorate indicate no harm at low levels of ingestion (translated roughly to 27 parts per billion in water), newer research indicates a measure of concern for some tens of millions of residents in the southwestern US. This research examines the decision-making process that translated risk assessment studies to regulatory levels, including how endocrine disrupting chemicals pose a methodological dilemma for chemical risk assessment policy.