Bone need not remain an elephant in the room for radiocarbon dating

Radiocarbon ( 14 C) analysis of skeletal remains by accelerator mass spectrometry is an essential tool in multiple branches of science. However, bone 14 C dating results can be inconsistent and not comparable due to disparate laboratory pretreatment protocols that remove contamination. And, pretreatments are rarely discussed or reported by end-users, making it an ‘elephant in the room’ for Quaternary scientists. Through a questionnaire survey, I quantified consensus on the reliability of collagen pretreatments for 14 C dating across 132 experts (25 countries). I discovered that while more than 95% of the audience was wary of contamination and would avoid gelatinization alone (minimum pretreatment used by most 14 C facilities), 52% asked laboratories to choose the pretreatment method for them, and 58% could not rank the reliability of at least one pretreatment. Ultrafiltration was highly popular, and purification by XAD resins seemed restricted to American researchers. Isolating and dating the amino acid hydroxyproline was perceived as the most reliable pretreatment, but is expensive, time-consuming and not widely available. Solid evidence supports that only molecular-level dating accommodates all known bone contaminants and guarantees complete removal of humic and fulvic acids and conservation substances, with three key areas of progress: (i) innovation and more funded research is required to develop affordable analytical chemistry that can handle low-mass samples of collagen amino acids, (ii) a certification agency overseeing dating-quality control is needed to enhance methodological reproducibility and dating accuracy among laboratories, and (iii) more cross-disciplinary work with better 14 C reporting etiquette will promote the integration of 14 C dating across disciplines. Those developments could conclude long-standing debates based on low-accuracy data used to build chronologies for animal domestications, human/megafauna extirpations and migrations, archaeology, palaeoecology, palaeontology and palaeoclimate models.

Effects of treatment on the characterization of organic matter in wastewater: a review on size distribution and structural fractionation

Since it is difficult to analyze the components of organic matter in complex effluent matrices individually, the use of more collective, but at the same time, specific wastewater characterization methods would be more appropriate to evaluate changes in effluent characteristics during wastewater treatment. For this purpose, size distribution and structural (resin) fractionation tools have recently been proposed to categorize wastewater. There are several case studies available in the scientific literature being devoted to the application of these fractionation methods. This paper aimed to review the most relevant studies dealing with the evaluation of changes in wastewater characteristics using size distribution and structural (resin) fractionation tools. According to these studies, sequential filtration-ultrafiltration procedures, as well as XAD resins, are frequently employed for size and structural fractionations, respectively. This review focuses on the most relevant publications including biological treatment processes, as well as chemical treatment methods such as coagulation-flocculation, electrocoagulation, the Fenton's reagent and ozonation. This study aims at providing an insight into the possible treatment mechanisms and details the understanding what structural features of wastewater components enabled or prevented efficient treatment (removal) or targeted pollutants.

The formation kinetics of haloacetonitriles and halonitromethanes during chloramination

This study investigates the formation of 14N- and 15N-nitrogenous disinfection by-product formation upon 15N-chloramination from four dissolved organic matters (DOMs). A series of XAD resins were used to fractionate DOM based on their hydrophobicity and functional group. The results show that hydrophobic acid (HPOA) fraction was the most important precursor pool for haloacetonitrile (HAN); these precursors mainly generated HAN through chloramine incorporation. HPOA and hydrophobic neutral (HPON) gave higher trichloronitromethane (TCNM) yields than the other fractions did. The nitrogen origin upon chloramination of HPOA was primarily from dissolved organic nitrogen (DON). By contrast, chloramines provided the main nitrogen sources during chloraminating HPON and HPOA with low DON to dissolved organic carbon ratios. The results of formation kinetics show that dichloroacetonitrile (DCAN) of which nitrogen source originate from DON formed faster than that of which nitrogen source originate from chloramines. Under normal chloramine exposure (4,000 mg-min/L, equal to 2 mg/L chloramines with around 2 days' reaction duration), 14N-DCAN concentration was two to over five times higher than that of 15N-DCAN. This study also uses a model to calculate the formation concentration of nitrogenous disinfection by-products without hydrolysis effects. The results show that 15N-DCAN formation was linearly correlated with chloramine exposure.

Further studies on the adsorption of plant phenols by synthetic polymers

Pyrocatechol, catechol, caffeic acid, chlorogenic acid, safflor yellow A, safflor yellow B, precarthamin and carthamin were effectively adsorbed by insoluble polyvinyl-N-pyr­rolidone (PVP) in a neutral buffer solution. These eight phenols also bound with Amberlite XAD resins, however, the rate was found to be far less efficient than that of PVP. The average rate of the phenol binding was calculated as following order (%): PVP (42.7), Amberlite XAD-2 (16.6), Amberlite XAD-4 (10.1), Amberlite XAD-7 (13.0), Amberlite XAD-8 (17.7). No 3,4-dihydroxyphenylalanine was adsorbed by PVP, while the O-dihydroxylic acid could be removed by Amberlite XAD-4, XAD-7 and XAD-8. Data from using different weights of the test polymers showed that the rate of the phenol adsorption rose in proportion to each increasing amount of the adsorbents. PVP also admittedly maintained its predominent capacity for phenol binding over that of each member of the Amberlite resins.

Comparison of extracts and toxicities of organic compounds in drinking water concentrated by single and composite XAD resins

We compared extracts and toxicities of organic compounds (OCs) in drinking water concentrated by composite XAD-2/8 resin (mixed with an equal volume of XAD-2 and XAD-8 resins) with those extracted by single XAD-2 (non-polar) and XAD-8 (polar) resins. Drinking water was processed from raw water of the Han River and the Yangtze River in Wuhan section, China. The extraction efficiency of all resins was controlled at 30%. The types of extracted OCs were detected by gas chromatography–mass spectrometry, and the cytotoxicity and genotoxicity were assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and comet assays, respectively, in human hepatoma HepG2 cells. Our results showed that XAD-2/8 extracted a larger variety of OCs, compared with XAD-8 and XAD-2. The cytotoxicity and genotoxicity of extracted OCs were in the order of XAD-8> XAD-2/8> XAD-2 at almost all tested concentrations after 24 h treatment (P < 0.05). Our findings suggest that single XAD resin selectively extracts either polar or non-polar OCs, which would lead to over- or under-estimation of the toxicity of drinking water. Nevertheless, composite resin extracts both polar and non-polar OCs, and could be utilized as a useful extraction technique to evaluate the level and toxicity of OCs in drinking water.