Chlorine radicals, including Cl• and Cl2 •–, can be produced in sunlight waters (rivers, oceans, and lakes) or water treatment processes (e.g., electrochemical and advanced oxidation processes). Dissolved organic matter (DOM) is a major reactant with, or a scavenger of, Cl• and Cl2 •– in water, but limited quantitative information exists regarding the influence of DOM structure on its reactivity with Cl• and Cl2 •–. This study aimed at quantifying the reaction rates and the formation of chlorinated organic byproducts produced from Cl• and Cl2 •– reactions with DOM. Laser flash photolysis experiments were conducted to quantify the second-order reaction rate constants of 19 DOM isolates with Cl• (k DOM–Cl•) and Cl2 •– (k DOM–Cl2•–), and compare those with the hydroxyl radical rate constants (k DOM–•OH). The values for k DOM–Cl• ((3.71 ± 0.34) × 108 to (1.52 ± 1.56) × 109 MC –1 s–1) were orders of magnitude greater than the k DOM–Cl2•– values ((4.60 ± 0.90) × 106 to (3.57 ± 0.53) × 107 MC –1 s–1). k DOM–Cl• negatively correlated with the weight-averaged molecular weight (M W) due to the diffusion-controlled reactions. DOM with high aromaticity and total antioxidant capacity tended to react faster with Cl2 •–. During the same experiments, we also monitored the formation of chlorinated byproducts through the evolution of total organic chlorine (TOCl) as a function of chlorine radical oxidant exposure (CT value). Maximum TOCl occurred at a CT of 4–8 × 10–12 M·s for Cl• and 1.1–2.2 × 10–10 M·s for Cl2 •–. These results signify the importance of DOM in scavenging chlorine radicals and the potential risks of producing chlorinated byproducts of unknown toxicity.

Bromine radicals can pose great impacts on the photochemical transformation of trace organic contaminants in natural and engineered waters. However, the reaction kinetics and mechanisms involved are barely known. In this work, second-order reaction rate constants with Br• and Br2 •– were determined for 70 common trace organic contaminants and for 17 model compounds using laser flash photolysis and steady-state competition kinetics. The k Br• values ranged from <108 to (2.86 ± 0.31) × 1010 M–1 s–1 and the k Br2 •– values from <105 to (1.18 ± 0.09) × 109 M–1 s–1 at pH 7.0. Six quantitative structure–activity relationships were developed, which allow predicting additional unknown k Br• and k Br2 •– values. Single-electron transfer was shown to be a favored pathway for the reactions of Br• and Br2 •– with trace organic contaminants, and this was supported by transient spectroscopy and quantum chemical calculations. This study is essential in advancing the scientific understanding of halogen radical-involved chemistry in contaminant transformation.

a b s t r a c tRisky decision making is a complex process that involves weighing the probabilities of alternative options that can be desirable, undesirable, or neutral. Individuals vary greatly in how they make decisions either under ambiguity and/or under risk. Such individual differences may have genetic bases. Based on previous studies on the genetic basis of decision making, two decision making tasks [i.e., the Iowa Gambling Task (IGT) and Loss Aversion Task (LAT)] were used to test the effect of 5-HTTLPR polymorphism on decision making under ambiguity and under risk in a large Han Chinese sample (572 college students, 312 females). Basic intelligence and memory tests were also included to control for the influence of basic cognitive abilities on decision making. We found that 5-HTTLPR polymorphism significantly influenced performance in both IGT and LAT. After controlling for intelligence and memory abilities, subjects homozygous for s allele had lower IGT scores than l carriers in the first 40 trials of the IGT task. They also exhibited higher loss aversion than l carriers in the LAT task. Moreover, the effects of 5-HTTLPR were stronger for males than for females. These results extend the literature on the important role of emotion in decision making under ambiguity and risk, and shed additional lights on how decision making is influenced by culture as well as sex differences. Combining our results with existing literature, we propose that these effects might be mediated by a neural circuitry that comprises the amygdala, ventromedial prefrontal cortex, and insular cortex. Understanding the genetic factors affecting decision making in healthy subjects may allow us to better identify at-risk individuals, and better target the development of new potential treatments for specific disorders such as schizophrenia, addiction, and depression.

Advanced oxidation processes (AOPs) can degrade a wide range of trace organic contaminants (TrOCs) to improve the quality of potable water or discharged wastewater effluents. Their effectiveness is impacted, however, by the dissolved organic matter (DOM) that is ubiquitous in all water sources. During the application of an AOP, DOM can scavenge radicals and/or block light penetration, therefore impacting their effectiveness toward contaminant transformation. The multiple ways in which different types or sources of DOM can impact oxidative water purification processes are critically reviewed. DOM can inhibit the degradation of TrOCs, but it can also enhance the formation and reactivity of useful radicals for contaminants elimination and alter the transformation pathways of contaminants. An indepth analysis highlights the inhibitory effect of DOM on the degradation efficiency of TrOCs based on DOM's structure and optical properties and its reactivity toward oxidants as well as the synergistic contribution of DOM to the transformation of TrOCs from the analysis of DOM's redox properties and DOM's transient intermediates. AOPs can alter DOM structure properties as well as and influence types, mechanisms, and extent of oxidation byproducts formation. Research needs are proposed to advance practical understanding of how DOM can be exploited to improve oxidative water purification.

Dissolved organic matter (DOM) is a major scavenger of bromine radicals (e.g., Br• and Br2 •–) in sunlit surface waters and during oxidative processes used in water treatment. However, the literature lacks quantitative measurements of reaction rate constants between bromine radicals and DOM and lacks information on the extent to which these reactions form brominated organic byproducts. Based on transient kinetic analysis with different fractions and sources of DOM, we determined reaction rate constants for DOM with Br• ranging from <5.0 × 107 to (4.2 ± 1.3) × 108 MC –1 s–1, which are comparable with those of HO• but higher than those with Br2 •– (k = (9.0 ± 2.0) × 104 to (12.4 ± 2.1) × 105 MC –1 s–1). Br• and Br2 •– attack the aromatic and antioxidant moieties of DOM via the electron transfer mechanism, resulting in Br– release with minimal substitution of bromine into DOM. For example, the total organic bromine was less than 0.25 μM (as Br) at environmentally relevant bromine radicals’ exposures of ∼10–9 M·s. The results give robust evidence that the scavenging of bromine radicals by DOM is a crucial step to prevent inorganic bromine radical chemistry from producing free bromine (HOBr/OBr–) and subsequent brominated byproducts.

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Catechol-O-methyltransferase(COMT) Val158Met (rs4680) polymorphism plays a crucial role in regulating brain dopamine level. Converging evidence from Caucasian samples showed that, compared with rs4680 Val allele, the Met allele was linked to lower COMT activity, which in turn was linked to better cognitive performance such as working memory (WM) and to a larger hippocampus (a brain region important for WM). However, some behavioral studies have shown that the function of rs4680 appears to vary across different ethnic groups, with Chinese subjects showing an opposite pattern as that for Caucasians (i.e. the Val allele is linked to better cognitive functions related to WM in Chinese). Using a sample of healthy Han Chinese college students (ages from 19 to 21 years), this study investigated the association of COMT Val158Met genotype with behavioral data on a two-back WM task (n = 443, 189M/254F) and T1 MRI data (n = 320, 134M/186F). Results showed that, compared to the Met allele, the Val allele was associated with larger hippocampal volume (the right hippocampus: β = −0.118, t = −2.367, P = 0.019, and the left hippocampus: β = −0.099, t = −1.949, P = 0.052) and better WM performance (β = −0.110, t = −2.315, P = 0.021). These results add to the growing literature on differentiated effects of COMT rs4680 polymorphism on WM across populations and offer a brain structural mechanism for such population-specific genetic effects.

Advanced oxidation processes (AOPs) are increasingly applied in water and wastewater treatment. Understanding the role of reactive species using probes and quenchers is one of the main requirements for good process design. However, much fundamental kinetic data for the reactions of probes and quenchers with reactive species is lacking, probably leading to inappropriate probe and quencher selection and dosing. In this work, secondorder rate constants for over 150 reactions of probes and quenchers with reactive species such as • OH, SO 4•− , and Cl • and chemical oxidants such as free chlorine and persulfate were determined. Some previously ill-quantified reactions (e.g., furfuryl alcohol and methyl phenyl sulfoxide reactions with certain chemical oxidants, nitrobenzene and 1,4-dioxane reactions with certain halogen radicals) were found to be kinetically favorable. The selection of specific probes can be guided by the improved kinetic database. The criteria for properly choosing dosages of probes and quenchers were proposed along with a procedure for quantifying reactive species free of interference from probe addition. The limitations of probe and quencher approaches were explicated, and possible solutions (e.g., the combination with other tools) were proposed. Overall, the kinetic database and protocols provided in this work benefit future research in understanding the radical chemistry in AOPs as well as other radical-involved processes.