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Aqueous phase diffusion-related isotope fractionation (DRIF) was investigated through modelling to determine under what subsurface conditions carbon isotope DRIF effects would be observable using typical sampling approaches. A dispersive enrichment factor was defined based on heavy and light isotopologue dispersion coefficients. For a given ratio of source concentration (C 0 ) to method detection limit (MDL), the maximum DRIF in a system increased linearly with transverse dispersive enrichment factor. Using this linear relationship, the critical dispersion enrichment factor for which DRIF would not be observable was quantified. Dispersive enrichment factors for various contaminants (benzene, toluene, chlorinated compounds) were estimated using field scale transverse dispersion coefficients upscaled from compound specific or non-compound specific local scale dispersivity. All predicted dispersive enrichment factors with non-compound specific dispersivity are smaller than critical values even for high C 0 /MDL ratios (e.g. 25,000), indicating DRIF would generally not be observable in systems where soil dispersivity is non-compound specific. To date, this finding has not been clearly articulated in the DRIF literature. While the calculated dispersive enrichment factors for some compounds with compound specific transverse dispersivity exceeded the critical values at which DRIF might become significant, the zones in which DRIF could potentially be observable were limited to bands below 0.5 m wide on lateral plume edges. In aquifer-aquitard systems, DRIF was theoretically detectable only in thin aquifers (e.g. 0.5 m) bounded by thick (e.g. meters) aquitards. DRIF due to back diffusion from aquitards would not be observable regardless of aquifer thickness. Simulations addressing the mixing effect in wells demonstrated that DRIF effects would be difficult to identify in the field without a sampling strategy (including smaller than industry norm well screen lengths, and fine sampling scales) expressly targeted towards that goal. The results of this study help identify what the required characteristics of such a field strategy might be. [ABSTRACT FROM AUTHOR]

Desert mosses are components of biological soil crusts (BSCs) and their ecological functions make assessment and protection of these mosses a high-ranking management priority in desert regions. Drying is thought to be useful for desert mosses surviving heat shock. In this study, we investigated the role of drying by monitoring the responses of physiological characters and asexual reproduction in the typical desert moss Syntrichia caninervis. Heat significantly decreased chlorophyll content and weakened rapid recovery of photochemical activity, and increased carotenoid content and membrane permeability. Lethal temperatures significantly destroyed shoot regeneration potential. In comparison with heat alone, drying significantly increased protonema emergence time and depressed protonema emergence area. Drying combined with heat accelerated water loss, followed by a decrease of photosynthetic activity. Drying had different influences on membrane permeability at different temperatures. When moss leaves were subjected to a combined stress of drying and heat shock, photosynthesis was maintained mainly due to the effects of drying on physiological activity although the cellular morphological integrity was affected. Drying caused opposing effects on moss physiological and reproductive characteristics. On the one hand, drying caused a positive synergistic effect with heat shock when the temperature was below 40 °C. On the other hand, drying showed antagonism with heat shock when the moss was subjected to temperatures higher than 40 °C. These findings may help in understanding the survival mechanism of dessert mosses under heat shock stress which will be helpful for the artificial reconstruction of BSCs. [Copyright &y& Elsevier]

Little is known about whether exposure to pets influences the association between hypertension and environmental tobacco smoke (ETS). The current study aims to examine the interaction of pet ownership on ETS exposure and the development of hypertension in children. From 2012 to 2013, a total of 9354 children, 5 to 17 years of age, were recruited from 62 schools in seven northeastern cities. BP in children was measured and hypertension was defined as an average diastolic blood pressure (DBP) or systolic blood pressure (SBP) at or above the 95th percentile for that child's age, sex, and height. Pet ownership in three different time periods (in utero , past 2 years, and currently) and ETS exposure data were collected from parents via a questionnaire. Two-level regressions were used for the data analyses. The data show consistent, significant interactions between exposure to pets and effects from ETS. Children who were not exposed to pets experienced stronger effects from ETS on hypertension when compared to those exposed to pets, and the protective effect of pet ownership became stronger with a greater number of pets in the home. Exposure to in utero ETS was associated with hypertension [adjusted odds ratio (aOR) = 1.32, 95% confidence interval (CI): 1.13–1.54] only for those children without pet exposure in utero but not for those with pets (aOR = 0.75; 95% CI: 0.49–1.15) (p interaction < 0.05). Moreover, household dog ownership was related to significantly lower effects of current ETS on hypertension (aOR = 0.80, 95% CI: 0.61–1.05) compared with children without dogs (aOR = 1.26, 95% CI: 1.11–1.44) (p interaction = 0.001). Interaction associations between ETS and pet ownership were more robust for girls than for boys and for younger than older children. This study indicates an inverse relationship between pet ownership and ETS, potentially pointing to pet ownership as protecting against the development of hypertension in children. Unlabelled Image • Few studies reported the interactions of pet ownership with ETS exposure on human health. • A large population-based cohort study was conducted in to assess these interactions. • Pet ownership in utero and postnatally decreases the effects of ETS exposure on hypertension. • More interactions were apparent in females and younger children. • This protective effect became stronger with a greater number of pets ownership. [ABSTRACT FROM AUTHOR]

This work systematically studied the role of pre-coagulation in the performance of ultralow pressure membrane system for algae-laden water treatment. The membrane performance with/without pre-coagulation was compared in terms of membrane permeate flux, water quality and membrane fouling. Ultralow pressure membrane system can effectively reduce TOC of Microcystis aeruginosa -laden water from 5.8 to 2.1 mg/L, and pre-coagulation removed most large inorganic particles but few small organic particles. Interestingly, pre-coagulation aggravated the fouling of ultralow membrane system which is generally acknowledged method to alleviate the ultrafiltration membrane fouling. According to Extended Derjaguin-Landau-Verwey-Overbeek theory (XDLVO), the interaction energy of membrane-foulants (ΔG fm TOT = − 41.95 mJ/m2), and foulant-foulant (ΔG ff TOT = − 30.15 mJ/m2) with coagulation were higher than those without coagulation (ΔG fm TOT = − 36.54 mJ/m2) and (ΔG ff TOT = − 15.73 mJ/m2) suggesting greater adherence between membrane and foulants & foulant and foulant after coagulation, which well agreed with SEM results. Membrane fouling models were also applied to analyze the fouling mechanism of ultralow-pressure membrane filtration. Based on above analysis, the possible fouling mechanisms for membrane filtration with/without precoagulation were proposed and then confirmed by pre-filtration experiment, where large inorganic particles played important roles. Our study could be indicative for membrane fouling control of ultralow-pressure membrane filtration for the treatment of algae-laden water. Unlabelled Image • Ultralow pressure membrane system effectively treated algae-laden water • Pre-coagulation aggravated the fouling of ultralow pressure membrane system • Interaction energy of membrane-foulants and foulant-foulant increased after coagulation. • Membrane fouling mechanisms with/without coagulation were proposed and confirmed • Compact and adhesive fouling layer caused severe fouling after coagulation. [ABSTRACT FROM AUTHOR]