Surface storage (pools, pockets, and stagnant areas caused by woody debris, bars etc) is very important to solute transport in streams as it attenuates the peak of a spill but releases the solute back to the stream ov...Surface storage (pools, pockets, and stagnant areas caused by woody debris, bars etc) is very important to solute transport in streams as it attenuates the peak of a spill but releases the solute back to the stream over a long time. The latter results in long exposure time of biota. Pools as fundamental stream morphology unit are commonly found in streams with mixed bed materials in pool-riffle or pool-step sequences. Fitting the transient storage model (TSM) to stream tracer test data may be problematic when pools present. A fully hydrodynamic 2-D, depth averaged advection-dispersion solute transport numerical simulation study on hypothetical stream with pool reveals that a pool can sharply enhance longitudinal spreading, cause a lag in the plume travel-time and radically increase solute residence time in the stream. These effects fade like a “wake” as the solute plume moves downstream of the pool. Further, these effects are strongly influenced by a dimensionless number derived from the 2-D transport equation ? or , which outlines the relative transverse mixing intensity of a stream or river, where, of the stream reach concerned, W is the flow width, Q0 is the volumetric flow rate, q is the longitudinal flux density, and Dt is the transverse turbulent diffusion coefficient. The breakthrough curves (BTCs) downstream of a pool may be “heavy tailed” which cannot be modeled accurately by the TSM. The internal transport and mixing condition (including the secondary circulations) in a pool together with the pool’s dimension determine the pool’s storage effects especially when >> 1. Results also suggest that the falling limb of a BTC more accurately characterizes the pool's storage because the corresponding solute has more chance to sample the entire storage area.展开更多
Global change will lead to increases in regional precipitation and nitrogen（N） deposition in the semi-arid grasslands of northern China. We investigated the responses of vegetation carbon（C） pools to simulated pre...Global change will lead to increases in regional precipitation and nitrogen（N） deposition in the semi-arid grasslands of northern China. We investigated the responses of vegetation carbon（C） pools to simulated precipitation and N deposition increases through field experiments in a typical steppe in Inner Mongolia. The treatments included NH4NO3 addition at concentrations of 0（CK）, 5（LN, low nitrogen）, 10（middle nitrogen, MN）, and 20（HN,high nitrogen）（g m^（-2）a^（-1）） with and without water. After three consecutive years of treatment, from 2010 to 2012,water addition did not significantly change the size of the total vegetation C pools, but it significantly decreased the ratio of root：shoot（R：S）（P = 0.05） relative to controls. By contrast, N addition significantly increased the total vegetation C pools. The C pools in the LN, MN and HN treatments increased by 22, 39 and 44 %, respectively. MN produced the largest effect among the N concentrations,although differences between N-added treatments were not significant（P ？ 0.05）. N addition significantly reduced the ratio of root：shoot（R：S）（P = 0.03）. However, there were no significant interactive effects of water and N addition on the vegetation C pools.展开更多
Disinfection of water for human use is essential to protect against microbial disease;however, disinfection also leads to formation of disinfection by-products（DBPs）, some of which are of health concern. From a chem...Disinfection of water for human use is essential to protect against microbial disease;however, disinfection also leads to formation of disinfection by-products（DBPs）, some of which are of health concern. From a chemical perspective, swimming pools are a complex matrix, with continual addition of a wide range of natural and anthropogenic chemicals via filling waters, disinfectant addition, pharmaceuticals and personal care products and human body excretions. Natural organic matter, trace amounts of DBPs and chlorine or chloramines may be introduced by the filling water, which is commonly disinfected distributed drinking water. Chlorine and/or bromine is continually introduced via the addition of chemical disinfectants to the pool. Human body excretions（sweat, urine and saliva） and pharmaceuticals and personal care products（sunscreens, cosmetics, hair products and lotions） are introduced by swimmers. High addition of disinfectant leads to a high formation of DBPs from reaction of some of the chemicals with the disinfectant.Swimming pool air is also of concern as volatile DBPs partition into the air above the pool.The presence of bromine leads to the formation of a wide range of bromo-and bromo/chloro-DBPs, and Br-DBPs are more toxic than their chlorinated analogues. This is particularly important for seawater-filled pools or pools using a bromine-based disinfectant.This review summarises chemical contaminants and DBPs in swimming pool waters, as well as in the air above pools. Factors that have been found to affect DBP formation in pools are discussed. The impact of the swimming pool environment on human health is reviewed.展开更多
Theoretical and empirical studies have suggested that an underestimate of the ENSO asymmetry may be accompanied by a climatologically smaller and warmer western Pacific warm pool. In light of this suggestion, simulati...Theoretical and empirical studies have suggested that an underestimate of the ENSO asymmetry may be accompanied by a climatologically smaller and warmer western Pacific warm pool. In light of this suggestion, simulations of the tropical Pacific climate by 19 Coupled Model Intercomparison Project Phase 3 （CMIP3） climate models that do not use flux adjustment were evaluated. Our evaluation revealed systematic biases in both the mean state and ENSO statistics. The mean state in most of the models had a smaller and warmer warm pool. This common bias in the mean state was accompanied by a common bias in the simulated ENSO statistics： a significantly weak asymmetry between the two phases of ENSO. Moreover, despite the generally weak ENSO asymmetry simulated by all models, a positive correlation between the magnitude of the bias in the simulated warm-pool size and the magnitude of the bias in the simulated ENSO asymmetry was found. These findings support the suggested link between ENSO asymmetry and the tropical mean state--the climatological size and temperature of the warm pool in particular. Together with previous studies, these findings light up a path to improve the simulation of the tropical Pacific mean state by climate models： enhancing the asymmetry of ENSO in the climate models.展开更多
文摘Surface storage (pools, pockets, and stagnant areas caused by woody debris, bars etc) is very important to solute transport in streams as it attenuates the peak of a spill but releases the solute back to the stream over a long time. The latter results in long exposure time of biota. Pools as fundamental stream morphology unit are commonly found in streams with mixed bed materials in pool-riffle or pool-step sequences. Fitting the transient storage model (TSM) to stream tracer test data may be problematic when pools present. A fully hydrodynamic 2-D, depth averaged advection-dispersion solute transport numerical simulation study on hypothetical stream with pool reveals that a pool can sharply enhance longitudinal spreading, cause a lag in the plume travel-time and radically increase solute residence time in the stream. These effects fade like a “wake” as the solute plume moves downstream of the pool. Further, these effects are strongly influenced by a dimensionless number derived from the 2-D transport equation ? or , which outlines the relative transverse mixing intensity of a stream or river, where, of the stream reach concerned, W is the flow width, Q0 is the volumetric flow rate, q is the longitudinal flux density, and Dt is the transverse turbulent diffusion coefficient. The breakthrough curves (BTCs) downstream of a pool may be “heavy tailed” which cannot be modeled accurately by the TSM. The internal transport and mixing condition (including the secondary circulations) in a pool together with the pool’s dimension determine the pool’s storage effects especially when >> 1. Results also suggest that the falling limb of a BTC more accurately characterizes the pool's storage because the corresponding solute has more chance to sample the entire storage area.
基金supported by the National Natural Science Foundation of China(Nos.4137308441330528+1 种基金and41203054)the Special Fund for Agro-scientific Research in the Public Interest(No.201203012)
文摘Global change will lead to increases in regional precipitation and nitrogen（N） deposition in the semi-arid grasslands of northern China. We investigated the responses of vegetation carbon（C） pools to simulated precipitation and N deposition increases through field experiments in a typical steppe in Inner Mongolia. The treatments included NH4NO3 addition at concentrations of 0（CK）, 5（LN, low nitrogen）, 10（middle nitrogen, MN）, and 20（HN,high nitrogen）（g m^（-2）a^（-1）） with and without water. After three consecutive years of treatment, from 2010 to 2012,water addition did not significantly change the size of the total vegetation C pools, but it significantly decreased the ratio of root：shoot（R：S）（P = 0.05） relative to controls. By contrast, N addition significantly increased the total vegetation C pools. The C pools in the LN, MN and HN treatments increased by 22, 39 and 44 %, respectively. MN produced the largest effect among the N concentrations,although differences between N-added treatments were not significant（P ？ 0.05）. N addition significantly reduced the ratio of root：shoot（R：S）（P = 0.03）. However, there were no significant interactive effects of water and N addition on the vegetation C pools.
基金Curtin University for an Australian Postgraduate AwardWater Research Australia and Chem Centre (Western Australia) for a PhD Top Up Scholarship
文摘Disinfection of water for human use is essential to protect against microbial disease;however, disinfection also leads to formation of disinfection by-products（DBPs）, some of which are of health concern. From a chemical perspective, swimming pools are a complex matrix, with continual addition of a wide range of natural and anthropogenic chemicals via filling waters, disinfectant addition, pharmaceuticals and personal care products and human body excretions. Natural organic matter, trace amounts of DBPs and chlorine or chloramines may be introduced by the filling water, which is commonly disinfected distributed drinking water. Chlorine and/or bromine is continually introduced via the addition of chemical disinfectants to the pool. Human body excretions（sweat, urine and saliva） and pharmaceuticals and personal care products（sunscreens, cosmetics, hair products and lotions） are introduced by swimmers. High addition of disinfectant leads to a high formation of DBPs from reaction of some of the chemicals with the disinfectant.Swimming pool air is also of concern as volatile DBPs partition into the air above the pool.The presence of bromine leads to the formation of a wide range of bromo-and bromo/chloro-DBPs, and Br-DBPs are more toxic than their chlorinated analogues. This is particularly important for seawater-filled pools or pools using a bromine-based disinfectant.This review summarises chemical contaminants and DBPs in swimming pool waters, as well as in the air above pools. Factors that have been found to affect DBP formation in pools are discussed. The impact of the swimming pool environment on human health is reviewed.
基金supported by the Strategic Priority Research Program-Climate Change:Carbon Budget and Related Issues of the Chinese Academy of Sciences(Grant No.XDA05110302)National Natural Science Foundation of China(NSFC)Major Research Project(Grant Nos.40890150 and 40890155)+2 种基金the National Basic Research Program of China for Structures,Variability,and Climatic Impacts of Ocean Circulation and Warm Pool in the Tropical Pacific Ocean(Grant No.2012CB417401)China Postdoctoral Science Foudation funded project(2012M521378)Chinese Scholarship Council,the Large-scale and Climate Dynamics Program of the US National Science Foundation(Grant Nos.AGS0553111 and AGS0852329)
文摘Theoretical and empirical studies have suggested that an underestimate of the ENSO asymmetry may be accompanied by a climatologically smaller and warmer western Pacific warm pool. In light of this suggestion, simulations of the tropical Pacific climate by 19 Coupled Model Intercomparison Project Phase 3 （CMIP3） climate models that do not use flux adjustment were evaluated. Our evaluation revealed systematic biases in both the mean state and ENSO statistics. The mean state in most of the models had a smaller and warmer warm pool. This common bias in the mean state was accompanied by a common bias in the simulated ENSO statistics： a significantly weak asymmetry between the two phases of ENSO. Moreover, despite the generally weak ENSO asymmetry simulated by all models, a positive correlation between the magnitude of the bias in the simulated warm-pool size and the magnitude of the bias in the simulated ENSO asymmetry was found. These findings support the suggested link between ENSO asymmetry and the tropical mean state--the climatological size and temperature of the warm pool in particular. Together with previous studies, these findings light up a path to improve the simulation of the tropical Pacific mean state by climate models： enhancing the asymmetry of ENSO in the climate models.
