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Ge H.,Tongji University | Lin Z.,Tongji University | Lin Z.,Collaborative Innovation Center for Regional Environmental Quality | Yao Z.,Tongji University | And 3 more authors.
Aquatic Toxicology | Year: 2014

The use of herbicide mixtures has become a cost-effective strategy against the evolution of herbicide resistance to protect global food production. Much research has focused on investigating either the herbicidal activities or the toxicity effects of herbicides; however, few of them have investigated both factors. This study investigates the balance between herbicidal activity for Selenastrum capricornutum and toxicity effect toward Photobacterium phosphoreum by determining the joint effects of triazine (simetryn, atrazine, prometon and prometryn) and phenylurea (fenuron, monuron, monolinuron and diuron) herbicides. The results showed that among the four triazines, only simetryn exhibited a unique effect (formation of a pi-sigma bond with the D1 microalga protein and an H-bond with the Luc photobacterial protein); and among 16 triazine-phenylurea binary mixtures, only the mixtures containing simetryn resulted in TU1 values (herbicidal activities of mixtures on S. capricornutum) >TU2 values (toxicity effects of mixtures on P. phosphoreum). However, the other 12 mixtures, which did not contain simetryn, showed the opposite result (TU1

Wang D.,Tongji University | Gao Y.,Tongji University | Lin Z.,Tongji University | Lin Z.,Collaborative Innovation Center for Regional Environmental Quality | And 2 more authors.
Aquatic Toxicology | Year: 2014

Metal oxide nanoparticles (NPs) have been used increasingly and are likely to accumulate in natural water bodies, where they encounter and interact with other environmental chemicals. These interactions result in joint effects on biological systems and the environment. However, compared with the intensive research examining the toxicities of individual NPs, the toxicities of NP mixtures remain relatively unexplored. In this work, we studied the joint effects of NPs and their most likely coexisting chemicals in the environment, including NPs with different compositions, humic substances, and surfactants. Our results indicate that the joint effects of NP mixtures were usually simple addition, which is commonly adopted in real risk assessment. However, the joint effects obtained for mixtures that contained ZnO were exclusively associated with antagonism. In addition, the mixtures of NPs and surfactants resulted in complex joint effects, i.e., antagonistic, additive, and synergistic effects were found for the mixtures with ZnO, NiO, and Fe-oxide, respectively. Our study suggests that the assessments of the ecological risk of NPs, particularly ZnO NPs, should consider the impact of their coexisting chemicals in the environment. © 2014 Elsevier B.V.

Wang D.,Tongji University | Lin Z.,Tongji University | Lin Z.,Collaborative Innovation Center for Regional Environmental Quality | Yao Z.,Tongji University | Yu H.,Nanjing University
Chemosphere | Year: 2014

The potential toxicities of nanoparticles (NPs) have been intensively discussed over the past decade. In addition to their single toxicities, NPs can interact with other environmental chemicals and thereby exert joint effects on biological systems and the environment. The present study investigated the combined toxicities of NPs and surfactants, which are among the chemicals that most likely coexist with NPs. Photobacterium phosphoreum was employed as the model organism. The results indicate that surfactants with different ion types can alter the properties of NPs (i.e., particle size and surface charge) in different ways and present complex joint effects on NP toxicities. Mixtures of different NPs and surfactants exhibited antagonistic, synergistic, and additive effects. In particular, the toxicity of ZnO was observed to result from its dissolved Zn2+; thus, the joint effects of the ZnO NPs and surfactants can be explained by the interactions between the Zn ions and the surfactants. Our study suggests that the potential hazards caused by mixtures of NPs and surfactants are different from those caused by single NPs. Because surfactants are extensively used in the field of nanotechnology and are likely to coexist with NPs in natural waters, the ecological risk assessments of NPs should consider the impacts of surfactants. © 2014 Elsevier Ltd.

Zheng B.,Tsinghua University | Zhang Q.,Tsinghua University | Zhang Q.,Collaborative Innovation Center for Regional Environmental Quality | Zhang Y.,Tsinghua University | And 10 more authors.
Atmospheric Chemistry and Physics | Year: 2015

Severe regional haze pollution events occurred in eastern and central China in January 2013, which had adverse effects on the environment and public health. Extremely high levels of particulate matter with aerodynamic diameter of 2.5 μm or less (PM2.5) with dominant components of sulfate and nitrate are responsible for the haze pollution. Although heterogeneous chemistry is thought to play an important role in the production of sulfate and nitrate during haze episodes, few studies have comprehensively evaluated the effect of heterogeneous chemistry on haze formation in China by using the 3-D models due to of a lack of treatments for heterogeneous reactions in most climate and chemical transport models. In this work, the WRF-CMAQ model with newly added heterogeneous reactions is applied to East Asia to evaluate the impacts of heterogeneous chemistry and the meteorological anomaly during January 2013 on regional haze formation. As the parameterization of heterogeneous reactions on different types of particles is not well established yet, we arbitrarily selected the uptake coefficients from reactions on dust particles and then conducted several sensitivity runs to find the value that can best match observations. The revised CMAQ with heterogeneous chemistry not only captures the magnitude and temporal variation of sulfate and nitrate, but also reproduces the enhancement of relative contribution of sulfate and nitrate to PM2.5 mass from clean days to polluted haze days. These results indicate the significant role of heterogeneous chemistry in regional haze formation and improve the understanding of the haze formation mechanisms during the January 2013 episode. © Author(s) 2015.

Cheng Y.,Tsinghua University | He K.-B.,Tsinghua University | He K.-B.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex | He K.-B.,Collaborative Innovation Center for Regional Environmental Quality
Environmental Pollution | Year: 2015

Current understanding of organic aerosol (OA) is challenged by the large gap between simulation results and observational data. Based on six campaigns conducted in a representative mega city in China, this study provided an annual perspective of the uncertainties in observational OA data caused by sampling artifacts. Our results suggest that for the commonly-used sampling approach that involves collection of particles on a bare quartz filter, the positive artifact could result in a 20-40 % overestimation of OA concentrations. Based on an evaluation framework that includes four criteria, an activated carbon denuder was demonstrated to be able to effectively eliminate the positive artifact with a long useful time of at least one month, and hence it was recommended to be a good choice for routine measurement of carbonaceous aerosol. © 2015 Elsevier Ltd.All rights reserved.

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