Formation of secondary organic aerosols through photooxidation of isoprene   总被引：5，自引：0，他引：5  

Claeys M  Graham B  Vas G  Wang W  Vermeylen R  Pashynska V  Cafmeyer J  Guyon P  Andreae MO  Artaxo P  Maenhaut W 《Science (New York, N.Y.)》2004,303(5661):1173-1176

Detailed organic analysis of natural aerosols from the Amazonian rain forest showed considerable quantities of previously unobserved polar organic compounds, which were identified as a mixture of two diastereoisomeric 2-methyltetrols: 2-methylthreitol and 2-methylerythritol. These polyols, which have the isoprene skeleton, can be explained by OH radical-initiated photooxidation of isoprene. They have low vapor pressure, allowing them to condense onto preexisting particles. It is estimated that photooxidation of isoprene results in an annual global production of about 2 teragrams of the polyols, a substantial fraction of the Intergovernmental Panel on Climate Change estimate of between 8 and 40 teragrams per year of secondary organic aerosol from biogenic sources.  相似文献   

Ecotoxic impact of suspended solids collected from polluted surface waters     

Reinhilde Weltens  Hilda Witters  Philippe Corbisier 《Journal of Soils and Sediments》2001,1(4):223-233

Scope and background

Earlier studies showed that artificially contaminated particulate matter could be responsible for acute effects in water fleas and fish. Physical/chemical measurements on suspended solids and river water collected in the field showed that these samples were often contaminated with mixtures of toxic molecules.

Objectives

The present pilot study was started to investigate the possible ecotoxic impact of suspended solids collected in situ.

Methods

Suspended solids and river waters were collected from 22 locations of polluted rivers in the Flanders. An extensive list of chemical components and physical parameters were measured in these matrices. Partition coefficients for water column and suspended solids were calculated. Toxicity of suspensions of solid materials was investigated in 3 test organisms of different trophic levels: Bacteria (BIOMET®), filter feeder (Daphnia magna) and fish (rainbow trout (Oncor-hynchus mykiss) or zebrafish (Danio rerio)). The acute toxicity was measured in a worst-case scenario using high concentrations of solids resuspended in standard medium and at standard conditions.

Results and discussion

The partition coefficients were highly variable, showing that this parameter is not simply related to the octanol/water partition coefficient or to the total organic carbon content of the solids in field conditions, as is often assumed in exposure models. The field material of some locations was toxic. Bacteria were the most sensitive test organisms, showing EC20 values at field relevant concentrations. For some samples, acute toxic effects were seen in fish and water fleas. The chemical content of the samples was very complex and could not simply be related to toxicity. Some samples were highly contaminated with toxic chemicals and yet caused no toxic effects, while other samples did not show extremely high concentrations, but were toxic to the test organisms.

Conclusions

Results show that biotests are needed, next to chemical measurements, to estimate the toxic impact of complex environmental matrices. A better understanding of the adsorption/desorption behaviour of toxic molecules in the water compartment and in living organisms will contribute to a better environmental risk assessment.

Recommendations and outlook

The results indicate that the ecotoxic impact of suspended solids in the field should be further investigated in realistic (non-worst-case) conditions, i.e. for chronic effects at field relevant concentrations. And more extensive scientific research is needed to understand the adsorption/desorption behaviour of toxic molecules in different physicochemical matrices.  相似文献