Petroleum hydrocarbons, mainly consisting of n-alkanes and polycyclic aromatic hydrocarbons (PAHs), are considered as priority pollutants and biohazards in the environment, eventually affecting the ecosystem and human health. Though many previous studies have investigated the change of bacterial community and alkane degraders during the degradation of petroleum hydrocarbons, there is still lack of understanding on the impacts of soil alkane contamination level. In the present study, microcosms with different n-alkane contamination (1%, 3% and 5%) were set up and our results indicated a complete alkane degradation after 30 and 50 days in 1%- and 3%-alkane treatments, respectively. In all the treatments, alkanes with medium-chain length (C11-C14) were preferentially degraded by soil microbes, followed by C27-alkane in 3% and 5% treatments. Alkane contamination level slightly altered soil bacterial community, and the main change was the presence and abundance of dominant alkane degraders. Thermogemmatisporaceae, Gemmataceae and Thermodesulfovibrionaceae were highly related to the degradation of C14- and C27-alkanes in 5% treatment, but linked to alkanes with medium-chain (C11-C18) in 1% treatment and C21-alkane in 3% treatment, respectively. Additionally, we compared the abundance of three alkane-monooxygenase genes, e.g., alk_A, alk_P and alk_R. The abundance of alk_R gene was highest in soils, and alk_P gene was more correlated with alkane degradation efficiency, especially in 5% treatment. Our results suggested that alkane contamination level showed non-negligible effects on soil bacterial communities to some extents, and particularly shaped alkane degraders and degrading genes significantly. This study provides a better understanding on the response of alkane degraders and bacterial communities to soil alkane concentrations, which affects their biodegradation process.
Background, aim, and scope Endosulfan is one of the organochlorine pesticides (OCPs) and also a candidate to be included in a group of new persistent
organic pollutants (UNEP 2007). The first national endosulfan usage inventories in China with 1/4° longitude by 1/6° latitude resolution has been reported
in an accompanying paper. In the second part of the paper, we compiled the gridded historical emissions and soil residues
of endosulfan in China from the usage inventories. Based on the residue/emission data, gridded concentrations of endosulfan
in Chinese soil and air have been calculated. These inventories will provide valuable data for the further study of endosulfan.
Methods Emission and residue of endosulfan were calculated from endosulfan usage by using a simplified gridded pesticide emission
and residue model—SGPERM, which is an integrated modeling system combining mathematical model, database management system,
and geographic information system. By using the emission and residue inventories, annual air and soil concentrations of endosulfan
in each cell were determined.
Results and discussion Historical gridded emission and residue inventories of α- and β-endosulfan in agricultural soil in China with 1/4° longitude
by 1/6° latitude resolution have been created. Total emissions were around 10,800 t, with α-endosulfan at 7,400 t and β-endosulfan
at 3,400 t from 1994 to 2004. The highest residues were 140 t for α-endosulfan and 390 t for β-endosulfan, and the lowest
residues were 0.7 t for α-endosulfan and 170 t for β-endosulfan in 2004 in Chinese agricultural soil where endosulfan was
applied. Based on the emission and residue inventories, concentrations of α- and β-endosulfan in Chinese air and agricultural
surface soil were also calculated for each grid cell. We have estimated annual averaged air concentrations and the annual
minimum and maximum soil concentrations across China. The real concentrations will be different from season to season. Although
our model does not consider the transport of the insecticide in the atmosphere, which could be very important in some areas
during some special time, the estimated concentrations of endosulfan in Chinese air and soil derived from the endosulfan emission
and residue inventories are in general consistent with the published monitoring data.
Conclusions To our knowledge, this work is the first inventory of this kind for endosulfan published on a national scale. Concentrations
of the chemical in Chinese air and agricultural surface soil were calculated for each grid cell. Results show that the estimated
concentrations of endosulfan in Chinese air and soil agree reasonably well with the monitoring data in general.
Recommendations and perspectives The gridded endosulfan emission/residue inventories and also the air and soil concentration inventories created in this study
will be updated upon availability of new information, including usage and monitoring data. The establishment of these inventories
for the OCP is important for both scientific communities and policy makers. 相似文献