Habitat suitability evaluation of invasive plant species Datura stramonium in Liaoning Province: Based on Biomod2 combination model.

Datura stramonium, as a major invasive plant in Liaoning Province, is difficult to be removed after its successful invasion, and is a great threat to ecological environment and biodiversity. To evaluate the habitat suitabi-lity of D. stramonium, we collected its geographic distribution data in Liaoning Province through field investigation and database query, and using the Biomod2 combination model, and investigated its potential and suitable distribution areas and main influencing environmental variables at present and under future climate change scenarios, respectively. The results showed that the combined model which composed of GLM (generalized linear model), GBM (generalized boosting regression model), RF (random forest model), and MaxEnt (maximum entropy model) had a good performance. By classifying the habitat suitability of D. stramonium into four categories: high-, medium-, low- and un-suitable habitats, we found that the high-suitable habitats were generally distributed in the northwest and south of Liaoning Province, with an area of about 3.81×104 km2, accounting for 25.8% of the total area. The medium-suitable habitats were mostly distributed in the northwest and central parts of Liaoning Province, with an area of about 4.19×104 km2, accounting for 28.3% of the total area. Slope and clay content of topsoil (0-30 cm) were the two main variables explaining the habitat suitability of D. stramonium, and the total suitability of D. stramonium first increased and then decreased with the increasing slope and clay content of topsoil in this region. Under future climate change scenarios, the total suitability of D. stramonium showed an expanding trend, and its suitability would be obviously increased in Jinzhou, Panjin, Huludao, and Dandong.

[Recognition of priority area of biodiversity conservation in Liaoning Province, Northeast China]. / è¾½å®çœç”Ÿç‰©å¤šæ ·æ€§ä¿æŠ¤ä¼˜å ˆåŒºè¯†åˆ«.

Priority areas of biodiversity conservation (PABC) were classified to strengthen biodiversity conservation in China. As there are no such priority areas in Liaoning Province, China, it is important to make up this gap. After calculation of seven indices at three composition levels (ecosystem conservation, human interference, and regionalization for biodiversity conservation), index values, composition values, and comprehensive recognition value for PABCs in Liaoning Province were obtained successively. Suggested territorial scopes of Western Liaoning Priority Area (WPA) and Eastern Liaoning Priority Area (EPA) were then determined in terms of administrative boundaries of towns, counties, and nature reserves. Among them, WPA covers an area of 12951 km2, with 53.6% of forest coverage and nine national or provincial nature reserves. The main ecological function of WPA is soil and water conservation. EPA is 20057 km2 in area, with 78.9% of forest cove-rage and eight national or provincial nature reserves. Water resource conservation is the main ecological function of EPA. Key protected species at national or provincial level and the important ecosystems are densely distributed in those priority areas. It is urgent to carry out biodiversity conservation in these PABCs.

[Effect of Decomposing Products of Immobilized Carriers on Desorption of Pyrene in Contaminated Soil].

Batch experiments were conducted to investigate the effect of soluble and insoluble decomposing products (decomposed for 1 day and 120 day; noted by DP1 and DP120, respectively) from immobilized carriers (corncob) on the desorption of pyrene in PAH-contaminated soil (120 d ageing, 20 mg x kg(-1)). It was found that (1) adding decomposing products of immobilized carriers could not only increase the rapidly desorbing fraction, but also improve the desorption rate of pyrene. The desorption rates of pyrene increased from 20% to 81.8% and 84.5% because of adding insoluble DP1 and DP120, and from 40% to 89.6% and 88.5% because of adding soluble DP1 and DP120. (2) The sorption amounts of pyrene by insoluble DP1 and.DP120 were 9. 4 and 16. 6 times higher than that by natural corncob, respectively. The sorption amounts of XAD-2 resins were increased by 1.5 and 3.1 times due to the added soluble DP1 and DP120, respectively. These results indicated that decomposing products of immobilized carries could improve the desorption of pyrene by sorption or activation in contaminated soil.

[Effects of root exudates of clover (Trifolium repens) on PAH microbial degradation and dioxygenase].

To demonstrate rhizospheric effect on the mechanism of (polycyclic aromatic hydrocarbon) PAH degradation, and to establish a proper joint phyto-microbial remediation mode, microcosms containing microorganisms and PAHs (pyrene and benzo[a]Pyrene) were added with clover (Trifolium repens) root exudates to study their effects on PAH degradation. Dioxygenase gene and 16S rDNA gene copy number changes during the biodegradation process were analyzed, and the microorganism with a good ability for degrading PAHs was identified. The results showed that Mycobacterium M1 had the capability to degrade PAHs. When total organic carbon (TOC) concentration of clover root exudates was 35.5 mg · L(-1), pyrene and benzo[a]pyrene degradation rates increased significantly, and the proportion of dioxygenase gene to 16S rDNA of Mycobacterium M1 increased. In the biodegradation process, dioxygenase gene copy number increased significantly, whereas 16S rDNA copy number increase was not so obvious, showing that the former was related to degradation process, but the latter was related to microbial numbers. It was concluded that the clover root exudates promoted the dioxygenase gene copy number of Mycobacterium M1, which contributed to the degradation of PAHs.

[Assessment of bioaccessibility of PAHs in microbial degradation process using solid phase micro extraction and solid phase extraction].

In order to demonstrate the variation of bioaccessibility of PAHIs in microbial degradation process, PAH contaminated coking plant soil was remediated using microbial agent, and the bioaccessibility of PAHs was assessed using solid phase micro extraction (SPME) and solid phase extraction (SPE), difference and correlation between PAH degradation and PAH bioaccessbility variation were also analyzed. Results showed that the dominant PAHs in the coking plant soil and its pore water were low molecular weight (LMW) PAHs, and 68.3% of total PAH was degraded by the microbial agent, which was mainly due to the LMW PAH degradation. Decrease of PAH concentration in soil pore water was also contributed by LMW PAHs, however, individual PAH reductions in soil pore water were lower than those PAH degradations. Fast desorption fraction was calculated from Tenax-TA extraction, and those fractions for LMW PAHs decreased, while those for high molecular weight (HMW) PAHs did not change significantly. Strong correlation between PAH degraded and PAH concentration in soil pore water or fast desorption fraction of Tenax-TA extraction was observed. The results above demonstrated that PAH concentration in soil pore water and fast desorption fraction of Tenax-TA extraction can be used to predict PAH degradation in soil, which provided some theoretical basis for the remediation of PAH contaminated soil from coking plant.

[Study on phytoremediation of phenanthrene-contaminated soil with alfalfa (Medicago sativa L.)].

Pot experiment was used to investigate phytoremediation of phenanthrene-contaminated soil with alfalfa (Medicago sativa L.). Results indicated that phenanthrene had inhibitive effect on alfalfa growth, and higher phenanthrene concentration seriously prevent alfalfa growth. When the concentration was 445.22 mg/kg, the shoot and root biomasses were only 57.31% and 31.20% of control respectively. Alfalfa significantly promoted phenanthrene degradation in the soil. After 60 days, 85.68%-91.40% and 75.25%-86.61% of spiked phenanthrene disappeared from the rhizosphere and non-rhizosphere soils respectively. And the average removal ratio of phenanthrene in rhizosphere soils was 6.33% higher than that in non-rhizoshpere soils. The residual concentration of phenanthrene in the rhizosphere was lower than that in the non-rhizosphere but the dehydrogenase activity was on the contrary. With phenanthrene concentration increase the removal ratio and dehydrogenase activity decreased. A positive correlation was observed between the soil dehydrogenase activity and the removal ratio of phenanthrene in both the rhizosphere and non-rhizosphere soils. Therefore the presence of alfalfa roots was effective in promoting the phytoremediation of phenanthrene.

Photochemical behavior of benzo[a]pyrene on soil surfaces under UV light irradiation.

The rates of photodegradation and photocatalysis of benzo[a]pyrene (BaP) on soil surfaces under UV light have been studied. Different parameters such as temperature, soil particle sizes, and soil depth responsible for photodegradation, catalyst loads and wavelength of UV irradiation blamed for photocatalysis have been monitored. The results obtained indicated that BaP photodegradation follows pseudo-first-order kinetics. BaP photodegradation was the fastest at 30 degrees C . The rates of BaP photodegradation at different soil particle size followed the order: less than 1 mm>less than 0.45 mm>less than 0.25 mm. When the soil depth increased from 1 mm to 4 mm, the half-life increased from 13.23 d to 17.73 d. The additions of TiO2 or Fe2O3 accelerated the photodegradation of BaP, and the photocatalysis of BaP follows pseudo-first-order kinetics. Changes in catalyst loads of TiO2 (0.5%, 1%, 2%, and 3% (wt)) or Fe2O3 (2%, 5%, 7%, and 10% (wt)) did not significantly affect the degradation rates. Both BaP photocatalysis in the presence of TiO2 and Fe2O3 were the fastest at 254 nm UV irradiation.

Temporal-spatial distribution and variability of cadmium contamination in soils in Shenyang Zhangshi irrigation area, China.

Heavy metal contamination in soils has been of wide concern in China in the last several decades. The heavy metal contamination was caused by sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides and so on. The Shenyang Zhangshi irrigation area (SZIA) in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years duration. This study investigated the spatial distribution and temporal variation of soil cadmium contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd of soils was analyzed and then the spatial distribution and temporal variation of Cd in soils was modelled using kriging methods. The kriging map showed that long-term sewage irrigation had caused serious Cd contamination in topsoil and subsoil. In 2004, the Cd mean concentrations were 1.698 and 0.741 mg/kg, and the maxima 10.150 and 7.567 mg/kg in topsoils (0-20 cm) and subsoils (20-40 cm) respectively. These values are markedly more than the Cd levels in the second grade soil standard in China. In 1990, the Cd means were 1.023 and 0.331 mg/kg, and the maxima 9.400 and 3.156 mg/kg, in topsoils and subsoils respectively. The soil area in 1990 with Cd more than 1.5 mg/kg was 2701 and 206.4 hm(2) in topsoils and subsoils respectively; and in 2004, it was 7592 and 1583 hm(2), respectively. Compared with that in 1990, the mean and maximum concentration of Cd, as well as the soil area with Cd more than 1.5 mg/kg had all increased in 2004, both in topsoils and subsoils.

Greenhouse gas emissions from a constructed wetland for municipal sewage treatment.

The fluxes of greenhouse gases (methane and nitrous oxide) emission from a constructed wetland in the Eastern China as municipal sewage treatment were measured from June 1999 to August 2000 by the closed chamber method. The constructed wetland for municipal sewage treatment is a significant source of methane, up to 976.6 x 10(6) g CH4/a, which was emitted from the constructed wetland with the area of 495,000 m2 and wastewater loading rate of 12,000 m3/d. Its daily mean methane flux reached 5.22 g CH4/(m2.d), 250 times as much as that in natural wetland in the same latitude region. 227.8 mg CH4 was produced from the treatment of 1 liter wastewater, up to 700-1000 times as much as that in the secondary treatment. The emission of nitrous oxide from the constructed wetland is not higher than that from secondary treatment of wastewater, only 0.07 mg N2O/L.