Analysis and Assessment on the Heavy Metals in a Severely Degraded Subtropical Red Soil Region

5 different forests of Pinus massoniana, Schima superba, Liquidambar formosana, P. massoniana × S. superba, P. massoniana × L. formosana as the research object were set up to study the Cr, Cu and Zn content of degraded red soil region in subtropics. The soil heavy metal pollution degree was evaluated by national environmental quality standard (II class). The results showed that three soil metals of P. massoniana × S. superba were the highest, and the soil metals enrichment ability was strong. The order of single factor pollution index of metal elements was Cu (1.38) > Cr (0.81) > Zn (0.42), and moderately pollution, pollution warning and no pollution, respectively. There was no significant correlation between three soil heavy metals and soil total carbon (TC), total nitrogen (TN) and total phosphorus (TP). These results suggested that the accumulation of heavy metal elements was not derived from the parent material of soil. There was a significant positive correlation between the three metal elements which indicated that the sources of the three elements were similar. The structural equation model showed that the direct and indirect effects among the influencing factors ultimately affected the activity of heavy metals by cascade effects.

PLFA Analysis of Soil Microbial Community Structure in Different Forest Types

Soil soluble organic matter is an important component in the study of carbon and nitrogen cycling in terrestrial ecosystems. Soil microorganisms, as soil decomposers, participate in soil biogeochemical processes and play an important role in maintaining the balance of soil ecosystems. As a typical subtropical regional unit, Queensland, Australia, is a relatively concentrated distribution area of forests in Australia. It is very sensitive to climate change and plays an important role in Australian climate and even global climate change. Its unique natural environment and ecosystem occupy a special position in the world. However, the knowledge of available carbon and nitrogen pool and microbial activity in forest soil is still very limited. Pinus elliottii, Araucaria cunninghamii and Agathis australis are the three most important forest types in southern Queensland, Australia. In our research, the function and structural diversity of soil microbial communities of these three forest types were studied using biochemical and molecular biological methods, and the effective carbon and nitrogen pools of soil of different forest types and related microbial processes were discussed, which has important theoretical guiding significance for further research on the structure and function of soil ecosystem. The number of PLFAs in the soil of P. elliottii was 45, the number of PLFAs in the soil of Araucaria cunninghamii and Agathis australis was 39 and 35, respectively. The number and content of PLFAs monomer in P. elliottii were higher than those in the other two kinds of forest soil.

Comparison of Bioleaching of Heavy Metals from Sewage Sludge of Different Solid Concentrations Using Two Inocula

Two 10%(v/v) different inocula, iron-oxidizing bacteria and sulfur-oxidizing bacteria, were used to investigate the bioleaching of heavy metals from sewage sludge with 10-40 g/L sludge concentration in the batch experiment. The results demonstrated that most of bioleaching rates of Zn and Cu achieved above 80% and 60%, respectively, after 12 d in the sludge with different concentrations and inocula. The lower the solid concentration, the higher the removal rate of heavy metals and the quicker the removal speed in sludge. The system with iron-oxidizing bacteria had faster startup speed and was influenced by solid concentration lightly, while in the system with sulfur-oxidizing bacteria, the removal efficiency was affected by concentration seriously.

Effects of Stratification and Hormone Treatments on Germination and Physio-Biochemical Properties of <i>Taxus chinensis var. mairei</i>Seed

In order to learn dormancy mechanism of Taxtts chinensis var. mairei seed, effects of stratification and hormone treatments on physiological and biochemical indexes of the seeds after stratifying for eight months were researched. The content of amylase activity and soluble sugar gradually increased at first stratification, and then to the maximum for the end of after-ripening period. With the dormancy of seed relieving, some soluble sugar of endosperm was used or consumed by respiration and that led to their content decreased. Seed soluble protein was gradually accumulated at the beginning of stratification and then the initial raw material of protein synthesis of embryo during development had been used or in part converted into carbohydrates for energy consumption, so that the soluble protein content decreased. The fat and starch content slowly decreased during stratification, which showed that the storage of material had continually carrying out catabolism and conversion, which might provide energy sources for seed germination in the stratification process. The peroxidase activity of Taxus seeds increased gradually at the beginning of stratification, and then reached maximum point during stratification for 4 months in A1 and A2. The G-6-PDH and 6-PGDH joint activity was rapidly increased to reach the maximum during stratification for 4 months in A1, which showed the pentose phosphate pathway was activated at this time. The peroxidase activity rapidly increased might also be related to respiratory metabolic pathway during stratification. In plants, acid phosphatase hydrolyze PAM metabolites, namely phosphate material was related to energy metabolism, especially to high-energy phosphate, and phosphate enzyme activity changes affected the energy metabolism. The acid phosphatase activity of Taxus seeds in different treatments has no significant changes during stratification process, but there were two maximums. Energy metabolism might get benefit from the increase of acid phosphatase activity. There were significant differences in amylase activity, peroxidase activity, soluble sugar and soluble protein content with different treatments. Effect of promoting seed germination soaked by GA before stratification was obvious, but the concentration of GA should not be too high. The high concentration of GA caused seed to rot and reduce the seed germination rate. In this study, the highest germination rate of seed was 71.8% and soaked in 200 mg·L-1 gibberellin.

转Bt基因抗虫作物对非靶标害虫的影响

转基因作物的长期大面积种植,在为农业生产带来惠益的同时,对农业生态系统的健康和稳定可能会产生潜在的影响。转基因作物表达的Bt蛋白对靶标害虫起到较好的控制效果,而对Bt蛋白不敏感的非靶标害虫种群可能会迅速发展起来,对作物造成为害。随着抗虫转基因作物的连续多年种植,科学家们对于田间杀虫剂施用量的增减看法不尽一致。通过总结已有的研究报道,本文以Bt玉米和Bt棉花为例,分析了大田中非靶标害虫暴发的现状,以及暴发的主要原因(如杀虫剂的使用、害虫天敌减少和物种替代)。在生产实践中,抗虫作物的长期大面积释放导致广谱杀虫剂施用量减少,田间非靶标害虫数量上升。因此今后需要继续开展更多的研究来综合评估种植转Bt基因作物产生的长期潜在影响,优化害虫防治措施,避免非靶标害虫暴发。