Acute and chronic impacts caused by aromatic hydrocarbons on bacterial communities at Boa Viagem and Forte do Rio Branco Beaches, Guanabara Bay, Brazil

The bacterial community presented significantly different hydrocarbonoclastic activity under acute and chronic impacts. Benzoic acid, toluene, benzene and xylene were used in final concentrations of 5, 10 and 15 mM and bacterial biomass was quantified through protein dosage. Under acute impact, the highest biomass percentages occurred between the 11th and 14th days; under chronic impact, between the 20th and 29th days. Under acute and chronic impacts, the bacterial biomass presented higher nutritional specialization at Boa Viagem Beach, using the aromatic hydrocarbons up to a concentration of 15 mM. Under acute impact, the concentration of the hydrocarbons constituted a critical factor for the bacterial flora from Forte do Rio Beach, because biomass increases only occurred in concentrations of 5 mM; under chronic impact, the aromatic hydrocarbons induced the specialization and increased bacterial biomass for 15 mM toluene. Benzoic acid (15 mM) was used by the bacteria from Boa Viagem and Forte do Rio Branco Beaches.     

Genotoxicity of two novel pesticides for the earthworm, Eisenia fetida

In this paper, several studies were conducted to evaluate the genotoxicity of two pesticides, Imidacloprid and RH-5849, for earthworm (Eisenia fetida). Earthworms were exposed in different exposure systems to evaluate their acute toxicity and the genotoxicity of the two pesticides was evaluated by using the method of sperm deformity assessment, micronucleus test of root tip cells in Vicia faba, a mouse bone-marrow micronucleus test, and comet assay. LC(50) (interpolated concentration at which 50% mortality of test population occurs) for earthworms varied in different exposure systems. The results indicated that Imidacloprid was consistently more toxic than RH-5849 in all exposure systems. In this study, sperm deformity test was used to detect the potential adverse influences of pesticides on the reproduction of earthworms. The results demonstrated that significant induction of sperm deformity (p<0.01) and a dose-effect relationship displayed at Imidacloprid concentrations higher than 0.5 mg/kg dry soil. However, the sperm deformity frequency of groups exposed to RH-5849 did not show significant difference (p>0.05) from the control until the dose reached 100 mg/kg dry soil. The results of the V. faba micronucleus tests showed that micronuclei frequency of the exposed group did not show significant difference (p>0.05) from the control until the concentration of Imidacloprid and RH-5849 reached 100 mg/ml. The results of the mouse bone-marrow micronuclei test also indicate that two pesticides did not show significant effects (p>0.05) on the micronuclei frequency in mice bone-marrow cells until the dose reached 100 mg/kg for Imidacloprid and 300 mg/kg for RH-5849 (2/3 LD(50)). Although no genotoxicity was detected by using the micronucleus tests, the results of the comet assay showed that the two pesticides induce significant DNA damage (p<0.01) in earthworms and dose-effect relationships were displayed. The 'earthworm comet assay' is a rapid and sensitive way to screen chemicals or terrestrial environments for their DNA-damaging properties.     

基于藻细胞形态和光合特征的水源地藻类种群时空分布机制及预警防控

为明晰藻细胞最基本属性细胞形态在藻种时空分布与竞争演替中扮演的角色,选择来自蓝藻、绿藻等藻门的45个具有不同细胞形态特征的常见藻种,通过实验室分析藻细胞形态特征参数与光合特征间相关关系,并基于于桥水库藻类种群监测数据探究藻类形态时空分布的驱动因素。研究发现,反映藻细胞光合作用过程中捕光潜力的细胞投影面积 (CPA) 是影响藻种光合特性的关键形态学参数;通过构建CPA与光系统II中调节性能量耗散量子产量 (Y(NPQ))、光响应曲线初始斜率 (α) 、最大电子传递速率 (ETRmax) 等光合参数建的关系模型,发现CPA与Y(NPQ)呈现强正相关关系 (R² = 0.31±0.01,p < 0.001) ,Y(NPQ)是影响藻类种群时空分布的关键参数。于桥水库中藻类种群的综合Y(NPQ)具有显著季节性,由春季到夏季逐渐降低,夏季藻类综合Y(NPQ)最低 (0.057±0.075) ,秋冬季呈现增加趋势,冬季藻类综合Y(NPQ)最高 (0.072±0.062) 。此外,藻类种群综合Y(NPQ)随水深增加呈降低趋势,Y(NPQ)是影响藻类形态空间分布的重要因素。基于于桥水库数据制定了以水体Y(NPQ)为核心的有害藻类预警防控体系,以期为实现针对水源地不同形态有害藻类的预警提供参考。     

Biodegradation of 2,4,6-trichlorophenol in the presence of primary substrate by immobilized pure culture bacteria

In this study, pure strains that are capable of utilizing 2,4,6-trichlorophenol have been isolated from the mixed culture grown on substrates containing chlorophenolic compounds. Studies have been carried out on the capability of these isolated pure strains in suspended and immobilized forms to decompose 2,4,6-trichlorophenol. Additionally, the influence of primary substrates (e.g., phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol) on the decomposition of 2,4,6-trichlorophenol by the isolated pure strains grown in immobilized form is also investigated. The results are: Through bacterial isolation and identification, three pure strains have been obtained: Pseudomonas spp. strain 01, Pseudomonas spp. strain 02 and Agrobacterium spp. Whether in suspended or immobilized forms, all strains have poor removal efficiencies of 2,4,6-trichlorophenol. However, addition of 200 mg/l phenol will enable the immobilized Pseudomonas spp. strain 01, and Pseudomonas spp. strain 02 to achieve 65% and 48% removal of 2,4,6-trichlorophenol, respectively. Addition of phenol will assist the immobilized Pseudomonas spp. strain 02 in achieving removal of 2,4,6-trichlorophenol but the removal efficiency is not good if the phenol concentration is too low. The optimum phenol concentration should be between 200 and 400 mg/l.     

Association between air pollution and COVID-19 infection: evidence from data at national and municipal levels

Environmental Science and Pollution Research - The impact of high concentrations of air pollution on COVID-19 has been a major air quality and life safety issue in recent studies. This study aimed...     

Facile in situ synthesis of silver nanocomposites based on cellulosic paper for photocatalytic applications

Environmental Science and Pollution Research - In this work, various photocatalysts were synthesized with an impregnation-precipitation process to in situ decorate Ag-based nanoparticles (NPs,...     

Impact of invasive ant species on native fauna across similar habitats under global environmental changes

Environmental Science and Pollution Research - Biotic invasions can predominantly alter the dynamics, composition, functions, and structure of natural ecosystems. Social insects, particularly ants,...     

Review and prospects of mining chemical dust suppressant: classification and mechanisms

Environmental Science and Pollution Research - Coal mine pollution is a serious threat to the mine safe production and occupational health of miners. Chemical dust suppression can effectively...     

Simultaneous nitrification and denitrification in a PCL-supported constructed wetland with limited aeration

Environmental Science and Pollution Research - Considerable advances have been made in the substrate design and operation strategies of constructed wetlands to facilitate nitrogen elimination....     

Shaping effects of rice,wheat, maize,and soybean seedlings on their rhizosphere microbial community

The rhizosphere microbiome plays critical roles in plant growth and is an important interface for resource exchange between plants and the soil environment. Crops at various growing stages, especially the seedling stage, have strong shaping effects on the rhizosphere microbial community, and such community reconstruction will positively feed back to the plant growth. In the present study, we analyzed the variations of bacterial and fungal communities in the rhizosphere of four crop species: rice, soybean, maize, and wheat during successive cultivations (three repeats for the seedling stages) using 16S rRNA gene and internal transcribed spacer (ITS) high-throughput sequencing. We found that the relative abundances of specific microorganisms decreased after different cultivation times, e.g., Sphingomonas, Pseudomonas, Rhodanobacter, and Caulobacter, which have been reported as plant-growth beneficial bacteria. The relative abundances of potential plant pathogenic fungi Myrothecium and Ascochyta increased with the successive cultivation times. The co-occurrence network analysis showed that the bacterial and fungal communities under maize were much more stable than those under rice, soybean, and wheat. The present study explored the characteristics of bacteria and fungi in crop seedling rhizosphere and indicated that the characteristics of indigenous soil flora might determine the plant growth status. Further study will focus on the use of the critical microorganisms to control the growth and yield of specific crops.