The levels of metals in sediments of urban river ecosystems are crucial for aquatic environmental health and pollution assessment. Yet little is known about the interaction of nutrients with metals for environmental risks under contamination accumulation. Here, we combined hierarchical cluster, correlation, and principal component analysis with structural equation model (SEM) to investigate the pollution level, source, toxicity risk, and interaction associated with metals and nutrients in the sediments of a river network in a city area of East China. The results showed that the pollution associated with metals in sediments was rated as moderate degree of contamination load and medium-high toxicity risk in the middle and downstream of urban rivers based on contamination factor, pollution load index, and environmental toxicity quotient. The concentration of mercury (Hg) and zinc (Zn) showed a significant correlation with toxic risks, which had more contribution to toxicity than other metals in the study area. Organic nitrogen and organic pollution index showed heavily polluted sediments in south of the study area. Though correlation analysis indicated that nutrients and metals had different input zones from anthropogenic sources in the urban river network, SEM suggested that nutrient accumulation indirectly intensified toxicity risk of metals by 13.6% in sediments. Therefore, we suggested the combined consideration of metal toxicity risk with nutrient accumulation, which may provide a comprehensive understanding to identify sediment pollution.
The consequence of polycyclic aromatic hydrocarbons (PAHs) in the environment is of great concern. The hydrophobic properties
of PAHs significantly impact phase distribution causing limited bioavailability. Enhanced biodegradation has been extensively
carried out by surfactants and the redeployment effect was recognized. However, the quantitative relationship concerning the
impact of solids was rarely reported. A batch of biphasic tests were carried out by introducing Mycobacterium vanbaalenii PYR-1 and hydroxypropyl-β-cyclodextrin (HPCD) into a mixture of phenanthrene solution and various glass beads (GB37-63, GB105-125, and GB350-500).
The comparative results demonstrated that HPCD had little effect on microbial growth and was not degradable by bacterium.
A model was proposed to describe the biodegradation process. The regression results indicated that the partition coefficient
kd (1.234, 0.726 and 0.448 L·g−1) and the degradation rate k (0 mmol·L−1: 0.055, 0.094, and 0.112; 20 mmol·L−1: 0.126, 0.141, and 0.156; 40 mmol·L−1: 0.141, 0.156 and 0.184 d−1) were positively and negatively correlated with the calculated total surface area (TSA) of solids, respectively. Degradation
enhanced in the presence of HPCD, and the enhancing factor f was calculated (20 mmol·L−1: 15.16, 40.01, and 145.5; 40 mmol·L−1: 13.29, 37.97, and 138.4), indicating that the impact of solids was significant for the enhancement of biodegradation. 相似文献
This report shows an increase of PAH-related microbial functional genes with PAH concentration in soils. Adaptation of microbial communities to organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) is a crucial issue. However, there is little knowledge on mechanisms ruling microbial community selection. Here, we studied microbial functional genes in soils contaminated by PAHs. We used GeoChip, an advanced functional gene array for gene analysis. Soil PAH concentrations were measured and microbial functional genes were categorized. PAH-related microbial functional genes, bph, nah, nidA, phd, dfb, and qor, were quantitatively expressed. Total microbial functional genes and PAH-related microbial functional genes were compared with PAH concentration by cluster analysis and curve-fitting analysis. We found that the average abundance of PAH-related microbial functional genes increased from 0.13 to 0.33, whereas that of total microbial functional genes decreased from 0.22 to 0.10 when PAHs concentration increased from 1.01 to 164.28 mg kg?1. It was also found that the classification of microbial community structure characteristics based on PAH-related microbial functional genes was closely similar to the classification based on PAHs concentration. Findings reveal that PAH stress promotes the dominance of PAH-related microbial communities. 相似文献
The consequence of polycyclic aromatic hydrocarbons (PAHs) in the environment is of great concern. The hydrophobic properties of PAHs significantly impact phase distribution causing limited bioavailability. Enhanced biodegradation has been extensively carried out by surfactants and the redeployment effect was recognized. However, the quantitative relationship concerning the impact of solids was rarely reported. A batch of biphasic tests were carried out by introducing Mycobacterium vanbaalenii PYR-1 and hydroxypropyl-β-cyclodextrin (HPCD) into a mixture of phenanthrene solution and various glass beads (GB37-63, GB105-125, and GB350-500). The comparative results demonstrated that HPCD had little effect on microbial growth and was not degradable by bacterium. A model was proposed to describe the biodegradation process. The regression results indicated that the partition coefficient kd (1.234, 0.726 and 0.448 L·g?1) and the degradation rate k (0 mmol·L?1: 0.055, 0.094, and 0.112; 20 mmol·L?1: 0.126, 0.141, and 0.156; 40 mmol·L?1: 0.141, 0.156 and 0.184 d?1) were positively and negatively correlated with the calculated total surface area (TSA) of solids, respectively. Degradation enhanced in the presence of HPCD, and the enhancing factor f was calculated (20 mmol·L?1: 15.16, 40.01, and 145.5; 40 mmol·L?1: 13.29, 37.97, and 138.4), indicating that the impact of solids was significant for the enhancement of biodegradation. 相似文献
The consequence of polycyclic aromatic hydrocarbons (PAHs) in the environment is of great concern. The hydrophobic properties of PAHs significantly impact phase distribution causing limited bioavailability. Enhanced biodegradation has been extensively carried out by surfactants and the redeployment effect was recognized. However, the quantitative relationship concerning the impact of solids was rarely reported. A batch of biphasic tests were carried out by introducing Mycobacterium vanbaalenii PYR-1 and hydroxypropyl-β-cyclodextrin (HPCD) into a mixture of phenanthrene solution and various glass beads (GB37-63, GB105-125, and GB350-500). The comparative results demonstrated that HPCD had little effect on microbial growth and was not degradable by bacterium. A model was proposed to describe the biodegradation process. The regression results indicated that the partition coefficient kd (1.234, 0.726 and 0.448 L·g−1) and the degradation rate k (0 mmol·L−1: 0.055, 0.094, and 0.112; 20 mmol·L−1: 0.126, 0.141, and 0.156; 40 mmol·L−1: 0.141, 0.156 and 0.184 d−1) were positively and negatively correlated with the calculated total surface area (TSA) of solids, respectively. Degradation enhanced in the presence of HPCD, and the enhancing factor f was calculated (20 mmol·L−1: 15.16, 40.01, and 145.5; 40 mmol·L−1: 13.29, 37.97, and 138.4), indicating that the impact of solids was significant for the enhancement of biodegradation. 相似文献
Nitrogen removal of wetlands under 40 different inflow loadings were studied in the field during 15 months. The removal efficiency of four different sets of beds, namely the reed bed, the Zizania caduciflor bed, the mixing planting bed, and the control bed were studied. The outflow loading and total nitrogen (TN) removal rate of these beds under different inflow loadings and pollution loadings were investigated. The inflow loadings of 4 subsurface flow systems (SFS) ranged from 400 to 8000 mg·(m2·d)?1, while outflow loadings were less than 7000 mg·(m2·d)?1. The results showed that the inflow and outflow loading of TN removal rate in SFS presented an obvious linear relationship. The optical inflow loading to run the system was between 2000 to 4000 mg·(m2·d)?1. Average removal rate was between 1062 and 2007 mg·(m2·d)?1. SFS with plant had a better removal rate than the control. TN removal rates of the reed and Zizania caduciflora bed were 63% and 27% higher than the control bed, respectively. The results regarding the TN absorption of plants indicated that the absorption amount was very limited, less than 5% of the total removal. It proved that plants clearly increase TN removal rates by improving the water flow, and increasing the biomass, as well as activities of microorganisms around the roots. The research provided a perspective for understanding the TN removal mechanism and design for SFS. 相似文献