首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
Polybrominated diphenyl ethers (PBDEs) are highly persistent anthropogenic contaminants found in trace amounts in many environmental compartments far from their source areas, posing a risk to aquatic ecosystems. Our objective was to determine the relative toxicities of three BDEs, BDE-47, BDE-99 and BDE-154 on marine phytoplankton algae Isochrysis galbana. For a highly sensitive endpoint: the 72-h inhibition of autotrophic growth rate was calculated according to standards methods. Actual PBDE concentration was measured by GC-MS and toxicity parameters were calculated on the basis of time-weighted mean actual concentrations. No observable effect concentration (NOEC) values were 2.53???g?L?1 for BDE-47, 3.48???g?L?1 for BDE-99 and 12.3???g?L?1 for BDE-154, and LOEC values were 5.06, 6.96 and 24.60???g?L?1 for BDE-47, BDE-99 and BDE-154, respectively. The calculated IC10 (the concentration inhibiting growth rate by 10?%) corresponded to 9.3, 12.78 and 54.6???g?L?1 for BDE-47, BDE-99 and BDE-154, respectively. The 50?% inhibitions of growth rate (IC50) values were: 25.7???g?L?1 BDE-47, 30.0???g?L?1 BDE-99 and 243.7???g?L?1 BDE-154. Therefore, the acute toxicity of PBDEs decreases as the degree of bromination increases, the order of toxicity is BDE-47?>?BDE-99?>?BDE-154. Significant (p?<?0.05) adverse effects were observed for all compounds at concentrations >15???g?L?1. Our results indicated that under laboratory conditions PBDEs inhibited the growth of marine phytoplankton at concentrations near 10???g?L?1. However, further work is required to investigate long-term effects in these and other aquatic organisms.  相似文献   

2.
The aquatic vascular plant (Ceratophyllum demersum L.) was investigated as a potential biological filter for removal of Cd from wastewaters. Plants were grown in and harvested weekly from 0.10 M Hoagland nutrient solutions containing concentrations of Cd from 0.01 to 1.03 μg Cd mL?1. Tissue Cd was positively correlated to increased concentrations of Cd in solution. Concentration factors (CFs) of Cd in plants after one week were 13.3 for the 0.01 μg Cd mL?1 treatment; 451.4 for plants treated with 0.04 μg Cd mL?1, and 506.5 for plants treated with 1.03 μg Cd mL?1. Plants treated with 0.01 μg Cd mL?1 sustained tissue Cd concentrations almost 9-fold over those at week 1. However, after 5 weeks tissue Cd concentration in plants exposed to 1.03 μg Cd mL?1 had decreased 97% compared to the week 1 concentration. Growth measurements of dry weight, stem lengths, and lateral shoot growth were nagatively correlated to increased Cd treatments. Our results suggest that Coontail exposed to very low Cd concentrations (0.01 μg Cd mL?1) can take up and accumulate Cd. However, plants exposed to Cd at 0.04 μg Cd mL?1 or above did not accumulate Cd past one week.  相似文献   

3.
The petroleum industry activities provide potential risks to the environment because they can contaminate ecosystems with different organic compounds in the production chain. Several accidents with transport and handling of petroleum and related products occurred in urban areas with harmful effects to the quality of life and economy. In the 1990s, bioremediation and phytoremediation technologies as economically feasible alternatives to repair the environmental damage were developed. In this study, the potential of the willows Salix rubens and Salix triandra were evaluated with regard to the phytoremediation of soils contaminated with petroleum-derived hydrocarbons (total hydrocarbons and polycyclic aromatic hydrocarbons (PAHs)). The PAHs were quantified by extraction from soils and plants using dichloromethane under ultrasonication. The HPLC analysis was performed with GC/MSD equipment. The total hydrocarbons present in uncontaminated soil were quantified by the sum of animal/vegetable oils and greases and mineral oils and greases according to Standard Methods 5520 (1997). The two willows species S. rubens and S. triandra were resistant during the project development. In the contaminated soil, in which both species were planted, the total hydrocarbons concentration was reduced near 98?%. The PAHs content was remarkably reduced as well. Pyrene showed an initial concentration of 23.06???g?kg?1, decreasing in most cases to 0.1???g?kg?1 or to undetectable levels. Chrysene decreased from 126.27???g?kg?1 to undetectable levels. Benzo[k]fluoranthene and benzo[a]pyrene concentrations had also showed a decrease from 28.44 and 3.82???g?kg?1, respectively, to undetectable levels.  相似文献   

4.
To have a better understanding of the industrial organic contamination of the city of Khabarovsk, southern Russian Far East, snow cover of the winter seasons of 2009?C2010 and 2010?C2011 was sampled at the end of March of 2010 and 2011 at six sites (and at eight sites in 2011) of the urban area and on the adjacent snow cover of the Amur River. The samples were analyzed by high-performance liquid chromatography and gas chromatography/mass spectrometry techniques for petroleum products and phenols. The main groups of the detected pollutants were n-alkanes, isoalkanes, paraffins, phenols, and phthalates. The total concentration of the petroleum products was 0.08?C2.84?mg/L, volatile phenols 0.17?C3.61???g/L. 4-Nitrophenol has been found among the phenols (0.22?C1.65???g/L). The minimum toxicant concentrations were found in background sites (first hundred meters) off the urban highways, and the maximum, in dumps of snow from the urban highways and the vicinities of Heat Power-3. Of aromatic compounds, insignificant amounts of isopropylbenzene (0.5???g/L) and xylenes (0.2?C0.3???g/L) and a high content of ethylbenzene (1.3???g/L) originated from local emission were found. For the unpolluted sites, identification of n-alkanes revealed high-molecular paraffins C26?CC33 (50?% of the total n-alkane content); fractions in the range of C19?CC21 and C24 were found for the snow dumps, 55.0?% and 90.0?% of the total alkane content in 2010 and 2011, correspondingly. These compounds originated most probably from the wasted diesel fuel and mineral greases (derivatives). The study indicated the dangerous level of the Khabarovsk urban atmosphere deterioration with a range of organic pollutants of transport and industrial origin. The snow (and rain) urban runoff may affect the local soil and water ecosystems subsequently.  相似文献   

5.
We examined the effects of an amended mixture of three pesticides, atrazine (72.7?g), S-metolachlor (54.5?g), and permethrin (both cis and trans isomers; 11.4?g), on 10-day sediment toxicity to Hyalella azteca in a managed natural backwater wetland after a simulated agricultural runoff event. Sediment samples were collected at 10, 40, 100, 300, and 500?m from inflow 13?days prior to amendment and 1, 5, 12, 22, and 36?days post-amendment. Background pesticide concentrations ranged from <1 to 977, <1 to 119, and <1 to 2???g?kg?1, for atrazine, S-metolachlor, and permethrin, respectively. Average post-amendment atrazine and S-metolachlor were 2,915?C3,927 and 3?C20???g?kg?1, respectively at 10?C40?m and 538?C872 and <1???g?kg?1, respectively at 300?C500?m. Average post-amendment permethrin was 65?C200???g?kg?1 at 10?C40?m and 1?C10???g?kg?1 at 300?C500?m. H. azteca 10-day survival varied spatially and temporally up to 100?m from inflow. Animal growth, independent of survival, was reduced 40 and 100?m from inflow on day?36, showing continued sediment toxicity of up to 100?m from inflow more than 1?month after amendment. Animal survival and growth were unaffected at 300 and 500?m from inflow throughout the study period. Correlations of pesticide concentrations and H. azteca responses indicated that observed sediment toxicity was primarily from permethrin with potential additional synergistic toxicity from atrazine and methyl parathion. Study results indicate that natural backwater wetlands can be managed to ameliorate pesticide mixture 10-day sediment toxicity to H. azteca within 300?m of inflow and smaller wetlands (??100?m) may require several months of effluent retention to mitigate effects.  相似文献   

6.
In order to study the potential use of microfauna as an indicator of effluent quality and operational parameters in an activated sludge system for treating piggery wastewater, an experimental sequencing batch reactor was set up and evaluated by biological and physical–chemical analyses for 12 months. Results show that microfauna (and specifically ciliate protozoa) are a good parameter for assessing effluent quality in terms of both chemical oxygen demand (COD) and ammonia and for assessing the organic and nitrogen load of the system. Specifically, the abundance of ciliates decreases from 20,000 individuals·mL?1 to ca. 2,500 individuals·mL?1 and from ca. 10,000 individuals mL?1 to ca. 200 individuals mL?1 when effluent concentration is between 550 and 750 mg L?1 and above 100 mg L?1 to the COD and ammonia concentrations, respectively. Furthermore, microfauna abundance is reduced from ca. 18,000 individuals mL?1 (organic load between 0.1 and 0.2 mg COD mg total suspended solids (TSS)?1 day?1) to ca. 500 individuals mL?1 (organic load between 0.3 and 04 mg COD mg TSS?1 day?1). Microfauna abundance also decreases as nitrogen loading increases. Nitrogen loading in the range of 5–60 mg NH4–N g TSS?1 day?1 does not have any significant effect on microfauna abundance. However, ammonia loading from 60 to 120 mg NH4–N g TSS?1 day?1 reduces microfauna abundance ca. 6-fold. Ciliate protozoa were the largest microfauna group during the whole period of study, representing ca. 75% of the total microfauna abundance. The largest group in the ciliate community was that of the free-swimming ciliates. This was followed by the group of attached and crawling ciliates. Specifically, the dominant ciliate species during the whole study period were Uronema nigricans, Vorticella microstoma-complex, Epistylis coronata, and Acineria uncinata.  相似文献   

7.
We determined normal plasma butyrylcholinesterase (BChE), carboxylesterase (CbE using ??-NA substrate), and glutathione S-transferase (GST) activities in Caiman latirostris and Phrynops hilarii to obtain reference values for organophosphorus (OP) pesticide monitoring. BChE and CbE sensitivity to malaoxon was also evaluated. C. latirostris (N?=?12; six males and six females) and P. hilarii (N?=?12; seven males and five females) were obtained from the programs Yacaré (Entre Ríos Province, Argentina) and Zoo of Córdoba (Córdoba Province, Argentina). Mean total (female and male) plasma BChE activity was significantly different between reptile species, ranging between 0.337?±?0.085???mol?min?1?ml?1 of plasma for C. latirostris and 0.251?±?0.070???mol?min?1?ml?1 of plasma for P. hilarii. However, plasma CbE (??-NA) and GST activities were significantly higher in P. hilarii (4.81?±?1.00 and 0.145?±?0.045???mol?min?1?ml?1 of plasma, respectively) than in C. latirostris (0.57?±?0.20 and 0.059?±?0.013???mol?min?1?ml?1 of plasma, respectively). No significant differences in B-esterase and GST activities were detected between sexes, except CbE (??-NA) for C. latirostris. IC50 values for BChE and CbE (??-NA) suggested different sensitivity levels between species and between sexes. The results demonstrate that plasma esterase activity varied between species, but not between sexes (except CbE for C. latirostris). The in vitro inhibition tests indicated that CbE (??-NA) is more sensitive to inhibition than BChE. C. latirostris may be the reptile species most vulnerable to field pesticide exposure because this reptile presents the lowest CbE activity levels and its B-esterase levels seem more sensitive to OP.  相似文献   

8.
This paper describes the use of dry free hanging filters, as passive samplers to determine ozone in the ambient air. The filters, with a diameter of 25?mm, were impregnated with 5,5??-disodium indigo disulphonate (IDS), a reagent for ozone. From the amount of reacted indigo compound, found on the filter, and the ozone concentration in the ambient air, a pseudo rate constant k 1, of the reaction between ozone (O3) and IDS on the filter, is calculated. The range of measurement is between 9 and 205???g/m3 ambient ozone. The dry filter method is specific for ozone, while the Dutch standard method NEN2789, based on an aqueous solution of IDS, has to be corrected for the presence of NO x . From wind tunnel and field experiments, k 1 proved to vary between 0.7 and 1.5?×?10?6?m3?s?1 (??g O3)?1 at wind velocities between 1 and 3?m/s and at an exposure time of 60?min. Within these conditions, ozone concentrations have been determined with free hanging filters in four busy streets in Yogyakarta, Indonesia and at two background sites using an average value of k 1 of 1.2?×?10?6. Subsequently, the traffic NO emission was estimated from the difference of the O3 concentrations at both sides of a road. For an arbitrary situation, an NO emission of 255???g/s per metre road length was calculated. The filter method is inexpensive and practical, needs no electricity, is easily assembled and can be used to perform measurements in remote areas. It is shown here that this simple measurement technique may support air quality studies, e.g., in developing countries.  相似文献   

9.
The aquatic vascular plant Eurasian watermilfoil (Myriophyllum spicatum L.) was investigated for its potential to take up Cd from nutrient-rich water in a short-term growth and harvest regime. Eurasian watermilfoil plants were grown in and harvested weekly from 0.10M Hoagland nutrient solutions containing concentrations of Cd from 0.04 to 7.63μg Cd mL?1. Dry weights of plants significantly decreas4ed when exposed to 7.63μg Cd mL?1. For both 0.04 and 1.03μg Cd mL?1 treatment the greatest concentration of Cd in plants occurred during the first two weeks. The greatest Cd concentration of Cd in plants for the 7.63μg Cd ML?1 treatment occurred during week one and decreased through week 2. Tissue P concentration in control plants increased over time but did not increase significantly over time when plants were exposed to 0.04 and 1.03μg Cd mL?1 levels. Tissue P concentration decreased over time when plants were exposed to 7.63μg Cd mL?1. Stem length, root dry weights, and root number significantly increased over time in control plants and in those exposed to the 0.04 and 1.03μg Cd mL?1 treatments. Plants treated with 7.63μg Cd mL?1 did not grow. These results suggest that Eurasian watermilfoil would be useful for absorbing Cd from nutrient-rich water when the solution concentration was in the range of 0.04 to 7.63μg Cd mL?1. However, in solutions having the highest concentration of Cd, the harvest regime would have to sustain plant vigor, avoid tissue Cd loss, and realize maximum uptake of Cd from solution.  相似文献   

10.
The effects of four concentrations (0.5, 1, 5 and 10 μg mL?1) of the heavy metals Hg, As, Pb, Cu, Cd, and Cr on some senescence variables of Cuscuta reflexa Roxb. were studied. All of the treatments, except 0.5 μg mL?1, decreased Hill reaction activity, chlorophyll and protein contents and dry matter percentage in biomass and increased tissue permeability over control data. The harmful effects of the metals were best visible at 10 μg mL?1. The general order of sensitivity was As > Cd > Pb > Hg > Cu > Cr (absolute metal concentration). The data suggest that Cuscuta reflexa shows tolerance to the heavy metals tested up to 0.5 μg mL?1.  相似文献   

11.
High As groundwater normally contained high concentrations of Cl? and HCO 3 ? . This study examined the effects of Cl?, HCO 3 ? , and As species on As uptake by hyperaccumulator Pteris vittata. Plants were exposed hydroponically to 5.0?mg/L As(III) or As(V) in the presence of 0, 0.5, 1, 2, 5, 10, and 20?mM of Cl? or HCO 3 ? for 10?days. Addition of high Cl? concentrations (>10?mM) slightly inhibited P. vittata growth (biomass), while generally had no significant effect on plant As uptake. High solution pH resulted in reduced plant growth and As uptake, which attributed to the inhibitory effects in HCO 3 ? treatments with the high pH of the high HCO 3 ? concentration. It was speculated that addition of HCO 3 ? (<20?mM) would have no significant effect on plant growth and As uptake. The inhibitory effect of HCO 3 ? on As translocation was less apparent in the As(III) solutions than the As(V) solutions. For the high As groundwater with As(III) as the predominant species, high pH, instead of high concentrations HCO 3 ? and Cl?, was expected to inhibit As uptake. The results suggested that optimum plant growth and maximum As hyperaccumulation could be achieved by adjusting solution pH in the growth media (around 7.2).  相似文献   

12.
The selection of control measures for reducing metal contamination in rivers has targeted point sources such as wastewater treatment plants (WWTPs) and industrial discharges without a proper evaluation of their relative contribution to metal loads at the catchment level. The necessity of controlling pollutant inputs in a sound and cost-effective way to prevent the deterioration of chemical and ecological quality of receiving waters has highlighted the need for appropriate source assessment. As metals in rivers emanate from a wide range of sources, it is necessary to understand their relative contribution in order to reduce effectively the concentrations in receiving waters. This study presents a simple method for calculating the relative contribution of WWTPs to levels of metals in receiving waters as applied to the Aire?CCalder catchment in the UK. In this catchment, the apportionments to WWTP effluents of metal levels in rivers were 37, 31, 36 and 60?% of total cadmium (Cd), lead (Pb), mercury (Hg) and nickel (Ni), respectively. Spatial metal distribution in rivers with maximum concentrations of 0.47???g?L?1 for Cd, 8.54???g?L?1 for Pb, 0.05???g?L?1 for Hg and 10.17???g?L?1 for Ni caused by the discharge of WWTP effluents was estimated. The findings demonstrate that the proposed approach using quantification of metal loads and estimation of concentrations in receiving waters could adequately calculate the relative contribution of WWTP effluents to metal levels in receiving waters. Applications to various river catchments using site-specific data would further validate the effectiveness of the approach proposed.  相似文献   

13.

Purpose

Many drainage basins are terminal recipients of hydrophobic contaminants such as pesticides. To minimize adverse effects of the contaminated sediments on wildlife, it is important to understand sediment contamination patterns. This study was conducted at the Salton Sea, which is a heavily polluted large lake in southern California, USA, with the purpose to identify areas with minimal contamination so as to support species conservation.

Materials and methods

We investigated the horizontal and vertical distribution of 14 organochlorine pesticides (OCPs) and 12 currently used pesticides (CUPs) in playas at locations near the drainage outfalls. The data were subjected to spatial analysis using Kriging interpolation and converted to contour maps. Statistical comparisons were made among different areas, between different sediment depths, and between air-exposed and submerged sediments.

Results and discussion

Various OCPs were found near two drainage inlets, with mean concentrations of 6?C30???g?kg?1 in air-exposed sediments and 3?C18???g?kg?1 in submerged sediments. Chlordane (detected frequency, DF?=?77?%) and DDT derivatives (DF?=?100?%) were among the most frequently detected OCP. Significantly higher concentrations were found in air-exposed sediments than in submerged sediments, and in subsurface sediments than in surface sediments (P?<?0.01), suggesting historical deposition and burial. Sediments at many locations exceeded the threshold levels for DDE. A total of seven CUPs were detected with the maximum ??CUPs concentration of up to 27???g?kg?1. Bifenthrin was the dominant CUP contaminant, representing more than 60?% of ??CUPs for most samples with the highest concentration of 26???g?kg?1.

Conclusions

Findings from this study provide a snapshot of the spatial distribution in both horizontal and vertical directions of hydrophobic pesticides in a drainage-dominated lake, and such information and the method of investigation may be used for identifying areas of minimal contamination as alternative habitats for this and other impacted lakes.  相似文献   

14.
The aim of this study is to assess the premature mortality risks caused by exposure to particulate matter with aerodynamic diameter less than 2.5???m (PM2.5) and ozone elevated concentrations for the years?2000, 2005, and 2020 in East Asia. The spatial distributions and temporal variations of PM2.5 and ozone concentrations are simulated using the Models-3 Community Multiscale Air Quality Modeling System coupled with the Regional Emission Inventory in Asia. The premature mortality risks caused by exposure to PM2.5 and ozone are calculated based on a relative risk (RR) value of 1.04 (95?% confidence interval (CI): 1.01?C1.08) for PM2.5 concentrations above the annual mean limit of 10???g?m?3 taken from the World Health Organization?CAir Quality Guideline and based on a RR value of 1.003 (95?% CI: 1.001?C1.004) for ozone concentration above 35?ppb of the SOMO35 index (the sum of ozone daily maximum 8-h mean concentrations above 35?ppb). We demonstrate one of the implications of the policy making in the area of environmental atmospheric management in East Asia by highlighting the annual premature mortalities associated with exposure to PM2.5 concentrations that just meet an annual mean concentration of 10???g?m?3, as well as ozone concentrations that have a daily zero SOMO35 index in vulnerable places. Our results point to a growing health risk that may endanger human life in East Asia. We find that the effect of PM2.5 on human health is greater than the effect of ozone for the age group of 30?years and above. We estimate the corresponding premature mortality due to the effects of both ozone and PM2.5 in East Asia for the years?2000 and 2005 to be around 316,000 and 520,000 cases, respectively. For future scenarios of the year?2020, policy succeed case, reference, and policy failed case, the estimated annual premature mortality rates are 451,000, 649,000, and 1,035,000 respectively.  相似文献   

15.
Laboratory experiments were carried out to study the uptake kinetics of selected metals and metalloids in the aquatic moss Fontinalis antipyretica. For this purpose, moss specimens from a clean site were exposed to concentrations of As, Hg, Sb, and Se ranging from 0.1 to 10,000???g?l?1, for incubation times of between 1 and 22?days, and the tissue concentrations of the metals in the moss specimens were then measured. Uptake kinetics followed different patterns in relation to exposure time, although the most common was Michaelis?CMenten kinetics. On the contrary, the contamination factors followed very similar patterns in relation to the exposure concentrations in all cases, with a good fit to logarithmic equations. The bioconcentration factors tended to decrease as exposure concentration increased. The bioconcentration factors for Hg were extremely high, even at the lowest concentration in water and for the shortest incubation time, which implies that F. antipyretica has a high capacity to magnify Hg levels in water, which is an important characteristic in a good biomonitor. According to the time to reach equilibrium, the minimum exposure time recommended for use in active biomonitoring by means of transplants is very variable, although high levels of the elements, except Sb, were found in the moss tissues within a few days. We do not recommend the use of this moss species to biomonitor low concentrations of Sb in water. The differences in maximum contamination factors and lowest bioconcentration factors suggest that As and Se were the most toxic of the elements under study.  相似文献   

16.
A chromated-copper-arsenate (CCA) wood preservative was tested for toxic effects on the growth of a bacterial culture (Flavobactenum sp. ATCC 53874) capable of biodegrading pentachlorophenol, another wood preservation chemical. Both a commercially available CCA preparation and a laboratory-prepared CCA solution were tested. Each had an inhibitory effect on the growth of Flavobacterium at diluted CCA levels as low as 1.0×10?4 to 1.0×10?5% wt vol?1. The commercial formulation was generally more toxic. EC50 values calculated after 96 hr of incubation were 1.2 ×10?4% wt vol?1 for the commercial material (containing 0.15/0.097/0.14 μg mL?1 of Cr/Cu/As, respectively) and 3.8×10?4% for the laboratory solution (containing 0.51/0.31/0.49 μg mL?1 of Cr/Cu/As, respectively). CCA toxicity increased during the first 7 to 8 days and then slowly decreased for the balance of the 21 day incubation period. Biodegradation of pentachlorophenol residues in contaminated soil will be negatively affected by the presence of CCA as a co-contaminant.  相似文献   

17.
High phosphorus (P) in surface drainage water from agricultural and urban runoff is the main cause of eutrophication within aquatic systems in South Florida, including the Everglades. While primary sources of P in drainage canals in the Everglades Agricultural Area (EAA) are from land use application of agricultural chemicals and oxidation of the organic soils, internal sources from canal sediments can also affect overall P status in the water column. In this paper, we evaluate P release and equilibrium dynamics from three conveyance canals within the EAA. Incubation and flux experiments were conducted on intact sediment cores collected from four locations within the Miami, West Palm Beach (WPB), and Ocean canal. After three continuous exchanges, Miami canal sediments reported the highest P release (66?±?37 mg m?2) compared to WPB (13?±?10 mg m?2) and Ocean (17?±?11 mg m?2) canal over 84 days. Overall, the P flux from all three canal sediments was highest during the first exchange. Miami canal sediments showed the highest P flux (2.4?±?1.3 mg m?2 day?1) compared to WPB (0.83?±?0.39 mg m?2?d?1) and Ocean canal sediments (0.98?±?0.38 mg m?2 day?1). Low P release from WPB canal sediments despite having high TP content could be due to carbonate layers distributed throughout the sediment column inhibiting P release. Equilibrium P concentrations estimated from the sediment core experiment corresponded to 0.12?±?0.04 mg L?1, 0.06?±?0.03 mg L?1, and 0.08?±?0.03 mg L?1 for Miami, WPB, and Ocean canal sediments, respectively, indicating Miami canal sediments behave as a source of P, while Ocean and WPB canal sediments are in equilibrium with the water column. Overall, the sediments showed a significant positive correlation between P release and total P (r?=?0.42), Feox (r?=?0.65), and Alox (r?=?0.64) content of sediments. The contribution of P from the three main canals sediments within the EAA boundary corresponded to a very small portion of the total P load exiting the EAA. These estimates, however, only take into consideration diffusive fluxes from sediments and no other factors such as canal flow, bioturbation, resuspension, and anaerobic conditions.  相似文献   

18.
Carbonic anhydrase (CA) has been immobilized on chitosan stabilized iron nanoparticles (CSIN) for the biomimetic carbonation reaction. CSIN was characterized using scanning electron microscope, energy dispersive X-ray, X-ray diffraction spectroscopy, and Fourier transform infrared analysis. The effect of various parameters such as pH, temperature and storage stability, on immobilized CA was investigated using a p-NPA assay. Kinetic parameters of immobilized and free CA (K m and V max values) were also evaluated. The K m and V max for immobilized CA was 1.727?mM and 1.189???mol?min?1?ml?1, respectively, whereas for free enzyme the K m and V max was 1.594?mM and 1.307???mol?min?1?ml?1, respectively. It was observed that the immobilized enzyme had longer storage stability and retained 50?% of its initial activity upto 30?days at room temperature. CA immobilized on CSIN has been used for hydration of CO2, and the results were validated by using a gas chromatographic method. Proof of concept has been established for the biomimetic carbonation reaction. Immobilized CA show reasonably good CO2 sequestration capacity of 21.55?mg of CaCO3/mg of CA as compared to CO2 sequestration capacity of 34.92?mg of CaCO3/mg of CA for free CA respectively, under a limiting concentration of CO2 (14.5?mg of CO2/10?ml).  相似文献   

19.
Current non-invasive biomonitoring techniques to measure heavy metal exposure in free ranging birds using eggs, feathers and guano are problematic because essential metals copper (Cu) and zinc (Zn) deposited in eggs and feathers are under physiological control, feathers accumulate metals from surface contamination and guano may contain faecal metals of mixed bioavailability. This paper reports a new technique of measuring lead (Pb), Cu and Zn in avian urate spheres (AUS), the solid component of avian urine. These metal levels in AUS (theoretically representing the level of metal taken into the bloodstream, i.e. bioavailable to birds) were compared with levels in eggs (yolk and shell), feathers and whole guano from chickens (Gallus gallus domesticus) exposed to a heavy metal-contaminated soil (an allotment soil containing Pb 555?mg?kg?1 dry mass (dm), Cu 273?mg?kg?1?dm and Zn 827?mg?kg?1?dm). The median metal levels (n?=?2) in AUS from chickens exposed to this contaminated soil were Pb 208???g?g?1 uric acid, Cu 66???g?g?1 uric acid and Zn: 526???g?g?1 uric acid. Lead concentrations in egg yolk and shell samples (n?=?3) were below the limit of detection (<2?mg?kg?1), while Cu and Zn were only consistently detected in the yolk, with median values of 3 and 70?mg?kg?1 (dm), respectively, restricting the usefulness of eggs as a biomonitor. Feathers (n?=?4) had median Pb, Cu and Zn levels respectively of 15, 10 and 140?mg?kg?1 (dm), while whole guano samples (n?=?6) were 140, 70 and 230?mg?kg?1 (dm). Control samples were collected from another chicken flock; however, because they had no access to soil and their diet was significantly higher in Cu and Zn, no meaningful comparison was possible. Six months after site remediation, by top soil replacement, the exposed chickens had median Pb, Cu and Zn levels respectively in whole guano (n?=?6) of 30, 20 and 103?mg?kg?1 (dm) and in AUS (n?=?4) of 147, 16 and 85???g?g?1 uric acid. We suggest the persistent high Pb level in AUS was a consequence of bone mobilised for egg production, releasing chronically sequestered Pb deposits into the bloodstream. In contrast, AUS levels of Cu and Zn (metals under homeostatic control and sparingly stored) had declined, reflecting the lower current exposure. However because pre- and post-remediation samples were measured using different methods carried out at different laboratories, such comparisons should be guarded. The present study showed that metals can be measured in AUS, but no assessment could be made of availability or uptake to the birds because tissue and blood samples were not concomitantly analysed. A major short coming of the study was the inappropriate control group, having no access to uncontaminated soil and being fed a different diet to the exposed birds. Furthermore guano and urine analysis should have been carried out on samples from individual birds, so biological (rather than just technical) variation of metal levels could have been determined. Future studies into using AUS for biomonitoring environmental heavy metals must resolve such experimental design issues.  相似文献   

20.
Among the many anthropogenic abiotic stresses, manganese (Mn) toxicity has been recognized for its impact on aquatic ecosystems as well as on the biological components of these ecosystems, including aquatic plants. The objective of this study was to determine the Mn accumulation ability of aquatic macrophytes (Azolla caroliniana, Salvinia minima and Spirodela polyrhiza) and evaluate the morphophysiological responses of the species that gather the highest amount of Mn when exposed to a supra-optimal supply of manganese. The experiments were conducted in the laboratory, and the effects of Mn were evaluated based on plant growth; the concentration of total chlorophyll, carotenoids, and anthocyanins; the enzymatic activity of catalase and peroxidase; and leaf anatomy. All of the studied species accumulated Mn in their tissues. Moreover, it was observed that this accumulation was dependent on the concentration of the metal in solution. S. polyrhiza showed higher concentrations of Mn in its tissues (17.062?mg?g?1 dry weight (DW)), followed by S. minima (4.283?mg?g?1 DW) and A. caroliniana (1.341?mg?g?1 DW). Despite the Mn accumulation in all species, S. polyrhiza was the only one selected for further analyses because of its greater ability to accumulate Mn. The high Mn concentration found in tissues of S. polyrhiza suggests that this species has the potential to sequester and accumulate this metal. However, a sensitive response in the plants exposed to higher Mn concentrations (0.4?mM) was observed. The phytotoxicity effects of this accumulation were responsible for a decrease in the plant growth, a reduction in the pigment content (total chlorophyll, carotenoids, and anthocyanins), a low activity of catalase, and the disarrangement of the leaf aerenchyma.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号