The influence of pH on cadmium toxicity to the green alga Stichococcus bacillaris and on the cadmium forms present in the culture medium

Cadmium toxicity to the green alga Stichococcus bacillaris was investigated in media of pH 3-9. A significant decrease of cadmium toxicity occurred in both the acidic and alkaline ranges of pH. In media of pH 3 and 9, cadmium did not affect the dry mass content substantially. Maximum toxicity of cadmium was noticed at pH 6-7. Voltametric investigations showed a significant effect of pH on electrochemically measured cadmium content in the culture media. Hydrolysis of the medium components and formation of cadmium complexes with OH(-) ions caused a considerable decrease in amounts of electrochemically measured cadmium in the alkaline range of pH.     

镉胁迫对向日葵幼苗生长和生理特性的影响

采用溶液培养方法,研究了不同浓度镉(0、0.05、0.1、0.5和1 mg/L)处理7 d对向日葵幼苗生长和生理特性的影响。结果表明：随着镉处理浓度的增加,向日葵幼苗对镉的吸收显著增加。1 mg/L镉浓度处理时,叶、茎和根中镉浓度分别为0.05 mg/L镉处理时的16.3、19.2和581倍;根中积累的镉含量明显高于叶和茎, 各浓度根部积累的镉分别为叶和茎的37.8～63倍和29.4～41倍。镉胁迫显著抑制向日葵幼苗生长和叶绿素合成,当镉浓度达1 mg/L时,整株植物生物量和总叶绿素含量分别为对照的55.9%和52.6%。镉胁迫下向日葵幼苗游离脯氨酸和丙二醛（MDA）含量显著增加,1 mg/L镉浓度时,根中含量分别为对照的4和5.8倍。向日葵幼苗可溶性蛋白含量和过氧化物酶(POD)活性变化与镉胁迫浓度呈明显的倒U字型关系,可溶性蛋白含量在0.05 mg/L镉浓度时达到最大值,叶、茎、根中的POD活性分别在0.1、0.1和0.05 mg/L镉浓度时达到最大值。     

Notes on the models of cadmium kinetics

This paper identifies several drawbacks in the models of absorption and desorption of cadmium presented by [Garcia-Gomez, C., Carbonell, G., 2004. Modelling the absorption and desorption of cadmium on paper pulp using kinetic approaches. Chemosphere 55, 869-878]. It then provides suggestions on improving the effectiveness of the model.     

Inactivation of cadmium in contaminated soils using synthetic zeolites

The addition of synthetic zeolite pellets to soils contaminated with cadmium significantly reduced the concentrations of cadmium in the roots and shoots of a range of crop plants. Use of synthetic foyazite group zeolites types 4A and 13X, at application rates of 1% by soil weight, caused reductions in cadmium concentrations of up to 86% in leaves of lettuce grown in pots, compared to controls with no added zeolites. The potential of these substances to reduce cadmium entry into the food chain, and as a clean up method, is noted.     

Sources and fates of lead and cadmium in municipal solid waste

Lead and cadmium enter the municipal solid waste stream as components of a variety of consumer products. Average empirical data from several resource recovery plants were analyzed to obtain an estimate of the source and fate of the subject elements. The total amounts of lead and cadmium found in municipal solid waste, determined from empirical data sources, were found to agree closely with those based on materials flow data. It was determined that most of the cadmium enters the waste stream in the combustible fraction and can account for a major share of the cadmium observed in fly ash and in atmospheric particulates. The most likely sources of cadmium are plastics and pigments. The lead emissions appeared to be derived from both combustible and noncombustible discards of batteries, plastics, and pigments. The data suggests that it would be useful to perform mass balance studies to provide primary data for the determination of the most effective methods for managing discards containing lead and cadmium. The purpose of the suggested research is the reduction of lead and cadmium emissions into the environment from resource recovery plants.     

Speciation and mobility of cadmium in straw and wood combustion fly ash

Two fly ashes from biomass combustion have been analysed regarding cadmium speciation and mobility. A fly ash from straw combustion contained 10 mg Cd/kg dry matter, and around 50% of the cadmium was leachable in water. The possible main speciation of cadmium in this fly ash was CdCl2. When adding this fly ash to agricultural soil a threat for groundwater contamination and plant uptake is existing. A fly ash from wood chip combustion had 28.6 mg Cd/kg dry matter. In this fly ash, the cadmium was bound more heavily, with only small amounts of cadmium leached in mild extractants. A possible speciation of cadmium in this fly ash was as oxide or as CdSiO3. Long-term effects and accumulation of cadmium could be a problem when adding this fly ash to agricultural or forest soils.     

硫化钠对土壤中铅镉的固定效果简

研究了硫化钠用于固定土壤中铅镉的可行性,考察了硫化钠用量及土壤pH、有机质对固定过程中土壤铅、镉赋存形态及固定效果的影响。结果表明,添加硫化钠可改变土壤中铅镉的形态分布,明显降低可交换态铅镉的含量。条件适当时,铅镉可交换态下降值分别为63%和73%。硫化钠在固定铅的过程中,固定效率对土壤pH、有机质含量的变化较为敏感,在有机质含量较低或酸性土壤中,硫化钠对铅固定效率较高;相对于铅,有机质含量和pH变化对镉的固定效率影响不是很大。     

Physiological mechanism of plant roots exposed to cadmium

Physiological experiments on plant roots exposed to cadmium were conducted on carrot and radish using a liquid culture and a pot experiment with a series of cadmium applications. Activities of four enzymes (catalase, peroxidase, polyphenol oxidase, superoxide dismutase), and concentrations of free proline and malonaldehyde in the roots of both plants were investigated. Results showed that the germination rate and growth of roots of both plants were inhibited at the concentration of 20 mg Cd/l, and the inhibition was increased with the increasing concentrations of cadmium, both in the liquid culture and in the pot experiment; activities of the four enzymes declined similarly in both species. The concentration of proline in roots reached the maximum when the application of cadmium was at the level of 20 mg/l in the liquid culture (or 20 mg/kg in soil), and then it declined slowly with the increasing concentration of cadmium. However, the reverse trend was observed for the concentration of malonaldehyde. All of bio-indicators measured here was quite sensitive to the addition of cadmium.     

萃取净化电镀含镉废水

研究了二壬基萘磺酸(DNNSA)形成的微乳液从模拟含镉废水中萃取镉离子的工艺条件。分别考察了相体积比(O/A)、萃取时间、温度及萃取剂浓度对废水中镉离子萃取的影响。结果表明,萃取平衡时间为10 mim,降低温度及增加萃取剂浓度均有利于萃取。紫外光谱证实当DNNSA萃取镉时,所形成萃合物对萘环的结构无影响,且不会破坏微乳相的结构;分子荧光光谱表明镉离子对配体DNNSA有荧光猝灭作用。     

Lead and cadmium in indoor air and the urban environment

The present study was conducted to find potential terrestrial biomonitors for heavy metals in indoor air in an urban environment. TSP, PM(10), and PM(2.5) were collected in three retirement facilities in the urban area of Vienna. In addition, particulate matter and soil, vegetation, and isopods (Porcellio scaber L.) were collected in the adjacent garden areas. Aerosols were sampled with a low-volume air sampler. The sampled materials were wet ashed and total lead and cadmium contents were determined. Water-soluble heavy metal concentrations were measured in aqueous extracts from air exposed filters, soil, and vegetation. Lead and cadmium were analyzed by graphite furnace AAS. Lead contents in the vegetation were inferred from water-soluble lead in soils. Lead in isopods generally reflected the contents in vegetation. Cadmium in plants probably derived from soil solutions as well as from atmospheric input. Isopods reflected the total cadmium contents in soils. Particulate matter was dominated by PM(2.5), both with respect to mass concentrations and to heavy metal contents. The indoor aerosol was found to be influenced by human activity, indoor sources, and outdoor particles. Relationships between indoor airborne heavy metals and the contents in vegetation (lead and cadmium: positive) and isopods (lead: negative) were identified to have the potential for biomonitoring indoor air quality.     

含镉的铬废水处理方法

对电镀镉工艺流程中出光、钝化及退镉进行了原理分析,得出上述工序必然会导致含镉的铬废水的产生。并提出了采用按铬废水处理后再通过添加重金属捕捉剂的方式,有效控制了电镀废水的处理质量,达到了标准的排放要求。     

Computational spectroscopic study of copper, cadmium, lead and zinc interactions in the environment

Molecular modelling has been used to investigate the interactions of various heavy metals, in order to understand and possibly to control the nature and behaviour of metals, especially in the aquatic environment. The interactions of copper, cadmium, lead and zinc with organic acids were studied using density functional theory (DFT) calculations. Carboxylic acid was used as a model molecule. The structure of each metal carboxylate was optimized and the vibrational spectrum calculated. The results indicate that there is a shift in the calculated v_S(C=O) of metal carboxylates compared with that of carboxylic acid. It was also found that hexaaqua structures of both cadmium and zinc are stable whereas those of copper and lead are not. Furthermore, dipole moment calculations indicate that cadmium carboxylate dihydrate is more representative of cadmium interactions in the aquatic environment. Moreover, hexaaquo cadmium could further interact with surrounding molecules in the aquatic environment.     

Medium composition affects the degree and pattern of cadmium inhibition of naphthalene biodegradation

Metals have been reported to inhibit organic pollutant biodegradation; however, widely varying degrees and patterns of inhibition have been reported. To investigate the roles of medium composition and metal bioavailability on these different degrees and patterns of inhibition, we assessed the impact of cadmium on naphthalene biodegradation by a newly isolated strain of Comamonas testosteroni in three chemically-defined minimal salts media (MSM): Tris-buffered MSM, PIPES-buffered MSM, and Bushnell-Haas medium. Cadmium (total concentrations of 100 and 500 microM) inhibited biodegradation in each medium. Degrees of inhibition were different in each medium. Cadmium was most inhibitory in PIPES-buffered MSM and least inhibitory in Bushnell-Haas. For example, in Bushnell-Haas medium, 100 microM cadmium reduced the cell yield more than 4-fold compared to controls not containing cadmium. The same concentration of cadmium completely inhibited growth in PIPES-buffered MSM. No difference in inhibition was observed in any medium when cadmium was added 24 h before inoculation rather than when added within one minute of inoculation. Two patterns of inhibition were observed. Inhibition occurred in a dose dependent pattern in Tris- and PIPES-buffered MSM and in a non-dose dependent pattern in Bushnell-Haas. Specifically, in Bushnell-Haas, 100 microM total cadmium extended the lag phase by 23+/-8.66 h, whereas 500 microM did not extend the lag phase. Soluble, ionic cadmium (Cd2+) concentrations were measured and modeled in each medium to assess cadmium bioavailability. In media containing 500 microM total cadmium, bioavailability was highest in Tris- and PIPES-buffered MSM and lowest in Bushnell-Haas. In Bushnell-Haas, cadmium bioavailability was initially higher in the 500 microM treatments (196+/-21.2 microM) than in the 100 microM treatments (78.2+/-2.04 microM); however, after 12 h, bioavailability was higher in the 100 microM treatments (56.4+/-24.8 micro) than the 500 microM treatments (13.3+/-1.2 microM). These data suggest that the type of medium determines the degrees and patterns by which metals inhibit biodegradation and emphasize the importance of coupling metal toxicity and bioavailability data.     

The influence of humic acids on the phytoextraction of cadmium from soil

Cadmium poses a major environmental and human health threat because of its constant release through anthropogenic activities. A need, therefore, exists for cost-effective remediation procedures. Phytoremediation, the use of plants to extract contaminants from soils and groundwater, has revealed great potential. However, it is limited by the fact that plants need time, nutrient supply and, moreover, have a limited metal uptake capacity. Synthetic chelators have shown positive effects in enhancing heavy metal extraction through phytoremediation, but they have also revealed a vast number of negative side-effects. The objective of this research was to investigate the use of humic acids as an alternative to synthetic chelators. Humic acids were applied to a cadmium-contaminated soil at various dosages, and the uptake of cadmium into Nicotiana tabacum SR-1 was determined in relation to the amounts of total and bioavailable cadmium in the soil. It was found that the theoretical bioavailability of cadmium, as determined by diethylenetriaminepentaacetic acid (DTPA) extraction, did not change, but its plant uptake was enhanced significantly, in some cases up to 65%. Humic acids added at a rate of 2 g kg(-1) soil increased the cadmium concentration in the shoots from 30.9 to 39.9 mg kg(-1). A possible reason for this enhancement is the decrease in pH, resulting in higher cadmium availability. Another possibility taken into account is that plants may take up cadmium complexes with humic acid fragments, which result from microbiological degradation or, self-dissociation.     

Effects of cadmium on sediment processing on members of the Capitella species-complex

The effect of cadmium on sediment processing by laboratory-cultured specimens of Capitella sp I and Capitella sp B was investigated. Specimens were exposed to 0, 60, 90 and 140 microg Cd g(-1) dry weight sediment for a 10 day period (two census days) to observe effects of cadmium on their feeding activity. Under unstressed conditions, Capitella sp I specimens were larger, had higher biomass and produced more fecal pellets than Capitella sp B. Cadmium concentrations had no effect on pellet production and body mass of the studied populations. However, cadmium exposure time significantly affected Capitella sp B pellet production and body mass of both populations following different trends: after 10 days of exposure, the average processed sediment per unit worm mass decreased in Capitella sp I but increased in Capitella sp B. The latter population did not reduce its feeding activity in the presence of cadmium maybe related to the fact that it is derived from a highly polluted environment. This study has shown an unimpaired response of Capitella sp I and Capitella sp B to cadmium in their sediment processing activity, which indicates the potential importance of this species complex in the trophic transfer of metals from sediments to other marine organisms.     

Dual-continuum analysis of a cadmium tracer field experiment

Cadmium penetration into a sandy-loam soil during the field ponded infiltration at Kralovska luka site in Southern Slovakia was observed in a controlled experiment. Adsorption of cadmium was examined using the radioactive tracer techniques in laboratory batch tests. Quite deep (115m)Cd penetration during the field experiment (65 cm beneath the soil surface) gives evidence of the particle-facilitated transport of cadmium through preferential pathways. More than 40% of the applied cadmium moved deeper than 10 cm. The field experiment was analyzed using both conventional single-continuum approach (based on Richards' equation for water flow and advection-dispersion equation for Cd transport) and dual-continuum approach. The latter approach allowed us to simulate more adequately the observed movement of cadmium.     

Desorption of copper and cadmium from soils enhanced by organic acids

The adsorption/desorption behavior of copper and cadmium on soils was investigated in this study. The adsorption isotherm of copper and cadmium conformed to Langmuir equation better than Freundlich equation. The effect of ionic strength, pH, and organic acid, including ethylenediamine tetraacetic disodium acid salt (EDTA), citric acid, oxalic acid and tartaric acid, on the desorption of copper and cadmium was studied. The desorption of copper and cadmium increased with the increase of ionic strength, while the desorption decreased with the rise of pH. The desorption of copper and cadmium enhanced by organic acids was influenced by pH. EDTA showed excellent enhancement on the desorption of both copper and cadmium; citric acid demonstrated great enhancement on the desorption of copper but negligible enhancement on the desorption of cadmium; oxalic acid enhanced the desorption of copper only at pH around 6.4 and enhanced the desorption of cadmium in the pH range from 6.4 to 10.7; tartaric acid slightly enhanced the desorption of copper but negligibly enhanced the desorption of cadmium. The desorption mechanism in the presence of organic acids were explained as the competition of complexation, adsorption and precipitation. The net effect determined the desorption efficiency. This study provided guidance for the selection of organic acids to enhance the electrokinetic (EK) remediation of copper and cadmium from contaminated soils.     

The effect of emissions of fertilizer production on the environment contamination by cadmium and arsenic in southern Brazil

The distribution of cadmium and arsenic in rainwater, surface soil and groundwater in a zone of influence of emissions of a phosphate fertilizer factory has been investigated. The analysis of rainwater along a wind line shows that cadmium in the soluble form precipitates close to emission source, whereas arsenic migrates further and also in the soluble form precipitates at a greater distance. The pH controls the distribution of cadmium and arsenic in rain and groundwater. Concentration of soluble cadmium along the impact line increases with reduction of pH and arsenic, contrary to the increase of pH. Concentrations of cadmium and arsenic in surface soil correlate well among themselves near to emission point. In a zone of confluence of emissions with sea air at a distance from the factory there is sedimentation of arsenic on a geochemical barrier and formation of a separate anomaly in soil.     

Uptake of cadmium by Stichococcus bacillaris

The uptake of cadmium by the green alga $\text{Stichococcus bacillaris}$ was studied. It was found that about 80% of the uptake was due to adsorption, and about 20% to energy-dependent transport. Investigations on the relationship between the sorption of cadmium and the equilibrium concentration (Ce) revealed that the alga cells are saturated at Ce20mg Cd/1.     

Accumulation of orally administered cadmium by the eel (Anguilla anguilla)

Eels were fed on gammarids (Amphipoda: Crustacea) containing high levels of cadmium for 30 days, then the cadmium distribution in the various organs of the fish was investigated. A retention value was calculated for liver + kidney and for whole-body.