A laboratory study of bacteria-facilitated cadmium transport in alluvial gravel aquifer media

Colloids, including bacteria, can dramatically accelerate the transport of heavy metals in ground water. Batch and column experiments were conducted to investigate adsorption of cadmium (Cd) onto Bacillus subtilis spores or Escherichia coli vegetative cells and Cd transport in alluvial gravel aquifer media in the presence of these bacteria. Results of the batch experiments showed that adsorption of Cd onto the bacteria was (i) positively related to solution pH, bacterial concentration, and negative surface charge, but inversely related to Cd concentration and (ii) a rate-limited nonlinear process, but adsorption onto E. coli was much less. For column influent Cd concentrations of about 4 mg/L and bacterial concentrations of > or = 10(5) colony-forming units (cfu)/mL, there was a significant increase in total Cd effluent concentrations. In comparison with controls that did not have bacteria-facilitated transport, Cd traveled 17 to 20 times faster when it traveled with mobile bacteria. However, Cd traveled mostly 2 to 3 times slower during the desorption phase under the influence of bacteria retained in the column. The difference between total and dissolved Cd concentrations was significant during Cd cotransport with B. subtilis spores, but this concentration difference was very small during Cd cotransport with E. coli, suggesting an adsorption-dominant mechanism during Cd cotransport with the spores and the possibility of Cd chelation by the dissolved membrane vesicles secreted from E. coli cell walls. Bacteria-facilitated transport of heavy metals may pose a threat to ground water quality in sites such as landfills and following land disposal of industrial and domestic effluent and sludge.     

Environmental assessment of packaging: The consumer point of view

When marketing environmentally responsible packaged products, the producer is confronted with consumer beliefs concerning the environmental friendliness of packaging materials. When making environmentally conscious packaging decisions, these consumer beliefs should be taken into account alongside the technical guidelines. Dutch consumer perceptions of the environmental friendliness of packaged products are reported and compared with the results of a life-cycle analysis assessment. It is shown that consumers judge environmental friendliness mainly from material and returnability. Furthermore, the consumer perception of the environmental friendliness of packaging material is based on the postconsumption waste, whereas the environmental effects of production are ignored. From the consumer beliefs concerning environmental friendliness implications are deduced for packaging policy and for environmental policy.     

RUNOFF,EROSION, AND SOLUTES IN THE LOWER TRUCKEE RIVER,NEVADA, DURING 19691

The Truckee River heads in the Sierra Nevada at Lake Tahoe, and terminates in Pyramid Lake. During the 1969 water year, flow about 9 miles upstream from the mouth (974,000 acre-ft) was almost four times the long-term average, due mainly to heavy winter rains and spring snowmelt. A short period of low-altitude rainfall produced the highest concentrations of suspended sediment, whereas a much longer subsequent period of snowmelt yielded a much greater total quantity of material. The upper 90 percent of the basin yielded about 260 acre-feet (630,000 tons) of sediment at the Nixon gage, whereas an estimated 2,800 acre-feet (6.8 million tons) was contributed by erosion of about 200 acres of river bank below the gage. Solute content at the gage ranged from 80 to 450 mg/l, dominated by calcium, sodium, and bicarbonate, plus silica in the most dilute snowmelt and chloride in the most concentrated low flows. Solute load totaled about 130,000 tons, of which the principal constituents in Pyramid Lake-sodium plus equivalent bicarbonate and chloride-amounted to almost 40,000 tons. The total solute load during a year of average flow may be 45,000-55,000 tons, including 18,000-22,000 tons of principal lake constituents.     

Movement of pertechnetate through soils: Hydrodynamic dispersion

Measurement of the hydrodynamic dispersion of pertechnetate (⁹⁹TcO^?₄) migrating towards the water-table complements other investigations of the partition of pertechnetate between soil solution and soil colloids. This study was performed on soil columns equilibrated with distilled water and through which a solution of ⁹⁹TcO₄NH₄ or ³⁶ClNa was percolated at constant rate. A theoretical elution curve was adjusted to the experimental points obtained from a sand column. An estimate could thus be made of the parameters characterizing the migration of pertechnetate. The model used here considered the presence of a ‘dead water’ zone in the column into which the solute penetrates by molecular diffusion only at a given rate. The elution curves obtained experimentally and theoretically have been compared with those for a non-reactive anion, ³⁶Cl^?. A simulationof the change of pertechnetate concentration in the eluate has been made for increasing values of the retention factor. The calculated curves confirm the very low mobility of this anion in soil.     

Effects of Lime and Ash Treatments on DOC Fractions and Low Molecular Weight Organic Acids in Soil Solutions of Acidified Podzolic Soils

Dissolved organic carbon (DOC) fractions and different low molecular weight organic acids (LMWOAs) were determined in soil solutions from two lime or ash treated Norway spruce sites in the south of Sweden. At Hasslöv, 3.45 t ha^-1 or 8.75 t ha^-1 dolomite were applied 15 years before sampling. Horröd was treated with 4.28 t ha^-1 ash and 3.25 t ha^-1 dolomite and sampled four years later. Propionate (7–268 M) and malonate (2–34 M) were the LMWOAsfound in the highest concentrations at Hasslöv. Two other LMWOAs dominated at Horröd, namely citrate (18–64 M)and fumarate (5–31 M). The differences in concentration of most of the determined LMWOAs at Hasslöv were significantly increased due to treatment. The LMWOAs comprised between 1.1–6.3% of the DOC at Hasslöv and 4.5–17.6% at Horröd. At Hasslöv normally 3–10% of the total acidity (TA) was due to LMWOAs and the average specific buffer capacity was 74 ± 22 mmol mol^-1C.The total DOC concentration in the mor layer solution was 16 mM for the dolomite treated plots compared to 10 mM at the untreated plot. A major part of the increase in DOC at the treated plots apparently had a hydrophobic character and was of high molecular weight corresponding to 3–10 kDa. The concentration of DOC < 1 kDa in the control and treated plots was similar.     

Influence of arsenic co-contamination on DDT breakdown and microbial activity

The impacts of arsenic co-contamination on the natural breakdown of 1,1,l1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) in soil are investigated in a study of 12 former cattle dip sites located in northeastern NSW, Australia. This study examines the relationship between the intrinsic breakdown of DDT to 1,1 -dichloro-2,2-bis(4-chlorophenyl)ethane (DDD) and 1,l-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE), and the impacts of arsenic co-contamination on this breakdown. Between-site analysis demonstrated that arsenic at 2000 mg/kg gave a 50% reduction in the concentration of DDD compared to background arsenic of 5 mg/kg.Within-site analysis also showed the ratio of DDT:DDD increased in soils as arsenic concentrations increased. This within-site trend was also apparent with the DDT:DDE ratio, suggesting inhibition of DDT breakdown by arsenic co-contamination. Microbial activity was inhibited as residues of total DDTs and arsenic increased. Hence arsenic co-contamination and high concentrations of DDT in soil may result in an increased persistence of DDT in the environment studied.     

Technology,managerial, and policy initiatives for improving environmental performance in small-scale gold mining industry

This paper reviews a series of strategies for improving environmental performance in the small-scale gold mining industry. Although conditions vary regionally, few regulations and policies exist specifically for small-scale gold mining activity. Furthermore, because environmental awareness is low in most developing countries, sites typically feature rudimentary technologies and poor management practices. A combination of policy-, managerial- and technology-related initiatives is needed to facilitate environmental improvement in the industry. Following a broad overview of these initiatives, a recommended strategy is put forth for governments keen on improving the environmental conditions of resident small-scale gold mines.     

A Comparative Analysis of the Vegetation and Topsoil Cover Nutrient Status between Two Similarly Rehabilitated Ash Disposal Sites

The aim of this paper is to compare the rehabilitation result between two ash disposal sites with regard to its vegetation establishment and soil nutrient status. The study areas were situated in close proximity, in the Mpumalanga coalfield, South Africa. Although both areas received a similar amelioration treatment and were seeded with similar seed mixture the vegetation composition were significantly different. Both areas were poor in essential nutrients, this probably being one of the most limiting factors for vegetation establishment. No serious phytotoxic conditions, as is frequently experience with coal ash, could be identified. A regular monitoring and low level maintenance program is therefore proposed to improve the sustainability of the vegetation. The study proposed that results form such evaluations be used to identify performance standards for rehabilitated derelict land.     

Accumulation of Heavy Metals by in vitro cultures of plants

The aim of the project is to study heavy metals accumulation by the selected plants in both laboratory and field conditions. Within the experiments the aspen (Populus tremula × tremuloides), sunflower (Helianthus annuus) and corn (Zea mays) plants were studied. The reasons for this selection were: a fast growth of these plants, an accumulation capacity and an ability to survive in different types of soils. The study was carried out on the aspen plantlets grown in vitro. The plants were exposed to the aqueous solutions having concentrations 0.1 mM, 0.5 mM of Pb²⁺ or Ni²⁺, respectively. The accumulation capacityfor aspen, was about 70% of Pb²⁺ originally present in the solution. The starting concentration of Pb²⁺ (0.5 mM) exhibited no negative impact on the growth. Besides in vitro expositions, a pilot-scale phytoremediation experiment was carried out at the polluted industrial area (Zn – 75000 mg/kg), (Pb – 16000 mg/kg), (Cr – 590 mg/kg), (Cd – 90 mg/kg) and (Cu – 1700 mg/kg).