The present study explained the effect of pretreatments on the biosorption of Cr (III) and Cr (VI) by Cassia fistula biomass from aqueous solutions. For this purpose Cassia fistula biomass was pretreated physically by heating, autoclaving, boiling and chemically with sodium hydroxide, formaldehyde, gluteraldehyde, acetic acid, hydrogen peroxide, commercial laundry detergent, orthophosphoric, sulphuric acid, nitric acid, and hydrochloric acid. The adsorption capacity of biomass for Cr (III) and Cr (VI) was found to be significantly improved by the treatments of gluteraldehyde (95.41 and 96.21 mg/g) and benzene (85.71 and 90.81 mg/g) respectively. The adsorption capacity was found to depend on pH, initial metal concentration, dose, size, kinetics, and temperature. Maximum adsorption of both the Cr (III) and Cr (VI) was observed at pH 5 and 2. When Freundlich and Langmuir isotherms were tested, the latter had a better fit with the experimental data. The kinetic studies showed that the sorption rates could be described better by a second order expression than by a more commonly applied Lagergren equation.

The selective recovery of Cd from simulated spent nickel–cadmium battery solutions was achieved using a Cd working electrode in a laboratory cell with a three-electrode arrangement in hydrochloric, nitric, and sulfuric acids. The latter was selected for further study of the recovery step. Nitrate media were found to be unsuitable for Cd recovery since nitrates are reduced at the required deposition potentials. Cd(II) deposition on Cd electrodes is favored in sulfate or chloride media since it occurs at a potential some 200 mV less negative than that of Ni(II). A good percent Cd recovery (>90%) with high selectivity (approximately 0% Ni) and a reasonably high current efficiency (>80%) can be achieved under appropriate conditions. The irreversible nature of Ni(II) reduction provides the necessary framework to achieve such a selective separation.

Two series of laboratory-scale vertical flow systems (flooded and nonflooded columns) were designed to compare nitrogen removal performance, nitrous oxide emission, and ammonia volatilization under different water levels upon treating diluted digested livestock liquid. In these systems, influent was supplied at three hydraulic loading rates (HLRs of 1.25, 2.5, and 5 cm day⁻¹) during stage 1 and the rates were doubled during stage 2 when the water levels of nonflooded columns were elevated from zero to half the height of the soil column. After hydraulic loading rates doubled, the average removal rates of total nitrogen in flooded columns varied from 1.27 to 2.94 g⁻² day⁻¹ and those in nonflooded columns ranged from 1.23 to 3.88 g⁻² day⁻¹. The T-N removal at an HLR of 10 cm day⁻¹ in the nonflooded column with an elevated water table level had higher efficiency than that in the flooded column, suggesting T-N removal is enhanced in the nonflooded column probably due to the improved coupled nitrification–denitrification process under the elevated water table level condition. On the other hand, there was a significant correlation (r ² = 0.532, p < 0.001) between the N₂O flux and redox potential that mainly corresponded to water levels and HLRs, suggesting anoxic or aerobic conditions stimulate N₂O emission by enhancing the nitrification (nitrification–denitrification) process. In contrast, NH₃ volatilization had a high flux in the anaerobic condition mainly because of flooding. Based on the experimental results, it is hypothesized a nonflooded condition with higher water table level (Eh range of −160 to +260 mV) would be suitable to reduce N₂O emission and NH₃ volatilization peak value by at least half while maintaining relatively efficient nitrogen removal performance.

Many industrialized regions in the world are faced with local overproductions of animal manure requiring processing in an economic sound manner. Intensive animal production in Flanders and the Netherlands has resulted in a considerable overproduction of animal manure. Spreading the excess manure over arable land has resulted in contamination and eutrophication of groundwater and surface waters. Over the last 4 years, research was conducted towards the potential of more economic constructed wetlands for the final treatment step. Although, initial results with laboratory flow field experiments were insufficient to reach stringent discharge criteria (Meers et al., Water Air Soil Pollut 160:15-26, 2005a), progressive optimisation of the tertiary treatment as well as of the preceding conditioning has resulted in a consistently performing pilot scale system (1,000 m³ year⁻¹ capacity) with effluent concentrations below the discharge criteria of 15 mg l⁻¹ N, 2 mg l⁻¹ P and 125 mg l⁻¹ COD (chemical oxygen demand), at a cumulated cost (operational plus investment) of 3-4 [Euro Sign] m⁻³ of pre-treated pig manure. Construction of full-scale installations with annual capacity of 10,000-25,000 m³ based on this pilot model are scheduled, with the first installation currently under way. The concept has the potential to provide a low cost, in situ treatment system allowing animal farmers to process excess animal manure themselves without the requirement of expensive ex situ treatment based on industrial scale membrane technology facilities. This paper presents the research findings of the first year of the pilot scale installation.

The present paper describes the results of experiments with measurements of heavy metals concentrations in soil, leaves and roots of Zea mays cultivated near the major road in the area Araxos, Greece. The chain of ecological interactions is decomposed into individual subsystems with sufficiently small number of data samples describing concentrations of elements. The GMDH-based regression models are obtained and analyzed to assess different aspects of interactions within the chain “soil-roots-leaves”. The paper also represents a qualitative assessment technique to simplify analysis of the results, as well as to generalize the modeling results for different subsystems to the whole system.

Lake St. Pierre (LSP), constituted of a 120 km² stretching of the St. Lawrence River (Southern Québec), hosts the largest freshwater fishery industry in Canada. The lake drains, through its main tributaries, an important area of agrarian land and was subjected to intense industrial activities in the past century. In this paper, we present (1) an estimation of the seasonal aquatic mercury (Hg) inputs to LSP from the St-Lawrence River and two major tributaries; (2) a reconstruction, by the analysis of sediment cores, of the historic inputs of Hg into LSP and in a large riparian wetland, Bay St. François. Our results indicate that the aquatic Hg inputs to LSP (290 kg Hg between April 2003 and April 2004) are moderately elevated with most of the inputs occurring from the St. Lawrence River, either in spring or early winter, during high flow episodes. The sediment profiles suggest a recent decrease in Hg inputs, likely attributable to improvements of industrial practices. The observed perturbation of the surface sediments give evidence of an active hydrodynamic regime, suggesting that LSP could only act as a transitory system for suspended sediment and Hg, with seasonal accumulation and recurrent re-suspension resulting from changes in the hydrodynamic regime. Finally, we observed positive MeHg fluxes from the sediment to the water at different seasons in Bay St. François. However, Hg levels in fish like walleyes of LSP are reported to be low, which could be explained by faster fish growth rates following in part intense fishing pressure in LSP.

Elevated concentrations of trace metals in soil can increase the risk of pollution to ecosystems and human health. This cannot be predicted solely from the total and/or extracted concentration of metals from soil samples, as movement of trace elements to the groundwater is also a result of the flow solution through the vadose zone. The rate at which trace elements move are not usually directly measurable, and thus it must be estimated taking into account water transport through the soil. Therefore, a field portable drop-former rainfall simulator has been designed and used to study trace-element mobility in small field plots. The rainfall simulator permits a wide range of variation in rainfall intensities and provides a homogeneous distribution of the simulated rain in a 0.25 m² plot with low cost per data collected and short time. Performance of the rainfall simulator has been evaluated and a preliminary assessment of the amount of pollutants present in the soil (As, Cu and Zn) that can reach groundwater via soil drainage is made by combining rainfall-simulation experiments with infiltration estimates based on a stochastic model of the local climate. The study was conducted in soils affected by the Aznalcóllar toxic spill in the Guadiamar river basin (Spain). Infiltration experiments reveal that the trace elements could be classified according to their mobility as As < Cu < Zn. The presence of high gravel content below this depth increased the amount of drainage and therefore the risk of groundwater pollution, especially with Zn, which was found below 50 cm depth.

In order to implement best environmental management practices in agricultural watershed, it is necessary to evaluate non point source pollution loads and identify critical watershed pollution sources, which are regional management priority missions. Nutrient related non point source pollutant inputs can increase primary production and intensify water eutrophication. Not all watershed areas are critical and responsible for high amount nutrient pollution losses. Implementation of watershed environmental prevention is required to assess pollution yields. Further more, identification of these critical areas is essential for the effective and efficient implementation of watershed best environmental management. In this study, a geographic information system based Soil and Water Assessment Tool was applied in Bahe River watershed, a part of the Yangtze River basin. Land use, soil series texture and daily rainfall data for a 10-year period (1996-2005) was used in this study. The calibrated model system was verified to estimate average annual Organic Nitrogen and Organic Phosphorus yields in these 10 years. The estimated results were also tested and optimized by statistical software. Based on 10-year average yearly Organic Nitrogen yield and Organic Phosphorus losses, critical sub-watersheds were identified. The five sub-watersheds in the north part of watershed were under more intensive pollution yield, west group sub-watersheds contributed to moderate losses, whereas other sub-watersheds fell under slight loading classes. The research outputs developed a basis for an effective watershed environmental management plan. The study revealed that the Soil and Water Assessment Tool could be applied successfully for identifying critical sub-watersheds for watershed best environmental management purposes.

Measurements of nitrogen dioxide, nitrous and nitric acids as well as ozone were made using newly developed instrumentation onboard the research vessel Aegeon in the Aegean Sea between 25th-29th July 2000. Typical nitrogen dioxide concentrations observed aboard the boat were 4-6 ppb (v/v) with a broad maximum of 20-30 ppb (v/v). Ozone concentrations typically ranged between 40 and 80 ppb (v/v). Mixing ratios of both nitric and nitrous acids in the ambient air of the Aegean Sea were mainly below 50 ppt (v/v). The data also showed a number of short pollution episodes with rapid changes in the concentration of reactive nitrogen compounds [nitrogen dioxide maximum up to 164 ppb (v/v), nitric acid maximum up to 12 ppb (v/v), nitrous acid maximum up to 2.7 ppb (v/v)] and ozone [maximum up to 88 ppb (v/v)]. These episodes were correlated with pollution plumes originating from boats upwind, at short distance, from the R/V Aegeon. The measurements revealed the importance of nitrous and nitric acids for the transport of nitrogen to marine biota in busy ship lanes.

Natural conditions and human activities have caused serious quality degradation of the Quaternary aquifer in the north of the United Arab Emirates (UAE). The aquifer within Ajman City is unconfined, receiving limited recharge (12 542 m³/day) from the east and large pollutants flux (4,800 m³/day) from land surface. Field survey and laboratory analyses revealed anomalies in groundwater salinity (TDS), total hardness (TH), dissolved oxygen (DO), cations (Ca²⁺, Mg²⁺, Na⁺ and K⁺), anions ( [graphic removed] , [graphic removed] , Cl⁻ and [graphic removed] ) and trace elements (Fe, Pb, Cd and Cr), which can be correlated to point and non-point pollution sources. Concentrations of trace elements are more responsive to anthropogenic sources than natural ones. High Fe and Pb levels were measured close to the untreated sewage disposal site, while high Cd and Cr contents were observed near hospitals and clinics. Iso-concentration maps of salinity and major ions, in addition to hydrochemical profiles were used to define the seawater-groundwater interface in Ajman City. The potentiometric surface map of the Quaternary aquifer within the study area shows that groundwater flows from the east towards the Arabian Gulf in the west. The proposed landfill site is suitable because it lies within a topographic low, receiving groundwater flow from all directions.