Concentrations of mercury (Hg) were measured in six dated cores from four lakes in western Whatcom County, Washington, USA, that were at various bearings from a chlor-alkali plant, two municipal waste incinerators and a municipal sewage sludge incinerator. The importance of atmospheric emissions of Hg from these local municipal and industrial sources was evaluating by comparing the temporal trends in sedimentation of the lake cores with the emission history of each Hg species and by examining the geographical distribution of Hg sedimentation in relation to the region's primary wind pattern. Local municipal and industrial sources of atmospheric Hg were not responsible for the majority of the Hg in the upper layer of sediments of Whatcom County lakes because of (1) the significant enrichment of Hg in lake sediments prior to emissions of local industrial and municipal sources in 1964, (2) smaller increases in Hg concentrations occurred after 1964, (3) the similarity of maximum enrichments found in Whatcom County lakes to those in rural lakes around the world, (4) the inconsistency of the temporal trends in Hg sedimentation with the local emission history, and (5) the inconsistency of the geographic trends in Hg sedimentation with estimated deposition. Maximum enrichment ratios of Hg in lake sediments between 2 and 3 that are similar to rural areas in Alaska, Minnesota, and New England suggest that global sources of Hg were primarily responsible for increases of Hg in Whatcom County lakes beginning about 1900.

This paper reports on studies conducted during 2005 in the ecosystem of the Solina-Myczkowce mountain complex of mesotrophic reservoirs on the San River, SE Poland. Of the 1,950 t of dissolved silica calculated to flow into the reservoirs in the course of the year, c. 20% of the load was retained in the reservoirs. However, most of this retention took place in the lower Myczkowce Reservoir. Far-reaching depletion to below 10 μM L-¹ of silicate was noted during the summer in the epilimnetic waters of the two reservoirs. In turn, the hypolimnion was seen to go through an enrichment process connected with sedimentation and releases from sediment. The observed depletion causes a decrease in the DSi:DIP ratio in the euphotic zone of the reservoirs, with simultaneous growth of non-siliceous algae expressed as chl a concentration.

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.

Urban rainfall-runoff residuals contain metals such as Cr, Zn, Cu, As, Pb and Cd and are thus reasonable candidates for treatment using Portland cement-based solidification-stabilization (S/S). This research is a study of S/S of urban storm water runoff solid residuals in Portland cement with quicklime and sodium bentonite additives. The solidified residuals were analyzed after 28 days of hydration time using X-ray powder diffraction (XRD) and solid-state ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. X-ray diffraction (XRD) results indicate that the main cement hydration products are ettringite, calcium hydroxide and hydrated calcium silicates. Zinc hydroxide and lead and zinc silicates are also present due to the reactions of the waste compounds with the cement and its hydration products. ²⁹Si NMR analysis shows that the coarse fraction of the waste apparently does not interfere with cement hydration, but the fine fraction retards silica polymerization.

The Marais Vernier is the largest freshwater wetland in the Seine Estuary in northern France. It is in a heavily urbanized and industrialized region and could be affected by atmospheric deposition and by fluvial input of contaminants in water diverted from the Seine River. To evaluate contaminant histories in the wetland and the region, sediment cores were collected from two open-water ponds in the Marais Vernier: the Grand-Mare, which was connected to the Seine by a canal from 1950 to 1996, and the Petite Mare, which has a small rural watershed. Diversions from the Seine to the Grand-Mare increased sedimentation rates but mostly resulted in low contaminant concentrations and loading rates, indicating that the sediment from the Seine was predominantly brought upstream by tidal currents from the estuary and was not from the watershed. Atmospheric sources of metals dominate inputs to the Petite Mare; however, runoff of metals from vehicle-related sources in the watershed might contribute to the upward trends in concentrations of Cr, Cu, and Zn. Estimates of atmospheric deposition using the Petite Mare core are consistent with measured deposition in the region and are mixed (similar for Hg and Pb; larger for Cd, Cu, and Zn) compared with deposition estimated from sediment cores in the northeastern United States. A local source of PAHs in the watershed of the Petite Mare is indicated by higher concentrations, higher accumulation rates, and a different, more petrogenic, PAH assemblage than in the Grand-Mare. The study illustrates how diverse sources and transport pathways can affect wetlands in industrial regions and can be evaluated using sediment cores from the wetland ponds.

A study on perchlorate distribution was conducted in male adult prairie voles (Microtus ochrogaster). Excretion via urine was the major pathway for perchlorate fate in the body, with the highest concentrations of perchlorate detected in urine after exposure to perchlorate through drinking water [250 μg/ml Mg(ClO₄)₂], and an average of 34% and 88% of perchlorate intake recovered in urine in the 4- and 8-h exposure groups, respectively. Perchlorate mass in kidney, thyroid, blood, and urine were related to perchlorate intake (254.5-2687.7 μg). Perchlorate excretion and depuration patterns via urine were tested further using male adult deer mice (Peromyscus maniculatus). Animals were exposed to perchlorate through dosed drinking water (0, 17, 165, and 1600 ng/ml). Perchlorate concentrations in urine showed a significant difference among the three dosed groups during a 28-day exposure period. However, no difference was found in urine among the three dosages in terms of mass percentage of perchlorate intake from water at each sampling time over the 28-day exposure period. Both concentrations of perchlorate and mass percentage in urine reached a steady state after 1 day in all treatments. On average 46%, 46%, and 61% of perchlorate intake from water was recovered in urine over the exposure period in high, medium, and low dose groups, respectively. Including perchlorate consumption from rodent chow (1.44 ng/g), less than 46% of perchlorate intake was recovered in urine in the high and medium dose groups, and <61% in the low dose group. Three parameter first-order decay models fit the depuration curve very well, with r > 0.99 in both the low and high dose groups; half-lives of perchlorate in deer mice were estimated as 9.12 and 7.25 h in the low and high dose groups, respectively. Endogenous generation of perchlorate and/or some degree of retention or metabolism of perchlorate may occur in deer mice, based in part on the uncompleted mass balance in the excretion and depuration experiments. The data reported herein should provide additional insight for perchlorate fate determination in animals and humans and valuable information for perchlorate risk assessment in the environment, especially wildlife.

The bioremediation of petroleum contaminated soil was investigated using a laboratory scale aerated reactor. The Indigenous bacteria, Stenotrophomonas multophilia, were isolated from the contaminated sites near to Jordan Petroleum Refinery and used further in the bioremediation experiments. First order kinetic equation has been proven to satisfactorily describe the biodegradation of petroleum contained in soil in the presence of the isolated bacteria. The results also showed that the first order kinetic constants for the different bioreactors vary between 0.041 and 0.0071/day. The overall kinetic constant k' was determined based on food-to-microorganisms ratio and found to be 0.02/day.

Numerous sites are contaminated with both heavy metals and polycyclic aromatic hydrocarbons (PAHs) and the technologies to treat such mixed contaminants are very limited. Electrokinetic remediation has the potential to remediate mixed contaminants in soils, including low permeability soils; however, the efficiency of this technology depends on the extracting solution employed. Previous studies on electrokinetic remediation have focused on the removal of heavy metals and organic compounds when they exist individually in clayey soils. In the present study, the feasibility of using cosolvents to enhance the electrokinetic removal of PAHs from clayey soils in the presence of heavy metals is investigated. A series of laboratory electrokinetic experiments was conducted using kaolin soil spiked with phenanthrene and nickel at concentrations of 500 mg/kg each to simulate typical field mixed contamination. Experiments were performed using n-butylamine (cosolvent) at concentrations of 10 and 20% and deionized water, each mixed with 0.01 M NaOH solution and circulated at the anode to maintain alkaline conditions. A periodic voltage gradient of 2 VDC/cm in cycles of 5 days on and 2 days off was applied in all the tests. During the initial stages when the soil pH was low, nickel existed as a cation and electromigrated towards the cathode. However, as the soil pH increased due to hydroxyl ions generated at the cathode and also flushing of high pH n-butylamine solution from the anode, nickel precipitated with no further migration. Phenanthrene was found migrating towards the cathode in proportion to the concentration of n-butylamine. The extent of phenanthrene removal was found to depend on both the electroosmotic flow and the concentration of n-butylamine, but the presence of nickel did not influence the transport and removal of phenanthrene.

This paper reports a laboratory-scale investigation concerning the use of sulphate-reducing bacteria (SRB) in a semi-continuous process, where column packed-bed type bioreactors were used for the treatment of acid mine drainage (AMD). The use of different materials as solid matrices was tested and the performance of the bioremediation processes was discussed in terms of sulphate and metals removal and acid neutralization. The behaviour of a reactor filled with acidic soil from a mining area and organic wastes was compared with other three reactors where coarse sand, glass spheres and cereal straw were used as packaging materials. Batch experiments showed the presence and growth of SRB from the acidic soil in different pH conditions and the effect of the absence or presence of several added carbon sources: lactate, ethanol and lactose. The data showed that it is possible to grow SRB using the acidic soil as source of inocula, in the absence and in the presence of the carbon sources tested, since the pH of the media was previously increased to values of 5 or higher. When acidic soil from the mining area and organic wastes were utilised as column matrices, it is possible to remove the metals and to neutralise the acidity of AMD, although an inefficient sulphate removal was observed. When coarse sand or glass spheres were utilised, efficient metals sulphate removal were achieved. However, the incapacity of both systems to generate enough alkalinity does not allow maintaining their good performances in terms of iron removal and sulphate reduction. As a result, the incorporation of materials with neutralizing and buffer capacity to the matrix is recommended. Due to its low density, cereal straw was not suitable to obtain an anaerobic environment inside the column for SRB activity.

Although microbially-mediated redox environments can alter the characteristics of soil/sediment organic matter (SOM) and its interactions with persistent hydrophobic organic contaminants (HOCs) bound to soils and sediments, the nature of their effects has not been adequately addressed. In this study, a field soil collected from a manufacturer gas plant site and contaminated historically with creosotes was incubated under aerobic and anoxic/anaerobic conditions along with various amendments (extra carbon and enrichment minerals) for stimulating microbial activities. Anaerobic conditions stimulated significant fractions of bound polycyclic aromatic hydrocarbons (PAHs) encompassing naphthalene through benzo[g,h,i]perylene to be mobilized to the aqueous phase, leaving their aqueous phase concentrations far in excess of solubility (increases in their apparent aqueous phase concentrations by factors as high as 62.8 relative to their initial aqueous phase concentrations). Such effects became more evident for high molecular weight PAHs. Dissolved organic matter exhibiting a high affinity for PAHs was liberated from soils during the anaerobic soil incubations. Feasibility of this concept for field applications was evaluated with a lab-scale continuous flow system composed of an anaerobic soil column followed by an aerobic bioreactor inoculated with PAH-degrading microbes. High quantities of PAHs exceeding their aqueous solubilities were eluted from the anaerobic soil column and those mobilized PAHs were readily bioavailable in the secondary aerobic bioreactor. This study may offer a potential method for cost-effective and performance-efficient ex situ remediation technologies (or in situ if appropriate hydrological control available in the contaminated field site) and risk assessment for the HOC-contaminated soils/sediments.