The type and amount of indoor air pollutants affects the comfort and quality of indoor environments. Therefore, indoor air quality is an important issue with different social, economic, and health aspects because people in developing countries spend most of their time indoors being exposed to different kinds of indoor pollutants. The indoor air quality can be assessed empirically by measuring the pollutant concentrations or can be predicted by means of mathematical models. An indoor aerosol model describes the dynamic behavior of indoor air pollutants. The basic concept of indoor air models is the mass-balance-conservation where several factors that govern the indoor particle concentrations can be described. These factors may include direct emissions from indoor sources, outdoor aerosol particles penetrating indoors as a result of the ventilation and filtration processes, deposition onto indoor surfaces, and removal from indoor air by means of ventilation. Here we present principles of indoor aerosol models and we also give examples of different kind of models.

The enrichment factor, multivariate analysis and metal speciation studies were used to identify degree, source and dispersal of metal contamination in Khli Ti watershed, Thailand. Topsoil samples were collected throughout the watershed, analyzed for total metal concentration. Sequential extraction was also carried out to determine geochemical phases of metals which were identified as exchangeable and bound to carbonates, Fe–Mn oxides, organic matter and residuals. Soil characteristics including pH, total organic carbon, redox potential, cation exchange capacity and texture were also analyzed. Principal component analysis yielded three metal groups which explained 83% of the variance. The concentrations of metals which were derived from lithogenic origin, such as Co, Cr, Fe, Ni and V were in natural background levels and were mostly bound to the residual phase. The remaining elements (i.e. Ba, Cd, Cu, Pb, Sb and Zn) were associated with the contamination from previous activities of the Pb-ore concentrator and Zn–Pb mining. Anthropogenic contamination mainly increased Pb and Zn bound to Fe–Mn oxides at the expense of residual fraction. Even though low exchangeable Pb contents in Khli Ti soils indicated low availability to plants, Pb bound to Fe–Mn oxides fraction might increase its mobility under reducing conditions.

The practice of contaminant transport and remediation has shown significant progress in recent years. However, despite the significant progress made, remediation efforts are often delayed by extremely long breakthrough curve tails that render efforts to bring the level of contaminants below the regulatory standards inefficient. One hypothesis is that these long tails are due to the reservoir-like slow diffusive processes in soil micropore zones. This study compares the effects of micropores at macroscopic and microscopic levels and establishes a link between these approaches for validation and calibration purposes. The link between macroscopic and microscopic levels is established through comparisons and testing of the two models while incorporating appropriate scale and boundary effects. Despite the differences in conceptual approaches and simulation time, the two approaches rendered meaningful results. The link helps forecast the effects of micropore zone transport processes in the subsurface efficiently and thus allows development of numerical tools that could contribute towards more efficient remediation design.

Prescribed or natural drawdowns occur frequently in reservoirs but their effects on fish populations have been barely studied. As a consequence of a severe drought and the need to optimize water quality, a partial drawdown was prescribed in autumn 2005 to a eutrophic reservoir that provides water supply to a large metropolitan area (Barcelona, Spain). In order to avoid a potential massive fish kill given the reduced oxygen availability and high fish abundance, preventive purse seine fisheries were performed to reduce the fish stock. The fisheries had little effect on the fish assemblage because final population size structure and species composition did not change significantly. The species composition of the purse seine catches varied significantly during the drawdown with higher proportion of bleak (Alburnus alburnus) in pelagic water during the days of worst water quality, confirming that bleak is more tolerant than roach (Rutilus rutilus) to poor water quality and a potential good indicator of water pollution. The weight-length relationship (i.e. condition) of roach and bleak also varied significantly during the drawdown following the same tendency in both species, losing and recovering their weight (4.99% in roach and 5.96% in bleak) in only 16 days. The close relationship found between water quality and fish condition demonstrates that fish condition can be a good metric of the well being of fish, even for extreme short-term changes.

Aluminium is a non-essential element for biological systems and is used in water and wastewater processes that rely on (micro)biological purification processes. The effect of Al doses ranging from 100 to 2,000 μg/l on the microbial dissolved oxygen uptake (respiration) over a 24-h period was assessed. Results indicated that Al can reduce the 24-h respiration, but the effects of pH depression due to Al dosing during testing should be taken into account.

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.

A wide variety of aquatic organisms, including juvenile salmonids, assess local predation risks using chemosensory cues. Such chemical cues are typically released from injured conspecifics and their detection may lead to species-typical antipredator behaviour, increasing the probability of prey to survive during predator encounters. Studies have demonstrated however, that under weak acidification (pH ~6.0), the response towards these chemical alarm cues is impaired. However, it remains unknown if the loss of response is graded (i.e., the behavioural response decreases with a reduction in pH) or if there is a threshold pH at which prey can no longer detect the alarm cues. We conducted two laboratory experiments to examine the effects of a graded reduction in pH on the behavioural response of juvenile rainbow trout to conspecific chemical alarm cues. The results of our first experiment suggest that at pH 6.6 and above, the alarm cues elicited a strong antipredator response, while alarm cues buffered to pH 6.2 did not (i.e. not different from distilled water). However, alarm cues buffered to pH 6.4 elicited a weak response, suggesting a graded response. We directly tested this in our second experiment using a repeated measures design. The response to alarm cues at varying pH levels did indeed follow a graded loss of function. Together, our results suggest that juvenile rainbow trout exhibit a reduction in the response to conspecific alarm cues proportional to ambient acidity and that the response to these critically important cues is lost at pH below 6.4. As the detection and response to these chemical alarm cues have been shown to confer direct survival benefit to individuals, these results are therefore presented in relation to possible sub-lethal effects of anthropogenic acidification to freshwater fish.

A biological source treatment (BST) technique using remote sensing and biogeochemistry has been developed to address acid mine drainage (AMD) at its source. The BST technique utilizes down-hole injections of microbial inoculum and substrate amendments to establish a biofilm on the surface of metal sulfides (AMD source material). The treatment results in an elevated groundwater pH (from acidic to circum-neutral levels) and prevents further oxidation of AMD source material. The first 2 years of an ongoing field study of the BST technique at a reclaimed coal mine in central Tennessee (USA) has produced successful results. For instance, the water chemistry in a monitoring well down-gradient from injection wells has improved substantially as follows: the pH increased 1.3 units from 5.7 to 7.3, the dissolved (0.45 μm-filtered) iron concentration decreased by 84% from 93 to 15 mg/l, the conductivity decreased by 379 μS/cm, and sulfate decreased by 78 mg/l. Electromagnetic induction surveys were conducted to identify AMD source material and monitor BST performance by measuring changes in subsurface resistivity throughout the site. These surveys revealed a treatment zone created between injection wells where the resistance of contaminated groundwater from up-gradient AMD sources increased as it flowed past injection wells, thus, suggesting this technique could be used to treat AMD sources directly or to intercept and neutralize sub-surface AMD.

To assess possible adverse effects of residual chlorines from hypochlorite-treated seawater to non-target marine organisms, bioassays were carried out on marine amphipod Hyale barbicornis and estuarine fish Oryzias javanicus. Acute toxicity tests were first conducted using various concentrations of sodium hypochlorite (NaOCl) followed by a long-term exposure to residual chlorines from a test water treated with 1 mg L⁻¹ NaOCl. Results showed that NaOCl was acutely toxic to both organisms. However, long-term exposure to residual chlorines from NaOCl-treated waters caused no major adverse effects to both organisms under laboratory conditions since free chlorines in the treated water was reduced to about 10% by 23-h holding and 1-h aeration. No H. barbicornis died but residual chlorine-exposed juveniles had significantly shorter body lengths at the end of exposure. Residual chlorine-exposed O. javanicus also showed no significant differences to that of the control in all measured endpoints except for hatching time. The results suggest that using 1 mg L⁻¹ NaOCl for disinfection of ballast waters will produce residual chlorines that is far below the LC50 and EC50 of H. barbicornis and O. javanicus even on a long-term basis.

Remediation and management of contaminated sediments and dredged material is often difficult due to the complex mixtures of chemical substances that usually impact the sediments. The selection of the best option that leads to the sustainable management of the sediments of a site is not an easy task, and it should be based on the integration of technical, economic, social and environmental criteria. In this paper, an overview of the main alternatives for the management of contaminated sediments and dredged material is presented. This work highlights the wide variety of techniques and treatments that can be applied, including no action (i.e. monitored natural recovery), in-situ capping, in-situ treatments, ex-situ treatments or confined disposal. The utilisation of contaminated dredged material for a beneficial use, directly or after treatment, should be considered as its preferred final destination. Therefore, special emphasis has been given in this study to the presentation of possible beneficial uses of dredged material. The results of our research group, which are summarised in this paper, about the use of contaminated sediments as alternative raw materials in the manufacture of traditional clay-based ceramics, can serve as an example of beneficial uses that lead to marketable products. | This work was conducted under the framework of the Spanish Ministry of Education and Science Projects CTM2005-07282-C03/3 and CTM 2006-07960. M. Alvarez-Guerra was funded by the Spanish Ministry of Education and Science by means of an F.P.U. fellowship.