The concentrations and distribution of selected heavy metals in epipelic and benthic sediments of Cross River Estuary mangrove swamp were studied to determine the extent of anthropogenic inputs from industrial activities and to estimate the effects of seasonal variations on geochemical processes in this tropical estuarine ecosystem. The analysis shows that the mean concentrations (mg/kg, dw) of Cu, Cr, Fe, Ni, Pb, V and Zn vary from 24.1-32.4, 19.9-27.4, 666.7-943.5, 15.2-30.3, 8.8-24.7, 2.2-6.9 and 140.1-188.9, respectively. An important observation is that, in general, lowest metal concentrations are found during the dry season, compared to wet season. Pollution load index (PLI) and index of geoaccumulation (I geo) revealed overall low values but the enrichment factors (EFs) for Cr, Zn, and V were high, and this reflects the intensity of anthropogenic inputs related to industrial discharge into the estuary. The mean concentrations of Zn, Cu and to some extent Ni exceeded the Effects Range--Low (ERL) and Threshold Effect Level (TEL) values in majority of the samples studied, indicating that there may be some ecotoxicological risk to organisms living in these sediments. The inter-element relationship revealed the identical source of elements in the sediments of the studied area. The concentration of heavy metals reported in this work will be useful as baselines for comparison in future sediment quality studies.

Chemical remediation of soil and groundwater containing hexavalent chromium (Cr(VI)) was carried out under batch and semi-batch conditions using different iron species: (Fe(II) (sulphate solution); Fe⁰ G (granulated elemental iron); ZVIne (non-stabilized zerovalent iron) and ZVIcol (colloidal zerovalent iron). ZVIcol was synthesized using different experimental conditions with carboxymethyl cellulose (CMC) and ultra-sound. Chemical analysis revealed that the contaminated soil (frank clay sandy texture) presented an average Cr(VI) concentration of 456 ± 35 mg kg⁻¹. Remediation studies carried out under batch conditions indicated that 1.00 g of ZVIcol leads to a chemical reduction of ~280 mg of Cr(VI). Considering the fractions of Cr(VI) present in soil (labile, exchangeable and insoluble), it was noted that after treatment with ZVIcol (semi-batch conditions and pH 5) only 2.5% of these species were not reduced. A comparative study using iron species was carried out in order to evaluate the reduction potentialities exhibited by ZVIcol. Results obtained under batch and semi-batch conditions indicate that application of ZVIcol for the “in situ” remediation of soil and groundwater containing Cr(VI) constitutes a promising technology.

In this study we have investigated the uptake and distribution of arsenic (As) and phosphate (Pi) in roots, shoots, and grain of wheat grown in an uncontaminated soil irrigated with solutions containing As at three different concentrations (0.5, 1 and 2 mg l⁻¹) and in the presence or in the absence of P fertilization. Arsenic in irrigation water reduced plants growth and decreased grain yield. When Pi was not added (P-), plants were more greatly impacted compared to the plus Pi (P+) treatments. The differences in mean biomass between P- and P+ treatments at the higher As concentrations demonstrated the role of Pi in preventing As toxicity and growth inhibition. Arsenic concentrations in root, shoot and grain increased with increasing As concentration in irrigation water. It appears that P fertilization minimizes the translocation of As to the shoots and grain whilst enhancing P status of plant. The observation that P fertilization minimises the translocation of arsenic to the shoots and grain is interesting and may be useful for certain regions of the world that has high levels of As in groundwater or soils.

Manganese was removed from naturally polluted river sediment by applying an electrokinetic remediation technique. The sediment was alkaline and had 20% clay, which was mainly illite. The electrokinetic remediation experiments were performed by controlling pHs in the electrode cells and reverse electroosmotic flows were observed, i.e., water moved from cathode towards anode. Manganese accumulated in areas closer to cathode, however, other metals, such as copper, zinc and lead were mostly observed in the middle section of the sediment. As a result of reverse electroosmotic flow, the removal efficiencies of metals were low and the highest removal efficiencies of manganese, copper and lead, were evaluated as 18%, 20% and 12%, respectively. Almost no removal of zinc was observed in all electrokinetic remediation experiments.

Field measurements were conducted using one to three sheets of a poly-tetrafluoroethylene (PTFE) membrane resistance-type passive sampler (N type sampler) and diffusion length resistance-type sampler (O type sampler) to compare sampling resistance. Acidic gases such as nitric acid (HNO₃), hydrochloric acid (HCl), sulfur dioxide (SO₂), ozone (O₃), ammonia (NH₃), nitrogen dioxide (NO₂), and nitrogen oxides (NO X ) were sampled using five types of capturing filter paper: plain polyamide filter ([Greek Phi symbol]47 mm) and cellulose filters ([Greek Phi symbol]14.5 mm) impregnated with NaNO₂ + K₂CO₃, H₃PO₄, triethanolamine (TEA), and TEA + 3-oxo-2-phenyl-4,4,5,5-tetramethylimidazolin-1-oxyl (PTIO). Four sets of the samplers were exposed to the atmosphere for 4 or 5 weeks through four seasons in FY 2006. The amount of gas components captured occurred in the order of NO X > O₃ > NO₂ > NH₃ > SO₂ > HCl > HNO₃ for all of the filters in spring and autumn. However, the amount of NH₃ captured was large in summer and the amount of NO X was large in winter. The relative standard deviations (RSDs) were less than 10% except for NH₃ with the O type sampler in spring and autumn, and for HCl of both type samplers in winter. The RSDs were not dependent on the numbers of PTFE sheets for gas species and season. When the N type sampler mounted on one PTFE sheet was normalized to unit, the resistance values of two and three PTFE sheets for HNO₃ were 2.3-2.4 and 4.2-6.1, respectively, while the values of two and three sheets for SO₂, O₃, HCl, and NH₃, were 1.1-1.5 and 1.3-1.9, respectively. There was little variation in resistance for NO₂ and NO X , as shown by the values of 1.0-1.1 and 0.9-1.2, respectively. For comparison with the O type sampler, the resistances values for SO₂, O₃, HCl, NH₃, NO₂ and NOX were 4.9-5.8, 2.5-3.2, 2.7-4.5, 4.1-12.6, 1.4-1.9, and 1.2-2.4, respectively. The resistance values of the O type sampler were larger than those of the N type samplers. The collection of HNO₃ was decreased 25% per PTFE sheet, while the decreases for SO₂, O₃, HCl and NH₃ were moderate at 12-17%. In contrast, collection of NO₂ and NO X was minimally affected by the number of PTFE sheets. The concentration of HNO₃, SO₂, HCl and NH₃ in the N type passive sampling method was compared with that of the four-stage filter pack method. The passive method for HNO₃, SO₂ and HCl was in fair agreement with the filter pack method. For NH₃, the concentration by passive method was lower than that by the active method.

Understanding wetland hydrogeology is important as it is coupled to internal geochemical and biotic processes that ultimately determine the fate of potential contaminant inputs. Therefore, there is a need to quantitatively understand the complex hydrogeology of wetlands. The main objective of this study was to improve understanding of saturated groundwater flow in a forested riparian wetland located on a golf course in the Lower Pee Dee River Basin in South Carolina, USA. Field observations that characterize subsurface wetland flow critical to solute transport originating from storm-generated runoff are presented. Monitoring wells were installed, and slug tests were performed to measure permeabilities of the wetland soil. A field-scale bromide tracer experiment was conducted to mimic the periodic loading of nutrients caused by storm runoff. This experiment provided spatial and temporal data on solute transport that were analyzed to determine travel times in the wetland. Furthermore, a 3-D numerical, steady-state flow model (MODFLOW) was developed to simulate subsurface flow in the wetland. A particle tracking model was subsequently used to calculate solute travel times from the wetland inlet to the outlet based on flow modeling results. It was evident that observed tracer breakthrough times were not typical of these measured wetland soil matrix conductivity values. Based on surface water sampling results at the wetland outlet, tracer arrival time was about 9 h after the injection of the tracer. These results implied an apparent mean K value of 2,050 m/day, which is 152 times larger than the mean of the measured values using slug tests (13.4 m/day). Modeling efforts clearly demonstrated this implied preferential flow behavior; particle travel times resulting from the calibrated flow model were in the order of hundreds of days, while actual travel times in the wetland were in the order of hours to a few days. This significant difference in travel times was attributed to the presence of macropores in the form of dead root channels and cavities forming a pipe-flow network. The analyses presented in this study resulted in an estimate of the ratio of matrix permeability to matrix plus macropore permeability of approximately 1/150. Eventually, the tracer test and resulting travel times between various points in the wetland were critical to understanding the true wetland flow dynamics. The final conceptual model of the hydraulic properties of the wetland soils comprised a low permeability matrix containing a web of high K macropores. Simulation of tracer transport in this system was possible using a flow model with significantly elevated K values.

Short term influence of silica, palladium, gold and copper nanoparticles on a soil microbial community and the germination of lettuce seeds are investigated in this study at two different concentrations of nanoparticles. Results show a statistically insignificant influence of the nanoparticles in the soil on the number of colony forming units, peak areas of methyl ester of fatty acids in the FAME profile or on the total soil community metabolic fingerprint (P > 0.05). Also, all nanoparticles tested in the study influenced the growth of lettuce seeds as measured through shoot/root ratios of the germinated plant (P < 0.05).

The decomposition of gaseous isopropanol (IPA) by UV/TiO₂ process in an annular photoreactor was studied under various conditions such as UV light intensity and inlet IPA concentrations. In order to impede the rapid electron/hole recombination during photoreaction, the Ag deposited on TiO₂ photocatalysts were prepared by a photodeposition process. This study was aimed at applying the photocatalytic oxidation using the Ag/TiO₂ and pure TiO₂ catalysts to remove gaseous IPA. The PL analyses indicated that the silver on the surface of TiO₂ could inhibit the electron/holes recombination. For experiments conducted with gaseous IPA under UV light irradiation, the photocatalytic activity of Ag deposited TiO₂ surface was significantly superior to that of TiO₂ only ones.

The rate at which creosote-treated pilings release polycyclic aromatic hydrocarbons (PAHs) into the environment should diminish with structure age and weathering, and so, it may be assumed that PAH concentrations in the vicinity of old structures (>30 years) may approach background levels. However, this may not be true in cold environments where PAH release and degradation rates are slow and where pilings continue to experience significant physical damage. Moreover, PAHs will remain high in the vicinity of pilings if current and wave action is insufficient to disperse and dilute PAHs over a wider area and/or where PAHs do not become diluted and buried by uncontaminated sediments. This is demonstrated in our investigation of the sediments of the Grey Owl Marina, located in Prince Albert National Park, in central Saskatchewan, Canada. The marina, constructed in the early 1960s, consists of six piers and is protected from strong wave action by a breakwater. PAH concentrations were high in sediments collected under the piers and inside the boat slips, exceeding probable effect levels for several compounds. Various lines of physical and chemical evidence pointed to creosote as being the primary PAH source with a mixture of relatively undegraded and weathered PAHs being present. PAH concentrations decreased rapidly 2 m and further away from the pilings as a result of dilution with increasing dispersal over a broadening area. There was evidence of benthic community impairment, with total abundances negatively correlated with PAH concentrations. According to the Methods for Ranking Contaminated Aquatic Sites on Canadian Federal Properties, areas with the highest hazard scores were under the piers and inside the boat slips, while areas with the lowest hazard scores were >10 m from the pilings. Therefore, remedial actions based on piling and contaminated sediment removal may need to be conducted over only a small area, i.e., within 2 m of the pilings.

Metal concentrations in a sediment core from a moat outside Osaka Castle in Japan were measured by ICP-MS following a microwave extraction method. Concentrations of metals in the sediment core samples peaked around 1945 when the World War II ended. This is in part due to great air raids on Osaka. In cluster analysis using metal concentrations, the fractions of sediment core samples were classified into two groups, representing natural sources (1795-1915) and anthropogenic sources (1922-1976), respectively. Results of lead isotope ratios also showed the anthropogenic influences from 1915 by changing the ratio values compared to those of natural sources. In addition, several components contributing to metal concentrations were identified by principal component analysis. The main component was controlled by natural sources and a decrease of the component score corresponded to an increased influence from anthropogenic sources. The largest impact of anthropogenic sources was shown around 1945.