Experiments were conducted in an annular flume using waste bed sediment from a discontinued aquaculture operation to assess its stability against erosion. Critical shear stress for erosion was measured under different flow conditions and after three different consolidation periods (2, 7 and 14 days). The influence of biostabilization was also assessed as a mechanism for controlling the bed sediment stability. Results suggest a moderate increase in bed sediment strength with time as evidenced by the increasing critical bed shear stress for erosion with increasing consolidation times. Critical bed shear stress for erosion ranged from 0.06 to 0.1 Pa. Eroded floc size and settling velocities were in the range that would allow for significant horizontal transport of sediments provided a flow was present (i.e. transport outside of the aquaculture pens). The increase in sediment strength with time is believed to be more strongly influenced by biofilm integration on and within the surface sediment layer than to consolidation and dewatering effects. Extensive biofilm growth was visibly evident and microscopy confirmed the presence of extensive filamentous organisms (likely of a fungal origin) and bacteria. The point of failure of this biostabilized sediment was significantly lower than that reported for other natural freshwater and salt water sediments. Regardless of the sediment type, however, biostabilization is a consistent and important mechanism which controls the stability of sediments. Factors such as the microbial community and sediment floc structure will need to be considered in order to improve our understanding of the mechanisms of bed sediment stability and erosion for the environmentally sustainable operations of aquaculture facilities.

Large quantity of dehydrated oil sludge, generated in the disposal process of oil-containing sewage in Shengli oilfield, needs to be rendered harmless to human and to the environment. Bioremediation has been accepted as an important method for the treatment of oil sludge by employing indigenous or extraneous microbial flora. The bioremediation of a dehydrated oil sludge of 960 m³ in volume was carried out in a prepared bed in Binyi oil-containing sewage disposal station, Shengli oil fields, China. Four different treatments were made to study the impact of certain process parameters on the bioremediation efficiency. Of the oil contaminants, 52.75% was degraded within 160 days when treated in a greenhouse, while the oil contaminations decreased by only 15.46% in the untreated sludge. The variations of the physical and chemical properties of oil sludge, the amount and the functional diversity of microorganisms in sludge were characterized. The results indicated that the water-holding capacity of oil sludge, the amount and the metabolism functional diversity of microorganisms in sludge in the three treatments increased markedly compared with the control.

Naturally high total dissolved solids and upstream agricultural runoff often mask the influence of urban land cover on stream chemistry and biology. We examined the influence of headwater urbanization on the water chemistry, microbiology, and fish communities of the Big Brushy Creek watershed, a 96 km² drainage basin in the piedmont of South Carolina, USA. Concentrations of most major anions and cations (especially nitrate, sulfate, chloride, sodium, potassium, and calcium) were highest in the urban headwaters and decreased downstream. Generally, the highest concentrations of suspended coliform bacteria occurred in the urban headwaters. In contrast, stream habitat quality and the abundance, species richness, and species diversity of fishes did not differ significantly between urban and rural sites. Discharge of wastewater treatment plant effluent at one rural location caused an increase in concentrations of many solutes and possibly the abundance of benthic algae. We hypothesize that atmospheric dry deposition and domestic animal wastes are important sources of stream solutes and of coliform bacteria, respectively, in the urban headwaters. The lack of significant differences in fish abundance and diversity between urban and rural sites may indicate that urban development in the Big Brushy Creek watershed has not yet degraded habitat conditions greatly for stream fishes. Alternatively, agriculture or other land uses may have degraded stream habitat quality throughout the watershed prior to urbanization.

A total of nine sediment cores were collected from the five deep basins of Kejimkujik Lake, located in southwestern Nova Scotia, Canada, in order to track changes related to surface-water acidification and to test reproducibility of results between sediment cores from different basins in a large lake. Present-day and pre-industrial (c. 1850) samples were analyzed from all cores and detailed diatom profiles were undertaken on three cores to determine the timing of acidification. All three detailed diatom profiles show declines in inferred pH starting in the early 1930-1940s. Since the 1940s, diatom-inferred lakewater pH has declined from a background pH of ~5.8 (± 0.4) to a current diatom-inferred pH of ~4.9 (± 0.1). This corresponds to the current (2001-2002) range of measured lakewater pH = 4.7-5.2 with a mean pH = 4.9. Species diversity of diatoms also declines markedly in all cores with the Hill's N2 index decreasing from ~5 to near 1. The pre-impact diatom assemblages were dominated by Aulacoseira spp. and have since changed to dominance by Asterionella ralfsii var. americana (>45 μm). All nine sediment cores showed similar changes in diatom assemblages, diatom-inferred pH, and timing of the onset of acidification. Thus, paleolimnological inferences from deepwater sediment cores were highly reproducible in this large, morphometrically complex lake system.

Concentration levels of 11 lower carbonyls were studied at Montelibretti, a semi-rural area near Rome, Italy, over July-September 2005 and February 2006. In both periods the most abundant carbonyls were acetone and formaldehyde, followed by methylglyoxal, acetaldehyde and hexanal. Monthly variation was apparent with maximum values observed in July, when levels at least a factor two higher compared to the successive months were observed. In summer all carbonyls except acetone were reasonably well correlated among themselves and with ozone. In addition very high formaldehyde/benzene concentration ratios were measured in the summer months compared to February. These findings indicated that photochemical reactions should be the major source of carbonyls in summer. Ranking of carbonyls respect to ozone production potential emphasized the predominance of formaldehyde and methylglyoxal, followed at a distance by glyoxal and acetaldehyde.

Former gold mining at Rodalquilar in southeastern Spain exploited a high sulphidation epithermal silicified ore deposit that contained significant enrichments in several metals/metalloids such as As, Sb, Bi, and Te. Treatment of this ore took place adjacent to the village and involved physical crushing then chemical extraction of gold using cyanide and zinc. The waste materials from this processing system, contaminated with a range of trace elements, were deposited immediately below the mine, and have been left exposed to erosion. Over the last 40 years these oxidised ferruginous tailings have not only polluted the local drainage system but also provided a point source for contaminated aeolian dust under the prevailing dry, windy climate. Chemical analyses of particulate matter mechanically resuspended from the tailings materials show enrichments in metals and metalloids due to the preferential incorporation of these elements into the inhalable size fraction (PM₁₀). Of particular concern is the fact that these PM₁₀ can contain >1,500 ppm As and >40 ppm Sb. Given that both As and Sb are clastogenic metalloids with proven negative health effects, and that their oxidised forms are especially toxic, such contamination levels in windblown dusts around old mine sites are highly undesirable.

In intensively cultivated areas, agriculture is a significant source of pesticides associated with storm runoff. When these pollutants enter aquatic receiving waters, they have potential to damage nearby aquatic ecosystems. Constructed wetlands are a best management practice (BMP) designed to help alleviate this potential problem. A constructed wetland system (180 x 30 m) comprised of a sediment retention basin and two treatment cells was used to determine fate and transport of a simulated storm runoff event containing the insecticide diazinon and suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results indicated that 43% of the study's measured diazinon mass was associated with plant material, while 23 and 34% were measured in sediment and water, respectively. Mean diazinon concentrations in water, sediment, and plants for the 55-d study were 18.1 ± 4.5 μg/l, 26.0 ± 8.0 μg/kg, and 97.8 ± 10.7 μg/kg, respectively. Aqueous concentrations fluctuated in the wetlands between 51-86 μg/l for the first 4 h of the experiment; however, by 9 h, aqueous concentrations were approximately 16 μg/l. During the 55 d experiment, 0.3 m of rainfall contributed to fluctuations in diazinon concentrations. Results of this experiment can be used to model future design specifications for mitigation of diazinon and other pesticides.

A powerful 7.3 magnitude earthquake struck Taiwan on September 21, 1999. The stream water chemistry (pH, total alkalinity, conductivity, sodium, potassium, calcium, magnesium, ammonium, fluoride, chloride, sulfate, and nitrate) has been monitored since 1995 at the Guandaushi forestry riparian zone in central Taiwan. Collected data was used as a basis for comparing pre- and post-earthquake impacts. The pH, conductivity, and concentrations of Na, Ca, Mg, SO₄, and HCO₃ in stream water were lowest during the summer season, when stream water discharge was highest. On the other hand, the lowest concentrations of Cl, NH₄, and NO₃ in stream water occurred during the winter season, when stream water discharge was lowest. Also, K and F showed very little seasonal fluctuation in concentration. Downward trends in K and Ca were found 14 months prior to the earthquake; although, an upward trend occurred in NH₄ at the same time.

Due to the episodic nature of rainfall and the high dissolved metal concentrations in the acid sulfate soil catchment of Clothiers Creek (NSW, Australia), active treatment was considered more appropriate than passive treatment. Alkaline reagents were added to oxidised shallow drains to remove acidities ranging from 438 to 1,837 mg/L CaCO₃. A fine limestone slurry was produced from the pounding together of limestone rock fragments within a rotating drum and, on addition to drain waters, was found to remove acidity to varying degrees of effectiveness (from 12 to 100%). The efficiency decreased as the pH of the water approached neutrality due to calcite saturation and the slow reaction rate of limestone at high pH. Hydrated lime powder was also mixed with drain water in the rotating drum though most mixing occurred once the slurry entered the drain where efficiencies ranging from 67 to 89% were observed. A powdered mixture of MgCO₃ and CaCO₃ was only 11% effective in treatment of the drainage water due to the slow rate of reaction of MgCO₃. Whilst the active treatment system was capable of treating a large acidity flux (particularly using hydrated lime) it required regular addition of reagent and the dosing of hydrated lime was particularly difficult to control. Future designs of this active treatment system should be automated to prevent adverse aquatic impacts due to overdosing.

Gradient analyses were used to correlatively determine the importance of acid-related variables for littoral macroinvertebrate assemblages. To better ascertain the effects of acidity on macroinvertebrate assemblages we removed sites judged to be affected by other stressors such as agriculture, urbanization and liming. PCA of land use and water chemistry confirmed the presence of an acidity gradient; several acidity variables (e.g. pH and buffering capacity) were strongly correlated with the first PC axis, which explained Ca 32% of the variance in the environmental data. Partial constrained ordination of littoral macroinvertebrate assemblages with water chemistry, after removing the effect of other confounding variables (e.g. land use/type), showed that acidity variables accounted for significant amounts of among-lake variability in assemblage structure. Regression of canonical scores (a metric of community composition) and diversity with pH and alkalinity was used to visually determine ecological breakpoints or threshold values. Five classes were established for pH: pH < 5 (extremely acid), 5 < pH <= 5.6 (very acid), 5.6 < pH <= 6.2 (acid), 6.2 < pH <= 6.8 (weakly acid) and pH > 6.8 (neutral-alkaline). Similarly, three classes were determined for alkalinity/acidity: <0.02, 0.02-0.1 and >0.1 meq/L.