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.

Former mining activities lasting 140 years in the Ducktown Mining District, Tennessee, USA, has contaminated the streams draining the district with acid-mine drainage (AMD). North Potato Creek and its major tributary, Burra Burra Creek, are two of the most heavily AMD-impacted streams in the district. The removal of dissolved metals from the water in these creeks is largely attributable to the sorption of Cu, Zn, Co, Al, and Mn on suspended hydroxide precipitates of Fe. The fraction of trace metals remaining in solution decreases with increasing pH in the sequence Pb < Cu < Zn < Co. The concentration of Fe in solution also decreases with increasing pH due to the formation of ferric hydroxide precipitates which accounted for up to 81.4% by weight of the total suspended sediment. The concentration of suspended sediment substantially decreases as the water of North Potato Creek flows through a large settling basin, where 1.3 (±0.3) x 10⁶ kg/year of trace-metal-laden suspended sediment would be annually deposited. In spite of this attempt to purify it, the water discharged into the river is acidic (pH 3.6) and still contains high concentrations of dissolved trace metals, which would resorb on to suspended sediment and be ultimately transported to a downstream reservoir, Ocoee No. 3 Lake.

Fifteen soil profiles were taken from Ar-Ramtha wastewater treatment plant, 65 km north of Amman. Twelve of them represent soil planted with barley and irrigated with wastewater for the past 2, 5, and 15 years. The remaining three profiles represented a control area that has been only rainfed. Soil samples were collected in four replicates from each depth in each soil profile. Field and laboratory experiments were conducted to study the effect of irrigation with treated wastewater on hydraulic properties of surface and subsurface vertisols. Soil infiltration rate (IR), hydraulic conductivity (HC), and water retention (at 33 kPa and 1.5 MPa) were measured. The application of wastewater for 2, 5, and 15 years reduced soil hydraulic conductivity, whereas the infiltration rate decreased for 2 and 5 years, compared with non-irrigated area. Sites irrigated for 15 years with treated wastewater are characterized by higher percentages of large cracks, therefore revealed the highest infiltration rate. Soil available water changed due to wastewater application in decreasing order of: control (rainfed), 15, 5, 2 years of wastewater application.

Phytoremediation is an in situ, cost-effective potential strategy for cleanup of sites contaminated with trace metals. Selection of plant materials is an important factor for successful field phytoremediation. A field experiment was carried out to evaluate the phytoextraction abilities of six high biomass plants (Vertiveria zizanioides, Dianthus chinensis, Rumex K-1 (Rumex upatientia x R. timschmicus), Rumex crispus, and two populations of Rumex acetosa) in comparison to metal hyperaccumulators (Viola baoshanensis, Sedum alfredii). The paddy fields used in the experiment were contaminated with Pb, Zn, and Cd. Our results indicated that V. baoshanensis accumulated 28 mg kg-¹ Cd and S. alfredii accumulated 6,279 mg kg-¹ Zn (dry weight) in shoots, with bioconcentration factors up to 4.8 and 6.3, respectively. The resulting total extractions of V. baoshanensis and S. alfredii were 0.17 kg ha-¹ for Cd and 32.7 kg ha-¹ for Zn, respectively, with one harvest without any treatment. The phytoextraction rates of V. baoshanensis and S. alfredii for Cd and Zn were 0.88 and 1.15%, respectively. Among the high biomass plants, R. crispus extracted Zn and Cd of 26.8 and 0.16 kg ha-¹, respectively, with one harvest without any treatment, so it could be a candidate species for phytoextraction of Cd and Zn from soil. No plants were proved to have the ability to phytoextract Pb with high efficiency.

A plot-scale, rainfall-simulation study measured edge-of-field pollutant losses from conventional-till, strip-till, and no-till treatments in a burley tobacco production system. The field experiment results show that the conventional-till treatment yielded more total runoff than strip- and no-till treatments. Compared to the conventional-till treatment, both no-till and strip-till reduced the total mass losses of total suspended solids (TSS), total nitrogen (TN), total Kjeldahl nitrogen (TKN), nitrate (NO-N), ammonia (NH₃-N), total phosphorus (TP), orthophosphate (PO₄-P), and the insecticide chlorpyrifos in runoff. Although statistical analyses indicated that there was no significant difference between the no-till and strip-till practices, the no-till practice consistently yielded less edge-of-field pollutant loss than the strip-till practice. This research reinforces the body of knowledge documenting the effectiveness of conservation-tillage practices in reducing edge-of-field pollutant losses.

Sediment cores were collected from two sites (A2 and ZQ) in the Qingdao sea area of the Yellow Sea. Radionuclides ⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁴Th, and ²³⁸U in the cores were measured using HPGe γ spectrometry. The sedimentation rate of the A2 Core using ²¹⁰Pbex and ¹³⁷Cs was 0.665 cm yr-¹, therefore this 32 cm long core represents a 48 year timespan leading to the sampling date in 2001. The mixing layer was restricted to the upper 5 cm as determined from the profile of ²³⁴Th. The uniformity of the activity distributions of ⁴⁰K and ²³⁸U throughout the A2 Core and the activity distributions of ²²⁶Ra, ²²⁸Ra and ²²⁸Th below the mixing layer suggested that no significant oceanographic event or change in sediment material source had occurred during this timespan. The ²¹⁰ Pb was in excess relative to ²²⁶Ra, but ²²⁶Ra was deficient with respect to ²³⁸U in the entire A2 Core, while excess ²³⁴Th and ²²⁸Th were apparent only in the surface 5 cm. Total organic matter (TOM) in Core A2 decreases with depth. The second core, taken to a depth of 14 cm, was from Site ZQ, which is located near Zhanqiao, Qingdao. The variations of the nuclide activity ratios in this core were similar to those in the A2 Core, i.e., the excess ²¹⁰ Pb and ²²⁶Ra deficiency were consistent throughout the core but excess ²²⁸Th was only in the surface to a depth of 2 cm. The ⁴⁰K activity in the ZQ Core fluctuated and showed no real trend with depth. The activities of ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra and ²³⁸U in the entire length of Core ZQ, and ²²⁸Ra and ²²⁸Th from 2 cm to the bottom, were comparable within the uncertainty of measured activity.

The purpose of the present study is to simulate concentrations of ozone and its precursors (NO and NO₂) in an area under the influence of the Candiota coal-fired power station by applying numerical models. The photochemical simulations were conducted during two distinct periods: in summer (from 24 to 26 January 2003) and in winter (from 10 to 12 August, 2004). With the RAMS atmospheric model (Regional Atmospheric Modelling System) we obtained meteorological fields to initialize the CIT photochemical model. The emission data were based on the AP-42 and only compounds emitted during coal burning were considered. The simulated results revealed high ozone levels in warmer periods, being related to high temperatures and water vapor concentrations. The simulated concentrations are located far from the emitting source, favoring reaction and mixing time between precursors to form ozone. Simulated winds of small intensity favored ozone transport, mixing and accumulation in areas far from the emitting source.

Solids and phosphorus found within urban stormwater have the potential to cause environmental damage to ecological systems in receiving waters. The evaluation of these pollutants in urban stormwater is usually undertaken by physico-chemical monitoring programs which sample streamflow for laboratory assessment. In this study, data from two such monitoring programs have been examined for the catchment characteristics which influence solids and phosphorus discharge behaviour and the potential for the use of surrogate indicators to predict streamflow concentrations. The study involved partitioning of the components on the basis of the dissolved and particulate fractions. Investigation of the physical and chemical behaviour of solids and phosphorus by univariate and multivariate data analysis techniques led to the identification of interrelationships among the measured parameters. Thus, using turbidity and conductivity, relationships were developed for suspended and dissolved solids. Similarly, relationships were developed for dissolved and particulate phosphorus using suspended and dissolved solids. These relationships have the potential to enhance rapid generation of vital information from site-based measurements and to reduce the requirements for laboratory-based analysis of indicator concentrations in urban stormwater.

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.