In the mid-20th century, similar to many lakes in the vicinity of Sudbury, Canada, Middle Lake was severely acidified due to nearby smelting operations. However, this lake is of particular interest because it was limed in 1973, and later fertilized as part of a restoration effort. Here, we use paleolimnological methods to track cladoceran assemblage responses to acidification, liming, and subsequent recovery in a ∼250-year lake sediment record. Cladoceran assemblage changes, notably increases in Chydorus brevilabris, coincided with the late 1800s establishment of open-pit ore roasting in the region. As acidification progressed, the Daphnia pulex complex was replaced by the Daphnia longispina complex. At the height of acidification, and with similar timing to the liming, C. brevilabris increased abruptly in relative abundance in the sediment record, followed by a rapid decline. Invertebrate predation was investigated using Bosmina mucro length; however, no significant trends were evident. Our results suggest that complete biological recovery has not occurred. Specifically, species richness (rarefied) is ∼64 % lower after the onset of acidification, and many rare species present prior to the onset of acidification have not yet returned to pre-impact levels despite dispersal events of these rare taxa being observed during contemporary zooplankton monitoring. Factors impeding the complete biological recovery of the cladocerans in Middle Lake may include biotic resistance, ongoing metal contamination, and a warming climate.

In this study, an artificial neural networks (ANN) model was developed to predict the removal of a polycyclic aromatic hydrocarbon (PAH), namely, naphthalene from marine oily wastewater by using UV irradiation. The removal rate was used as model output and simulated as a function of five independent input variables, including fluence rate, salinity, temperature, initial concentration and reaction time. The configuration of the ANN model was optimized as a three-layer feed-forward Levenberg–Marquardt backpropagation network with log-sigmoid and linear transfer functions at the hidden (12 hidden neurons) and output layers, respectively. By considering goodness-of-fit and cross validated predictability, the ANN model was trained to provide good overall agreement with experimental results with a slope of 0.97 and a correlation of determination (R ²) of 0.943. Sensitivity analysis revealed that fluence rate and temperature were the most influential variables, followed by reaction time, salinity and initial concentration. The findings of this study showed that neural network modeling could effectively predict the behavior of the photo-induced PAH degradation process.

The study was aimed at determining whether potentially pathogenic free-living amoebae (FLA) and Legionella pneumophila can be found in lakes serving as a natural cooling system of a power plant. Water samples were collected from five lakes forming the cooling system of the power plants Pątnów and Konin (Poland). The numbers of investigated organisms were determined with the use of a very sensitive molecular method—fluorescence in situ hybridization (FISH). The result of the present study shows that thermally altered aquatic environments provide perfect conditions for the growth of L. pneumophila and amoebae. The bacteria were identified in the biofilm throughout the entire research period and in the subsurface water layer in July and August. Hartmanella sp. and/or Naegleria fowleri were identified in the biofilm throughout the entire research period.

The Wetland Classification and Risk Assessment Index (WCRAI) is based on manifestations of ecological processes in natural wetland ecosystems. The index is hierarchical in structure and is designed to allow identification and rapid assessment at the broadest levels by non wetland experts in different disciplines to manage natural wetlands. From previous studies, landscape ecology has demonstrated the importance of considering landscape context in addition to local site attributes when explaining wetland ecological processes and ecological integrity. The pressures that land uses and activities exert on wetlands generate impacts that affect both the biotic and abiotic characteristics of the surface water column and the surrounding riparian zone. Therefore, human-altered land in a catchment and spatial patterns of surrounding wetlands provide a direct way to measure human impacts and can be correlated with indicators such as water chemistry and biotic variables. The objective of this study was to develop and test the WCRAI so that the index can be used to classify different types of wetlands and to assess their ecological condition (also known as “Eco-status”) under different ecological conditions. The results obtained from the WCRAI were indicative of the integrity of these wetlands when compared to the status of the abiotic and biotic variables measured at each sampling site. From an economical perspective, the WCRAI can play a crucial role in preventing unnecessary degradation of wetlands, hence reducing financial loss through management, restoration, or rehabilitation efforts. The methodology can be applied very easily (due to its simplistic nature) by industry stakeholders to continually monitor these wetlands.

We determined basal levels of cholinesterase (ChE) and carboxylesterase (CbEs; two substrates: α-naphthyl acetate and 4-nitrophenylvalerate) in different tissues of tadpoles and adults of the frog Pseudis paradoxa and evaluated their use as complementary biomarkers of anti-cholinesterase pesticide exposure. ChE and CbEs sensitivity to malaoxon was also evaluated. Adults and tadpoles were collected with sweep net from temporary ponds located in natural riparian forests along the Paraná River (Garay Department, Santa Fe province, Argentina). We found significant differences in B-esterase activities between adults and tadpoles and among different tissues. The in vitro inhibition tests indicated that ChE is more sensitive to inhibition than CbEs. Our results suggest that basal ChE and CbE (α-NA and 4-NPV) activities in different tissues of adult and tadpoles P. paradoxa would be suitable biomarkers of pesticide exposure, and this amphibian species could be used as sentinel in field monitoring.

The samples of natural and iron-modified clinoptilolite (GC, Na-GC, Fe1-GC, and Fe2-GC) were assessed as adsorbent for arsenate removal by batch and column studies. The influences of retention time, pH, adsorbent dosage, and initial arsenate concentration on the arsenate adsorption efficiency were investigated. The experiments demonstrated that Fe1-GC has the highest arsenate removal efficiency with the adsorption capacity of 8.4 μg g⁻¹at equilibrium time of 60 min. Both the Fe1-GC and Fe2-GC removed arsenate effectively over the initial pH range 4–10. Adsorption capacity of Fe1-GC was adequately described by Freundlich isotherm. According to the results of the desorption performance experiments, the Fe1-GC was used six times until arsenic removal efficiency was reduced to 19 %. The adsorption percentage of arsenic increased with the diminish of initial concentration of arsenic and increase of adsorbent dose for all types of clinoptilolite. The column study demonstrated that Fe1-GC was achieved to reduce final arsenate of about 10 μg L⁻¹or below for up to 300 bed volumes in a continuous flow mode. The results of this study show that Fe1-GC can be used as an alternative adsorbent for arsenate removal.

In 1999, the Perm region ranked eighth among Russian regions in terms of technogenic load per unit of area (4.4 t/km²). The situation in the city of Perm is especially unfavorable in ecological terms due to aerial contamination and hydrogenic contamination, because of industrial wastes entering the small rivers that are tributaries of the Kama river. It was revealed that fluvisols of the city of Perm are contaminated by heavy metals of hydrogenic origin because of the unpurified sewage water entering them. The fluvisols of the city of Perm are contaminated by heavy metals of hydrogenic origin because of the unpurified sewage water entering them.Content of HMs in fine earth showed the deficit and excess compared with European Soil Clarke and Local Background. In relation to European Soil Clarkes elements can be divided into three groups: (1) scarce elements forming negative geochemical anomaly, (2) "normal" elements, which does not differ significantly from Clarke, (3) excess elements forming positive geochemical anomaly. Scarce elements include rubidium and arsenic. “Normal” elements are yttrium, gallium, zirconium and lead. Excess elements are nickel, copper, zinc, strontium and chromium. In the fluvisols, the Fe-rohrensteins are formed. Some elements are concentrated in the Fe-rohrensteins, and some others are not concentrated in them or are found in low concentrations. In Fe-rohrensteins the highly active group comprises As, Zn, Ni, Cu, Cr, and Pb; the moderately active one is represented by Sr, Nb, Ga, and Y; and the inert group contains Zr and Rb. The contents of some chemical elements in Fe-rohrensteins are much greater than those in the fine earth. The Pb and Zn contents in Fe-rohrensteins of the soil of small rivers basin are 440 and 890 mg/kg, respectively. In Fe-rohrensteins, the Pb and Zn contents are 42 % and 17 % of their concentrations in fine earth, respectively. Since some part of heavy metals is precipitated at the redox microbarriers around concretions (Fe-rohrensteins), it is removed from the biological cycle.

Evaluation of a field scale agricultural nonpoint source simulation model against field experiment data is an important step that must be considered before a model can be used as a management tool. Field soil water content and metribuzin residue adsorbed in soil profile were intensively monitored and measured by the gravimetric method and the LC-MS/MS method, respectively, for a soybean field plot located at the Asian Institute of Technology, Thailand. The Root Zone Water Quality Model (RZWQM) was evaluated based on laboratory-measured soil hydraulic properties and pesticide residue in Bangkok clay soil. Reasonable agreement exists between the soil water content measured and predicted by RZWQM for 10–20 and 30–40 cm soil depths. The model slightly overestimated the pesticide residue at 0–10 cm soil depth 1 day after application at surface, whereas pesticide residue at 10–20 and 30–40 cm soil depths was in agreement with model acceptance. These results indicate that RZWQM can be used when properly calibrated to predict the movement of water and metribuzin through the soil profile in the tropical zone.

Potential toxic elements (PTEs) concentration was analyzed seasonally in seawater and sediment samples from Tuticorin coast, India. The extent of PTEs contamination in Tuticorin coast has been revealed by measuring the concentrations of iron (Fe), nickel (Ni), zinc (Zn), copper (Cu), cadmium (Cd), and lead (Pb) using inductively coupled plasma mass spectrophotometer (ICP-MS) seasonally. The concentration of all the PTEs in seawater samples was higher in summer and least in spring. The concentration of all the PTEs was significantly different within and among the season except for Zn and Cu. The concentration of PTEs in sediment samples was higher in winter and least in summer seasons. Exceptionally, the concentration of Cd was not significant among and within the seasons. The concentration of the PTEs in seawater and sediment samples exceeded the WHO-recommended limits. The contamination factor (CF) and geoaccumulation index (I gₑₒ) values indicated significant contamination of PTEs in the sediment samples collected in different seasons. Variations in the concentration of PTEs could be due to changes in levels of pollution discharge over time, availability of PTEs for adsorption, as well as variations in the sampling season. The presence of a number of industries surrounding the Tuticorin coast and the release of the effluents from both industries and domestic sources are the main source of pollution at Tuticorin coast and are the prime reasons for the loss of existing diverse ecosystem.

We measured C and N cycling indicators in Appalachian watersheds impacted by mountaintop removal and valley fill (MTR/VF) coal mining, and in nearby forested watersheds. These watersheds include ephemeral, intermittent, and perennial stream reaches, and the length of time since disturbance in the MTR/VF watersheds was 5 to 11 years. In forest soils compared to VF soils, both denitrification enzyme activity (DEA) and basal respiration (BR) were elevated (factor of 6 for DEA and factor of 1.8 for BR expressed on a weight basis) and bulk density was lower. Organic matter (OM) and moisture were higher in the forest soils, which likely contributed to the elevated DEA and BR levels. Evaluation of soils data from our intermittent watersheds as a chronosequence provides some evidence of soil quality (DEA, BR, and soil moisture) improvement over the course of a decade, at least in the top 5 cm. Across the hydrological permanence gradient, sediment DEA was significantly higher (factor of 1.6) and sediment OM was significantly lower in forested than in VF watersheds, whereas sediment BR did not differ between forested and VF watersheds. Dissolved organic carbon (DOC) concentrations were not different in mining-impacted and forested streams, whereas dissolved inorganic carbon (DIC) concentrations and DOC and DIC stable carbon isotopic compositions (δ¹³C) were significantly elevated in VF streams. The δ¹³C-DIC values indicate that carbonate dissolution was a dominant source of dissolved carbon in MTR/VF mining-impacted streams. The disturbance associated with MTR/VF mining significantly impacts C and N processing in soils, stream sediments, and stream water although our data suggests some improvement of soil quality during the first decade of reclamation.