This study focuses on spatial and temporal nutrient pollution of groundwater in the unconfined sandy aquifers of Kalpitiya peninsula, Sri Lanka, where agricultural activities are intense. The study covers two consecutive dry and rainy seasons during the period from 2008 to 2010. Nitrate is the dominant nutrient pollutant in groundwater. The values of Nitrate-N contents ranged from 0.60 to 212.40 mg/L in the dry seasons and 0.20–148.50 mg/L in rainy seasons. Phosphate in groundwater ranged from 0.20 to 5.70 mg/L in dry seasons and 0.04–10.35 mg/L with few exceptions in rainy seasons. About 50% of the studied water samples had Nitrate-N concentrations above WHO drinking water guideline values both in dry and rainy periods. These high concentrations were recorded from wells in agricultural lands. Although there is a slight decrease in the Nitrate-N concentrations at random in rainy seasons, an increasing trend of average concentrations became evident over the study period as a whole, probably indicating building up of Nitrate-N in groundwater in the vegetable growing areas. The spatial distribution of Nitrate-N too shows a good match of high Nitrate-N bearing zones with vegetable cultivated areas indicating intensive leaching from application of excessive chemical fertilizers. High Nitrate-N zones also showed fairly steady lateral distribution indicating slow lateral mobility of Nitrate-rich groundwater probably due to low hydraulic gradients. Low phosphate concentrations in both groundwater and surface soils either indicates their less use in the area or that the available phosphate is leached and removed from the aquifer water and (sandy) soil solutions and probably adsorbed in clayey deeper horizons. Low concentrations of major cations (especially K, Ca, and Na) indicate less impact on cation concentrations in groundwater by the fertilizer application or sea water intrusions/up-coning.

Constructed wetlands have recently received considerable attention as low cost and efficient means of cleaning up many different types of wastewaters at secondary and tertiary levels. This is an environmentally sound method of wastewater treatment that does not use hazardous chemicals, and is based on the high productivity and nutrient removal capability of the wetland that strongly relies on its intricate ecosystem structure and function. Research work was conducted on a tropical constructed wetland to establish its capability to treat wastewater during the dry season. A comparison of its efficacy with that of conventional wastewater treatment plants was made on the basis of the measured water quality parameters. Temperature, pH, dissolved oxygen, and conductivity were measured in situ. Total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD5), chemical oxygen demand (COD), phosphorus, ammonia, and nitrites were analyzed in the laboratory. Fecal coliforms were enumerated and Escherichia coli counts were determined. The TSS values reduced from a mean of 102 mg/l at the influent point to 16 mg/l at the effluent point, depicting a reduction of 84.3%. Influent TDS averaged 847 mg/l, while the effluent averaged 783 mg/l. Dry season BOD5 levels were reduced from an average of 286 at the inlet point to 11 mg/l at the outlet representing a reduction efficiency of 96.2%. COD levels were reduced from a mean of 2,002.5 to 47.5 mg/l depicting a removal efficiency of 97.6%. Phosphorus was reduced from a mean of 14 to 11 mg/l representing a percentage removal of 21.4%. Levels of ammonia reduced from a mean of 61 at the influent point to 36 mg/l at the effluent point representing a percent reduction of 41.0%. There was a 99.99% reduction for both the fecal coliforms and E. coli counts. Conductivity of wastewater increased from 1.08 to 1.98 mS, while the pH increased from 6.23 at the inlet point to 7.99 at the outlet of the system. Temperature and dissolved oxygen measurements showed a diurnal variation. The dry season wastewater heavy metal concentrations were in the following ranges: Pb (0.7–6.9 ppm), Cr (0.2–0.5 ppm), Zn (0.1–2.3 ppm), Ni (0.1–1.3 ppm) with Cd and Cu not being detected in the wastewater streams. Overall, tropical constructed wetlands are effective in treating wastewater streams and they perform a lot better than the popularly used waste stabilization ponds. This paper recommends that they can be widely used within the tropics.

Radon concentration and gamma activity concentration of naturally occurring radionuclides were determined and presented for two tourist caves (Karaca and Çal caves) in this study. These caves are reported to receive about 77,000 visitors during the summer season in 2007. It was seen that mean radon activity concentrations for the winter and summer seasons for the Karaca cave is 1,023 and 823 Bq/m³ and for the Çal cave is 264 and 473 Bq/m³. Mean ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations are found to be 43, 19, and 262 Bq/kg for the Karaca cave and 31, 27, and 460 Bq/kg for the Çal cave. Doses received by the cave guides due to radon were estimated to be 2.9 mSv/year for the winter season and 2.3 mSv/year for the summer season for the Karaca cave. Same values were estimated for the Çal cave, and the results were found to be 0.6 mSv/year for the winter season and 1.1 mSv/year for the summer season. Annual effective doses received by the visitors in both caves were estimated to be in the order of μSv/year because of the short exposure time comparing the cave guides. Although the reported values are below the recommended values, both groups are exposed to possible radiological risk during their stay inside the cave, since prolonged exposure to high radon concentration has been linked to lung cancer.

The spread of antibiotic-resistant bacteria in the environment is raising serious public health concerns, and manure is being increasingly recognized as a major source of antibiotic-resistant bacteria. In this research, we isolated Escherichia coli and enterococci from manure produced in a Wisconsin, USA family dairy farm to determine their resistance to six representative antibiotics. The average densities for E. coli and enterococci were 6.37(±4.38) × 107 colony formation units (CFU) g−1 and 1.60(±1.57) × 104 CFU g−1, respectively. The E. coli isolates were found to be resistant to cephalothin, ampicillin, tetracycline, and erythromycin. In addition to these four antibiotics, the Enterococcus isolates were also resistant to gentamicin and ciprofloxacin. Additionally, we examined the survival and growth of E. coli and enterococci in dairy manure over a period of ~3 days. While the densities of enterococci remained stable over the study period, the concentrations of E. coli on average increased by 1.5 log10 units. Further tests of the bacterial antibiotic resistance over time showed no significant changes in the prevalence of antibiotic resistance. This result indicated that slightly aged manure could represent a larger source of antibiotic-resistant E. coli than fresh manure and the accumulation of antibiotic-resistant E. coli and enterococci in the agricultural fields must be accounted for in the modeling of the spread of antibiotic-resistant bacteria in the environment.

Diplopods are components of the edaphic fauna, which makes them suitable bioindicators of soil quality. Some characteristics of the fat body of diplopods make it suitable for ecotoxicological studies. This organ, composed of diffuse tissue, fills the body cavity; it presents intense metabolic activity associated with lipid, glycogen, protein, and uric acid storage, being also responsible for storage, neutralization, and excretion of substances that are not useful to the organism. The present study aimed to investigate whether the perivisceral fat body of Rhinocricus padbergi can be used as a target organ in ecotoxicological studies and to identify possible histological and histochemical biomarkers in this organ. Upon examining the perivisceral fat body of individuals of R. padbergi exposed to different concentrations of industrial soil contaminated with polycyclic aromatic hydrocarbons (∑ 2,749.0 mg/kg) and metals (∑ 40,355.8 mg/kg), we have found evidence that this organ is sensitive to environmental pollutants present in the soil. The loss of integrity of the cell boundary associated with cytoplasmatic disorganization and depletion in total proteins, neutral polysaccharides, calcium, and lipids can be considered stress biomarkers for R. padbergi.

A bacterial water quality model (BWQM) was developed and used to evaluate the impacts of cattle farming and climate change on the stream fecal coliform pollution in the Salmon River watershed in south-central British Columbia, Canada. The accuracy of the model simulation was evaluated using the Nash-Sutcliffe coefficient of efficiency (COE). The BWQM simulated the observed field data well, with the values of the COE ranging from 0.76 to 0.78 for the stream flow, from 0.55 to 0.60 for the fecal coliform (FC) concentration, and from 0.85 to 0.89 for the FC loading. The BWQM captured more than 79%, 66%, and 90% variation of the daily stream flow, FC concentration, and FC loading, respectively. The BWQM predicts that between 70% and 80% of the FC were transferred from the cattle farm to the Salmon River through the snowmelt-caused surface runoff during late winter and early spring, with the balance 20% to 30% coming from the soil-lateral flow and the groundwater return flow. The model also indicates that the stream FC concentration is sensitive to the distance of the cattle farm to the Salmon River. The model scenario analysis reveals that the climate change, at an assumed 1°C increment of daily air temperature, results in an increase in the stream FC concentration in the spring, fall, and winter, but there is also a decrease in the summer. The increased air temperature also changes the seasonal pattern of the stream FC concentration. Rainfall can reduce the stream FC concentration and mitigate the impact of the increased air temperature on the stream FC concentration as long as it does not result in a surface runoff or flooding event.

Forebays, small settling basins placed at the inlet of Stormwater Best Management Practices, encourage sedimentation with the intention of pollutant consolidation and capture. Regularly, accumulated sediments are excavated to restore forebay storage volume and to further prevent contamination of downstream waterbodies during large storm events. Disposal measures vary according to the toxicity of sediments. To test for the potential toxicity of forebay spoils, 30 stormwater wetland and wetpond forebays of varying age, size, and upstream landuse were sampled across North Carolina and analyzed for seven metals: cadmium, chromium, copper, iron, lead, nickel, and zinc. Ten of 30 sites were also sampled near the outlet structures for spatial comparison of settled sediment and pollutant presence. The relative toxicity of all sampled sediment metal concentrations was evaluated using existing aquatic health sediment guidelines and US Environmental Protection Agency standards for the land application of biosolids (40 CFR503). Of 30 sites, 17 exceeded sediment guidelines for aquatic health, emphasizing the need for routine forebay sediment removal. However, all samples were less than 40 CFR 503 limits with factors of safety ranging from 2.3 to 28, indicating that land application of forebay sediment is unlikely to pose an environmental threat. Additionally, forebay sediment tended to have lower metal toxicity than sediment collected at the pond or wetland outlet.

Diatoms are good indicators of water quality in lotic systems. Unlike in the temperate region, the effect of substrate on diatom-based water quality assessment in tropical streams is not fully understood. The purpose of this study was to assess the effect of substrate on diatom-based multivariate water quality assessment. Epilithic, epiphytic, epipsammic and epipelic diatom community and water quality sampling was done four times at 10 sites during the dry season (2008 and 2009). Artificial substrates (brick and glasses) were also placed at the sampling sites during this period and sampled after 1 month. Cluster analysis was performed to show the main differences and similarities in community composition amongst substrates sampled and amongst sampling sites. The IndVal method was used to identify indicator species characterising different substrates. Canonical correspondence analyses (CCAs) were performed to relate the structure of diatom communities from different substrates to predictor variables. A gradient of increasing metal and organic pollution, eutrophication and ionic strength was observed from the agricultural/forested area to the urban area. Diatom community structure closely reflected this gradient, with communities from polluted sites (8, 9 and 10) being different from other communities. Polluted sites were associated with such species as Nitzschia palea, Plantago lanceolata, Achnanthes exigua, Caloneis hyaline, Cyclotella meneghiniana, Gomphonema parvulum, Fallacia monoculata, Luticola goeppertiana, Pinnularia microstauron, Pinnularia subcapitata and Sellaphora pupula. Indicator species analysis showed that common diatom species were not restricted to a single substrate, though preference was generally high for natural (especially macrophytes) compared to artificial substrates. Six CCAs corresponding to six substrates performed to relate diatom community structure to simultaneous effects of predictor variables explained ∼50% of the diatom species variance in all cases and roughly separated highly polluted sites from the rest of the sites. This indicates that the results of diatom-based multivariate water quality assessment based on different substrates may be interchangeable. Only one substrate has to be collected at each site for water quality assessment surveys, thus avoiding unnecessary expensive and time-consuming oversampling. Given the limitations of artificial substrates, sampling of natural substrates is highly recommended.

In order to investigate the effects of canopy-dependent processes on throughfall chemistry, comparative studies on the chemical composition of throughfall were carried out in five characteristic forest types of the southeastern United States within Fort Benning Military Installation from January 2002 to August 2003. The concentrations and fluxes of and total organic carbon (TOC), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) were determined in rainfall and throughfall. Seasonal variations in chemical fluxes were also evaluated. Throughfall concentrations of TOC, TKN, and TP in matured pine stand were higher than in rainfall and other forest stands. Throughfall nutrient concentrations in wetland were lowest as compared to rainfall as well as hardwood, mixed, plantation, and pine stands. The average TOC, TKN, and TP concentrations in the matured pine stand were 17.2, 0.74, and 0.057 mg/L, respectively. In wetland stands, average concentrations of TOC, TKN, and TP were 4.0, 0.54, and 0.034 mg/L, respectively. Hardwood stand had the lowest TKN concentration of 0.53 mg/L. Nutrient fluxes were generally higher during the dormant season (November–April) as compared to the growing season (May–October). The highest and lowest TOC fluxes during dormant season were contributed from pine stand (801.7 g/ha) and wetland stand (186.2 g/ha), respectively. Rainfall was the major contributor of TKN fluxes in growing season (32.3 g/ha) as well as in dormant season (34.1 g/ha). Similarly, highest TP flux was produced in mixed stand (2.7 g/ha) during the dormant season. Enrichment ratios of nutrients reveal that, in general, forest stands used up nutrients during growing season and washed off during the dormant season.

Nitrogen fertilizers used in agriculture often cause nitrate leaching towards shallow groundwater, especially in lowland areas where the flat topography minimize the surface run off. In order to introduce good agricultural practices that reduce the amount of nitrate entering the groundwater system, it is important to quantify the kinetic control on nitrate attenuation capacity. With this aim, a series of anaerobic batch experiments, consisting of loamy soils and nitrate-contaminated groundwater, were carried out using acetate and natural dissolved organic matter as electron donors. Acetate was chosen because it is the main intermediate species in many biodegradation pathways of organic compounds, and it is a suitable carbon source for denitrification. Sorption of acetate was also determined, fitting a Langmuir isotherm in both natural and artificially depleted organic matter soils. Experiments were performed in quadruplicate to account for the spatial variability of soil parameters. The geochemical code PHREEQC (version 2) was used to simulate kinetic denitrification using Monod equation, equilibrium Langmuir sorption of acetate, and equilibrium reactions of gas and mineral phases (calcite). The reactive modeling results highlighted a rapid acetate and nitrate mineralization rate, suggesting that the main pathway of nitrate attenuation is through denitrification while calcite acted as a buffer for pH. However, in the absence of acetate, the natural content of organic matter did not allow to complete the denitrification process leading to nitrite accumulation. Reactive modeling is thought to be an efficient and robust tool to quantify the complex biogeochemical reactions which can take place in underground environments.