Two series of laboratory-scale vertical flow systems (flooded and nonflooded columns) were designed to compare nitrogen removal performance, nitrous oxide emission, and ammonia volatilization under different water levels upon treating diluted digested livestock liquid. In these systems, influent was supplied at three hydraulic loading rates (HLRs of 1.25, 2.5, and 5 cm day⁻¹) during stage 1 and the rates were doubled during stage 2 when the water levels of nonflooded columns were elevated from zero to half the height of the soil column. After hydraulic loading rates doubled, the average removal rates of total nitrogen in flooded columns varied from 1.27 to 2.94 g⁻² day⁻¹ and those in nonflooded columns ranged from 1.23 to 3.88 g⁻² day⁻¹. The T-N removal at an HLR of 10 cm day⁻¹ in the nonflooded column with an elevated water table level had higher efficiency than that in the flooded column, suggesting T-N removal is enhanced in the nonflooded column probably due to the improved coupled nitrification–denitrification process under the elevated water table level condition. On the other hand, there was a significant correlation (r ² = 0.532, p < 0.001) between the N₂O flux and redox potential that mainly corresponded to water levels and HLRs, suggesting anoxic or aerobic conditions stimulate N₂O emission by enhancing the nitrification (nitrification–denitrification) process. In contrast, NH₃ volatilization had a high flux in the anaerobic condition mainly because of flooding. Based on the experimental results, it is hypothesized a nonflooded condition with higher water table level (Eh range of −160 to +260 mV) would be suitable to reduce N₂O emission and NH₃ volatilization peak value by at least half while maintaining relatively efficient nitrogen removal performance.

The concentrations of Pb, Cd, Cr, Mn and Fe were evaluated in leaves, stem and root of the Scirpus americanus and Typha latifolia aquatic macrophytes, which were collected from Tanque Tenorio, an artificial lagoon highly polluted by municipal and industrial wastewater. Some S. americanus and T. latifolia plants were collected from four different sites within Tanque Tenorio. The sites were chosen regarding their proximity with the main channel discharging wastewater into the lagoon. The results showed that S. americanus and T. latifolia have the ability to extract Pb, Cd, Cr, Mn and Fe from their water surroundings; on the whole, the roots presented higher concentrations of heavy metals than the stem and the leaves. The highest accumulation of heavy metals was observed in plants growing at the site near the channel entering the lagoon. S. americanus accumulated more Pb, Cr, Mn and Fe than T. latifolia; Cd concentrations were comparably the same in both species. This study provides information in relation to aquatic plants growing in polluted waters, which accumulate heavy metals. These findings are of interest pertaining to the removal processes for treating aquatic systems with heavy metal content.

Mercury and organic carbon concentrations vary dynamically in streamwater at the Sleepers River Research Watershed in Vermont, USA. Total mercury (THg) concentrations ranged from 0.53 to 93.8 ng/L during a 3-year period of study. The highest mercury (Hg) concentrations occurred slightly before peak flows and were associated with the highest organic carbon (OC) concentrations. Dissolved Hg (DHg) was the dominant form in the upland catchments; particulate Hg (PHg) dominated in the lowland catchments. The concentration of hydrophobic acid (HPOA), the major component of dissolved organic carbon (DOC), explained 41-98% of the variability of DHg concentration while DOC flux explained 68-85% of the variability in DHg flux, indicating both quality and quantity of the DOC substantially influenced the transport and fate of DHg. Particulate organic carbon (POC) concentrations explained 50% of the PHg variability, indicating that POC is an important transport mechanism for PHg. Despite available sources of DHg and wetlands in the upland catchments, dissolved methylmercury (DmeHg) concentrations in streamwaters were below detection limit (0.04 ng/L). PHg and particulate methylmercury (PmeHg) had a strong positive correlation (r ² = 0.84, p < 0.0001), suggesting a common source; likely in-stream or near-stream POC eroded or re-suspended during spring snowmelt and summer storms. Ratios of PmeHg to THg were low and fairly constant despite an apparent higher methylmercury (meHg) production potential in the summer. Methylmercury production in soils and stream sediments was below detection during snowmelt in April and highest in stream sediments (compared to forest and wetland soils) sampled in July. Using the watershed approach, the correlation of the percent of wetland cover to TmeHg concentrations in streamwater indicates that poorly drained wetland soils are a source of meHg and the relatively high concentrations found in stream surface sediments in July indicate these zones are a meHg sink.

This study reports the evaluation of chemical composition of a Black Vistula and White Vistula streams' waters taking into consideration both geological conditions of the stream's catchment area and different water' level related to seasonal variations in particular catchment ecosystem (high stage: beginning of the vegetation period; medium stage: vegetation period; low stage: final time of vegetation period). The complex data matrix (744 observations), obtained by the determination of major inorganic analytes (Cl⁻, NO₃ ⁻, SO₄ ²⁻, NH₄ ⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺) in water samples by ion chromatography was treated by linear discriminant analysis and non-parametrical testing. In case of both streams obtained results indicate presence of two discriminant functions (DFs). The data variance explained by DFs is as follows: Black Vistula stream--first DF: 93.5%, second DF: 6.5%; White Vistula stream--first DF: 66.3%, second DF: 33.7%. In case of Black Vistula stream first DF allows distinction of medium, high and low waterstage related samples while second DF between high/low and medium water stage related samples. In case of White Vistula stream first DF allowed to distinguish between medium/high and low water stage related samples while second DF between medium and high water level samples. In case of both streams, the most informative DFs were related to geological conditions of investigated catchments (contents of Cl⁻, Na⁺, K⁺, Mg²⁺, Ca²⁺, SO₄ ²⁻), while the second to nutrient biocycle (mainly NH₄ ⁺ and NO₃ ⁻) related to slope's exposition and inclination.

The arsenic bioavailability in the bed sediments from the Anllóns River (NW Spain) has been assessed by using several analytical approaches. A six-step sequential fractionation was compared to three general availability tests: the Toxicity Characteristic Leaching Procedure (TCLP) extraction, which estimates the leaching potential of As and its effect on the survival of microorganisms (Vibrio fischeri), an extraction with 1 M HCl extraction, which estimates the bioavailability to higher plants, and a physiologically based extraction test (PBET), which estimates the bioavailability to superior animals. Arsenic was found to be mainly associated to the least mobile fractions: bound to Fe-Al oxides and in the residual phase. Among the three single extractants considered, the PBET extracted the highest As concentrations (1-11% of the total As). The TCLP extracts showed toxicity to Vibrio fischeri whereas for the plants evaluated, aqueous extracts did not show adverse effects.

The use of three inorganic materials as potential immobilizers of metals in soils has been studied by monitoring metal availability by EDTA extraction, the Simple Bioaccessibility Extraction Test (SBET) and extraction with a mixture of organic acids (OA). The SBET test was the most suitable for risk assessment in soils of recreational areas. The materials were a 4A-type zeolite, tri-calcium phosphate and 'slovakite', a synthetic sorbent developed for remediation of metal-polluted soils. Adsorption/desorption experiments of metals by the isolated materials showed that all materials caused a strong retention of metals from solutions, with negligible release by dilution. When added to soils of three parks, zeolite and, to a much lesser extent, slovakite caused some increase in soil pH. Despite this increase of pH, zeolite is often the least effective amendment for decreasing metal availability estimated by any method, and even sometimes seems to cause some increase, as well as an increase of soil electrical conductivity. In contrast, slovakite causes a decrease of available metals as estimated by EDTA and SBET, but by SBET the effect seems to be steadily reduced after the first samplings, so that after 300 days the metals extracted by this method are very similar to the data for the blanks. Despite the differences in pseudo-total metal contents, few differences are noticeable among parks. In general, these amendments are scarcely efficient in the case of neutral urban soils like those studied here. Other techniques are needed for controlling and, eventually, decreasing metal pollution hazard in soils of recreational areas.

The direct spectrophotometric analysis of aqueous nitrates is a simple analytical procedure but prone to interferences. A twelve-month study of the Preakness Brook in Wayne Township, New Jersey demonstrated that two wavelength, three wavelength, and second derivative calculation methods provide very different results from the same ultraviolet absorption spectrum. On average, the two wavelength and second derivative methods yielded the same concentration at each sample point over the entire study period. These methods provided concentration results closest to those obtained by ion chromatography and significantly lower than the three wavelength computation method. The degree of variation between the different computation methods was not consistent as it rose with increasing absorbances at wavelengths associated with interfering compounds. This variation was especially pronounced between May and August.

The theoretical basis of the proposed technique is the cumulative variation of ¹³⁷Cs measurements' squared-differences between a reference and other sites. The change of the cumulative squared-differences with distance from the reference site is referred to as the point cumulative semivariogram (PCSV), which provides appropriate measure of cumulative similarity. Inspection of individual experimental PCSV provides local interpretation about the ¹³⁷Cs radioactivity concentration around each site, whereas collective inspections provide possibility for grouping similar sites and hence identifying homogeneous sub-areas within the study area. It is also possible to prepare ¹³⁷Cs radioactivity concentration maps based on pre-specified distances in each experimental PCSV, which lead to similarity levels. Such maps provide appreciation of ¹³⁷Cs radioactivity concentration regional dependence in Keban Dam Lake, Turkey. Apart from the individual PCSV interpretations, the whole lake is divided into four distinctive classes.

Investigation of pollution sources and their impacts on ecosystems is important, not only for better understanding the responses of an ecosystem to pollutants, but also for making practicable prevention and control plans. In this study, ecological quality of three areas which received different source pollutants in Shanghai coast were evaluated and compared in four seasons using Shannon-Wiener index (H'), a benthic diversity index as an indicator of ecological quality of coastal waters. The genotoxicity and physical-chemical variables of water samples were also analyzed. The H' value indicated the ecological quality of Shanghai coastal waters was seriously impacted, and the ecological quality of two areas receiving waste discharges were significantly worse than that of the natural protection zone but not significantly different in four seasons. The positive genotoxic response was detected in most samples from two discharge zones but not detected in the samples from the natural protection zone. However, no significant difference was observed in water quality variables in the different coastal areas. Our study suggested that the point source pollution had significantly contributed to the genotoxicity of the coastal waters and impaired benthic assemblages, while the deterioration of ecological quality status was also critically impacted by the stressors from other sources.

Acute toxicity of Pb to the water flea; (Daphnia sp) and Copepod, (Cyclop sp) both important component of zooplankton diet of fish was determined by static assay. A positive relationship between percentage mortality and exposure concentration was found in all tests. Mean 24-h LC50, 48-h LC50 and 96-h LC50 values were 2.51 ± 0.0.04 mg l⁻¹, 1.88 ± 0.06 mg l⁻¹ and 1.65 ± 0.19 mg l⁻¹ for Daphnia spp and 3.11 ± 0.03 mg l⁻¹, 2.97 ± 0.05 mg l⁻¹ and 2.61 ± 0.09 mg l⁻¹ for Cyclop spp, respectively. For all tested species did the LC50 values decrease with time; the decrease was more marked for Daphnia spp. Observed symptoms include spiral movement followed by change of body colour to white and rapid disintegration of the skin. The Daphnia spp. appear to be more sensitive to Pb poison than Cyclop spp. The results showed that concentrations of Lead (Pb) in excess of 0.19 mg l⁻¹ and 0.30 mg l⁻¹ can be potentially harmful to Daphnia magna and Cyclop spp respectively.