The remediation of four estrogenic endocrine-disrupting compounds (EDCs), estrone (E1), estradiol (E2), ethinylestradiol (EE2) and estriol (E3), was measured in saturated and unsaturated carbonate sand-filled columns dosed with wastewater from a sewage treatment plant. The estrogen equivalency (EEQ) of inlet wastewater was 1.2 ng L⁻¹ and was remediated to an EEQ of 0.5 ng L⁻¹ through the unsaturated carbonate sand-filled columns. The high surface area of carbonate sand and associated high microbial activity may have assisted the degradation of these estrogens. The fully saturated sand columns showed an increase in total estrogenic potency with an EEQ of 2.4 ng L⁻¹, which was double that of the inlet wastewater. There was a significant difference (P < 0.05) in total estrogenic potency between aerobic and anaerobic columns. The breakdown of conjugated estrogens to estrogenic EDCs formed under long residence time and reducing conditions may have been responsible for the increase in the fully saturated columns. This may also be explained by the desorption of previously sorbed estrogenic EDCs. The effect of additional filter materials, such as basalt sediment and coconut fibre, on estrogenic EDC reduction was also tested. None of these amendments provided improvements in estrogen remediation relative to the unamended unsaturated carbonate sand columns. Aerobic carbonate sand filters have good potential to be used as on-site wastewater treatment systems for the reduction of estrogenic EDCs. However, the use of fully saturated sand filters, which are used to promote denitrification, and the loss of nitrogen as N₂ were shown to cause an increase in EEQ. The potential for the accumulation of estrogenic EDCs under anaerobic conditions needs to be considered when designing on-site sand filtration systems required to reduce nitrogen. Furthermore, the accumulation of estrogens under anaerobic conditions such as under soil absorption systems or leachate fields has the potential to contaminate groundwater especially when the water table levels fluctuate.

The rapid development of antibiotic-resistant bacteria (ARB) has been of concern worldwide. In this study, antibiotic resistance genes (ARGs) were investigated in antibiotic-resistant Escherichia coli isolated from surface water samples (rivers, n = 17; Taihu Lake, n = 16) and from human, chicken, swine, and Egretta garzetta sources in the Taihu Basin. E. coli showing resistance to at least five drugs occurred in 31, 67, 58, 27, and 18 % of the isolates from surface water (n = 665), chicken (n = 27), swine (n = 29), human (n = 45), and E. garzetta (n = 15) sources, respectively. The mean multi-antibiotic resistance (MAR) index of surface water samples (0.44) was lower than that of chicken (0.64) and swine (0.57) sources but higher than that of human (0.30) and E. garzetta sources (0.15). Ten tetracycline, four sulfonamide, four quinolone, five β-lactamase, and two streptomycin resistance genes were detected in the corresponding antibiotic-resistant isolates. Most antibiotic-resistant E. coli harbored at least two similar functional ARGs. Int-I was detected in at least 57 % of MAR E. coli isolates. The results of multiple correspondence analysis and Spearman correlation analysis suggest that antibiotic-resistant E. coli in water samples were mainly originated from swine, chicken, and/or human sources. Most of the ARGs detected in E. garzetta sources were prevalent in other sources. These data indicated that human activities may have contributed to the spread of ARB in the aquatic environment.

The variation of five antibiotic resistance genes (ARGs)—tetG, tetW, tetX, sul1, and intI1—in a full-scale municipal wastewater treatment plant with A²O-MBR system was studied. The concentrations of five resistance genes both in influent and in membrane bioreactor (MBR) effluent decreased as sul1 > intI1 > tetX > tetG > tetW, and an abundance of sul1 was statistically higher than three other tetracycline resistance genes (tetG, tetW, and tetX) (p < 0.05). The concentrations of five ARGs in the influent were all higher in spring (median 10⁵.⁸¹–10⁷.³² copies mL⁻¹) than they were in other seasons, and tetW, tetX, and sul1 reached its lowest concentration in autumn (10⁴.⁶¹–10⁶.⁸¹ copies mL⁻¹). The concentration of ARGs in wastewater decreased in the anaerobic effluent and anoxic effluent, but increased in the aerobic effluent, and then sharply declined in the MBR effluent. The reduction of tetW, intI1, and sul1 was all significantly positively correlated with the reduction of 16S ribosomal DNA (rDNA) in the wastewater treatment process (p < 0.01). The concentration of ARGs (copies mg⁻¹) in sludge samples increased along the treatment process, but the abundance of five ARGs (ratio of ARGs to 16S rDNA) remained the same from anaerobic to anoxic to aerobic basins, while an increment ratio in MBR was observed for all ARGs.

In Hokkaido, northern Japan, there are 12 hybrid subsurface constructed wetlands (HSCWs) and most of them are treating high concentrated organic wastewater. One of these systems is an HSCW situated in Embetsu, northern Hokkaido, and it has been in operation since November of 2006 to treat dairy milking parlor wastewater. The system is composed of two vertical flow beds and a horizontal flow bed. The influent and the effluent flow rates and pollutant concentrations and loads were extremely variable. Throughout its 6 years of operation, most of the pollutant removals were decently high. Removal efficiencies for COD, BOD₅, and SS were ranging in the 90 %. Removal efficiencies for TN, NH₄-N, and BOD₅ were improving because of the development of the soil ecosystem and the Phragmites australis community. However, the removal efficiencies of TP were decreasing, presumably because of the declining adsorption ability. The accumulation of TP in the first and the second vertical beds had reached its plateau. Vertical beds had high removal efficiencies for TN, COD, BOD₅, and SS. These high removal efficiencies of the first vertical bed may be caused from the efficient removal of solid material that is deposited as an organic layer of the first vertical bed. High NH₄-N removal efficiencies exerted by the second vertical bed may be due to the recycling of wastewater. In conclusion, the HSCW was working excellently for its 6 years of operation, and it could be concluded that it has not reached its life yet.

The effectiveness of the oxide-rich residue from bauxite refining (red mud) to remove inorganic Hg(II) from aqueous solutions was assessed. The aspects studied comprised the kinetics of the process (t = 1 min–24 h), the effect of pH (3.5–11.5), the interacting effect between salt concentration (0.01–1 M NaNO₃) and pH and the Hg(II) sorption isotherm. Hg leaching from spent red mud was evaluated using the toxicity characteristics leaching procedure (TCLP) method. The sorption of Hg(II) onto red mud was very fast, with most of Hg(II) (97.0–99.7 %) being removed from 0.5–50 μM Hg solutions in few minutes. The kinetic process was best described by Ho’s pseudo-second order equation, pointing to chemisorption as the rate controlling step. Hg(II) sorption efficiency was very high (% removal between 93.9 and 99.8 %) within all the studied pH range (3.5–11.5) and added Hg concentrations (5 and 50 μM), being optimal at pH 5–8 and decreasing slightly at both lowest and highest pH. The effect of background electrolyte concentration suggests specific sorption as the main interaction mechanism between Hg(II) and red mud, but the increasing non-sorbed Hg concentrations at low and high pH for higher electrolyte concentrations also revealed the contribution of an electrostatic component to the process. The sorption isotherm showed the characteristic shape of high affinity sorbents, and it was better described by the Redlich-Peterson and Freundlich equations, which are models that assume sorbent heterogeneity and involvement of more than one mechanism. The estimated Hg(II) sorption capacity from the Langmuir equation (q ₘ ~9 mmol/kg) was comparable to those of some inorganic commercial sorbents but lower than most bio- or specifically designed sorbents. The leachability of retained Hg(II) from spent red mud (0.02, 0.25 and 2.42 mmol Hg/kg sorbed concentration) was low (0.28, 1.15 and 2.23 μmol/kg, respectively) and accounted for 1.2, 0.5 and 0.1 % of previously sorbed Hg, indicating that Hg(II) is tightly bound by red mud once sorbed.

Bioavailability has been used as a key indicator in chemical risk assessment yet poorly quantified risk factor. Worldwide, the framework used to assess potentially contaminated sites is similar, and the decisions are based on threshold contaminant concentration. The uncertainty in the definition and measurement of bioavailability had limited its application to environment risk assessment and remediation. Last ten years have seen major developments in bioavailability research and acceptance. The use of bioavailability in the decision making process as one of the key variables has led to a gradual shift towards a more sophisticated risk-based approach. Now a days, many decision makers and regulatory organisations ‘more readily accept’ this concept. Bioavailability should be the underlying basis for risk assessment and setting remediation goals of those contaminated sites that pose risk to environmental and human health. This paper summarises the potential application of contaminant bioavailability and bioaccessibility to the assessment of sites affected by different contaminants, and the potential for this to be the underlying basis for sustainable risk assessment and remediation in Europe, North America and Australia over the coming decade.

Watershed-specific variables such as sediment particle size distribution, water depth, sedimentation rate, focusing factors, and catchment area to lake area ratio can affect the distribution of trace element contaminants to lakes. The aim of this study was to investigate sources of metals to three headwater lakes and to quantify effects of watershed-specific variables on spatial and temporal trends of trace elements (As, Cd, Co, Cr, Cu, Hg, K, Ni, Pb, Rb, and Zn) in sediments and mercury (Hg) concentrations in fish. Surface sediment and water samples were used to characterize spatial patterns, while sediment cores were collected to portray temporal trends. Historical trends of Hg in northern pike (Esox lucius) were assessed in relation to paleolimnological trends of sediment Hg concentrations. Similarity in timing of sediment peak trace element concentrations for the lakes suggests large-scale, atmospheric sources. The lake with highest catchment area-to-lake area ratio was consistently associated with highest sediment elemental concentrations and displayed significant correlations between increased sediment Hg concentrations and decreased pike tissue concentrations over time. This suggests that catchment area-to-lake area ratio is an important factor influencing the concentration of atmospherically derived contaminants within lake sediments and their transfer through the food web.

The aim of this paper was to assess the influence of diet on the concentrations of total mercury (HgTOT) in the eggs of aquatic birds. Trophic level was determined using stable isotopes (δ¹⁵N, δ¹³C). Analysis was carried out on eggs (laid in 2010–2012) belonging to two species of terns nesting at the River Vistula outlet on the Gulf of Gdansk and on herring gulls nesting both in Gdynia harbour and on the Vistula dam in Wloclawek. The results show that seafood diet causes the highest load of mercury, that which is transferred into terns eggs. The amounts of accumulated mercury obtained were found to be different in the particular egg components with Hgₐₗbᵤₘₑₙ > Hgyₒₗₖ > Hgₘₑₘbᵣₐₙₑ > Hgₛₕₑₗₗ. In the herring gull eggs, three stages of embryo development with varying levels of mercury were determined. It was observed that mercury received from the albumen and yolk was most effectively removed when developing embryo into down.

Agriculture has significantly intensified in Northern China since the 1980s. This intensification has caused a series of simultaneous lake ecological environment problems in this area. However, little is known about the role of agricultural intensification in historical nutrient dynamics and lake eutrophication processes. The Yanghe reservoir, a typical artificial reservoir characterized by high-yield grain production in Northern China, has been suffering from serious eutrophication and water quality deterioration. This study evaluates the effect of agricultural intensification on nutrient retention and source in the sediments using ²¹⁰Pb and ¹³⁷Cs dating techniques combined with stable C and N isotopes (δ¹³C, δ¹⁵N) and total organic carbon/total nitrogen, as well as total nitrogen (TN), total phosphorus (TP), and P fractions. Results suggested that agricultural intensification was keys to the accumulation of nutrients and was a source of organic matter (OM) and N in sediment for the past three decades. N and P pollution started in the 1980s and worsened from the 1990s. Good water quality status and steady sedimentary environment with low nutrient content (mean concentrations of TN and TP were 815 and 387 mg kg⁻¹, respectively) were observed before the 1980s. Sediment OM was primarily derived from aquatic plants, whereas N was primarily derived from soil erosion and aquatic plants. However, water quality began to deteriorate while sediment nutrient content began to increase after the 1980s, with values of 1186 mg kg⁻¹ for TN and 434 mg kg⁻¹ for TP in 1989. Sediment OM was primarily derived from C₃ (sweet potato) and aquatic plants, and the major sources of N were soil erosion, fertilizer, and sewage, which accompany the rapid development of agriculture in the watershed. Following the further growth of grain production and fertilizers, excessive external nutrient loading has resulted in dramatic water quality and ecosystem deterioration since 1990. The increasing rate of TN and TP contents was also augmented during these periods, reaching as high as 2624 and 846 mg kg⁻¹ in surface sediment, respectively. In addition, sources of OM and N in sediment were similar to those in the 1980s, but the contribution of aquatic organic N in sediment has continued to increase (aquatic organic N that accounts for TN increased from 14.5 % before the 1980s to 48 % in 2007). This condition could be attributed to the impact of frequent “water bloom” and recession of aquatic plant due to worsening water pollution.

The decrease of ice cover in the Arctic will lead to an increase of ship traffic in the upcoming decades. Consequently, oil pollution is expected. In this context, the goals of this study were to evaluate the biological impact of marine diesel contamination and, on this basis, to determine analytical tools of interest (biomarkers) for future biomonitoring of diesel spills. Using a 7-day contamination protocol, this study investigated biochemical modulations in the digestive gland of the Iceland scallop (Chlamys islandica). Incorporation of contaminants was verified assessing haemolymph metabolites. Results showed a response of glutathione-S-transferase to contamination suggesting detoxification processes and the suitability of such a tool for diesel spill biomonitoring. The lack of modulation of superoxide dismutase activity and lipid peroxidation suggests no oxidative stress and the unsuitability of these molecular tools for biomonitoring.