Gold mining is responsible for most Hg pollution in developing countries. The aims of this study were to assess the levels of total Hg (T-Hg) in human hair, fish, water, macrophyte, and sediment samples in the gold mining district of San Martin de Loba, Colombia, as well as to determine fish consumption-based risks for T-Hg ingestion. T-Hg levels were measured by electrothermal atomization and atomic absorption spectroscopy. The overall mean T-Hg level in hair for humans in the mining district of San Martin de Loba was 2.12 μg/g, whereas for the reference site, Chimichagua, Cesar, it was 0.58 μg/g. Mean T-Hg levels were not different when considered within localities belonging to the mining district but differed when the comparison included Chimichagua. T-Hg levels in examined locations were weakly but significantly associated with age and height, as well as with fish consumption, except in San Martin de Loba. High T-Hg concentrations in fish were detected in Pseudoplatystoma magdaleniatum, Caquetaia kraussii, Ageneiosus pardalis, Cyrtocharax magdalenae, and Triportheus magdalenae, whereas the lowest appeared in Prochilodus magdalenae and Hemiancistrus wilsoni. In terms of Hg exposure due to fish consumption, only these last two species offer some guarantee of low risk for Hg-related health problems. Water, floating macrophytes, and sediments from effluents near mining sites also had high Hg values. In mines of San Martin de Loba and Hatillo de Loba, for instance, the geoaccumulation index (Igₑₒ) for sediments reached values greater than 6, indicating extreme pollution. In short, these data support the presence of a high Hg-polluted environment in this mining district, with direct risk for deleterious effects on the health of the mining communities.

Response surface methodology based on Box-Behnken (BBD) design was successfully applied to the optimization in the operating conditions of the electrochemical oxidation of sanitary landfill leachate aimed for making this method feasible for scale up. Landfill leachate was treated in continuous batch-recirculation system, where a dimensional stable anode (DSA©) coated with Ti/TiO₂and RuO₂film oxide were used. The effects of three variables, current density (milliampere per square centimeter), time of treatment (minutes), and supporting electrolyte dosage (moles per liter) upon the total organic carbon removal were evaluated. Optimized conditions were obtained for the highest desirability at 244.11 mA/cm², 41.78 min, and 0.07 mol/L of NaCl and 242.84 mA/cm², 37.07 min, and 0.07 mol/L of Na₂SO₄. Under the optimal conditions, 54.99 % of chemical oxygen demand (COD) and 71.07 ammonia nitrogen (NH₃-N) removal was achieved with NaCl and 45.50 of COD and 62.13 NH₃-N with Na₂SO₄. A new kinetic model predicted obtained from the relation between BBD and the kinetic model was suggested.

The main aim of the present work was to study the overall performance and the fouling behavior of the integrated sequencing batch membrane bioreactor (SBMBR) treating synthetic dye-containing wastewater at different sludge retention times (SRTs) of 10, 40, and 160 days. For this reason, the removal efficiencies of color and chemical oxygen demand (COD) and the membrane fouling rates as well as the main sludge characteristics including extracellular polymeric substances (EPS), soluble microbial products (SMP), particle size distribution (PSD), and apparent viscosity were evaluated during the operation time of three SBMBRs. According to the obtained results, the decolorization efficiency was found to increase with increasing the SRT while the COD removal efficiency was similarly high (94–97 %) in all SBMBRs regardless of SRT change. The rate of rise of transmembrane pressure (TMP) was much lower in the SBMBR operating at SRT of 160 days compared with the two other SBMBRs. Cake development on the membrane surface was recognized as the predominant fouling mechanism in three SBMBRs. Among the stated sludge properties, specific EPS and uniformity coefficient of the particle size distribution were suggested to be the controlling factors of the membrane fouling rate in three SBMBRs. During the operation at prolonged SRT (160 days in this study), better decolorization efficiency and lower biofouling rate were obtained in SBMBR system.

The response of rape (Brassica juncea L.) to different vanadium (V) speciation in rhizosphere soils was investigated in pot experiments using an agricultural soil containing 147 mg V kg⁻¹ supplemented with 0–500 mg V kg⁻¹ of pentavalent V [V(V)] and a mining soil containing 774 mg V kg⁻¹. Tetravalent V [V(IV)] accounted for 76.1 and 85.9 % of total V in the untreated agricultural soil and mining soil, respectively. The proportion of both V(V) and water-extractable V increased with increasing concentrations of V(V) in the agricultural soil. The growth of rape substantially reduced the concentrations of V(V) but not V(IV) in the rhizosphere soil, suggesting that V(V) was actively involved in the soil–rape interaction of V. Both soil V(V) and water-extractable V were negatively related to the total rape biomass, but were positively correlated with the concentration of root V. No such relationships were found for total V and soil V(IV). Together, these results indicate that soil V(V) and water-extractable V might better reflect the toxicity of V in soils than total V and soil V(IV). Rape accumulated V in the sequence: roots > > stem > leaf > seed. As indicated by the remarkably low root bioconcentration factor of V(V) (0.41–7.24 %), rape had a lower ability to accumulate V than other plants reported in the literature (14.6–298 %). Only a small fraction of V in rape roots was translocated to the aboveground organs (the translocation factor was 3.57–46.9 %). No V was detectable in seeds in the soils at 147 and 197 mg V kg⁻¹, and no seed was produced in the soils at higher V concentrations. Thus, the risk of V intake by humans via the consumption of rapeseed-based foods under normal conditions is considered to be lower than that of other plants.

Contaminants in the environment often occur as complex mixtures, and their combined effect may exhibit toxicity to organisms. Risk assessments based on individual components tend to underestimate the effects associated with toxic action of mixtures. Toxicity studies on chemical mixtures are urgently required to assess their potential combined toxicities. The combination index (CI)-isobologram method was used to study chemical interactions to determine the nature of toxicological interactions of two pesticides chlorpyrifos and atrazine and a heavy metal cadmium toward earthworm Eisenia fetida by artificial soil and filter paper acute toxicity tests. The results showed that the binary mixture of chlorpyrifos and atrazine was antagonistic toward E. fetida at all f ₐ levels in an artificial soil test. The combination of atrazine and Cd exhibited a slight degree of synergism throughout the exposure range, while chlorpyrifos plus Cd combination led to dual antagonistic/synergistic behavior. The nature of binary combinations in filter paper displayed opposite interaction to that in the artificial soil test, and the toxicity of ternary mixtures was not significantly synergistic than their binaries. The combination index (CI)-isobologram equation method could determine the interaction types for a series of effect levels of three chemicals in binary and ternary combinations in two types of acute earthworm tests. However, the nature of these interactions was not uniform along the f ₐ level range in any of the two tests. Bioavailability, the nature of toxicological interaction, and the test organism need to be considered for understanding exposures and chemical measures. The synergistic effect for the particular binary combination suggests that a potential risk associated with the co-occurrence of these pollutants may still exist, which may have implications in risk assessment for the terrestrial environment. The combined effects between different contaminants might be influenced by the category of chemical, as well as the bioassay procedures. More studies of combined toxicities among these contaminants in the terrestrial environment should be conducted to identify the mixtures exhibiting synergistic pattern of interactions.

The BCR sequential extraction procedure was compared with EDTA, HCl, and NaNO₃ single extractions for evaluating vanadium bioavailability in alfalfa rhizosphere soil. The amounts of vanadium extracted by these methods were in the following order: BCR (bioavailable V) > EDTA ≈ HCl > NaNO₃. Both correlation analysis and stepwise regression were adopted to illustrate the extractable vanadium between different reagents. The correlation coefficients between extracted vanadium and the vanadium contents in alfalfa roots were R NₐNO₃ = 0.948, R HCₗ = 0.902, R EDTA = 0.816, and R bᵢₒₐᵥₐᵢₗₐbₗₑ V = 0.819. The stepwise multiple regression equation of the NaNO₃ extraction was the most significant at a 95 % confidence interval. The influence of pH, total organic carbon, and cadmium content of soil to vanadium bioavailability were not definite. In summary, both the BCR sequential extraction and the single extraction methods were valid approaches for predicting vanadium bioavailability in alfalfa rhizosphere soil, especially the single extractions.

The application of nitrogen fertilizers leads to various ecological problems such as large amounts of nitrogen runoff loss causing water body eutrophication. The proposal that nitrification inhibitors could be used as nitrogen runoff loss retardants has been suggested in many countries. In this study, simulated artificial rainfall was used to illustrate the effect of the nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate) on nitrogen loss from vegetable fields under combined organic and inorganic nitrogen fertilizer application. The results showed that during the three-time simulated artificial rainfall period, the ammonium nitrogen content in the surface runoff water collected from the DMPP application treatment increased by 1.05, 1.13, and 1.10 times compared to regular organic and inorganic combined fertilization treatment, respectively. In the organic and inorganic combined fertilization with DMPP addition treatment, the nitrate nitrogen content decreased by 38.8, 43.0, and 30.1 % in the three simulated artificial rainfall runoff water, respectively. Besides, the nitrite nitrogen content decreased by 95.4, 96.7, and 94.1 % in the three-time simulated artificial rainfall runoff water, respectively. A robust decline in the nitrate and nitrite nitrogen surface runoff loss could be observed in the treatments after the DMPP addition. The nitrite nitrogen in DMPP addition treatment exhibited a significant low level, which is near to the no fertilizer application treatment. Compared to only organic and inorganic combined fertilizer treatment, the total inorganic nitrogen runoff loss declined by 22.0 to 45.3 % in the organic and inorganic combined fertilizers with DMPP addition treatment. Therefore, DMPP could be used as an effective nitrification inhibitor to control the soil ammonium oxidation in agriculture and decline the nitrogen runoff loss, minimizing the nitrogen transformation risk to the water body and being beneficial for the ecological environment.

The ability to fix carbon and energy in swine wastewater of duckweeds was investigated using Spirodela polyrhiza as the model species. Cultures of S. polyrhiza were grown in dilutions of both original swine wastewater (OSW) and anaerobic digestion effluent (ADE) based on total ammonia nitrogen (TAN). Results showed that elevated concentrations of TAN caused decreased growth, carbon fixation, and energy production rates, particularly just after the first rise in two types of swine wastewater. Also, OSW was more suitable for S. polyrhiza cultivation than ADE. Maximum carbon and energy fixation were achieved at OSW-TAN concentrations of 12.08 and 13.07 mg L⁻¹, respectively. Photosynthetic activity of S. polyrhiza could be inhibited by both nutrient stress (in high-concentration wastewater) and nutrient limitation (in low-concentration wastewater), affecting its growth and ability for carbon-energy fixation.

Enteric viruses are present in aquatic environments due to contamination by raw sewage, even in the absence of fecal coliforms, which are considered to be significant indicators when it comes to microbial water quality assessment. This study investigated the presence of group A rotavirus (RVA) in surface water from a river basin in Minas Gerais, Brazil, assessing the influence of the urbanization, the rainfall, and the microbiological and physico-chemical parameters regarding water quality. Forty-eight surface water samples collected in urbanized and non-urbanized areas, both in dry and rainy periods, were obtained throughout the study. The viral particles were concentrated by adsorption-elution in a negatively charged membrane. Fecal coliforms, as well as physico-chemical water parameters were determined at each point in all collections. The RVA was detected in 62.5 % (30/48) of the water samples through a real-time PCR assay. All the sequenced RVA strains belonged to genotype I1. The RVA was detected in 50.0 % (11/22) of the water samples regarded as being acceptable by current microbiological standards. The presence of the RVA and the viral load were influenced by the collection area (p < 0.05). It was also observed a significant association between the RVA and detecting the turbidity of water (p < 0.05). The collected data showed a high level of contamination in this watershed by the discharge of raw sewage, highlighting the need for urgent measures to improve water quality, ensuring the safe use of this matrix.

Bird feeding is one of the most widespread direct interactions between man and nature, and this has important social and environmental consequences. However, this activity can differ between rural and urban habitats, due to inter alia habitat structure, human behaviour and the composition of wintering bird communities. We counted birds in 156 squares (0.25 km² each) in December 2012 and again in January 2013 in locations in and around 26 towns and cities across Poland (in each urban area, we surveyed 3 squares and also 3 squares in nearby rural areas). At each count, we noted the number of bird feeders, the number of bird feeders with food, the type of feeders, additional food supplies potentially available for birds (bread offered by people, bins) and finally the birds themselves. In winter, urban and rural areas differ in the availability of food offered intentionally and unintentionally to birds by humans. Both types of food availability are higher in urban areas. Our findings suggest that different types of bird feeder support only those species specialized for that particular food type and this relationship is similar in urban and rural areas.