The intensive use of pesticides has increased exponentially in Brazil and worldwide due to the need to meet the food demands of a growing population. If the management/monitoring of the use of pesticides is adequately performed, it would not compromise the expected benefits or have negative effects on the environment as a whole. In order to examine the information available on herbicide use in Brazil and worldwide, this paper presents a review of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and its chemical properties, action on target organisms, environmental fate, and toxicity to non-target organisms. This herbicide is a synthetic auxin used to control broad-leaved weeds, and the action in target organisms is well known. Although 2,4-D has been widely used worldwide, many studies have shown that this herbicide induces alterations in non-target organisms. Therefore, ecotoxicology studies are important to assess the risk the herbicides can be to different ecosystems. Thus, it is advised to use this herbicide and other pesticides with caution.

Decomposition of aquatic plant might generate a significant influence on the receiving water body. In this study, decomposition of emergent aquatic plant (cattail) litter was investigated under different conditions to determine the influencing level of the decomposition process on the water quality. Different litter addition rates (0.1, 0.5, 1.0 g L⁻¹), temperature changes, sediment additions, and kinestates (static and dynamic conditions) were selected as the influencing factors for the decomposition process. The results suggested that the decomposition process could be all accelerated when conducted at a higher litter addition rate, under a cold condition, with sediment addition or on dynamic condition, respectively. Additionally, the maximum ratio of releasing carbon to nitrogen (C/N) was increased when the decomposition process was conducted with a higher litter addition rate, under a cold condition (31.0), with sediment addition (24.6) and on a dynamic condition (28.0), respectively, and the C/N ratios were all higher than that with only 0.5 g L⁻¹ litter addition (24.5), suggesting that lowering of water temperature, sediment addition, and increasing of oxygen might also enhance the C/N. The high C/N released during the decomposition process implied that the cattail litter might be utilized as the potential organic carbon source for nitrogen removal in the CW system.

Nonlinear sorption of substituted phenols (degradation products of several pesticides) onto soils was often observed. This sorption nonlinearity at low solute concentration ranges could result in higher soil organic carbon-water distribution coefficient (K ₒc) values than those predicted by their hydrophobicity (K ₒw). In this study, nonlinear sorption characteristic of four substituted phenols (2,6-dimethylphenol, 2-chlorophenol, 2-nitrophenol, and 2,4-dichlorophenol) onto two agricultural soils was investigated. The sorption nonlinearity gradually approached apparent saturation at low solute activity ranges (e.g., a ᵢ < 0.01). At high a ᵢ ranges, linear sorption was observed. Thus, partition and adsorption of solutes were successfully evaluated by a dual-mode sorption model. The concentrations of substituted phenols in the environment are pretty low (e.g., usually lower than 1 mg/L). According to our results, nonlinear adsorption is dominant in such low concentration ranges in the environment. To predict varied log K ₒc values resulted from nonlinear adsorption, especially for low a ᵢ range, an expanded polyparameter linear free energy relationship (pp-LFER) is established: log K ₒc = [(1.829 ± 0.488) + (3.481 ± 0.462) log a ᵢ)]E+ [(− 4.307 ± 0.466) log a ᵢ]S+ [(− 0.876 ± 0.138) log a ᵢ]A+ [(− 0.086 ± 0.529) + (1.209 ± 0.218) log a ᵢ]B+ (6.280 ± 0.649)V – (6.814 ± 0.917) (E, the excess molar refraction; S, the dipolarity/polarizability parameter; A, the solute H-bond acidity; B, the solute H-bond basicity; and V, the molar volume). This model can provide a better prediction (within 0.3 log unit) than previous models. This study provides essential parameters for predicting and understanding the environmental behavior of substituted phenols in agricultural soils. Graphical Abstract ᅟ

Samples of roots and spatial soils of native Rubus fruticosus L. were collected from the spots positioned at different distances from the copper smelter and city heating plants in the industrial zone of the town of Bor (Serbia) and subjected to chemical analyses in order to determine the content of several heavy metals, and 15 priority polycyclic aromatic hydrocarbons (PAHs). In this study, the results for 9 low and medium molecular weight PAHs (LMW and MMW PAHs) are represented and processed using the calculation of bio-concentration factors and statistical methods such as hierarchical cluster analysis and Pearson’s correlation study with the aim of investigating the plant capabilities for their uptake from the soil and later accumulation into the root tissue, under the hostile circumstances of multiple contamination. The obtained data revealed different accumulation rates for the investigated PAHs and showed that in several cases, the contents of root PAHs were under the strong influence of present contaminants such as soil copper and some soil PAHs, indicating at the same time that R. fruticosus can regulate the processes of LMW and MMW PAHs extraction/accumulation using different mechanisms, depending on the existing environmental circumstances. The used mechanisms could be exploited in phytoremediation methods based not only on the extraction and concentration of PAHs in plant roots but also on PAH degradation or stabilization in the soil. Also, the results of this study confirmed that, except in the case of naphthalene and fluoranthene, there was no PAH pollution, which originated solely from the industrial zone.

Contaminant elution and tracer (CET) tests are one method for characterizing the impact of mass transfer, transformation, and other attenuation processes on contaminant transport and mass removal for subsurface systems. The purpose of the work reported herein is to explore specific well-field configurations for improving CET tests by reducing the influence of preferential flow and surrounding plume effects. Three injection-extraction well configurations were tested for different domain conditions using a three-dimensional numerical model. The three configurations were the traditional configuration with a single pair of injection-extraction wells, modified configuration I with one extraction well located between two injection wells, and modified configuration II with two pairs of injection-extraction couplets (one nested within the other). Elution curves for resident contaminant and breakthrough curves from simulated tracer tests were examined for specific landmarks such as the presence and extent of steady state (relatively high concentrations) and asymptotic (asymptotic decrease to low concentrations) phases, as well as distinct changes in slope. Temporal moment analysis of the breakthrough curves was conducted to evaluate mass recovery. Effective diffusion coefficients were obtained by fitting selected functions to the elution curves. Based on simulation results for a homogeneous domain, full isolation of the inner extraction well from the surrounding plume was obtained for the modified configuration II, whereas the extraction wells are impacted by the surrounding plume for the other two configurations. Therefore, configuration II was used for additional simulations conducted with layered and heterogeneous domains. Tracer test simulations for homogeneous and layered domains indicate 100% mass recovery for the inner extraction well. For the heterogeneous domain, decreasing the distance between the inner injection-extraction well couplet and adjusting the pumping rate distribution between the two extraction wells increased the mass recovery from 69 to 99%.

Currently, the use of nanotechnologies is in rapid expansion, which entails increasing risks of environmental contamination by nanoparticles. Many studies describe the toxic effects on human cells, but little is known about the possible adverse effects on plants. Currently, various nanoparticles are often detected in streams, wastewater, and sewage due to widespread nanoparticle uses. We studied the accumulation and the effect of metal oxide nanoparticles together with their bulk counter particles and soluble metal salts on the growth of a wetland plant species true fox-sedge (Carex vulpina L.). The concentration 100 mg/l of copper nanoparticles significantly affected the growth of the plants, roots characteristics, and content of the photosynthetic pigments in leaves, while the same concentration of iron nanoparticles did not reduced any of the measured items. Using the bulk materials, the effect was very similar.

Oil spills might lead to severe environmental impacts to the affected fauna, disrupting local food webs, and causing mass mortality in many species. However, little is known about long-term impacts of oil spills, or even if such impacts can be detectable after several generations. In this study, we investigate the genetic variability of three freshwater species—Mimagoniates microlepis (Characiformes: Characidae), Scleromystax barbatus (Siluriformes: Callichthyidae), and Phalloceros harpagos (Cyprinodontiformes: Poeciliidae)—in rivers that were affected by a large oil spill in the state of Paraná, southern Brazil, on February of 2001. Samples were obtained from nine different locations, such that rivers that were directly affected by the oil spill could be compared with similar rivers in the same region that were unaffected. A fragment of the cytochrome C oxidase subunit I mitochondrial gene was sequenced from each specimen, and the level of genetic variability was assessed. Based on estimates of haplotype and nucleotide diversity, no impact of the oil spill could be detected in impacted rivers. These results suggest that fish populations in the region showed resilience to the pollutant, such that immigration from other locations was able to reestablish levels of genetic variability comparable to those of unimpacted rivers.

Until recently, there have been only few published reports concerning the use of mangrove macroalgae as biomonitors to assess the estuarine metal contamination. Therefore, the present study was an effort to investigate the biomonitoring of metal contamination using mangrove macroalgae in the tropical Miri estuary of Sarawak, Malaysia. The metal concentrations (Cu, Fe, Mn, and Zn) were determined in the surface sediments, estuarine water, and six dominant macroalgae species that epiphytically grow on mangrove pneumatophores. The results showed that the scheme of metal occurrences in estuarine surface water and sediments was Fe > Mn > Zn > Cu and Fe > Zn > Mn > Cu, respectively. Among the studied metals in algal tissues, irrespective of macroalgal species, the concentration of Fe was found to be the highest. Significant positive correlations were found between Cu and Zn in all macroalgal species (except Caloglossa ogasawaraensis and Dictyota sp.), indicating the common origin of those elements. Concentrations of each of the studied metal in algal tissues varied among macroalgal species, probably because of the differences of structure, age, and growth of thallus among macroalgal species. To our knowledge, this is the first comprehensive report describing the biomonitoring of metal contamination using macroalgae from Malaysian mangrove systems.

Sediments deposited on road surfaces are contaminated with pollutants; the load of pollution increases from coarse to fine particles. When it rains, different fractions of the road-deposited sediments are washed off depending on the rain intensity, the slope of the catchment, and other site-specific factors. This road runoff is often treated using settling processes implemented in different types of manufactured treatment devices. These devices can be tested with well-defined artificial test materials to determine the removal efficiencies of particulate matter in a reproducible manner. However, the suitability of the currently deployed artificial test materials to represent the settling behavior of real runoff particle collectives is largely unknown. In this study, a laboratory method to measure and compare the settling behavior of artificial and real particle collectives with a reproducible particle size composition was developed. The particle collectives were obtained from different road surfaces, fractionated into sieve classes, and then recomposed into a defined particle size distribution that represented the road runoff. The settling velocity was analyzed in a modified settling column setup under constant conditions. The resulting data form a cumulative curve of the settling velocities for both artificial and real particle collectives. The main result from this work is that the tested artificial material and the recomposed real particle collectives have comparable settling behaviors despite different losses on ignition and densities.