The effect of microplastics (MP) exposure on the chironomid species Chironomus riparius Meigen, 1804 was investigated using the OECD sediment and water toxicity test. Chironomid larvae were exposed to an environmentally relevant low microplastics concentration (LC), a high microplastics concentration (HC) and a control (C). The LC was 0.007 g m⁻² on the water surface + 2 g m⁻³ in the water column + 8 g m⁻² in the sediment, and the HC was 10 X higher than this for each exposure. The size of the majority of the manufactured microplastic pellets varied between 20 and 100 μm. The MP mixture consisted of: polyethylene-terephtalate (PET), polystyrene (PS), polyvinyl-chloride (PVC) and polyamide (PA) in a ratio of 45%: 15%: 20%: 20%, respectively, for the sediment exposure; 100% polyethylene for the water column exposure; and 50% polyethylene: 50% polypropylene for the water surface exposure. Different endpoints were monitored, including morphological changes in the mandibles and mentums of 4th instar larvae, morphological changes in the wings, mortality, emergence ratio, and developmental time. A geometric morphometric analysis showed a tendency toward widening of the wings, elongation of the mentums and changing the shape of the mandibles in specimens exposed to both concentrations of microplastics. The development time of C. riparius was significantly prolonged by the MP treatment: 13.8 ± 0.5; 14.4 ± 0.6; and 15.3 ± 0.4 days (mean ± SD) in the C, LC, and HC, respectively. This study indicates that even environmentally relevant concentrations of MP mixture have a negative influence on C. riparius, especially at the larval stage.

Bees are considered as important providers of ecosystem services, acting via pollination process in crops and native plants, and contributing significantly to the maintenance of biodiversity. However, the decrease of bee's population has been observed worldwide and besides other factors, this collapse is also related to the extensive use of pesticides. In this sense, studies involving the assessment of adverse effects and the uptake of pesticides by bees are of great concern. This work presents an analytical method for the determination of the insecticide abamectin and the fungicide difenoconazole in the stingless bee Melipona scutellaris exposed via oral and topic to endpoints concentrations of active ingredients (a.i.) alone and in commercial formulations and the discussion about its mortality and uptake. For this purpose, QuEChERS (Quick, Easy, Cheap, Efficient, Rugged and Safe) acetate modified method was used for extraction and pesticides were determined by LC-MS/MS. The validation parameters have included: a linear range between 0.01 and 1.00 μg mL⁻¹; and LOD and LOQ of 0.038 and 0.076 μg g⁻¹ for abamectin and difenoconazole, respectively. The uptake of tested pesticides via oral and topic was verified by the accumulation in adult forager bees, mainly when the commercial product was tested. Mortality was observed to be higher in oral exposure than in topic tests for both pesticides. For abamectin in a commercial formulation (a.i.) no differences were observed for oral or topic exposure. On the other hand, for difenoconazole, topic exposure had demonstrated higher accumulation in bees, according to the increase of received dose. Through the results, uptake and the possible consequences of bioaccumulated pesticides are also discussed and can contribute to the knowledge about the risks involving the exposure of bees to these compounds.

The neonicotinoid imidacloprid (IMI) is one of the most extensively applied neuro-active insecticides worldwide and continues to enter surface waters in many countries despite a recent ban for outdoor use in the EU. Yet little is known about ecotoxicological effects on non-target benthic freshwater species exposed to environmentally relevant concentrations of IMI and its marketed products. The aim of the present study was to narrow this gap by assessing effects of pure IMI and its commercial formulation Confidor® on the aquatic oligochaete Lumbriculus variegatus, a key species in freshwater sediments. To this end, we determined dose-response relationships in 24 h toxicity tests, bioconcentration during 24 h and 5 d of exposure to 0.1, 1 and 10 μg IMI L⁻¹, and physiological stress responses by measuring glutathione S-transferase, glutathione reductase and catalase activity in the same conditions. Maximum neonicotinoid concentrations reported from the field were lethal to L. variegatus within 24 h (LC₅₀ of 65 and 88 μg IMI L⁻¹ in pure form and as active ingredient of Confidor®, respectively). At sub-lethal exposure concentrations, tissue content of IMI significantly increased with exposure time. The observed bioconcentration factors (BCFs) were far above the water octanol coefficient (KOW), indicating a potentially large underestimation of IMI bioaccumulation when based on KOW. Activities of biotransformation and antioxidant enzymes indicated attempts of L. variegatus to counter xenobiotic-triggered oxidative stress to very low IMI and Confidor® concentrations. Together, our data add significantly to growing evidence that the continued proliferation of neonicotinoids require increased efforts in environmental risk assessment, especially in view of species-specific differences in sensitivities to the insecticide and possibly to additives of commercial formulations.

Microplastics (MPs), as a new type of environmental pollutant, pose a serious threat to soil ecosystems. The activities of soil extracellular enzymes produced by microorganisms are the potential sensitive indicators of soil quality. However, little is known about the response mechanism of enzyme activities toward MPs on a long-term scale. Moreover, information on differences in enzyme activities across different soil aggregates is lacking. In this study, 150 days of incubation experiments and soil aggregate fractionation were combined to investigate the influence of MPs on extracellular enzyme activities in soil. 28% concentration of polyethylene with size 100 μm was adopted in the treatments added with MPs. The results show that MPs inhibited enzyme activities through changing soil nutritional substrates and physicochemical properties or through adsorption. Moreover, MPs competed with soil microorganisms for physicochemical niches to reduce microbial activity and eventually, extracellular enzyme activity. Enzyme activities in different aggregate-size fractions responded differently to the MPs exposure. The catalase in the coarse particulate fraction and phenol oxidase and β-glucosidase in the micro-aggregate fraction exerted the greatest response. With comparison, urease, manganese peroxidase, and laccase activities showed the greatest responses in the non-aggregated silt and clay fraction. These observations are believed to stem from differences in the key factors determining the enzyme activities in different aggregate-size fractions.The inhibitory pathway of microplastics on activities of extracellular enzymes in soil varies significantly across different aggregate fractions.

Aquatic macrophytes play a significant role in nutrients removal in constructed wetlands, yet nutrients could be re-released due to plant debris decomposition. In this study, Myriophyllum aquaticum was used as a model plant debris and three debris biomass levels of 3 g, 9 g dry biomass, and 20 g fresh biomass (D3, D9, and F20, respectively) were used to simulate 120-d plant debris decomposition in a sediment-water system. The biomass first-order decomposition rate constants of D3, D9, and F20 treatments were 0.0058, 0.0117, and 0.0201 d⁻¹, respectively with no significant difference of decomposition rate among three mass groups (p > 0.05). Plant debris decomposition decreased nitrate and total nitrogen concentrations but increased ammonium, organic nitrogen, and dissolved organic carbon (DOC) concentrations in overlying water. The parallel factor analysis confirms that three components of DOC in overlying water changed over decomposition time. Emission fluxes of methane and nitrous oxide in the plant debris treatments were several to thousands of times higher than the control group within the initial 0–45 d, which was mainly attributed to DOC released from the plant debris. Plant debris decomposition can affect the gas emission fluxes for relatively shorter time (30–60 d) than water quality (>120 d). The 16S rRNA, nirK, nirS and hazA gene abundance increased in the early stage for plant debris treatments, and then decreased to the end of 120-d incubation time while ammonia monooxygenase α-subunit A gene abundance of ammonia-oxidizing archaea and bacteria had no large variations during the entire decay time compared with no plant debris treatment. The results demonstrate that decomposition of M. aquaticum debris could affect greenhouse gas emission fluxes and microbial gene abundance in the sediment-water system besides overlying water quality.

Textile wastewater contains a huge amount of azo dyes and heavy metals and catastrophically deteriorates the agricultural field by affecting its phyisco-chemical/biological and nutritional properties when directly drained to agricultural lands without any treatment. Recently, biogenic copper nanoparticles (CuNPs) have gained considerable attention for photocatalytic degradation of wastewater pollutants owing to their unique physico-chemical and biological properties, low cost and environmental sustainability. The current study reports the synthesis of CuNPs by a native copper-resistant bacterial strain Escherichia sp. SINT7 and evaluation of the photocatalytic activity of the biogenic CuNPs for azo dye degradation and treatment of textile effluents. Scanning electron microscopy and transmission electron microscopy revealed the spherical shape of biogenic CuNPs with particle size ranging from 22.33 to 39 nm. Moreover, X-ray diffraction data revealed that the CuNPs have spherical crystalline shapes with an average particle size of 28.55 nm. FTIR spectra showed the presence of coating proteins involved in the stabilization of nanomaterial. Azo dye degradation assays indicated that CuNPs decolorized congo red (97.07%), malachite green (90.55%), direct blue-1 (88.42%) and reactive black-5 (83.61%) at a dye concentration of 25 mg L⁻¹ after 5 h of sunlight exposure. However, at 100 mg L⁻¹ dye concentration, the degradation percentage was found to be 83.90%, 31.08%, 62.32% and 76.84% for congo red, malachite green, direct blue-1 and reactive black-5, respectively. Treatment of textile effluents with CuNPs resulted in a significant reduction in pH, electrical conductivity, turbidity, total suspended solids, total dissolved solids, hardness, chlorides and sulfates as compared to the non-treated samples. Thus, the promising dye detoxification and textile effluent recycling efficiency of biogenic CuNPs may lead to the development of eco-friendly and cost-efficient process for large-scale wastewater treatment.

Pollution by marine litter is raising major concerns due to its potential impact on marine biodiversity and, above all, on endangered mega-fauna species, such as cetaceans and sea turtles. The density and distribution of marine litter and mega-fauna have been traditionally monitored through observer-based methods, yet the advent of new technologies has introduced aerial photography as an alternative monitoring method. However, to integrate results produced by different monitoring techniques and consider the photographic method a viable alternative, this ‘new’ methodology must be validated. This study aims to compare observations obtained from the concurrent application of observer-based and photographic methods during aerial surveys. To do so, a Partenavia P-68 aircraft equipped with an RGB sensor was used to monitor the waters off the Spanish Mediterranean coast along 12 transects (941 km). Over 10000 images were collected and checked manually by a photo-interpreter to detect potential targets, which were classified as floating marine macro-litter, mega-fauna and seabirds. The two methods allowed the detection of items from the three categories and proved equally effective for the detection of cetaceans, sea turtles and large fish on the sea surface. However, the photographic method was more effective for floating litter detection and the observer-based method was more effective for seabird detection. These results provide the first validation of the use of aerial photography to monitor floating litter and mega-fauna over the marine surface.

Constructed wetland effectiveness is often assessed by measuring reductions of contaminant concentrations in influent versus departing effluent, but this can be complicated by fluctuations in contaminant content/chemistry and hydrology. We assessed effectiveness of a constructed wetland at protecting downstream biota from accumulating elevated metal concentrations—particularly copper and zinc in effluents from a nuclear materials processing facility. Contaminants distributed throughout a constructed wetland system and two reference wetlands were assessed using six dragonfly nymph genera (Anax, Erythemis, Libellula, Pachydiplax, Tramea, and Plathemis) as biomonitors. Additionally, the crayfish, Cambarus latimanus, were analyzed from the receiving and two reference streams. Concentrations of Cu, Zn, Pb, Mn, Cr, Cd, and Al were evaluated in 597 dragonfly nymph and 149 crayfish whole-body composite samples. Dragonfly genera varied substantially in metal accumulation and the ability to identify elevated metal levels throughout components of the constructed wetland. Genera more closely associated with bottom sediments tended to accumulate higher levels of metals with Libellula, Pachydiplax, and Erythemis often accumulating highest concentrations and differing most among sites. This, combined with their abundance and broad distributions make the latter two species suitable candidates as biomonitors for constructed wetlands. As expected, dragonfly nymphs accumulated higher metal concentrations in the constructed wetland than reference sites. However, dragonfly nymphs often accumulated as high of metal concentrations downstream as upstream of the water treatment cells. Moreover, crayfish from the receiving stream near the constructed wetland accumulated substantially higher Cu concentrations than from downstream locations or reference streams. Despite reducing metal concentrations at base flow and maintaining regulatory compliance, metal fluxes from the wetland were sufficient to increase accumulation in downstream biota. Future work should evaluate the causes of downstream accumulation as the next step necessary to develop plans to improve the metal sequestering efficiency of the wetland under variable flow regimes.

Gradual contamination of agricultural land with copper (Cu), due to the indiscriminate uses of fungicides and pesticides, and the discharge of industrial waste to the environment, poses a high threat for soil degradation and consequently food crop production. In this study, we combined morphological, physiological and biochemical assays to investigate the mechanisms underlying acetate-mediated Cu toxicity tolerance in lentil. Results demonstrated that high dose of Cu (3.0 mM CuSO₄. 5H₂O) reduced seedling growth and chlorophyll content, while augmenting Cu contents in both roots and shoots, and increasing oxidative damage in lentil plants through disruption of the antioxidant defense. Principle component analysis clearly indicated that Cu accumulation and increased oxidative damage were the key factors for Cu toxicity in lentil seedlings. However, acetate pretreatment reduced Cu accumulation in roots and shoots, increased proline content and improved the responses of antioxidant defense (e.g. increased catalase and glutathione-S-transferase activities, and improved action of glutathione-ascorbate metabolic pathway). As a result, excess Cu-induced oxidative damage was reduced, and seedling growth was improved under Cu stress conditions, indicating the role of acetate in alleviating Cu toxicity in lentil seedlings. Taken together, exogenous acetate application reduced Cu accumulation in lentil roots and shoots and mitigated oxidative damage by activating the antioxidant defense, which were the major determinants for alleviating Cu toxicity in lentil seedlings. Our findings provide mechanistic insights into the protective roles of acetate in mitigating Cu toxicity in lentil, and suggest that application of acetate could be a novel and economical strategy for the management of heavy metal toxicity and accumulation in crops.

Bioremediation has gained global prominence as an effective method for treating hydrocarbon-contaminated drill mud waste (HCDW). However, the problem of low nutrient content, bioavailability and microbial presence remain largely unresolved. In this study, the synergistic effects of compost, cow bile and bacterial culture on the degradation rate of HCDW was investigated. A homogenized HCDW sample (80 kg) obtained from 25 different drill mud tanks was divided into 20 portions (4 kg each) and each adjusted to 1.4% nitrogen content + 20 ml cow bile (i.e., basic treatment). Pure cultures of Brevibacterium casei (Bc) and Bacillus zhangzhouensi (Bz) and their mixture (BcBz) were subsequently added to 12 of the amended HCDW (basic) to undergo a 6-week incubation. A portion of the unamended HCDW (2 kg) was used as control. Initial pH, electrical conductivity and surface tension values of the HCDW were 8.83, 2.34 mS/cm and 36.5 mN/m, respectively. Corresponding values for total petroleum hydrocarbon (TPH), total nitrogen and total plate count bacteria were 165 g/kg, 0.04% and 4.4 × 10² cfu/ml. The treatments led to a substantial reduction in TPH (p < 0.05) while the control had no significant effect (p > 0.05). TPH reduction after the experimental period occurred in the order: basic + BcBz (99.7%) > basic + Bz (99.5%) > basic + Bc (99.2%) > basic (95.2%) > control (0.06%). Multiple regression analysis revealed significant effect of total plate count, pH, CN ratio and electrical conductivity (R² = 0.87, p = 0.05) on the degradation of TPH in the HCDW. The study demonstrates strong interactive effects of compost, cow bile and bacteria culture on the remediation of HCDW, which can be applied to boost the efficiency of the bioremediation technique.