The internal loading of P is reported to be the main factor initiating algal blooms. However, there are only a few reports on the dynamic variation of labile P in the sediment and overlying water during the decomposition of algal. In addition, the widely perceived relationship between labile P and Fe was not supported by in situ obtained values in freshwater. Consequently, the in situ simultaneous measurement of diffusion gradients in thin-film techniques (DGT) was applied on a large scale to detect the mechanisms of labile P and Fe in a typical shallow lake (Lake Hongze). The newly developed ZrO-DGT and ZrO-Chelex DGT were combined to obtain the concentration of labile P and Fe. Results showed that decomposition of algal might be the main contributor for the concentration dots and peaks of labile P in sediment profiles, as well as for the high values on the horizontal heterogeneity index of labile P at the depth of 0–30 mm of the sediment. Moreover, there existed significant difference between the apparent diffusion fluxes of labile P and Fe across the sediment–water interface which obtained from June sampling and October sampling. The results of apparent diffusion flux in two periods indicated the sediments changed from “sink” to “source” for labile P, especially at Sites 4–8, 10, 13–14, and 18. However, the role of the labile Fe has no significantly variation in the values of the diffusion flux. This phenomenon also contributed to the poor relationship between labile P and Fe in the sediment which obtained from the October sampling. Accordingly, we conclude that algal decomposition might be essential for internal loading of P in this aquatic ecosystem, and that also be the reason for vicious circle of algal occurrence in the following year in the center of Lake Hongze.

Freshwater ecosystems are threatened by multiple anthropogenic stressors, which might be differentiated into two types: those that reduce biological activity at all concentrations (toxic contaminants), and those that subsidize biological activity at low concentrations and reduce it at high concentrations (assimilable contaminants). When occurring in mixtures, these contaminants can have either antagonistic, neutral or synergistic effects; but little is known on their joint effects. We assessed the interaction effects of a mixture of assimilable and toxic contaminants on stream biofilms in a manipulative experiment using artificial streams, and following a factorial design with three nutrient levels (low, medium or high) and either presence or absence of a mixture of emerging contaminants (ciprofloxacin, erythromycin, diclofenac, methylparaben, and sulfamethoxazole). We measured biofilm biomass, basal fluorescence, gross primary production and community respiration. Our initial hypotheses were that biofilm biomass and activity would: increase with medium nutrient concentrations (subsidy effect), but decrease with high nutrient concentrations (stress effect) (i); decrease with emerging contaminants, with the minimum decrease at medium nutrient concentrations (antagonistic interaction between nutrients subsidy and stress by emerging contaminants) and the maximum decrease at high nutrient concentrations (synergistic interaction between nutrients and emerging contaminants stress) (ii). All the measured variables responded linearly to the available nutrients, with no toxic effect at high nutrient concentrations. Emerging contaminants only caused weak toxic effects in some of the measured variables, and only after 3–4 weeks of exposure. Therefore, only antagonistic interactions were observed between nutrients and emerging contaminants, as medium and high nutrient concentrations partly compensated the harmful effects of emerging contaminants during the first weeks of the experiment. Our results show that contaminants with a subsidy effect can alleviate the effects of toxic contaminants, and that long-term experiments are required to detect stress effects of emerging contaminants at environmentally relevant concentrations.

Coastal urban infrastructures are proliferating across the world, but knowledge about their emergent impacts is still limited. Here, we provide evidence that urban artificial reefs have a high potential to accumulate the diverse forms of litter originating from anthropogenic activities around cities. We test the hypothesis that the structural complexity of urban breakwaters, when compared with adjacent natural rocky intertidal habitats, is a driver of anthropogenic litter accumulation. We determined litter abundances at seven sites (cities) and estimated the structural complexity in both urban breakwaters and adjacent natural habitats from northern to central Chile, spanning a latitudinal gradient of ∼15° (18°S to 33°S). Anthropogenic litter density was significantly higher in coastal breakwaters when compared to natural habitats (∼15.1 items m−2 on artificial reefs versus 7.4 items m−2 in natural habitats) at all study sites, a pattern that was temporally persistent. Different litter categories were more abundant on the artificial reefs than in natural habitats, with local human population density and breakwater extension contributing to increase the probabilities of litter occurrence by ∼10%. In addition, structural complexity was about two-fold higher on artificial reefs, with anthropogenic litter density being highest at intermediate levels of structural complexity. Therefore, the spatial structure characteristic of artificial reefs seems to enhance anthropogenic litter accumulation, also leading to higher residence time and degradation potential. Our study highlights the interaction between coastal urban habitat modification by establishment of artificial reefs, and pollution. This emergent phenomenon is an important issue to be considered in future management plans and the engineering of coastal ecosystems.

In our earlier work, Tigriopus japonicus were subjected to different mercuric chloride treatments (0–50 μg/L in the seawater) for five generations (F0–F4), and they were subsequently resumed under clean environments for one generation, i.e., F5. Accumulative effects were hypothesized to participate in mercury (Hg) multigenerational toxicity, however phenotypic plasticity could be responsible for metal resistance in this copepod against the long term exposure. Here, we specifically investigated the proteome profiles in the F0, F2, and F5 copepods of the control and 50 μg/L metal treatment, respectively, so as to elucidate the action mechanisms for Hg toxicity/tolerance in T. japonicus under the long term exposure. Functional enrichment analysis showed that a quite different proteomic response was observed in F5 compared with F0 and F2. Namely, the vast majority of enrichments were correlated with the down-regulated proteins in F0 and F2, whereas the enrichments for F5 were mostly attributable to the up-regulated proteins, suggesting that different mechanisms are responsible for Hg toxicity and tolerance (i.e., phenotypic plasticity). Hg toxicity prohibited many proteins in F0 and F2 which are related to several critical processes/pathways, e.g., protein translation, macromolecule metabolic process, DNA replication, cell cycle, cuticle organization, vitellogenesis, etc. In F5, many up-regulated proteins were enriched into compensatory systems, such as carbohydrate metabolism, myosin reorganizations, and stress-related defense pathway. Notably, glycolysis (an oxygen-independent pathway) was enhanced for energy allocation into metal detoxification and tolerance. Taken together, proteomics provides novel mechanistic insights into phenotypic plasticity used by T. japonicus when challenged with cumulative effects due to Hg multigenerational toxicity.

As of November 2014, the Korean Ministry of Environment (KME) has been forecasting the concentration of particulate matter with diameters ≤ 10 μm (PM10) classified into four grades: low (PM10 ≤ 30 μg m−3), moderate (30 < PM10 ≤ 80 μg m−3), high (80 < PM10 ≤ 150 μg m−3), and very high (PM10 > 150 μg m−3). The KME operational center generates PM10 forecasts using statistical and chemistry-transport models, but the overall performance and the hit rate for the four PM10 grades has not previously been evaluated. To provide a statistical reference for the current air quality forecasting system, we have developed a neural network model based on the synoptic patterns of several meteorological fields such as geopotential height, air temperature, relative humidity, and wind. Hindcast of the four PM10 grades in Seoul, Korea was performed for the cold seasons (October–March) of 2001–2014 when the high and very high PM10 grades are frequently observed. Because synoptic patterns of the meteorological fields are distinctive for each PM10 grade, these fields were adopted and quantified as predictors in the form of cosine similarities to train the neural network model. Using these predictors in conjunction with the PM10 concentration in Seoul from the day before prediction as an additional predictor, an overall hit rate of 69% was achieved; the hit rates for the low, moderate, high, and very high PM10 grades were 33%, 83%, 45%, and 33%, respectively. Our findings also suggest that the synoptic patterns of meteorological variables are reliable predictors for the identification of the favorable conditions for each PM10 grade, as well as for the transboundary transport of PM10 from China. This evaluation of PM10 predictability can be reliably used as a statistical reference and further, complement to the current air quality forecasting system.

Concentration and spatial distribution of six phthalic acid esters (PAEs) and eight phenols in sediments of urban rivers, namely the Xi River (XR) and Pu River (PR) in Shenyang city, Northeast China were investigated and the ecological risk of these target pollutants was assessed based on the risk quotient (RQ) approach. Target PAEs and phenols were detected in most of sediment samples collected from the XR and PR. The concentrations of total PAEs in sediments varied from 22.4 to 369 μg/g dw in the XR and 3.71–46.9 μg/g dw in the PR. The levels of phenols ranged from 2.72 to 106 μg/g dw in the XR and 0.811–25.0 μg/g dw in the PR, respectively. The dominant pollutants in both XR and PR were DEHP, phenol and 4-methylphnol. The sampling locations XR1-3 in the XR suffered severe contamination from PAEs and phenols. The sites PR1 and PR6 were heavily polluted by phenols and PAEs, respectively. Almost all target PAEs and phenolic compounds in sediment of the XR exhibited medium or high ecological risk to organisms and the ecological risk in the PR mainly originated from PEAs, phenol and 4-methylphenol. These results would provide guidance for individual pollutant control and indicate that it is imperative to take some effective measures to reduce the pollution of those contaminants.

Manufactured nanoparticles (MNP) rapidly undergo aging processes once released from products. Silver sulfide (Ag2S) is the major transformation product formed during the wastewater treatment process for Ag-MNP. We examined toxicogenomic responses of pristine Ag-MNP, sulfidized Ag-MNP (sAg-MNP), and AgNO3 to a model soil organism, Caenorhabditis elegans. Transcriptomic profiling of nematodes which were exposed at the EC30 for reproduction for AgNO3, Ag-MNP, and sAg-MNP resulted in 571 differentially expressed genes. We independently verified expression of 4 genes (numr-1, rol-8, col-158, and grl-20) using qRT-PCR. Only 11% of differentially expressed genes were common among the three treatments. Gene ontology enrichment analysis also revealed that Ag-MNP and sAg-MNP had distinct toxicity mechanisms and did not share any of the biological processes. The processes most affected by Ag-MNP relate to metabolism, while those processes most affected by sAg-MNP relate to molting and the cuticle, and the most impacted processes for AgNO3 exposed nematodes was stress related. Additionally, as observed from qRT-PCR and mutant experiments, the responses to sAg-MNP were distinct from AgNO3 while some of the effects of pristine MNP were similar to AgNO3, suggesting that effects from Ag-MNP is partially due to dissolved silver ions.

Heavy metals (Cr, Co, Ni, As, Cd, and Pb) can be bound to PM adversely affecting human health. Quantifying the source impacts on heavy metals can provide source-specific estimates of the heavy metal health risk (HMHR) to guide effective development of strategies to reduce such risks from exposure to heavy metals in PM2.5 (particulate matter (PM) with aerodynamic diameter less than or equal to 2.5 μm). In this study, a method combining Multilinear Engine 2 (ME2) and a risk assessment model is developed to more effectively quantify source contributions to HMHR, including heavy metal non-cancer risk (non-HMCR) and cancer risk (HMCR). The combined model (called ME2-HMHR) has two steps: step1, source contributions to heavy metals are estimated by employing the ME2 model; step2, the source contributions in step 1 are introduced into the risk assessment model to calculate the source contributions to HMHR. The approach was applied to Huzou, China and five significant sources were identified. Soil dust is the largest source of non-HMCR. For HMCR, the source contributions of soil dust, coal combustion, cement dust, vehicle, and secondary sources are 1.0 × 10−4, 3.7 × 10−5, 2.7 × 10−6, 1.6 × 10−6 and 1.9 × 10−9, respectively. The soil dust is the largest contributor to HMCR, being driven by the high impact of soil dust on PM2.5 and the abundance of heavy metals in soil dust.

Ecological communities are increasingly exposed to natural and anthropogenic stressors. While the effects of individual stressors have been broadly investigated, there is growing evidence that multiple stressors are frequently encountered underscoring the need to examine interactive effects. Pesticides and infectious diseases are two common stressors that regularly occur together in nature. Given the documented lethal and sublethal effects of each stressor on individuals, there is the potential for interactive effects that alter disease outcomes and pesticide toxicity. Using larval wood frogs (Lithobates sylvaticus), we examined the reciprocal interaction between insecticides (carbaryl and thiamethoxam) and the viral pathogen ranavirus by testing whether: (1) prior ranavirus infection influences pesticide toxicity and (2) sublethal pesticide exposure increases susceptibility to and transmission of ranavirus. We found that prior infection with ranavirus increased pesticide toxicity; median lethal concentration (LC50) estimates were reduced by 72 and 55% for carbaryl and thiamethoxam, respectively. Importantly, LC50 estimates were reduced to concentrations found in natural systems. This is the first demonstration that an infection can alter pesticide toxicity. We also found that prior pesticide exposure exacerbated disease-induced mortality by increasing mortality rates, but effects on infection prevalence and transmission of the pathogen were minimal. Collectively, our results underscore the importance of incorporating complexity (i.e. order and timing of exposures) into research examining the interactions between natural and anthropogenic stressors. Given the environmental heterogeneity present in nature, such research will provide a more comprehensive understanding of how stressors affect wildlife.

The effects of four types of dissolved organic matters (DOM) on the bioconcentration of perfluoroalkyl substances (PFASs) in Chironomus plumosus larvae have been studied. The PFASs included perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), and perfluorododecanoic acid (PFDoA). The DOM included humic acid (HA), fulvic acid (FA), tannic acid (TA), and a protein, peptone (PEP), and their concentrations ranged from 0 to 50 mg L−1. The results showed that, upon bioconcentration equilibrium, the body burdens of longer perfluoroalkyl chain PFASs (PFOS, PFDA, PFUnA and PFDoA) decreased with PEP and HA concentrations while increased with FA and TA concentrations. When FA and TA concentrations increased from 0 to 50 mg L−1, body burdens of these PFASs increased by 7.5%–148.8% and 5.7%–37.1%, respectively. However, the DOM had no significant impact on the body burdens of shorter perfluoroalkyl chain PFASs (PFOA and PFNA). All of the four types of DOM lowered not only the uptake rate constants (ku) of PFASs due to the decrease of freely dissolved PFAS concentrations, but also the elimination rate constants (ke) due to the inhibition effect of DOM on the PFAS elimination from the larvae. The reduction in the two constants varied with both DOM and PFAS types. In the presence of PEP and HA with larger molecular weights, the ku values decreased more than ke, leading to the decreased body burdens of longer perfluoroalkyl chain PFASs. As for FA and TA with smaller molecular weights, the ke values decreased more than ku, resulting in increased body burdens of longer perfluoroalkyl chain PFASs. This study suggests that the effects of DOM on PFAS bioconcentration depend not only on the concentration but also on the molecule weight of DOM, which should be considered in the bioavailability assessment of PFASs.