The conversion of natural saltmarshes to shrimp aquaculture ponds can potentially influence the biogeochemical cycling of nutrients in coastal wetlands, but its impact on the dynamics of sediment dissimilatory nitrate (NO3−) reduction remains poorly understood. In this study, three sediment NO3− reduction processes including denitrification (DNF), anaerobic ammonium oxidation (ANAMMOX), and dissimilatory NO3− reduction to ammonium (DNRA) were examined simultaneously in a natural saltmarsh and two shrimp culture ponds (5- and 18-year-old) in July and November, using nitrogen (N) isotope-tracing experiments. Our results showed that sediment potential DNF, ANAMMOX and DNRA rates were generally higher in the shrimp culture ponds than the natural saltmarsh in the two seasons. The rates of all three processes generally increased with the age of shrimp ponds, with the magnitude of increase being less pronounced for DNF and ANAMMOX than DNRA. The contribution of DNRA to total NO3− reduction increased significantly following saltmarsh conversion to shrimp ponds, suggesting that DNRA became an increasingly important biogeochemical process under shrimp culture. DNRA competed with DNF and limited reactive N loss to some extent after natural saltmarshes converted to shrimp culture ponds. The results of redundancy analysis revealed that the availability of substrates and sulfides in sediments, rather than the bacteria gene abundance, were the most important factor influencing the NO3− reduction processes. Overall, our findings highlighted that shrimp-aquaculture reclamation may aggravate nitrogen loading in coastal wetlands by promoting the production of bioavailable ammonium.

Modeling for the toxicity of ionic liquids (ILs) is necessary to fill data gaps for untested chemicals and to understand the relevant mechanisms at the molecular level. In order for many researchers to easily predict toxicity and/or develop some prediction model, simple method(s) based on a single parameter should be proposed. Therefore, previously our group developed a comprehensive toxicity prediction model with unified linear free-energy relationship descriptors to address the single parameter for predicting the toxicities, as follows (Cho et al., 2016b).Log 1/toxicity in the unit of mM= (2.254 Ec – 2.545 Sc + 0.646 Ac – 1.471 Bc + 1.650 Vc + 2.917 J+ – 0.201 Ea + 0.418 Va + 0.131 J−) – 0.709.It is considered that the model can calculate the general toxicological effect of ILs in parenthesis, as it was developed on the basis of numerous toxic effects i.e., 58 toxicity testing methods and about 1600 data points. In order to check the hypothesis, the values calculated by the model were correlated with four different datasets from insect cell line (Spodoptera frugiperda 9), earthworm (Eisenia fetida), nematode (Caenorhabditis elegans), and fish (Danio rerio). The results clearly showed that the calculated values are in good agreement with each dataset. In the case of S. frugiperda 9 cells, the calculated parameters were correlated with log1/LC50 values, measured after 24 h and 48 h incubation, in R2 of 0.67 and 0.88, respectively. The R2 values for the earthworm, nematode, and fish were 0.88, 0.96, and 0.94–0.95, respectively. This study confirmed that the comprehensive model can be simply and accurately used to predict toxicity of ILs.

This review evaluates the three dynamic models (biokinetic model: BK, physiologically based pharmacokinetic model: PBPK, and toxicokinetic-toxicodynamic model: TKTD) in our understanding of the key questions in metal ecotoxicology in aquatic systems, i.e., bioaccumulation, transport and toxicity. All the models rely on the first-order kinetics principle of metal uptake and elimination. The BK model basically treats organisms as a single compartment, and is both physiologically and geochemically based. With a good understanding of each kinetic parameter, bioaccumulation of metals in any aquatic organisms can be studied holistically and mechanistically. Modeling efforts are not merely restrained from the prediction of metal accumulation in the tissues, but instead provide the direction of the key processes that need to be addressed. PBPK is more physiologically based since it mainly addresses the transportation, transformation and distribution of metals in the organisms. It can be treated conceptually as a multi-compartmental kinetic model, whereas the physiology is driving the development of any good PBPK model which is no generic for aquatic animals and contaminants. There are now increasingly applications of the PBPK modeling specifically in metal studies, which reveal many important processes that are impossible to be teased out by direct experimental measurements without adequate modeling. TKTD models further focus on metal toxicity in addition to metal bioaccumulation. The TK part links exposure and bioaccumulation, while the TD part links bioaccumulation and toxic effects. The separation of TK and TD makes it possible to model processes, e.g., toxicity modification by environmental factors, interaction between different metals, at both the toxicokinetic and toxicodynamic levels. TKTD models provide a framework for making full use of metal toxicity data, and thus provide more information for environmental risk assessments. Overall, the three models reviewed here will continue to provide guiding principles in our further studies of metal bioaccumulation and toxicity in aquatic organisms.

Agricultural chemicals affect the daily life of food production. However, the abuse of pesticides led to the damage to the environment. Pyraclostrobin (PYR) is commonly used strobilurin fungicide which inhibits fungal respiration through mitochondrial cytochrome-b and c1 inhibition. There is increasing concerns that PYR may adversely impact the environment. Although impacts on ecological receptors have been detailed, little information is available regarding the toxicological impact of PYR on soil microbial community dynamics and functioning. Understanding the potential impact on soil microbial populations is important. The activity of enzymes (urease, dehydrogenase, and β-glucosidase) and diversity of microbial community structure using high-throughput 16S rRNA sequencing were evaluated at different soil-PYR concentrations (0.1, 1.0, and 2.5 mg/kg) over a 48 day exposure period. Urease activity remained stable in general. Pyraclostrobin inhibited dehydrogenase activity during the exposure period. The β-glucosidase activity was inhibited on day 28 and induced on day 48 at 1.0 and 2.5 mg/kg. The genera Gp6, Exiguobacterium, Gp4, and Gemmatimonas were both the dominant genera and significantly changed genera. Pyraclostrobin had different level of influence on soil microbes containg their enzyme activity and community structure. The purpose of the current study was to examine the impact of PYR addition on soil enzymes as an indicator of soil health and to have complementary data on the impact of microbial populations. Furthermore, the study may also be the guide for further rational pesticide selection.

The bacterial communities and ecological contribution of biofilm-leaves of the Vallisneria natans (VN), Hydrilla verticillata (HV) and artificial plant (AP) settled in sediments with different polluted levels of phenanthrene were investigated by high-throughput sequencing in different growth periods. There was no significant difference among the detected Alpha diversity indices based on three classification, attached surface, spiking concentration and incubation time. While Beta diversity analysis assessed by PCoA on operational taxonomic units (OTU) indicated that bacterial community structures were significantly influenced in order of attached surface > incubation time > spiking concentration of phenanthrene in sediment. Moreover, the results of hierarchical dendrograms and heat maps at genus level were consistent with PCoA analysis. We speculated that the weak influence of phenanthrene spiking concentration in sediment might be related to lower concentration and smaller concentration gradient of phenanthrene in leaves. Meanwhile, difference analysis suggested that attached surface was inclined to influence the rare genera up to significant level than incubation time. In general, the results proved that phenanthrene concentrations, submerged macrophytes categories and incubation time did influence the bacterial community of biofilm-leaves. In turn, results also showed a non-negligible ecological contribution of biofilm-leaves in dissipating the phenanthrene in sediments (>13.2%–17.1%) in contrast with rhizosphere remediation (2.5%–3.2% for HV and 9.9%–10.6% for VN).

Bioaccessibility measurements of polycyclic aromatic hydrocarbons (PAHs) in soils are significant for exposure risk assessment. The current physicochemical methods require tedious operation processes, underestimate the actual risks, or are unsuitable for high organic content soils. In this work, an efficient and convenient method based on polydopamine-coated polyethylene sieve plate (PDA@PESP) and hydroxypropyl-β-cyclodextrin (HPCD) was developed to predict the bioaccessibility of PAHs in multi-type soils. The PDA@PESP can be prepared via in situ self-polymerization, allowing to extract PAHs from HPCD solution quantitatively and rapidly. When applied to evaluate the bioaccessibility with PDA@PESP as an adsorption sink and HPCD as a diffusive carrier, the proposed method can significantly improve the extractable fraction of PAHs compared to single HPCD extraction in particular for high organic carbon content soil and high-ring PAHs. The desorption kinetics data indicated that the method can predict the bioaccessible fraction of PAHs. In addition, the method predicted a satisfactory accumulation into earthworms (Eisenia fetida) with a slope statistically approximated to 1. A highly significant linear regression (R2 = 0.95) was also found between the proposed method and Tenax desorption in historically contaminated soils, demonstrating that the method is an efficient and convenient approach for the bioaccessibility prediction of PAHs in soils.

The performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were investigated under 75-day exposure of different Cu(II) concentrations. Cu(II) at 0–5 mg/L had no distinct impact on the chemical oxygen demand (COD) and nitrogen removal, oxygen-uptake rate (OUR), nitrification and denitrification rate, and microbial enzymatic activity. The inhibitory effects of Cu(II) at 10 and 30 mg/L on the nitrogen removal rate, OUR, and microbial enzymatic activity of SBR increased with an increment in operation time due to the Cu(II) biotoxicity and the accumulation of Cu(II) in activated sludge. The changes of microbial reactive oxygen species production, lactate dehydrogenase release, catalase activity and superoxide dismutase activity demonstrated that Cu(II) at 10 and 30 mg/L broke the equilibrium between the oxidation and antioxidation processes in microbial cells and also damaged the cytomembrance integrity, which could affect the COD and nitrogen removal performance and change normal microbial cell morphology. The Cu(II) in the influent could be removed by the microbial absorption and accumulated in the activated sludge under long-term exposure. The microbial community displayed some distinct changes from 0 to 30 mg/L Cu(II). In contrast with 0 mg/L Cu(II), Nitrosomonas, Nitrospira and some denitrifying bacteria obviously decreased in relative abundance under long-term exposure of 10 and 30 mg/L Cu(II).

The Hooghly River (HR) estuary is the first deltaic off-shoot of the perennial and transboundary river, Ganga, India. HR receives industrial and domestic waste along with storm-water run-off from Kolkata city and the adjoining districts. Organic micropollutants (OMPs) have been collectively termed for plasticizers, pharmaceuticals and personal care products, which are extensively consumed and disposed in the waste streams. Hence emerging OMPs were investigated to obtain the first baseline data from the Hooghly riverine sediment (HRS) along urban and suburban transects using gas chromatography mass spectrometry (GC-MS). The concentration range of OMPs in the HRS varied between 3 and 519 ng/g for carbamazepine, 5–407 ng/g for non-steroidal anti-inflammatory drugs (NSAIDs), 2–26 ng/g for musk ketone, 2–84 ng/g for triclosan, 2–199 ng/g for bisphenol A (BPA), 2–422 ng/g for plasticizers (phthalic acid esters (PAEs) and bis (2-ethylhexyl) adipate (DEHA)) and 87–593 ng/g for parabens. Carbamazepine concentration in sediment was an useful marker for untreated wastewater in urban waterways. High concentrations of BPA and PAEs in the suburban industrial corridor together with significant correlation between these two type of OMPs (r2 = 0.5; p < 0.01) likely reflect a common source, possibly associated with the plastic and electronic scrap recycling industries. Among all the categories of OMPs, plasticizers seems to exhibit maximum screening level ecological risk through out the study area.

Size-resolved samples were collected using a 14-stage impactor during four seasons in Zhengzhou and analyzed for 26 elements to calculate the health risks from atmospheric particle-bound metals. High concentrations of heavy metals were observed in ultrafine (10.2 (Ni)–66.9 (Cd) ng m⁻³) or submicrometer (11.4 (Ni)–134 (Pb) ng m⁻³) mode in winter. Two size-dependent models were used to estimate the deposition of inhaled toxic metals in various regions of the human respiratory system. Results show that heavy metals deposited in the alveolar region ranged from 7.6 (As)–375 (Al) ng m⁻³ and were almost concentrated in ultrafine and fine modes. Cd (2.2–8.6) may cause accumulative non-carcinogenic health effects on children, and Cr (1.0 × 10⁻⁴–2.2 × 10⁻⁴) may lead to carcinogenic health risks for nearby residents around the sampling site. The major sources by principal component analysis that contributed to Cr and Cd in ultrafine and fine particles were coal combustion, vehicular and industrial emissions. The atmospheric dry deposition fluxes of Cr and Cd were between 0.7 and 1.9 μg m⁻² day⁻¹ calculated by a multi-step method. From the environmental and public health perspective, environmental agencies must control the emission of heavy metals in the atmosphere.

The gut microbiota is important for maintaining homeostasis of the host. Gut microbes represent the initial site for toxicant processing following dietary exposures to environmental contaminants. The diet is the primary route of exposure to polychlorinated biphenyls (PCBs), which are absorbed via the gut, and subsequently interfere with neurodevelopment and behavior. Developmental exposures to PCBs have been linked to increased risk of neurodevelopmental disorders (NDD), including autism spectrum disorder (ASD), which are also associated with a high prevalence of gastrointestinal (GI) distress and intestinal dysbiosis. We hypothesized that developmental PCB exposure impacts colonization of the gut microbiota, resulting in GI pathophysiology, in a genetically susceptible host. Mouse dams expressing two heritable human mutations (double mutants [DM]) that result in abnormal Ca²⁺ dynamics and produce behavioral deficits (gain of function mutation in the ryanodine receptor 1 [T4826I-RYR1] and a human CGG repeat expansion [170–200 CGG repeats] in the fragile X mental retardation gene 1 [FMR1 premutation]). DM and congenic wild type (WT) controls were exposed to PCBs (0–6 mg/kg/d) in the diet starting 2 weeks before gestation and continuing through postnatal day 21 (P21). Intestinal physiology (Ussing chambers), inflammation (qPCR) and gut microbiome (16S sequencing) studies were performed in offspring mice (P28–P30). Developmental exposure to PCBs in the maternal diet caused significant mucosal barrier defects in ileum and colon (increased secretory state and tight junction permeability) of juvenile DM mice. Furthermore, PCB exposure increased the intestinal inflammatory profile (Il6, Il1β, and Il22), and resulted in dysbiosis of the gut microbiota, including altered β-diversity, in juvenile DM mice developmentally exposed to 1 mg/kg/d PCBs when compared to WT controls. Collectively, these findings demonstrate a novel interaction between PCB exposure and the gut microbiota in a genetically susceptible host that provide novel insight into environmental risk factors for neurodevelopmental disorders.