Pesticide pollution from agricultural field run-off or spray drift has been documented to impact river ecosystems worldwide. However, there is limited data on short- and long-term effects of repeated pulses of pesticide mixtures on biotic assemblages in natural systems. We used reported pesticide application data as input to a hydrological fate and transport model (Soil and Water Assessment Tool) to simulate spatiotemporal dynamics of pesticides mixtures in streams on a daily time-step. We then applied regression models to explore the relationship between macroinvertebrate communities and pesticide dynamics in the Sacramento River watershed of California during 2002–2013. We found that both maximum and average pesticide toxic units were important in determining impacts on macroinvertebrates, and that the compositions of macroinvertebrates trended toward taxa having higher resilience and resistance to pesticide exposure, based on the Species at Risk pesticide (SPEARpesticides) index. Results indicate that risk-assessment efforts can be improved by considering both short- and long-term effects of pesticide mixtures on macroinvertebrate community composition.

Sediment cores and soil samples were taken from nine lakes and their catchments across England with varying degrees of direct human disturbance. Mercury (Hg) analysis demonstrated a range of impacts, many from local sources, resulting from differing historical and contemporary site usage and management. Lakes located in industrially important areas showed clear evidence for early Hg pollution with concentrations in sediments reaching 400–1600 ng g−1 prior to the mid-19th century. Control of inputs resulting from local management practices and a greater than 90% reduction in UK Hg emissions since 1970 were reflected by reduced Hg pollution in some lakes. However, having been a sink for Hg deposition for centuries, polluted catchment soils are now the major Hg source for most lakes and consequently recovery from reduced Hg deposition is being delayed.

Palygorskite (PAL) is a good heavy metal adsorbent due to its high surface area, low cost, and environmentally compatibility. But the natural PAL has limited its adsorption capacity and selectivity. In this study, a cost-effective and readily-generated absorbent, l-threonine-modified palygorskite (L-PAL), was used and its performance for Cu(II) removal in simulated aquaculture wastewater was evaluated. After preparation, L-PAL was characterized by using Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, transmission electron microscopy and thermogravimetric analysis. The impacts of pH, adsorbent dosage, contact time, and initial Cu(II) concentration on the adsorption capacity of L-PAL were examined. The Cu(II) adsorption capacity on L-PAL was enhanced almost 10 times than that of raw PAL. The adsorption isotherms of Cu(II) fit the Langmuir isotherms, and the adsorption kinetics was dominated by the pseudo-second-order model. The thermodynamic parameters at four temperatures were calculated, which indicated that the adsorption was spontaneous and endothermic. The adsorption mechanism involves complexation, chelation, electrostatic attraction, and micro-precipitation. Furthermore, L-PAL is shown to have a high regeneration capacity. These results indicate that L-PAL is a cheap and promising absorbent for Cu(II) removal and hold potential to be used for aquaculture wastewater treatment.

To better understand interaction mechanism of sediment organic matter with hydrophobic organic compounds, sorption of phenanthrene (Phen) and nonylphenol (NP) by bulk sediments and their fractions was investigated. Three surface sediments were selectively fractionated into different organic fractions, including the demineralized carbon (DM), lipid free carbon (LF), lipid (LP), and nonhydrolyzable carbon (NHC) fractions. The structure and microporosity of the isolated fractions were characterized by NMR and CO2 adsorption techniques, and used as sorbents for Phen and NP. The calculated micropore volumes (Vo) and specific surface area (SSA) values are positively related to the concentrations of aromatic C and char for the DM, LF and NHC fractions, suggesting that aromatic moieties and char component significantly contribute to the microporosity. The LF fractions exhibit greater sorption affinity than the DM fractions do, indicating that the presence of LP could block the accessibility of sorption sites for Phen and NP. Significant and positive correlations among log K′FOC values for Phen and NP and aromatic carbon and char contents, and Vo and SSA values suggest the aromatic moieties and microporosity dominate their sorption of HOCs by sediment organic matter (SOM). As the NHC fractions have much stronger sorption than other fractions do, they dominate the overall sorption by the bulk samples. This study indicated that the important roles of aromatic moieties, accessibility, and microporosity in the sorption of HOCs by SOM.

Fluoride, a ubiquitous environmental contaminant, is known to impair testicular functions and fertility; however the underlying mechanisms remain obscure. In this study, we used a rat model to mimic human exposure and sought to investigate the roles of apoptosis and autophagy in testicular toxicity of fluoride. Sprague–Dawley rats were developmentally exposed to 25, 50, or 100 mg/L sodium fluoride (NaF) via drinking water from pre-pregnancy to post-puberty, and then the testes of offspring were excised on postnatal day 56. Our results demonstrated that developmental NaF exposure induced an enhanced testicular apoptosis, as manifested by a series of hallmarks such as caspase-3 activation, chromatin condensation and DNA fragmentation. Further study revealed that fluoride exposure elicited significant elevations in the levels of cell surface death receptor Fas with a parallel increase in cytoplasmic cytochrome c, indicating the involvement of both extrinsic and intrinsic apoptotic pathways. Intriguingly, fluoride treatment also simultaneously increased the number of autophagosomes and the levels of autophagy marker LC3-II but not Beclin1. Unexpectedly, the expression of p62, a substrate that is degraded by autophagy, was also significantly elevated, suggesting that the accumulated autophagosomes resulted from impaired autophagy degradation rather than increased formation. Importantly, these were associated with marked histopathological lesions including spermatogenic failure and germ cell loss, along with severe ultrastructural abnormalities in testes. Taken together, our findings provide deeper insights into roles of excessive apoptosis and defective autophagy in the aggravation of testicular damage, which could contribute to a better understanding of fluoride-induced male reproductive toxicity.

Uptake of Cry toxins by insect natural enemies has rarely been considered and bioaccumulation has not yet been demonstrated. Uptake can be demonstrated by the continued presence of Cry toxin after exposure has stopped and gut contents eliminated. Bioaccumulation can be demonstrated by showing uptake and that the concentration of Cry toxin in the natural enemy exceeds that in its food. We exposed larvae of the aphidophagous predator, Harmonia axyridis, to Cry1Ac and Cry1F through uniform and constant tritrophic exposure via an aphid, Myzus persicae, and looked for toxin presence in the pupae. We repeated the experiment using only Cry1F and tested newly emerged adults. Both Cry toxins were detected in pupae, and Cry1F was detected in recently emerged, unfed adults. Cry1Ac was present 2.05 times and Cry1F 3.09 times higher in predator pupae than in the aphid prey. Uptake and bioaccumulation in the third trophic level might increase the persistence of Cry toxins in the food web and mediate new exposure routes to natural enemies.

The spatial distributions and fates of selected legacy and emerging compounds were investigated and compared in surface sediments sampled along the Adriatic mud-wedge and in deep-sea regions from the southern Adriatic basin. Results indicated that the concentrations of legacy contaminants (PAHs, PCBs and DDTs) and emerging contaminants (tonalide, galaxolide, EHMC, octocrylene, BP3 and NP) ranged from 0.1 to 572 ng g−1 and from <LOD to 40.7 ng g−1, respectively. In general, higher concentrations and estimated burdens were detected in the northern Adriatic, highlighting the importance of the Po River as the major contributor for the inputs of legacy and emerging contaminants to sediments in the Adriatic Sea. Nevertheless, the prevalence of some UV filters and fragrances in the central and southern Adriatic indicates that the proximity to tourist areas and WWTPs discharges seems to affect the distribution of those compounds. The accumulation of contaminants in the deep-sea areas supports the inference that this region may act as an important repository for contaminants within the Adriatic Sea. Estimated annual contaminant accumulation reveals that both, legacy and emerging contaminants accumulate preferentially in the northern Adriatic (40–60% of the total annual contaminant accumulation), where the presence of legacy, and to a lesser extent emerging contaminants, are likely to pose an immediate or long-term hazard to resident biota.

Trace organic contaminants such as pharmaceuticals, personal care products and industrial chemicals are frequently detected in the urban water cycle, including wastewater, surface water and groundwater, as well as drinking water. These also include human metabolites (HMs), which are formed in the human body and then excreted via urine or feces, as well as transformation products (TPs) formed in engineered treatment systems and the aquatic environment. In the current study, the occurrence of HMs as well as their TPs of the anticonvulsants carbamazepine (CBZ) and oxcarbazepine (OXC) were investigated using LC tandem MS in effluents of wastewater treatment plants (WWTPs), surface water and groundwater. Highest concentrations were observed in raw wastewater for 10,11-dihydro-10,11-dihydroxycarbamazepine (DiOHCBZ), 10,11-dihydro-10-hydroxy-cabamazepine (10OHCBZ) and CBZ with concentrations ranging up to 2.7 ± 0.4, 1.7 ± 0.2 and 1.07 ± 0.06 μg L−1, respectively. Predictions of different toxicity endpoints using a Distributed Structure-Searchable Toxicity (DSSTox) expert system query indicated that several HMs and TPs, in particular 9-carboxy-acridine (9-CA-ADIN) and acridone (ADON), may exhibit an increased genotoxicity compared to the parent compound CBZ. As 9-CA-ADIN was also detected in groundwater, a detailed investigation of the genotoxicity of 9-CA-ADIN is warranted. Investigations of an advanced wastewater treatment plant further revealed that the discharge of the investigated compounds into the aquatic environment could be substantially reduced by ozonation followed by granular activated carbon (GAC) filtration.

Polychlorinated dibenzo-p-dioxins (PCDDs) are of global concern due to their persistence, bioaccumulation and toxicity. Although the fate of PCDDs in the environment is determined by their physical-chemical properties, such as aqueous solubility, vapor pressure, octanol/water-, air/water-, and octanol/water-partition coefficients, experimental property data on the entire set of 75 PCDD congeners are limited. The quantitative structure-property relationship (QSPR) approach is applied to predict the properties of all PCDD congeners. Experimental property data available from the literature are correlated against 16 molecular descriptors of five types. Reported and newly developed QSPR models for PCDDs are presented and reviewed. The values calculated by the best QSPRs are further adjusted to satisfy fundamental thermodynamic relationships. Although the single-descriptor models with chlorine number, molar volume, solvent accessible surface area and polarizability are based on good statistical results, these models cannot distinguish among PCDDs having the same chlorine number. The QSPR model based on the hyper-Wiener index of quantum-chemical descriptor gives useful statistical results and is able to distinguish among congeners with the same chlorine number, as well as satisfying thermodynamic relationships. The resulting consistent properties of the 75 PCDD congeners can be used for environmental modeling.

Hydrophobic organic compounds (HOCs) tend to associate with suspended sediment (SPS) in aquatic environments; the composition and grain size of SPS will affect the bioavailability of SPS-associated HOCs. However, the bioavailability of HOCs sorbed on SPS with different compositions and grain sizes is not well understood. In this work, passive dosing devices were made to control the freely dissolved concentration of pyrene, a typical HOC, in the exposure systems. The effect of pyrene associated with amorphous organic carbon (AOC), black carbon (BC), and minerals of SPS with grain sizes of 0–50 μm and 50–100 μm on the immobilization and enzymatic activities of Daphnia magna was investigated to quantify the bioavailability of pyrene sorbed on SPS with different grain sizes and compositions. The results showed that the contribution of AOC-, BC-, and mineral-associated pyrene to the total bioavailability of SPS-associated pyrene was approximately 50%–60%, 10%–29%, and 20%–30%, respectively. The bioavailable fraction of pyrene sorbed on the three components of SPS was ordered as AOC (22.4%–67.3%) > minerals (20.1%–46.0%) > BC (9.11%–16.8%), and the bioavailable fraction sorbed on SPS of 50–100 μm grain size was higher than those of 0–50 μm grain size. This is because the SPS grain size will affect the ingestion of SPS and the SPS composition will affect the desorption of SPS-associated pyrene in Daphnia magna. According to the results obtained in this study, a model has been developed to calculate the bioavailability of HOCs to aquatic organisms in natural waters considering both SPS grain size and composition.