The bioavailability of the metalloid arsenic (As) in paddy soil is controlled by microbial cycling of As and other elements such as iron (Fe) and sulfur (S), which are strongly influenced by water management in paddy fields. In this study, we evaluated how water management affects As bioavailability by growing rice plants in a geogenic As-contaminated soil. We determined As speciation in soil porewater and the diversity of the associated microbial community. Continuous flooding enhanced the release of Fe and As and increased arsenite (As(III)) and methylated As species concentrations in the rice grain compared with aerobic treatment. Total inorganic and organic As in the grain was 84% and 81% lower, respectively, in the aerobic treatment compared with the continuous flooding treatment. The amounts of Fe(III)-reducing bacteria (FeRB) increased in the flooded rhizosphere soil. The abundance of FeRB in the soil correlated with the dissolution of Fe and As. Among the As-transformation genes quantified, the aioA gene for As(III) oxidation and arsM gene for As(III) methylation were most abundant. The arsM copy number correlated positively with the levels of dsrB (dissimilatory (bi) sulfite reductase β-subunit), suggesting that dissimilatory sulfate-reducing bacteria (SRB) may play an important role in dimethylarsenate (DMAs(V)) production in soil. Our results show that decreased populations of rhizosphere FeRB and SRB contributed to a lower bioavailability of As, and decreased production of methylated arsenicals under oxic conditions.

Due to the increasing presence of platinum (Pt) in the environment, the caveat arises to identify its toxic potential in species at risk of being exposed – especially those found in aquatic environments where pollutants tend to accumulate. Comprehensive characterisation of possible adverse effects following exposure of aquatic organisms to Pt remains elusive. To address this, Zebra mussels (Dreissena polymorpha) were exposed to a range of Pt(IV) concentrations (0.1, 1, 10, 100 and 1000 μg/L) for one and four days, respectively, after which bioaccumulation was quantified and compared to alterations in biomarker profiles relevant to metal toxicity i.e. glutathione-S-transferase (GST) and catalase (CAT) activity, lipid peroxidation and metallothionein (MT) induction. Despite pre-conditioning of the tanks, Pt recovery in the exposure media was found to be 36% (0.1 μg/L), 42% (1 μg/L), 47% (10 μg/L), 68% (100 μg/L) and 111% (1000 μg/L) due to biological and non-biological processes. Pt concentrations in dried mussel soft tissue increased with exposure concentrations and were 20–153 times higher compared to quantified Pt concentrations in the exposure media. CAT activity was significantly increased in the tissue of mussels exposed to 0.1–100 μg/L Pt after Day 1 while the lowest effect concentration (LOC) for this response on both Day 1 and Day 4 was 0.1 μg/L. The effect on the GST activity was less pronounced but demonstrated a similar trend. However, enhanced lipid peroxidation was measured in the tissue of mussels exposed to ≥0.1 μg/L on Day 4. Bioaccumulation of Pt was also associated with a concentration-dependent increase in Pt-MT. Although these effects occurred at Pt levels higher than those present in the environment, it indicates that Pt has the ability to cause aberrancies in metal-associated biomarker profiles.

Dissolved organic carbon (DOC) is not only a critical component of global and regional carbon budgets, but also an important precursor for carcinogenic disinfection byproducts (DBP) generated during drinking water disinfection process. The lack of process based watershed scale model for carbon cycling has been a limiting factor impeding effective watershed management to control DOC fluxes to source waters. Here, we integrated terrestrial and aquatic carbon processes into the widely tested Soil and Water Assessment Tool (SWAT) watershed model to enable watershed-scale DOC modeling (referred to as SWAT-DOC hereafter). The modifications to SWAT mainly fall into two groups: (1) DOC production in soils and its transport to aquatic environment by different hydrologic processes, and (2) riverine transformation of DOC and their interactions with particular organic carbon (POC), inorganic carbon and algae (floating and bottom). We tested the new SWAT-DOC model in the Cannonsville watershed, which is part of the New York City (NYC) water supply system, using long-term DOC load data (from 1998 to 2012) derived from 1399 DOC samplings. The calibration and verification results indicate that SWAT-DOC achieved satisfactory performance for both streamflow and DOC at daily and monthly temporal scales. The parameter sensitivity analysis indicates that DOC loads in the Cannonsville watershed are controlled by the DOC production in soils and its transport in both terrestrial and aquatic environments. Further model uncertainty analysis indicates high uncertainties associated with peak DOC loads, which are attributed to underestimation of high streamflows. Therefore, future efforts to enhance SWAT-DOC to better represent runoff generation processes hold promise to further improve DOC load simulation. Overall, the wide use of SWAT and the satisfactory performance of SWAT-DOC make it a useful tool for DOC modeling and mitigation at the watershed scale.

The enrichment factor (EF) is a widely used metric for determining how much the presence of an element in a sampling media has increased relative to average natural abundance because of human activity. Calculation of an EF requires the selection of both a background composition and a reference element, choices that can strongly influence the result of the calculation. Here, it is shown how carefully applied, classical principal component analysis (PCA) examined via biplots can guide the selections of background compositions and reference elements. Elemental data were treated using the centered log ratio (CLR) transformation, and multiple subsets of major and trace elements were examined to gain different perspectives. The methodology was applied to a dataset of elemental soil concentrations from around breccia pipe uranium mines in Arizona, U.S.A., with most samples collected via incremental sampling methodology. Storage of ore at the surface creates the potential for wind dispersal of ore-derived material. Uranium was found to be the best individual tracer of dispersal of ore-derived material to nearby soils, with EF values up to 75. Sulfur, As, Mo, and Cu were also enriched but to lesser degrees. The results demonstrate several practical benefits of a PCA in these situations: (1) the ability to identify one or more elements best suited to distinguish a specific source of enrichment from background composition; (2) understanding how background compositions vary within and between sites; (3) identification of samples containing enriched or anthropogenic materials based upon their integrated, multi-element composition. Calculating the most representative EF values is useful for numerical assessment of enrichment, whether anthropogenic or natural. As shown here, however, the PCA and biplot method provide a visual approach that integrates information from all elements for a given subset of data in a manner that yields geochemical insights beyond the power of the EF.

Nickel is a ubiquitous heavy-metal pollutant in lakes and severely affects aquatic organisms. Aquatic plants are often initially linked to having heavy metal contents and further are proposed as phytoremediation agent to remove heavy metal from water. Although the toxic effects of nickel on aquatic plants are thoroughly explored, the effective investigation to increase Ni tolerance is still in its infancy. The role of rare-earth elements (REEs) in plant resisting heavy-metal pollution has recently received considerable interest. To explore the physiological effects of REEs on Potamogeton crispus under Ni stress, we explored whether or not the additive exposure to low-dose yttrium (Y; 2.5 μM) promotes the polyamine metabolism, antioxidation, and photosynthesis performance of P. crispus under Ni stress values of 0, 50, 100, 150, and 200 μM. Results showed that Y exposure did not influence Ni bioaccumulation in P. crispus. Furthermore, Y exposure alleviated the adverse effects of Ni stress to convergent degrees because Y positively converts putrescine into spermidine and spermine, inhibits oxidative stress, increases the total chlorophyll content, and maximum/potential quantum efficiency of photosystem II. We concluded that low-dose Y can positively regulate polyamine transformation, inhibit oxidative stress, stimulate photosynthesis, and finally promote the resist ability of P. crispus to nickel stress. Thus, REEs have potential to be applied in regulating submerged plant tolerance to aquatic heavy-metal pollution.

4-Nonylphenol (NP) and bisphenol A (BPA) are high-production and high-volume chemicals used to manufacture various commercial products. They are also ubiquitous contaminants that disrupt endocrine systems in wildlife and humans. We collected, from Taiwan cities with the highest food production, and analyzed, using high performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS), 278 food samples for NP and BPA from 11 categories. We found background levels of 100% for NP and 72% for BPA in total samples. High levels of contamination (up to 918 and 49.4 μg/kg) were found in some foods of seafood and animal origin. We used a probabilistic approach to calculate daily dietary dose (Monte Carlo-estimated 95th percentile dietary exposure [MCS 95]) from the Taiwan National Food Consumption database for each sex- and age-specified population. For NP and BPA, the highest average daily dose (ADDs) were in the 4- to 6-year-old group (MCS 95 = 1.57/1.28 and 0.157/0.147 [Male/Female] μg/kg bw/day, respectively), and the lowest ADDs were in the ≥65-year-old group (MCS 95 = 0.674/0.581 and 0.054/0.045 [M/F] μg/kg bw/day, respectively). Based on the European Food Safety Authority (4 μg/kg bw/day for BPA) and Danish Institute of Safety and Toxicology guidelines (5 μg/kg bw/day for NP), the 95th percentile HQ of NP and BPA intake in different sex- and age-specified groups in Taiwan posed no risks through dietary exposure. The intake quantity and concentrations of grains, livestock, and seafood are important variables for the integrated risk of NP and BPA. In conclusion, a combination of multiple and long-term exposure via food consumption should be considered rather than individual endocrine-disrupting chemicals during dietary risk assessment in specific populations.The 95th percentile HQ of NP and BPA intake in different age and sex groups in Taiwan posed no risks through dietary exposure based on probabilistic and sensitive approach.

Although, health and environmental hazards of Ni are ironclad; however, that of Nickle oxide nanoparticles (NiO-NPs) are still obscure. Therefore, impact of NiO-NPs exposure (0, 5, 50, 200, 500 and 1000 mg kg⁻¹ soil) on the earthworm (Eisenia fetida) survival (at 28th day), reproduction (at 56th day), histopathology, ultrastructures, antioxidant enzymes and oxidative DNA damage was appraised in full life cycle study. Lower concentrations of NiO-NPs (5, 50 and 200) did not influence the survival, reproduction and growth rate of adult worms significantly. However, reproduction reduced by 40–50% with 500 and 1000 mg kg⁻¹ exposure, which also induced oxidative stress leading to DNA damage in earthworms. Ultrastructural observation and histology of earthworms exposed to higher NiO-NPs concentrations revealed abnormalities in epithelium layer, microvilli and mitochondria with underlying pathologies of epidermis and muscles, as well as adverse effects on the gut barrier. To the best of our knowledge, this is the first study unveiling the adverse effects of NiO-NPs on a soil invertebrate (Eisenia fetida). Our findings clue towards looking extensively into the risks of NiO-NPs on soil organisms bearing agricultural and environmental significance.

The issue of potential long-term or hereditary effects for both humans and wildlife exposed to low doses (or dose rates) of ionising radiation is a major concern. Chronic exposure to ionising radiation, defined as an exposure over a large fraction of the organism's lifespan or even over several generations, can possibly have consequences in the progeny. Recent work has begun to show that epigenetics plays an important role in adaptation of organisms challenged to environmental stimulae. Changes to so-called epigenetic marks such as histone modifications, DNA methylation and non-coding RNAs result in altered transcriptomes and proteomes, without directly changing the DNA sequence. Moreover, some of these environmentally-induced epigenetic changes tend to persist over generations, and thus, epigenetic modifications are regarded as the conduits for environmental influence on the genome.Here, we review the current knowledge of possible involvement of epigenetics in the cascade of responses resulting from environmental exposure to ionising radiation. In addition, from a comparison of lab and field obtained data, we investigate evidence on radiation-induced changes in the epigenome and in particular the total or locus specific levels of DNA methylation. The challenges for future research and possible use of changes as an early warning (biomarker) of radiosensitivity and individual exposure is discussed. Such a biomarker could be used to detect and better understand the mechanisms of toxic action and inter/intra-species susceptibility to radiation within an environmental risk assessment and management context.

Increasing riverine phosphorus (P) levels in headwaters due to expanded and intensified human activities are worldwide concerns, because P is a well-known limiting nutrient for freshwater eutrophication. Here we adopt the conceptual framework of the SPAtially Referenced Regressions On Watershed attributes (SPARROW) model to describe total phosphorus (TP) sources and transport in a headwater watershed undergoing rapid agricultural expansion in the upper Taihu Lake Basin, China. Our models, which include variables for land cover, river length, runoff depth, and pond density, explain 94% of the spatio-temporal variability in TP loads. Agricultural lands contribute the largest percentage (61%) of the TP loads delivered downstream, followed by forestland (21%) and urban land (18%). Future agricultural expansion to 15% of the total basin area is possible, which could lead to a 50% increase in TP loads. According to our analysis, an average of 24% of the total P export from the watershed landscape was intercepted in ponds. The exported amount was subsequently retained by tributaries and along the mainstem river, accounting for 14% and 43% of their inflowing loads, respectively. The remaining ∼6 tons yr⁻¹ of TP was eventually transported into Tianmu Lake, in Southeastern China. The model identified several sub-catchments as hotspots of TP loss and thus logical sites for targeted management. Our study underscores the significance of agricultural expansion as a factor that can exacerbate headwater TP pollution, highlighting the importance of landscapes to buffer TP losses from sensitive hilly catchments. This also points to a need for an integrated management strategy that considers the spatial-varying P sources and associated transport of TP in precious headwater resources.

The Keban Reservoir, which is the second man-made waterbody in Turkey, has the biggest rainbow trout production in the country. In this study, the impacts of rainbow trout farms on water and sediment chemistry were investigated. Water and sediment samples were taken at distances of 0, 10, 25, 50 and 100 m from the edge of the cages at the three fish farms, and at the respective reference stations. Samples were also taken at 0 m stations and reference stations in the late August when there were no fish in the cages. Physico-chemical variables and trace metals were analysed in all samples. Due to likely high dilution rates and recycling processes in the water column of the reservoir, little changes in the water quality parameters associated with wastes of the fish farms were noticed. When compared with those in the sediment samples at the stations near the edge of cages, the lower concentrations of total phosphorus (TP), total nitrogen (TN), organic matter (OM), total carbon (TC), sulfide (S2−), arsenic (As), cobalt (Co), copper (Cu), manganese (Mn) and zinc (Zn), and higher values of redox potential (Eh) were found at the reference stations. According to organic enrichment classification based on S2− and Eh values, sediments of the three fish farms in the period when there were fish in the cages fell into the oxic category, whereas sediments in the August (no fish farming activity) fell into the normal category. Also, it was found in the August that most of sediment quality parameters at the 0 m stations had close values to those at the reference stations. These results revealed that a three-month period when there were no fish in the cages allows for sediments to return to reference station conditions.