A comprehensive measurements of aerosol optical depth (AOD), particulate matter (PM) and black carbon (BC) mass concentrations have been carried out over Patiala, a semi-urban site in northwest India during October 2008 to September 2010. The measured aerosol data was incorporated in an aerosol optical model to estimate various aerosol optical parameters, which were subsequently used for radiative forcing estimation. The measured AOD at 500 nm (AOD500) shows a significant seasonal variability, with maximum value of 0.81 during post-monsoon (PoM) and minimum of 0.56 during winter season. The Ångström exponent (α) has higher values (i.e. more fine-mode fraction) during the PoM/winter periods, and lower (i.e. more coarse-mode fraction) during pre-monsoon (PrM). In contrast, turbidity coefficient (β) exhibits an opposite trend to α during the study period. BC mass concentration varies from 2.8 to 13.9 μg m⁻³ (mean: 6.5 ± 3.2 μg m⁻³) during the entire study period, with higher concentrations during PoM/winter and lower during PrM/monsoon seasons. The average single scattering albedo (SSA at 500 nm) values are 0.70, 0.72, 0.82 and 0.75 during PoM, winter, PrM and monsoon seasons, respectively. However, inter-seasonal and inter-annual variability in measured aerosol parameters are statistically insignificant at Patiala. These results suggest strong changes in emission sources, aerosol composition, meteorological parameters as well as transport of aerosols over the station. Higher values of AOD, α and BC, along with lower SSA during PoM season are attributed to agriculture biomass burning emissions over and around the station. The estimated aerosol radiative forcing within the atmosphere is positive (i.e. warming) during all the seasons with higher values (∼60 Wm⁻²) during PoM–08/PoM–09 and lower (∼40 Wm⁻²) during winter–09/PrM–10. The present study highlights the role of BC aerosols from agricultural biomass burning emissions during post-monsoon season for atmospheric warming at Patiala.

Diesel exhaust particles (DEP) and their ultrafine fraction (UFP) are known to induce cardiovascular effects in exposed subjects. The mechanisms leading to these outcomes are still under investigation, but the activation of respiratory endothelium is likely to be involved. Particles translocation through the air-blood barrier and the release of mediators from the exposed epithelium have been suggested to participate in the process. Here we used a conditioned media in vitro model to investigate the role of epithelial-released mediators in the endothelial cells activation.Diesel UFP were sampled from a Euro 4 vehicle run over a chassis dyno and lung epithelial BEAS-2B cells were exposed for 20 h (dose 5 μg/cm2). The exposure media were collected and used for endothelial HPMEC-ST1.6R cells treatment for 24 h. The processes related to oxidative stress and inflammation were investigated in the epithelial cells, accordingly to the present knowledge on DEP toxicity. The release of IL-6 and VEGF was significantly augmented in diesel exposed cells. In endothelial cells, VCAM-1 and ICAM-1 adhesion molecules levels were increased after exposure to the conditioned media. By interfering with IL-6 binding to its endothelial receptor, we demonstrate the role of this interleukin in inducing the endothelial response.

The Catskill Mountains have been adversely impacted by decades of acid deposition, however, since the early 1990s, levels have decreased sharply as a result of decreases in emissions of sulfur dioxide and nitrogen oxides. This study examines trends in acid deposition, stream-water chemistry, and soil chemistry in the southeastern Catskill Mountains. We measured significant reductions in acid deposition and improvement in stream-water quality in 5 streams included in this study from 1992 to 2014. The largest, most significant trends were for sulfate (SO42−) concentrations (mean trend of −2.5 μeq L−1 yr−1); hydrogen ion (H+) and inorganic monomeric aluminum (Alim) also decreased significantly (mean trends of −0.3 μeq L−1 yr−1 for H+ and −0.1 μeq L−1 yr−1 for Alim for the 3 most acidic sites). Acid neutralizing capacity (ANC) increased by a mean of 0.65 μeq L−1 yr−1 for all 5 sites, which was 4 fold less than the decrease in SO42− concentrations. These upward trends in ANC were limited by coincident decreases in base cations (−1.3 μeq L−1 yr−1 for calcium + magnesium). No significant trends were detected in stream-water nitrate (NO3−) concentrations despite significant decreasing trends in NO3− wet deposition. We measured no recovery in soil chemistry which we attributed to an initially low soil buffering capacity that has been further depleted by decades of acid deposition. Tightly coupled decreasing trends in stream-water silicon (Si) (−0.2 μeq L−1 yr−1) and base cations suggest a decrease in the soil mineral weathering rate. We hypothesize that a decrease in the ionic strength of soil water and shallow groundwater may be the principal driver of this apparent decrease in the weathering rate. A decreasing weathering rate would help to explain the slow recovery of stream pH and ANC as well as that of soil base cations.

Wheat is one of several cereals that is capable of accumulating higher amounts of Cd in plant tissues. It is important to understand the Cd²⁺ transport processes in roots that result in excess Cd accumulation. Traditional destructive technologies have limited capabilities in analyzing root samples due to methodological limitations, and sometimes may result in false conclusions. The mechanisms of Cd²⁺ uptake into the roots of wheat seedlings (Triticum aestivum L.) were investigated by assessing the impact of various inhibitors and channel blockers on Cd accumulation as well as the real-time net Cd²⁺ flux at roots with the non-destructive scanning ion-selective electrode technique. The P-type ATPase inhibitor Na3VO4 (500 μM) had little effect on Cd uptake (p < 0.05) and the kinetics of transport in the root of wheat, suggesting that Cd²⁺ uptake into wheat root cells is not directly dependent on H⁺ gradients. While, the uncoupler 2,4-dinitrophenol significantly limited Cd²⁺ uptake (p < 0.05) and transport kinetics in the root of wheat, suggesting the existence of metabolic mediation in the Cd²⁺ uptake process by wheat. The Cd content at the whole-plant level in wheat was significantly (p < 0.05) decreased upon pretreatment with the Ca²⁺ channel blockers La³⁺ or Gd³⁺ and Verapamil, but not in case of pretreatment with the K⁺ channel blocker tetraethylammonium (TEA). In addition, the inhibitors of the Ca²⁺ channel, as well as high concentrations of Ca²⁺, reduced the real-time net Cd²⁺ fluxes at the root surface in SIET experiments. These results indicate that Cd²⁺ moves across the plasma lemma of the wheat root via Ca²⁺ channels. In addition, our results suggested a role for protein synthesis in mediating Cd²⁺ uptake and transport by wheat.

The impacts of iron oxide nanoparticles (γ-Fe2O3 NPs) and ferric ions (Fe³⁺) on plant growth and molecular responses associated with the transformation and transport of Fe²⁺ were poorly understood. This study comprehensively compared and evaluated the physiological and molecular changes of Citrus maxima plants as affected by different levels of γ-Fe2O3 NPs and Fe³⁺. We found that γ-Fe2O3 NPs could enter plant roots but no translocation from roots to shoots was observed. 20 mg/L γ-Fe2O3 NPs had no impact on plant growth. 50 mg/L γ-Fe2O3 NPs significantly enhanced chlorophyll content by 23.2% and root activity by 23.8% as compared with control. However, 100 mg/L γ-Fe2O3 NPs notably increased MDA formation, decreased chlorophyll content and root activity. Although Fe³⁺ ions could be used by plants and promoted the synthesis of chlorophyll, they appeared to be more toxic than γ-Fe2O3 NPs, especially for 100 mg/L Fe³⁺. The impacts caused by γ-Fe2O3 NPs and Fe³⁺ were concentration-dependent. Physiological results showed that γ-Fe2O3 NPs at proper concentrations had the potential to be an effective iron nanofertilizer for plant growth. RT-PCR analysis showed that γ-Fe2O3 NPs had no impact on AHA gene expression. 50 mg/L γ-Fe2O3 NPs and Fe³⁺ significantly increased expression levels of FRO2 gene and correspondingly had a higher ferric reductase activity compared to both control and Fe(II)-EDTA exposure, thus promoting the iron transformation and enhancing the tolerance of plants to iron deficiency. Relative levels of Nramp3 gene expression exposed to γ-Fe2O3 NPs and Fe³⁺ were significantly lower than control, indicating that all γ-Fe2O3 NPs and Fe³⁺ treatments could supply iron to C. maxima seedlings. Overall, plants can modify the speciation and transport of γ-Fe2O3 NPs or Fe³⁺ for self-protection and development by activating many physiological and molecular processes.

Microcystin-LR is the most poisonous and commonly encountered hepatotoxin produced by cyanobacteria in an aquatic ecosystem, and it may cause thyroid dysfunction in fish. The present study aimed to reveal the effects of transgenerational toxicity of MCLR on the thyroid endocrine system under sub-chronic exposure conditions. Adult zebrafish (F0) were exposed to environmentally relevant concentrations (1, 5 and 25 μg/L) of MCLR for 45 days. The produced F1 embryos were then tested without further MCLR treatment. In the F0 generation, exposure to 25 μg/L MCLR reduced thyroxine (T4) but not 3, 5, 3′-triiodothyronine (T3) levels in females, while the T4 and T3 levels were unchanged in males. After parental exposure to MCLR, we observed a decreased hatching and growth retardation correlated with reduced thyroid hormone levels in the F1 offspring. The gene transcription and protein expression along the hypothalamic-pituitary-thyroid axis were detected to further investigate the possible mechanisms of MCLR-induced thyroid disruption. Our results indicated MCLR could disturb the thyroid endocrine system under environmentally relevant concentrations and the disrupting effects could be remarkably transmitted to its F1 offspring. We regard these adverse effects as a parental transgenerational toxicity of MCLR.

With their application as seed coatings, the use of neonicotinoid insecticides increased dramatically during the last decade. They are now frequently detected in aquatic ecosystems at concentrations susceptible to harm aquatic invertebrates at individual and population levels. This study intent was to document surface runoff and subsurface tile drain losses of two common neonicotinoids (thiamethoxam and clothianidin) compared to those of companion herbicides (atrazine, glyphosate, S-metolachlor and mesotrione) at the edge of a 22.5-ha field under a corn-soybean rotation. A total of 14 surface runoff and tile drain discharge events were sampled over two years. Events and annual unit mass losses were computed using flow-weighted concentrations and total surface runoff and tile drain flow volumes. Detection frequencies close to 100% in edge-of-field surface runoff and tile drain water samples were observed for thiamethoxam and clothianidin even though only thiamethoxam had been applied in the first year. In 2014, thiamethoxam median concentrations in surface runoff and tile drain samples were respectively 0.46 and 0.16 μg/L, while respective maximum concentrations of 2.20 and 0.44 μg/L were measured in surface runoff and tile drain samples during the first post-seeding storm event. For clothianidin, median concentrations in surface runoff and tile drain samples were 0.02 and 0.01, μg/L, and respective maximum concentrations were 0.07 μg/L and 0.05 μg/L. Surface runoff and tile drain discharge were key transport mechanisms with similar contributions of 53 and 47% of measured mass losses, respectively. Even if thiamethoxam was applied at a relatively low rate and had a low mass exportation value (0.3%), the relative toxicity was one to two orders of magnitude higher than those of the other chemicals applied in 2014 and 2015. Companion herbicides, except glyphosate in tile drains, exceeded their water quality guideline during one sampling campaign after application but rapidly resumed below these limits.

Dissolved humic acid (HA) is ubiquitous in natural waters. Its presence significantly changes the photo-and bio-degradation of some organic pollutants in natural waters. The effects of photobleaching on the composition, photosensitizing property and bioavailability of HA were investigated here along with the subsequent influence on its photochemical and biological reactivity in mediating 17α-ethynylestradiol (EE2) degradation. Photobleaching transformed the refractory HA into some small molecules, including organic acids and aliphatics. Along with composition alteration, the photochemical reactivity of HA towards EE2 was slightly depressed, with 9% of the removal rate inhibited by a 70-h photobleaching. Contrarily, the reactivity of HA in mediating EE2 biodegradation by E. coli was significantly promoted by a short-term photobleaching. Compared to the biodegradation of EE2 in the pristine HA, the 10-h photobleached HA increased the biodegradation removal rate of EE2 by 25%, reaching its peak value of about 60%. However, the EE2 biodegradation was inhibited by further irradiation, and the removal rate of EE2 decreased to that in the pristine HA systems. Because no substrate competition was found between EE2 and formate or glucose, EE2 biodegradation mediated by HA in natural waters may not be affected by coexistent organics. Photodegradation and biodegradation of EE2 mediated by HA thus can be combined together by photobleaching to remove pollutants from natural waters. The results reported here could assist environmental risk assessment with respect to EE2 in natural aquatic systems.

Increasing applications of titanium dioxide nanoparticles (nano-TiO2) have intensified the risk of environmental contamination. Since nano-TiO2 can absorb metals and be consumed as ‘food’ by zooplankton but also can interact with phytoplankton, they could significantly disturb the existing metal assimilation patterns. In the present study, we quantified the dietary assimilation of Cd and Zn from nano-TiO2 and algae (Chlamydomonas reinhardtii) at comparable particle concentrations as well as in complex food environment (variable food quality and quantity) in a freshwater zooplankton Daphnia magna using the radiotracer technique. For both nano-TiO2 and algae as food, the feeding food quality and depuration food quantity significantly affected the assimilation efficiencies (AEs) of Cd and Zn. At feeding food quantity of 1 mg/L to 10 mg/L without food in depuration, the AEs of Cd and Zn from nano-TiO2 were lower than those from algae. When food was added during depuration, the influences of nano-TiO2 on metal AEs were variable due to the differential effects of food quantity on the gut passage of nano-TiO2 and algae. Furthermore, mixed nano-TiO2 and algae had the lowest metal AEs compared to sole nano-TiO2 or algae as a result of interaction between nano-TiO2 and algae during feeding. Overall, this study showed the distinguishing metal AEs between nano-TiO2 and algae, and that nano-TiO2 could significantly reduce the existing metal AEs from algae. More attention should be paid to the potential roles of nano-TiO2 in disturbing metal assimilation in the environmental risk assessments of nanoparticles.