Perfluorochemicals in wastewater treatment plants and sediments in Hong Kong

The study reported in this paper examined the concentrations of nineteen perfluorochemicals (PFCs), including perfluoroalkyl sulfonates, carboxylates, and sulfonamides in samples collected from Hong Kong wastewater treatment plants (WWTPs) and sediments. The study was the first to use an external isolator column to assist in the quantification of PFCs in environmental samples without having to make internal modifications to a liquid chromatography system. Perfluorooctanesulfonate was found to be the dominant PFC pollutant in Hong Kong, and the WWTP sludge was the major sink of PFCs discharged from the urban areas. Compared to discharge influenced by industrial activities, much less perfluorooctanoate was found in waste streams. The significantly lower level of perfluorodecanesulfonate in WWTP sludge reflects the important influence of consumer products on PFC distribution. The dominance of even-chain length perfluoroalkyl carboxylates in all of the WWTP sludge samples investigated further suggests the strong aerobic degradation of fluorotelomer alcohols in WWTPs.     

Modelling the fate of hydrophobic organic contaminants in a boreal forest catchment: A cross disciplinary approach to assessing diffuse pollution to surface waters

The fate of hydrophobic organic compounds (HOCs) in soils and waters in a northern boreal catchment was explored through the development of a chemical fate model in a well-characterised catchment system dominated by two land types: forest and mire. Input was based solely on atmospheric deposition, dominated by accumulation in the winter snowpack. Release from soils was governed by the HOC concentration in soil, the soil organic carbon fraction and soil-water DOC content. The modelled export of selected HOCs in surface waters ranged between 11 and 250 ng day⁻¹ during the snow covered period, compared to 200 and 9600 ng/d during snow-melt; highlighting the importance of the snow pack as a source of these chemicals. The predicted levels of HOCs in surface water were in reasonable agreement to a limited set of measured values, although the model tended to over predict concentrations of HOCs for the forested sub-catchment, by over an order of magnitude in the case of hexachlorobenzene and PCB 180. This possibly reflects both the heterogeneity of the forest soils and the complicated and changing hydrology experienced between the different seasons.     

Phytotoxicity of atrazine and alachlor in soil amended with sludge,manure and activated carbon

Abstract

Greenhouse studies were conducted to determine the influence of waste‐activated carbon (WAC), digested municipal sewage sludge (DMS), and animal manure on herbicidal activity of atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐trazine] and alachlor [2‐chloro‐2’,6'‐diethyl‐N‐(methoxymethyl)acetanilide] in a Plainfield sandy soil. Amendments generally reduced bioactivity against oat (Avena sativa L.) and Japanese millet (E. crus‐galli frumentacea). The extent to which herbicide phytotoxicity was inhibited depended upon the application rate and the kind of soil amendment. WAC, applied at the loading rate of 2.1 mt C/ha, showed a significant inhibitory effect on both herbicides. In DMS‐ and manure‐amended soil, the reduction of atrazine activity was not significant at the rate of 8.4 mt C/ha, but reduction of alachlor activity was significant at the rate of 4.2 mt C/ha. Despite inhibition of herbicidal activity, the ED₅₀ of atrazine and alachlor was below 2 ppm in most of the amendment treatments. Before adopting carbon‐rich waste amendments as management practices for controlling pesticide leaching in coarse‐textured soils, further studies are needed to characterize how alterations in sorption, leaching and degradation may affect herbicidal activity.     

The impact of sewage sludge compost on tree peony growth and soil microbiological,and biochemical properties

In order to assess the suitability of sludge compost application for tree peony (Paeonia suffruticosa)–soil ecosystems, we determined soil microbial biomass C (C_mic), basal respiration (R_mic), enzyme activities, and tree peony growth parameters at 0–75% sludge compost amendment dosage. Soil C_mic, R_mic, C_mic as a percent of soil organic C, enzyme (invertase, urease, proteinase, phosphatase, polyphenoloxidase) activities, and plant height, flower diameter, and flower numbers per plant of tree peony significantly increased after sludge compost amendment; however, with the increasing sludge compost amendment dosage, a decreasing trend above 45% sludge compost amendment became apparent although soil organic C, total Kjeldahl N, and total P always increased with the sludge compost amendment. Soil metabolic quotient first showed a decreasing trend with the increasing sludge compost application in the range of 15–45%, and then an increasing trend from compost application of 45–75%, with the minimum found at compost application of 45%. As for the diseased plants, 50% of tree peony under the treatment without sludge compost amendment suffered from yellow leaf disease of tree peony, while no any disease was observed under the treatments with sludge compost application of 30–75%, which showed sludge compost application had significant suppressive effect on the yellow leaf disease of tree peony. This result convincingly demonstrated that ?45% sludge compost application dosage can take advantage of beneficial effect on tree peony growth and tree peony–soil ecosystems.     

Quantification of the interactions between Ca,Hg and extracellular polymeric substances (EPS) of sludge

The interactions between metals (Ca²⁺ and Hg²⁺) and extracellular polymeric substances (EPS) extracted from the aerobic and anaerobic sludge in wastewater treatment reactors were investigated using a combination of zeta potential measurement and 3-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analysis. Results show that Ca²⁺ had no substantial effects on the EEM fluorescence spectra of the EPS, but their zeta potentials increased with the increasing Ca²⁺ dosage. However, Hg²⁺ had a significant effect on the EEM fluorescence spectra of the EPS, while their zeta potentials seemed not to be affected by the dose of Hg²⁺. The interactions between Hg²⁺ and EPS were elucidated using the fluorescence quenching with PARAFAC analysis, while the interactions between Ca²⁺ and EPS were evaluated by the zeta potential technique. The binding constants for Hg²⁺ and EPS were two orders of magnitude higher than those for Ca²⁺ and EPS, suggesting that the binding mechanisms between Ca²⁺ and EPS were different from those between Hg²⁺ and EPS. The results might be useful for understanding the roles of EPS in bacterial self-protection against heavy metals and the aggregate formation mechanisms through ionic bridging interactions.     

Projecting Climate Change Effects on Forest Net Primary Productivity in Subtropical Louisiana,USA

This study projected responses of forest net primary productivity (NPP) to three climate change scenarios at a resolution of 5 km × 5 km across the state of Louisiana, USA. In addition, we assessed uncertainties associated with the NPP projection at the grid and state levels. Climate data of the scenarios were derived from Community Climate System Model outputs. Changes in annual NPP between 2000 and 2050 were projected with the forest ecosystem model PnET-II. Results showed that forest productivity would increase under climate change scenarios A1B and A2, but with scenario B1, it would peak during 2011–2020 and then decline. The projected average NPP under B1 over the years from 2000 to 2050 was significantly different from those under A1B and A2. Forest NPP appeared to be primarily a function of temperature, not precipitation. Uncertainties of the NPP projection were due to large spatial resolution of the climate variables. Overall, this study suggested that in order to project effects of climate change on forest ecosystem at regional level, modeling uncertainties could be reduced by increasing the spatial resolution of the climate projections.     

Adsorptive removal of an acid dye by lignocellulosic waste biomass activated carbon: equilibrium and kinetic studies

Chemically prepared activated carbon material derived from palm flower was used as adsorbent for removal of Amido Black dye in aqueous solution. Batch adsorption studies were performed for the removal of Amido Black 10B (AB10B), a di-azo acid dye from aqueous solutions by varying the parameters like initial solution pH, adsorbent dosage, initial dye concentration and temperature with three different particle sizes such as 100 μm, 600 μm and 1000 μm. The zero point charge was pH 2.5 and the maximum adsorption occurred at the pH 2.3. Experimental data were analyzed by model equations such as Langmuir, Freundlich and Temkin isotherms and it was found that the Freundlich isotherm model best fitted the adsorption data and the Freundlich constants varied from (K_F) 1.214, 1.077 and 0.884 for the three mesh sizes. Thermodynamic parameters such as ΔG, ΔH and ΔS were also calculated for the adsorption processes and found that the adsorption process is feasible and it was the endothermic reaction. Adsorption kinetics was determined using pseudo first-order, pseudo second-order rate equations and also Elovich model and intraparticle diffusion models. The results clearly showed that the adsorption of AB10B onto lignocellulosic waste biomass from palm flower (LCBPF) followed pseudo second-order model, and the pseudo second-order rate constants varied from 0.059 to 0.006 (g mg⁻¹ min) by varying initial adsorbate concentration from 25 mg L⁻¹ to 100 mg L⁻¹. Analysis of the adsorption data confirmed that the adsorption process not only followed intraparticle diffusion but also by the film diffusion mechanism.     

Assessment of fates of estrogens in wastewater and sludge from various types of wastewater treatment plants

We measured five estrogens in the wastewater samples from the municipal wastewater treatment plants (M-WWTPs), livestock wastewater treatment plants (L-WWTPs), hospital WWTPs (H-WWTPs) and pharmaceutical manufacture WWTPs (P-WWTPs) in Korea. The L-WWTPs showed the highest total concentration (0.195-10.4 μg L⁻¹) of estrogens in the influents, followed by the M-WWTPs (0.028-1.15 μg L⁻¹), H-WWTPs (0.068-0.130 μg L⁻¹) and P-WWTPs (0.015-0.070 μg L⁻¹). Like the influents, the L-WWTPs (0.003-0.729 μg L⁻¹) and the M-WWTPs (0.001-0.299 μg L⁻¹) also showed higher total concentration of estrogens in the effluents than the H-WWTPs (0.002-0.021 μg L⁻¹) and P-WWTPs (0.011 μg L⁻¹ in one sample). The L-WWTPs (37.5-543 μg kg⁻¹, dry weight) showed higher total concentrations in sludge than the M-WWTPs (3.16-444 μg kg⁻¹, dry weight) like the wastewater. The distribution of estrogens in the WWTPs may be affected by their metabolism in the human body, their transition through biological treatment processes, and their usage for livestock growth. Unlike the concentration results, the daily loads of estrogens from the M-WWTPs were the highest, which is related to the high capacities of WWTPs.     

Quantification of nitrate leaching from German forest ecosystems by use of a process oriented biogeochemical model

Simulations with the process oriented Forest-DNDC model showed reasonable to good agreement with observations of soil water contents of different soil layers, annual amounts of seepage water and approximated rates of nitrate leaching at 79 sites across Germany. Following site evaluation, Forest-DNDC was coupled to a GIS to assess nitrate leaching from German forest ecosystems for the year 2000. At national scale leaching rates varied in a range of 0–>80 kg NO₃–N ha⁻¹ yr⁻¹ (mean 5.5 kg NO₃–N ha⁻¹ yr⁻¹). A comparison of regional simulations with the results of a nitrate inventory study for Bavaria showed that measured and simulated percentages for different nitrate leaching classes (0–5 kg N ha⁻¹ yr⁻¹:66% vs. 74%, 5–15 kg N ha⁻¹ yr⁻¹:20% vs. 20%, >15 kg N ha⁻¹ yr⁻¹:14% vs. 6%) were in good agreement. Mean nitrate concentrations in seepage water ranged between 0 and 23 mg NO₃–N l⁻¹.     

Regulation (EC) No. 1107/2009 and upcoming challenges for exposure assessment of plant protection products--Harmonisation or national modelling approaches?

In the new European Pesticide Regulation (EC) No. 1107/2009, the harmonisation of approaches for estimation of the environmental exposure of pesticides is considered a major goal. Several member states currently require their own models for the calculation of predicted environmental concentrations (PEC) in surface water. The variety of methods makes risk evaluations rather time-consuming for both notifiers and evaluating authorities. In the present study we compare surface water concentrations of 19 compounds using EU and country-specific models and risk assessment approaches to evaluate to which extent the resulting estimated exposure concentrations differ. Our results show that EU and country specific approaches and the resulting surface water concentrations differ considerably regarding basic model assumptions and assessment methods. The results indicate that the aimed harmonisation of risk assessment approaches within the EU will be difficult based on current models. New scenarios may help to achieve a harmonisation taking country-specific features into account.