Changes in biomass activity and characteristics of activated sludge exposed to low ozone dose

In this paper, the response mechanism of activated sludge exposed to low-dose ozone at less than 20 mg O₃ g⁻¹ total suspended solids (TSS) was studied by analyzing the changes in sludge activity and the evolution of C, N, P and metals from sludge following ozonation. The intracellular ATP concentration was not affected at less than 5 mg O₃ g⁻¹ TSS and thereafter decreased rapidly to around 60% when the ozone dose increased to 20 mg O₃ g⁻¹ TSS. Similarly, the efficiency of sludge solubilization initially changed a little and then increased rapidly to around 30% at an ozone dose of 20 mg O₃ g⁻¹ TSS. However, the activities of superoxide dismutase and protease decreased immediately upon exposure to ozone. These findings indicate that ozone firstly destroys the floc, leading to the disruption of the compact aggregates, which does not affect cells viability but induces a decrease in enzyme activities. Ozone then attacks the bacterial cells of the sludge, causing a decrease in cells viability. During ozonation, the content of carbon, nitrogen and phosphorus in the sludge matrix decreased, while the content of these elements in the micro-solids and supernatant gradually increased. Most of the released metals from the sludge matrix were found in the micro-solids.     

Reactive barriers for Cs retention

¹³⁷Cs was dispersed globally by cold war activities and, more recently, by the Chernobyl accident. Engineered extraction of ¹³⁷Cs from soils and groundwaters is exceedingly difficult. Because the half-life of ¹³⁷Cs is only 30.2 years, remediation might be more effective (and less costly) if ¹³⁷Cs bioavailability could be demonstrably limited for even a few decades by use of a reactive barrier. Essentially permanent isolation must be demonstrated in those few settings where high nuclear level wastes contaminated the environment with ¹³⁵Cs (half-life 2.3×10⁶ years) in addition to ¹³⁷Cs. Clays are potentially a low-cost barrier to Cs movement, though their long-term effectiveness remains untested. To identify optimal clays for Cs retention, Cs desorption was measured for five common clays: Wyoming Montmorillonite (SWy-1), Georgia Kaolinites (KGa-1 and KGa-2), Fithian Illite (F-Ill), and K-Metabentonite (K-Mbt). Exchange sites were pre-saturated with 0.16 M CsCl for 14 days and readily exchangeable Cs was removed by a series of LiNO₃ and LiCl washes. Washed clays were then placed into dialysis bags and the Cs release to the deionized water outside the bags measured. Release rates from 75 to 139 days for SWy-1, K-Mbt and F-Ill were similar; 0.017% to 0.021% sorbed Cs released per day. Both kaolinites released Cs more rapidly (0.12% to 0.05% of the sorbed Cs per day). In a second set of experiments, clays were Cs-doped for 110 days and subjected to an extreme and prolonged rinsing process. All the clays exhibited some capacity for irreversible Cs uptake. However, the residual loading was greatest on K-Mbt (0.33 wt.% Cs). Thus, this clay would be the optimal material for constructing artifical reactive barriers.     

Adsorption studies of the herbicide simazine in agricultural soils of the Aconcagua valley, central Chile

Simazine is a s-triazine herbicide that has been applied worldwide for agriculture. This herbicide is the second most commonly detected pesticide in surface and groundwater in the United States, Europe and Australia. In this study, simazine adsorption behaviour was studied in two agricultural soils of the Aconcagua valley, central Chile. The two studied soils were soil A (loam, 8.5% organic matter content) and soil B (clay-loam, 3.5% organic matter content). Three times higher simazine adsorption capacity was observed in soil A (68.03 mg kg⁻¹) compared to soil B (22.03 mg kg⁻¹). The simazine adsorption distribution coefficients (K_d) were 9.32 L kg⁻¹ for soil A and 7.74 L kg⁻¹ for soil B. The simazine adsorption enthalpy in soil A was −21.0 kJ mol⁻¹ while in soil B the adsorption enthalpy value was −11.5 kJ mol⁻¹. These results indicate that simazine adsorption process in these soils is exothermic, governing H bonds the adsorption process of simazine in both the loam and clay-loam soils. These results and the potentiometric profiles of both soils, suggest that simazine adsorption in soil A is mainly governed by simazine–organic matter interactions and in soil B by simazine–clay interactions. The understanding of simazine sorption–desorption processes is essential to determine the pesticide fate and availability in soil for pest control, biodegradation, runoff and leaching.     

Acute and chronic effects of nano- and non-nano-scale TiO2 and ZnO particles on mobility and reproduction of the freshwater invertebrate Daphnia magna

Among the emerging literature addressing the biological effects of nanoparticles, very little information exists, particularly on aquatic organisms, that evaluates nanoparticles in comparison to non-nanocounterparts. Therefore, the potential effects of nano-scale and non-nano-scale TiO₂ and ZnO on the water flea, Daphnia magna, were examined in 48-h acute toxicity tests using three different test media, several pigment formulations – including coated nanoparticles – and a variety of preparation steps. In addition, a 21-d chronic Daphnia reproduction study was performed using coated TiO₂ nanoparticles. Analytical ultracentrifugation analyses provided evidence that the nanoparticles were present in a wide range of differently sized aggregates in the tested dispersions. While no pronounced effects on D. magna were observed for nano-scale and non-nano-scale TiO₂ pigments in 19 of 25 acute (48-h) toxicity tests (EC50 > 100 mg L⁻¹), six acute tests with both nano- and non-nano-scale TiO₂ pigments showed slight effects (EC10, 0.5–91.2 mg L⁻¹). For the nano-scale and non-nano-scale ZnO pigments, the acute 48-h EC50 values were close to the 1 mg L⁻¹ level, which is within the reported range of zinc toxicity to Daphnia. In general, the toxicity in the acute tests was independent of particle size (non-nano-scale or nano-scale), coating of particles, aggregation of particles, the type of medium or the applied pre-treatment of the test dispersions. The chronic Daphnia test with coated TiO₂ nanoparticles demonstrated that reproduction was a more sensitive endpoint than adult mortality. After 21 d, the NOEC for adult mortality was 30 mg L⁻¹ and the NOEC for offspring production was 3 mg L⁻¹. The 21-d EC10 and EC50 values for reproductive effects were 5 and 26.6 mg L⁻¹, respectively. This study demonstrates the utility of evaluating nanoparticle effects relative to non-nano-scale counterparts and presents the first report of chronic exposure to TiO₂ nanoparticles in D. magna.     

Levels and congener profiles of PCDD/Fs, PCBs and PBDEs in seafood from China

A nationwide investigation into polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in market seafood was conducted for the first time in this study. Total PCDD/F concentrations in fatty fish ranged from 0.13 to 8.64 pg g⁻¹ wet weight (mean 2.05 pg g⁻¹ wet weight), total PCB concentrations ranged from 38.9 to 3514 pg g⁻¹ wet weight (mean 1133 pg g⁻¹ wet weight), and total PBDE concentrations ranged from 42.8 to 913 pg g⁻¹ wet weight (mean 322 pg g⁻¹ wet weight). Corresponding mean toxicity equivalent (TEQ) values for total PCDD/F and dioxin-like PCB were 0.25 pg g⁻¹ wet weight (WHO 98-TEQ) and 0.32 pg g⁻¹ wet weight (WHO 98-TEQ), respectively. OCDD, PCB-138 and PBDE-47 were the dominant compounds according to their respective congeners. WHO 98-TEQ _{PCDD/PCDF/PCB} for fatty fish and shell fish were 0.60 and 0.070 pg g⁻¹ wet weight, respectively, lower than the standard set by the European Commission. The contamination levels and profiles were compared with those documented in previous publications.     

Simultaneous E. coli inactivation and NOM degradation in river water via photo-Fenton process at natural pH in solar CPC reactor. A new way for enhancing solar disinfection of natural water

Bacteria inactivation and natural organic matter oxidation in river water was simultaneously conducted via photo-Fenton reaction at “natural” pH (6.5) containing 0.6 mg L⁻¹ of Fe³⁺ and 10 mg L⁻¹ of H₂O₂. The experiments were carried out by using a solar compound parabolic collector on river water previously filtered by a slow sand filtration system and voluntarily spiked with Escherichia coli. Fifty five percent of 5.3 mg L⁻¹ of dissolved organic carbon was mineralized whereas total disinfection was observed without re-growth after 24 h in the dark.     

Sorption studies of chloroanilines on kaolinite and montmorillonite

Batch experiments have been performed in order to evaluate the ability of the two reference clays kaolinite (KGa-1) and Na-montmorillonite (SWy-1) to retain three representative chloroanilines: 3-chloroaniline, 3,4-dichloroaniline and 2,4,6-trichloroaniline. Systems containing the clay mineral and the pollutant solution (at concentration levels ranging between 1.0 and 10.0mg/L) were considered and RP-HPLC methods were employed to follow the sorption processes as a function of time. The results indicate that montmorillonite shows a general higher sorption capacity with respect to kaolinite and that for both the reference clays, in the concentration range investigated, the amount of pollutant sorbed increases with concentration. The sorption coefficient K(d) ranges between 0.0030 L/g for the system 3-chloroaniline-kaolinite and 0.0488L/g for the system 2,4,6-trichloroaniline-montmorrillonite. The most lipophilic trichloroaniline shows the greater sorption. X-ray analyses suggest for kaolinite a preferential sorption onto the mineral surface, while for montmorillonite a progressive swelling of the structure is observed, likely due to sorption processes that also take place in the interlayer.     

Organochlorine pesticides in surface sediments and suspended particulate matters from the Yangtze estuary, China

Total HCHs' and total DDTs' levels in surface sediments (SS) ranged from 0.5 to 17.5 ng g⁻¹ and from 0.9 to 33.1 ng g⁻¹, averaged 6.0 and 8.2 ng g⁻¹, respectively. Total HCHs' and total DDTs' levels in suspended particulate matters (SPM) varied from 6.2 to 14.8 ng g⁻¹ with a mean value of 12.3 ng g⁻¹ and were from 3.4 to 25.7 ng g⁻¹ with an average of 16.4 ng g⁻¹, respectively. Lindane is the main HCHs' source and continuing use in the Yangtze Delta areas of ‘pure’ γ-HCH (lindane) rather than technical HCH (a mix of largely α- and some γ-HCH). DDTs in SS are mainly accumulated in history. However, high DDT fractions in SPM are indicators of new input of typical dicofol type DDT from 2002 to 2004. It can be seen that most samples from the Yangtze estuary were in ranges where adverse biological effects are expected, either occasionally or frequently.     

Influence of tidal regime on the distribution of trace metals in a contaminated tidal freshwater marsh soil colonized with common reed (Phragmites australis)

A historical input of trace metals into tidal marshes fringing the river Scheldt may be a cause for concern. Nevertheless, the specific physicochemical form, rather than the total concentration, determines the ecotoxicological risk of metals in the soil. In this study the effect of tidal regime on the distribution of trace metals in different compartments of the soil was investigated. As, Cd, Cu and Zn concentrations in sediment, pore water and in roots were determined along a depth profile. Total sediment metal concentrations were similar at different sites, reflecting pollution history. Pore water metal concentrations were generally higher under less flooded conditions (mean is (2.32 ± 0.08) × 10⁻³ mg Cd L⁻¹ and (1.53 ± 0.03) × 10⁻³ mg Cd L⁻¹). Metal concentrations associated with roots (mean is 202.47 ± 2.83 mg Cd kg⁻¹ and 69.39 ± 0.99 mg Cd kg⁻¹) were up to 10 times higher than sediment (mean is 20.48 ± 0.19 mg Cd kg⁻¹ and 20.42 ± 0.21 mg Cd kg⁻¹) metal concentrations and higher under dryer conditions. Despite high metal concentrations associated with roots, the major part of the metals in the marsh soil is still associated with the sediment as the overall biomass of roots is small compared to the sediment.     

Sorption of Pesticides on Kaolinite and Montmorillonite as a Function of Hydrophilicity

Pesticides and other organic species are adsorbed by soil via different mechanisms, with bond strengths that depend on the properties of both the soil and the pesticide. Since the clay fraction in soil is a preferential sorbent for organic matter, reference kaolinite and montmorillonite are useful models for studying the mechanism and the strength of sorption. This paper presents the results of batch experiments to investigate the interactions of kaolinite KGa-1 and montmorillonite SWy-1 with the following pesticides and organic species resulting from the natural degradation of pesticides in the environment: atrazine (1-chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine), simazine (1-chloro-3,5-bisethylamino-2,4,6-triazine), diuron [1,1-dimethyl-3-(3,4-dichlorophenyl)urea], aniline, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. Each of these chemicals has different hydrophilicity. Systems containing 2.0 g of clay were put in contact with 100.0 mL of solutions of the pesticides at known concentration ranging from 1.0 to 5.0 mg/L, and the amount of solute adsorbed was evaluated through RP-HPLC analysis of the pesticide still present in the aqueous suspension. To test for electrostatic interactions between the clay surface and the pesticides, potentiometric titration was used to determine the permanent surface charge of clays. Experiments were performed at different pH values. The results indicate that, for the chemicals studied, neutral molecules are preferentially retained relative to ionized ones, and that montmorillonite is a more effective sorbent than kaolinite.     

Polychlorinated dibenzo-p-dioxins, dibenzofurans and polychlorinated biphenyls levels in human breast milk from different regions of Turkey

Human breast milk offers the optimal nutrition for all infants and have been widely used in biomonitoring programs to assess human exposure to lipophylic environmental contaminants such as polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and polychlorinated biphenyls (PCB). There are no previous reports from Turkey on chemically determined levels of PCDDs, PCDFs, and PCBs in human breast milk expressed as World Health Organization (WHO) toxic equivalents (TEQ). To get an overview of the levels of these contaminants in Turkish human milk, samples from 51 Turkish women living in the Ankara, İstanbul, Antalya, Kahramanmaraş, and Afyon provinces were analyzed by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) throughout 2007. The mean concentrations of WHO_PCDD/F-TEQ and WHO_PCB-TEQ of all samples from the five regions were 7.5 and 3.1 pg g⁻¹ on a lipid basis, respectively. PCDD/F concentrations ranged between 0.78 and 29.3 pg WHO-TEQ g⁻¹ fat (1.7 and 36.2 pg WHO-TEQ g⁻¹ fat, respectively, including PCB). Of the five studied locations, the lowest levels of ∑TEQs (PCDD/F + PCB) were found in the Afyon (6.8 pg WHO-TEQ g⁻¹ fat) and the highest in the Antalya (15.6 pg WHO-TEQ g⁻¹ fat) province. The results have been discussed in terms of regions and PCDD/F and PCBs for which analyses had been made. The mean levels of PCDD/Fs and PCBs in Turkish human milk are comparable to that found in other countries.     

Spatial character of polychlorinated biphenyls from soil and respirable particulate matter in Taiyuan, China

As one of China’s great metropolises, Taiyuan is affected by heavy chemical industry and manufacture of chemical products, and faces pollution from polychlorinated biphenyls (PCBs). Therefore, this study was conducted to determine the PCB concentrations in various environmental media in Taiyuan. We collected 15 soil samples, 34 respirable particulate matter (PM) samples (17 of PM_2.5 and 17 of PM₁₀) from urban areas of Taiyuan, and measured a total of 144 PCB congeners (including some coeluting PCB congeners). The total PCB concentrations were 51–4.7 × 10³ pg g⁻¹ in soil, 27–1.4 × 10² pg m⁻³ in PM_2.5 and 16–1.9 × 10² pg m⁻³ in PM₁₀. Of the PCB homologues, the dominant PCBs detected in the various media were all tri-CBs. Soil was relatively the most polluted media. Furthermore, principal-component analysis revealed that the major PCB source in Taiyuan may be associated with the main commercial PCB through long-range transmission. Toxic equivalency (TEQ) concentrations (based on ten dioxin-like PCBs) ranged from N.D. to 5.9 × 10⁻³ pg-WHO TEQ g⁻¹ in soil, 2.0 × 10⁻⁴–3.4 × 10⁻³ pg-WHO TEQ m⁻³ and 1.0 × 10⁻⁴–1.2 × 10⁻³ pg-WHO TEQ m⁻³ in PM_2.5 and PM₁₀, respectively. In previous studies, PCBs were not a severe component of contaminant in Taiyuan; however, this study suggested there is a potential threat of human exposure to PCBs for residents of Taiyuan.     

Mercury deposition/accumulation rates in the vicinity of a lead smelter as recorded by a peat deposit

Mercury (Hg) concentration profiles and historical accumulation rates were determined in three ²¹⁰Pb-dated cores from a peat deposit in the vicinity of a lead (Pb) smelter at Příbram, Czech Republic. The Hg concentrations in peat samples ranged from 66 to 701 μg kg⁻¹. Cumulative Hg inventories from each core (for the past 150 yr) varied by a factor of 1.4 (13.6–18.5 mg Hg m⁻²), indicating variations of net Hg accumulation rate within the peat deposit. Historical changes in vegetation cover (leading to variable interception by trees) are probably responsible for this variation in space and time. The uncorrected Hg accumulation rates peaked between the 1960s and 1980s (up to 226 μg m⁻² yr⁻¹). Recent findings show that Hg records from peat tend to overestimate historical levels of Hg deposition. Therefore we used the mass loss compensation factor (MLCF) to normalize Hg accumulation rates. These corrected Hg accumulation rates were significantly lower (maximum 129 μg m⁻² yr⁻¹) and better corresponded to changes in historical smelter emissions, which were highest in the 1960s. The agreement between the corrected Hg accumulation rates in the uppermost peat sections (2–38 μg m⁻² yr⁻¹) and biomonitoring of atmospheric deposition by mosses in several recent years (4.7–34.4 μg m⁻² yr⁻¹) shows the usefulness of MLCF application on Hg accumulation in peat archives. However, the MLCF correction was unsuitable for Pb. The recent Pb deposition rates obtained by an independent biomonitoring study using mosses (0.5–127 mg m⁻² yr⁻¹) were better correlated with net Pb accumulation rates recorded in peat (7–145 mg m⁻² yr⁻¹) than with corrected rates obtained by the MLCF approach (1–28 mg m⁻² yr⁻¹).     

Arsenic concentration in porewater of an alkaline coal ash disposal site: Roles of siderite precipitation/dissolution and soil cover

The geochemical behavior of As in porewaters of an alkaline coal ash disposal site was investigated using multilevel samplers. The disposal site was in operation from 1983 until 1994 and was covered with 0.3–0.5 m thick soils in 2001 when this study was initiated. Sequential extraction analyses and batch leaching experiments were also performed using the coal ash samples collected from the disposal site. The results suggest the important roles of siderite (FeCO₃) precipitation/dissolution and soil cover, which have been ignored previously. Arsenic levels in the porewater were very low (average of 10 μg L⁻¹) when the site was covered with soil due to coprecipitation with siderite. The soil cover enabled the creation of anoxic conditions, which raised the Fe concentration by the reductive dissolution of Fe-(hydr)oxides. Because of the high alkalinity generated from the alkaline coal ash, even a small increase in the Fe concentration (0.66 mg L⁻¹ on average) could cause siderite precipitation. When the soil cover was removed, however, an oxidizing condition was created and triggered the precipitation of dissolved Fe as (hydr)oxides. As a result, the dissolution of previously precipitated As-rich siderite caused higher As concentration in the porewater (average of 345 μg L⁻¹).     

In vitro assessment of AhR-mediated activities of TCDD in mixture with humic substances

Humic substances (HS) are ubiquitous natural products of decomposition of dead organic matter. HS is present in most freshwaters at concentrations ranging from 0.5 to 50 mg L⁻¹. Organic carbon can represent 20% dry weight of sediments. Recently, the interaction of dissolved HS with the aryl hydrocarbon receptor (AhR) has been demonstrated. The AhR is a cytosolic receptor to which persistent organic pollutants (POPs) can bind and many of their toxic effects are mediated through interactions with this receptor. We describe in vitro effects (using H4IIE-luc cells) of binary mixtures of various HS with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), since in contaminated environments these compounds occur simultaneously. Six out of 12 HS samples activated AhR even at environmentally relevant concentrations (17 mg L⁻¹), but did not reach the full AhR-activation even at excessive concentration. In simultaneous exposure of H4IIE-luc to HS (17 mg L⁻¹) and TCDD (1.2 pM) without any preincubation prior to exposure, either significant additive or facilitative effects were observed. No negative interactions, due to possible sorption of TCDD to HS was observed. Nevertheless, if the HS–TCDD binary mixture was preincubated for 6 days prior to the exposure on H4IIE-luc cells, the additive and facilitative effects were less due to possible sorption of TCDD onto HS. Similar results were obtained from analogous experiments with greater concentrations of both TCDD and HS.     

The change of gaseous carbon fluxes following the switch of dominant producers from macrophytes to algae in a shallow subtropical lake of China

Successions of lake ecosystems from clear-water, macrophyte-rich conditions into turbid states with abundant phytoplankton have taken place in many shallow lakes in China. However, little is know about the change of carbon fluxes in lakes during such processes. We conducted a case study in Lake Biandantang to investigate the change of carbon fluxes during such a regime shift. Dissolved aquatic carbon and gaseous carbon (methane (CH₄) and carbon dioxide (CO₂)) across air–water interface in three sites with different vegetation covers and compositions were studied and compared. CH₄ emissions from three sites were 0.62±0.36, 0.70±0.36, and 1.31±0.57 mg m⁻² h⁻¹, respectively. Correlation analysis showed that macrophytes, rather than phytoplankton, directly positively affected CH₄ emission. CO₂ fluxes of three sites in Lake Biandantang were significantly different, and the average values were 77.8±20.4, 52.2±14.1 and 3.6±26.8 mg m⁻² h⁻¹, respectively. There were an evident trend that the larger macrophyte biomass, the lower CO₂ emissions. Correlation analysis showed that in different sites, dominant plant controlled CO₂ flux across air–water interface. In a year cycle, the percents of gaseous carbon release from lake accounting for net primary production were significantly different (from 39.3% to 2.8%), indicating that with the decline of macrophytes and regime shift, the lake will be a larger carbon source to the atmosphere.     

Chemical compositions and radiative properties of dust and anthropogenic air masses study in Taipei Basin, Taiwan, during spring of 2004

Asia is one of the major sources of not only mineral dust but also anthropogenic aerosols. Continental air masses associated with the East Asian winter monsoon always contain high contents of mineral dust and anthropogenic species and transported southeastward to Taiwan, which have significant influences on global atmospheric radiation transfer directly by scattering and absorbing solar radiation in each spring. However, few measurements for the long-range transported aerosol and its optical properties were announced in this area, between the Western Pacific and the southeastern coast of Mainland China. The overall objective of this work is to quantify the optical characteristics of different aerosol types in the Eastern Asian. In order to achieve this objective, meteorological parameters, concentrations of PM₁₀ and its soluble species, and optical property of atmospheric scattering coefficients were measured continuously with 1 h time-resolved from 11 February to 7 April 2004 in Taipei Basin (25°00′N, 121°32′E). In this work, the dramatic changes of meteorological parameters such as temperature and winds were used to determine the influenced period of each air mass. Continental, strong continental, marine, and stagnant air masses defined by the back-trajectory analysis and local meteorology were further characterized as long-range transport pollution, dust, clean marine, and local pollution aerosols, respectively, according to the diagnostic ratios. The aerosol mass scattering efficiency of continental pollution, dust, clean marine, and local pollution aerosols were ranged from 1.3 to 1.6, 0.7 to 1.0, 1.4 and 1.4 to 2.3 m² g⁻¹, respectively. Overall, there are two distinct populations of aerosol mass scattering efficiencies, one for an aerosol chemical composition dominated by dust (<1.0 m² g⁻¹) and the other for an aerosol chemical composition dominated by anthropogenic pollutants (1.3–2.3 m² g⁻¹), which were similar to the previous measurements with high degree of temporal resolution.     

Atmospheric deposition and canopy exchange processes in alpine forest ecosystems (northern Italy)

Throughfall and bulk precipitation chemistry were studied for five years (June 1994–May 1999) at two high elevation forest sites (Val Gerola and Val Masino) which were known to differ in terms of tree health, as assessed by live crown condition. The ion concentration of bulk precipitation samples did not differ significantly between sites, except for Mg²⁺, while the throughfall concentrations differed in the measured values of H⁺, N-NO₃⁻, Cl⁻, Na⁺, K⁺, DOC and weak organic acids. The results of the application of the canopy exchange model indicated a higher contribution from the dry deposition of N-NO₃⁻, N-NH₄⁺ and H⁺ at Val Gerola, where the damage symptoms were more evident. In addition, the canopy leaching of Ca²⁺, K⁺ and weak organic acids were 47%, 21% and 27% higher at Val Gerola than at Val Masino. Annual SO₄²⁻ deposition fluxes (21.3 kg ha⁻¹ yr⁻¹ at Val Masino and 23.6 kg ha⁻¹ yr⁻¹ at Val Gerola) were similar to those reported for moderately polluted European and U.S. sites. Annual N loads were 13.6 and 13.1 kg ha⁻¹ yr⁻¹ in the bulk input, and 15.0 and 18.0 kg ha⁻¹ yr⁻¹ in throughfall inputs, at Val Masino and Val Gerola, respectively. The contribution of the organic fraction to the total N atmospheric deposition load is significant, constituting 17% of the bulk flux and 40% of the throughfall flux. Measured nitrogen loads exceed the critical nutrient loads by several kg N ha⁻¹ at both stations. In particular the nitrogen throughfall load at Val Gerola was about 3 times higher than the critical values.     

The toxicity of sulfamethazine to Daphnia magna and its additivity to other veterinary sulfonamides and trimethoprim

Sulfonamides (SAs), the oldest chemotherapeutic agents used for antimicrobial therapy, still play an important role in veterinary mass treatments. Consequently, traces of these compounds, alone or in combinations, have been repeatedly detected in the environment. Sulfamethazine (SMZ) deserves particular attention not only because it is the most used veterinary SA, but also due to its proven effects on fertility in mice and on thyroid hormone homeostasis in rats. In this study, after evaluating the acute toxicity to Daphnia magna of six veterinary SAs and trimethoprim (TMP), the additivity of SMZ to each other compound was tested using the isobologram method. Two reproduction tests on the same biological model were also performed in order to derive LOEC and NOEC of SMZ. The acute EC₅₀ was in the range 131–270 mg L⁻¹ for all the compounds tested with the exception of sulfaguanidine (EC₅₀ = 3.86 mg L⁻¹). In acute binary tests SMZ showed a complex interaction with sulfaquinoxaline (superadditivity, additivity or subadditivity) at the three different combination ratios tested, simple additivity to TMP and less than additive interaction when paired to the other SAs. LOEC and NOEC of SMZ obtained from reproduction tests were 3.125 and 1.563 mg L⁻¹, respectively. In conclusion, SMZ should not harm the crustacean population at environmentally realistic concentrations. Its toxicity is comparable to that of other systemic SAs, and their binary interactions are less than additive. The same can not be entirely said for enteric SAs, and considering that these compounds are administered at high doses and mostly excreted in unmetabolised form, further evaluation of their impact to the aquatic environment seems advisable.     

Sequential coupling of bio-augmented permeable reactive barriers for remediation of 1,1,1-trichloroethane contaminated groundwater

Sequential coupling of high-density luffa sponge (HDLS) immobilized microorganism and permeable reactive barriers (IM Bio-PRBs) was superior to intimate coupling of free microorganism and permeable reactive barriers (FM Bio-PRBs) for remediation of 1,1,1-trichloroethane contaminated groundwater. IM Bio-PRBs had much better performance to removal 1,1,1-trichloroethane (1,1,1-TCA) and prevent the transport of 1,1,1-TCA and inorganic ions (NO₃^?, PO₄^3?, and SO₄^2?). The majority of them were prevented and accumulated in upgradient of IM Bio-PRBs. 1,1,1-TCA and inorganic ions in there contributed to the much faster growth of microorganism in upgradient aquifer. Therefore, the removal of 1,1,1-TCA and consumption of inorganic ions in upgradient of Bio-PRBs played a constructive role in reducing the processing load of following zero-valent iron (ZVI) PRBs and the negative effect of free microorganism cells (biological clogging) and inorganic ions (chemical clogging) on Bio-PRB permeability. In addition, IM Bio-PRBs were more conducive to accelerate the removal of 1,1,1-TCA in long-term remediation and 1,1,1-TCA residual concentration significantly lower than the safety standard of 0.2 mg L^?1. The change of terminal by-products of 1,1,1-TCA contaminated groundwater in Bio-PRBs showed that 1,1,1-TCA could be effectively de-chlorinated and mineralized in Bio-PRBs. The reductant H₂S (prolong the service life of ZVI-PRBs) was much more produced and utilized in IM Bio-PRBs. Taken together, sequentially coupled IM Bio-PRBs had a better overall performance, and its service life could be prolonged. It was a different design and idea to update conventional PRB remediation technology and theory.