Nitrate and fluoride contamination in groundwater of an intensively managed agroecosystem: A functional relationship

A study was conducted to assess the potential of nitrate-nitrogen (NO₃-N) and fluoride (F) contamination in drinking groundwater as a function of lithology, soil characteristics and agricultural activities in an intensively cultivated district in India. Two hundred and fifty two groundwater samples were collected at different depths from various types of wells and analyzed for pH, electrical conductivity (EC), NO₃-N load and F content. Database on lithology, soil properties, predominant cropping systems, fertilizer and pesticide uses were also recorded for the district. The NO₃-N load in groundwater samples were low ranging from 0.12 to 6.58 μg mL^− 1 with only 8.7% of them contained greater than 3.0 μg mL^− 1 well below the 10 μg mL^− 1, the threshold limit fixed by WHO for drinking purpose. Samples from the habitational areas showed higher NO₃-N content over the agricultural fields. The content decreased with increasing depth of wells (r = − 0.25, P ≤ 0.01) and increased with increasing rate of nitrogenous fertilizer application (r = 0.90, P ≤ 0.01) and was higher in areas where shallow- rather than deep-rooted crops (r = − 0.28, P = ≤ 0.01, with average root depth) are grown. The NO₃-N load also decreased with increasing bulk density (r = − 0.73, P ≤ 0.01) and clay content (r = − 0.51, P ≤ 0.01) but increased with increasing hydraulic conductivity (r = 0.68, P ≤ 0.01), organic C (r = 0.78, P ≤ 0.01) and potential plant available N (r = 0.82, P ≤ 0.01) of soils. Fluoride content in groundwater was also low (0.02 to 1.15 μg mL^− 1) with only 4.0% of them exceeding 1.0 μg mL^− 1 posing a potential threat of fluorosis. On average, its content varied little spatially and along depth of sampling aquifers indicating little occurrence of F containing rocks/minerals in the geology of the district. The content showed a significant positive correlation (r = 0.234, P = ≤ 0.01) with the amount of phosphatic fertilizer (single super phosphate) used for agriculture. Results thus indicated that the groundwater of the study area is presently safe for drinking purpose but some anthropogenic activities associated with intensive cultivation had a positive influence on its loading with NO₃-N and F.     

Population growth away from the coastal zone: Thirty years of land use change and nutrient export in the Altamaha River, GA

We used more than thirty years of water quality monitoring data collected by the United States Geological Survey at several stations in the Altamaha River and its tributaries to examine the relationship between population density, agricultural land use, and nutrient export from the watershed. Population densities in the Altamaha River watershed increased during the study period, most notably in the upper watershed near metropolitan Atlanta, while agricultural land use declined throughout the watershed. NO_x, TN and P in rivers were related to human population densities, while OC and NH₄⁺ concentrations in rivers were apparently related to agricultural land use. A general pattern of increasing NO_x and TN and decreasing NH₄⁺, P and OC over time throughout the watershed reflected changing population and land use. The overall average load from the Altamaha River to the coastal zone during the study period was 1.1, 5.6, 16.9, 0.9 and 262 kmol km^− 2 yr^− 1, delivering 40, 197, 596, 30, and 9213 · 10⁶ mol yr^− 1 of NH₄⁺, NO_x, TN, P and OC, respectively, to the coastal zone. The nutrient export patterns suggest that N and P loading to rivers in the Altamaha River watershed was greatest in the upper watershed where high population densities were found, and in-stream processing, dilution, and only moderate inputs during transit through the lower watershed resulted in relatively low export from the watershed to coastal waters.     

Rhizosphere acidification of faba bean, soybean and maize

Interspecific facilitation on phosphorus uptake was observed in faba bean/maize intercropping systems in previous studies. The mechanism behind this, however, remained unknown. Under nitrate supply, the difference in rhizosphere acidification potential was studied by directly measuring pH of the solution and by visualizing and quantifying proton efflux of roots between faba bean (Vicia faba L. cv. Lincan No.5), soybean (Glycine max L. cv. Zhonghuang No. 17) and maize (Zea mays L. cv. Zhongdan No.2) in monoculture and intercrop, supplied without or with 0.2 mmol L^− 1 P as KH₂PO₄. The pH of the nutrient solution grown faba bean was lower than initial pH of 6.0 from day 1 to day 22 under P deficiency, whereas the pH of the solution with maize was declined from day 13 after treatment. Growing soybean increased solution pH irrespective of P supply. Under P deficiency, the proton efflux of faba bean both total (315.25 nmol h^− 1 plant^− 1) and specific proton efflux (0.47 nmol h^− 1 cm^− 1) was greater than that those of soybean (21.80 nmol h^− 1 plant^− 1 and 0.05 nmol h^− 1 cm^− 1, respectively). Faba bean had much more ability of rhizosphere acidification than soybean and maize. The result can explain partly why faba bean utilizes sparingly soluble P more effectively than soybean and maize do, and has an important implication in understanding the mechanism behind interspecific facilitation on P uptake by intercropped species.     

Polybrominated diphenyl ethers, perfluorinated alkylated substances, and metals in tile drainage and groundwater following applications of municipal biosolids to agricultural fields

Polybrominated diphenyl ethers (PBDEs), perfluorinated alkylated substances (PFAS), and metals were monitored in tile drainage and groundwater following liquid (LMB) and dewatered municipal biosolid (DMB) applications to silty-clay loam agricultural field plots. LMB was applied (93,500 L ha^− 1) in late fall 2005 via surface spreading on un-tilled soil (SS_LMB), and a one-pass aerator-based pre-tillage prior to surface spreading (AerWay SSD) (A). The DMB was applied (8 Mg dw ha^− 1) in early summer 2006 on the same plots by injecting DMB beneath the soil surface (DI), and surface spreading on un-tilled soil (SS_DMB). Key PBDE congeners (BDE-47, -99, -100, -153, -154, -183, -209) comprising 97% of total PBDE in LMB, had maximum tile effluent concentrations ranging from 6 to 320 ng L^− 1 during application-induced tile flow. SS_LMB application-induced tile mass loads for these PBDE congeners were significantly higher than those for control (C) plots (no LMB) (p < 0.05), but not A plots (p > 0.05). PBDE mass loss via tile (0-2 h post-application) as a percent of mass applied was ~ 0.04-0.1% and ~ 0.8-1.7% for A and SS_LMB, respectively. Total PBDE loading to soil via LMB and DMB application was 0.0018 and 0.02 kg total PBDE ha^− 1 yr^− 1, respectively. Total PBDE concentration in soil (0-0.2 m) after both applications was 115 ng g^− 1 dw, (sampled 599 days and 340 days post LMB and DMB applications respectively). Of all the PFAS compounds, only PFOS (max concentration = 17 ng L^− 1) and PFOA (12 ng L^− 1) were found above detectable limits in tile drainage from the application plots. Mass loads of metals in tile for the LMB application-induced tile hydrograph event, and post-application concentrations of metals in groundwater, showed significant (p < 0.05) land application treatment effects (SS_LMB > A > C for tile and SS_LMB and A > C for groundwater for most results). Following DMB application, no significant differences in metal mass loads in tile were found between SS_DMB and DI treatments (PBDE/PFAS were not measured). But for many metals (Cu, Se, Cd, Mo, Hg and Pb) both SS_DMB and DI loads were significantly higher than those from C, but only during < 100 days post DMB application. Clearly, pre-tilling the soil (e.g., A) prior to surface application of LMB will reduce application-based PBDE and metal contamination to tile drainage and shallow groundwater. Directly injecting DMB in soil does not significantly increase metal loading to tile drains relative to SS_DMB, thus, DI should be considered a DMB land application option.     

Temporal analysis of net fluvial methylmercury loading in a dystrophic and a clear water lake

The concentration of methylmercury (MeHg) in aquatic ecosystems is the net result of the highly dynamic abiotic and biotic processes of mercury methylation and demethylation. In this study, we conduct an examination of the net fluvial loading of methylmercury (MeHg_Net = MeHg_Watershed − MeHg_{Lake outflow}) across a 3 year time frame in both a dystrophic lake and an oligotrophic lake. A significant portion of MeHg_Net variance in both lakes could be attributed to a seasonal pattern (11.4%, p = 0.009; oligotrophic, and 27.0%, p < 0.0001; dystrophic) which in both cases, was most correlated with air temperature. The dystrophic lake appeared to be a net source of methylmercury (MeHg_Net = − 1.9 ± 0.3 mg MeHg d^− 1) while the oligotrophic lake appeared to be a net sink (MeHg_Net = 0.4 ± 0.2 mg MeHg d^− 1), indicating that there was net methylation in the dystrophic lake and net demethylation in the oligotrophic lake. Higher MeHg loading to the lakes occurred during the summer and between seasons there was a difference in MeHg_Net of 1.1 ±0.3 mg MeHg d^− 1 and 3.1 ± 0.6 mg MeHg d^− 1. Seasonal patterns of MeHg_Net in the oligotrophic lake lagged behind the dystrophic lake by 39 days. The short term variation in MeHg_Net was dominated by precipitation (t = 2.73, p = 0.008; dystrophic, t = 2.53, p = 0.017; oligotrophic).     

Removal of Pharmaceutical and Personal Care Products (PPCPs) under nitrifying and denitrifying conditions

The contribution of volatilization, sorption and transformation to the removal of 16 Pharmaceutical and Personal Care Products (PPCPs) in two lab-scale conventional activated sludge reactors, working under nitrifying (aerobic) and denitrifying (anoxic) conditions for more than 1.5 years, have been assessed. Pseudo-first order biological degradation rate constants (k_biol) were calculated for the selected compounds in both reactors. Faster degradation kinetics were measured in the nitrifying reactor compared to the denitrifying system for the majority of PPCPs. Compounds could be classified according to their k_biol into very highly (k_biol > 5 L g_SS⁻¹ d⁻¹), highly (1 < k_biol < 5 L g_SS⁻¹ d⁻¹), moderately (0.5 < k_biol < 1 L g_SS⁻¹ d⁻¹) and hardly (k_biol < 0.5 L g_SS⁻¹ d⁻¹) biodegradable.Results indicated that fluoxetine (FLX), natural estrogens (E1 + E2) and musk fragrances (HHCB, AHTN and ADBI) were transformed to a large extent under aerobic (>75%) and anoxic (>65%) conditions, whereas naproxen (NPX), ethinylestradiol (EE2), roxithromycin (ROX) and erythromycin (ERY) were only significantly transformed in the aerobic reactor (>80%). The anti-depressant citalopram (CTL) was moderately biotransformed under both, aerobic and anoxic conditions (>60% and >40%, respectively). Some compounds, as carbamazepine (CBZ), diazepam (DZP), sulfamethoxazole (SMX) and trimethoprim (TMP), manifested high resistance to biological transformation.Solids Retention Time (SRT_aerobic >50 d and <50 d; SRT_anoxic >20 d and <20 d) had a slightly positive effect on the removal of FLX, NPX, CTL, EE2 and natural estrogens (increase in removal efficiencies <10%). Removal of diclofenac (DCF) in the aerobic reactor was positively affected by the development of nitrifying biomass and increased from 0% up to 74%. Similarly, efficient anoxic transformation of ibuprofen (75%) was observed after an adaptation period of 340 d. Temperature (16-26 °C) only had a slight effect on the removal of CTL which increased in 4%.     

Interactions of land use and dynamic river conditions on sorption equilibria between benthic sediments and river soluble reactive phosphorus concentrations

Within-river cycling of P is a crucial link between catchment pollution sources and the resulting ecological impacts and integrates the biogeochemistry and hydrodynamics of river systems. This study investigates benthic sediment P sorption in relation to river soluble reactive phosphorus (SRP) concentrations during high- to low-flow changes in a major mixed land use river system in NE Scotland. We hypothesised that sediments comprised P sinks during moderate to higher flows but became P saturated with loss of buffering function during prolonged baseflow. Sediment characteristics were evaluated and equilibrium P concentrations (EPC₀) calculated using a standardised batch adsorption method (EPC₀ values 0.04-1.75 μmol P l⁻¹). Pollution-impacted tributaries (32-69% catchment agricultural land cover) had increased SRP concentrations (0.19-2.62 μmol P l⁻¹) and maintained EPC₀ < SRP values during changing flow conditions. Moorland-dominated tributaries and main stem sites had small SRP concentrations (0.03-0.19 μmol P l⁻¹) but showed EPC₀ > SRP values during summer baseflow so that sediments were indicated as P sources. This deviation from a geochemical sediment-water P equilibrium was attributed to biological accumulation of P from the water column into the sediments. In particular, large stores of sediment P accumulated in main stem reaches below agricultural tributaries and this may be consequential for sensitive downstream ecosystems. Hence, biogeochemical processes at the river bed may strongly influence river SRP cycling between geochemical and biotic pools. The nature of this internal reservoir of river P and its ecosystem interactions needs better understanding to enable best results to be attained from catchment mitigation actions designed to maintain/improve ecological status under the Water Framework Directive.     

Releasing behavior of zinc in recirculated bioreactor landfill

The purpose of this research was to determine the releasing behavior of zinc in municipal solid waste (MSW) in landfill site with respect to refuse and leachate as an inseparable system. Two simulated bioreactor landfills, one with leachate recirculation and the other without, were operated in room temperature for 320 days. Results showed that the content of zinc in MSW could amount to 591.29 ± 31.33-632.14 ± 18.98 µg g ^− 1 dry weight ^− 1 (DW ^− 1). It exceeded the set standard for “Environmental quality standard for soil” (≤ 500 µg g ^− 1 DW ^− 1) and had high potential environmental risk. The releasing behavior of zinc in refuse mainly experienced speciation of solid-Zn, Zn²⁺, ZnHCO₃⁺, ZnCO₃, Zn(OH)⁺, Zn(OH)₂, Zn(NH₃)₄²⁺, ZnS, etc. Zinc in refuse showed behaviors of staggered migration and retention, which corresponded with the degradation process of refuse in bioreactor landfill. The Zn²⁺ concentration in leachate, which varied correspondingly with releasing behavior of zinc in refuse, were 0.75 mg L ^− 1 to 3.13 mg L ^− 1 and had no great difference in landfill with different operation modes (CL and RL). However, the amount of Zn²⁺ leached out from refuse, which accounted for 28.70 mg and 130.67 mg after 320 day's operation, respectively. More attention should be paid to the inseparable system including refuse and leachate together.     

Organic and inorganic carbon concentrations and fluxes from managed and unmanaged boreal first-order catchments

Seasonal and between stream variation (catchment dependent variation) in losses of organic and inorganic carbon via downstream transport and outgassing of CO₂ into the atmosphere were studied in 11 small boreal catchments situated in close proximity to each other. Of these catchments four were undrained peatland rich catchments, four drained peatland rich catchments and three managed mineral soil-dominated catchments. Downstream export of total inorganic carbon (TIC) varied between 870 and 1400 kg km^− 2 a^− 1 and was rather consistent between the catchments, except in the case of the mineral soil-dominated catchment Kangaslampi, where export was only 420 kg km^− 2 a^− 1. The export of total organic carbon (TOC) varied between 2300 and 14,800 kg km^− 2 a^− 1 and was highest in peatland rich catchments. Peatland drainage decreased TIC and TOC concentrations in the long term, but did not affect lateral carbon export due to increased runoff from the catchments. Partial pressure of CO₂ in streams was the highest in undrained peatland rich catchments, but the outgassing of CO₂ into the atmosphere was also high from drained peatlands due to the higher discharge rate and long ditch networks. In mineral soil-dominated catchments both downstream export of carbon and emission into the atmosphere were low. TOC exports were compared in two climatically different years (2003 and 2007). The results indicate that climate change might alter the timing of the TOC export from the catchments, the importance of the spring ice melt diminishing and both snow cover and snow free period export increasing.     

Treating landfill leachate using passive aeration trickling filters; effects of leachate characteristics and temperature on rates and process dynamics

Biological ammoniacal-nitrogen (NH₄⁺-N) and organic carbon (TOC) treatment was investigated in replicated mesoscale attached microbial film trickling filters, treating strong and weak strength landfill leachates in batch mode at temperatures of 3, 10, 15 and 30 °C. Comparing leachates, rates of NH₄⁺-N reduction (0.126-0.159 g m^− 2 d^− 1) were predominantly unaffected by leachate characteristics; there were significant differences in TOC rates (0.072-0.194 g m^− 2 d^− 1) but no trend relating to leachate strength. Rates of total oxidised nitrogen (TON) accumulation (0.012-0.144 g m^− 2 d^− 1) were slower for strong leachates. Comparing temperatures, treatment rates varied between 0.029-0.319 g NH₄⁺-N m^− 2 d^− 1 and 0.033-0.251 g C m^− 2 d^− 1 generally increasing with rising temperatures; rates at 3 °C were 9 and 13% of those at 30 °C for NH₄⁺-N and TOC respectively. For the weak leachates (NH₄⁺-N < 140 mg l^− 1) complete oxidation of NH₄⁺-N was achieved. For the strong leachates (NH₄⁺-N 883-1150 mg l^− 1) a biphasic treatment response resulted in NH₄⁺-N removal efficiencies of between 68 and 88% and for one leachate no direct transformation of NH₄⁺-N to TON in bulk leachate. The temporal decoupling of NH₄⁺-N oxidation and TON accumulation in this leachate could not be fully explained by denitrification, volatilisation or anammox, suggesting temporary storage of N within the treatment system. This study demonstrates that passive aeration trickling filters can treat well-buffered high NH₄⁺-N strength landfill leachates under a range of temperatures and that leachate strength has no effect on initial NH₄⁺-N treatment rates. Whether this approach is a practicable option depends on a range of site specific factors.     

Photoassisted reduction of metal ions and organic dye by titanium dioxide nanoparticles in aqueous solution under anoxic conditions

The photoassisted reduction of metal ions and organic dye by metal-deposited Degussa P25 TiO₂ nanoparticles was investigated. Copper and silver ions were selected as the target metal ions to modify the surface properties of TiO₂ and to enhance the photocatalytic activity of TiO₂ towards methylene blue (MB) degradation. X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used to characterize the crystallinity, chemical species and morphology of metal-deposited TiO₂, respectively. Results showed that the particle size of metal-deposited TiO₂ was larger than that of Degussa P25 TiO₂. Based on XRPD patterns and XPS spectra, it was observed that the addition of formate promoted the photoreduction of metal ion by lowering its oxidation number, and subsequently enhancing the photodegradation efficiency and rate of MB. The pseudo-first-order rate constant (k_obs) for MB photodegradation by Degussa P25 TiO₂ was 3.94 × 10^− 2 min^− 1 and increased by 1.4-1.7 times in k_obs with metal-deposited TiO₂ for MB photodegradation compared to simple Degussa P25 TiO₂. The increase in mass loading of metal ions significantly enhanced the photodegradation efficiency of MB; the k_obs for MB degradation increased from 3.94 × 10^− 2 min^− 1 in the absence of metal ion to 4.64-7.28 × 10^− 2 min^− 1 for Ag/TiO₂ and to 5.14-7.61 × 10^− 2 min^− 1 for Cu/TiO₂. In addition, the electrons generated from TiO₂ can effectively reduce metal ions and MB simultaneously under anoxic conditions. However, metal ions and organic dye would compete for electrons from the illuminated TiO₂.     

Solar radiation disinfection of drinking water at temperate latitudes: Inactivation rates for an optimised reactor configuration

Solar radiation-driven inactivation of bacteria, virus and protozoan pathogen models was quantified in simulated drinking water at a temperate latitude (34°S). The water was seeded with Enterococcus faecalis, Clostridium sporogenes spores, and P22 bacteriophage, each at ca 1 × 10⁵ m L⁻¹, and exposed to natural sunlight in 30-L reaction vessels. Water temperature ranged from 17 to 39 °C during the experiments lasting up to 6 h. Dark controls showed little inactivation and so it was concluded that the inactivation observed was primarily driven by non-thermal processes. The optimised reactor design achieved S₉₀ values (cumulative exposure required for 90% reduction) for the test microorganisms in the range 0.63-1.82 MJ m⁻² of Global Solar Exposure (GSX) without the need for TiO₂ as a catalyst. High turbidity (840-920 NTU) only reduced the S₉₀ value by <40%. Further, when all S₉₀ means were compared this decrease was not statistically significant (prob. > 0.05). However, inactivation was significantly reduced for E. faecalis and P22 when the transmittance of UV wavelengths was attenuated by water with high colour (140 PtCo units) or a suboptimally transparent reactor lid (prob. < 0.05). S₉₀ values were consistent with those measured by other researchers (ca 1-10 MJ m⁻²) for a range of waters and microorganisms. Although temperatures required for SODIS type pasteurization were not produced, non-thermal inactivation alone appeared to offer a viable means for reliably disinfecting low colour source waters by greater than 4 orders of magnitude on sunny days at 34°S latitude.     

Mercury bioacumulation in four tissues of Podocnemis erythrocephala (Podocnemididae: Testudines) as a function of water parameters

A number of environmental factors influence the dynamics of Hg in aquatic ecosystems, yet few studies have examined these factors for turtles, especially from South America. Red-headed river turtle (Podocnemis erythrocephala) is easy to capture in the black waters of Rio Negro, making it the turtle species that is consumed most often by people of the region. In this study, environmental factors and turtle size were investigated to determine their influence on the Hg concentration in blood, muscle, liver and carapace of the red-headed river turtle. Factors investigated included turtle length, pH, dissolved organic carbon and availability of potential methylation sites (floodplain forests and hydromorphic soils). The study was conducted in the Rio Negro basin, where we collected water and turtle blood, muscle, liver and carapace samples from 12 tributaries for chemical analysis. Through radar imagery and existing soil maps with GIS, the percentage of alluvial floodplains and hydromorphic soils (potential methylation sites) was estimated for each drainage basin at sampling points. The mean Hg concentration in blood of P. erythrocephala was 1.64 ng g^− 1 (SD = 1.36), muscle 33 ng g^− 1 (SD = 11), liver 470 ng g^− 1 (SD = 313) and carapace 68 ng g^− 1 (SD = 32). Sex or length did not influence the Hg concentration in P. erythrocephala blood, muscle and liver, but Hg increased in carapace tissue when length size increased (ANCOVA p = 0.007). In the multiple regression analysis, none of the environmental factors studied had a significant relation with blood, muscle, liver and carapace. P. erythrocephala moves among habitats and in the open and interconnected aquatic systems of the Amazon basin, characterized by high levels of limnological variability, a good bioindicator of Hg concentration needs to be relatively sedentary to represent a specific habitat. However, the levels of Hg in liver were sufficient to pose a potential risk to humans that consume them, suggesting the usefulness of P. erythrocephala as a bioindicator.     

Gas-particle partitioning and seasonal variation of polycyclic aromatic hydrocarbons in the atmosphere of Zonguldak, Turkey

Atmospheric concentrations and gas-particle partition coefficients were determined for polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of Zonguldak, Turkey between May 2007 and April 2008. Total concentrations of PAHs ranged from 0.52 ng m^− 3 to 636 ng m^− 3 in the particle phase and from 5.60 ng m^− 3 to 725 ng m^− 3 in the gas phase. The annual mean concentrations of PAHs in the particle and gas phase were found to be 114 ng m^− 3 and 184 ng m^− 3, respectively. Significant seasonal variations of particle and gas phase PAH concentrations were observed with higher levels during cold period. The distribution of PAHs between the particle and gas phase was investigated and it was found that three ring PAHs were associated primarily with the gas phase, four ring PAHs were distributed almost equally between the two phases and five and six ring PAHs were mainly associated with the particle phase. Gas-particle partition coefficients (K_p) of PAHs have been calculated and correlated with their subcooled liquid vapor pressures (P_Lº). The slopes (m_r) varied from − 0.63 to − 0.23 were far from the theoretical value (−1) due to the short distance between the sampling point and the emission sources. The relationships between temperature and gas phase partial pressures of PAHs were examined using the Clausius-Clapeyron equation and the obtained positive slopes indicated that PAH concentrations increased with decreasing air temperature as a result of high dominance of local emissions.     

Heterogenous photocatalytic degradation kinetics and detoxification of an urban wastewater treatment plant effluent contaminated with pharmaceuticals

Degradation kinetics and mineralization of an urban wastewater treatment plant effluent contaminated with a mixture of pharmaceutical compounds composed of amoxicillin (10 mg L⁻¹), carbamazepine (5 mg L⁻¹) and diclofenac (2.5 mg L⁻¹) by TiO₂ photocatalysis were investigated. The photocatalytic effect was investigated using both spiked distilled water and actual wastewater solutions. The process efficiency was evaluated through UV absorbance and TOC measurements. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Lepidium sativum) was performed to evaluate the potential toxicity of the oxidation intermediates. A pseudo-first order kinetic model was found to fit well the experimental data. The mineralization rate (TOC) of the wastewater contaminated with the pharmaceuticals was found to be really slow (t_1/2 = 86.6 min) compared to that of the same pharmaceuticals spiked in distilled water (t_1/2 = 46.5 min). The results from the toxicity tests of single pharmaceuticals, their mixture and the wastewater matrix spiked with the pharmaceuticals displayed a general accordance between the responses of the freshwater aquatic species (P. subscapitata > D. magna). In general the photocatalytic treatment did not completely reduce the toxicity under the investigated conditions (maximum catalyst loading and irradiation time 0.8 g TiO₂ L⁻¹ and 120 min respectively).     

Tree-based modeling of complex interactions of phosphorus loadings and environmental factors

Phosphorus (P) enrichment has been observed in the historic oligotrophic Greater Everglades in Florida mainly due to P influx from upstream, agriculturally dominated, low relief drainage basins of the Everglades Agricultural Area (EAA). Our specific objectives were to: (1) investigate relationships between various environmental factors and P loads in 10 farm basins within the EAA, (2) identify those environmental factors that impart major effects on P loads using three different tree-based modeling approaches, and (3) evaluate predictive models to assess P loads. We assembled thirteen environmental variable sets for all 10 sub-basins characterizing water level management, cropping practices, soils, hydrology, and farm-specific properties. Drainage flow and P concentrations were measured at each sub-basin outlet from 1992-2002 and aggregated to derive monthly P loads. We used three different tree-based models including single regression trees (ST), committee trees in Bagging (CTb) and ARCing (CTa) modes and ten-fold cross-validation to test prediction performances. The monthly P loads (MPL) during the monitoring period showed a maximum of 2528 kg (mean: 103 kg) and maximum monthly unit area P loads (UAL) of 4.88 kg P ha^− 1 (mean: 0.16 kg P ha^− 1). Our results suggest that hydrologic/water management properties are the major controlling variables to predict MPL and UAL in the EAA. Tree-based modeling was successful in identifying relationships between P loads and environmental predictor variables on 10 farms in the EAA indicated by high R² (> 0.80) and low prediction errors. Committee trees in ARCing mode generated the best performing models to predict P loads and P loads per unit area. Tree-based models had the ability to analyze complex, non-linear relationships between P loads and multiple variables describing hydrologic/water management, cropping practices, soil and farm-specific properties within the EAA.     

Removal of organics in constructed wetlands with horizontal sub-surface flow: a review of the field experience

Constructed wetlands with horizontal sub-surface flow (HF CWs) have successfully been used for treatment various types of wastewater for more than four decades. Most systems have been designed to treat municipal sewage but the use for wastewaters from agriculture, industry and landfill leachate in HF CWs is getting more attention nowadays. The paper summarizes the results from more than 400 HF CWs from 36 countries around the world. The survey revealed that the highest removal efficiencies for BOD₅ and COD were achieved in systems treating municipal wastewater while the lowest efficiency was recorded for landfill leachate. The survey also revealed that HF CWs are successfully used for both secondary and tertiary treatment. The highest average inflow concentrations of BOD₅ (652 mg l^− 1) and COD (1865 mg l^− 1) were recorded for industrial wastewaters followed by wastewaters from agriculture for BOD₅ (464 mg l^− 1) and landfill leachate for COD (933 mg l^− 1). Hydraulic loading data reveal that the highest loaded systems are those treating wastewaters from agriculture and tertiary municipal wastewaters (average hydraulic loading rate 24.3 cm d^− 1). On the other hand, landfill leachate systems in the survey were loaded with average only 2.7 cm d^− 1. For both BOD₅ and COD, the highest average loadings were recorded for agricultural wastewaters (541 and 1239 kg ha^− 1 d^− 1, respectively) followed by industrial wastewaters (365 and 1212 kg ha^− 1 d^− 1, respectively). The regression equations for BOD₅ and COD inflow/outflow concentrations yielded very loose relationships. Much stronger relationships were found for inflow/outflow loadings and especially for COD. The influence of vegetation on removal of organics in HF CWs is not unanimously agreed but most studies indicated the positive effect of macrophytes.     

Pharmaceutical and personal care products in tile drainage following surface spreading and injection of dewatered municipal biosolids to an agricultural field

Land application of municipal biosolids can be a source of environmental contamination by pharmaceutical and personal care products (PPCPs). This study examined PPCP concentrations/temporally discrete mass loads in agricultural tile drainage systems where two applications of biosolids had previously taken place. The field plots received liquid municipal biosolids (LMB) in the fall of 2005 at an application rate of ∼ 93,500 L ha^− 1, and a second land application was conducted using dewatered municipal biosolids (DMB) applied at a rate of ∼ 8 Mt dw ha^− 1 in the summer of 2006. The DMB land application treatments consisted of direct injection (DI) of the DMB beneath the soil surface at a nominal depth of ∼ 0.11 m, and surface spreading (SS) plus subsequent tillage incorporation of DMB in the topsoil (∼ 0.10 m depth). The PPCPs examined included eight pharmaceuticals (acetaminophen, fluoxetine, ibuprofen, gemfibrozil, naproxen, carbamazepine, atenolol, sulfamethoxazole), the nicotine metabolite cotinine, and two antibacterial personal care products triclosan and triclocarban. Residues of naproxen, cotinine, atenolol and triclosan originating from the fall 2005 LMB application were detected in tile water nearly nine months after application (triclocarban was not measured in 2005). There were no significant differences (p > 0.05) in PPCP mass loads among the two DMB land application treatments (i.e., SS vs. DI); although, average PPCP mass loads late in the study season (> 100 days after application) were consistently higher for the DI treatment relative to the SS treatment. While the concentration of triclosan (∼ 14,000 ng g^− 1 dw) in DMB was about twice that of triclocarban (∼ 8000 ng g^− 1 dw), the average tile water concentrations for triclosan were much higher (43 ± 5 ng L^− 1) than they were for triclocarban (0.73 ± 0.14 ng L^− 1). Triclosan concentrations (maximum observed in 2006 ∼ 235 ng L^− 1) in tile water resulting from land applications may warrant attention from a toxicological perspective.     

Indoor/outdoor relationship of fine particles less than 2.5 μm (PM2.5) in residential homes locations in central Indian region

The high levels in developing countries and the apparent scale of its impact on the global burden of disease underline the importance of particulate as an environmental health risk and the consequence need for monitoring them particularly in indoor microenvironment. PM2.5 μm, 1.0 μm, 0.5 μm and 0.25 μm were measured inside and outside 14 residential homes located in different microenvironment during a six-month period (October 2007–March 2008) in Agra located in the central region of India. Particulate mass concentrations were measured using Grimm aerosol spectrometer for 24 h inside and outside the homes located in roadside, rural and urban area, along with the field survey study done in the same region. The indoor average concentrations recorded for PM_2.5, PM_1.0, PM_0.5 and PM_0.25 were maximum for the rural homes (173.03 μgm⁻³, 133.26 μgm⁻³, 96.02 μgm⁻³, 8.56 μgm⁻³) followed by roadside homes (137.93 μgm⁻³, 117.09 μgm⁻³, 68.17 μgm⁻³, 8.55 μgm⁻³) and then by urban homes (135.55 μgm⁻³, 102.92 μgm⁻³, 38.38 μgm⁻³, 6.35 μgm⁻³). The average I/O ratios for PM_2.5, PM_1.0, PM_0.5 and PM_0.25 in roadside and rural areas were close to or above 1.00 and less than 1.00 for urban areas. The I/O ratios obtained were linked to the indoor activities using occupant's diary entries. The positive values of correlation coefficient (r) also indicated the indoor concentrations of particulate matter were correlated with the corresponding outdoor concentrations.     

Heavy metals: confounding factors in the response of New Zealand freshwater fish assemblages to natural and anthropogenic acidity

Acidification of freshwaters is a global phenomenon, occurring both through natural leaching of organic acids and through human activities from industrial emissions and mining. The West Coast of the South Island, New Zealand, has both naturally acidic and acid mine drainage (AMD) streams enabling us to investigate the response of fish communities to a gradient of acidity in the presence and absence of additional stressors such as elevated concentrations of heavy metals. We surveyed a total of 42 streams ranging from highly acidic (pH 3.1) and high in heavy metals (10 mg L⁻¹ Fe; 38 mg L⁻¹ Al) to circum-neutral (pH 8.1) and low in metals (0.02 mg L⁻¹ Fe; 0.05 mg L⁻¹ Al). Marked differences in pH and metal tolerances were observed among the 15 species that we recorded. Five Galaxias species, Anguilla dieffenbachii and Anguillaaustralis were found in more acidic waters (pH< 5), while bluegill bullies (Gobiomorphus hubbsi) and torrentfish (Cheimarrichthys fosteri) were least tolerant of low pH (minimum pH 6.2 and 5.5, respectively). Surprisingly, the strongest physicochemical predictor of fish diversity, density and biomass was dissolved metal concentrations (Fe, Al, Zn, Mn and Ni) rather than pH. No fish were detected in streams with dissolved metal concentrations > 2.7 mg L⁻¹ and nine taxa were only found in streams with metal concentrations < 1 mg L⁻¹. The importance of heavy metals as critical drivers of fish communities has not been previously reported in New Zealand, although the mechanism of the metal effects warrants further study. Our findings indicate that any remediation of AMD streams which seeks to enable fish recolonisation should aim to improve water quality by raising pH above ≈ 4.5 and reducing concentrations of dissolved Al and Fe to < 1.0 mg L⁻¹.