Search

Residual pharmaceutical compounds (PCs) are among the emerging organic contaminants detected in our water cycle. Diclofenac (Dic) is one of the commonly detected pharmaceutical contaminant in aquatic systems. This study was designed to investigate the degradation and mineralization of Dic in aqueous solutions by ionizing radiation emitted from radioactive Co60 under several conditions. Ultra-performance liquid chromatography, ion chromatography and TOC measurements confirmed the radiolytic degradation of Dic. The absorbed doses needed to degrade 99% Dic at 25, 50, 100, 190, 280, and 480 μM were 0.560, 0.950, 1.950, 4.000, 5.400, and 7.400 kGy, respectively. This process follows pseudo-first-order kinetics. The γ-ray/N 2 O system decreased the dose required to degrade 99% to 1.47 kGy. The presence of bromide anions inhibits degradation. Remarkably, adding H 2 O 2 , S 2 O 8 2−, or N 2 O promotes mineralization. Conversely, the absence of dissolved oxygen hinders mineralization. This study provides a viable finding that ionizing radiation are useful tolls to remedy water containing pharmaceutical organic compounds. Unlabelled Image • The kinetics of diclofenac radiolysis by Co60 was studied at several concentrations. • The effect of hydrated electron was discussed. • Bromide anion inhibits radiolysis. • Persulfate and hydrogen peroxide addition and nitrous oxide saturation were probed. • The main organic byproducts proposed in the literature are summarized. [ABSTRACT FROM AUTHOR]

In this study, the strategy of combining radiation with ferrate oxidation was proposed to decrease the adsorbed dosse and enhance the mineralization of carbamazepine in aqueous solution. Compared to single radiation (800 Gy), the combined process of ferrate pretreatment and radiation required lower dose (600 Gy) for totally removing carbamazepine. During the combined process, the removal efficiency of total organic carbon (TOC) reached 22.2%. However, the removal efficiencies of carbamazepine and TOC decreased when ferrate and radiation were used simultaneously, indicating that the addition of ferrate during the radiation process had negative effect on the removal of carbamazepine. In contrast, the radiation followed by ferrate oxidation presented the best performance in decreasing the absorbed dose and enhancing the mineralization of carbamazepine. Carbamazepine could be completely removed under all conditions. TOC removal efficiency reached 18.3%, 31.3%, 52.9% and 60.6%, respectively, at the adsorbed dose of 100, 300, 600 and 800 Gy when 0.4 mM ferrate was adopted. The enhanced TOC removal could be due to the enhanced oxidation capacity of ferrate caused by the pH decrease at the end of radiation and the further oxidation of intermediate products formed during the radiation process by ferrate. Seven degradation products were identified in total, and thus the degradation pathway of carbamazepine was proposed. This study provides a possible way to decrease the adsorbed dose and enhance the mineralization of carbamazepine by radiation. Unlabelled Image • The combined process of radiation and ferrate oxidation was developed. • Radiation followed by ferrate oxidation effectively decreased absorbed dose. • Radiation followed by ferrate oxidation significantly increased mineralization. • Combining radiation with ferrate oxidation is promising for antibiotics removal. [ABSTRACT FROM AUTHOR]

Electro-oxidation (EO) of synthetic wastewater containing amoxicillin (AMT) antibiotic as a model pollutant was performed using dimensionally stable Ti/RuO 2 electrodes in a continuous reactor set-up. Response surface methodology (RSM) was used for optimization of continuous EO process. Individual and interactive effects of initial pH of synthetic wastewater (2−10), applied current, I (0.25–1.25 A), elapsed time, t (20–180 min) and retention time, R T (15–195 min) on AMT removal, total organic carbon (TOC) removal and specific energy consumption (SEC, kWh (g TOC removed)−1) were investigated. At optimum conditions (pH = 7.53, I = 0.7 A, R T = 175.6 min, t = 128.89 min), 51.64% and 37.82% AMT and TOC removal was achieved, with SEC value of 0.408 kWh (g TOC removed)−1. AMT and TOC removal at optimum conditions was found to follow pseudo-first order kinetics. Mineralization current efficiency for optimum run of continuous EO came out to be 9.81%. Furthermore, 8 transformation products/reaction intermediates of AMT (ARIs) were determined by UPLC-Q-TOF-MS analysis, and subsequently, a plausible degradation scheme of AMT by anodic oxidation and cathodic reduction using Ti/RuO 2 electrodes was proposed. Unlabelled Image • Ti/RuO 2 anode was used for amoxicillin (AMT) mineralization in continuous EO. • 37.82% TOC removal showed partial mineralization and AMT presence in degraded form. • Eight transformation products/reaction intermediates of AMT (ARIs) were determined. • Generated chlorinated ARIs underwent dechlorination via cathodic reduction. • A plausible AMT degradation mechanism was proposed. [ABSTRACT FROM AUTHOR]

DDT and its main metabolites (DDTs) are still the residual contaminants in soil. Sequential anaerobic-aerobic cycling has long been approved for enhancing the degradation of DDTs in soil. However, there is a lack of study investigating whether anaerobic-aerobic cycling would enhance the mineralization of DDT, and what a kind of anaerobic-aerobic management regimes would be optimal. To fill these gaps, the fate of 14C-DDT under different flooding-drying cycles was examined in a paddy soil by monitoring its mineralization and bioavailability. The results show the total mineralization of 14C-DDT in 314 days accounted for 1.01%, 1.30%, and 1.41%, individually for the treatments subjected to one, two, and three flooding-drying cycles. By comparison, the treatment subjected to the permanently aerobic phase had only 0.12% cumulative mineralization. Shorter intervals and multiple flooding-drying cycles enhanced the mineralization of 14C-DDT, however, reduced its bioavailability. Therefore, the enhanced mineralization was explained from an abiotic pathway as predicted by the one-electron reduction potential (E 1), the Fukui function for nucleophilic attack (f +) and the steps for anaerobic decarboxylation. From a practical view, it is important to investigate how the anaerobic-aerobic interval and frequency would affect the degradation and mineralization of DDT, which is very essential in developing remediation strategies. Unlabelled Image • Shorter-multiple flooding-drying cycles reduced DDT bioavailability in a paddy soil. • Shorter-multiple flooding-drying cycles enhanced DDT mineralization in a paddy soil. • E 1 values and nucleophilic attacking potential explained the degradation mechanism. • α-FeOOH has no significant effect on DDT mineralization in the paddy soil. [ABSTRACT FROM AUTHOR]

We studied long-term (64.5 weeks) biodegradation of diesel fuel, diesel/biodiesel blends (B10-B90) and biodiesel fuels in urban soil microcosms containing indigenous microorganisms, or indigenous microorganisms augmented with a hydrocarbon-degrading bacterial community. Mineralization extent (mmol of CO 2 per day) of B10-B30 blends was smaller compared with diesel fuel at both short- (28 days) and long-term (109 days), and increased with biodiesel content. Priming with hydrocarbon degraders accelerated mineralization in the short-term (by up to 140%), with highest influence using blends with lower biodiesel content, but did not significantly influence kinetics and mineralization extent in the long-term. Although the biodiesel fraction was degraded completely within 64.5 weeks, 3–12% of the total aromatic and aliphatic hydrocarbons remained in the microcosms. Barcoded 16S rRNA gene MiSeq sequencing analysis revealed a significant effect of blend type on the community structure, with a marked enrichment of Sphingobacteriia and Actinobacteria classes. However, no significant influence was determined in the long-term, suggesting that the inoculated bacterial community may not have survived. Our findings show that biodiesel is preferentially degraded in urban soil and suggest that the value of bioaugmentation for bioremediating biodiesel fuels with hydrocarbon-degrading bacteria is limited to short-term exposures to lower (B10-B30) blends. Unlabelled Image • Long-term (64.5 weeks) biodegradation of diesel/biodiesel in urban soil was studied. • 3–12% of the total aromatic and aliphatic hydrocarbons remained in the microcosms. • Effect of bioaugmentation was evaluated. • MiSeq sequencing analysis revealed a significant effect of blend type. • No significant influence of bioaugmentation was determined in the long-term. [ABSTRACT FROM AUTHOR]

Abstract Glyphosate is the best-selling and the most-used broad-spectrum herbicide worldwide. Microbial conversion of glyphosate to CO 2 and biogenic non-extractable residues (bioNER) leads to its complete degradation. The degradation of glyphosate may vary in different soils and it depends on environmental conditions and soil properties. To date, the influence of temperature, soil pH and total organic carbon (TOC) on microbial conversion of glyphosate to bioNER has not been investigated yet. The pH or TOC of an agricultural original soil (pH 6.6, TOC 2.1%) was modified using sulfuric acid or farmyard manure (FYM), respectively. Each treatment: original (I), 3% TOC (II), 4% TOC (III), pH 6.0 (IV) and pH 5.5 (V) was amended with 13C 3 15N-glyphosate and incubated at 10 °C, 20 °C and 30 °C for 39 days. The temperature was the main factor controlling the mineralization and the extractable 13C 3 15N-glyphosate, whereas higher TOC content and lower pH resulted in enhanced formation of 13C-bioNER. After 39 days the cumulative mineralization of 13C-glyphosate was in the range of 12–22% (10 °C), 37–47% (20 °C) and 43–54% (30 °C). Extractable residues of 13C-glyphosate were in the range of 10–21% (10 °C) and 4–10% (20 °C and 30 °C); whereas those of 15N-glyphosate were as follows 20–32% (10 °C) and 12–25% (20 °C and 30 °C). The 13C-NER comprised about 53–69% of 13C-mass balance in soils incubated at 10 °C, but 40–50% in soils incubated at 20 °C and 30 °C. The 15N-NER were higher than the 13C-NER and varied between 62% and 74% at 10 °C, between 53% and 81% at 20 °C and 30 °C. A major formation of 13C-bioNER (72–88% of 13C-NER) at 20 °C and 30 °C was noted in soil amended with FYM. An increased formation of 15N-bioNER (14–17% of 15N-NER) was also observed in FYM-amended soil. The xenobiotic 15N-NER had a major share within the 15N-NER and thus need to be considered when assessing the environmental risk of glyphosate-NER. Graphical abstract Unlabelled Image Highlights • Temperature is the main factor controlling mineralization and glyphosate contents. • pH and farmyard manure altered slightly mineralization and glyphosate contents. • Higher TOC content and lower pH promoted non-extractable residue (NER) formation. • Biogenic NER dominated in soil with higher TOC at 20 °C and 30 °C. [ABSTRACT FROM AUTHOR]

Abstract Microbial biodegradation plays a key role in determining the fate of estrogens and can be affected by the background nutrients in natural environments. However, information on how microbial community and nutrient conditions influence estrogen biodegradation is very limited. In this study, 13C-17β-estradiol (13C-E2) was supplied to sediments from the Central Area (CA), Gonghu (GH), Meiliang (ML), and Zhushan (ZS) Bays of Taihu Lake to investigate shifts in bacterial community structure associated with 13C-E2 mineralization over a 30-day incubation period, and the relationships between the background nutrients and cumulative 13C-E2 mineralization rates. The cumulative 13C-E2 mineralization rate for ZS Bay was 87.40% on Day 30, which was significantly greater (P < 0.05) than the rates for ML Bay (67.74%), GH Bay (62.79%), and the CA (52.60%). A correlation analysis suggested that the cumulative 13C-E2 mineralization rate was significantly and positively related to the concentrations of total organic carbon (P < 0.01), nitrate-nitrogen (P < 0.05), ammonia-nitrogen (P < 0.001), and dissolved phosphorus (P < 0.001) in the sediments. Although the highest relative abundances of Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes (contain most estrogen-degrading bacteria) were not initially in the ZS Bay sediment, the addition of 13C-E2 stimulated their growth in all sediments, with the greatest increases observed for ZS Bay. At the genus level, the cumulative increases of seven genera (Nitrosomonas , Bacillus , Pseudomonas , Sphingomonas , Novosphingobium , Alcaligenes and Mycobacterium) considered to be associated with E2 degradation were also highest for ZS Bay (80.2 times), followed by ML Bay (39.8 times), GH Bay (28.1 times), and CA (19.0 times). Besides the higher nutrient concentrations, the responses of bacteria to 13C-E2 addition in ZS Bay could also explain it having the highest cumulative 13C-E2 mineralization rate. These results indicate both the background nutrients and bacterial community evolution in the sediments determined the 13C-E2 mineralization rates. Graphical abstract Unlabelled Image Highlights • 13C-E2 mineralization rate varied significantly among the four sediments. • 13C-E2 mineralization rate was positively related to nutrient concentrations. • The addition of 13C-E2 exerted a selective pressure on certain bacterial groups. • Bacterial community evolution was responsible for the E2 mineralization. [ABSTRACT FROM AUTHOR]

Abstract Modern agricultural practices largely rely on pesticides to protect crops against various pests and to ensure high yields. Following their application to crops a large amount of pesticides ends up in soil where they may affect non-target organisms, among which microorganisms. We assessed the effects of the carbamate nematicide oxamyl on the whole bacterial diversity of an agricultural soil exhibiting enhanced biodegradation of oxamyl through 16S rRNA amplicon next generation sequencing (NGS) and on the oxamyl-degrading bacterial community through cehA q-PCR analysis and 14C-oxamyl mineralization assays. Oxamyl was rapidly mineralized by the indigenous microorganisms reaching >70% within a month. Concomitantly, a significant increase in the number of oxamyl-degrading microorganisms was observed. NGS analysis of the total (DNA) and active (RNA) bacterial community showed no changes in α-diversity indices in response to oxamyl exposure. Analysis of the β-diversity revealed significant changes in the composition of the soil bacterial community after 13 and 30 days of oxamyl exposure only when the active fraction of the bacterial community was considered. These changes were associated with seven OTUs related to Proteobacteria (5), Acidobacteria (1) and Actinobacteria (1). The relative abundance of the dominant bacterial phyla were not affected by oxamyl, except of Bacteroidetes and Gemmatimonadetes which decreased after 13 and 30 days of oxamyl exposure respectively. To conclude, oxamyl induced changes in the abundance of oxamyl-degrading microorganisms and on the diversity of the soil bacterial community. The latter became evident only upon RNA-based NGS analysis emphasizing the utility of such approaches when the effects of pesticides on the soil microbial community are explored. Graphical abstract Unlabelled Image Highlights • Oxamyl effects on the bacterial community of an adapted soil were measured. • Increase in the abundance of oxamyl-degraders concomitant to oxamyl mineralization. • No effect of oxamyl on α- and β-diversity of the total soil bacterial community. • Oxamyl caused transient changes in the β-diversity of active bacterial community. • Six OTUs increased and one OTU decreased after oxamyl application to soil. [ABSTRACT FROM AUTHOR]

Abstract Coastal marine habitats become contaminated with the munitions constituent, Hexahydro-1,3,5-trinitro-1,3,5-trazine (RDX), via military training, weapon testing and leakage of unexploded ordnance. This study used 15N labeled RDX in simulated aquarium-scale coastal marine habitat containing seawater, sediment, and biota to track removal pathways from surface water including sorption onto particulates, degradation to nitroso-triazines and mineralization to dissolved inorganic nitrogen (DIN). The two aquaria received continuous RDX inputs to maintain a steady state concentration (0.4 mg L−1) over 21 days. Time series RDX and nitroso-triazine concentrations in dissolved (surface and porewater) and sorbed phases (sediment and suspended particulates) were analyzed. Distributions of DIN species (ammonium, nitrate + nitrite and dissolved N 2) in sediments and overlying water were also measured along with geochemical variables in the aquaria. Partitioning of RDX and RDX-derived breakdown products onto surface sediment represented 13% of the total added 15N as RDX (15N-[RDX]) equivalents after 21 days. Measured nitroso-triazines in the aquaria accounted for 6–13% of total added 15N-[RDX]. 15N-labeled DIN was found both in the oxic surface water and hypoxic porewaters, showing that RDX mineralization accounted for 34% of the 15N-[RDX] added to the aquaria over 21 days. Labeled ammonium (15NH 4 +, found in sediment and overlying water) and nitrate + nitrite (15NO X , found in overlying water only) together represented 10% of the total added 15N-[RDX]. The production of 15N labeled N 2 (15N 2), accounted for the largest individual sink during the transformation of the total added 15N-[RDX] (25%). Hypoxic sediment was the most favorable zone for production of N 2 , most of which diffused through porous sediments into the water column and escaped to the atmosphere. Graphical abstract Unlabelled Image Highlights • RDX transforms to inorganic nitrogen via series of organic derivatives. • Coupled oxic and anoxic degradation help to transform RDX in marine environments. • Major breakdown product of RDX is N 2 that majority escapes to the atmosphere. • The low redox conditions in porewaters were likely important for RDX mineralization. • RDX breakdown products can adsorb onto the sandy sediment in marine settings. [ABSTRACT FROM AUTHOR]

Abstract Western Antarctica (WA) constitutes the area with the highest human presence in the white continent and also the region where the effects of global warming are more evident worldwide. Such human presence represents a potential risk of pollution with both, organic and inorganic contaminants. Global warming also could modify dynamics and transport of the pollutants, increasing summer water runoff, ice melting and iceberg scouring. Under this fast-changing scenario, knowledge about the concentration of contaminants is essential to evaluate the environmental status of this ecologically relevant area. In this work, we performed the first regional-scale monitoring of 9 trace elements (Cr, Co, Ni, Cu, Zn, As, Pb, Cd and Hg), as well as Fe and Mn, in surface sediment from 64 sites comprising six different areas in Maxwell Bay, 25 de Mayo (King George) Island. Target elements were quantified in surface sediment samples (20–30 m depth) obtained during two summer Antarctic expeditions: 2010/11 and 2011/12 by inductively coupled plasma linked to a quadrupole mass spectrometer (ICP-MS). Based on the average values observed for the reference areas, baseline values were defined for the studied region. A regional enrichment in Cu (compared with the global mean upper crust) was observed and related to the widespread mineralization of volcanic rocks. The most anthropized area (South Fildes) mainly showed sediment class 3 (moderately polluted) for Pb, Cd and Hg with a number samples revealing some highly contaminated hot spots. Although elemental contamination in some samples close to scientific stations or sites where logistic operations were evidenced, a pollution pattern was not clearly identified. The present work represents the first regional-scale attempt to define the baseline values and the anthropic impacts in this region of the WA and also provides the first data about Hg concentration in surface sediment of the study area. Graphical abstract Unlabelled Image Highlights • Quality of sediments from the region with the greatest human presence in Western Antarctica Peninsula, was evaluated. • The first data of Hg in marine sediments for the study area are reported. • Baseline levels are defined for 9 trace elements, Fe and Mn. • The Igeo/SC tool was used for the first time in many sites of the study area for the evaluation of the sediments quality. • The possible effect of iceberg scouring, ice-rafting- debris and ice calving on the composition of sediments is discussed. [ABSTRACT FROM AUTHOR]

Abstract This study investigates copper ore tailings deposited in Repparfjorden, Norway in the 1970's. Bathymetric show that the tailings deposit still occurs as a series of cone-shapes and has retained its original shape for four decades. Analytical data of 51 chemical elements show that some of the tailings are spreading, affecting fjord surface sediments in the inner part of the fjord. The deposited tailings are clearly enriched on the elements Ba, Bi, Cu, Hf and Zr and depleted of Ca, Li, Nb, Pb, Sc, V and Y. A hard pan horizon occurs at 20 cm sediment depth in large parts of the inner inlet, which seems to have precipitated during the deposition of tailings. New tailings were fabricated from the two local mineralisations and these display varying chemical results from each other but also in respect to the old, deposited tailings. Therefore, caution should be taken when making chemical predictions for a future deposit. Graphical abstract Unlabelled Image Highlights • An old tailings deposit still retains the original shape despite sea currents. • During tailings deposition, a hard pan horizon formed on inlet sediment surface. • New tailings show differing chemistry making future predictions difficult. • Tailings still spread to surroundings due to deposit shape and lack of cover. [ABSTRACT FROM AUTHOR]

Sediments delivered to freshwater and marine environments can make important contributions to the aquatic bioavailable nutrient pool. In the Great Barrier Reef (GBR) catchments, particulate nutrients comprise an important fraction of the end of catchment loads; however, their contribution to the bioavailable nutrient pool is not well understood. This research determined which particulate nutrient parameters are the best indicators of the potential effect of fine sediment (<10 μm) on phytoplankton growth. Surface and subsurface sediments were lab-generated to cover a wide spectrum of particulate nutrient bioavailability from key soil types, land uses and erosion processes (hillslope and gully) in a wet and a dry tropics catchment of the GBR. Phytoplankton bioassays were used to assess freshwater and marine phytoplankton responses to sediments. The best indicators were selected by regressing measurements of phytoplankton growth against nutrient bioavailability parameters measured on the sediments. The selected indicator equations included organic carbon (C) pools for both fresh and marine water, highlighting the role of bacteria in mediating nutrient availability for phytoplankton. The equations also included various fractions of particulate nitrogen (N) (differentiating the adsorbed ammonium-N from the particulate organic N), and the ratios of C to N, which indicate the lability of the organic matter present in the sediment. Dissolved reactive phosphorus was also an important indicator in freshwater. The indicators performed better in assessing bioavailability potential than traditional methods to monitor particulate nutrients, e.g., particulate N and particulate phosphorus. Phytoplankton bioassays indicated that nutrients in sediment can promote phytoplankton growth, with nutrient bioavailability depending not only on sediment load, but also sediment characteristics associated with its parent soil. These characteristics vary with soil type, land use and erosion process. Findings will help prioritize erosion control to catchment areas which are most likely to contribute large amounts of bioavailable particulate nutrients to the GBR. [ABSTRACT FROM AUTHOR]

Electro-oxidation with electrogenerated H 2 O 2 (EO-H 2 O 2 ) was applied to treat acidic aqueous solutions of 4-aminoantipyrine (4-AA), a persistent drug metabolite of dipyrone, in sulfate medium. Trials were made using a boron-doped diamond anode in the presence of H 2 O 2 electrogenerated on site. A 2 4 central composite design (CCD) was employed to evaluate the effect of four independent variables, namely current density ( j ), pH, 4-AA concentration and electrolysis time, on the percentages of degradation and mineralization, as well as on mineralization current efficiency (MCE). Predicted responses agreed with observed values, showing linear trendlines with good R 2 and R 2 adj values. The degradation was optimum at j = 77.5 mA cm −2 , pH 3.5 and 62.5 mg L −1 4-AA, leading to 63% and 99% removal after 3 and 7 min, respectively. For those solutions, the largest mineralization was found at j = 77.5 mA cm −2 , attaining 45% abatement at 175 min. Low MCE values were obtained in all electrolyses. An initial route for 4-AA degradation is proposed based on one dimer and eleven aromatic and aliphatic intermediates detected in the treated solutions at pH 3.5 by LC-MS. The initial 62.5 mg L −1 solution at pH 3.5 presented acute toxicity on Artemia salina larvae, with LC 50 = 13.6 mg L −1 , being substantially reduced after 3 and 7 min of EO-H 2 O 2 at j = 77.5 mA cm −2 due to the formation of less toxic derivatives. [ABSTRACT FROM AUTHOR]

Natural dissolved organic matter (DOM) and nitrification can play an important role in biodegradation of pharmaceutically active compounds (PhACs) in aerobic zones of constructed wetlands (CWs). This study used an enrichment culture originating from CW sediment to study the effect of DOM and nitrification on aerobic biodegradation of seven PhACs. The enriched culture degraded caffeine (CAF), metoprolol (MET), naproxen (NAP), and ibuprofen (IBP) with a consistent biodegradability order of CAF > MET > NAP > IBP. Biodegradation of propranolol, carbamazepine, and diclofenac was insignificant (<15%). CAF biodegradation was inhibited by the easily biodegradable DOM. Conversely, DOM enhanced biodegradation of MET, NAP, and IBP, potentially by contributing more biomass capable of degrading PhACs. Nitrification enhanced biodegradation of NAP and IBP and mineralization of the PhAC mixture as well as less biodegradable DOM, which may result from co-metabolism of ammonia oxidizing bacteria or enhanced heterotrophic microbial activity under nitrification. MET biodegradation was inhibited in the presence of nitrification. DOM and nitrification effects on PhAC biodegradation in CWs gained from this study can be used in strategies to improve CW operation, namely: designing hydraulic retention times based on the biodegradability order of specific PhACs; applying DOM amendment; and introducing consistent ammonium streams to increase removal of PhACs of interest. [ABSTRACT FROM AUTHOR]

Produced or flowback waters from Marcellus Shale gas extraction (MSWs) typically are highly saline and contain chemicals including trace metals, which pose significant concerns on water quality. The natural attenuation of MSW chemicals in groundwater is poorly understood due to the complex interactions between aquifer minerals and MSWs, limiting our capabilities to monitor and predict. Here we combine flow-through experiments and process-based reactive transport modeling to understand mechanisms and quantify the retention of MSW chemicals in a quartz (Qtz) column, a calcite-rich (Cal) column, and a clay-rich (Vrm, vermiculite) column. These columns were used to represent sand, carbonate, and clay-rich aquifers. Results show that the types and extent of water-rock interactions differ significantly across columns. Although it is generally known that clay-rich media retard chemicals and that quartz media minimize water-rock interactions, results here have revealed insights that differ from previous thoughts. We found that the reaction mechanisms are much more complex than merely sorption and mineral precipitation. In clay rich media, trace metals participate in both ion exchange and mineral precipitation. In fact, the majority of metals (~50–90%) is retained in the solid via mineral precipitation, which is surprising because we typically expect the dominance of sorption in clay-rich aquifers. In the Cal column, trace metals are retained not only through precipitation but also solid solution partitioning, leading to a total of 75–99% retention. Even in the Qtz column, trace metals are retained at unexpectedly high percentages (~20–70%) due to precipitation. The reactive transport model developed here quantitatively differentiates the relative importance of individual processes, and bridges a limited number of experiments to a wide range of natural conditions. This is particularly useful where relatively limited knowledge and data prevent the prediction of complex rock-contaminant interactions and natural attenuation. [ABSTRACT FROM AUTHOR]

Fungi are known to be present in the activated sludge of wastewater treatment plants (WWTP). Their study should be at the base of an overall vision of the plant effectiveness and of effluents sanitary impact. Moreover, it could be fundamental for the implementation of successful bioaugmentation strategies aimed at the removal of recalcitrant or toxic compounds. This is one of the first studies on the cultivable autochthonous mycoflora present in the mixed liquors of two WWTP treating either vegetable or chromium tannery effluents. All samples showed a risk associated with potential pathogens or toxigenic species and high ecotoxicity ( Lepidium sativum and Raphidocelis subcapitata were the most sensitive organisms). Diverse fungal populations developed, depending on the origin of the samples (63% of the 102 identified taxa were sample-specific). The use of a fungistatic was determinant for the isolation and, thus, for the identification of sample-specific species with a lower growth rate. The incubation temperature also affected the mycoflora composition, even though at lower extent. A selective medium, consisting of agarised wastewater, allowed isolating fungi with a biodegradation potential. Pseudallescheria boydii / Scedosporium apiospermum species complex was ubiquitously dominant, indicating a possible role in the degradation of pollutants in both WWTP. Other species, i.e. Trichoderma spp ., Trematosphaeria grisea , Geotrichum candidum , Lichtheimia corymbifera , Acremonium furcatum , Penicillium simplicissimum , Penicillium dangeardii , Fusarium solani , Scopulariopsis brevicaulis potentially could be involved in the degradation of specific pollutants of vegetable or chromium tannery wastewaters. However, several of these fungi are potential pathogens and their application, for an in situ treatment, must be carefully evaluated. [ABSTRACT FROM AUTHOR]

Mercury (Hg) concentrations in water and biota are often positively correlated to organic matter (OM), typically measured as total or dissolved organic carbon (TOC/DOC). However, recent evidence suggests that higher OM concentrations inhibit bioaccumulation of Hg. Here, we test how TOC impacts the Hg accumulation in fish in a synoptic study of Methyl-Hg (MeHg) in water and total Hg (THg) in perch ( Perca fluviatilis ) in 34 boreal lakes in southern Norway. We found that aqueous MeHg (r 2  = 0.49, p  < 0.0001) and THg (r 2  = 0.69, p  < 0.0001), and fish THg (r 2  = 0.26, p  < 0.01) were all positively related with TOC. However, we found declining MeHg bioaccumulation factors (BAF MeHg ) for fish with increasing TOC concentrations. The significant correlation between fish THg concentrations and aqueous TOC suggests that elevated fish Hg levels in boreal regions are associated with humic lakes. The declining BAF MeHg with increasing TOC suggest that increased OM promotes increased aqueous Hg concentrations, but lowers relative MeHg bioaccumulation. A mechanistic understanding of the response from OM on BAF MeHg might be found in the metal-complexation properties of OM, where OM complexation of metals reduces their bioavailability. Hence, suggesting that MeHg bioaccumulation becomes less effective at higher TOC, which is particularly relevant when assessing potential responses of fish Hg to predicted future changes in OM inputs to boreal ecosystems. Increased browning of waters may affect fish Hg in opposite directions: an increase of food web exposure to aqueous Hg, and reduced bioavailability of Hg species. However, the negative relationship between BAF MeHg and TOC is challenging to interpret, and carries a great deal of uncertainty, since this relationship may be driven by the underlying correlation between TOC and MeHg (i.e. spurious correlations). Our results suggest that the trade-off between Hg exposure and accumulation will have important implications for the effects of lake browning on Hg transport, bioavailability, and trophodynamics. [ABSTRACT FROM AUTHOR]

We investigated how two different biochars (wood biochar - WBC and straw biochar - SBC) affected P dynamics and bioavailability in five different soils differing in pH, C%, texture, Fe, Al, Ca, and Mg giving a range of soils with low (S1 and S2), intermediate (S4), and high (S3 and S5) P sorption capacities. Langmuir and Freundlich equations were fitted to the sorption data of soil and soil/biochar mixtures. P fertilizer applied to all treatments was fractioned into strongly sorbed P (qS), easily available sorbed P (qA) and solution P (c) by determining the anion exchange resin (AER)-extractable P in samples from the sorption experiment. A pot experiment was conducted to measure P uptake by maize grown in S1, S2 and S3 amended with WBC or SBC at two P fertilizer levels (0 or 70 mg P kg −1 ). Only WBC could sorb P from solution partly due to a high content of calcite. SBC did not have any effect on P sorption isotherms, whereas WBC increased the P sorption in S1, S2, and S4, yet decreased P sorption in acidic soil S5. qS increased in S1, S2, and S4, and decreased in S5 in WBC treatments, whereas, qS decreased in SBC treatments in soils S2, S4, and S5. Accordingly, there was a significant interaction between soil type and biochar on maize growth and P uptake. Biochar had no effect in an alkaline soil (S3), whereas, WBC and SBC had positive effects on maize growth in slightly acidic soils S1 and S2, depending on the soil P status, however, the P uptake was lower in WBC compared to SBC treatments. Biochar and soil properties and the P status of the soil affect P bioavailability. The study provides useful information for optimizing the use of biochar in agricultural P management. [ABSTRACT FROM AUTHOR]

Simple, rapid and reliable methods of assessing soil burn severity (SBS) are required in order to prioritize post-fire emergency stabilization actions. SBS proxies based on visual identification and changes in soil organic matter (SOM) content and quality can be related to other soil properties in order to determine the extent to which soil is perturbed following fire. This task is addressed in the present study by an approach involving the use of differential scanning calorimetry-thermogravimetric analysis (DSC-TGA) to determine changes in SOM generated in soils subjected to different levels of SBS. Intact topsoil monoliths comprising the organic horizons and the surface mineral soil (alumic-humic umbrisols) were collected from a representative P. pinaster stand in NW Spain. The monoliths were experimentally burned in a combustion wind tunnel to simulate different fire conditions (fuel bed comprising forest pine litter and wood; air flow, 0.6 m s −1 ). Changes in OM properties in the soil organic layer and mineral soils samples (0–2 cm) at the different temperatures and SBS levels were identified. For both duff and mineral soil, the data revealed a temperature-induced increase in aromatic compounds and a concomitant decrease of carbohydrates and alkyl products. However, for a given temperature, the degree of carbonization/aromatization was lower in the mineral soil than in the duff, possibly due to the different composition of the OM and to the different combustion conditions. The low degree of aromatization of the organic matter suggests that this soil component could undergo subsequent biological degradation. SOM content and thermal recalcitrance (measured as T50) discriminated the SBS levels. Use of visual identification of SBS levels in combination with DSC-TGA enables rapid evaluation of the spatial variability of the effects of fire on SOM properties. This information is useful to predict soil degradation process and implement emergency soil stabilization techniques. [ABSTRACT FROM AUTHOR]

The construction and use of buildings represent about half of the extracted materials and energy consumption, and around one third of the water consumption and waste produced in the European Union. Therefore it is becoming more important to use sustainable materials that reduce the environmental impacts of construction, by conserving and using resources more efficiently. Green walls can be used as a sustainable strategy to reduce the environmental impact of buildings. The aim of this study is to evaluate the environmental impact of a new modular system for green roofs and green walls (Geogreen) which uses waste and sustainable materials in its composition. A life cycle analysis (LCA) is used to evaluate the long term environmental benefits of this system. The life cycle analysis (LCA) is carried according to ISO 14040/44 using GaBi software and CML 2001 impact category indicators. The adopted functional unit is the square meter of each material required to assemble the Geogreen system. This study also compares the environmental performance of the Geogreen system with other living wall systems and other cladding materials using data from the literature. This LCA study of the Geogreen system became relevant to identify a curing process with a major impact on GWP due to the energy consumed in this process. A change on this process allowed reducing 74% of the overall GWP. After this change it can be noticed that the Geogreen System presents one of the lowest environmental burden when compared to other construction systems. [ABSTRACT FROM AUTHOR]

Glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) have frequently been detected in surface water and groundwaters. Since adequate glyphosate mineralization in soil may reduce its losses to environment, improved understanding of site specific factors underlying pesticide mineralization in soils is needed. The aim of this study was to investigate the relationship between soil properties and glyphosate mineralization. To establish a sound basis for resilient correlations, the study was conducted with a large number of 21 agricultural soils, differing in a variety of soil parameters, such as soil texture, soil organic matter content, pH, exchangeable ions etc. The mineralization experiments were carried out with 14 C labelled glyphosate at a soil water tension of −15 kPa and at a soil density of 1.3 g cm −3 at 20 ± 1 °C for an incubation period of 32 days. The results showed that the mineralization of glyphosate in different agricultural soils varied to a great extent, from 7 to 70% of the amount initially applied. Glyphosate mineralization started immediately after application, the highest mineralization rates were observed within the first 4 days in most of the 21 soils. Multiple regression analysis revealed exchangeable acidity (H + and Al 3+ ), exchangeable Ca 2+ ions and ammonium lactate extractable K to be the key soil parameters governing glyphosate mineralization in the examined soils. A highly significant negative correlation between mineralized glyphosate and NaOH-extractable residues (NaOH-ER) in soils strongly suggests that NaOH-ER could be used as a simple and reliable parameter for evaluating the glyphosate mineralization capacity. The NaOH-ER were composed of glyphosate, unknown 14 C-residues, and AMPA (12%–65%, 3%–34%, 0%–11% of applied 14 C, respectively). Our results highlighted the influential role of soil exchangeable acidity, which should therefore be considered in pesticide risk assessments and management to limit efficiently the environmental transfers of glyphosate. [ABSTRACT FROM AUTHOR]

Thermal destruction of chemical munitions from World War I led to the formation of a heavily contaminated residue that contains an unexpected mineral association in which a microbial As transformation has been observed. A mesocosm study was conducted to assess the impact of water saturation episodes and input of bioavailable organic matter (OM) on pollutant behavior in relation to biogeochemical parameters. Over a period of about eight (8) months, the contaminated soil was subjected to cycles of dry and wet periods corresponding to water table level variations. After the first four (4) months, fragmented litter from the nearby forest was placed on top of the soil. The mesocosm solid phase was sampled by three rounds of coring: at the beginning of the experiment, after four (4) months (before the addition of OM), and at the end of the experiment. Scanning electron microscopy coupled to energy dispersive X-ray spectroscopy observations showed that an amorphous phase, which was the primary carrier of As, Zn, and Cu, was unstable under water-saturated conditions and released a portion of the contaminants in solution. Precipitation of a lead arsenate chloride mineral, mimetite, in soils within the water saturated level caused the immobilization of As and Pb. Mimetite is a durable trap because of its large stability domain; however, this precipitation was limited by a low Pb concentration inducing that high amounts of As remained in solution. The addition of forest litter modified the quantities and qualities of soil OM. Microbial As transformation was affected by the addition of OM, which increased the concentration of both As(III)-oxidizing and As(V)-reducing microorganisms. The addition of OM negatively impacted the As(III) oxidizing rate, however As(III) oxidation was still the dominant reaction in accordance with the formation of arsenate-bearing minerals. [ABSTRACT FROM AUTHOR]

Understanding interrelations between an environment's hydrological past and its current biogeochemistry is necessary for the assessment of biogeochemical and microbial responses to changing hydrological conditions. The question how previous dry-wet events determine the contemporary microbial and biogeochemical state is addressed in this study. Therefore, sediments exposed to the atmosphere of areas with a different hydrological past within one kettle hole, i.e. (1) the predominantly inundated pond center, (2) the pond margin frequently desiccated for longer periods and (3) an intermediate zone, were incubated with the same rewetting treatment. Physicochemical and textural characteristics were related to structural microbial parameters regarding carbon and nitrogen turnover, i.e. abundance of bacteria and fungi, denitrifiers (targeted by the nirK und nirS functional genes) and nitrate ammonifiers (targeted by the nrfA functional gene). Our study reveals that, in combination with varying sediment texture, the hydrological history creates distinct microbial habitats with defined boundary conditions within the kettle hole, mainly driven by redox conditions, pH and organic matter (OM) composition. OM mineralization, as indicated by CO 2 -outgassing, was most efficient in exposed sediments with a less stable hydrological past. The potential for nitrogen retention via nitrate ammonification was highest in the hydrologically rather stable pond center, counteracting nitrogen loss due to denitrification. Therefore, the degree of hydrological stability is an important factor leaving a microbial and biogeochemical legacy, which determines carbon and nitrogen losses from small lentic freshwater systems in the long term run. [ABSTRACT FROM AUTHOR]

The Gulf of Tadjoura is located in the Horn of Africa and is widely recognized as an important site where the zooplanktivorous whale sharks seasonally aggregate from October to February. The surface zooplankton community (0–3 m) was weekly sampled from November 2016 to February 2017 in two sites during the whale shark aggregation period. A total of 12 phyla were identified. Copepoda represented the most abundant and diverse group with 29 different genera, and contributed with an average of 82% of the mean zooplankton density of approximately 6600 ind m −3 . During the sampling period, copepods were dominated numerically by Calanoida (3600 ind m −3 ), followed by Poicilostomatatoida (1300 ind m −3 ). Within the copepods, Paracalanidae, Calanidae, Oncaeidae and Miraciidae were the most common families. The temporal trend in zooplankton biomass at both stations revealed the highest peak in December (41.3 ± 36.4 mg m −3 ), and the lowest in February (6.6 ± 3.3 mg m −3 ). As no information is available on the occurrence of legacy contaminants use and release in this area, analysis revealed the consistent presence of both DDT and PCB residues in zooplankton samples in the Gulf of Tadjoura. Total PCB ranged from approximately 110 to 637 ng g −1 d.w., while total DDT from 21 to 80 ng g −1 d.w. The proportion of primary DDT in the total residue was higher than DDE and DDD, which strongly suggests that the area might actually be subjected to DDT inputs of the parent compound. [ABSTRACT FROM AUTHOR]

In recent years, the Chinese government has strengthened its efforts in surface water protection and restoration through strict policies and heavy investments. A clear understanding of the impacts of land use on water quality is necessary in order to ensure an effective and efficient implementation of the ongoing surface water restoration program in China. To this end, four small watersheds (less than 5000 ha) in southeastern China, which have clear gradients in the intensities of agriculture (17.0–45.4%), forest (35.2–73.6%) and built-up area (3.3–8.5%), were investigated regarding the impacts of land use on water quality. In addition to the general water quality indices, characteristic components derived by fluorescence excitation-emission matrices (FEEMs) coupled with parallel factor analysis (PARAFAC) were employed to explore a more accurate association between land use and water quality. The results show that agricultural intensity has significant effects by elevating the concentrations of dissolved organic carbon (DOC, an approximate six-fold increase) and total phosphorous (TP, an approximate four-fold increase) in the surface waters. A total of five PARAFAC components representing terrestrial (three components) and protein-like (two components) substances were identified. The PARAFAC results indicate that land-use patterns affected the dissolved organic matter (DOM) in the aspects of both amount and composition. The intensity (R.U.) of the terrestrial components showed a strong correlation (r 2  = 0.95, p  = 0.01) with agricultural land percentage. Moreover, although the proportion of built-up area varies with a relatively small range, a protein-like component could predict its impact with excellent sensitivity (r 2  = 0.94, p  = 0.02), whereas the general water quality indices were incapable of predicting the impact due to their multiple sources. The results of this study demonstrate that the FEEMs-PARAFAC technique provides an inexpensive and effective tool for policy makers to overcome the insensitivity of general water quality indices, particularly for the restoration of watersheds with complex land-use patterns. [ABSTRACT FROM AUTHOR]

A MIKE SHE hydrological-solute transport model including nitrate reduction is employed to evaluate the delayed response in nitrogen loads in catchment streams following the implementation of nitrogen mitigation measures since the 1980s. The nitrate transport lag times between the root zone and the streams for the period 1950–2011 were simulated for two catchments in Denmark and compared with observational data. Results include nitrogen concentration and mass discharge to streams. By automated baseflow separation, stream discharge was separated into baseflow and drain flow components, and the nitrogen concentration and mass discharge in baseflow and drain flow were determined. This provided insight on the development of stream nitrogen loads, with a short average lag time in drain flow and a long average lag time in baseflow. The long term effect of nitrogen mitigation measures was determined, with results showing that there is a 15 years long delay in the appearance of peak nitrogen loads in streams. This means that real time stream monitoring data cannot be used alone to assess the effect of nitrogen mitigation measures. [ABSTRACT FROM AUTHOR]

This study analyzes the influence of various fertilizer management practices on crop yield and soil organic carbon (SOC) based on the long-term field observations and modelling. Data covering 11 years from 8 long-term field trials were included, representing a range of typical soil, climate, and agro-ecosystems in China. The process-based model EPIC (Environmental Policy Integrated Climate model) was used to simulate the response of crop yield and SOC to various fertilization regimes. The results showed that the yield and SOC under additional manure application treatment were the highest while the yield under control treatment was the lowest (30%–50% of NPK yield) at all sites. The SOC in northern sites appeared more dynamic than that in southern sites. The variance partitioning analysis (VPA) showed more variance of crop yield could be explained by the fertilization factor (42%), including synthetic nitrogen (N), phosphorus (P), potassium (K) fertilizers, and fertilizer NPK combined with manure. The interactive influence of soil (total N, P, K, and available N, P, K) and climate factors (mean annual temperature and precipitation) determine the largest part of the SOC variance (32%). EPIC performs well in simulating both the dynamics of crop yield ( NRMSE  = 32% and 31% for yield calibration and validation) and SOC ( NRMSE  = 13% and 19% for SOC calibration and validation) under diverse fertilization practices in China. EPIC can assist in predicting the impacts of different fertilization regimes on crop growth and soil carbon dynamics, and contribute to the optimization of fertilizer management for different areas in China. [ABSTRACT FROM AUTHOR]

Tundra soils account for 50% of global stocks of soil organic carbon (SOC), and it is expected that the amplified climate warming in high latitude could cause loss of this SOC through decomposition. Decomposed SOC could become hydrologically accessible, which increase downstream dissolved organic carbon (DOC) export and subsequent carbon release to the atmosphere, constituting a positive feedback to climate warming. However, DOC export is often neglected in ecosystem models. In this paper, we incorporate processes related to DOC production, mineralization, diffusion, sorption-desorption, and leaching into a customized arctic version of the dynamic ecosystem model LPJ-GUESS in order to mechanistically model catchment DOC export, and to link this flux to other ecosystem processes. The extended LPJ-GUESS is compared to observed DOC export at Stordalen catchment in northern Sweden. Vegetation communities include flood-tolerant graminoids ( Eriophorum ) and Sphagnum moss, birch forest and dwarf shrub communities. The processes, sorption-desorption and microbial decomposition (DOC production and mineralization) are found to contribute most to the variance in DOC export based on a detailed variance-based Sobol sensitivity analysis (SA) at grid cell-level. Catchment-level SA shows that the highest mean DOC exports come from the Eriophorum peatland (fen). A comparison with observations shows that the model captures the seasonality of DOC fluxes. Two catchment simulations, one without water lateral routing and one without peatland processes, were compared with the catchment simulations with all processes. The comparison showed that the current implementation of catchment lateral flow and peatland processes in LPJ-GUESS are essential to capture catchment-level DOC dynamics and indicate the model is at an appropriate level of complexity to represent the main mechanism of DOC dynamics in soils. The extended model provides a new tool to investigate potential interactions among climate change, vegetation dynamics, soil hydrology and DOC dynamics at both stand-alone to catchment scales. [ABSTRACT FROM AUTHOR]

The design of French VFCWs leads to the formation of a sludge layer at the surface of the first filters due to the retention of suspended solids from the percolation of unsettled wastewater. This layer plays a major role in the system but still little is known on its characteristics and evolutions. In this study, suspended solids and sludge deposits sampled from two French VFCW plants were analyzed by different methods in the objective to assess the evolution of particulate organic matter (POM) along the treatment chain and within the sludge layer, and identify relevant analytical indicators of these phenomena. The treatment chain included an aerobic trickling filter followed by FeCl 3 injection and two successive stages of filters. Thermal analyses showed that OM contents of suspended solids decreased along the treatment chain. POM in inflow suspended solids was predominantly composed of reactive, biodegradable compounds which were partly hydrolyzed and mineralized notably at the trickling filter stage. 3D fluorescence spectra collected from aqueous POM extracts confirmed the evolution of organic matter from low-molecular reactive compounds to more complex and stable structures such as humic-like substances. FTIR confirmed the mineralization of POM's reactive constituents along the treatment chain by the decrease in the intensities of the characteristics bands of aliphatic compounds or proteins, and its humification in the sludge deposits through the relative increase of the bands at 1634 cm − 1 (v C = O ) and 1238 cm − 1 (δ C = O and/or δ OH ). Isotopic ratios δ 2 H/ 1 H and δ 15 N/ 14 N were found to be good indicators of POM evolutions. The higher values of δ 2 H/ 1 H and δ 15 N/ 14 N ratios measured in sludge deposits as compared to inflow suspended solids were related to POM humification and to microbial processes of POM hydrolysis and mineralization, respectively. [ABSTRACT FROM AUTHOR]

One of the most critical challenges faced in restoration of disturbed arid lands is the limited availability of topsoil. In post-mining restoration, alternative soil substrates such as mine waste could be an adequate growth media to alleviate the topsoil deficit, but these materials often lack appropriate soil characteristics to support the development and survival of seedlings. Thus, addition of exogenous organic matter may be essential to enhance plant survival and soil function. Here, we present a case study in the arid Pilbara region (north-west Western Australia), a resource-rich area subject to intensive mining activities. The main objective of our study was to assess the effects of different restoration techniques such as soil reconstruction by blending available soil materials, sowing different compositions of plant species, and addition of a locally abundant native soil organic amendment ( Triodia pungens biomass) on: (i) seedling recruitment and growth of Triodia wiseana , a dominant grass in Australian arid ecosystems, and (ii) soil chemical, physical, and biological characteristics of reconstructed soils, including microbial activity, total organic C, total N, and C and N mineralisation. The study was conducted in a 12-month multifactorial microcosms setting in a controlled environment. Our results showed that the amendment increased C and N contents of re-made soils, but these values were still lower than those obtained in the topsoil. High microbial activity and C mineralisation rates were found in the amended waste that contrasted the low N mineralisation but this did not translate into improved emergence or survival of T. wiseana . These results suggest a short- or medium-term soil N immobilisation caused by negative priming effect of fresh un-composted amendment on microbial communities. We found similar growth and survival rates of T. wiseana in topsoil and a blend of topsoil and waste (50:50) which highlights the importance of topsoil, even in a reduced amount, for plant establishment in arid land restoration. [ABSTRACT FROM AUTHOR]

Anthropogenic perturbation of the global nitrogen cycle and its effects on the environment such as hypoxia in coastal regions and increased N 2 O emissions is of increasing, multi-disciplinary, worldwide concern, and agricultural production is a major contributor. Only limited studies, however, have simultaneously investigated NO 3 − losses to subsurface drain flow and N 2 O emissions under corn-soybean production. We used the Root Zone Water Quality Model (RZWQM) to evaluate NO 3 − losses to drain flow and N 2 O emissions in a corn-soybean system with a winter rye cover crop (CC) in central Iowa over a nine year period. The observed and simulated average drain flow N concentration reductions from CC were 60% and 54% compared to the no cover crop system (NCC). Average annual April through October cumulative observed and simulated N 2 O emissions (2004–2010) were 6.7 and 6.0 kg N 2 O-N ha − 1 yr − 1 for NCC, and 6.2 and 7.2 kg N ha − 1 for CC. In contrast to previous research, monthly N 2 O emissions were generally greatest when N loss to leaching were greatest, mostly because relatively high rainfall occurred during the months fertilizer was applied. N 2 O emission factors of 0.032 and 0.041 were estimated for NCC and CC using the tested model, which are similar to field results in the region. A local sensitivity analysis suggests that lower soil field capacity affects RZWQM simulations, which includes increased drain flow nitrate concentrations, increased N mineralization, and reduced soil water content. The results suggest that 1) RZWQM is a promising tool to estimate N 2 O emissions from subsurface drained corn-soybean rotations and to estimate the relative effects of a winter rye cover crop over a nine year period on nitrate loss to drain flow and 2) soil field capacity is an important parameter to model N mineralization and N loss to drain flow. [ABSTRACT FROM AUTHOR]

Insecticide indoxacarb metabolites JT333 and MP819 were used as model compounds to assess the utilization of kinetic modeling to elucidate metabolic pathways, determine degradation kinetics of non-extractable residues (NER) and predict the accumulation potential of the released NER in soil. Soil adsorption coefficients and degradation product formation were determined in different soils in laboratory. Inverse kinetic modeling was applied to explore the dynamics of dissipation of parent (P), formation of extractable metabolites (MET), NER and CO 2 , and to identify their routes of degradation in soil. These two compounds share similar structural characteristics, have high affinity to soil (K oc > 5000 L/kg), short half-life (DT 50 of 4–9 days), and significant CO 2 formation in soil. However, kinetic modeling showed that they degraded via different pathways. The P-MET-CO 2 conversion route was the major degradation pathway for JT333 in aerobic soil. Multiple pathways were involved in MP819 degradation, while the formation of NER was predominant. The time-exposure area under the curves (AUC) for the MET or NER in soils were derived from the time-%concentration plots for the evaluation of rate limiting steps in their degradation pathways. In P-MET-CO 2 pathway the MET-CO 2 conversion is the rate limiting step for both compounds. Higher P-MET conversion/MET-CO 2 conversion rate constant ratio resulted in larger MET AUC. The rate of NER degradation appeared much slower compared to the rates of P-MET and MET-CO 2 conversions, likely due to the rate-limiting step of NER release from the bound-state, indicating that in this situation the free-state NER would be unlikely to accumulate in soil. The study reported here demonstrates the utility of kinetic modeling to quantify the dynamics of NER formation/dissipation vs. P-MET-CO 2 conversion, and the application of kinetic modeling to predict the possibility of free-sate NER accumulation in soil, therefore, reveals the potential for the quantitative NER environmental risk assessment. [ABSTRACT FROM AUTHOR]

The incorporation of biochar into soil has been proposed as a strategy for enhancing soil fertility and crop productivity. However, there is limited information regarding the responses of soil respiration and the C, N and P cycles to the addition of apple branch biochar at different rates to soil with different levels of N. A 108-day incubation experiment was conducted to investigate the effects of the rate of biochar addition (0, 1, 2 and 4% by mass) on soil respiration and nutrients and the activities of enzymes involved in C, N and P cycling under two levels of N. Our results showed that the application of apple branch biochar at rates of 2% and 4% increased the C-mineralization rate, while biochar amendment at 1% decreased the C-mineralization rate, regardless of the N level. The soil organic C and microbial biomass C and P contents increased as the rate of biochar addition was increased to 2%. The biochar had negative effects on β-glucosidase, N -acetyl-β-glucosaminidase and urease activity in N-poor soil but exerted a positive effect on all of these factors in N-rich soil. Alkaline phosphatase activity increased with an increase in the rate of biochar addition, but the available P contents after all biochar addition treatments were lower than those obtained in the treatments without biochar. Biochar application at rates of 2% and 4% reduced the soil nitrate content, particularly in N-rich soil. Thus, apple branch biochar has the potential to sequester C and improve soil fertility, but the responses of soil C mineralization and nutrient cycling depend on the rate of addition and soil N levels. [ABSTRACT FROM AUTHOR]

A field experiment was established in a high elevation red spruce ( Picea rubens Sarg.) – balsam fir ( Abies balsamea ) forest on Mount Ascutney Vermont, USA in 1988 to test the nitrogen (N) saturation hypothesis, and to better understand the mechanisms causing forest decline at the time. The study established replicate control, low and high dose nitrogen addition plots (i.e., 0, 15.7 and 31.4 kg NH 4 Cl-N ha − 1 yr − 1 ). The treatments began in 1988 and continued annually until 2010, but monitoring has continued to present. During the fertilization period, forest floor C:N, net in situ N mineralization, spruce foliar Ca%, and live spruce basal area decreased with increasing N addition, while foliar spruce N% and forest floor net nitrification increased with increasing N addition. The control plots aggraded forest floor N at a rate equal to the sum of the net in situ N mineralization plus average ambient deposition. Conversely, N addition plots lost forest floor N. Following the termination of N additions in 2010, the measured tree components returned to pre-treatment levels, but forest floor processes were slower to respond. During the 30 year study, site surface air temperature has increased by 0.5 °C per decade, and total N deposition has decreased 5.5 to 4.0 kg N ha − 1 yr − 1 . There have also been three significant drought years and at least one freeze injury year after which much of the forest mortality on the N addition plots occurred. Given that there was no control for the air temperature increase, discussion of the interactive impacts of climate and change and N addition is only subjective. Predicted changes in climate, N deposition and other stressors suggest that even in the absence of N saturation, regeneration of the spruce-fir ecosystem into the next century seems unlikely despite recent region-wide growth increases. [ABSTRACT FROM AUTHOR]

Many countries and some Brazilian regions have defined the guideline values for metals in soils. However, the local geological features may be so heterogeneous that global or even regional guideline values cannot be applied. The Greenstone Belts are worldwide geological formations of vast extension, containing mineralization of various metals (e.g., Au, Cr, Ni, and Ag). Natural concentrations of soils must be known to correctly assess the impact of mining. We studied the soils of the Rio Itapicuru Greenstone Belt (RIGB), of Paleoproterozoic age, sampling at 24 sites (0–0.20 m) in the areas not or minimally human impacted, equally distributed in the three units of the RIGB: Volcanic Mafic Unit (VMU), Volcanic Felsic Unit (VFU), and Volcano-clastic Sedimentary Unit (SU). The natural pseudo-total concentrations of Cr, Ni, Cu, Zn, Pb, Fe, and Mn were obtained by acid digestion (EPA3050b) both in the soil and the particle-size fractions (sand and clay + silt). The concentrations of metals in RIGB soils, especially Cr and Ni, are generally higher than those reported for other regions of Brazil or other countries. Even the sedimentary soils have relatively high metal values, naturally contaminated by the VMU of the RIGB; a potential impact on Mesozoic and Cenozoic sedimentary rocks located near the study region is highly expected. Metals are concentrated (80%) in the fine particle-size fraction, implying an easy availability through surface transport (wind and runoff). We introduced a new index, called the Fe-independent accumulation factor – AF -Fe , which reveals that 90–98% of the dynamics of the trace metals is associated with the iron geochemical cycle. We primarily conclude that determining the guideline values for different soil classes in variable geological/geochemical environment and under semiarid climate is meaningless: the concentration of metals in soils is clearly more related to the source material than to the pedogenesis processes. [ABSTRACT FROM AUTHOR]