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Abstract The Red River Delta is a major agricultural production area of Vietnam with year-round use of pesticides for paddy rice cultivation and other production systems. The delta is protected from flooding, storm surges and saline water intrusion by a sophisticated river and sea-dyke system. Little is known about the effects of such a dyke system on pesticide pollution in the enclosed landscape. Our aim was to address this gap by i) determining pesticide prevalence in soils and sediments within a dyked agricultural area, and by ii) assessing whether and to which degree this dyke system might affect the spatial distribution of pesticides. After sampling paddy rice fields (topsoil) and irrigation ditches (sediment) perpendicular to the dyke in Giao Thuy district, we analysed 12 of the most commonly used pesticides in this area. In soils, we detected most frequently isoprothiolane (100% detection frequency), chlorpyrifos (85%) and propiconazole (41%) while in sediments isoprothiolane (71%) and propiconazole (71%) were most frequently found. Maximum concentrations reached 42.6 μg isoprotiolane kg−1 in soil, and 35.1 μg azoxystrobin kg−1 in sediment. Our results supported the assumption that the dyke system influenced residue distribution of selected pesticides. More polar substances increasingly accumulated in fields closer to the sea-dyke (R2 = 0.92 for chlorpyrifos and 0.51 for isoprothiolane). We can thus support initiatives from local authorities to use the distance to dykes as a mean for deliniating zones of different environmental pollution; yet, the degree at which dykes influence pesticide accumulation appear to be compound specific. Graphical abstract Image 1 Highlights • Twelve commonly used pesticides have been detected in a dyked area. • Soil under paddy rice contain hydrophobic pesticides. • Sediment of irrigation ditches contains frequently the same pesticides as in the soil. • Spatial distribution of pesticides seems to be affected by the dyke-system. This study provides data on prevalence of recently and commonly used pesticides in soil and sediments and investigated possible effects of dyke constructions on spatial pesticide distribution. [ABSTRACT FROM AUTHOR]

• n -Alkanes were found in topsoils and deep sediments of the desert. • n -Alkane biomarker compositions differ between fog and rain-fed regions. • 75–98% of n -alkanes are stored below 15 cm in the subsurface sediments. • Climate change had a higher influence on the desert margins than on the hyperarid desert zone. • Currently hyperarid regions of the Atacama Desert once possibly varied in size. Although the Atacama is the oldest and most continuous dry desert on Earth, organic matter (OM) is ubiquitous in its surface sediments. Today, vegetation growth is restricted to the Coastal Cordillera and the Andean foothills, which are predominantly supplied by fog or rainfall. The sources of OM in topsoils of hyperarid regions and deep sediments remain an open question; therefore, we hypothesized that desert plants exhibit specific n -alkane compositions that can be traced in adjacent topsoils and assessed possible OM sources and formation processes in hyperarid regions and soil depths of desert. We determined the n -alkane signatures of plants (n = 28), of soil OM in their vicinity, of hyperarid surface sediments (n = 82), and of four depth profiles (up to 200 cm). We found that n -alkane distributions in fog-fed plants were dominated in order by n C 31 , n C 29 , n C 33 , and n C 27 alkanes, while rain-fed plants were dominated by n C 29 and n C 31 alkanes. When the ratio of n C 27+ n C 33 / n C 29+ n C 31 was applied as a "fog-to-rain n -alkane ratio", the data in surface soils and sediments below 1200 m a.s.l. (in the west of the desert) indicated fog-influenced formation of organics, while all soils and sediments formed higher than 1200 m a.s.l. (in the center and east of the desert) archived n -alkanes from plants fed by rain. Surprisingly, 75–98% of the desert's OM was found in deep sediments, even under recent vegetation cover. Hence, our findings indicate that currently vegetation-free hyperarid regions of the Atacama Desert once varied in size depending on climate change. [ABSTRACT FROM AUTHOR]

Phosphate rocks (PRs) used in fertilizer production contain uranium (U), which enters agricultural soils through phosphorus fertilization. However, our knowledge is still limited and cannot explain the different levels of U contamination found in agricultural systems. The paper reviewed the spatial and temporal U variations in PRs to obtain a comprehensive overview of U levels in various PRs worldwide and to investigate why U concentrations in igneous PRs are significantly lower compared to sedimentary PRs, and why less U is present in old sedimentary PRs (Precambrian-Cambrian) than in younger PRs (Ordovician-Neogene). In addition, the natural oxygen isotope compositions of phosphate (δ18O p) in various PRs were determined to identify their origins in relation to their U concentration. The δ18O p values differed among igneous PRs, old sedimentary PRs, and younger sedimentary PRs. Generally, the PRs with low δ18O p values had low U concentrations. In igneous PRs, low U concentrations were due to the lack of secondary U enrichment processes after rock formation, with low δ18O p values resulting from limited isotope fractionation at high temperature. Conversely, in sedimentary PRs, both U concentrations and δ18O p values were influenced by paleoclimate and paleogeographic features. Overall, there is a time-dependent coincidence of processes altering U concentration and δ18O p signatures of sedimentary PRs in a similar direction. • The U contents of phosphate rocks (PRs) increase in the order: igneous PRs, old sedimentary PRs (Precambrian-Cambrian), younger sedimentary PRs (Ordovician-Neogene). • The values of δ18O p of PRs increase as follows: igneous PRs, old sedimentary PRs (Precambrian-Cambrian), younger sedimentary PRs (Ordovician-Neogene). • In sedimentary PRs, there is a time-dependent coincidence of processes altering U concentration and δ18O p signatures in a similar direction. [ABSTRACT FROM AUTHOR]

Rice straw burning in agroecosystems delivers BC (black carbon) to soil/sediment but its contribution relative to other BC sources is unspecified. We have differentiated for the first time combustion residues (CRs) derived from autochthonous and pyrogenic agricultural vs. allochthonous and biogenic riverine input by way of complementary analysis of BC and PAH (polycyclic aromatic hydrocarbon) abundance and composition. Both CR markers in four upland and six periodically flooded paddy soils having different cultivation times were analyzed. BC was the quantitatively dominant CR fraction at 16–512 mg/g SOC (soil organic carbon), whereas PAHs yielded trace amounts of eleven EPA-PAHs at 1.5–47.0 μg/g SOC. CR concentrations in paddy soils exceeded those in upland topsoil. The lowest BC and PAH concentration occurred in subsoil ⩽ 700 yr old, independent of paddy or upland use, but BC content increased in paddy subsoil ⩾ 700 yr old. Exceptional BC enrichment and composition of benzene polycarboxylic acid (BPCA) products revealed dark buried horizons (700 and 1000 yr sites) as former topsoil. Relative distributions of 5-ring PAHs differentiated CRs from biogenic residues in substrate, topsoil and subsoil. Perylene was enriched in tidal wetland substrate, indicating allochthonous input from soil/sediment erosion in the Yangtze River catchment. An identical pattern was observed in subsoil. Present and former topsoil yielded a distinctive distribution of rice ash PAHs. Although PAHs occurred in traces, their wider compositional variation improved source discrimination power exceeding that of BPCAs. The former are recommended for source identification and the latter for quantifying CR input to soil/sediment. Parallel application of both methodological approaches is advocated for investigating combustion processes in ecosystems. [ABSTRACT FROM AUTHOR]

Land application of animal wastes from intensive grassland farming has resulted in growing environmental problems relating to greenhouse gas emissions, ammonia volatilisation, and nitrate and phosphorus leaching into surface and groundwater. We examined the short-term effects of dairy slurry amendment on carbon sequestration and enzyme activities in a temperate grassland (Southwest England). Slurry was collected from cows fed either on perennial ryegrass (C3) or maize (C4) silages. Fifty m3 ha−1 of each of the obtained C3 or C4 slurries (δ13C=−30.7 and −21.3‰, respectively) were applied to a C3 pasture soil with δ13C of −30.0±0.2‰. We found that water soluble organic carbon (WSOC) content was two to three times higher in the slurry amended plots compared with the unamended control. No significant change in the soil microbial biomass (SMB) carbon content was observed in the four weeks (772 h) following slurry application. Natural abundance 13C isotope analysis suggested a rapid initial incorporation (>25% within 2 h of application) of slurry-derived C in the SMB-C and WSOC pools of the 0–2 cm layer. Linear relationships were found between slurry-derived C in the whole soil, SMB, and WSOC for the 0–2 cm depth in the soil. Applied slurry-derived C was sequestered in the SMB pool in two phases. The first phase (0–48 h) was dominated by the incorporation of labile slurry C from the liquid phase, whereas beyond 48 h slurry-derived C was mainly from less mobile particulate C. No significant differences between treatments were found for invertase and xylanase. Urease activity was always higher in slurry treatments. Cellobiohydrolase, β-N-acetyl-glucosamidase, β-glucosidase and acid phosphatase activities became significantly higher in slurry treatments after 336 h. However, the observed temporal changes in enzyme activities were not correlated with the amounts of slurry-C incorporated in the SMB and WSOC pool. [Copyright &y& Elsevier]

Salinity intrusion into coastal regions is an increasing threat to agricultural production of salt sensitive crops like paddy rice. In the coastal Mekong Delta, farmers respond by shifting to more salinity tolerant agricultural production systems such as alternating rice-shrimp and permanent shrimp. While shrimps are sensitive to pesticide residues used on rice, the use of antibiotics in shrimp farming can cause contamination in rice crops. These patterns of cross-contamination are not well documented empirically in the rapidly changing agricultural landscape. Our objective was to understand changing pollution patterns induced by shifts in agricultural land use system. We addressed this by i) documenting pesticide and antibiotic use in three different agriculture land use systems (permanent rice, alternating rice-shrimp and permanent shrimp), and by ii) determining residues of pesticides and antibiotics in top soil layers of these three land use systems. Samples were taken in Sóc Trăng and Bến Tre province in the Mekong Delta, Vietnam. Chemical analyses comprised 12 of the most commonly used pesticides in rice paddies and six common antibiotics used in shrimp production. Results showed that residues of pesticides were present in all agricultural land use systems, including shrimp aquaculture. Active ingredients were mostly fungicides with a maximum concentration of 67 μg kg−1 found for isoprothiolane in permanent rice systems, followed by alternating rice-shrimp and permanent shrimp systems. Furthermore, antibiotics were present ubiquitously, with fluoroquinolones accumulating to larger amounts than sulfonamides and diaminopyrimidines. All concentrations were below critical lethal threshold values. Overall, farmers were most conscious of agrochemical use in alternating rice-shrimp systems to prevent harm to shrimps, which was reflected in overall lower concentrations of agrochemicals when compared to rice systems. Thus, alternating rice-shrimp systems present a low risk option in terms of food safety, which may bring additional benefits to this so far rather low-input system in brackish water transition zone. • Salt water intrusion shifts land use towards alternating/permanently saline systems. • Permanent shrimp and rice farms are sources of antibiotic and pesticide pollution, respectively. • Alternating rice-shrimp farming is a low-input system for antibiotics and pesticides. • Interconnected channel system facilitate cross-contamination between land use systems. [ABSTRACT FROM AUTHOR]

Antibiotic resistance genes in soil pose a potential risk for human health. They can enter the soil by irrigation with untreated or insufficiently treated waste water. We hypothesized that water flow paths trigger the formation of antibiotic resistance, since they transport antibiotics, multi-resistant bacteria and free resistance genes through the soil. To test this, we irrigated soil cores once or twice with waste water only, or with waste water added with sulfamethoxazole (SMX) and ciprofloxacin (CIP). The treatments also contained a dye to stain the water flow paths and allowed to sample these separately from unstained bulk soil. The fate of SMX and CIP was assessed by sorption experiments, leachate analyses and the quantification of total and extractable SMX and CIP in soil. The abundance of resistance genes to SMX ( sul1 and sul2 ) and to CIP ( qnrB and qnrS ) was quantified by qPCR. The sorption of CIP was larger than the dye and SMX. Ciprofloxacin accumulated exclusively in the water flow paths but the resistance genes qnrB and qnrS were not detectable. The SMX concentration in the water flow paths doubled the concentration of the bulk soil, as did the abundance of sul genes, particularly sul1 gene. These results suggest that flow paths do function as hotspots for the accumulation of antibiotics and trigger the formation of resistance genes in soil. Their dissemination also depends on the mobility of the antibiotic, which was much larger for SMX than for CIP. [ABSTRACT FROM AUTHOR]

Biopores are characterised by high concentrations of plant available nutrients and provide preferential pathways for root growth into the subsoil, thereby potentially enabling plants to access phosphorus (P) resources located in the subsoil. Here, we sampled biopores from a replicated agricultural field trial in Klein-Altendorf, Germany, to analyse their nutrient composition and P speciation as determined by Hedley sequential extraction and X-ray absorption near edge structure (XANES) spectroscopy. In addition, we analysed the oxygen isotopic composition of HCl P (δ 18 O HCl P ) as an indicator of long-term effects of biological P turnover. We found that biopore effects were most pronounced in the subsoil, where the concentration of easily extractable (labile) P tended to be greater in biopores than in bulk soil, as evident in both Hedley sequential extraction and XANES spectroscopy. We assume that these findings result from inputs of organic matter from the topsoil as well as an input of Ca-particles into subsoil biopores by earthworm activity. Biologically cycled P was subsequently precipitated as Ca-P as evident by δ 18 O HCl P values close to equilibrium in biopores even at great depths. When incubating bulk soil samples with 18 O-labelled water, however, we observed a significant increase of δ 18 O HCl P values in the topsoil, but only small if any changes of δ 18 O HCl P values in the subsoil. Thus, biopores present hotspots of P cycling in the subsoil, but the effect of biopores on overall P turnover in the bulk subsoil is limited. [ABSTRACT FROM AUTHOR]

Lacking knowledge about the spatial heterogeneity of heterotrophic soil respiration (R h ) hampers the prediction of larger-scale soil CO 2 efflux in patchy landscapes. The aim of this study was to establish a cost-efficient method for the rapid and simultaneous assessment of cumulative heterotrophic soil respiration (CO 2 ) at different sample spots. For this purpose, we adapted the laboratory-based, fully-automated Respicond VIII respirometer (Respicond) to detect CO 2 emission under field condition, installed the device in two temperate grasslands, and compared the R h flux data with those obtained using the so-called dynamic chamber method with infrared gas analyzers (IRGA). The results revealed good agreement between both R h measurements (Slope = 0.89, R 2 = 0.99). We conclude that adapting the Respicond for detection of CO 2 under field conditions is principally feasible, thus providing a new tool for the simultaneous assessment of CO 2 fluxes from different soil ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: The sorption of perfluorinated compounds (PFCs) to soils and sediments determines their fate and distribution in the environment, but there is little consensus regarding distribution coefficients that should be used for assessing the environmental fate of these compounds. Here we reviewed sorption coefficients for PFCs derived from laboratory experiments and compared these values with the gross distribution between the concentrations of PFCs in surface waters and sediments or between wastewater and sewage sludge. Sorption experiments with perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) suggest that their sorption can be described reasonably well as a partitioning-like process with an average log Koc of approximately 2.8 for PFOA and 3.0 for PFOS. However, median concentrations in sediments (PFOA, 0.27ngg−1; PFOS, 0.54ngg−1) or sewage sludge (PFOA, 37ngg−1; PFOS, 69ngg−1) in relation to median concentrations in surface water (PFOA, 3ngl−1; PFOS, 3ngl−1) or wastewater treatment effluent (PFOA, 24ngl−1; PFOS, 11ngl−1), suggest that effective log Koc distribution coefficients for the field situation may be close to 3.7 for PFOA and 4.2 for PFOS. Applying lab-based log Koc distribution coefficients can therefore result in a serious overestimation of PFC concentrations in water and in turn to an underestimation of the residence time of PFOA and PFOS in contaminated soils. Irrespective of the dissipation kinetics, the majority of PFOA and PFOS from contaminated soils will be transported to groundwater and surface water bodies. [Copyright &y& Elsevier]

Abstract: Stable soil aggregates and high microbial diversity are essential for efficient nutrient recycling in soil. This study evaluated effects of different arable land-use systems on soil aggregation and associated composition and total diversity of bacteria and fungi. For this purpose, 5- and 3-year-old field trials were selected, two in sub-humid (orthic Acrisols and oxidic Ferralsols) and one in semi-arid (chromic Cambisol) region in Kenya. The treatments included combinations of tillage (conventional tillage [CT] and reduced tillage [RT]), crop residue management (0 and 2tha−1 maize stover) and cropping systems (continuous maize, maize–soybean intercropping and rotation) in the sub-humid sites, and of different tillage (CT, no-till and tied-ridging) and organic fertilization management (manure and crop residue) in semi-arid Kenya. The innovativeness of this study is the research in tropical soils where the concept of aggregate hierarchy is not generally accepted yet. The results showed that aggregate mean weight diameter (MWD) at 0–15cm depths had increased from 19 to 34% under RT relative to CT management (P <0.05). Crop residue additions also significantly increased MWD by 22% at the top 5cm (P <0.01) compared to treatments without residue in oxidic Ferralsols. At all the three sites, tillage resulted in greatest shifts of bacterial and fungal community composition, while cropping system had largest positive effect on the total microbial diversity indices. Total microbial diversity indices as well as MWD were higher in soybean–maize intercropping systems than under rotation or continuous maize cropping. Changes in total bacterial diversity related inversely to changes in the amount of free silt+clay, while fungal diversity related inversely to the contents of soil macro-aggregates >2mm (P <0.05). We conclude that RT plus supply of organic resources and intercropping are best strategies to increase total diversity of soil bacteria and fungi and improve soil structure in these tropical soils. [Copyright &y& Elsevier]

Abstract: Comprehensive data sets for understanding the global distribution of black carbon (BC) in soil are lacking because the currently available methods are too time consuming for routine monitoring of BC in the environment. Here we report that reliable screening of soil BC can be achieved using mid-infrared spectroscopy (MIRS) and multivariate data analysis. Calibration models were built employing 309 samples from different soil depths and land use systems in America, Asia and Europe, characterized for soil organic carbon (SOC) and benzene polycarboxylic acids (BPCAs) as specific BC markers. About 99% of total SOC variability was explained by local calibrations with an error of prediction < 0.1g SOCkg−1 soil. In addition, BPCA carbon was assessable. The precision was lower (R 2 >0.8), partly reflecting different BC quality. A measure of the latter is the mellitic acid carbon percentage. This also correlated with MIRS patterns (R 2 ⩾0.6), which therefore even allowed classification of BC according to its degree of aromatic condensation. [Copyright &y& Elsevier]

A contamination of off-site aquatic environments with pesticides has been observed in the tropics, yet only sparse information exists about pesticide fate in such ecosystems. The objective of our semi-field study was to elucidate the fate of alachlor, atrazine, chlorpyrifos, endosulfan, metolachlor, profenofos, simazine, and trifluralin in the aqueous environment of the Pantanal wetland (MT, Brazil). To this aim, water and water/sediment microcosms of two sizes (0. 78 and 202l) were installed in the outskirts of this freshwater lagoon environment and pesticide dissipation was monitored for up to 50 d after application. The physical-chemical water conditions that developed in the microcosms were reproducible among field replicates for both system sizes. Pesticide dissipation was substantially enhanced for most pesticides in small microcosms relative to the large ones (reduced DT50 by a factor of up to 5. 3). The presence of sediment in microcosms led to increased persistence of chlorpyrifos, endosulfan, and trifluralin in the test systems, while for polar pesticides (alachlor, atrazine, metolachlor, profenofos, and simazine) a lesser persistence was observed. Atrazine, simazine, metolachlor, and alachlor were identified as the most persistent pesticides in large water microcosms (DT50 ⩾47 d); in large water/sediment systems endosulfan β, atrazine, metolachlor, and simazine showed the slowest dissipation (DT50 ⩾44 d). A medium-term accumulation in the sediment of tropical ecosystems can be expected for chlorpyrifos and endosulfan isomers (11–35% of applied amount still extractable at 50 d after application). We conclude that the persistence of the studied pesticides in aquatic ecosystems of the tropics is not substantially lower than during summer in temperate regions. [Copyright &y& Elsevier]

Abstract: Sustainable agriculture requires the formation of new humus from the crops. We utilized 13C and 15N signatures of soil organic matter to assess how rapidly wheat/maize cropping contributed to the humus formation in coarse-textured savanna soils of the South African Highveld. Composite samples were taken from the top 20cm of soils (Plinthustalfs) cropped for lengths of time varying from 0 to 98years, after conversion from native grassland savanna (C4). We performed natural 13C and 15N abundance measurements on bulk and particle-size fractions. The bulk soil δ 13C values steadily decreased from −14.6 in (C4 dominated) grassland to −16.5‰ after 90years of arable cropping. This δ 13C shift was attributable to increasing replacement of savanna-derived C by wheat crop (C3) C which dominated over maize (C4) inputs. After calculating the annual C input from the crop yields and the output from literature data, by using a stepwise C replacement model, we were able to correct the soil δ 13C data for the irregular maize inputs for a period of about one century. Within 90years of cropping 41–89% of the remaining soil organic matter was crop-derived in the three studied agroecosystems. The surface soil C stocks after 90years of the wheat/maize crop rotation could accurately be described with the Rothamsted Carbon Model, but modelled C inputs to the soil were very low. The coarse sand fraction reflected temporal fluctuations in 13C of the last C3 or C4 cropping and the silt fraction evidenced selective erosion loss of old savanna-derived C. Bulk soil 15N did not change with increasing cropping length. Decreasing δ 15N values caused by fertilizer N inputs with prolonged arable cropping were only detected for the coarse sand fraction. This indicated that the present N fertilization was not retained in stable soil C pool. Clearly, conventional cropping practices on the South African highlands neither contribute to the preservation of old savanna C and N, nor the effective humus reformation by the crops. [Copyright &y& Elsevier]

Abstract: Black carbon (BC), the ubiquitous stable product of incomplete combustion, is believed to be a potential sink for atmospheric CO2 and therefore a contributor to the Earth’s radiative heat balance. Nevertheless, analytical procedures to measure BC are inconsistent, giving a non-systematic variation by factors of 14–571 for estimates of its content in soil. We hypothesized that the HCl used to isolate benzene polycarboxylic acids (BPCAs) as markers for BC helps form these compounds, which could then cause an overestimation of the BC content of the soil. We found that indeed up to 90% of BPCA yields may be attributed to this HCl pre-treatment. To correct this error we developed a revised method that uses BPCAs as BC markers but which allows us to eliminate any confusion in the results. This aim was achieved by digestion with 4M trifluoroacetic acid (TFA). After oxidation with HNO3, the BPCAs were purified using a cation exchange resin and derivatized to form the trimethylsilyl derivatives. Analyses were performed using a gas chromatograph (GC) equipped with a flame ionization detector (FID); constant linearity was obtained at ⩾7ng BPCA injection amount and peak purity was determined using mass spectrometry (MS). The recovery of the BPCAs averaged 93.5±5.1% for pure standards and 95.0±3.6% for spiked charred plant material. The contribution of BPCAs from aspergillin to soil organic carbon was estimated to be negligible. No close correlation between the results obtained with the original method and our revised procedure was observed. [Copyright &y& Elsevier]

• The origin of colloids in streams indicates elemental transport pathways. • Monthly analysis of stream & groundwater, rainwater, throughfall, soil leachate. • Field flow fractionation revealed three fractions in all sample types. • Groundwater derived colloids dominated the stream signal. • Water flux and particle reformation affect the seasonal dynamics of particles. Biogeochemical changes of whole catchments may, at least in part, be deduced from changes in stream water composition. We hypothesized that there are seasonal variations of natural nanoparticles (NNP; 1–100 nm) and fine colloids (<300 nm) in stream water, which differ in origin depending on catchment inflow parameters. To test this hypothesis, we assessed the annual dynamics of the elemental composition of NNP and fine colloids in multiple water compartments, namely in stream water, above and below canopy precipitation, groundwater and lateral subsurface flow from the Conventwald catchment, Germany. In doing so, we monitored meteorological and hydrological parameters, total element loads, and analyzed element concentrations of org C, Al, Si, P, Ca, Mn and Fe by Asymmetric Flow Field Flow Fractionation (AF4). The results showed that colloid element concentrations were < 5 µmol/L. Up to an average of 55% (Fe) of total element concentrations were not truly dissolved but bound to NNP and fine colloids. The colloid patterns showed seasonal variability with highest loads in winter. The presence of groundwater-derived colloidal Ca in stream water showed that groundwater mainly fed the streams throughout the whole year. Overall, the results showed that different water compartments vary in the NNP and fine colloidal composition making them a suitable tool to identify the streams NNP and fine colloid sources. Given the completeness of the dataset with respect to NNP and fine colloids in multiple water compartments of a single forest watershed this study adds to the hitherto underexplored role of NNP and fine colloids in natural forest watersheds. [ABSTRACT FROM AUTHOR]