Imidacloprid is a widely used seed dressing insecticide in Brazil. However, the effects of this pesticide on non-target organisms such as soil fauna still present some knowledge gaps in tropical soils. This study aimed to assess the toxicity and risk of imidacloprid to earthworms Eisenia andrei and collembolans Folsomia candida in three contrasting Brazilian tropical soils.
Materials and methodsAcute and chronic toxicity assays were performed in the laboratory with both species in a tropical artificial soil (TAS) and in two natural soils (Oxisol and Entisol), at room temperature of 25 °C. The ecological risk was calculated for each species and soil by using the toxicity exposure ratio (TER) and hazard quotient (HQ) approaches.
Results and discussionAcute toxicity for collembolans and earthworms was higher in Entisol (LC50?=?4.68 and 0.55 mg kg?1, respectively) when compared with TAS (LC50?=?10.8 and 9.18 mg kg?1, respectively) and Oxisol (LC50collembolans?=?25.1 mg kg?1). Chronic toxicity for collembolans was similar in TAS and Oxisol (EC50 TAS?=?0.80 mg kg?1; EC50 OXISOL?=?0.83 mg kg?1), whereas higher toxicity was observed in Entisol (EC50?=?0.09 mg kg?1). In chronic assays with earthworms, imidacloprid was also more toxic in Entisol (EC50?=?0.21 mg kg?1) when compared to TAS (EC50?=?1.89 mg kg?1). TER and HQ values indicated a significant risk of exposure of the species to imidacloprid in all soils tested, and the risk in Entisol was at least six times higher than in Oxisol or TAS.
ConclusionsThe toxicity and risk of imidacloprid varied significantly between tropical soils, being the species exposure to this pesticide particularly hazardous in very sandy natural soils such as Entisol.
相似文献Fast and real-time prediction of leaf nutrient concentrations can facilitate decision-making for fertilisation regimes on farms and address issues raised with over-fertilisation. Cacao (Theobroma cacao L.) is an important cash crop and requires nutrient supply to maintain yield. This project aimed to use chemometric analysis and wavelength selection to improve the accuracy of foliar nutrient prediction.
Materials and methodsWe used a visible-near infrared (400–1000 nm) hyperspectral imaging (HSI) system to predict foliar calcium (Ca), potassium (K), phosphorus (P) and nitrogen (N) of cacao trees. Images were captured from 95 leaf samples. Partial least square regression (PLSR) models were developed to predict leaf nutrient concentrations and wavelength selection was undertaken.
Results and discussionUsing all wavelengths, Ca (R2CV?=?0.76, RMSECV?=?0.28), K (R2CV?=?0.35, RMSECV?=?0.46), P (R2CV?=?0.75, RMSECV?=?0.019) and N (R2CV?=?0.73, RMSECV?=?0.17) were predicted. Wavelength selection increased the prediction accuracy of Ca (R2CV?=?0.79, RMSECV?=?0.27) and N (R2CV?=?0.74, RMSECV?=?0.16), while did not affect prediction accuracy of foliar K (R2CV?=?0.35, RMSECV?=?0.46) and P (R2CV?=?0.75, RMSECV?=?0.019).
ConclusionsVisible-near infrared HSI has a good potential to predict Ca, P and N concentrations in cacao leaf samples, but K concentrations could not be predicted reliably. Wavelength selection increased the prediction accuracy of foliar Ca and N leading to a reduced number of wavelengths involved in developed models.
相似文献To identify the sources and levels of contamination with anthropogenically derived heavy metals (HMs) for appropriate pollution control. We quantified anthropogenic influences with respect to HM pollution in soil, based on multiple pollution indices and cluster analysis derived from the results of an annual nationwide survey conducted in Korea.
MethodsContamination levels of HMs in soils were quantitatively evaluated using multiple pollution indices: contamination factor (CF), geo-accumulation index (Igeo), Nemerow’s integrated pollution index (NIPI), and pollution load index (PLI). Hierarchical cluster analysis was conducted to elucidate the correlations between HMs and contamination sources. A total of 2214 HM concentration data including six contamination sources were used to evaluate the pollution state of anthropogenic effects of HMs.
ResultsThe CFs for Zn and Cu revealed a broad enrichment of these HMs in all pollution sources. Scrap recycling sites (SRS) had the highest likelihood of pollutant distribution in soil surfaces. NIPI and PLI varied with the extent of anthropogenic activities or land use, especially in SRS, waste disposal sites (WDS), transport maintenance sites (TMS), and industrial sites (INS), and anthropogenic sources were divided into three discrete clusters: INS-TMS-LDS (land development sites), SRS-WDS, and vicinities of industrial sites (VIS).
ConclusionOur results confirmed that soil pollution indices combined with cluster analysis were useful to identify sources of anthropogenic HMs in urban soil, as well as to assess the levels of HM contamination.
相似文献This study investigated the concentrations of cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), zinc (Zn), and polycyclic aromatic hydrocarbons (PAHs) in sediments collected from gully pots for road drainage in Hong Kong. The presence and intensity of anthropogenic contamination of road gully sediments were assessed. Identifications of potential sources of trace elements and PAHs were performed to help understand the situation for future control of pollution to the land and aquatic environments.
Materials and methodsGully sediment samples were collected from gully pots of 18 roads that are potentially exposed to different pollution sources in Hong Kong. The selection of roads considered different road features, adjacent land uses, and traffic volumes. Composite samples were collected for the analysis of trace elements (Cd, Cr, Cu, Pb, Ni, and Zn) and PAHs by an accredited environmental testing laboratory. Geo-accumulation index (Igeo), contamination factor (Cf), modified degree of contamination (mCd), ecological risk factor (Er), and pollution load index (PLI) were used to assess the level of ecological risk of trace element contamination. Positive matrix factorization (PMF) and PAH diagnostic ratios were applied to identify the sources of trace elements and PAHs.
Results and discussionElevated trace element concentrations were commonly found in gully sediments. The concentrations of Zn (267–3700 mg kg?1) were the highest compared to the other trace elements. Noticeable high concentrations of Cu (27–1020 mg kg?1), Pb (21–332 mg kg?1), and Cr (14–439 mg kg?1) were found in all samples. The PAH contents were moderate to high (0.6 to 24.7 mg kg?1). Commercial/industrial emissions and road features that cause frequent acceleration-deceleration and turning events showed important influences on the contaminant levels. Strong correlations between the concentrations of Cd, Cr, Pb, and Zn were identified, implying that these trace elements are likely from common sources. The contamination assessment indices reflect significant sediment pollution. The ecological risk ranges from the considerable/moderate-risk class to over the high-risk class.
ConclusionsThe collected gully sediments are identified as highly contaminated and need to be isolated from the environment upon final disposal. Through the comprehensive analysis of the collected data, this study provides a detailed insight into the contaminant levels of road gully sediments and potential sources of contamination. Disposal of gully sediments and potential impacts due to release of contaminants into the downstream aquatic environment during rainstorm events should receive attention and need further investigation.
相似文献Copper (Cu) is the earliest anthropogenic metal pollutant, but knowledge of Cu soil concentrations at ancient metalworking sites is limited. The objective of this work was to examine the ability of portable X-ray fluorescence to quantify Cu in soils at such sites.
Materials and methodsUsing a Bruker Tracer III-SD pXRF, we examine factory “scan” settings versus simple instrument parameter changes (a reduction in energy settings from 40 to 12 kV) to target analysis for Cu. We apply these to a set of uncontaminated samples (n?=?18, <?92 mg Cu kg?1) from Central Thailand and compare results to standard wet chemistry analysis (aqua regia digestion and ICP-OES analysis). We then apply the optimized method to a set of highly contaminated samples (n?=?86, <?14,200 mg Cu kg?1) from a known ancient smelting site.
Results and discussionWe demonstrate that simple changes to factory recommended “scan” settings can double the sensitivity of Cu determination via pXRF (“optimized limit of determination” of 19.3 mg kg?1 versus an initial value of 39.4 mg kg?1) and dramatically improve the accuracy of analysis. Changes to other results for other elements are variable and depend on concentration ranges, soil matrix effects, and pXRF response for the individual element. We demonstrate that pXRF can accurately determine Cu across a wide concentration range and identify grossly contaminated soil samples.
ConclusionsWe conclude that pXRF is a useful tool to rapidly screen and analyse samples at remote sites and can be applied to ancient metalworking sites. Simple optimization of the pXRF settings greatly improves accuracy and is essential in determining comparative background concentrations and “unaffected” areas. Application to other elements requires further element and matrix specific optimization.
相似文献Calcareous soils are characterized by high pH and phosphorus (P) fixation capacity. Increasing application of P fertilizer recently has significantly improved soil P concentration, especially available P (Olsen-P) and inorganic phosphate (Pi) fractions. However, there are few data available on the ability of soils with different initial Olsen-P levels to continuously supply P (i.e., P desorption capacity) to crops without additional P fertilization and on which Pi fraction exerts the greatest influence on P desorption capacity.
Materials and methodsFive soils with different initial Olsen-P levels (0.5, 14.3, 38.4, 55.4, 72.3 mg kg?1, hereafter refer as OP1, OP2, OP3, OP4, and OP5) but similar other soil properties were selected to evaluate the capacity of P desorption and its relationship with Pi fractions. Soil P was sequentially extracted once daily for 16 consecutive days using Olsen solution.
Results and discussionThe content and proportions of dicalcium phosphate fraction (Ca2-P), octacalcium phosphate fraction (Ca8-P), aluminum phosphorus fraction (Al-P), and iron phosphorus fraction (Fe-P) in Pi increased significantly with the increase of initial Olsen-P (P?<?0.01). Applied P fertilizer was mostly stored as Ca8-P in the soil. Soil P desorbed reached an equilibrium after 16 extractions for all soils, and P desorption capacity (12–358 mg kg?1) showed a significant linear relationship with initial Olsen-P (P?<?0.01), with an increase of 4.2 mg kg?1 desorbed P per 1 mg kg?1 increase of initial Olsen-P. Ca2-P exerted the conclusive effect on P desorption in the first four extractions, but Ca8-P played a more important role in the 16 extractions.
ConclusionsCa8-P was the greatest potential pool for P desorption after Ca2-P was depleted. P desorption capacity was significantly linearly related to initial Olsen-P (P?<?0.01). Different fertilizer use strategies were developed based on P desorption capacity for soils with different initial Olsen-P levels. The present study provided basic data on how to reduce effectively the application amount of chemical P fertilizer.
相似文献In contaminated streams, understanding the role of streambank and streambed source contributions is essential to developing robust remedial solutions. However, identifying relationships can be difficult because of the lack of identifying signatures in source and receptor pools. East Fork Poplar Creek (EFPC) in Oak Ridge, TN, USA received historical industrial releases of mercury that contaminated streambank soils and sediments. Here, we determined relationships between the contaminated streambank soils and sand-sized streambed sediments.
Materials and methodsField surveys revealed the spatial trends of the concentrations of inorganic total mercury (Hg) and methyl mercury (MeHg), Hg lability as inferred by sequential extraction, particle size distribution, and total organic carbon. Statistical tests were applied to determine relationships between streambank soil and streambed sediment properties.
Results and discussionConcentrations of Hg in streambank soils in the upper reaches averaged 206 mg kg?1 (all as dry weight) (n?=?457), and 13 mg kg?1 in lower reaches (n?=?321), while sand-sized streambed sediments were approximately 16 mg kg?1 (n?=?57). Two areas of much higher Hg and MeHg concentrations in streambank soils were identified and related to localized higher Hg concentrations in the streambed sediments; however, most of the streambank soils have similar Hg concentrations to the streambed sediments. The molar ratio of Hg to organic carbon, correlation between MeHg and Hg, and particle size distributions suggested similarity between the streambank soils and the fine sand-sized fraction (125–250 μm) collected from the streambed sediments. Mercury in the fine sand-sized streambed sediments, however, was more labile than Hg in the streambank soils, suggesting an in-stream environment that altered the geochemistry of sediment-bound Hg.
ConclusionsThis study revealed major source areas of Hg in streambank soils, identified possible depositional locations in streambed sediments, and highlighted potential differences in the stability of Hg bound to streambank soils and sediments. This work will guide future remedial decision making in EFPC and will aid other researchers in identifying source–sink linkages in contaminated fluvial systems.
相似文献Identification of phosphorus (P) species is essential to understand the transformation and availability of P in soil. However, P species as affected by land use change along with fertilization has received little attention in a sub-alpine humid soil of Tibet plateau.
Materials and methodsIn this study, we investigated the changes in P species using Hedley sequential fractionation and liquid-state 31P-NMR spectroscopy in soils under meadow (M) and under cropland with (CF) or without (CNF) long-term fertilization for 26 years in a sub-alpine cold-humid region in Qinghai–Tibet plateau.
Results and discussionLand-use change and long-term fertilization affected the status and fractions of P. A strong mineralization of organic P (OP) was induced by losing protection of soil organic matter (SOM) and Fe and Al oxides during land-use change and resulted in an increase of orthophosphate (from 56.49 mg kg?1 in M soils to 130.07 mg kg?1 in CNF soils) and great decreases of orthophosphate diesters (diester-P, from 23.35 mg kg?1 in M soils to 10.68 mg kg?1 in CNF soils) and monoesters (from 336.04 mg kg?1 in M soils to 73.26 mg kg?1 in CNF soils). Long-term fertilization boosted P supply but failed to reclaim soil diester-P (from 10.68 mg kg?1 in CNF soils to 7.79 mg kg?1 in CF soils). This may be due to the fragile protection from the combination of SOM with diester-P when long-term fertilization had only improved SOM in a slight extent.
ConclusionsThese results suggest that SOM plays an important role in the soil P cycling and prevents OP mineralization and losses from soil. It is recommended that optimization of soil nutrient management integrated with SOM was required to improve the P use efficiency for the development of sustainable agriculture.
相似文献Metallic nanomaterials (MNM) like cobalt oxide (nano-Co3O4) are currently attracting enormous interest owing to their unique size and shape-dependent properties and potential applications in various sectors. The aims of this study were to assess the toxicity of nano-Co3O4 and to propose a risk limit through the estimation of a Predicted No Effect Concentration (PNEC) for this MNM to soil biota.
Materials and methodsFor this purpose, a battery of sub-lethal ecotoxicological tests was performed to assess the influence of this MNM on four plant species (endpoints: germination and growth) and two invertebrate species (endpoints: avoidance and reproduction) following standard protocols. Further, biochemical endpoints (acetylcholinesterase [AChE], catalase [CAT], glutathione-S-transferase [GST] activity, and lipid peroxidation [LPO]) were also assessed in Eisenia andrei, one of the invertebrate species tested, in order to contribute for refining the PNEC value.
Results and discussionThe recorded data showed a significant inhibition in the germination of L. lycopersicum and in the growth of Z. mays, even at the lowest concentration tested (269.3 mg kg?1 soildw of nano-Co3O4). Concerning the soil invertebrates, the results showed only significant avoidance (p?<?0.05) by E. andrei in the soil contaminated with the highest concentration tested (1000 mg kg?1 soildw of nano-Co3O4), while no significant ecotoxicological effect on reproductive outputs of both species was recorded. However, the data reported for AChE, CAT, GST, and LPO showed significant effects at the range of concentrations tested in E. andrei. Thus, we recorded, the occurrence of oxidative stress and the enhancement of lipid peroxidation, on this invertebrate species.
ConclusionsThe data obtained in this study supports the proposal of a PNEC value of 9.1 mg kg?1 soildw for nano-Co3O4 in soil. The integration of data from biochemical endpoints allowed the refinement of the PNEC value and to obtain a more protective threshold.
相似文献Wetlands have a critical impact on the global carbon cycle. This study aims to investigate the spatial and vertical distribution of the soil organic carbon concentration (SOCc), to identify the differences of SOCc among swamps, marshes, bogs, and fens at a regional scale, and finally to examine the main environmental factors impacting SOCc at different depth intervals within different wetland types located in the Greater Khingan Mountains (GKM).
Materials and methodsA total of 218 soil samples were collected. SOCc was determined by the combustion-oxidation method. To analyze the impacts of wetland type, soil type, mean annual precipitation (MAP), mean annual temperature (MAT), evapotranspiration (ET), elevation (EL), and slope (SL) on SOCc, statistical analysis methods were executed, including ANOVA with the Duncan test, Pearson correlations analysis, and the stepwise multiple regressions analysis.
Results and discussionThe mean values of SOCc in the 0–30, 30–60, and 60–100-cm intervals were 130.4, 64.2, and 32.6 g kg?1, respectively. The wetland type played an important role in the pattern of SOCc in terms of significant differences (p?<?0.05) among the different wetland types in the 0–60-cm depth. However, significant differences were not found among different soil types. In terms of the wetland type, the highest SOCc was found in bogs (p?<?0.05), probably due to the higher MAP and lower MAT. The increased MAP (R2?=?0.1369, p?<?0.01) and decreased MAT (R2?=?0.1225, p?<?0.01) had positive associations on the wetland SOCc. ET (R2?=?0.2809, p?<?0.01), MAP (R2?=?0.2025, p?<?0.01), and EL (R2?=?0.0484, p?<?0.05) were positively correlated with marsh SOCc. Moreover, MAP was positively correlated with the bog SOCc (R2?=?0.1296, p?<?0.01). For vertical patterns, SOCc was higher in the 0–30-cm interval and decreased with depth. The impacts of environmental factors on SOCc decreased with depth for each wetland type. Models were developed to document the relations between the SOCc of marshes and fens and corresponding environmental factors.
ConclusionsWetland types largely differed in the soil carbon pools in the GKM of China. The relative importance of environmental factors was different for the SOCc values of various wetland types. To minimize carbon loss into the atmosphere, more protections are required for wetlands, especially in the 0–30-cm depth interval because it contains higher SOCc values and is more vulnerable and less stable than those in the deeper layers.
相似文献Wetlands in Mu Us Desert have severely been threatened by grasslandification over the past decades. Therefore, we studied the impacts of grasslandification on soil carbon (C):nitrogen (N):phosphorus (P) stoichiometry, soil organic carbon (SOC) stock, and release in wetland-grassland transitional zone in Mu Us Desert.
Materials and methodsFrom wetland to grassland, the transition zone was divided into five different successional stages according to plant communities and soil water conditions. At every stage, soil physical and chemical properties were determined and C:N:P ratios were calculated. SOC stock and soil respirations were also determined to assess soil carbon storage and release.
Results and discussionAfter grasslandification, SOC contents of top soils (0–10 cm) decreased from 100.2 to 31.79 g kg?1 in June and from 103.7 to 32.5 g kg?1 in October; total nitrogen (TN) contents of top soils (0–10 cm) decreased from 3.65 to 1.85 g kg?1 in June and from 6.43 to 3.36 g kg?1 in October; and total phosphorus (TP) contents of top soils (0–10 cm) decreased from 179.4 to 117.4 mg kg?1 in June and from 368.6 to 227.8 mg kg?1 in October. From stages Typha angustifolia wetland (TAW) to Phalaris arundinacea L. (PAL), in the top soil (0–10 cm), C:N ratios decreased from 32.2 to 16.9 in June and from 19.0 to 11.8 in October; C:P ratios decreased from 1519.2 to 580.5 in June and from 19.0 to 11.8 in October; and N:P ratios decreased from 46.9 to 34.8 in June and changed from 34.9 to 34.0 in October. SOC stock decreased and soil respiration increased with grasslandification. The decrease of SOC, TN, and TP contents was attributed to the reduction of aboveground biomass and mineralization of SOM, and the decrease of soil C:N, C:P, and N:P ratios was mainly attributed to the faster decreasing speeds of SOC than TN and TP. The reduction of aboveground biomass and increased SOC release led by enhanced soil respiration were the main reasons of SOC stock decrease.
ConclusionsGrasslandification led to lowers levels of SOC, TN, TP, and soil C:N, C:P, and N:P ratios. Grasslandification also led to higher SOC loss, and increased soil respiration was the main reason. Since it is difficult to restore grassland to original wetland, efficient practices should be conducted to reduce water drainage from wetland to prevent grasslandification.
相似文献Combining biodegradable chelating agents with phytoextraction is an efficient technique to amend metal-contaminated soils, but most studies have addressed remediation efficiency rather than a comprehensive understanding of the interactions among plant stress, metal accumulation, and metal bioavailability. This study aimed to investigate the effects of biodegradable chelating agents on improving the efficiency of phytoextraction for cobalt (Co)-contaminated soil by sweet alyssum (Lobularia maritima (L.)) and to explore the interrelationships among plant stress, Co accumulation, and Co bioavailability.
Materials and methodsSweet alyssum (three plants per pot) was grown in pots containing soil with Co added at 0, 40, and 60 mg kg?1, respectively. After 70 days of growth, we added four biodegradable chelating agents (EDDS, NTA, CA, and OA) at various concentrations (0, 2.5, 5.0, and 7.5 mmol kg?1). The plants were harvested after 7 days, and the biomass, reactive oxygen species (ROS) parameters, Co concentrations of the shoot and root, and available Co content in the soil were analyzed.
Results and discussionThe results demonstrate that chelating agents significantly (p?<?0.05) improved the phytoextraction capability of sweet alyssum and influenced plant growth and stress. The capability of EDDS to activate Co was higher than that of other chelating agents at identical concentrations in Co-contaminated soils. Furthermore, we observed that a moderate concentration (40 mg kg?1) of Co could promote plant growth and that high concentrations of Co (60 mg kg?1) and EDDS (7.5 mmol kg?1) cause enhanced stress to plant growth, even resulting in lower shoot Co accumulation than that in the moderate EDDS treatment (5.0 mmol kg?1).
ConclusionsThe present study demonstrates that the application of EDDS may be a better choice for Co phytoextraction than NTA, CA, and OA; nevertheless, a high concentration of EDDS may enhance the negative effects on plant growth, physiological traits, and Co accumulation.
相似文献Rare earth elements have been used as sediment tracers in river, estuarine and coastal environments but rarely applied as fluvial tributary tracers. Lanthanides (Ln) and yttrium (Y) were quantified in fluvial sediments of the Minho River lower course (NW Iberian Peninsula), where the catchment contains heterogeneous lithologies, to define the characteristic imprints of tributaries and their relevance in the riverine system.
Materials and methodsSurface sediments were sampled at 36 points in the lower Minho riverbed and its nine main tributaries.The <?2-mm fraction was sieved and ground, and ≈?100 mg was completely acid-digested with HF and aqua regia in closed Teflon bombs at 100 °C for 1 h. The residue was evaporated, re-dissolved with HNO3 and Milli-Q water, heated 20 min at 75 °C and diluted to 50 cm3 with Milli-Q water. Lanthanides and yttrium were determined using a quadrupole ICP-MS equipped with a Peltier impact bead spray chamber and a concentric Meinhard nebuliser. Blanks accounted for less than 1% of the element concentrations in the samples. The precision and accuracy of the analytical procedures were controlled through reference materials AGV-1 and MAG-1.
Results and discussionContents ranged from 22 to 153 mg Ln kg?1 and 1.5–22.9 mg Y kg?1 and ES-normalised light-heavy Ln fractionation, (LN/HN), varied between 0.6 and 2.6. These wide ranges, together with Eu and Ce anomalies and element-by-element Ln, varied with changes in parental rocks of the lower Minho basin. Minho sediments showed negative Ce anomalies (0.81?±?0.29) and positive Eu anomalies (1.23?±?0.18). Sediments received traces of granitic pegmatites and gneissic peralkaline rocks from two tributaries: the Gadanha (22.9 mg Y kg?1; 83 mg Ln kg?1; 0.60 LN/HN; 0.51 Eu/Eu*; 0.88 Ce/Ce*) and the Louro (15.9 mg Y kg?1; 110 mg Lnkg?1; 0.97 LN/HN; 0.69 Eu/Eu*; 1.49 Ce/Ce*). The Tamuxe tributary, flowing through a slate and quartzite fault, provided the lowest source (1.6 mg Y kg?1; 28 mg Ln kg?1; 2.48 LN/HN; 1.01 Eu/Eu*; 0.55 Ce/Ce*).
ConclusionsLanthanide and Y signatures in sediments may be used to trace land-tributary-river influences. The imprints are observed downstream of fluvial confluences but not in all cases, responding to basin lithological changes, particularly for pegmatites and peralkaline rocks. The general REE trend is described using Y contents only. Tributaries, which are responsible for one-fifth of the Minho water load, provide one-half of their sediments. Non-homogeneous sediment patterns may be magnified in dammed rivers such as the Minho.
相似文献Antibiotics are emerging contaminants of increasing concern in recent years. A total of 71 representative farmland soils along the Fenhe River in Shanxi Province were collected to investigate the occurrence of tetracyclines (TCs), sulfonamides (SAs), and quinolones (QLs). Additionally, the effects of population, livestock and poultry density, and soil properties on antibiotic distribution were also evaluated.
Materials and methodsFarmland topsoil samples along the Fenhe River were collected and freeze-dried at ??20 °C. The antibiotics in soils were extracted with a mixture of acetonitrile, EDTA-SPB, and Mg(NO3)2-NH3·H2O at the ratio of 2:1:1 (v/v/v). The extracted antibiotics were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS).
Results and discussionThe antibiotics were universally detected. The detection frequencies of sulfaclozine, enrofloxacin, norfloxacin, and ciprofloxacin reached 100%. Norfloxacin was the most abundant antibiotic in soils (27.21 μg kg?1). The distribution of antibiotics in soils along Fenhe River varied as midstream (8.62 μg kg?1) > downstream (4.58 μg kg?1) > upstream (3.49 μg kg?1). Oxytetracycline along the upstream and midstream was mainly caused by the emission of livestock and poultry and the overuse of human. The main sources of antibiotics along the downstream were livestock and poultry farms. Antibiotics were generally negatively correlated with sand content, pH, and organic matter, while cation exchange capacity had positive correlation with most of antibiotics such as tetracycline, sulfamonomethoxine, enrofloxacin, sulfameter, and sulfachinoxalin. SAs and TCs had little ecological risk, while QLs posed low or medium ecological risks.
ConclusionsThis study provided a scientific basis for antibiotic pollution control and agricultural safety supervision along the Fenhe River. Although no high risk of antibiotics was observed in soil samples based on the calculation, the widespread distribution of antibiotics in farmland soil along Fenhe River should be addressed.
相似文献Determination of the effectiveness of white mustard and oats in immobilising cadmium as a soil contaminant and determining the role of cellulose and urea in restoring homeostasis in soil under pressure from Cd2+.
Materials and methodsSoil samples were contaminated with cadmium (CdCl2·21/2H2O) at 0, 4, 8 and 16 mg Cd2+ kg?1. In order to reduce the negative impact of Cd2+, cellulose was introduced to the soil at the following rates: 0 and 15 g kg?1 and urea at 80 and 160 mg N kg?1. The yield of the above-ground parts and roots was determined on days 40 and 80 of the experiment, along with the cadmium content in the plant material. The enzyme activity was also determined, and the physical and chemical properties of the soil were determined on the day of the oats’ (aftercrop) harvest.
Results and discussionContamination of soil with Cd2+ at 4 to 16 mg kg?1 d.m. of soil reduced the yield of white mustard and oats. The tolerance index (TI) values indicate that oats (aftercrop) is more tolerant than white mustard of soil contamination with Cd2+. Cadmium accumulated more intensely in roots compared with the above-ground parts of the plants. The translocation index (TF) indicates smaller Cd2+ translocation from roots to above-ground parts, as it was below 1 in both plants. An addition of cellulose and nitrogen offsets the adverse impact of cadmium on plants. Arylsulphatase was the most sensitive to soil contamination with Cd2+, followed by dehydrogenases, catalase, β-glucosidase and urease, and alkaline phosphatase and acid phosphatase were the least sensitive. Contamination of soil with Cd2+ changed its physical and chemical properties only slightly.
ConclusionsWhite mustard and oats have phytostabilisation potential with respect to soil contaminated with cadmium. Cellulose introduced to the soil and fertilisation with urea alleviated the negative impact of cadmium on the growth and development of plants.
相似文献Soil consists of various sizes of aggregates, and different soil aggregates vary in their abilities to adsorb or transport metals. This study aimed to investigate the distribution behaviors of Cu from different fungicides in soil aggregates after a 15-month incubation.
Materials and methodsBordeaux mixture (CuSO4/Ca(OH)2?=?1/1 by weight, BR), copper nitrate (Cu(NO3)2·4H2O, CN), and copper oxychloride (3Cu(OH)2·CuCl2, CO) were applied to a representative Chinese Mollisol to reach the Cu content 200 mg kg?1. Five soil aggregate fractions, i.e., >?2000 μm, 2000–1000 μm, 1000–500 μm, 500–250 μm, and <?250 μm, were obtained by the wet sieving method. The modified Bureau Communautaire de Références (BCR) sequential extraction was applied to assess the Cu distribution among the main soil fractions.
Results and discussionThe highest Cu mass loading was found for the >?2000-μm soil aggregate. The input Cu was mainly in stable fractions, and the highest proportion was found for the residual fraction. The bioavailability and mobility of Cu from different fungicides in soils varied from each other, and they presented an order of CO > CN > BR. High bioavailability and transferring coefficients were found in the <?250-μm and >?2000-μm soil aggregates.
ConclusionsThis study indicated that the input Cu from fungicides mainly distributed in the >?2000-μm soil aggregates. Moreover, the CO-derived Cu presented a higher availability than the BR- and CN-derived Cu in the soil.
相似文献Natural organic acids, such as humic acid (HA), play crucial roles in biogeochemistry of anions and cations in soil due to their numerous functional groups on their surfaces. Selenium (Se) and cadmium (Cd) could bind strongly to HA; nevertheless, it is still unclear as to the effects of HA on Se and Cd uptake in rice which will be focused on in this paper.
Materials and methodsPot experiments were carried out at Huazhong Agricultural University, Wuhan City, Hubei Province, China. Agricultural soils were treated with different concentrations of HA (0, 4, and 8 g kg?1 soil) and Se (SeIV or SeVI) (0 and 2 mg kg?1 soil) as well as with base fertilizer 3 days prior to planting. For Cd treatment, experimental soils were treated with Cd (0 and 2 mg kg?1 soil) 1 month before sowing. For element determination, root (after DCB extraction) and shoot samples were digested with a mixed solution of HNO3-HClO4, and the Se and Cd in digest solution were measured by HG-AFS and ICP-MS, respectively. Fe, Se, and Cd in iron plaque were extracted by DCB extraction and measured by AAS, HG-AFS, and ICP-MS, respectively.
Results and discussionHA reduced Se (or Cd)-induced growth stimulation and Se and Cd uptake in rice seedlings, whereas iron plaque formation varied little with different treatments. HA inhibited SeIV (or SeVI) uptake in rice seedlings by reducing Se translocations from soil to iron plaque (or by increasing Se adsorption capacity of iron plaque and decreasing Se transport from iron plaque to root). HA reduced Cd uptake in rice seedlings by reducing Cd transport from soil to iron plaque and from iron plaque to root. Compared with single addition of SeIV or SeVI or HA, adding HA combined with SeIV or SeVI could further reduce Cd uptake in rice seedlings, whereas Se contents of aerial tissues did not change obviously.
ConclusionsHA inhibited the accumulation of Se (SeIV or SeVI) and Cd in rice seedlings; nevertheless, the mechanism was different. Compared with adding Se (or HA) alone, application of Se mixed with HA might be a more effective way to produce Se-enriched and Cd-deficient crop in Cd-contaminated soil.
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