•Cr stress reduced morpho-physiology and photosynthetic pigments in sunflower plant.•Citric acid application alleviated Cr induced toxicity in sunflower plant.•Citric acid scavenged reactive oxygen species by enhancing plant antioxidant defense.•Cr mobility and solubility increased in soil for plant uptake under citric acid.•Sunflower significantly accumulated and translocated Cr from roots to shoots.Soil and water contamination from heavy metals and metalloids is one of the most discussed and burning global issues due to its potential to cause the scarcity of healthy food and safe water. The scientific community is proposing a range of lab and field based physical, chemical and biological solutions to remedy metals and metalloids contaminated soils and water. The present study finds out a possibility of Chromium (Cr) extraction by sunflower from spiked soil under chelating role of citric acid (CA). The sunflower plants were grown under different concentrations of Cr (0, 5, 10 & 20 mg kg−1) and CA (0, 2.5 & 5 mM). Growth, biomass, gas exchange, photosynthesis, electrolyte leakage (EL), reactive oxygen species (ROS; malondialdehyde (MDA), hydrogen peroxide (H2O2) and the activities of antioxidant enzymes such as, superoxide dismutase (SOD), guaiacole values peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT) were measured. The results depicted a clear decline in plant height, root length, leaf area, number of leaves and flowers per plant along with fresh and dry biomass of all parts of plant with increasing concentration of Cr in soil. Similar reduction was observed in chlorophyll a and b, total chlorophyll, carotenoids, soluble protein, gas exchange attributes and SPAD. The increasing concentration of Cr also enhanced the Cr uptake and accumulation in plant roots, stem and leaves along with the production of ROS and EL. The activities of antioxidant enzymes increased with increasing Cr concentration from 0 to 10 mg, but decreased at 20 mg kg−1 soil. The CA application significantly alleviated Cr-induced inhibition of plant growth, biomass, photosynthesis, gas exchange, soluble proteins and SPAD value. Presence of CA also enhanced the activities of all antioxidant enzymes and reduced the production of ROS and EL. The chelating potential of CA increased the concentration and accumulation of Cr in plant roots, stem and leaves. It is concluded that the sunflower can be a potential candidate for the remediation of Cr under CA treatment, while the possibility may vary with genotype, Cr level and CA concentration.

Excessive use of antibiotics potentially threatens human health, agricultural production, and soil phytoremediation. This arouses concern over the potential adverse effects of a commonly used antibiotic, oxytetracycline (OTC), on plants used for soil remediation and possible stimulation of antibiotic resistance genes in soils. A greenhouse experiment was conducted to investigate different rates (0, 1, 5, and 25 mg kg–1) and frequencies (one single high and daily low application) of OTC addition to soil on phytoremediation of a heavy metal contaminated soil by Sedum plumbizincicola and/or Medicago sativa (alfalfa). After 90 days both Cd and Zn were substantially removed by phytoextraction into S. plumbizincicola shoots especially at the high OTC (25 mg kg–1) treatment which also led to inhibition of antioxidative enzyme activities in both plant species. Soil microbial activity decreased significantly with the addition of OTC, and this was ameliorated by planting alfalfa and S. plumbizincicola together. OTC at <5 mg kg–1 increased the biomass of both plant species, but the frequency of OTC addition had no effect on the rate of metal removal. Alfalfa exhibited greater detoxification ability and effectiveness in soil microbial activity promotion than S. plumbizincicola with intercropping. Phytoremediation by alfalfa and S. plumbizincicola in association can both promote the removal of heavy metals and also alleviate the toxic effects of pollutants on plants and soil microbes even at relatively high soil OTC concentrations.Keywords: biolog; enzyme activity; hyperaccumulator; microbial activity; oxytetracycline; phytoextraction;

Variation in soil moisture content can change metal availability. However, the effects of soil drying during wetting-drying cycles on metal availability have been little investigated. Metal availability to an imposed sink can be assessed by the diffusive gradients in thin film (DGT) technique. The purpose of this study was therefore to investigate the effects of the soil drying processes and previous soil moisture contents on metal availability using DGT.Two metal-polluted agricultural soils with contrasting pH (one acid and one calcareous) were collected from agricultural fields and were repeatedly phytoextracted with a Zn/Cd hyperaccumulator. Both soils, with and without phytoextraction, were subjected to two soil drying processes, i.e. drying from flooded conditions to 50 % maximum water holding capacity (WHC) and drying from 100 to 30 % WHC. Changes in metal availability induced by changing soil water moisture were examined using DGT.In acid soils, the availability of cadmium (Cd), zinc (Zn) and nickel (Ni) (but not copper) increased with drying from saturation to 50 % WHC. Drying soil from 100 to 30 % WHC had weak or no significant effects on available metals. Availabilities of Cd, Ni and Zn correlated well with available Al for both drying conditions. In calcareous soil, a decreasing trend of metal availability with soil drying from saturation to 50 % WHC or from 100 to 30 % WHC was found. Soils were also subjected to different wetting-drying cycles prior to drying. In acid soil, available copper (Cu) was correlated with dissolved organic carbon (DOC). Available Cd, Ni and Zn were correlated with available Al and increased with soil wetting-drying cycles in phytoextracted soil, but not in non-remediated soil. In calcareous soil, available Cu and Ni were correlated well with DOC and were higher with long dry periods. However, available Cd and Zn were lower in soils dried from the cycle of saturation to 50 % WHC.The results indicate that soil water regimes can be manipulated to alleviate soil metal availability, but they must be tailored to individual metals and different soil types, and soil moisture content before drying should be considered when dried soils are used for evaluation of metal availability.

A total of 58 dewatered sludge samples were collected from 58 sewage treatment plants (STPs) geographically located in 31 provincial cities of China; the concentrations of heavy metals and antibiotics were determined to monitor the pollutant levels on a large scale, and the pollutant concentrations in sludge samples from different sources of sewage sludge and different geographical regions were compared.All the samples were divided into two portions, one of which was air-dried for determination of heavy metals. The other portion was placed in a brown glass bottle and frozen at −20 °C for antibiotics analysis. Total heavy metals were digested with aqua regia and determined by atomic absorption spectrophotometry (Varian SpectrAA 220FS and Varian SpectrAA 220Z). The antibiotics were extracted with EDTA-sodium phosphate buffer with acetonitrile/Mg(NO3)2-NH3⋅H2O, v/v, 3:1 and analysed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) and quantified by the isotope-labelled internal standard method.In all the sludge samples, zinc was the most abundant metal followed by copper, with relatively low concentrations of chromium, lead, nickel and cadmium. Only 20 % of samples exceeded the Chinese class A values of heavy metal standards for agricultural use (GJ/T309-2009). Sixteen different antibiotics were detected in all the sludge samples, and fluoroquinolones (FQs) and tetracyclines (TCs) were more abundant than sulfonamides (SAs). Concentrations of ∑FQs, ∑TCs and ∑SAs ranged from 1,569 to 23,825 μg kg−1 (mean 8,274 μg kg−1, dry weight), from 592 to 37,895 μg kg−1 (mean 8,326 μg kg−1, dry weight) and from 20.1 to 117 μg kg−1 (mean 55.4 μg kg−1, dry weight), respectively. Tetracyclines (except chlortetracycline) were significantly correlated with zinc and lead. No significant regional trends were observed in the concentrations of heavy metals and antibiotics in sludges.Heavy metal concentrations are not the major factor restricting domestic and mixed flow sludge application, but the antibiotic concentrations in sludges are problematic; regulation of antibiotic use and establishment of standards to ensure safe handling of sludges are needed.

An analytical method for the analysis of four classes of antibiotics (tetracyclines, sulfonamides, fluoroquinolones and macrolides) has been developed and validated in this work. After optimizing the extraction and purification, the solvent consisting of a (EDTA-sodium phosphate buffer with acetonitrile:Mg(NO3)2-NH3·H2O, v/v, 3:1) was used as the extraction buffer, these antibiotics were extracted from agricultural soil, manure, and sewage sludge using ultrasonic-assisted extraction aided by mechanical shaking and followed by solid phase extraction (SPE) clean-up with hydrophilic–lipophilic balance (HLB) cartridges. The chromatographic separation was optimized, the analytes were separated and detected by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) and quantified by the isotope-labelled internal standard method. Mass spectral acquisition was done in the positive ion mode by applying multiple reaction monitoring (MRM) of two fragmentation transitions per analyte to provide a high degree of sensitivity and specificity. The calibration range used for all the antibiotics was 5.0–300.0 μg L−1 and each calibration curve was linear with a coefficient of determination (R2) > 0.997, the instrument detection limits (IDLs) and quantification limits (IQLs) ranged from 0.09 to 3.57 and 0.49 to 11.9 μg L−1, respectively. Spiked recoveries were obtained in the range 60–140% for these antibiotics from three different matrices, with the exception of NFC and OFC in soil (52–55%). Lower relative standard deviation (RSD < 17%) for seven replicates from each matrix at 50 μg kg−1 spiking level and the method detection limits (MDLs) obtained in the ranges 0.5–14.8 μg kg−1 from soil, 0.5–14.1 μg kg−1 from manure and 1.3–17.3 μg kg−1 from sludge for all the antibiotics studied indicate that the method was reliable and sensitive for extraction and determination of the target compounds in soil, manure and sludge matrices. Finally, the method was applied to analyse soil, manure and sewage sludge samples. Fluoroquinolones were the most dominant antibiotics and there were smaller amounts of sulfonamides in the soil, sludge and manure samples collected.

Water management affects the bioavailability of cadmium (Cd) and arsenic (As) in the soil and hence their accumulation in rice grains and grain yields. However, Cd and As show opposite responses to soil water content, but information, particularly on irrigation, is missing on a field scale. The purpose of the present study was therefore to find a water management regime that can lower accumulation of both Cd and As in grain without yield loss.Two rice (Oryza sativa L.) cultivars, A16 and A159, with different grain Cd accumulation capacities were employed in field plot experiments with four water management regimes comprising aerobic, intermittent, conventional practice and flooded. The dynamics of Cd and As bioavailability in the soil and Cd and As concentrations in roots, straw and grains were determined at the early tillering, full tillering, panicle initiation, filling and maturity stages of crop growth.The lower water content regimes (aerobic and intermittent) mostly led to higher soil HCl-extractable Cd than the higher soil water content regimes (conventional and flooded). HCl-extractable As in contrast was favoured by the higher soil water content treatments. Conventional and flooded irrigation accordingly gave higher plant As concentrations but lower Cd compared to aerobic and intermittent irrigation. Cd concentrations in roots and straw of both varieties increased with growth stage, especially in aerobic and intermittent regimes, while As concentrations in plants showed little change or a slight decrease. As the water irrigation volume increased from aerobic to flooded, brown rice Cd decreased from 1.15 to 0.02 mg kg−1 in cultivar A16 and from 1.60 to 0.05 mg kg−1 in cultivar A159, whereas brown rice As increased. Aerobic and flooded treatments produced approximately 10–20 % lower grain yields than intermittent and conventional treatments. Cultivars with low Cd accumulation capacity show higher brown rice grain As than those with high Cd uptake capacity.Of the four water management regimes, the conventional irrigation method (flooding maintained until full tillering followed by intermittent irrigation) ensured high yield with low Cd and As in the brown rice and so remains the recommended irrigation regime.

Land use in east China tends to change from paddy rice to vegetables or other high-value cash crops, resulting in high input rates of organic manures and increased risk of contamination with both heavy metals (HMs) and antibiotics. This investigation was conducted to determine the accumulation, distribution and risks of HMs and tetracyclines (TCs) in surface soils and profiles receiving different amounts of farmyard manure. Soil samples collected from suburbs of Hangzhou city, Zhejiang province were introduced to represent three types of land use change from paddy rice to asparagus production, vineyards and field mustard cultivation, and divided into two portions, one of which was air-dried and sieved through 2-, 0.3- and 0.149-mm nylon mesh for determination of pH and heavy metals. The other portion was frozen at −20 °C, freeze-dried and sieved through a 0.3-mm nylon mesh for tetracyline determination. HM and TC concentrations in surface soils of 14-year-old mustard fields were the highest with total Cu, Zn, Cd and ∑TCs of 50.5, 196, 1.03 mg kg−1 and 22.9 μg kg−1, respectively, on average. The total Cu sequence was field mustard > vineyards > asparagus when duration of land use change was considered; oxytetracycline (OTC) and doxycycline were dominant in soils used for asparagus production; OTC was dominant in vineyards and chlortetracycline (CTC) was dominant in mustard soils. There were positive pollution relationships among Cu, Zn and ∑TCs, especially between Cu and Zn or Cu and ∑TCs. Repeated and excessive application of manures from intensive farming systems may produce combined contamination with HMs and TCs which were found in the top 20 cm of the arable soil profiles and also extended to 20–40 cm depth. Increasing manure application rate and cultivation time led to continuing increases in residue concentrations and movement down the soil profile.

Sedum plumbizincicola X.H. Guo et S.B. Zhou ex L.H. Wu (Crassulaceae), a new species restricted to lead–zinc mining areas in Zhejiang Province, China, is described and illustrated. This taxon belongs to sect. Sedum (H. Ohba) S.H. Fu based on the adaxially gibbous carpels and follicles. It superficially resembles S. alfredii Hance and three other Sedum species found in the same area, but differs from these other taxa in bearing 4-merous flowers. Differences in geographical distribution, growth habit, phenology, macromorphology, leaf and stem anatomy, as well as seed micromorphology among S. plumbizincicola, S. alfredii and other related taxa in the genus Sedum are also reported. nrDNA internal transcribed spacers (ITS) sequences from seven populations of S. plumbizincicola support the recognition of this as a taxonomic entity distinct from S. alfredii.

Phytoextraction has become one of the most promising remediation techniques for heavy metal (HM) contaminated soils. However, the technique invariably produces large amounts of HM-enriched hyperaccumulators, which need further safe disposal. In this study, two different thermal treatment methods are investigated as potential options for evaporative separation of HMs from the residues. A horizontal tube furnace and a vertical entrained flow tube furnace were used for testing the disposal of grounded hyperaccumulators. The release characteristics of HMs (Cd, Cu, Pb, and Zn) into flue gas and residues were investigated for thermal treatment of the Cd and Zn hyperaccumulators Sedum plumbizincicola and Sedum alfredii. In a horizontal tube furnace, incineration favors the volatilization of Cu and Cd in contrast to pyrolysis. The percentages of HMs in residues after incineration are lower than those after pyrolysis, especially for Cd, Pb, and Zn. However, in an entrained flow tube furnace, Zn content in flue gas increases with increasing temperature, but Cu and Cd contents are fluctuated. In addition, a higher incineration temperature enhances the Cu content in residues.

Two contrasting soils receiving long-term application of commercial sewage sludge fertilizers in China were investigated to determine the concentrations of selected nutrients, heavy metals (HMs) and polybrominated diphenyl ethers (PBDEs) present to evaluate the impact of sewage sludge fertilizer on soil fertility and environmental risk.Soil samples were collected from Tangshan City, Hebei province and Ningbo City, Zhejiang province and divided into two portions, one of which was air-dried and sieved through 2-, 0.25- and 0.149-mm nylon mesh for determination of nutrients and heavy metals. The other portion was frozen at −20°C, freeze-dried and sieved through 2-mm nylon mesh for PBDE analysis. The concentrations of nutrients, heavy metals and PBDEs were determined in all samples.Concentrations of nutrients and heavy metals in soils amended with low rates of sewage sludge fertilizer (SSF) and conventional fertilizer were compared. After long-term excessive amendment with SSF from Ningbo City (SSF-N), the concentrations of soil total N, P, aqua regia-extractable HMs and DTPA extractable HMs were higher than the control, especially in the arable layer. Moreover, the concentration of aqua regia-extractable Zn (457 mg kg−1) exceeded the recommended China Environmental Quality Standard for soils (GB15618-1995). All 8 target PBDE congeners were found in fertilizer SSF-N and soil with excessive amendment with SSF-N for 12 years, but the concentrations of 8 different PBDEs in SSF-N-amended soil were not significantly different from control soil.Both economic and environmental benefits can be obtained by careful application of sewage sludge fertilizer to recycle plant nutrients. Repeated and excessive application rates of sewage sludge fertilizer may pose environmental risk, especially in respect of soil heavy metal and PBDE contamination, and high concentrations of phosphorus may also be environmentally detrimental.

We investigated the chemical fractions of Zn, Cd and Cu in soils collected from positions at different distances from a copper smelter and studied the relationships between distribution patterns of Zn, Cd and Cu, fractions and soil organic carbon (SOC), especially “black carbon” (BC), in contaminated soils. The relationships between soil particle size and concentrations of Zn and Cd in contaminated soil were also examined.Soil samples were collected from field sites at different distances from the copper smelter, air-dried and passed through 0.25-mm and 0.149-mm nylon mesh sieves. The SOC and BC were determined. Aqua regia and sequentially extracted Zn, Cd and Cu fractions in soil and the different sizes of soil particles, and metal concentrations (Zn, Cd and Cu) in BC were also determined.The soils were heavily contaminated by fly ash from the copper smelter. Concentrations of Zn, Cd and Cu in soil and SOC decreased with increasing distance from the smelter. Concentrations of Zn and Cd in the surface soil (0–15 cm) decreased from 27,017 to 892 mg kg−1 and from 18.7 to 1.04 mg kg−1, respectively. Soil BC and concentrations of Zn, Cd and Cu in the BC fraction showed significant and positive relationships with the corresponding aqua regia metal concentrations in soil. Soil Zn and Cd occurred predominantly in the exchangeable and reducible fractions, but residual and oxidisable fractions of Cu that were not considered mobile or bioavailable were predominant (>60%). Concentrations of Zn and Cd in the soil particle size fractions tended to increase with decreasing particle size.The Cd and Zn and BC were all derived from the fly ash of the smelter. Concentrations of Zn and Cd and BC in the soil decreased significantly with increasing distance from the smelter. Zinc and Cd in contaminated soils increased as particle size decreased, and were mainly in highly available exchangeable-, water- and acid-soluble, and reducible fractions.

•Different concentrations and application frequencies of OTC were compared in a novel study.•Microbial biomass carbon/Cmic increased more with a single application of a large amount of OTC.•Daily repeated low OTC additions stimulated Cmic and McIntosh index between 60 and 90 d.•Single additions of equal amounts of OTC had greater effects on soil microbial metabolism.Antibiotics in soil can interfere with the structure and function of the soil microbial community and represent a potential genetic pollution risk. The effects of different concentrations and application frequencies of oxytetracycline (OTC) to an agricultural soil on the activities of soil microorganisms and enzymes were investigated during incubation of 120 days. Single once-only high application treatments (1, 3.6, 10, and 30 mg OTC kg−1 soil) and one daily low application treatment (0.03 mg OTC kg−1 soil every day) were compared to simulate OTC application to the soil in sewage sludges or manures or from waste water irrigation. In the single addition treatments, microbial biomass carbon (Cmic) in the soil increased 2.17–3.29 times and 1.37–2.08 times after 7 and 42 d of incubation, respectively, but nitrification potential increased sharply to 3.01–10.9 times after 28 d and dehydrogenase activity was also significantly stimulated after 14 d compared to the zero OTC control and decreased sharply by 120 d. The daily OTC addition treatments promoted Cmic (up to 2.64 times) and increased the McIntosh index (p < 0.05) between 60 and 90 days as calculated using Biolog data and compared to the zero OTC control. A single high rate of OTC addition showed a generally more pronounced negative effect on soil microbial community metabolism (but not on functional diversity indices of the soil microbial community) than repeated small rates of addition because with equal amounts of added OTC (single 3.6 mg kg−1 and daily 0.03 mg kg−1 OTC) Cmic, nitrification potential and neutral phosphatase activity at 120 d were significantly lower in the single application treatments.

Long-term field experiments were established in 1990 at two sites, one in northeast (17 years) and the other in south China (16 years) to better understand the effects of pig manure and inorganic fertilizers on heavy metal accumulation in soil. Experimental treatments were NPK and SNPK (Straw + NPK) fertilizers and two application rates of pig manure plus NPK at the site in northeast China and NK, NP, NK and PK fertilizers and pig manure with and without PK in the south. Unamended control plots were included at both sites. Both application rates of pig manure with NPK in the northeast for 17 years increased concentrations of aqua regia extractable Cd in the topsoil by about 17.0- and 18.9-fold but repeated applications of straw for 17 years did not result in a marked accumulation of Cd in the surface soil. Similar results were found in the southern plots treated with pig manure (with or without NPK). The distribution patterns of DTPA-extractable Cd in the northeast (BSES) were similar to that of aqua regia-Cd. HCl-extractable Cd in the topsoil treated with pig manure (with or without NPK) in the south exceeded that in the control soil by about 4.5- and 5.4-fold (RSES). Sequential extraction results show that in the northeast pig manure from intensively managed pig farms led to accumulation of Cd in both exchangeable and reducible soil fractions.Highlights► Routine annual field applications of pig manure led to marked accumulation of Cd. ► The Cd in pig manures was from feed additives at intensively managed pig farms. ► Long-term field trials at two contrasting Chinese agricultural soils confirmed this.

A total of 222 surface soil samples and 40 plant samples were collected to investigate the spatial distribution and possible sources of soil heavy metals and to know the uptake and translocation of heavy metals from roots to different plant parts in a representative vegetable production area in the Baguazhou Island, a suburb of Nanjing City, East China. The arithmetic mean values of total Cd, Cr, Cu, Ni, Pb, and Zn concentrations in the soils were 0.314, 133, 41.0, 58.0, 31.8, and 114 mg kg−1, respectively. All of these values were above the topsoil background values in the Nanjing area. Multivariate and geostatistical analyses showed that soil Cd contamination was derived mainly from agricultural practices. In contrast, Cu and Zn were derived mainly from soil parent materials and Pb from atmospheric deposition from highway gasoline stations. Artemisia selengensis, a locally important specialty vegetable, accumulated heavy metals primarily in the edible leaves. The general distribution of heavy metal concentrations in this plant species showed that the highest occurred in the leaves, intermediate in the stems and lowest in the roots. Cd had the highest concentration factor (root–to–soil ratio) and may pose increased health risks in the future to the local population through the consumption of contaminated vegetables.

An analytical method for the analysis of four classes of antibiotics (tetracyclines, sulfonamides, fluoroquinolones and macrolides) has been developed and validated in this work. After optimizing the extraction and purification, the solvent consisting of a (EDTA-sodium phosphate buffer with acetonitrile:Mg(NO3)2-NH3·H2O, v/v, 3:1) was used as the extraction buffer, these antibiotics were extracted from agricultural soil, manure, and sewage sludge using ultrasonic-assisted extraction aided by mechanical shaking and followed by solid phase extraction (SPE) clean-up with hydrophilic–lipophilic balance (HLB) cartridges. The chromatographic separation was optimized, the analytes were separated and detected by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) and quantified by the isotope-labelled internal standard method. Mass spectral acquisition was done in the positive ion mode by applying multiple reaction monitoring (MRM) of two fragmentation transitions per analyte to provide a high degree of sensitivity and specificity. The calibration range used for all the antibiotics was 5.0–300.0 μg L−1 and each calibration curve was linear with a coefficient of determination (R2) > 0.997, the instrument detection limits (IDLs) and quantification limits (IQLs) ranged from 0.09 to 3.57 and 0.49 to 11.9 μg L−1, respectively. Spiked recoveries were obtained in the range 60–140% for these antibiotics from three different matrices, with the exception of NFC and OFC in soil (52–55%). Lower relative standard deviation (RSD < 17%) for seven replicates from each matrix at 50 μg kg−1 spiking level and the method detection limits (MDLs) obtained in the ranges 0.5–14.8 μg kg−1 from soil, 0.5–14.1 μg kg−1 from manure and 1.3–17.3 μg kg−1 from sludge for all the antibiotics studied indicate that the method was reliable and sensitive for extraction and determination of the target compounds in soil, manure and sludge matrices. Finally, the method was applied to analyse soil, manure and sewage sludge samples. Fluoroquinolones were the most dominant antibiotics and there were smaller amounts of sulfonamides in the soil, sludge and manure samples collected.