Phosphorus doped cyanobacterial biochar catalyzes efficient persulfate oxidation of the antibiotic norfloxacin.

In this study, cyanobacterial biochars (CBs) enriched/doped with non-metallic elements were prepared by pyrolysis of biomass amended with different N, S, and P containing compounds. Their catalytic reactivity was tested for persulfate oxidation of the antibiotic norfloxacin (NOR). N and S doping failed to improve CB catalytic reactivity, while P doping increased reactivity 5 times compared with un-doped biochar. Biochars produced with organic phosphorus dopants showed the highest reactivity. Post-acid-washing improved catalytic reactivity. In particular, 950 ℃ acid-washed triphenyl-phosphate doped CB showed the largest degradation rate and reached 79% NOR mineralization in 2 h. Main attributes for P-doped CBs high reactivity were large specific surface areas (up to 655 m2/g), high adsorption, high C-P-O content, graphitic P and non-radical degradation pathway (electron transfer). This study demonstrates a new way to reuse waste biomass by producing efficient P-doped metal-free biochars and presents a basic framework for designing carbon-based catalysts for organic pollutant degradation.

Fast peroxydisulfate oxidation of the antibiotic norfloxacin catalyzed by cyanobacterial biochar.

Peroxydisulfate (PDS) is a common oxidant for organic contaminant remediation. PDS is typically activated by metal catalysts to generate reactive radicals. Unfortunately, as radicals are non-selective and metal catalysts may cause secondary contamination, alternative selective non-radical pathways and non-metal catalysts need attention. Here we investigated PDS oxidation of commonly detected antibiotic Norfloxacin (NOR) using cyanobacterial nitrogen rich biochars (CBs) as catalysts. NOR was fully degraded by CB pyrolysed at 950 °C (CB950) within 120 min. CB950 caused threefold faster degradation than low pyrolysis temperature (PT) CBs and achieved a maximum surface area normalized rate constant of 4.38 × 10-2 min-1 m-2 L compared to widely used metal catalysts. CB950 maintained full reactivity after four repeated uses. High defluorination (82%) and mineralization (>82%) were observed for CB950/PDS. CBs were active over a broad pH range (3-10), but with twice as high rates under alkaline compared with neutral conditions. NOR is degraded by organic, •OH and SO4•- radicals in low PT CBs/PDS systems, where the presence of MnII promotes radical generation. Electron transfer reactions with radicals supplemented dominate high PT CBs/PDS systems. This study demonstrates high PT biochars from algal bloom biomass may find use as catalysts for organic contaminant oxidation.

A critical review of phytoremediation for acid mine drainage-impacted environments.

Acid mine drainage (AMD), a waste product of mining activities containing sulfates, iron and heavy metals, causes severe environmental degradation and pose risks to human health and sustainable development. Areas impacted by AMD are lacking remediation techniques that holistically address the ecologic, social, and economic needs of affected communities, for which phytoremediation is a promising solution. This review article introduces AMD and AMD-impacted environments and critically discusses phytomanagement, phytoprotection, and phytorestoration approaches towards AMD-impacted environments. Continued research and application of such approaches will help optimize resource and revenue-generating potentials, address biodiversity loss and carbon storage concerns of climate change, and promote sustainable agricultural management. With a focus on energy crops, phytomining critical elements, carbon storage, co-cropping, allelopathy, and ecosystem restoration, this review examines phytoremediation research that addresses positive economic and environmental opportunities for AMD-impacted environments.

Method for assessment of stormwater treatment facilities - Synthetic road runoff addition including micro-pollutants and tracer.

Stormwater treatment facilities (STFs) are becoming increasingly widespread but knowledge on their performance is limited. This is due to difficulties in obtaining representative samples during storm events and documenting removal of the broad range of contaminants found in stormwater runoff. This paper presents a method to evaluate STFs by addition of synthetic runoff with representative concentrations of contaminant species, including the use of tracer for correction of removal rates for losses not caused by the STF. A list of organic and inorganic contaminant species, including trace elements representative of runoff from roads is suggested, as well as relevant concentration ranges. The method was used for adding contaminants to three different STFs including a curbstone extension with filter soil, a dual porosity filter, and six different permeable pavements. Evaluation of the method showed that it is possible to add a well-defined mixture of contaminants despite different field conditions by having a flexibly system, mixing different stock-solutions on site, and use bromide tracer for correction of outlet concentrations. Bromide recovery ranged from only 12% in one of the permeable pavements to 97% in the dual porosity filter, stressing the importance of including a conservative tracer for correction of contaminant retention values. The method is considered useful in future treatment performance testing of STFs. The observed performance of the STFs is presented in coming papers.

Phosphorus saturation and mobilization in two typical Chinese greenhouse vegetable soils.

Chinese greenhouse vegetable production can cause eutrophication of fresh waters due to heavy use of fertilizers. To address this, phosphorus (P) leaching was compared between two major greenhouse vegetable soils from Jiangsu Province, Southeast China: clayey and acid-neutral Guli Orthic Anthrosols and sandy and alkaline Tongshan Ustic Cambosols. A total of 20 intact soil columns were collected based on differences in total P content varying between 1360 and 11,220 mg kg-1. Overall, six leaching experiments were carried out with collection of leachates over 24 h. Very high P concentrations, with a mean of 3.43 mg L-1, were found in the leachates from P rich Tongshan soils. In contrast, P leaching from fine-textured but less P rich Guli soils rarely exceeded the suggested environmental P threshold of 0.1 mg L-1. Strong linear correlations were found between different soil test P measures (STPs) or degree of P saturations (DPSs) and dissolved reactive P (DRP) for Tongshan soil columns. The correlations with Olsen P (r2 = 0.91) and DPS based on MehlichIII extractable calcium (DPSM3-Ca) (r2 = 0.87) were the most promising. An Olsen P value above 41 mg kg-1 or a DPSM3-Ca above 3.44% led to DRP leaching exceeding 0.1 mg L-1. Accordingly, more than 80% of Tongshan soils resulted in DRP leaching exceeding the environmental P threshold. In conclusion P rich alkaline sandy soils used for greenhouse vegetable production are at high risk of P mobilization across China.

Diffusive Gradients in Thin Films as a Reference Method for Assessing Soil Phosphorus by Visual and Near-Infrared Spectroscopy.

Phosphorus (P) deficiency is a severe challenge in many agricultural areas around the globe, while at the same time, aquatic environments are threatened by leaching and runoff of excess P in other areas. Accurate, cheap, and rapid assessment of crop P needs and risk of P loss is therefore necessary to optimize the use of P fertilizer worldwide. The purpose of this study was to develop a method to predict soil P concentrations by visual and near-infrared spectroscopy using reference P concentrations determined by diffusive gradients in thin films (DGT); Olsen P results were included for comparison. The study was conducted on paddy soils from six main rice-producing ( L.) provinces in southern China. Using DGT P as a reference resulted in a better visual and near-infrared calibration to predict soil P concentrations, as compared with using Olsen P.

High-resolution imaging of labile phosphorus and its relationship with iron redox state in lake sediments.

A thorough understanding of the labile status and dynamics of phosphorus (P) and iron (Fe) across the sediment-water interface (SWI) is essential for managing internal P release in eutrophic lakes. Fe-coupled inactivation of P in sediments is an important factor which affects internal P release in freshwater lakes. In this study, two in-situ high-resolution diffusive gradients in thin films (DGT) techniques, Zr-Oxide DGT and ZrO-Chelex DGT, were used to investigate the release characteristics of P from sediments in a large freshwater lake (Dongting Lake, China; area of 2691 km2) experiencing a regional summer algal bloom. Two-dimensional distributions of labile P in sediments were imaged with the Zr-Oxide DGT without destruction of the original structure of the sediment layer at four sites of the lake. The concentration of DGT-labile P in the sediments, ranging from 0.007 to 0.206 mg L-1, was highly heterogeneous across the profiles. The values of apparent diffusion flux (Fd) and release flux (Fr) of P varied between -0.027-0.197 mg m-2 d-1 and 0.037-0.332 mg m-2 d-1, respectively. Labile P showed a high and positive correlation (p < 0.01) with labile Fe(II) in the profiles, providing high-resolution evidence for the key role of Fe-redox cycling in labile P variation in sediments.

Aluminum Oxide-Coated Sand for Improved Treatment of Urban Stormwater.

Infiltration facilities for urban stormwater runoff, such as biofilters, rain gardens, and curb extensions, typically contain an engineered soil mixture for effective drainage and retention of pollutants. The treatment efficiency of such soils is generally considered high for many pollutants. However, recent studies have revealed that in situ mobilization of soil organic matter may cause leaching of a range of pollutants and therefore diminish the long-term performance of engineered soils. The purpose of this study was to develop and test sand coated with aluminum (Al) oxides for improving the retention of organic matter and a range of common pollutants in engineered soils. Two alternative Al-coating methods were successfully developed in the laboratory. The Al coating of the sand increased the specific surface area from 0.3 to 1.1 m g to 0.87 to 2.2 m g depending on sand fraction. One method was upscaled to produce 100 kg coated sand. The stability of the coatings was studied in batch experiments. Dry shaking showed a high resistance of the coating against mechanical stress. Increasing the ionic strength by the addition of NaCl seemed to improve the stability of the coatings. Varying pH showed that acidic conditions could compromise the Al coating stability. Overall, one coating method showed slightly better results in terms of higher surface area and stability. The Al coating significantly improved the retention capacity of the sand toward dissolved organic carbon. The results document that it is possible to coat sand effectively with Al oxides and consequently to improve the retention capacity and lifetime of engineered soils for urban stormwater management.

Decreased abundance and diversity of culturable Pseudomonas spp. populations with increasing copper exposure in the sugar beet rhizosphere.

Recent studies have indicated that culturable bacteria constitute highly sensitive bioindicators of metal-induced stress in soil. We report the impact of different copper exposure levels characteristic of contaminated agricultural soils on culturable Pseudomonas spp. in the rhizosphere of sugar beet. We observed that the abundance of Pseudomonas spp. was much more severely affected than that of the general population of culturable heterotrophic bacteria by copper. For diversity assessment, Pseudomonas isolates were divided into operational taxonomic units based on amplified ribosomal DNA restriction analysis and genomic PCR fingerprinting by universally primed PCR. Copper significantly decreased the diversity of Pseudomonas spp. in the rhizosphere and significantly increased the frequency of copper-resistant isolates. Concomitant chemical and biological analysis of copper in the rhizosphere and in bulk soil extracts indicated no rhizosphere effect and a relatively low copper bioavailability in the studied soil, suggesting that the observed effects of copper may occur at lower total concentrations in other soils. We conclude that culturable Pseudomonas sensu stricto constitutes a highly sensitive and relevant bioindicator group for the impact of copper in the rhizosphere habitat, and suggest that continued application of copper to agricultural soils poses a significant risk to successful rhizosphere colonization by Pseudomonas spp.