Reduced Plant Uptake Research Articles

Revealing the size effect mechanisms of micro(nano)plastics on nitrogen removal performance of constructed wetland

Micro(nano)plastics (MPs) in aquatic environments can disrupt wastewater treatment, particularly nitrogen removal in constructed wetlands (CWs). However, their broader effects on microbial and plant nitrogen metabolism remain unclear. This study investigated the effects of different-sized MPs (4 mm, 100 µm, and 100 nm) on nitrogen transformation in CWs. Results revealed that 4 mm- and 100 µm-MPs did not significantly affect total nitrogen (TN) removal, although 100 µm-MPs significantly increased leaf antioxidant enzyme activities and reduced plant uptake of nitrogen by 12.95 % (p < 0.05). In contrast, 100 nm-MPs decreased the TN removal efficiency by 7.97 % via inhibiting both nitrification and denitrification, since 100 nm-MPs penetrated cell membranes, disrupted reactive oxygen species balance, and reduced bacterial viability, thus suppressing microbial nitrogen degradation by 8.07 % (p < 0.05). Additionally, 100 nm-MPs significantly inhibited plant growth and reduced plant nitrogen uptake by 16.05 % (p < 0.05). Furthermore, 100 µm-MPs increased the abundance of nitrifiers but reduced denitrifiers and functional genes, whereas 100 nm-MPs reduced the abundance of both nitrifiers and denitrifiers along with their functional genes (p < 0.05). These findings highlight the need to improve waste management to mitigate the adverse effects of MPs on nitrogen removal.

Effects of low molecular weight organic acids on adsorption of Cd(II) by Auricularia auricula spent substrate-derived biochar: Types and reaction sequence

Cadmium (Cd) is one of the most mobile and toxic heavy metals that seriously deteriorates crop quality and threatens human health. It is considered an effective means to stabilize Cd in soil and reduce plant uptake by the application of biochar. However, the interactions and mechanisms between biochar and Cd in the rhizospheric soil are blurred due to the involvement of low molecular weight organic acids (LMWOAs). In this study, four different reaction sequences were established to simulate the chemical interactions between LMWOAs and cadmium (Cd) in the rhizospheric soil with biochar. In terms of adsorption patterns, the results show that, LMWOAs not only slow down the adsorption of Cd ions onto biochar, but also desorb the adsorbed Cd ions from biochar. Tartaric acid (TA) makes adsorption easier, while citric acid (CA) and malic acid (MA) make it more difficult. In terms of adsorption mechanism, the functional groups of MA and CA on biochar the vary wtih reaction sequence, thereby affecting the Cd adsorption onto biochar. The functional groups of TA participate in the adsorption to the greatest extent, and its impact on adsorption is rarely influenced by the reaction sequence. The reaction sequence does not affect the types of Cd-crystals, but affects dissolvement or attachment to the surface of biochar. This study provides chemical insights for further understanding the impact of LMWOAs on the interaction between biochar and heavy metals in soil.

A methodological framework for assessing sea level rise impacts on nitrate loading in coastal agricultural watersheds using SWAT+: A case study of the Tar-Pamlico River basin, North Carolina, USA

This study addresses the urgent need to understand the impacts of climate change on coastal ecosystems by demonstrating how to use the SWAT+ model to assess the effects of sea level rise (SLR) on agricultural nitrate export in a coastal watershed. Our framework for incorporating SLR in the SWAT+ model includes: (1) reclassifying current land uses to water for areas with elevations below 0.3 m based on SLR projections for mid-century; (2) creating new SLR-influenced land uses, SLR-influenced crop database, and hydrological response units for areas with elevations below 2.4 m; and (3) adjusting SWAT+ parameters for the SLR-influenced areas to simulate the effects of saltwater intrusion on processes such as plant yield and denitrification. We demonstrate this approach in the Tar-Pamlico River basin, a coastal watershed in eastern North Carolina, USA. We calibrated the model for monthly nitrate load at Washington, NC, achieving a Nash-Sutcliffe Efficiency (NSE) of 0.61. Our findings show that SLR substantially alters nitrate delivery to the estuary, with increased nitrate loads observed in all seasons. Higher load increases were noted in winter and spring due to elevated flows, while higher percentage increases occurred in summer and fall, attributed to reduced plant uptake and disrupted nitrogen cycle transformations. Overall, we observed an increase in mean annual nitrate loads from 155,000 kg NO3-N under baseline conditions to 157,000 kg NO3-N under SLR scenarios, confirmed by a statistically significant paired t-test (p = 2.16 × 10−10). This pioneering framework sets the stage for more sophisticated and accurate modeling of SLR impacts in diverse hydrological scenarios, offering a vital tool for hydrological modelers.

Growth Responses of Holcus lanatus L. (Velvet Grass) in Soils Contaminated with Cesium or Strontium

Radiocesium (r-Cs) and radiostrontium (r-Sr) released from nuclear accidents (e.g., Chornobyl, Fukushima) and routine operations (reactors, reprocessing) pose environmental and health concerns. Their primary pathway to humans is through plant uptake and subsequent bioaccumulation within the food chain. While soil amendments with potassium (K) and calcium (Ca) are known to mitigate r-Cs and r-Sr uptake, respectively, the impact on plant growth remains unclear. This study investigates the effects of Cs and Sr on the growth of Holcus lanatus L. seedlings under hydroponic and soil conditions with varying Cs and Sr concentrations. Stable isotopes of Cs and Sr served as non-radioactive analogs. Seedling growth was assessed across a range of Cs and Sr concentrations (≤1 and ≥4 mg L−1). The impact of the addition of K and Ca on Cs/Sr uptake in amended soils was also evaluated. Additionally, this study examined how Cs and Sr amendments affected the influx rates of other nutrients in H. lanatus. Higher Cs and Sr concentrations (≥4 mg L−1) significantly inhibited seedling growth, while lower concentrations had no effect. Notably, H. lanatus exhibited moderate Cs tolerance and strong Sr tolerance. Furthermore, K and Ca supplementation in Cs/Sr-amended soils demonstrably reduced plant uptake of these elements. This study also observed alterations in the uptake rates of other nutrients within H. lanatus due to Cs/Sr addition. This study suggests that H. lanatus exhibits moderate tolerance to Cs and Sr contamination, potentially making it suitable for revegetation efforts in contaminated grasslands. Additionally, K and Ca amendments show promise as a strategy to mitigate plant uptake of these radioisotopes further. These findings contribute to the development of safer revitalization strategies for areas impacted by nuclear accidents.

Field-aged rice hull biochar stimulated the methylation of mercury and altered the microbial community in a paddy soil under controlled redox condition changes

Mercury (Hg) contaminated paddy soils are hot spots for methylmercury (MeHg) which can enter the food chain via rice plants causing high risks for human health. Biochar can immobilize Hg and reduce plant uptake of MeHg. However, the effects of biochar on the microbial community and Hg (de)methylation under dynamic redox conditions in paddy soils are unclear. Therefore, we determined the microbial community in an Hg contaminated paddy soil non-treated and treated with rice hull biochar under controlled redox conditions (< 0 mV to 600 mV) using a biogeochemical microcosm system. Hg methylation exceeded demethylation in the biochar-treated soil. The aromatic hydrocarbon degraders Phenylobacterium and Novosphingobium provided electron donors stimulating Hg methylation. MeHg demethylation exceeded methylation in the non-treated soil and was associated with lower available organic matter. Actinobacteria were involved in MeHg demethylation and interlinked with nitrifying bacteria and nitrogen-fixing genus Hyphomicrobium. Microbial assemblages seem more important than single species in Hg transformation. For future directions, the demethylation potential of Hyphomicrobium assemblages and other nitrogen-fixing bacteria should be elucidated. Additionally, different organic matter inputs on paddy soils under constant and dynamic redox conditions could unravel the relationship between Hg (de)methylation, microbial carbon utilization and nitrogen cycling.

Effect of microplastics used in agronomic practices on agricultural soil properties and plant functions: Potential contribution to the circular economy of rural areas.

The extensive use of plastic materials and their improper disposal results in high amounts of plastic waste in the environment. Aging of plastics leads to their breakdown into smaller particles, such as microplastics (MPs) and nanoplastics. This research investigates plastics used in agricultural practices as they contribute to MP pollution in agricultural soils. The distribution and characteristics of MPs in agricultural soils were evaluated. In addition, the effect of MPs on soil properties, the relationship between MPs and metals in soil, the effect of MPs on the fate of pesticides in agricultural soils and the influence of MPs on plant growth were analysed, discussing legume, cereal and vegetable crops. Finally, a brief description of the main methods of chemical analysis and identification of MPs is presented. This study will contribute to a better understanding of MPs in agricultural soils and their effect on the soil-plant system. The changes induced by MPs in soil parameters can lead to potential benefits as it is possible to increase the availability of micronutrients and reduce plant uptake of toxic elements. Furthermore, although plastic pollution remains an emerging threat to soil ecosystems, their presence may result in benefits to agricultural soils, highlighting the principles of the circular economy.

Reduction of arsenic uptake in lentil through arbuscular mycorrhizal fungi

Arsenic (As) is a carcinogenic and hazardous substance that poses a serious risk to human health. The present research focused on the transport of As in seven lentil varieties developed by the Bangladesh Agricultural Research Institute (BARI) viz., BARI Mashur1, BARI Mashur 2, BARI Mashur 3, BARI Mashur 4, BARI Mashur 5, BARI Mashur 6 and BARI Mashur 7 and the role of arbuscular mycorrhizal fungi (AMFs) in mitigating As phyto-toxicity in them. The transportation of As from soil to root, shoot, and grain was lower after week 13 than in weeks 6 or 10 after lentil seedling emergence. The As accumulation in grains was higher in BARI Mashur 1 than in other test genotypes. Treatment with AMF significantly increased growth and biomass accumulation in lentil genotypes compared to non-AMF plants. Furthermore, AMF effectively reduced As concentrations in roots and shoots of lentil plants grown in 8 and 45 mg kg-1 As-contaminated soils. This study revealed a remarkable variation among the BARI-developed lentil genotypes in terms of As accumulation in plant parts. Treatment with AMF could effectively reduce plant uptake of As and mitigate As-induced phytotoxicity in lentils. The results reveal a great potential of AMF to mitigate As toxicity in lentils caused by the transport of As from soil to the shoot mass and reallocation to grains. This may enable farmers to expand lentil cultivation in As- affected areas throughout the world. Ann. Bangladesh Agric. (2023) 27 (1): 41-56

Hydrochar reduces oxytetracycline in soil and Chinese cabbage by altering soil properties, shifting microbial community structure and promoting microbial metabolism

The efficient remediation of antibiotic-contaminated soil is critical for agroecosystem and human health. Using the cost-effective and feedstock-independent hydrochar with rich oxygen-containing functional groups as a soil remediation material has become a hot concern nowadays. However, the feasibility and effectiveness of hydrochar amendment in antibiotic-contaminated soil still remain unknown. Therefore, this study investigated the remediation effect and potential mechanisms of different hydrochars from cow manure (H-CM), corn stalk (H-CS) and Myriophyllum aquaticum (H-MA) at two levels (0.5% and 1.0%) in oxytetracycline (OTC)-contaminated soil using a pot experiment. Results showed that compared with CK, OTC content in the soils amended with H-CM and H-MA was decreased by 14.02–15.43% and 9.23–24.98%, respectively, whereas it was increased by 37.03–42.64% in the soils amended with H-CS. Additionally, all hydrochar amendments effectively reduced the OTC uptake in root and shoot of Chinese cabbage by 10.41–57.99% and 31.92–65.99%, respectively. The response of soil microbial community to hydrochar amendment heavily depended on feedstock type rather than hydrochar level. The soil microbial metabolism (e.g., carbohydrate metabolism, amino acid metabolism) was enhanced by hydrochar amendment. The redundancy analysis suggested that TCA cycle was positively related to the abundances of OTC-degrading bacteria (Proteobacteria, Arthrobacter and Sphingomonas) in all hydrochar-amended soils. The hydrochar amendment accelerated the soil OTC removal and reduced plant uptake in soil-Chinese cabbage system by altering soil properties, enhancing OTC-degrading bacteria and promoting microbial metabolism. These findings demonstrated that the cost-effective and sustainable hydrochar was a promising remediation material for antibiotic-contaminated soil.

Tea biochar-immobilized Ralstonia Bcul-1 increases nitrate nitrogen content and reduces the bioavailability of cadmium and chromium in a fertilized vegetable soil

Pyrolytic biochar (PL-BC, pyrochar) and hydrothermal biochar (HT-BC, hydrochar) derived from branches and leaves of tea plants had different pH, electrical conductivity (EC), total carbon nitrogen content, BET surface area, total pore volume, average pore diameter, and functional groups. HT-BC had a larger specific surface area and more functional groups than PL-BC. Ralstonia Bcul-1 (R-B) was the dominant and functional bacteria in a fertilized vegetable soil supplemented with TBB-immobilized R-B (TBB + R-B). R-B vitality was more closely related to BET surface area, total pore volume, and functional groups of tea-based biochar (TBB: PL-BC and HT-BC). R-B was able to maintain high oxidase activity. R-B and TBB + R-B can increase the activities of urease and peroxidase in vegetable soil playing an essential role in the biotransformation of ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N). TBB was able to simultaneously increase the content of NO3−-N and NH4+-N, and TBB + R-B also significantly increased NO3−-N content but decreased NH4+-N content in a fertilized vegetable soil. These results indicated that R-B promoted nitrification in the soil, i.e. conversion of NH4+-N into NO3−-N, by enhancing the activities of urease and peroxidase. R-B had high adsorption capacity for cadmium (Cd) and chromium (Cr) (Cd&Cr: Cd and Cr). Moreover, TBB + R-B was able to convert weak acid extractable and reducible Cd&Cr into a more stable residual fraction and oxidizable Cd&Cr. The overall effect of the treatments was to reduce plant uptake of Cd&Cr by cabbage. TBB + R-B significantly promoted R-B growth, changed inorganic nitrogen speciation, increased NO3−-N supply, reduced Cd&Cr bioavailability, and decreased plant tissue Cd&Cr content.

Aridity shifts the difference in carbon uptake and storage between wooded and pure grasslands from positive to negative

Woody plant encroachment in arid grasslands may reduce plant uptake and soil storage of carbon (C) with consequences for the global C cycle, yet multi-site comparative studies have not been done so far and experiments are not feasible due to the long time needed for soil organic C (SOC) to accumulate. We selected multiple grassland sites with ≥50 % or 0 % woody plant aboveground biomass in each of six vegetation types representing a gradient of increasing aridity, resulting in a comparative study design with a total of 178 pure and 106 wooded grasslands distributed over the large geographic area of Xinjiang, China. Differences between wooded and pure grasslands in SOC stocks in the top 100 cm of the soil changed from positive to negative with increasing aridity. This effect was strongest in the upper soil layers, suggesting that woody plants had perhaps not been present for long enough to leave a signal in the lower soil layers. The differences in SOC stocks were related to differences in plant belowground standing C (BGC) and these to differences in yearly plant aboveground C uptake (ANPP) between wooded and pure grasslands. At more arid sites, wooded grasslands had lower ANPP and BGC because of reduced contributions of herbaceous plants that were not fully compensated by woody plants. Considering predicted increases in aridity in the study region, our results suggest that to avoid future losses of grassland SOC stocks — which are several ten times higher than the C stored in plant organs — management should try to prevent or reduce woody plant encroachment.

Effects of forest management on soil acidification in cedar plantation

Forest management practices such as clearcutting risk increasing the leaching loss of cations and soil acidification by increasing nitrification and reducing plant uptake. To evaluate the effect of two forest management practices, clearcutting and stem girdling, on soil acidification, we quantified proton budgets by measuring ion fluxes associated with solute leaching and plant uptake in a Japanese cedar plantation in Wakayama, Japan. In the control and girdling plots, the dissociation of organic acids was a major proton-generating process that promoted cation leaching from the organic horizon. Plant uptake of mobilized cations was a dominant soil-acidifying process in the control plot, whereas litterfall from tree dieback and loss of plant uptake led to soil alkalization via cation inputs to the mineral soil in the girdling plot. In the clearcut plot, in addition to cation removal due to harvesting, nitrification was a major proton-generating process that increased aluminum (Al) leaching in the first year following clearcutting. However, proton consumption via net mineralization (loss) of soil organic matter (SOM) could neutralize the acidity generated by nitrification. Forest management practices stimulate both proton-generating and -consuming processes. Soils under cedar plantation are affected by biological acidification of surface soil by plant uptake in the rooting zone and net cation leaching by carbonic acid below the rooting zone (subsoil and bedrock), but organic matter and Al and Fe oxides accumulated in plantation could mitigate acidification induced by disturbances.

Organic amendments for crop production, phosphorus bioavailability and heavy metal immobilisation: a review

Repeated and excessive use of inorganic phosphorus fertilisers adversely affects soil fertility, reduces plant phosphorus (P)-use efficiency, increases soil heavy metal concentrations and poses human health risks via food chain interaction. Organic amendments (OAs) are considered as cost-effective and environment-friendly supplement to inorganic P fertilisers that are produced from scarce phosphate rocks. Numerous studies have reported the synergistic and antagonistic effects of OAs on crop production, P solubility and availability, and immobilisation of heavy metals. However, the results of these studies are found to be variable and demand a critical review. This article summarises the environmental and health implications of continuous inorganic P fertilisers application along with a detailed overview of commonly available OAs and their efficacy to stimulate plant growth and yield. Moreover, this review describes the potentiality of OAs to increase the bioavailability of P in soil, discusses how and to what extent these soil amendments can immobilise heavy metals and reduce plant uptake, and finally provides future research directions for organic farming and sustainable agricultural practices.

Fate of endosulfan in ginseng farm and effect of granular biochar treatment on endosulfan accumulation in ginseng.

Endosulfan was widely used as an insecticide in the agricultural sector before its environmental persistence was fully understood. Although its fate and transport in the environment have been studied, the effects of historic endosulfan residues in soil and its bioaccumulation in crops are not well understood. This knowledge gap was addressed by investigating the dissipation and bioaccumulation of endosulfan in ginseng as a perennial crop in fresh and aged endosulfan-contaminated fields. In addition, the effect of granular biochar (GBC) treatment on the bioaccumulation factor (BAF) of endosulfan residue in ginseng was assessed. The 50% dissipation time (DT50) of the total endosulfan was over 770days in both the fresh and aged soils under mulching conditions. This was at least twofold greater than the reported (6- > 200days) in arable soil. Among the endosulfan congeners, the main contributor to the soil residue was endosulfan sulfate, as observed from 150days after treatment. The BAF for the 2-year-old ginseng was similar in the fresh (1.682-2.055) and aged (1.372-2.570) soils, whereas the BAF for the 3-year-old ginseng in the aged soil (1.087-1.137) was lower than that in the fresh soil (1.771-2.387). The treatment with 0.3 wt% GBC extended the DT50 of endosulfan in soil; however, this could successfully suppress endosulfan uptake, and reduced the BAFs by 66.5-67.7% in the freshly contaminated soil and 32.3-41.4% in the aged soil. Thus, this adsorbent treatment could be an effective, financially viable, and sustainable option to protect human health by reducing plant uptake of endosulfan from contaminated soils.

Reduced plant uptake of PAHs from soil amended with sunflower husk biochar

Biochar effect on the polycyclic aromatic hydrocarbons (PAHs) uptake by spring barley (Hordeum Sativum) was studied in model experiment conditions with Haplic Chernozem spiked by the high doses of benzo[a]pyrene (BaP) (400, 800 and 1200 µg kg-1), as the main marker of PAHs contamination. The relevance of the study is due to the BaP stability in natural environments and its carcinogenicity in relation to all living organisms. The express method of subcritical water extraction was used for BaP extraction from samples. The soil contamination by BaP contributed to the PAHs accumulation in soil and plants uptake from the polluted soil. It was found the 1% biochar application dose in the variant with 400 µg kg-1 contamination decreased the alone BaP and total PAHs content in soil and spring barley up to 50% compared to the contaminated variant. In soil contaminated with 800 µg kg-1 the 5% of biochar application led to the BaP content decreasing in the soil up to 56% and in the plants to 40-60%. Application of 5% biochar in the soil polluted with 1200 µg kg-1 led to the BaP and total PAHs content decreasing in soil up to 47% and 30%, respectively, plants the BaP content decreased up to 37-48%. Biochar 5% amendment effectiveness has been shown on the plants grown on the highly toxic variant contaminated with 1200 µg kg-1 BaP. The earing phase was inhibited in the spring barley plants growth at the most contaminated soil of the model experiment, whereas biochar application into the soil promoted the successful formation of the corn. The used biochar showed a high sorption capacity and its effectiveness under the soil remediation contaminated with BaP.

Exogenous application of Mn significantly increased Cd accumulation in the Cd/Zn hyperaccumulator Sedum alfredii.

Sedum alfredii is a Cd/Zn hyperaccumulator native to China, which was collected from a mined area where Mn content in soil was extremely high, together with Zn and Cd content. We investigated the tolerance and accumulation ability of Mn and its possible association with Cd hyperaccumulation in this plant species by using MP-AES, SR-μ-XRF, and RT-PCR. The results showed that the hyperaccumulating ecotype (HE) S.alfredii exhibited high tolerance to Mn and accumulating around 10,000 and 12,000mgkg-1 Mn in roots and shoots, respectively, without exhibiting toxicity under 5000mgkg-1 Mn treatment for 4 weeks. Exposure to Cd significantly reduced plant uptake of Mn. In contrast, exogenous Mn application significantly improved root uptake and root-to-shoot translocation of Cd, resulting in the increased Cd accumulation in the shoots of HE S.alfredii. SR-μ-XRF analysis demonstrated that high Mn (20μM) exposure resulted in higher intensities of Cd localized in both stem vascular bundles and cortex, as well as leaf mesophyll cells, than in those treated with low Mn levels (0.2μM or 2.0μM). RT-PCR analysis of several genes possibly involved in Mn/Cd transportation showed that expression of SaNramp3 in roots was significantly reduced under high Mn exposure. These results suggested a significant interaction between Cd and Mn in the HE S.alfredii plants, possibly through their competition for transporters and theoretically provided a strategy to improve the efficiency of Cd extraction from polluted soils by this plant species, after using appropriate nutrient management of Mn.

Immobilization and retention of caffeine in soil amended with Ulva reticulata biochar

The goal of the present study was to evaluate the immobilization and retention of caffeine (CFN) in soil and the influence of biochar for the CFN transport in agricultural soil. The biochar was produced from the Ulva reticulata seaweed biomass (ULBC) under the slow-pyrolysis with a heating rate of 7 °C/min at 500 °C and characterized using XRD and FTIR. The CFN retention and transport abilities in loamy sand and ULBC amended (2.5%) soil were evaluated under various pH values range of 3–10 and at various CFN concentrations using batch and column experiments. The surface orientation of ULBC was portrayed as the randomized distribution of hetero and homogeneous nature. The highest retention capacity (40 μg/g) was obtained at pH 4.0. Soil amendment with ULBC shows a higher retention affinity towards CFN, of up to 150 μg/g than soil, with minimal pH dependence. The maximum CFN adsorption capacities of soil and amended soils were 420 and 820 μg/g, respectively, based on the Langmuir model. Batch experiments suggested the adsorption of CFN by the biochar amended loamy soil is governed by the electrostatic attraction. The column experiment data demonstrated a high transport potential of CFN in the loamy sand; however, a strong cumulative reduction of transport (58%) was observed with the application of ULBC into the loamy sand. Thus, the addition of seaweed biochar as an amendment in soils with biosolids and wastewater irrigation may reduce the mobilization of CFN to the aquatic system and possibly reduce plant uptake.

Identification of reduced plant uptake and reduction effects of azoxystrobin, procymidone and tricyclazole by biochars and quicklime

Identification of reduced plant uptake and reduction effects of azoxystrobin, procymidone and tricyclazole by biochars and quicklime

Biochar Affects Heavy Metal Uptake in Plants through Interactions in the Rhizosphere

Heavy metals in soil pose a constant risk for animals and humans when entering their food chains, and limited means are available to reduce plant accumulation from more or less polluted soils. Biochar, which is made by pyrolysis of organic residues and sees increasing use as a soil amendment to mitigate anthropogenic C emissions and improve agronomic soil properties, has also been shown to reduce plant availability of heavy metals in soils. The cause for the reduction of metal uptake in plants when grown in soils enriched with biochar has generally been researched in terms of increased pH and alkalinity, while other potential mechanisms have been less studied. We conducted a pot experiment with barley using three soils differing in metal content and amended or not with 2% biochar made from Miscanthus x giganteus, and assessed plant contents and changes in bioavailability in bulk and rhizosphere soil by measuring extractability in acetic acid or ammonium nitrate. In spite of negligible pH changes upon biochar amendment, the results showed that biochar reduced extractability of Cu, Pb and Zn, but not of Cd. Rhizosphere soil contained more easily extractable Cu, Pb and Zn than bulk soil, while for Cd it did not. Generally, reduced plant uptake due to biochar was reflected in the amounts of metals extractable with ammonium nitrate, but not acetic acid.

Impact of biochar amendment on the uptake, fate and bioavailability of pharmaceuticals in soil-radish systems

Crops grown in soils receiving wastewaters, biosolids, or manures can accumulate pharmaceuticals in edible parts, raising concerns over potential human exposure to multiple pharmaceuticals. Nonetheless, viable mitigation options for minimizing plant uptake of pharmaceuticals are limited. This study evaluated how biochar amendment could influence the uptake of 15 pharmaceuticals by radish (Raphanus sativus) grown in a sandy loam at two amendment rates (0.1 and 1% w/w). Comparing with that in the unamended soil, the accumulation of acetaminophen, carbamazepine, sulfadiazine, sulfamethoxazole, lamotrigine, carbadox, trimethoprim, oxytetracycline, tylosin, estrone, and triclosan in radish grown in the soil amended with 1.0% of biochar was significantly decreased by 33.3–83.0%. However, the concentration of lincomycin in radish was increased by 36.7–48.2% in the soil amended with 1% biochar. While the soil amended with 1.0% of biochar had increased sorption of all 15 pharmaceuticals, the persistence of 7 pharmaceuticals in the soil were prolonged, including caffeine, sulfadiazine, sulfamethoxazole, lincomycin, estrone, 17 β-estradiol and triclosan. The reduced plant uptake of pharmaceuticals was mainly due to their lowered concentrations in pore water by the presence of biochar. Overall, the estimated daily intake data suggest that biochar amendment could potentially decrease total human exposure to a mixture of pharmaceuticals.

Popular wood and sugarcane bagasse biochars reduced uptake of chromium and lead by lettuce from mine-contaminated soil

As a result of metal mining activities in Pakistan, toxic heavy metals (HMs) such as chromium (Cr) and lead (Pb) often enter the soil ecosystem, accumulate in food crops and cause serious human health and environmental issues. Therefore, this study examined the efficacy of biochar for contaminated soil remediation. Poplar wood biochar (PWB) and sugarcane bagasse biochar (SCBB) were amended to mine-contaminated agricultural soil at 3% and 7% (wt/wt) application rates. Lactuca sativa (Lettuce) was cultivated in these soils in a greenhouse, and uptake of HMs (Cr and Pb) as well as biomass produced were measured. Subsequently, health risks were estimated from uptake data. When amended at 7%, both biochars significantly (P<0.01) reduced plant uptake of Cr and Pb in amended soil with significant (P<0.01) increase in biomass of lettuce as compared to the control. Risk assessment results showed that both biochars decreased the daily intake of metals (DIM) and associated health risk due to consumption of lettuce as compared to the control. The Pb human health risk index (HRI) for adults and children significantly (P<0.01) decreased with sugarcane bagasse biochar applied at 7% rate relative to other treatments (including the control). Relative to controls, the SCBB and PWB reduced Cr and Pb uptake in lettuce by 69%, 73.7%, respectively, and Pb by 57% and 47.4%, respectively. For both amendments, HRI values for Cr were within safe limits for adults and children. HRI values for Pb were not within safe limits except for the sugarcane bagasse biochar applied at 7%. Results of the study indicated that application of SCBB at 7% rate to mine impacted agricultural soil effectively increased plant biomass and reduced bioaccumulation, DIM and associated HRI of Cr and Pb as compared to other treatments and the control.