Potential of organic and inorganic amendments for stabilizing nickel in acidic soil, and improving the nutritional quality of spinach.

Rice straw, biochar and calcite incorporation enhance nickel (Ni) immobilization in contaminated soil and Ni removal capacity.

Rice straw (RS), biochar (BC) and lime (LM) have proved to be effective immobilizing agents in acidic contaminated soil. Up-to-date scientific data is lacking regarding residual effects of these amendments in acidic soils and wheat/rice cropping system. The objective was to analyze the efficacy of amendments to improve grain yields, nutritional quality, and reduce Ni bioavailability of wheat/rice rotation system. A pot experiment was conducted to examine the efficacy of RS, BC 10 and 20 g kg−1 and LM 10 g kg−1 application rates on plant growth, nutritional quality and Ni contents in wheat and rice tissues and grain. Amendments enhanced Ni immobilization, declined their uptake by plants and accumulation in the grains of both crops. Rice straw biochar reduced several factors like health risk assessment, Ni uptake and bioconcentration factor. BC 20 g kg−1 increased shoot, root and grain yields, while enhanced essential nutrients in the wheat/rice cropping system compared to untreated soil. Soil amendments significantly decreased toxicity characteristics leaching procedure (TCLP) extractable Ni by 42.25% and 42.62% and simple bioaccessibility extraction test (SBET) by 42.1% and 45.25% in post- wheat/rice crops. This process enhanced the safety of wheat/rice rotation cropping system to be consumed and mitigated security risks.

作物殘體經由燃燒後所產生之含炭物質，具有比表面積高、不易分解及良好的陰、陽離子交換容量，若施用於土壤中將會對於土壤基本性質、重金屬的移動和有機分子傳輸等具有影響。鉻在環境中主要以三價鉻﹝Cr(III)﹞及六價鉻﹝Cr(VI)﹞的形態存在，其中Cr(VI)的毒性和移動性都高於Cr(III)。現今受鉻污染之土壤常用的整治方法為添加化學還原劑(如，硫化鐵、亞鐵離子和零價鐵)將Cr(VI)還原為Cr(III)，近年已有研究藉由添加炭化之生物性資材還原Cr(VI)，然而土壤環境中存在許多變因，舉如土壤pH、有機質、氧化物及陰陽離子等，皆會影響炭化之生物性資材還原Cr(VI)之能力，因此本研究目的為探討添加稻稈生質炭(Rice-straw biochar; RB)到土壤中對土壤固定Cr(VI)之影響。 本研究選用兩種土壤，分別為陳厝寮系土壤(Chentsuo; Ce)(台中縣大肚鄉)及萬合系土壤(Wanho; Wa)(彰化縣埤頭鄉)，並添加5%的稻稈生質炭，以固液比為50 g L-1添加稻稈生質炭的土壤與10 mg L-1Cr(VI)溶液於pH 2.0-7.0以及未調整pH的環境中進行動力學反應。等溫吸附結果顯示，添加稻稈生質炭與否的陳厝寮和萬合系土壤在未調整pH的且低濃度Cr(VI)時，稻稈生質炭所固定的Cr(VI)佔土壤總固定量較大，顯示在低濃度的Cr(VI)污染情況時，土壤對於Cr(VI)的固定能力較佳。於動力學及土壤溶液中可溶性有機碳結果顯示，隨著溶液pH增加，陳厝寮及萬合系土壤對於Cr(VI)之固定和還原量隨之下降，可溶性有機碳濃度亦有上升趨勢。當溶液pH 7.0時，Cr(VI)仍有被還原的現象發生，表示可溶性有機碳將Cr(VI)還原為Cr(III)。當pH NO3- ≅ SO42- > Cl-。未來於土壤添稻稈生質炭若應用於低濃度Cr(VI)污染之土壤復育，對於Cr(VI)的固定和還原量是有影響性的。

Soil contamination with heavy metals, such as Cd and Pb, has caused severe health and environmental risks all over the world. Possible eco-friendly solutions for Cd and Pb immobilization were required to reduce its mobility through various cost-effective amendments. A laboratory incubation study was conducted to assess the efficiency of biochar (BC), zeolite (ZE), and rock phosphate (RP) as passivators for the stabilization of Cd and Pb in paddy soil as well as soil microbial biomass. Various extraction techniques were carried out: a sequential extraction procedure, the European Community Bureau of Reference (BCR), toxicity characteristic leaching procedure (TCLP) test, and single extraction with CaCl2. The impact of passivators on soil pH, dissolved organic carbon (DOC), and microbial biomass (carbon, nitrogen, and phosphorus) was examined in the metal contaminated soil. The results showed that the exchangeable portion of Cd in soil was significantly reduced by 34.8, 21.6, and 18.8% with ZE, RP, and BC at a 3% application rate, respectively. A similar tendency of reduction in Pb soluble portion was observed by ZE (9.6%), RP (20%), and BC (21.4%) at a 3% application rate. Moreover, the TCLP leachate of Cd and Pb was apparently reduced by 17 and 30.3% with BC at a 3% application dose, respectively, when compared to the control. Soil pH, nutrients, and microbial biomass C, N, and P were significantly increased with the addition of BC, RP, and ZE passivators. The results showed that the incorporation of BC, ZE, and RP significantly reduced the Cd and Pb mobility in paddy soil as well as enhanced soil nutrients and microbial biomass. Overall, among all the amendments, rice straw derived-BC performed better for Cd and Pb immobilization in paddy soil.

Effect of bamboo and rice straw biochars on the bioavailability of Cd, Cu, Pb and Zn to Sedum plumbizincicola

Effect of rice straw, biochar and calcite on maize plant and Ni bio-availability in acidic Ni contaminated soil

Two field experiments were raised at Farm of El-Sirw Agriculture Research Station, Dammitta province, Egypt through 2018 and 2019 seasons. The present study was performed to compromise the influence of rice straw biochar and other two soil amendments of rice straw compost and gypsum on rice growth and yield of three contrasting rice varieties,Giza177 (salt sensitive variety), Giza 178 (salt tolerant variety) and Giza179 new (salt tolerant variety) under saline sodic soil. The field experiments were designed in spilt plot design with four replications. The three rice varieties were scattered in the main plot, whereas the amendment treatments; control, gypsum(G), rice straw compost (RS) and rice straw biochar (RSB) were put in the subplots. The tested rice varieties were significantly different in growth parameters, yield attributes and yields in both seasons. Giza 179 as a new salt tolerant variety provided the maximum values of rice growth characteristics and most of yield contributes and yields without significant difference with Giza178 were considering yields. Applying varying soil amendments greatly improved rice growth and yields in addition to yield attributes comparing to the control treatments. Rice straw biochar surpassed significantly other two amendments, particularly in the first season, meanwhile in the second seasonthe three soil amendments were equally in increasing grain yield. Thereby, rice straw biochar could be applied each two years but rice straw compost has to apply in two successive season to get its efficiency. Two field experiments were raised at Farm of El-Sirw Agriculture Research Station, Dammitta province, Egypt through 2018 and 2019 seasons. The present study was performed to compromise the influence of rice straw biochar and other two soil amendments of rice straw compost and gypsum on rice growth and yield of three contrasting rice varieties,Giza177 (salt sensitive variety), Giza 178 (salt tolerant variety) and Giza179 new (salt tolerant variety) under saline sodic soil. The field experiments were designed in spilt plot design with four replications. The three rice varieties were scattered in the main plot, whereas the amendment treatments; control, gypsum(G), rice straw compost (RS) and rice straw biochar (RSB) were put in the subplots. The tested rice varieties were significantly different in growth parameters, yield attributes and yields in both seasons. Giza 179 as a new salt tolerant variety provided the maximum values of rice growth characteristics and most of yield contributes and yields without significant difference with Giza178 were considering yields. Applying varying soil amendments greatly improved rice growth and yields in addition to yield attributes comparing to the control treatments. Rice straw biochar surpassed significantly other two amendments, particularly in the first season, meanwhile in the second seasonthe three soil amendments were equally in increasing grain yield. Thereby, rice straw biochar could be applied each two years but rice straw compost has to apply in two successive season to get its efficiency.

Biochar (BC) continues to gain considerable interest for remediating metal-contaminated soils. A laboratory incubation study was conducted to evaluate the comparative efficiency of rapeseed residue and rice straw BCs pyrolyzed at 300°C and 550°C for lead (Pb) and copper (Cu) immobilization in naturally contaminated soil, which was not reported earlier. X-ray diffraction, scanning electron microscopy, and fourier-transform infrared (FT-IR) analysis were performed to study the nature of the BCs. Effectiveness of the amendments for Pb and Cu immobilization was assessed using a modified community bureau of reference extraction procedure, single extraction with CaCl 2 , and the toxicity characteristic leaching procedure, respectively. Amending the soil with RS550 significantly decreased the acid-extractable portions of Pb and Cu by 63.30% and 66%, respectively, whereas the residual (stable) fractions of Pb and Cu were increased by 40.31% and 52.98%, respectively. Immobilized metals were mainly transformed to the reducible fractions. High reductions in the bioavailable phase of Pb (97.13%) and Cu (93.71%) were recorded, while Pb and Cu solubility were reduced by 92.62% and Cu 72.55%, respectively. Affinity of BCs toward Pb and Cu was enhanced due to the increased negativity with increasing pH, as described by zeta potential and cation exchange capacity, which is one of the mechanisms of Pb and Cu immobilization. BCs produced at high temperature efficiently immobilized Pb and Cu compared to low-temperature BCs. These findings suggested that rapeseed residue and rice straw BCs could be used as Pb and Cu stabilizers in contaminated agricultural soils.

In order to understand the resource utilization of plant biomass, five types of biomass materials were used to produce biochar to treat wastewater containing phosphorus. The phosphorus adsorption capacity of five materials was preliminarily compared through laboratory experiments, and two materials with strong phosphorus adsorption capacity were screened out. The physicochemical characteristics of the selected biochar were analyzed using scanning electron microscopy and a BET specific surface area analyzer, and the effects of different pH values on phosphorus adsorption of the biochar were investigated. Furthermore, the phosphorus adsorption characteristics of the selected biochar were analyzed via isothermal adsorption and adsorption kinetics models. The results showed that among the five biochar materials, only rice straw and corn straw biochar had the ability to adsorb phosphorus. The Langmuir isothermal adsorption curve showed that the adsorption capacity of rice straw biochar for phosphorus in wastewater was stronger than that of corn straw biochar, and the theoretical maximum adsorption capacity was as follows:rice straw biochar (9.78 mg·g-1)>corn straw biochar (0.39 mg·g-1). The specific surface area (148.30 m2·g-1) and total pore volume (0.11 cm3·g-1) of rice straw biochar were much higher than those of corn straw biochar (8.26 m2·g-1 and 0.03 cm3·g-1, respectively), and the contents of Mg, Ca, Fe, and Al were higher in rice straw biochar. The best pH for phosphorus adsorption of rice straw biochar and corn straw biochar was acidic. In different pH ranges (3.0-11.0), the phosphorus adsorption capacity of rice straw and corn straw biochar decreased with the increase in pH. These results indicated that rice straw biochar has strong phosphorus adsorption capacity and has a better application prospect in wastewater treatment.

Biochar is a carbon-rich solid material derived from the pyrolysis of agricultural and forest residual biomass. Previous studies have shown that biochar is suitable as an adsorbent for soil contaminants such as heavy metals and consequently reduces their bioavailability. However, the long-term effect of different biochars on metal extractability or soil health has not been assessed. Therefore, a 1-year incubation experiment was carried out to investigate the effect of biochar produced from bamboo and rice straw (at temperatures ≥500 °C) on the heavy metal (cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn)) extractability and enzyme activity (urease, catalase, and acid phosphatase) in a contaminated sandy loam paddy soil. Three rates (0, 1, and 5%) and two mesh sizes (<0.25 and <1 mm) of biochar applications were investigated. After incubation, the physicochemical properties, extractable heavy metals, available phosphorus, and enzyme activity of soil samples were analyzed. The results demonstrated that rice straw biochar significantly (P < 0.05) increased the pH, electrical conductivity, and cation exchange capacity of the soil, especially at the 5% application rate. Both bamboo and rice straw biochar significantly (P < 0.05) decreased the concentration of CaCl2-extractable heavy metals as biochar application rate increased. The heavy metal extractability was significantly (P < 0.01) correlated with pH, water-soluble organic carbon, and available phosphorus in soil. The 5% application rate of fine rice straw biochar resulted in the greatest reductions of extractable Cu and Zn, 97.3 and 62.2%, respectively. Both bamboo and rice straw biochar were more effective at decreasing extractable Cu and Pb than removing extractable Cd and Zn from the soil. Urease activity increased by 143 and 107% after the addition of 5% coarse and fine rice straw biochars, respectively. Both bamboo and rice straw biochars significantly (P < 0.05) increased catalase activity but had no significant impact on acid phosphatase activity. In conclusion, the rice straw biochar had greater potential as an amendment for reducing the bioavailability of heavy metals in soil than that of the bamboo biochar. The impact of biochar treatment on heavy metal extractability and enzyme activity varied with the biochar type, application rate, and particle size.

Cadmium mobility, uptake and anti-oxidative response of water spinach (Ipomoea aquatic) under rice straw biochar, zeolite and rock phosphate as amendments

Effect of amendment of biochar supplemented with Si on Cd mobility and rice uptake over three rice growing seasons in an acidic Cd-tainted paddy from central South China

The presence of Ni above the permissible limit in agriculture soils poses negative effects on soil health, crop quality, and crop productivity. Surprisingly, the usage of various organic and inorganic amendments can reduce Ni mobility in the soil and its distribution in the crops. A pot experiment was conducted to elucidate the effects of olive pulp biochar (BR), calcite (CAL), and wheat straw (WS), as sole amendments and their mixtures of 50:50 ratio, added to Ni polluted soil on Ni mobility in the soil, Ni immobilization index (Ni − IMi), soil enzymatic activities, Ni distribution in parts of chili plant, Ni translocation factor and bioaccumulation factor in fruit, plant growth parameters and oxidative stress encountered by the plants. Outcomes of this pot experiment revealed that amendments raised soil pH, improved soil enzymatic activities, values of Ni − IMi, while significantly reduced bioavailable Ni fraction in the post-harvest soil. However, the highest activities of acid phosphatase, urease, catalase, and dehydrogenase by 50, 70, 239, and 111%, respectively, improvement in Ni − IMi up to 60% while 60% reduction in the bioavailable Ni fraction was observed in BR + CAL treatment, compared to control was noted. Among all amendments, the top most reduction in Ni concentrations in shoots, roots, fruit, Translocation Factor (TF), and Bioaccumulation Factor (BAF) values of fruit by 72%, 36%, 86%, 72%, and 86%, in BR + CAL treatment, compared to control. Moreover, the plants growing on BR + CAL amended Ni contaminated soil showed the topmost improvement in plant phonological parameters while encountered the least oxidative stress. Such findings refer to the prospective usage of BR + CAL at 50:50 ratio than BR, CAL, WS alone, and BR + WS as well as WS + CAL for reducing Ni mobility in the soil, improving Ni − IMi, soil enzymatic activities, plant phonological and oxidative stress while reducing Ni distribution in plant parts. Novelty statement In this experiment, it was hypothesized that amending Ni polluted soil with olive pulp biochar (BR), CAL, and WS as alone soil amendments and their combinations at 50:50 ratios can reduce Ni bioavailability in soil, Ni distribution in chili plant and oxidative stress encountered by the plants. Moreover, these amendments may improve, soil enzymatic activities, Ni immobilization index, plant phenological traits. Therefore, it was aimed to undertake useful scientific planning and research, to restore and rehabilitate the dwellings, biological resources and to minimize the sufferings of the peoples in nutrient-poor Ni contaminated soils, by improving soil health and chili productivity.

Novel thiol-grafted composite of chitosan and rice straw biochar (TH@CT-BC): A two-step fabrication for highly selective adsorption of cadmium from contaminated water

In the present study, efficiency of different biochars (BCs) on cadmium (Cd) immobilization and its bioavailability to spinach were investigated. In the first experiment, Cd-spiked soil was amended with treatments (T1 = control, T2 and T3 = cotton stalk biochar (CBC) 2% and 5%, T4 and T5 = rice straw biochar 2% and 5%) and incubated for 120 days. In the second experiment, spinach was grown in pots using three soils (a normal soil, a Cd-spiked soil, and a sewage-irrigated soil) after application of CBC and rice straw biochar (RBC) (2% w/w each) in each soil. In the field experiments, spinach was grown at two sites with six treatments including T0 = control, T1 and T2 (RBC 5 and 10 ton ha−1), T3 and T4 (CBC 5 and 10 ton ha−1). The results of our experiments showed a significant impact of BCs on soil pH, EC, soil organic matter, and Cd bioavailability. The plant growth parameters were also influenced positively by application of BC in both pot and field experiments. In field experiments, plant population and fresh biomass at different sites varied significantly. The Cd concentration in plants was lower when grown in treated soils. Moreover, there was a significant increase in soluble Si and phosphorus concentrations in plants and this had significant correlation with Cd concentration in plants.