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Long-term intensive use of mineral fertilizers in double rice-cropping systems has led to soil acidification and soil degradation. Manure fertilization was suggested as an alternative strategy to mitigate soil degradation. However, the effects of long-term mineral and manure fertilization on rice grain yield, yield stability, soil organic carbon (SOC) content, soil total nitrogen (TN) content, and the underlying mechanisms are unclear. Based on a long-term experiment established in 1981 in southern China, we compared four treatments: no fertilizer application (Control); application of nitrogen–phosphorus–potassium (NPK); NPK plus green manure in early rice (M1); and M1 plus farmyard manure in late rice and rice straw return in winter (M2). Our results showed that 37 years of NPK, M1, and M2 significantly increased rice grain yield by 54%, 46%, and 72%, and yield stability by 22%, 17%, and 9%, respectively. M1 and M2 significantly increased SOC content by 39% and 23% compared to Control, respectively, whereas there was no difference between Control and NPK. Regarding soil TN content, it was significantly increased by 8%, 46%, and 20% by NPK, M1, and M2, respectively. In addition, M2 significantly increased bacterial OTU richness by 68%, Chao1 index by 79%, and altered the bacterial community composition. Changes in soil nutrient availability and bacterial Simpson index were positively correlated with the changes in grain yield, while shifts in bacterial community were closely related to yield stability. This study provides pioneer comprehensive assessments of the simultaneous responses of grain yield, yield stability, SOC and TN content, nutrient availability, and bacterial community composition to long-term mineral and manure fertilization in a double rice-cropping system. Altogether, this study spanning nearly four decades provides new perspectives for developing sustainable yet intensive rice cultivation to meet growing global demands. [ABSTRACT FROM AUTHOR]

The use of advanced treatment technologies such as pyrolysis and carbonization of bio-waste materials has the promise to develop coupled solutions for organic C and P problems in the future of food processing. Sewage sludge-derived pyrogenic materials that are applied to the soil system contain notable levels of P (1–20%). However, only a small portion of total phosphorus is available for plants. Therefore, our study assessed the pretreatment of sewage sludge with Na2CO3 and subsequent pyrolysis at 400 °C and 500 °C for the production of MPCM400 and MPCM500 as potential alternatives for inorganic P fertilizers. Non-pretreated sewage sludge-derived pyrogenic carbonaceous materials (PCM400 and PCM500) were produced as controls. The derived materials obtained by slow pyrolysis at a residence time of 120 min and pyrolysis temperatures of 400 °C and 500 °C, were analyzed by determination of electrical conductivity (EC), pH, elemental analysis of total C, H, N, scanning electron microscopy (SEM) and total concentrations of P, Cd, Fe, Pb and Zn. PCM400, PCM500, MPCM400 and MPCM500 were characterized by analysis of total 16 US-EPA (U.S. Environmental Protection Agency) PAHs by a toluene extraction procedure. Additionally, PCM400, PCM500, MPCM400 and MPCM500 were tested by a germination test with cress seeds (Lepidium sativum L.) and a short-term rye seedling test. Total C concentrations were raised in the order: MPCM500 < MPCM400 < PCM500 < PCM500. Concentration of Σ16 US-EPA PAHs was almost five times higher at PCM500 (21.87 mg/kg) compared to PCM400 (4.38 mg/kg) and three times higher at MPCM500 (23.12 mg/kg) compared to MPCM400 (7.55 mg/kg) with a dominant role of two and three-ring aromatic structures. Total P-concentrations in rye biomass increased in the order for the controls: (2.43 ± 0.95 mg/g) < PCM400 (3.57 ± 0.27 mg/g) < PCM500 (4.04 ± 0.24 mg/g) < MPCM400 (5.23 ± 0.09 mg/g) < MPCM500 (5.57 ± 0.70 mg/g) < IF (7.53 ± 2.65 mg/g). Obtained results showed that pyrolysis materials produced from sewage sludge represent a potential alternative of conventional P inorganic fertilizers and organic C suppliers. [ABSTRACT FROM AUTHOR]

Although the suitability of some biochars for contaminants' sorption separation has been established, not all potential feedstocks have been explored and characterized. Here, we physicochemically characterized cherry pit biochar (CPB) pyrolyzed from cherry pit biomass (CP) at 500 °C, and we assessed their As and Hg sorption efficiencies in aqueous solutions in comparison to activated carbon (AC). The basic physicochemical and material characterization of the studied adsorbents was carried out using pH, electrical conductivity (EC), cation exchange capacity (CEC), concentration of surface functional groups (Boehm titration), and surface area (SA) analysis; elemental C, H, N analysis; and Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX). AsO43− anions and Hg2+ cations were selected as model contaminants used to test the sorption properties of the sorption materials. Characterization analyses confirmed a ninefold increase in SA in the case of CPB. The total C concentration increased by 26%, while decreases in the total H and N concentrations were observed. The values of carbonate and ash contents decreased by about half due to pyrolysis processes. The concentrations of surface functional groups of the analyzed biochar obtained by Boehm titration confirmed a decrease in carboxyl and lactone groups, while an increase in phenolic functional groups was observed. Changes in the morphology and surface functionality of the pyrolyzed material were confirmed by SEM–EDX and FTIR analyses. In sorption experiments, we found that the CPB showed better results in the sorption separation of Hg2+ than in the sorption separation of AsO43−. The sorption efficiency for the model cation increased in the order CP < CPB < AC and, for the model anion, it increased in the order CPB < CP < AC. [ABSTRACT FROM AUTHOR]

Elevated or unnatural levels of arsenic (As) and phosphorus (P) concentrations in soils and waterbodies from anthropogenic sources can present significant hazards for both natural ecosystems and human food production. Effective, environmentally friendly, and inexpensive materials, such as biochar, are needed to reduce mobility and bioavailability of As and P. While biochar features several physicochemical properties that make it an ideal contaminant sorbent, certain modifications such as mineral-impregnation can improve sorption efficiencies for targeted compounds. Here, we conducted sorption experiments to investigate and quantify the potential utility of magnesium (Mg) for improving biochar sorption efficiency of P and As. We synthesized a Mg-modified walnut shells-derived biochar and characterized its ability to remove As and P from aqueous solutions, thereby mitigating losses of valuable P when needed while, at the same time, immobilizing hazardous As in ecosystems. SEM-EDX, FTIR and elemental analysis showed morphological and functional changes of biochar and the formation of new Mg-based composites (MgO, MgOHCl) responsible for improved sorption potential capacity by 10 times for As and 20 times for P. Sorption efficiency was attributed to improved AEC, higher SSA, chemical forms of sorbates and new sorption site formations. Synthetized Mg-composite/walnut shell-derived biochar also removed >90% of P from real samples of wastewater, indicating its potential suitability for contaminated waterbody remediation. [ABSTRACT FROM AUTHOR]

Harmful algal blooms have increased globally with warming of aquatic environments and increased eutrophication. Proliferation of cyanobacteria (blue-green algae) and the subsequent flux of toxic extracellular microcystins present threats to public and ecosystem health and challenges for remediation and management. Although methods exist, there is currently a need for more environmentally friendly and economically and technologically feasible sorbents. Biochar has been proposed in this regard because of its high porosity, chemical stability, and notable sorption efficiency for removing of cyanotoxins. In light of worsening cyanobacterial blooms and recent research advances, this review provides a timely assessment of microcystin removal strategies focusing on the most pertinent chemical and physical sorbent properties responsible for effective removal of various pollutants from wastewater, liquid wastes, and aqueous solutions. The pyrolysis process is then evaluated for the first time as a method for sorbent production for microcystin removal, considering the suitability and sorption efficiencies of pyrolysed materials and biochar. Inefficiencies and high costs of conventional methods can be avoided through the use of pyrolysis. The significant potential of biochar for microcystin removal is determined by feedstock type, pyrolysis conditions, and the physiochemical properties produced. This review informs future research and development of pyrolysed materials for the treatment of microcystin contaminated aquatic environments. [ABSTRACT FROM AUTHOR]