The aims of this study were to investigate the effectiveness of fermented horse manure (HM) over vermicompost (VC), bamboo biochar (BB), and fly ash (FA) in suppressing Cd accumulation in rice plants and further to elucidate the underlying mechanisms of HM. Greenhouse experiments were conducted to determine the Cd concentration in rice tissues after the application of amendments to different Cd-contaminated soils. Chemical properties of root Fe plaque and pore water were also determined, including the amount of Fe in Fe plaque, and the changes in redox potential (Eh) and concentration of Cd and Fe in pore water with cultivation time. The results showed that HM was the most effective of all amendments in suppressing Cd accumulation in rice (by at least 57%), and the effect increased with the application rate. Furthermore, the application of HM can decrease the concentration of Cd in soil pore water and promote the formation of root Fe plaque (a barrier to prevent Cd uptake by rice plants) by decreasing the Eh and increasing the Fe concentration in pore water. The decrease in Cd concentration in soil pore water and the increase in root Fe plaque were the main reasons for the considerable reduction in the uptake and accumulation of Cd in rice plants by HM.

Two soils with explosives and metals were evaluated for the degradation efficiency of explosives by native microorganisms under anaerobic conditions. The commercially available method Daramend®, amended with zero-valent iron (ZVI), was compared with a horse-manure-amended compost and a treatment with ZVI alone. In a moderately contaminated soil, Daramend® and ZVI treatment gave significantly higher removal rates compared to compost and control treatments (Tukey's test, P < 0.05). The largest overall decrease in ecotoxicity, measured with bioluminescent bacteria (Vibrio fischeri), was achieved with ZVI treatment. In a more contaminated soil, no degradation of contaminants and no decline in soil toxicity could be distinguished after the same time period. Problems with establishment of anaerobic conditions during parts of the remediation process and low microbial activity due to acute toxicity of contaminants are plausible explanations. Redistribution that could potentially lead to mobilization of the co-contaminant Pb was not observed in either of the soils during the biological treatments.

Hydrothermal carbonization (HTC) is an energy-efficient thermochemical process for converting wet waste products into value added materials for water treatment. Understanding how HTC influences the physicochemical properties of the resultant materials is critical in optimizing the process for water treatment, where surface functionality and surface area play a major role. In this study, we have examined the HTC of four wet waste streams, sewage sludge, biosludge, fiber sludge, and horse manure at three different temperatures (180 °C, 220 °C, and 260 °C). The physicochemical properties of these materials were examined via FTIR, SEM and BET with their adsorption capacity were assessed using methylene blue. The yield of solid material after hydrothermal carbonization (hydrochar) decreased with increasing temperature for all samples, with the largest impact on horse manure and fiber sludge. These materials also lost the highest degree of oxygen, while HTC had minimal impact on biosludge and sewage sludge. The differences here were due to the varying compositions of each waste material, FTIR identified resonances related to cellulose in horse manure and fiber sludge, which were not detected in biosludge and sewage sludge. Adsorption capacities varied between 9.0 and 68 mg g⁻¹ with biosludge HTC at 220 °C adsorbing the highest amount. Adsorption also dropped drastically at the highest temperature (260 °C), indicating a correlation between adsorption capacity and HTC conditions. This was attributed to the loss of oxygen functional groups, which can contribute to adsorption. These results suggest that adsorption properties can be tailored both by selection of HTC temperature and feedstock.

Large areas of soils in China are contaminated with Cd and are deficient in Se. Therefore, here, we aimed to reduce Cd accumulation while increasing Se content in rice grain, and to elucidate the mechanisms associated. A greenhouse pot experiment was conducted to determine grain concentrations of Se and Cd upon foliar spraying of Se combined with the application of horse manure and/or fly ash to different contaminated soils containing Cd 0.51 (T1), 1.46 (T2), and 4.59 mg Cd kg⁻¹ (T3). The amount of Fe, Si, and Cd in root iron plaque, and concentrations of Cd and Si in rice tissues were also determined. Foliar spray of Se increased Se concentration in brown rice from approximately 0.04 to 0.15 mg kg⁻¹. Fly ash significantly reduced Cd concentration in brown rice from 0.07 to 0.05, 0.15 to 0.09, and 1.00 to 0.55 mg kg⁻¹ at the T1, T2, and T3 treatment levels, respectively, and soil Cd bioavailability (by at least 33.3%), while it increased Si content in rice roots and shoots by at least 34%. The increase of Si concentration in rice tissues inhibited Cd translocation to brown rice by at least 17%. Horse manure increased the formation of root Fe plaque by approximately 2.3-fold, which resulted in the significant reduction of Cd accumulation in brown rice, shoots, and roots by 36–56%. Thus, foliar spray of Se in combination with the application of fly ash and horse manure proved an effective method to produce Cd-low and Se-rich rice.

PURPOSE: This study evaluates manure and chemical fertilizer effects on micronutrient (Fe, Mn, Cu, and Zn) content and availability in crops. METHODS: Seven treatments were selected, including three conventional fertilization treatments (NP, horse manure (M), and NP plus M (NPM)), three corresponding double rate fertilization (N2P2, M2, and N2P2M2), and a CK. Soil samples were collected and separated into four aggregates by wet-sieving in September 2009. Corn samples were collected and analyzed simultaneously. RESULTS: Treatment N2P2 increased DTPA extractable Fe, Mn, and Cu in soil by 732%, 388%, and 42%, whereas M2 decreased the corresponding values by 26%, 22%, and 10%, respectively, compared to CK. DTPA extractable Zn in soil and Zn in corn grain were higher in the M and M2 treatments than in the other treatments, and DTPA Zn was significantly correlated with soil organic carbon (SOC) in large macroaggregate, microaggregate, and silt + clay fractions. The Mn concentrations in corn stalks and grain were significantly correlated with DTPA extractable Mn in bulk soil and microaggregates, and Zn in stalks were significantly correlated with DTPA Zn in bulk soil, microaggregates, and large macroaggregates. CONCLUSIONS: Long-term application of horse manure could increase soil Zn availability and uptake by corn, possibly due to its activation by SOC. In contrast, chemical fertilizer application increased DTPA extractable Fe, Mn, and Cu in soil by reducing soil pH. Our results also suggest that Mn uptake by corn originated mainly in microaggregates, whereas Zn in crops was primarily sourced from large macroaggregates and microaggregates.

Compost (mainly composed of cow manure, horse manure, chicken manure, and straw) has turned out to be effective in remediation of heavy metal-contaminated soil. However, in recent years, the effects of green waste compost (GWC) on plant growth and the immobilization of heavy metal cadmium (Cd) in the soil have not been clearly studied. We considered the effects of different GWC ratios on the growth of pakchoi cabbage, soil physical and chemical properties, total and availability of Cd content, and soil enzyme activity. The results showed that organic matter, total nitrogen, available phosphorus, and available potassium in the soil gradually put in place over the increase of compost proportion and showed a significant difference. Dehydrogenase, urease, and catalase activities grew by 380, 35, and 32% under the treatment of T10, respectively. The increase of enzyme activity indirectly reflects the enhancement of self-purification ability of contaminated soil. The addition of GWC improved soil quality, leading to a significant increase in soil nutrients, and in biomass and chlorophyll content of pakchoi cabbage. The decrease of Cd availability led to a significant reduction of Cd content in pakchoi cabbage, with a 30–36% reduction of Cd content in roots and a 43–69% reduction in leaf. The BCF of leaves decreased from 0.62 to 0.22, and the TF decreased from 0.94 to 0.46, indicating that the addition of GWC reduced the mobility of Cd to pakchoi cabbage leaves. The result is decreased in Cd content in edible parts of pakchoi cabbage.

In this study, we have examined how the activation of hydrothermally carbonized sewage sludge and horse manure influences the inorganic component of these materials and surface chemistry. This was examined through statistical correlations between kinetic tests using trimethoprim, fluconazole, perfluorooctanoic acid, and copper, zinc, and arsenic and physicochemical properties. Yield and inorganic content varied considerably, with potassium hydroxide–activated materials producing lower yields with higher inorganic content. Phosphoric acid activation incorporated inorganically bound phosphorus into the material, although this showed no statistically relevant benefit. A maximum surface area of 1363 m²g⁻¹ and 343 m²g⁻¹ was achieved for the horse manure and sewage sludge. Statistical analysis found positive correlations between carbon-oxygen functionalities and trimethoprim, fluconazole, perfluorooctanoic acid, and copper removal, while inorganic content was negatively correlated. Conversely, arsenic removal was positively correlated with inorganic content. This research provides insight into the interactions with the organic/inorganic fraction of activated waste materials for water treatment.

Historically, subsistence farmers around the Atlantic coast of NW Europe utilized marine algae as a fertilizer in agroecosystems, a practice that continued in small areas and is now considered to have real potential for re-establishing sustainable food production systems on marginal soils. Earthworms form a significant component of soil fauna, and their ecosystem services are well-documented. Therefore, palatability of marine organic amendments to faunal detritivores of terrestrial systems is of interest. This work aimed to assess the potential for growth of Aporrectodea caliginosa, Lumbricus rubellus and Aporrectodea longa fed with two common macroalgae (seaweeds), Laminaria digitata and Fucus serratus. In addition, choice chambers were constructed to permit earthworm selection of these macroalgae with more conventional organic materials, horse manure (HM) and birch leaves (BL). Over a period of 2 months, earthworm species showed significantly greater mass gain with conventional food (p < 0.05). Laminaria outperformed Fucus, which in turn was superior to soil alone. Similarly, when given a choice, a significant preference (p < 0.001) was shown for the more nitrogen-rich HM and BL over the seaweeds. No removal was recorded for A. caliginosa when offered seaweeds only. By contrast, L. rubellus and A. longa showed significant preferences (p < 0.001) for Laminaria over Fucus and fresh material over degraded. These results underline an interest to profit from natural resources (seaweeds) to maintain or improve soil biological quality in marginal coastal areas.

Adsorption on low-cost biochars would increase the affordability and availability of water treatment in, for example, developing countries. The aim of this study was to identify the precursor materials and hydrochar surface properties that yield efficient removal of compounds of environmental concern (CEC). We determined the adsorption kinetics of a mixture containing ten CECs (octhilinone, triclosan, trimethoprim, sulfamethoxasole, ciprofloxacin, diclofenac, paracetamol, diphenhydramine, fluconazole, and bisphenol A) to hydrochars prepared from agricultural waste (including tomato- and olive-press wastes, rice husks, and horse manure). The surface characteristics of the hydrochars were evaluated via diffuse reflectance infrared spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and N₂-adsorption. Kinetic adsorption tests revealed that removal efficiencies varied substantially among different materials. Similarly, surface analysis revealed differences among the studied hydrochars and the degree of changes that the materials undergo during carbonization. According to the DRIFTS data, compared with the least efficient adsorbent materials, the most efficient hydrochars underwent more substantial changes during carbonization.