Performance of compost and biochar amendments for in situ risk mitigation of aged DDT, DDE and dieldrin residues in an old orchard soil was examined. The change in bioavailability of pesticide residues to Lumbricus terrestris L. relative to the unamended control soil was assessed using 4-L soil microcosms with and without plant cover in a 48-day experiment. The use of aged dairy manure compost and biosolids compost was found to be effective, especially in the planted treatments, at lowering the bioavailability factor (BAF) by 18–39%; however, BAF results for DDT in the unplanted soil treatments were unaffected or increased. The pine chip biochar utilized in this experiment was ineffective at lower the BAF of pesticides in the soil. The US EPA Soil Screening Level approach was used with our measured values. Addition of 10% of the aged dairy manure compost reduced the average hazard quotient values to below 1.0 for DDT + DDE and dieldrin. Results indicate this sustainable approach is appropriate to minimize risks to wildlife in areas of marginal organochlorine pesticide contamination. Application of this remediation approach has potential for use internationally in areas where historical pesticide contamination of soils remains a threat to wildlife populations.

The over-use of antibiotics in animal husbandry in China and the concomitant enhanced selection of antibiotic resistance genes (ARGs) in animal manures are of serious concern. Thermophilic composting is an effective way of reducing hazards in organic wastes. However, its effectiveness in antibiotic degradation and ARG reduction in commercial operations remains unclear. In the present study, we determined the concentrations of 15 common veterinary antibiotics and the abundances of 213 ARGs and 10 marker genes for mobile genetic elements (MGEs) in commercial composts made from cattle, poultry and swine manures in Eastern China. High concentrations of fluoroquinolones were found in the poultry and swine composts, suggesting insufficient removal of these antibiotics by commercial thermophilic composting. Total ARGs in the cattle and poultry manures were as high as 1.9 and 5.5 copies per bacterial cell, respectively. After thermophilic composting, the ARG abundance in the mature compost decreased to 9.6% and 31.7% of that in the cattle and poultry manure, respectively. However, some ARGs (e.g. aadA, aadA2, qacEΔ1, tetL) and MGE marker genes (e.g. cintI-1, intI-1 and tnpA-04) were persistent with high abundance in the composts. The antibiotics that were detected at high levels in the composts (e.g. norfloxacin and ofloxacin) might have posed a selection pressure on ARGs. MGE marker genes were found to correlate closely with ARGs at the levels of individual gene, resistance class and total abundance, suggesting that MGEs and ARGs are closely associated in their persistence in the composts under antibiotic selection. Our research shows potential disseminations of antibiotics and ARGs via compost utilization.

High total and bioavailable concentrations of As in soils represent a potential risk for groundwater contamination and entry in the food chain. The use of organic amendments in the remediation of As-contaminated soils has been found to produce distinct effects on the solubility of As in the soil. Therefore, knowledge about As adsorption-desorption processes that govern its solubility in soil is of relevance in order to predict the behaviour of this element during these processes. In this paper, the objective was to determine As adsorption and desorption in four different soils, with and without compost addition, and also in competition with phosphate, through the determination of sorption isotherms. Batch experiments were carried out using three soils affected differently by previous mining activity of the Sierra Minera of La Unión-Cartagena (SE Spain) and an agricultural soil from Segovia province (central Spain). Adsorption was higher in the mining soils (and highest in the acidic one) than in the agricultural soils, although the latter were not affected negatively by organic matter or phosphate competition for sorption sites. The results show that As adsorption in most soils, both with and without compost, fitted better a multimolecular layer model (Freundlich), whereas As adsorption in competition with P fitted a monolayer model (Langmuir). Moreover, the use of compost and phosphate reduced the adsorption of As in the mining soils, while in the agricultural soils compost increased their low adsorption capacity. Therefore, the use of compost can be a good option to favour As immobilisation in soils of low adsorption, but knowledge of the soil composition will be crucial to predict the effects of organic amendments on As solubility in soils and its associated environmental risk.

Cadmium (Cd) is a non-essential trace element that accumulates in agricultural soils through the application of Cd-rich phosphate fertiliser. Vegetables can accumulate Cd to concentrations that sometimes exceed food safety standards. We investigated the potential of low-cost soil amendments to reduce Cd uptake by spinach (Spinacia oleracea L.), lettuce (Lactuca sativa L.) and onion (Allium cepa L.). Batch sorption experiments revealed the relative sorption of Cd by biosolids, charcoal, lignite, sawdust, two types of compost, bentonite and zeolite. Lignite and compost had the greatest ability to sorb Cd and were subsequently selected for pot trials, which elucidated their effect on Cd uptake by onions, spinach and lettuce in two market garden soils with native Cd concentrations of 1.45 mg/kg and 0.47 mg/kg. The addition of 2.5% (dry w/w) municipal compost reduced the Cd concentration in onions, spinach and lettuce by up to 60% in both soils. The addition of lignite gave variable results, which depended on the soil type and rate of addition. This Cd immobilisation was offset by soil acidification caused by the lignite. The results indicate that municipal compost is a low-cost soil conditioner that is effective in reducing plant Cd uptake.

As in situ use of amendments for restoration of metal-contaminated mining sites becomes increasingly accepted, the expected level of ecosystem function at these sites will increase. Use of appropriate tools to measure both the level and value of that function is critical to expand use of this approach. For these sites, amendment mixtures must reduce metal availability in situ and restore ecosystem function. Combinations of mixtures, typically consisting of a material with high metal binding capacity (cyclonic ashes, municipal biosolids, or other materials rich in Fe, Al, or Mn oxides), material to adjust soil pH (sugar beet lime, cement kiln dust, dolomitic limestone), and an organic residual to provide soil structure and nutrients (composts, animal manures, municipal biosolids) have been tested in multiple lab and field trials on metal-contaminated sites. This review focuses on field tests of this approach with the goal of providing methods to quantify reduction of hazard and restoration of functional systems. Methods to evaluate success of amendments including extractions to measure changes in metal availability, microbial function and diversity, phytoavailability of metals, and earthworm and small mammal assays are discussed. In most cases, measures of metal availability and ecosystem function are related. For example, surveys of small mammals on restored sites provide information on metal availability as well as suitability of restored habitat. Additional measures of ecosystem function including soil fertility, physical properties, and diversity of habitat are described. Finally, measures of the value of this approach for restoring ecosystems are detailed.

This study aims to evaluate a new biosorbent derived from co-composting eggshell with other organic materials (potato peels, grass clipping, and rice husk) for uptaking Pb(II) from an aqueous medium. This biosorbent contains a high amount of eggshell (30 % w/w; CES) and its performance was compared to mature compost without eggshell (CWES) and natural eggshell (ES). Sorption kinetics and equilibrium data were fitted to pseudo-second-order and Langmuir models, respectively. From a kinetic point of view, lead sorption into CES was fast, attaining equilibrium within less than 180 min. Batch experiments indicated that maximum sorption capacity of Pb into CES is 23 mg g⁻¹. The sorption capacity of CES was not significantly dependent on pH within the range of 2–5.5. In comparison to ES, organic matter of CES provided supplementary sites for lead sorption and an increase of 43 % in the sorption capacity was observed. Nevertheless, CWES was the biosorbent with higher sorption capacity. Still, this study points out the potential of new use of CES as an effective biosorbent to lead removal from aqueous matrices.

Mine soils often contain high levels of metals that produce serious environmental problems and poor fertility conditions that limit their reclamation. The aim of this study was to evaluate the influence of a compost and biochar amendment on the nutrient phytoavailability in a mine soil from the depleted copper mine of Touro (Spain). For this purpose, a greenhouse experiment was carried out amending the mine soil with increasing proportions (20, 40, 80 and 100%) of the compost and biochar mixture and planting Brassica juncea plants. The results revealed that the mine soil had an extremely acid pH and low fertility conditions and was affected by copper contamination. The addition of compost and biochar to the mine soil increased soil pH values (from 2.7 to 8.7), total carbon (from undetectable values to 149 g kg⁻¹) and total nitrogen (from undetectable values to 11,130 mg kg⁻¹) contents and phytoavailable concentrations of K, Mg, Na and P and promoted plant growth, since B. juncea plants did not survive in the untreated mine soil. The application of amendment decreased the phytoavailable concentration of Al, Co, Cu, Fe and Ni in the soil, resulting in a reduction of copper toxicity. The use of compost and biochar as a soil amendment combined with B. juncea plants could be an efficient strategy for the reclamation of degraded soils with low fertility conditions.

The influence of manure and composts on the leaching of heavy metals from soil was evaluated in a model lysimeter experiment under controlled conditions. Soil samples were collected from experimental fields, from 0- to 90-cm layers retaining the layout of the soil profile layers, after the second crop rotation cycle with the following plant species: potatoes, spring barley, winter rapeseed, and winter wheat. During the field experiment, 20 t DM/ha of manure, municipal sewage sludge composted with straw (SSCS), composted sewage sludge (SSC), dried granular sewage sludge (DGSS), “Dano” compost made from non-segregated municipal waste (CMMW), and compost made from municipal green waste (CUGW) was applied, i.e., 10 t DM/ha per crop rotation cycle. The concentrations (μg/dm³) of heavy metals in the leachate were as follows: Cd (3.6–11.5) < Mn (4.8–15.4) < Cu (13.4–35.5) < Zn (27.5–48.0) < Cr (36.7–96.5) < Ni (24.4–165.8) < Pb (113.8–187.7). Soil fertilization with organic waste materials did not contaminate the percolating water with manganese or zinc, whereas the concentrations of the other metals increased to the levels characteristic of unsatisfactory water quality and poor water quality classes. The copper and nickel content of percolating water depended on the concentration of those metals introduced into the soil with organic waste materials. The concentrations of Cd in the leachate increased, whereas the concentrations of Cu and Ni decreased with increasing organic C content of organic fertilizers. The widening of the C/N ratio contributed to Mn leaching. The concentrations of Pb, Cr, and Mn in the percolating water were positively correlated with the organic C content of soil.

Biomixtures comprise the active part of biopurification systems (BPS) for the removal of pesticide-containing wastewater from agricultural origin. Considering that biomixtures contain an important amount of lignocellulosic substrates, their bioaugmentation with degrading ligninolytic fungi represents a promising way to improve BPS. The fungus Trametes versicolor was employed for the bioaugmentation of rice husk-compost-soil (GCS) biomixtures in order to optimize the removal of the highly toxic insecticide/nematicide carbofuran (CFN). Composition of biomixtures has not been optimized before, and usually, a volumetric composition of 50:25:25 (lignocellulosic substrate:humic component:soil) is employed. Optimization of the biomixture composition was performed with a central composite design, using the volumetric content of rice husk (pre-colonized by the fungus) and the volumetric ratio compost/soil as design variables. Performance of biomixtures was comprehensively assayed considering CFN removal, the production of toxic transformation products (3-hydroxycarbofuran/3-ketocarbofuran), the ability to mineralize [¹⁴C]carbofuran, and the residual toxicity in the matrix. According to the models, the optimal volumetric composition of the GCS biomixture is 30:43:27, which maximizes removal and mineralization rate, and minimizes the accumulation of transformation products. Results support the value of assessing new biomixture formulations according to the target pesticide in order to obtain their optimal performance, before their use in BPS.

Livestock manure and compost are commonly used to supply nutrients for crops and improve soil quality. However, excess application may increase the risk of nutrient loss and eutrophication. We investigated the potential leaching losses of nitrogen (N), phosphorus (P), and non-purgeable organic carbon (NPOC) over 105 days in the laboratory. Soils were amended with four treatments: (1) manure (BM) and (2) compost (BC) from cattle fed a typical finishing diet, (3) manure (DDGSM), and (4) compost (DDGSC) from cattle fed diets containing 60 % wheat dried distillers’ grains with solubles (DDGS) replacing barley grain. A non-amended control soil was included for comparison. Leachate samples were collected 0, 7, 21, 42, 70, and 105 days after amendment application. Amendment application significantly increased leaching loss of total nitrogen (TN), NO₃ ⁻-N, NH₄ ⁺-N, total phosphorus (TP), ortho-P (PO₄ ³⁻-P), and NPOC from soils by 2.2 to 154.8 times compared with the control. Regardless of whether DDGS was included in cattle diet, cumulative leaching losses of TN, NO₃ ⁻-N, TP, and PO₄ ³⁻-P were significantly higher, while NH₄ ⁺-N and NPOC were lower from compost-amended soil than manure-amended soil. The proportion of cumulative N leaching losses relative to the total N applied was greater with DDGSM and DDGSC than BM and BC, while a greater proportion of total P was leached from DDGSM and DDGSC than BM. Based on the results, more attention should be paid to the potential risk of soil nutrient leaching posed after applying manure and compost, and the higher risk of N and P leaching losses from soil amended with DDGS manure and compost than manure from beef cattle fed typical finishing diets.