Organic Nutrient Concentrations Research Articles

Black soldier fly larvae frass increases the soil’s residual nutrient content and enzymatic activity – a lettuce production trial

The aim of this study was to evaluate the potential agronomic value of black soldier fly larvae frass (BSFF) as an organic fertiliser in short-cycle crops, using lettuce as the test plant. Treatments consisted in applying different fertilisers (BSFF and mineral) at different doses and combinations. The experiment was carried out for 42 days and plants were analysed in terms of biomass production, while the soil was chemically characterised before and after fertilisation, in order to assess the residual nutrient concentrations. In addition, soil microbial activity was assessed through the activity of the enzymes dehydrogenase and β-glucosidase. The highest yields were obtained with an exclusive mineral fertilisation (162.5±61.8 g fresh weight) and with a mixture of organic/mineral fertilisation (144.5±16.8 g) in comparison to exclusive fertilisation with BSFF, probably due to the immobilisation and slow mineralisation rate of the N provided by frass, along with the choice of the short-cycle plant, which requires readily available nutrients. Nevertheless, the BSFF increased the soil’s organic matter and residual nutrient content after 42 days of experiment, as well as the enzymatic activity of dehydrogenase and β-glucosidase, by at least 121 and 24% in the soils fertilised with BSFF, respectively. Thus, despite not being effective as an exclusive fertiliser for a short cycle culture, the BSFF included in a mixture with mineral fertilisation, may compete with exclusive mineral fertilisation with the benefit of improving the sustainability of soil fertility and crop production.

Assessment of Seasonal and Spatial Variation of the Organic Carbon and Nutrients in the Ghaghara River Sediment

To assess the organic carbon and nutrients content and its seasonal and spatial variation, sediment samples were collected three times from 18 different locations starting from Keuna, Nepal to Doriganj, Bihar from Ghaghara River during the year 2018-19. The value of pH varied from 7.6 to 8.8 during the study period and indicated the alkaline nature of the sediment. The electrical conductivity (EC) value varied from 0.09 to 0.47 (m S cm-1) in the study area, which shows the contribution of the anthropogenic input mainly from domestic and industrial sources to the sediment of the Ghaghara River. The sediment organic carbon (SOC) was in the range of 0.14 to 1.26 %, with relatively higher concentrations during the post-monsoon and monsoon season. The concentration (Mean ± SD) of nitrate, ammonium, phosphate, sulphate and silica in the sediment samples of Ghaghara River were 7.05 ± 1.19, 5.5 ±1.7, 1372 ± 509, 562 ± 157, and 159306 ± 36192 (mg kg-1), respectively, during post-monsoon season, 2.05 ± 0.59, 18.0 ± 5.2, 1814 ± 318, 602 ± 139, and 180152 ± 52098 (mg kg-1) in pre-monsoon season, and were 7.3 ± 3.3, 7.8 ± 1.4, 1835 ± 696, 438 ± 85, and 163625 ± 68143 (mg kg-1) in monsoon season, respectively. The bulk density (BD), pH, EC, nitrate, ammonium, sulphate, and phosphate content showed significant seasonal variation and in the case of spatial variation, while only EC and sediment organic carbon showed significant variation in the Ghaghara river sediment.

Effects of long-term fertilization with different substitution ratios of organic fertilizer on paddy soil

In recent years, the abuse of chemical fertilizers has caused numerous environmental problems, such as soil acidification and compaction. Replacing chemical fertilizers with organic fertilizers can effectively alleviate these problems. However, the effects of alternative organic fertilizers remain unclear. To explore the effects of organic fertilizer substitution on rice yield and paddy soil physicochemical properties and bacterial community structure, we conducted a 5-year experiment using different proportions of organic fertilizer substitution in a double-cropping rice field in Jiangxi, China. Our results showed that replacing chemical fertilizers with organic fertilizers can reduce soil acidification, increase soil organic matter content, nutrient contents, and enzyme activities, improve soil physicochemical properties and microbial community, and enhance soil metabolism. Appropriate organic substitution also had positive effects on rice production. These findings enhance our understanding of the effects of different alternative organic fertilization methods and have important theoretical significance for the promotion of the use of organic fertilizers in the future.

Multifractal dimensions of soil particle size distribution reveal the erodibility and fertility of alpine grassland soils in the Northern Tibet Plateau

Climate change and human activities have seriously degraded alpine grassland, potentially affecting soil particle size distribution (PSD) and further influencing the nutrient levels and erodibility of soil. Predicting the fertility and erodibility of alpine soil using multifractal dimensions of soil PSD could be used to enhance the management and restoration of degraded alpine grasslands. In the present study, we evaluated three types of alpine grasslands: alpine meadow (AM), alpine steppe (AS), and alpine desert steppe (ADS). Fencing and grazing management measures were conducted at sites containing each grassland type. Then, we analyzed the PSDs, erodibility, and other properties of soil in the 0–20 cm soil layer. Multifractal characterization of soil PSD was calculated using the fractal scale theory. The findings showed that grassland type significantly impacted soil nutrients and the multifractal dimensions of soil PSDs, whereas management measures affected soil erodibility significantly. The proportion of finer particles decreased as follows: AM > AS > ADS. Compared to grazing, fencing enhanced clay content and reduced the proportion of coarser particles under all three grassland types. AM had higher organic carbon and nitrogen levels than AS and ADS. Multifractal dimensions were highest for AM, with ADS having higher erodibility than AM and AS. Multifractal dimensions (except for correlation dimension) also had significantly positive relationships with soil organic carbon and available nutrient content and soil erodibility, but had significantly negative correlations with soil pH, bulk density, and electrical conductivity. Thus, the multifractal dimensions of soil PSDs could be used to characterize the erodibility and fertility characteristics of soil in alpine regions, providing a reference for assessing vegetation restoration measures in the Northern Tibet Plateau.

Continuous Cultivation of Microalgae in Cattle Slaughterhouse Wastewater Treated with Hydrodynamic Cavitation

Cattle slaughtering produce large amounts of wastewater containing high concentrations of organic matter and nutrients and requires significant treatment before disposal or reutilization. However, the nutrients contained can be valued as a medium for microalgal biomass generation. In this work, hydrodynamic cavitation (HC) followed by membrane filtration or biological (microalgae cultivation) treatment in continuous mode were performed. From cattle slaughterhouse wastewater (CSW), by the effect of HC treatment with air injection in batch mode, more than 20% of the chemical oxygen demand (COD) was removed. In a continuous HC process, the COD content in output was 324 mg O2/L, which is 68% lower than the supplied CSW. After that, 76% of residual COD was removed by filtration through a tubular alumina membrane (600 nm). Finally, 85% of residual COD after HC treatment in 24 h in a batch mode was removed by microalgae. On the other hand, the COD concentration in the output was around 59 mg O2/L in continuous mode, which represents 85–93% COD removal. The process involving HC and microalgae growing looks promising since in addition to water treatment, the microalgae produced could be valued in a biorefinery concept.

Scale-dependent effects of vegetation on flow velocity and biogeochemical conditions in aquatic systems

In rivers, scale-dependent feedbacks resulting from physical habitat modifications control the lateral expansion of submerged plant patches, while the mechanisms that limit patch expansion on a longitudinal dimension remain unknown. Our objective was to investigate the effects of patch length on physical habitat modification (i.e., flow velocity, sediment grain size distribution), the consequences for biogeochemical conditions (i.e., accumulation/depletion of nutrients, microbial respiration), and for individual plants (i.e., shoot length). We measured all of these parameters along natural patches of increasing length. These measurements were performed at two sites that differed in mean flow velocity, sediment grain size, and trophic level. The results showed a significant effect of patch length on organic matter content and nutrient concentrations in interstitial water. For the shortest patches sampled, all of these parameters had similar values to those measured at the upstream control position. For longer patches, organic matter content and orthophosphate and ammonium concentrations increased within the patch compared to the upstream bare sediment, whereas nitrate concentrations decreased, suggesting changes in vertical water exchanges and an increase in anaerobic microbial activities. Furthermore, plant height was related to patch length by a quadratic pattern, probably due reduced hydrodynamic stress occurring for increasing patch length, combined with conditions that are less favourable for plants over a threshold length, possibly due to the light limitation or to the high concentration of ammonium that in the concentration range we measured may be toxic for plants. The threshold lengths over which patches influence the nutrient concentrations were reduced for the site with higher nutrient levels. We demonstrated that the plant-induced modifications of the physical habitat exert important effects on biogeochemical conditions, with possible consequences for patch dynamics and ecosystem functioning.

Resolving the Drivers of Algal Nutrient Limitation from Boreal to Arctic Lakes and Streams

Nutrient inputs to northern freshwaters are changing, potentially altering aquatic ecosystem functioning through effects on primary producers. Yet, while primary producer growth is sensitive to nutrient supply, it is also constrained by a suite of other factors, including light and temperature, which may play varying roles across stream and lake habitats. Here, we use bioassay results from 89 lakes and streams spanning northern boreal to Arctic Sweden to test for differences in nutrient limitation status of algal biomass along gradients in colored dissolved organic carbon (DOC), water temperature, and nutrient concentrations, and to ask whether there are distinct patterns and drivers between habitats. Single nitrogen (N) limitation or primary N-limitation with secondary phosphorus (P) limitation of algal biomass was the most common condition for streams and lakes. Average response to N-addition was a doubling in biomass; however, the degree of limitation was modulated by the distinct physical and chemical conditions in lakes versus streams and across boreal to Arctic regions. Overall, algal responses to N-addition were strongest at sites with low background concentrations of dissolved inorganic N. Low temperatures constrained biomass responses to added nutrients in lakes but had weaker effects on responses in streams. Further, DOC mediated the response of algal biomass to nutrient addition differently among lakes and streams. Stream responses were dampened at higher DOC, whereas lake responses to nutrient addition increased from low to moderate DOC but were depressed at high DOC. Our results suggest that future changes in nutrient availability, particularly N, will exert strong effects on the trophic state of northern freshwaters. However, we highlight important differences in the physical and chemical factors that shape algal responses to nutrient availability in different parts of aquatic networks, which will ultimately affect the integrated response of northern aquatic systems to ongoing environmental changes.

Land-cover, climate and fjord morphology drive differences in organic matter and nutrient dynamics in two contrasting northern river-fjord systems

Climate and land-use changes are leading to impacts on individual ecosystems as well as shifts in transfer dynamics between interconnected systems. At the land-ocean interface, changes in riverine inputs of organic matter (OM) and nutrients have the potential to lead to shifts in coastal carbon and nutrient cycling with consequences for ecosystem structure and function. In this study, we assess OM and nutrient dynamics for two contrasting Norwegian river-to-fjord systems: a boreal system with a forested catchment draining into a narrow fjord (‘narrow boreal system’), and a subarctic system where lowland forests and mountainous regions drain into a broad fjord (‘broad subarctic system’). We characterized seasonal organic carbon and nutrient concentrations and DOM absorption properties for samples collected along transects from river to outer fjord during 2015/2016. While differences in catchment properties drove contrasts in river chemistry between the two study rivers, fjord morphology and hydrodynamics as well as dissolved organic carbon (DOC) and nutrient concentrations in marine receiving waters predicted water-chemistry patterns along the transect. The narrow boreal system, with high riverine DOC and nutrient concentrations, was structured mainly by a horizontal salinity gradient from river to outer fjord, with limited impact of seasonality. In contrast, the broad subarctic system tended to be dominated by vertical salinity stratification, with strong between-date differences in surface water salinity linked to seasonality in river discharge. These dynamics were also reflected in the strong horizontal gradients in DOC, nutrients and DOM properties in the narrow boreal system, in contrast to the broad subarctic system, where strong seasonality paired with a lack of strong contrast between riverine and marine concentrations of DOC and most nutrients led to an uncoupling between salinity and other water chemistry variables. In the narrow boreal system, terrestrial OM dominated both the particulate and dissolved OM pools, while OM in the broad subarctic system was derived primarily from marine phytoplankton. Non-linear declines in NO3 + NO2 were observed consistently in the boreal system and during the productive spring season in the subarctic system, suggesting biological uptake and a potentially important role of these rivers as sources of bioavailable N to coastal ecosystems. The results from these two case studies highlight the complex and interacting effects of catchment land-cover, river water chemistry and discharge, fjord morphometry and hydrodynamics in structuring the transport, fate and potential impacts of terrestrially-derived nutrients and organic matter in northern coastal environments.

Seasonal patterns in nutrient bioavailability in boreal headwater streams

AbstractChanges in nutrient bioavailability due to increased loading of dissolved organic matter (DOM) may impact boreal freshwaters. Yet, the relative bioavailability of carbon (C), nitrogen (N), and phosphorus (P) associated with terrestrial DOM remains poorly understood. We applied short‐term bioassays with natural bacterial inocula to determine seasonal variation in bioavailable organic nutrient pools from four boreal headwater streams in northern Sweden. Experiments were designed to exhaust bioavailable nutrients associated with DOM by inducing limiting conditions when all required resources except for the targeted nutrient (C, N, or P) are provided in excess. We hypothesized that the supply of different bioavailable nutrients to streams would reflect seasonal variations in terrestrial demand, hydrology, and temperature. The delivery of bioavailable DOM‐associated resources from the four streams were, on average, 2%, 11%, and 38% of the total dissolved organic C, N, and P, respectively, emphasizing the relatively low C bioavailability in these DOM‐rich waters. Bioavailable N : P ratios peaked in autumn for all sites, with lower values in winter and spring. Both in terms of relative (% of total) and absolute bioavailable organic nutrient concentrations, the seasonal pattern was characterized by systematically high values for the autumn period. Furthermore, links between bioavailable resources and temperature and hydrology varied across sites, time periods, and the different elements. Thus, elevated concentrations of bioavailable organic resources in autumn suggest the potential for leaf fall, as well as late season storms that rewet dry soils, to serve as considerable sources of C, N, and P to boreal aquatic ecosystems.

Changes in soil properties during iron mining and in rehabilitating minelands in the Eastern Amazon.

Open-cast iron mining causes drastic disturbances in soil properties. Recovery of soil chemical and physical properties is essential for successful revegetation and landscape rehabilitation. To identify changes in soil properties during the mining and revegetation process, soil samples were collected from undisturbed sites represented by forestand ferriferous savannas stocking above iron outcrops, called "cangas," in open-pit benches, and in rehabilitation chronosequences of iron waste piles in the Carajás Mineral Province (CMP), Eastern Amazon, Brazil. The samples wereanalyzed for chemical and physical properties. Our results showed that iron mining operations resulted in significant alteration of the chemical soil properties when forest and canga vegetation are suppressed to form open-pit benches or waste piles in the CMP. Mining substrates showed lower contents of soil organic matter (SOM) and nutrients than undisturbed areas of forests and cangas. In order to achieve the success of revegetation, nutrients have been added prior to plant establishment. We have demonstrated how soil fertility changes along with mineland rehabilitation, and the variation among chronosequence was attributable mainly due to contents of SOM, K, and B in the soil. The slight improvement of SOM found in rehabilitated waste piles reinforces the notion that recovery of soil quality can be a slow process in iron minelands in the CMP.

Addition of mature compost improves the composting of green waste

Composting is an environmentally friendly and effective way to dispose of green waste (GW), but traditional composting of GW is slow and results in the loss of many nutrients and a poor-quality compost product. In this study, mature compost (MC), which may function as an inexpensive and readily available microbial inoculant, was added to GW at 15, 20, 25, and 30% (w/w, dry weight basis) (treatments T2–T5, respectively); GW with 0.5% (v/w, dry weight basis) commercial microbial inoculum served as T1, and GW without any microbial inoculant served as the control. The treatment that produced the highest quality compost was determined based on the following compost properties: temperature, bulk density, porosity, pH, electric conductivity, contents of organic matter and nutrients, Fourier-transform infrared spectroscopy data, and phytotoxicity. The results showed that addition of 25% MC resulted in the best quality product in only 40 days.

Productivity of Populus nigra L. in two different soils over five rotations

This study describes growth performance and productivity of poplars (Populus nigra L.) on a 5-year rotation in two soil types. Two adjacent and even-aged stands of poplar (PS1 and PS2) with different productivity were selected in poplar plantations of Tehran, Iran. On a 5-year rotation, growth parameters of poplar trees were measured and productivity was computed. A transect sampling method with 10% intensity was used for measurement of the growth parameters. A composite soil sample was taken for all transects, and soil physico-chemical properties were determined. Texture, EC, organic matter percent, the contents of some macro and micro nutrients and some heavy metal concentrations of soil had significant differences between two stands; as a consequence growth performance and productivity of poplars were significantly difference between PS1 and PS2. In PS1, productivity of 5-year trees was 2.5 times higher than in PS2. Soil with Clay Loam texture, more contents of organic matter and nutrients, lower EC and lower contents of Ca, Mg, S and heavy metals provided more suitable conditions for growth of poplars. The growth parameters were positively correlated with the contents of nutrients, clay and organic matter in the soil, but they were negatively related to EC and the contents of silt, Ca, Mg, S and heavy metals of soil. Careful selecting sites based on soil properties before planting can be useful for increasing productivity of poplars.

Decomposition Behavior of Triarrhena lutarioriparia Tissues in Dongting Lake Water: A Laboratory Simulation Study

AbstractFollowing the overall withdrawal of papermaking enterprises, Triarrhena lutarioriparia, a most abundant macrophyte of Dongting Lake wetland, will remain to be uncut and decay in the lake water. The decomposition dynamics of T. lutarioriparia tissues and the decomposition effects on water quality are investigated in this study. The results show that two main processes are observed during the 90‐day decomposition period of T. lutarioriparia: rapid leaching and gradual biodegradation. During the initial 10‐day leaching process, the initial weight loss of leaves, spikes, and stems reached 13.33%, 12.44%, and 4.67%, respectively; meanwhile, 15.12–32.62% of total nitrogen and 24.16–45.45% of total phosphorus in the tissues are released to the water. The decomposition rate of T. lutarioriparia tissues is in the order: spikes (0.0053 day−1) > leaves (0.0045 day−1) > stems (0.0033 day−1). The T. lutarioriparia decomposition exerted adverse effects on the lake water quality, including the depletion of dissolved oxygen, the increase in concentrations of organic matter and nutrients, especially during the rapid leaching process. Such adverse effects are significantly associated with both the biomass (p < 0.001) and the species of T. lutarioriparia tissues (p < 0.05).

The Effect of Kerosene Pollution on the Cellulolytic Activity of Albic Retisols and Arenosols (Aridic): A Laboratory Experiment.

The results of a laboratory experiment modeling the effect of kerosene contamination on the cellulolytic activity of microbiocenosis of the Albic Retisol (Kaluga oblast, Russia) and Arenosol (Kyzylorda oblast, Republic of Kazakhstan) humus horizons are described. Cellulolytic activity is assessed according to the rate of weight loss in linen cloth fragments during the incubation for 0–3, 3–7, and 7–13 months. The intensity of cellulolytic activity in the unpolluted Albic Retisol is higher as compared with the Arenosol, which is determined by low acidity and an elevated content of organic matter and nutrients. The soil pollution with kerosene to 10 g/kg causes a reversible change in cellulolytic activity of both Albic Retisol and Arenosol (Aridic). A high load of kerosene (≥25 g/kg) inhibits cellulolytic activity in both soils over 13 months of observation.Supplementary InformationThe online version contains supplementary material available at 10.1134/S1064229322020119.Fig. S1. Cellulolytic activity of soils in a laboratory experiment: (a) initial state of linen tissue (test object) and (b) linen tissue after three months of incubation. Table S1. Properties of soil humus horizons.Table S2. Initial water content in the studied soil samples with due account for the added kerosene.Table S3. Cellulolytic activity in soils grouped according to kerosene load (rate of mass loss, mg/g soil per day.Table S4. Significance of differences between cellulolytic activities of contaminated soil samples relative control samples according to the Mann–Whitney U-test. Table S5. Kerosene content in the studied soil samples at the end of the experiment, % of the initial content.

Effects of Bacillus fertilizer and agent on growth of young peach tree and soil environment under replant condition.

We analyzed the effects of Bacillus fertilizer and agent supplementation at different concentrations in the replanted soil by examining the growth of young peach trees, soil nutrients, enzyme activities, and fungal commu-nity. The aim of this study was to provide theoretical basis for alleviating peach replant diseases. One-year-old potted 'Yuanmeng' peach trees were subjected to eight treatments: replanted soil without supplementation (RS), non-replanted soil without supplementation (NS), replanted soil with 1%, 4%, 8% Bacillus fertilizer supplementation (BF1, BF2, BF3), and 0.1‰, 0.5‰, 1‰ Bacillus agent supplementation (B1, B2, B3), respectively. The results showed that shoot growth and root biomass under NS treatment were greater than that under other treatments, and the contents of soil organic matter, available nutrients and soil catalase activity were greatly enhanced. Peach trees treated with BF and B treatments showed better root development than RS, among which, BF3 and B1 treatments were the best, and B1 treatment had similar effects as NS treatment. Compared with RS, BF and B treatments significantly increased the activities of soil catalase and urease during new shoot development, while B treatment significantly increased soil sucrase activity after the growth cessation of new shoots. Bacillus fertilizer and agent increased soil fungal diversity and the relative abundance of Ascomycota, Chaetomium and Penicillium, and decreased that of Basidiomycota. Considering the comprehensive parameters, BF3 and B1 showed more significant effects. In summary, our findings indicated that the supplementation of Bacillus fertilizer and agent to replanted soil could improve soil fertility, fungal community, and root development of roots, and thus provided a feasible method to alleviate peach replant diseases.

Comparison of dissolved organic carbon and nutrients content in Papua peatland

Indonesia’s peatlands degrade due to land conversion and land development. Peatland conversion affects nutrient content in peat soil and peat water, including dissolved organic carbon (DOC). Research on the comparison of DOC and nutrient content was conducted in Papua peatland. It was carried out at Kaliki and Marga Mulia in Merauke, and also at Khanami and Yame in Mappi. This research aimed to determine DOC, soil, and water nutrients, then compare them among peatlands in Merauke and Mappi. At each location, three replications of peat water and peat soil were sampled by digging to a depth of 20 cm. The peat water was estimated for DOC concentration and nutrients, but peat soil was analyzed for nutrients only. The DOC concentration at Yame was the highest among the sites, followed by Khanami, Marga Mulia, and Kaliki. Soil carbon stored was estimated highest at Khanami, followed by Kaliki, Yame, and Marga Mulia. It was concluded that the DOC and soil carbon stored were higher in Mappi peatland than in Merauke peatland because it was still preserved by the community and no peatland conversion in Mappi.

Efektivitas Penggunaan Limbah Cair Tahu sebagai Bahan Substitusi Pencampuran Media Tanam dalam Percepatan Pertumbuhan Miselium Jamur Tiram (Pleurotus ostreatus)

Tofu liquid waste with protein content is one of the wastes that has economic value, because the content of organic compounds and nutrients contained in it is still relatively high. Oyster mushroom is a type of wood mushroom that has a higher nutritional content than other types of wood mushrooms. Market demand for oyster mushrooms continues to increase. The need for oyster mushrooms is still relatively high and its fulfillment is still limited, therefore it is necessary to add nutrients from the outside, where tofu liquid waste can be used as an alternative growing medium for oyster mushrooms. This study aims to determine the extent to which tofu liquid waste has the potential as a substitute for mixing planting media in accelerating the growth of mycelium of oyster mushroom (Pleurotus ostreatus). This type of research is a pure experiment using a completely randomized design (CRD) using 4 treatments (0% concentration, 25%, 50%, 75% and 100%) and 5 replications. Parameters observed were the increase in length, thickness and color of the mycelium. Data were analyzed using 5% ANOVA (Analysis Of Variance) with the help of SPPS for windows program. The results of the value analysis based on the increase in length, thickness and color of the mycelium were 1.737 cm (t-count = 2.911 > t-table = 0.094); thick (t-count = 0.688 > t-table = 0.411) and white (t-count = 1.219 > t-table = 0.001).

Bio-Based Waste’ Substrates for Degraded Soil Improvement—Advantages and Challenges in European Context

The area of degraded sites in the world is constantly expanding and has been a serious environmental problem for years. Such terrains are not only polluted, but also due to erosion, devoid of plant cover and organic matter. The degradation trends can be reversed by supporting remediation/reclamation processes. One of the possibilities is the introduction of biodegradable waste/biowaste substrates into the soil. The additives can be the waste itself or preformed substrates, such composts, mineral-organic fertilizers or biochar. In EU countries average value of compost used for land restoration and landfill cover was equal 4.9%. The transformation of waste in valuable products require the fulfillment of a number of conditions (waste quality, process conditions, law, local circumstances). Application on degraded land surface bio-based waste substrates has several advantages: increase soil organic matter (SOM) and nutrient content, biodiversity and activity of microbial soil communities and change of several others physical and chemical factors including degradation/immobilization of contaminants. The additives improve the water ratio and availability to plants and restore aboveground ecosystem. Due to organic additives degraded terrains are able to sequestrate carbon and climate mitigate. However, we identified some challenges. The application of waste to soil must comply with the legal requirements and meet the end of use criteria. Moreover, shorter or long-term use of bio-waste based substrate lead to even greater soil chemical or microbial contamination. Among pollutants, “emerging contaminants” appear more frequently, such microplastics, nanoparticles or active compounds of pharmaceuticals. That is why a holistic approach is necessary for use the bio-waste based substrate for rehabilitation of soil degraded ecosystems.

Flushing of Soils Highly Contaminated with Cd Using Various Washing Agents Derived from Sewage Sludge

The suitability of sewage-sludge derived washing agents (SS_WAs) (dissolved organic matter DOM; humic-like substances HLS; soluble humic substances SHS), was assessed for removing Cd from highly contaminated (300 mg/kg) sandy clay loam and clay. The soils were remediated via column flushing at two flow rates, 0.5 and 1.0 mL/min. The stability of the flow velocity (FV) depended on the type of SS_WA and decreased in the following order: DOM > HLS > SHS. Cd was most effectively removed during the first hours of flushing, and the process proceeded with a first-order kinetics. The overall process efficiency was higher at flow rate of 1.0 mL/min than at 0.5 mL/min and ranged from 65.7 (SHS) to 75.5% (DOM) for the sandy clay loam and from 64.7% (SHS) to 67.8% (DOM) for the clay. However, all SS_WAs at both flow rates removed the most mobile Cd fraction (F1) with an efficiency above 90%. Flushing improved soil characteristics in terms of the content of organic matter, humic substances and nutrients. Among all SS_WAs, DOM was the most suitable for remediation of highly Cd-contaminated soils due to high efficiency of Cd removal, the high stability of its FV during flushing and the simple manner of DOM recovery from sewage sludge.

Part A: Sanitization and use of sewage sludge in soil Technical Note 2 - Legislation aspects

The use of sewage sludge in soil is a environmentally sustainable practice, compatible with the Brazilian Policy of Solid Wastes. Due to its content of organic compounds and nutrients, the sludge is beneficial to the physical, chemical and biological soil properties and to the development of plants. However, since it may contain chemical and microbiological pollutants, it has to be carefully used by following criteria and procedures concerning the protection of the environment and public health. In 2020, Brazil approved Resolution 498 of CONAMA for the definition of criteria and procedures for production and application of biosolids in soil. Besides its agricultural use, this Resolution covers other uses, such as the recuperation of degraded areas. For the use of sludge on land, it needs to be processed in a Sludge Management Unit licensed by a local environmental agency. Depending on the criteria in the Resolution, biosolids are classified under Classes A and B for their microbiological quality, and under Classes 1 and 2 for their chemical aspects.