Soil Total Content Research Articles

Relatively stable metal(loid) levels in surface soils of a semiarid Inner Mongolia steppe under multiple environmental change factors

Global change is increasingly recognized as a possible regulator of metal(loid) biogeochemistry, but it is not well known whether and to what extent multiple environmental change factors alter the metal(loid) levels in surface soils. Here, we analyzed the total concentrations of surface soil metal(loid)s (Ca, Mn, Cr, V, Pb, Ni, Cu, Co, As, and Cd) with 3 years of simulated warming, increased precipitation, nitrogen addition, and elevated CO2, and with 9 years of simulated warming and increased precipitation, both in the Inner Mongolia steppe (northern China). Three relatively mobile fractions of the metal(loids), i.e., exchangeable, carbonate, and organic-bound fractions, were also quantified. Results showed that multiple environmental change factors had antagonistic interactions on only a few number of total or fractional metal(loid) concentrations. The antagonistic interactions between nitrogen addition and elevated CO2 on some metal(loid) concentrations suggest that the significant simple effects of N addition without elevated CO2 treatment reported here or previously may not happen with a future, higher CO2 level. The main effects of all 3- or 9-years of treatments on total or fractional metal(loid) concentrations in surface soils were all no more than 25%. These findings indicate that global environmental change has a relatively weak impact on surface soil metal(loid) pools and the associated ecological risks in the Inner Mongolia steppe at a near-decadal scale.

Review: mine tailings in an African tropical environment-mechanisms for the bioavailability of heavy metals in soils.

Heavy metals are of environmental significance due to their effect on human health and the ecosystem. One of the major exposure pathways of Heavy metals for humans is through food crops. It is postulated in the literature that when crops are grown in soils which have excessive concentrations of heavy metals, they may absorb elevated levels of these elements thereby endangering consumers. However, due to land scarcity, especially in urban areas of Africa, potentially contaminated land around industrial dumps such as tailings is cultivated with food crops. The lack of regulation for land-usage on or near to mine tailings has not helped this situation. Moreover, most countries in tropical Africa have not defined guideline values for heavy metals in soils for various land uses, and even where such limits exist, they are based on total soil concentrations. However, the risk of uptake of heavy metals by crops or any soil organisms is determined by the bioavailable portion and not the total soil concentration. Therefore, defining bioavailable levels of heavy metals becomes very important in HM risk assessment, but methods used must be specific for particular soil types depending on the dominant sorption phases. Geochemical speciation modelling has proved to be a valuable tool in risk assessment of heavy metal-contaminated soils. Among the notable ones is WHAM (Windermere Humic Aqueous Model). But just like most other geochemical models, it was developed and adapted on temperate soils, and because major controlling variables in soils such as SOM, temperature, redox potential and mineralogy differ between temperate and tropical soils, its predictions on tropical soils may be poor. Validation and adaptation of such models for tropical soils are thus imperative before such they can be used. The latest versions (VI and VII) of WHAM are among the few that consider binding to all major binding phases. WHAM VI and VII are assemblages of three sub-models which describe binding to organic matter, (hydr)oxides of Fe, Al and Mn and clays. They predict free ion concentration, total dissolved ion concentration and organic and inorganic metal ion complexes, in soils, which are all important components for bioavailability and leaching to groundwater ways. Both WHAM VI and VII have been applied in a good number of soils studies with reported promising results. However, all these studies have been on temperate soils and have not been tried on any typical tropical soils. Nonetheless, since WHAM VII considers binding to all major binding phases, including those which are dominant in tropical soils, it would be a valuable tool in risk assessment of heavy metals in tropical soils. A discussion of the contamination of soils with heavy metals, their subsequent bioavailability to crops that are grown in these soils and the methods used to determine various bioavailable phases of heavy metals are presented in this review, with an emphasis on prospective modelling techniques for tropical soils.

Evaluation of Nitric Acid Extraction of Elements from Soils and Sediments in Two watersheds in East Tennessee

ABSTRACTDetermining the total elemental concentrations of soils requires a total dissolution method, in which hydrofluoric acid (HF) is commonly used. However, this method is tedious and risky due to the dangerous reagent HF. This study compared a single acid extraction technique using a nitric acid (HNO3) extraction method to total dissolution (HF + microwave assisted aqua regia) for evaluating the total elemental concentrations in soils and sediments. The two methods were used to analyze the elemental content of soils and sediments from the Oostanaula Creek and Pond Creek watersheds in East Tennessee. Twenty-one elements (Al, Ba, Ca, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Nd, P, S, Si, Sr, Ti, V, Zn, and Zr) were subsequently measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The extraction efficiency for HNO3 relative to the total was compared and discussed. In general, HNO3 can extract the elements in absorbed phases and those residing in non-silicate minerals. Six elements (Ba, Co, Fe, Ca, Mn, and P) generated significant correlations between total and HNO3 in both OC and PC watersheds. Finally, the elements were grouped according to the interrelationships of their total elemental concentrations based on the dendrogram plots, suggesting their geochemical association in soils and sediment forming minerals.

Cadmium accumulation, translocation factor, and health risk potential in a wastewater-irrigated soil-wheat (Triticum aestivum L.) system

The accumulation of trace elements in wastewater-irrigated soils may introduce them to the food chain and therefore can threaten human health. The present study investigated the accumulation, translocation factor, and health risk potential of cadmium (Cd) in a soil-wheat system irrigated with treated wastewater compared with a reference soil (irrigated with fresh water). All treated wastewater-irrigated soils showed significantly higher levels of electrical conductivity (EC) than that of reference soil by 75–143%. Irrigation with treated wastewater increased both available and total Cd content in soil by 2–4 times. In all irrigated sites, Cd content was about twice as great as the maximum acceptable rate. Bioconcentration factor (BCF) and translocation factor (TF) indicated that Cd was mainly accumulated in the roots (BCF = 2.2–3.1), while little mobilization from roots to stems and grains was noted (TFshoot/root = 0.07–0.21; TFgrain/root = 0.18–0.24). The average hazard quotient (HQ) for different age groups of the population varied in the range of 0.1–1.0, implying low non-carcinogenic health risk of Cd to local wheat-consuming residents. The risk of Cd to cause carcinogenic health risk (CR) was in the range of 1 × 10-5 to 1 × 10-4, indicating low to moderate potential risk. CR for different age groups was in the order: individuals above 18 years old > individuals 7–18 years old > individuals 0–6 years old. For reducing potential health risks to local people, it is imperative to continuously monitor heavy metal levels in the wheat-soil system and urgently adopt more efficient managerial strategies to reduce Cd contamination.

Assessment of TPH and nickel contents associated with tolerant native plants in petroleum-polluted area of Gachsaran, Iran

The main aim of this study is to identify total petroleum hydrocarbons (TPHs) and nickel contents in soil as well as to evaluate the phytoremediation potential of native petroleum-resistant plants of Pazanan-E-Gachsaran (Iran). Firstly, soil samples were taken from depth of 0–30 cm in three ranges (0–500, 500–1000, and 1000–1500 m) from the center of pollution area of soil to outer part, and plant samples were taken by a linear transect from the same place. According to the results, there are 24 frequent species from 12 families in this region including Poaceae (25%), Asteraceae (20.83%), and Chenopodiaceae (12.50%). The results of initial soil test revealed that more distance from the core, leads to more decrease in the content of TPHs. Comparing total nickel content of soil showed a reduction trend from span (0–500 m) to 3 (1000–1500 m). The maximum nickel was found in the roots of Stipagrostis plumosa while lowest amount was observed in Cynodon dactylon. According to the frequency of Sipagrostis plumosa, Calotropis procera, and Sinapis arvensis, and their ability to resist in improper circumstances of the study area, these species were recognized as tolerant species that can be developed to decrease soil contamination of Pazanan. Therefore, they can be an appropriate choice for the phytoremediation of TPHs and nickel-contaminated soils.

Characteristics, sources, and in situ phytoremediation of polycyclic aromatic hydrocarbon in rural dumpsites

Without precaution to deal with gas emissions and leachate generation, dumpsites have become a severe environmental problem in many developing countries. The objectives of this study were to investigate the pollution status of polycyclic aromatic hydrocarbons (PAHs) in dumpsite soil in rural areas of China and to verify phytoremediation effectiveness with Sedum alfredii Hance and alfalfa (Medicago sativa L.) under complex pollution conditions in PAH-contaminated soil. In this study, we collected soil cores from four dumpsites in rural areas of North China (Hebei Province) for analysis, and correspondingly conducted an in situ phytoremediation experiment using Sedum alfredii Hance and alfalfa (Medicago sativa L.) at one of these sites, monitoring the total PAH concentration in soil. Results showed generally moderate pollution by PAHs in soil samples from dumpsites with pockets of heavy pollution. PAH concentrations in dumpsite soil ranged from 827 to 1101 ng/g (dry weight). High-molecular-weight PAHs were present in higher proportions at oldest dumpsite in operation. Certain molecular ratios of PAHs can be used to diagnose the source of PAHs in soil, and it indicated that the main sources were combustion of domestic coal and biomass, as well as the automobile exhaust and kitchen exhaust. A 17-month in situ phytoremediation experiment resulted in the effective removal of PAHs in the Sedum alfredii and alfalfa plots, with total PAH concentrations decreasing by 82.4% and 81.3%, respectively. Furthermore, PAH concentrations in plants correlated to plant growth conditions. This study indicated that the soils of the dumpsites were generally moderately polluted by PAHs, and some parts of the area were heavily polluted. Both Sedum alfredii and alfalfa absorbed PAHs from soil, and PAH concentrations in these two plants correlated to the growth conditions of the plants. Phytoremediation can effectively be used for PAH removal in open dumpsites.

Geographical variation in arsenic, cadmium, and lead of soils and rice in the major rice producing regions of China

Rapid industrialization and urbanization have accelerated the contamination of paddy soils with potentially toxic elements (PTEs). However, the status and the key factors responsible for the geographical variation in PTE concentrations in rice remain poorly understood. Here, a total of 113 pairs of soil and rice plant samples were collected from 19 provinces in four major rice producing areas of China to assess the geographical variation in total arsenic (As), cadmium (Cd) and lead (Pb) concentrations in the soil-rice system. Average total concentrations of As, Cd and Pb were 11.8, 0.45 and 25.7 mg kg−1, respectively, in the soils and 0.089, 0.087 and 0.036 mg kg−1 in the polished rice. The national maximum allowable concentrations of total soil As and Cd were exceeded in 6.19 and 33.6% of soils and that of Cd was exceeded in 7.96% of polished rice and no polished rice exceed the Pb limit. The As, Cd and Pb concentrations of rice were significantly and positively correlated (p < 0.05) with their corresponding soil available concentrations rather than with their soil total concentrations. Due to the combined effects of local rice varieties, cultivation of varieties with high Cd translocation factors and high Cd availability in acid soils, the highest rice Cd risk occurred in south China. The Cd concentrations in polished rice exceeded the maximum allowable by 4.0 and 15.8% in uncontaminated and contaminated soils, respectively. Results from 113 fixed samples may represent the actual current As, Cd and Pb status of rice in the main rice production areas nationally as they were very consistent with 574 random samples. In view of the high Cd contamination risk in acid soils of south China, countermeasures are needed to minimize Cd accumulation in rice crops in this region.

Polycyclic aromatic hydrocarbons (PAHs) contamination of soils and water around automobile repair workshops in Eket metropolis, Akwa Ibom State, Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are very toxic and persistent environmental contaminants. The paper is aimed at investigating the PAHs levels in soil collected at 0–30 cm depths from 5 automobile repair workshops within Eket metropolis/the underground water around its vicinity. The soils and water were prepared in the laboratory following standard procedures and were analysed for 16 US EPA priority PAHs using Gas Chromatography–Mass Spectrometer (GC–MS). Total PAHs concentrations in soil (Ʃ16 EPA PAHs) from all sampling sites were in the range of 0.82–12.98 mg/kg and 0.47–14.85 mg/kg for both dry and rainy seasons respectively and did not follow regular pattern with depth. Total PAHs concentrations in underground water from all sampling sites were in the range of 1.71–16.07 mg/l and 1.07–12.97 mg/l for both dry and rainy seasons respectively. According to European commission contamination classification and WHO maximum permissible limit for PAHs in drinking water (0.002 mg/l), the sites are said to be moderately to heavily contaminated. The total BaPeq for the soil and water samples indicated a moderate carcinogenic burden and hence low health risk. The calculated values obtained from diagnostic ratios shows that the PAHs in this study were from both pyrogenic and petrogenic sources. The correlation between total PAHs concentration in soil and water for both seasons indicated that the automobile repair activities had a moderate effect on the soil as well as the underground water around it. Therefore, boreholes should not be sited close to automobile repair yards to enable its suitability for domestic, irrigation and recreational usage.

Aridity and reduced soil micronutrient availability in global drylands.

Drylands cover more than 40% of terrestrial surface, and their global extent and socio-ecological importance will increase in the future due to the forecasted increases in aridity driven by climate change. Despite the essential role of metallic micronutrients in life chemistry and ecosystem functioning, it is virtually unknown how their bioavailability changes along aridity gradients at the global scale. Here we analysed soil total and available Cu, Fe, Mn, and Zn in 143 drylands from all continents, except Antarctica, covering a broad range of aridity and soil conditions. We found that total and available micronutrient concentrations in dryland soils were low compared to averages commonly found in soils of natural and agricultural ecosystems globally. Aridity negatively affected the availability of all micronutrients evaluated, mainly indirectly by increasing soil pH and decreasing soil organic matter. Remarkably, the available Fe:Zn ratio decreased exponentially as aridity increased, pointing to stoichiometric alterations. Our findings suggest that increased aridity conditions due to climate change will limit the availability of essential micronutrients for organisms, particularly that of Fe and Zn, which together with other adverse effects (e.g., reduced water availability) may pose serious threats to key ecological processes and services, such as food production, in drylands worldwide.

Assessment of crop growth, soil properties and crop yield in an upland acidic soil with inorganic fertilizer blended with organic amendments in summer rice cropping seasons

PurposeIntensification of rice cultivation to meet the growing demand has imbalanced the nitrogen level in soil. Amendments of inorganic fertilizers increase yield, but at the same time affects the environment. Hence, different amendments are to be investigated which acting sustainably on soil and the environment upholds yield gains.MethodsA study was carried out on acidic sandy loam soil in the irrigated summer seasons of the years of 2015–2016 and 2016–2017 to examine the effects of various amendments on rice growth, soil health and yield. The applied amendments were inorganic fertilizer blended with crop residues, farm yard manure and compost made of daily household green wastes.ResultsThe highest yield of 53.33 ± 2.09 Q/ha was recorded with application of inorganic fertilizer blended with compost and the lowest yield of 32.71 ± 3.09 Q/ha without amendment. Strong positive correlations were found between soil moisture and volumetric water content (0.982 at p < 0.001), manganese and copper (0.900 at p < 0.001), whereas available phosphorus and manganese showed a strong negative correlation (− 0.901 at p < 0.001). Performing stepwise regression analysis, yield was found affected mostly by soil moisture and total carbon out of evaluated 17 soil traits.ConclusionThe inorganic fertilization blended with the compost increased rice yield by 13.61% over inorganic fertilizer but a higher yield associated with compost demoted total nitrogen contents in soil, leading to lower soil nitrogen fertility and providing a negative feedback to sustainable agriculture. More research is required on compost development and application in different rice agroecosystems.

Transfer of naturally occurring radionuclides to wheat under laboratory controlled conditions

Knowledge of soil–plant transfer of naturally occurring radionuclides can be essential to assure an adequate radiological protection. Available data are mainly for anthropogenic radionuclides and biased for temperate climates. Wheat plantlets were grown using soil collected in Mediterranean regions and transfer factors, TF, for 234,238U, 226Ra, 210Po and stable elements (K, Na, Ca and Mg) were determined. U, Ra and Po were mainly located in roots. Calcium presented the highest TF values, whereas for radionuclides were much lower. Uranium TFs were correlated with total and exchangeable potassium concentration in soil. Calcium and radium TFs were correlated with total calcium concentration in soil.

Speciation, mobility and adsorption effects of various metals in sediments in an agricultural area surrounding an uranium ore deposit (Nisa, Portugal)

The availability and mobility of metals in soil strongly depend on its sediments geochemical forms and, therefore, the sediments’ particles composition evaluation is more meaningful than the estimation of total soil concentrations, particularly when risk and toxicity are under evaluation. The objective of the present study is to evaluate speciation, fractionation and mobility of the considered metals in sediment samples collected in the surrounding area of a very important unexploited uranium ore deposit located in the Alto Alentejo region of Portugal (Nisa). Sequential Extraction and analytical determinations using X-ray fluorescence technique of the tested materials allowed the determination of mobile fractions and the estimation of ionic speciation. Mobility factor for different elements was estimated, with some of them presenting high mobility rates for exchangeable ions and oxide fractions. The results evidence a high geochemical availability for U, Mo, Nb, Ca, Mn, and, in some particular cases for As, V and Cr. This availability is considerably lower for other elements such as Cu, Zn, Pb, Fe, Ba and Zr. Geochemically, regarding its form of occurrence, most of these metals are incorporated in the sediment matrixes as (oxide) secondary minerals and/or included in iron-exchangeable-oxyhydroxides precipitates. By contrast, binocular microscopy observations and Scanning Electron Microscopy analysis evidenced that U, As, Nb, Mo, and (but with less evidence) V and Cr, are adsorbed in iron-oxyhydroxides-clay minerals, being present as aggregates and as coatings at the surface of primary grains. It was possible to prospect that the majority of the more mobile metals, including uranium, probably occur as oxide or in secondary forms minerals being its origin related with weathering and dissolution of primary sources and subsequent transportation by local water courses in the dissolved fractions as hydrochemical solutes or included in colloids. Later, these metals precipitated as secondary forms and/or were adsorbed preferentially at the surface of the iron-oxyhydroxides-clay minerals precipitates.

Effect of Gypsum and Compost on Growth and Yield of Washington Navel Orange under Saline-Sodic Soils

INCREASING saline-sodic soils area as a result of climatic change, wrong agriculture practices and unsuitable of nutrition sources were lead to malnutrition and caused low productivity and quality of citrus. The study focused on gypsum and compost application in the proper rates for coping with such variable parameters. The trial carried out during 2017 and 2018 seasons on Washington navel orange trees (Citrus sinensis L., Osbek) grafted on sour orange (Citrus aurantium L.). Six application treatments were examined for the purpose of the study, i.e., T1: control, T2: compost at 10 tons / fed, T3: compost at 15 tons/ fed, T4: gypsum at 10 tons/ fed, T5: T4+T2 and T6: T4+T3. Field capacity (FC), Permanent wilting point (PWP), available water (AW), soil moisture and soil total content of NPK as indicators of soil parameter for application treatments were looked up. Growth parameters such shoot length, number of shoots/branch, number of leaves/shoot and leaf area, yield attributes such fruit set, fruit cracking, peel thickness, total tree yield (Kg), fruit juice volume, TSS, acidity, total sugars and vitamin C and leaf nutritional content of N, P, K, Ca and Mg were also determined. Results showed that T6 gave the highest results followed by T5, T4, T3 and T2 whereas T1 was the lowest ones for all parameters under investigations. The study aimed and recommends gypsum at 10 tons/ fed + compost at 15 tons/ fed for ameliorating saline-sodic soil and improving growth, yield and quality of Washington navel orange under such conditions.

Fit-for-purpose modelling of radiocaesium soil-to-plant transfer for nuclear emergencies: a review

Numerous radioecological models have been developed to predict radionuclides transfer from contaminated soils to the food chain, which is an essential step in preparing and responding to nuclear emergencies. However, the lessons learned from applying these models to predict radiocaesium (RCs) soil-to-plant transfer following the Fukushima accident in 2011 renewed interest in RCs transfer modelling. To help guide and prioritise further research in relation to modelling RCs transfer in terrestrial environments, we reviewed existing models focussing on transfer to food crops and animal fodders.To facilitate the review process, we categorised existing RCs soil-to-plant transfer models into empirical, semi-mechanistic and mechanistic, though several models cross the boundaries between these categories. The empirical approach predicts RCs transfer to plants based on total RCs concentration in soil and an empirical transfer factor. The semi-mechanistic approach takes into account the influence of soil characteristics such as clay and exchangeable potassium content on RCs transfer. It also uses ʻbioavailableʼ rather than total RCs in soil. The mechanistic approach considers the physical and chemical processes that control RCs distribution and uptake in soil-plant systems including transport in the root zone and root absorption kinetics.Each of these modelling approaches has its advantages and disadvantages. The empirical approach is simple and requires two inputs, but it is often associated with considerably uncertainty due to the large variability in the transfer factor. The semi-mechanistic approach factorises more soil and plant parameters than the empirical approach; therefore, it is applicable to a wider range of environmental conditions. The mechanistic approach is instrumental in understanding RCs mobility and transfer in soil-plant systems; it also helps to identify influential soil and plant parameters. However, the comlexity and the large amount of specific parameters make this approach impractical for nuclear emergency preparedness and response purposes.We propose that the semi-mechanistic approach is sufficiently robust and practical, hence more fit for the purpose of planning and responding to nuclear emergencies compared with the empirical and mechanistic approaches. We recommend further work to extend the applicability of the semi-mechanistic approach to a wide range of plants and soils.

Physicochemical and biochemical properties of an acid soil under potato culture amended with municipal solid waste compost

PurposeA field trial was conducted on a silty-loam soil under potato culture in NW Spain, to assess the effect of municipal solid waste (MSW) compost in a heavily fertilized acid soil.MethodsThree doses of compost (0, 30 and 60 Mg compost ha−1 soil) or inorganic fertilization (~ 140 N: 120 P2O5: 240 K2O kg ha−1 soil) were assayed. The effects of compost on soil physical, chemical (nutrient status and potentially toxic trace elements) and biochemical properties were evaluated after 1 and 5 months.ResultsCompost addition at the highest dose decreased bulk density and increased soil porosity and soil stability against water erosion. Soil pH, total organic C and N, cation exchange capacity and available P, Ca, Mg and K were also higher in compost-amended soils, whereas no effect on NH4+-N and NO3−-N was observed. Compost significantly increased soil microbial biomass and dehydrogenase activity. Due to the high nutrient status in the control soil, potato yield was not increased by compost or inorganic fertilization. A negative consequence of compost addition was the increased extractability of trace metals such as Zn, Cu, Pb and Ni, although their total concentrations in soil or in potato tubers did not increase with respect to the control.ConclusionsOverall, results show that positive effects of MSW compost can be expected even in rich soils that do not need fertilization for maintaining their productive function in the short-term. These positive effects prove the benefits of recycling urban wastes in agricultural soils as a sustainable way of waste management.

Lead, zinc, and copper redistributions in soils along a deposition gradient from emissions of a Pb-Ag smelter decommissioned 100 years ago

Sourcing and understanding the fate of anthropogenic metals in a historical contamination context is challenging. Here we combined elemental and isotopic (Pb, Zn, Cu) analyses with X-ray Absorption Spectroscopy (XAS) measurements (Zn) to trace the fate, in undisturbed soil profiles, of historical metal contamination emitted by a 167-year-old Pb-Ag smelter decommissioned 100 years ago located in the Calanques National Park (Marseilles, France). Lead isotopic measurements show that entire soil profiles were affected by 74 years of Pb emissions up to ~7 km from the smelter under the main NNW wind, and indicate particulate transfer down to 0.8 m at depth. This vertical mobility of anthropogenic Pb contrasts with previous studies where Pb was immobilized in surface horizons. The contribution of anthropogenic Pb to the total Pb concentration in soil was estimated at 95% in surface horizons, and 78% in the deepest horizons. Zinc isotopic signatures of past emissions that are enriched in light isotopes compared to the natural geological background (−0.70 ± 0.04‰ and −0.15 ± 0.02‰, respectively), were detected only in the surface horizons of the studied soils. Using XAS analyses, we showed that anthropogenic Zn was transformed and immobilized in surface horizons as Zn-Layered Double Hydroxide, thus favoring the enrichment in heavy isotopes in these surface horizons. No clear evidence of copper contamination by the smelter was found and Cu isotopes point to a bedrock origin and a natural distribution of Cu concentrations.

Pyrolyzed municipal sewage sludge ensured safe grain production while reduced C emissions in a paddy soil under rice and wheat rotation.

Safe recycling of the growing amounts of municipal sewage sludge containing toxic metals had been critically challenged with the fast urbanization. In this study, we investigated soil amendment of municipal wastewater treatment (MSS) converted biochar for its recycling in agricultural soils. In a field experiment, unpyrolyzed (USS) and pyrolyzed municipal sewage sludge (PSS) was amended at 20tha-1 on dry base to a rice paddy before rice plantation, with a control without amendment. Grain yield and emission of non-CO2 potent greenhouse gases were examined as well as topsoil metal mobility and plant uptake determined throughout a rice-wheat rotation year. Compared to USS treatment, addition of PSS caused a significantly increased grain yield of rice by 35% but no change in grain yield of wheat following the rice season. No distinct difference was observed in grain concentration of major nutrients of N, P, and K between USS and PSS treatments. Compared to USS treatment, PSS treatment reduced CH4 emissions by 91.6% from soil and by 78.5% from ecosystem during rice-growing season. Whereas, PSS treatment led to a reduction of ecosystem N2O emissions by 70.8% relative to USS treatment during wheat-growing season. While both USS and PSS treatments slightly but insignificantly increased soil total content of heavy metals, PSS treatment reduced CaCl2-extractable Cd pool by 33~40% over USS treatment. Grain contents of Cd and Pb and Cd/Zn were markedly reduced under PSS over USS, without exceeding the Chinese state guideline limit. Carbon emission intensity was considerably (by over 20%) reduced for soil and ecosystem but unchanged for wheat soil, under PSS over USS. Thus, soil amendment of pyrolyzed sewage sludge could be a measure for climate smart soil and for safe grain production in rice agriculture. It deserves further study if repeated amendment could exert sustainable impacts on soil health and food security in the paddy.

Influence of different organic geo-sorbents on Spinacia oleracea grown in chromite mine-degraded soil: a greenhouse study

Potentially toxic element (PTE) concentrations in mine-degraded soil and their bioaccumulation in food crops is a public health concern worldwide. The current study investigates the influence of organic geo-sorbents including biochar (B), farmyard manure (FYM), and peat moss (PTM) on PTE in chromite mine-degraded soil and their subsequent effects on spinach biomass, PTE uptake, average dietary intake (ADI), and health risk (HRI) associated with PTE via spinach consumption. Chromite mine-degraded soil samples were collected from different mining sites in Kohistan region. Pot experiments were carried out in the greenhouse environment. The selected geo-sorbents (B, FYM and PTM) were mixed at application rates of 1%, 2%, and 5%. Contaminated soil without geo-sorbents (control treatment) was also included in each batch of the experiments. Local FYM and PTM were used in this experiment, while B was provided by the Institute of Urban Environment (CAS) Xiamen, China. The total carbon (C), total nitrogen (N), and total sulfur (S) contents in mine-degraded soil and organic geo-sorbents were measured using a macro-elementor (VarioMax CNS, Germany). Total (acid digestion) and bioavailable PTE (As, Cd, Cr, Ni, Zn, and Pb) concentrations in mine-degraded soil and spinach were determined using inductive coupled plasma mass spectrophotometer (ICP-MS 7500 CX, Agilent Technologies, USA). The addition of organic geo-sorbents effectively immobilized the PTE concentrations in mine-degraded soil, and increased the major nutrient contents and thereby reduced the bioaccumulation of PTE (Cr, As, Ni, Cd, Zn, and Pb) in spinach. Consequently, B2, B5, FYM2, FYM5, PTM2, and PTM5 amendments significantly (p < 0.001) increased the biomass, whereas the B1, FYM1, and PTM1 addition showed no significant increase in spinach biomass as compared to the control treatment. The results showed that all the organic geo-sorbents had significantly (p < 0.001) reduced the As uptake in spinach, while B2, B5, FYM2, FYM5, and PTM5 significantly (p < 0.001) decreased PTE bioaccumulation as compared to the control treatment. The highest application rate (5%) showed the best result in increasing the spinach growth and biomass as well as reducing the PTE mobility in soil, and their bioaccumulation in spinach, as compared to 1% and 2% application rates and also with the control treatment. Furthermore, the average dietary intake (ADI) of PTE and health risk indices (HRIs) reduced via spinach consumption for both the children and adults, due to the addition of selected organic geo-sorbents used for soil amendments.

Occurrence of organophosphate flame retardants in farmland soils from Northern China: Primary source analysis and risk assessment

Ninety-eight soil samples were collected from farmland soils from Beijing-Tianjin-Hebei core area, Northern China, where agricultural lands were subjected to contamination from intense urban and industrial activities. Twelve organophosphates flame retardants (OPFRs) were analyzed with total soil concentrations ranging from 0.543 μg/kg to 54.9 μg/kg. Chlorinated OPFRs were dominating at mean level of 3.64 μg/kg and Tris(2-chloroisopropyl) phosphate contributed the most (mean 3.36 ± 5.61 μg/kg, 98.0%). Tris(2-ethylhexyl) phosphate was fully detected at levels of 0.041–1.95 μg/kg. Generally, tris(2-butoxyethyl) phosphate and triphenyl phosphate contributed the most to alkyl- (53.6%) and aryl-OPFRs (54.3%), respectively. The levels of ∑OPFRs close to the core urban areas were significantly higher than those from background sites. The occurrence and fate of OPFRs in soil were significantly associated with total organic carbon content and mostly with fine soil particles (<0.005 mm), and a transfer potential from the atmosphere was predicted with logKSA values. Comparable soil levels with poly brominated diphenyl ethers s in other studies suggested that the contamination of OPFRs occurred in farmland soil with an increasing trend but currently showed no significant environmental risk based on risk quotient estimation (<1). This investigation warrants further study on behaviors of OPFRs in a soil system and a continual monitoring for their risk assessment.

Qualitative and Quantitative Assessment of Hydrocarbons in Soil Profiles of Auto-Mechanic Workshop: A Case Study of Akure City, Nigeria

The total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbon (PAH) contents of soils collected at various depths (0–15 cm, 15–30 cm, and 30–45 cm) within automobile repair workshops in Akure metropolis, Nigeria were qualitatively and quantitatively assessed using gas chromatographic-mass spectrometer (GC-MS). Long chain n-alkanes (n C8–C32) were detected across all soils. TPH concentration (in mg/kg) for the top soils ranged from 85.42 ± 3.42 to123.76 ± 4.37. The middle had a concentration range of 63.45 ± 3.47–90. 80 ± 3.97 and a range of 12.59 ± 3.34–72.97 ± 3.97 recorded for the 30–45 cm depths measured. Similarly, the mean total PAHs concentrations in top, middle and bottom soils ranged from 0.14 to 0.21 mg/kg, 0.11 to 0.17 mg/kg, and <0.01 to 0.11 mg/kg respectively. Positive correlation in TPAH and particle sizes and organic carbon was recorded (R2 > 0.890). Partitioning of the more hydrophobic high molecular weight (HMW)-PAHs occurs to a greater extent (72–93%) compared with low molecular weight (LMW)-PAHs. The overall results showed that the soils of the area were highly contaminated and might be detrimental to living existence, through contamination of ground and surface water.