Building a quality index for soils impacted by proximity to an industrial complex using statistical and data-mining methods

Quantitative tracing the sources and human risk assessment of complex soil pollution in an industrial park

Pollution in industrial parks has long been characterized by complex pollution sources and difficulties in identifying pollutant origins. This study focuses on a typical industrial park consisting of 11 factories (F1-F11) including organic pigment, inorganic pigment, and chemical factories in Hunan Province, China, here, a total of 327 sample points were surveyed. Eight pollutants (Mn, Cd, As, Co, NH3-N, l, 1,2-Trichloroethane, chlorobenzene, and petroleum hydrocarbons) were classified as contaminants of concern (COCs). This study assessed the contributions of driving factors to the distribution of COCs in the soil. Pollutant source apportionment was conducted using positive matrix factorization (PMF) and random forest (RF). The results revealed that the main factors driving pollution are groundwater migration, non-compliant emissions, leaks during production, and interactions among pollutants. The primary pollution sources were four chemical factories and an inorganic pigment factory. Source 5 demonstrates significant correlations with TCA (29.6%), CB (30%), and As (31.6%). Two chemical factories (F7 and F10) are the most significant pollution source with a risk assessment contribution rate of more than 60%. The present study sheds some light on the contamination characteristics, source apportionment and source-health risk assessment of COCs in industrial park. By utilizing the proposed research framework, decision-makers can effectively prioritize and address identified pollution sources.

In-situ remediation of cadmium contamination in paddy fields: from rhizosphere soil to rice kernel

Cadmium (Cd) has become an important heavy metal pollutant because of its strong migration and high toxicity. The industrial production process aggravated the Cd pollution in rice fields. Human exposure to Cd through rice can cause kidney damage, emphysema, and various cardiovascular and metabolic diseases, posing a grave threat to health. As modern technology develops, the Cd accumulation model in rice and in-situ remediation of Cd pollution in cornfields have been extensively studied and applied, so it is necessary to sort out and summarize them systematically. Therefore, this paper reviewed the primary in-situ methods for addressing heavy metal contamination in rice paddies, including chemical remediation (inorganic-organic fertilizer remediation, nanomaterials, and composite remediation), biological remediation (phytoremediation and microbial remediation), and crop management remediation technologies. The factors that affect Cd transformation in soil and Cd migration in crops, the advantages and disadvantages of remediation techniques, remediation mechanisms, and the long-term stability of remediation were discussed. The shortcomings and future research directions of in situ remediation strategies for heavily polluted paddy fields and genetic improvement strategies for low-cadmium rice varieties were critically proposed. To sum up, this review aims to enhance understanding and serve as a reference for the appropriate selection and advancement of remediation technologies for rice fields contaminated with heavy metals.

Edaphic properties as pieces of evidence of tailings deposit on soils

Mine tailings are one of the primary contaminant sources of heavy metals and metalloids in the soil. Besides increasing the concentration of potentially toxic elements (PTEs), tailings may modify the edaphic conditions and decrease the buffer capacity of impacted soils. The influence of tailings may reach distances far from the impoundments depending on the transport path and the specific transport mean: air, rain (runoff and infiltration), or acid mine drainage. In this study, soil samples from various horizons were collected in trial pits along a transect, at different distances from sulfide tailings. Soil analysis included texture, organic matter, alkalinity, porous space, carbonates, pH, electrical conductivity, real density, apparent density, total sulfur, main mineralogy, and total concentrations of As, Cd, Pb, Fe, and Zn. Graphical and statistical interpretation of the results showed that real density and porous space are the leading indicators of the tailings dispersion and accumulation and that pH is not a significant parameter (all values were above the neutrality) due to the limestone abundance in the area. However, Zn and Cd concentrations had an inverse relation with pH. Differences in the concentrations of PTEs between the superficial and deep layers that increased toward the tailings were also observed. Gypsum was only present in the closest samples to the tailings and may also be an indicator of tailings' influence on soils. This study allowed us to identify general edaphic parameters as a first and quick means to determine the tailings contamination of soils.

Determination of Soil Quality Index of agricultural land adjacent to industrial sites of Jamuria C.D.Block, Paschim Bardhaman District, West Bengal

A healthy soil is crucial for food security, but human activities, particularly industrialization, are degrading the soil's quality. This study aims to assess and compare the Soil Quality Index (SQI) at three industrial sites: the iron and steel industry, the open cast coal mining industry, and the brick kiln industry, along with a control field. To measure the SQI, the weighted additive method was applied to the nine selected physico-chemical properties of soil: soil temperature, soil moisture, Bulk Density, pH, N, P, K, OC, and EC. Principal Component Analysis coupled with multiple correlation methods was used to determine the Minimum Data Set. The most dominant factors near the iron and steel industrial site are soil temperature, N, K, and EC, while N, OC, soil moisture, P, K, and EC are the most significant factors near the open cast coal mine. In the case of the brick kiln industrial site, soil moisture, OC, K, soil temperature, and P have the highest loadings. The calculated SQI indicates that the quality of soil is in better condition in the control field (0.6475), while the soil adjacent to the coal mining industrial site (0.1426) is in the worst state, followed by the iron and steel industrial site (0.1611) and the brick kiln industrial site (0.289). To attain sustainable agricultural practices in industrial landscapes, efficient management of nutrient contents and phytoremediation can be helpful.

Mobility, bioaccumulation in plants, and risk assessment of metals in soils

Heavy metal contamination of soils is one of the main factors contributing to soil quality decline and loss of biodiversity, which is also associated with plant contamination, as metals accumulate in the surface layer of soils and then enter the trophic chain. The aims of the study were to assess the mobility and bioavailability of metals in soils to plants, and to estimate the ecological and health risks associated with heavy metal content in soils. 320 topsoil and 206 plant samples were collected. Fractional analysis showed that for most of the samples, there was no or low risk associated with the mobility of Cr, Pb, Cu, Ni, Zn, and low and medium for Cd. High and very high metal release risk was only shown for Cd (28 % of samples), and Zn and Pb (2 % of samples). The bioaccumulation factor found moderate levels of accumulation for Cd, Zn, Cu, Ni. High accumulation of Cd and Zn was found in 38 % and 15 % of plant samples. Alivibrio fischeri proved to be a more sensitive indicator of soil ecotoxicity compared to Sinapis alba. In the 81 % of the soil samples found a low probability of adverse effects on ecological receptors associated with exposure to soilborne metals. In the case of human health risk, no harmful health effects were observed due to accidental ingestion of metal-containing soils in the study area. In assessing metal risks, the choice of indicators is crucial. Moreover, the properties of soils have a significant impact on the mobility of metals and their bioaccumulation by plants. This means that the more varied the choice of indicators, the more comprehensive, reliable and close to reality the risk assessment of heavy metals in soils will be.

Ecological assessment of soil contamination by heavy metals affected in the past by the lead-zinc mining and processing complex in Kentau, Kazakhstan

Polymetallic ore processing plants are serious sources of heavy metal pollution. The present study examined the degree of pollution of surface soils with the metals zinc, cadmium, lead, and copper in the single-industry town of Kentau, Kazakhstan, where an enterprise for the processing of lead-zinc ore has been operating for a long time. This enterprise ceased operations in 1994, and this study may be of interest in terms of assessing the current ecological state of urban soils after a 27-year period of possible soil self-cleaning processes. The study showed that the surface soils of Kentau retain fairly high concentrations of metals. The maximum detected concentrations of zinc, cadmium, lead, and copper were 592 mg/kg, 1.651 mg/kg, 462 mg/kg, and 82.5 mg/kg, respectively. According to the classification of the geoaccumulation index, the soils of the town belong to pollution classes II, III, and IV with moderate and strong pollution. The calculated potential ecological risk factor indicates that cadmium poses a considerable potential ecological risk, while lead showed a moderate ecological risk. In general, according to the obtained values of potential ecological risk factors, metals can be arranged in the following order: Cd > Pb > Zn > Cu. In this study, a five-step sequential extraction procedure by the method of A. Tessier was used, and the mobility factors of metals were calculated. Based on the data obtained, it was found that cadmium and lead have the highest mobility and, consequently, availability for biota in modern conditions, which may pose a potential risk to public health in the town.

Identification of the factors determining the concentration and spatial distribution of Zn, Pb and Cd in the soils of the non-forest Tatra Mountains (southern Poland)

We investigated trace-metal (TM)--Zn, Pb and Cd--concentrations and spatial distributions in the uppermost layers of non-forest soils from Tatra National Park (West Carpathians). We aimed to determine the main factors affecting the distribution of TMs, as well as the risk they posed to the environment. TM concentrations were compared to the target and intervention values established by the Dutch Ministry. Principle component analysis was used to identify the potential factors affecting TM accumulation, with two-factor analysis being applied to further examine the importance of any given factor. To examine the regularity of the TM distribution, semivariograms were created. The semivariograms of Cd and Pb were similar, suggesting a moderate spatial dependence for these metal concentrations, while the Zn variogram indicated a lack of spatial continuity for this metal. We established that the Zn, Pb and Cd exceeded target levels and at some sites, Cd exceeded the intervention values, posing a strong ecological risk to the environment. Our study confirmed that the parent rock was the most important factor affecting the TM accumulation. The carbonate-free soils differed from carbonate soils in the second important factor affecting TM accumulation, for carbonate-free soils it was location when for carbonate soils-TM content in the parent material. The Zn, Pb and Cd distribution patterns indicated that Cd, but also to a lesser degree Pb and Zn, accumulation mainly resulted from long-range transport from industrialised areas, while the Zn concentrations were also affected by local sources, such as the historical mining of Zn ore.

Assessment of biotoxicity of three types of landfilled foundry waste on the basis of dehydrogenase activity

The microbiological activity of three types of landfilled foundry wastes, i.e. biologically reclaimed foundry waste (BFW), foundry waste landfilled since the 1990s (LFW) and fresh foundry waste (FFW), was investigated. The wastes originated from a Polish iron and steel foundry which uses organic binders based on phenol-formaldehyde resins and mineral binders to casting production. The physical and chemical properties and dehydrogenase activity (DHA) were determined in the waste samples and local soils. In addition, a pot experiment was performed to determine the effect of the addition of FFW with no microbial activity on soils. Additional correlation analysis was conducted between DHA and other parameters. It was found that biologically reclaimed foundry waste (BFW) showed the highest microbial activity, similar to soils from garden allotments and agricultural fields. The DHA in LFW was about a half lower than BFW. On the other hand, FFW did not show any microbial activity. A pot experiment showed that increasing the percentage of foundry waste relative to soil had a negative effect on DHA, probably as a result of soil dilution rather than the inhibitory effect of contaminants. It was concluded that the optimum addition of FFW to soils is 10% wt, due to the highest value of DHA among the other variants.

Changes in Soil Physico-Chemical and Microbiological Properties During Natural Succession: A Case Study in Lower Subtropical China

Vegetation succession can change the function and quality of the soil. Exploring the changes in soil properties during secondary forest restoration is of great significance to promote forest restoration and improve the ecological service function of subtropical ecosystems in South China. In this study, we chose three typical forests in subtropical China as restoration sequences, broadleaf-conifer mixed forest (EF), broad-leaved forest (MF), and old-growth forest (LF), to study the changes in soil physico-chemical and biological properties and the changes of soil comprehensive quality during the secondary succession of subtropical forest. The results showed that the soil physical structure was optimized with the progress of forest succession. The soil bulk density decreased gradually with the progress of forest restoration, which was significantly affected by soil organic carbon (p < 0.01). In LF, the soil moisture increased significantly (p < 0.05), and its value can reach 47.85 ± 1.93%, which is consistent with the change of soil porosity. With the recovery process, soil nutrients gradually accumulated. Except for total phosphorus (TP), there was obvious surface enrichment of soil nutrients. Soil organic carbon (15.43 ± 2.28 g/kg), total nitrogen (1.08 ± 0.12 g/kg), and total phosphorus (0.43 ± 0.03 g/kg) in LF were significantly higher than those in EF (p < 0.05). The soil available nutrients, that is, soil available phosphorus and available potassium decreased significantly in LF (p < 0.05). In LF, more canopy interception weakened the P limitation caused by atmospheric acid deposition, so that the soil C:P (37.68 ± 4.76) and N:P (2.49 ± 0.24) in LF were significantly lower than those in EF (p < 0.05). Affected by TP and moisture, microbial biomass C and microbial biomass N increased significantly in LF, and the mean values were 830.34 ± 30.34 mg/kg and 46.60 ± 2.27 mg/kg, respectively. Further analysis showed that total soil porosity (TSP) and TP (weighted value of 0.61) contributed the most to the final soil quality index (SQI). With the forest restoration, the SQI gradually increased, especially in LF the value of SQI was up to 0.84, which was significantly higher than that in EF and MF (p < 0.05). This result is of great significance to understanding the process of restoration of subtropical forests and improving the management scheme of subtropical secondary forests.