Nemerow Pollution Index Research Articles

Occurrence and distribution characteristics of heavy metals in the surface water of Yongding River Basin, China.

Yongding River is a vital socioeconomic zone in China in providing daily usage for humans, animals, and running of industries and agriculture. This study first provides a comparative assessment for the heavy metal pollution in the surface water from 82 estuarine locations along the basin, including the Guanting Reservoir and seven wastewater treatment plants (WWTPs). The occurrence, distribution, potential sources, and water quality relating to the detected heavy metals were addressed. Eleven typical elements (Pb, Cr, As, Cd, Sb, Ba, V, Ti, Zn, Ni, and Be) were investigated, and the results showed that all the measured concentrations were below the WHO guideline limits. Most heavy metals exhibited higher levels in the middle of Yongding River basin due to the discharge of WWTPs. Pb, Ti, Zn, and Cd in the surface water mainly originated from anthropogenic discharge, while Sb and V were mostly contributed to geogenic sources according to the principal component analysis. Three documented methods, water quality index (WQI), heavy metal pollution (HPI), and Nemerow pollution index (Pn) values, were used to evaluate the contamination monitoring of surface water. All the locations were classified as low and moderate risk except Y12, B2, and Y13 for their Pn values were higher than 1.0. The present study highlights the status of heavy metals in Yongding River basin which is helpful in providing fundamental data for assessment of water quality and the effective protection for Yongding River basin in the future.

Contaminants and heavy metals along the mangrove area of Dongzhai Harbor, China: distribution and assessment

In recent decades, higher-place shrimp ponds are prevalent in coastal areas of developing countries. However, shrimp aquaculture has a growing negative impact on mangrove wetland ecosystems. Mangroves located in Dongzhai harbor are under threat continuously of this commercialization. Therefore, a comprehensive analysis of contaminants and heavy metals is necessary for Dongzhai harbor, considering the mangrove area was declined and ecological services offered to the coastal communities with an insight for future restoration activities. In this study, pond effluents (Total Nitrogen (TN), Ammonia Nitrogen (AN), Total phosphorus (TP), Chemical Oxygen Demond (COD)) and heavy metals (Cd, Cu, Pb, Zn) were monitored in Dongzhai harbor yearly between 2013 and 2017. The results showed that the contents of Cd, Cu, Pb, and Zn were far lower than the standards. However, the main contaminants were organic matter and nitrogen. Maximum values of COD and TN were 26.10 mg·L−1 and 1.34 mg·L−1, respectively in 2017. Single factor index, Nemerow's pollution index, and Trophic level index revealed that the heavily polluted areas were Tashi and Sanjiang town.

Comprehensive evaluation of soil quality in a desert steppe influenced by industrial activities in northern China

Desert steppe soil security issues have been the focus of attention. Therefore, to understand the impact of industrial activities on the soil quality of desert grasslands, this experiment investigated the Gaoshawo Industrial Concentration Zone in Yanchi County. Based on the distance and direction from the industrial park, sample plots were established at intervals of 1–2 km. A total of 82 surface soil samples (0–20 cm) representing different pollution sources were collected. The samples were analysed for pH, total nitrogen, total phosphorus, available phosphorus, available potassium, organic matter, copper (Cu), cadmium (Cd), chromium (Cr), lead (Pb), and zinc (Zn). The desert steppe soil quality was analysed based on the integrated fertility index (IFI) and the Nemerow pollution index (PN), followed by the calculation of the comprehensive soil quality index (SQI), which considers the most suitable soil quality indicators through a geostatistical model. The results showed that the IFI was 0.393, indicating that the soil fertility was relatively poor. Excluding the available potassium, the nugget coefficients of the fertility indicators were less than 25% and showed strong spatial autocorrelation. The average values of Cu, Cd, Cr, Pb and Zn were 21.64 ± 3.26, 0.18 ± 0.02, 44.99 ± 21.23, 87.18 ± 25.84, and 86.63 ± 24.98 mg·kg−1, respectively; the nugget coefficients of Cr, Pb and Zn were 30.79–47.35%. Pb was the main element causing heavy metal pollution in the study area. Higher PN values were concentrated north of the highway in the study area, resulting in lower soil quality in the northern region and a trend of decreasing soil quality from south to north. The results of this research showed that the average SQI was 0.351 and the soil quality was extremely low. Thus, industrial activities and transportation activities in the Gaoshawo Industrial Zone significantly impact the desert steppe soil quality index.

Receptor model-based source apportionment and ecological risk of metals in sediments of an urban river in Bangladesh

Metal accumulation (As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) in Korotoa River sediment was studied in order to determine the metal content, distribution, sources, and their possible ecological impacts on the riverine ecosystem. Our study found significant spatial patterns of toxic metal concentration and principal coordinate analysis (PCoA) accounted for 45.2% of spatial variation from upstream to downstream. Metal contents were compared to sediment quality standards and found all studied metal concentrations exceeded the Threshold Effect Level (TEL) whereas Cr and Ni surpassed probable effect levels. All metal concentrations were higher than Average Shale Value (ASV) except Mn and Hg. The positive matrix factorization (PMF) and absolute principal component score-multiple linear regression models (APCS-MLR) were applied to identify promising sources of metals in sediment samples. Both models identified three potential sources i.e. natural source, traffic emission, and industrial pollution, which accounted for 50.32%, 20.16%, and 29.51% in PMF model whereas 43.56%, 29.42%, and 27.02% in APCS-MLR model, respectively. Based on ecological risk assessment, pollution load index (7.74), potential ecological risk (1078.45), Nemerow pollution index (5.50), and multiple probable effect concentrations quality (7.73) showed very high contamination of toxic metal in sediment samples.

Chemical speciation and risk assessment of heavy metals in biochars derived from sewage sludge and anaerobically digested sludge.

Dewatered sewage sludge (DSS) and anaerobically digested sludge (ADS) were pyrolyzed at 550 °C to investigate the characteristics of derived biochar and evaluate the risk of heavy metals (Cr, Ni, Cu, As, Cd, and Pb). The results showed that the pH value of the biochar derived from DSS (DSS-C) was slightly lower than that of the biochar derived from ADS (ADS-C), while DSS-C presented relatively higher specific surface area and total pore volume. DSS-C also showed higher H/C and lower O/C ratios than ADS-C, indicating a higher aromatic condensation and a lower polarity. Total concentrations of Cr, Ni, Cu, As, Cd, and Pb in DSS and ADS increased significantly after pyrolysis owing to the thermal decomposition of organic matter in the sludge, with corresponding rise of the Nemerow pollution index (NPI) of the biochars compared with the raw sludge. In addition, the sequential extraction procedure (BCR) analysis revealed that the pyrolysis process promoted the transformation of heavy metals from bio-available fractions to stable fractions. The potential environmental risk of heavy metals decreased from moderate and extremely high levels in the DSS and ADS to low risk and moderate levels in DSS-C and ADS-C after pyrolysis, respectively.

Spatial distribution, risk assessment, and source identification of pollutants around gold tailings ponds: a case study in Pinggu District, Beijing, China

This work investigated heavy metal and cyanide pollution in surface soils and edible plants around Yanzhuang gold tailings ponds in the region of Yanzhuang Village in Pinggu District, Beijing. Surface soil samples were collected from 33 sites around gold tailings ponds, and concentrations of seven heavy metals (i.e., Sb, As, Cd, Cu, Pb, Zn, and Hg) and cyanide were analyzed to determine their spatial distributions, pollution degrees, and sources. The potential ecological risks of As, Cd, Cu, Pb, Zn, and Hg were preliminarily assessed. The results showed that the mean cyanide, Sb, As, Cd, Cu, and Pb concentrations were higher than the standard values. The pollutant concentrations around the tailings ponds were high and decreased with increasing distance from the ponds. The single pollution index indicated that cyanide, As, and Cd were the main pollutants. The Nemerow pollution index revealed a large region and serious degree of heavy metal pollution in soils. The potential ecological risk level of the study area was moderate, with Cd and As posing the main risks. Multivariate statistical analysis suggested that the heavy metal and cyanide pollution present mainly derived from gold tailings, with agricultural pollution also had a certain effect. However, the 12 edible plants sampled were basically not polluted.

Recycled aggregates from construction and demolition waste as wetland substrates for pollutant removal

Large amounts of construction and demolition (C&D) waste have been generated due to the rapid urbanization process in China over recent decades. Hence, effective strategies for C&D waste reuse and recycling are urgently needed to reduce the impact of the generation of C&D waste. This work assessed the pollution control efficiency of recycled aggregates from C&D waste as substrates in vertical flow constructed wetlands (VFCWs) and the regeneration capability of these substrates. Six artificial experimental columns loaded with three recycled aggregates, namely, brick (RBA), concrete (RCA), and concrete-brick mixtures (C&B), and three natural aggregates, namely, limestone (LIM), lava rock (LAV), and zeolite (ZEO), were separately used. The results showed that recycled aggregates performed more effectively in terms of TP and COD removal than did natural aggregates, with the highest removal efficiency of 87.1% towards TP achieved by RCA and 74.9% towards COD achieved by C&B. Nemerow pollution index calculation demonstrated that the effluent water quality followed the order of RCA > C&B > RBA > LIM > ZEO > LAV. NH3–N, TP and COD removal efficiencies of 51.3%, 51.0% and 58.9%, respectively, were observed for RCA after in situ regeneration. The highest NH3–N and TP removal efficiencies were 54.7% and 84.8%, respectively, for RCA by aeration and NaOH washing, respectively, after four adsorption-desorption runs of ectopic regeneration. However, chemical regeneration of RCA and LIM severely destroyed the substrate structure over physical regeneration. Unfortunately, a low temperature led to a poor removal of TN in all systems, and the recycled aggregates from C&D waste were less resistant to impact than were the natural aggregates. Life cycle cost analysis showed that RCA as a substrate reduces the cost of wetland construction. This work provides a systematic comparison of recycled aggregates and natural aggregates as substrates in VFCWs in regard to their purification ability, regeneration methods and economic cost.

Interactive effects of natural and anthropogenic factors on heterogenetic accumulations of heavy metals in surface soils through geodetector analysis

The rapid socioeconomic development has led to severe pollution of urban soils by heavy metals. It is vital to identify and quantify the factors that affect trace-element pollution for better preventing and managing soil pollution. In this study, we collected 179 surface soil samples from Zhangzhou City in a coastal area of south China to determine the concentration of seven heavy metals (As, Cr, Cu, Hg, Ni, Pb, and Zn) and used the Nemerow Pollution Index (Pn) to estimate the level of heavy metal pollution in soils. Eighteen environmental factors, including six natural factors (e.g. soil properties, surface topography) and twelve anthropogenic factors (e.g. industry, road network, land use types and landscape pattern), were evaluated with the geodetector statistical method. The results indicate that the heavy metal contamination of soils in Zhangzhou City was highly heterogeneous. We found that the primary influencing factors for heavy metal concentrations were soil organic matter content, agriculture activities, and landscape pattern. Furthermore, the nonlinear relationship between the primary factors and their interaction factors enhanced soil contamination by the heavy metals. Among the anthropogenic factors, landscape pattern enhanced Pn the most when interacting with natural factor. In addition, the buffer zone should be considered when evaluating the effects of factors such as land use and landscape pattern, because the interactions between landscape pattern and slope aspect produce a maximum effect, accounting for 31.0% of the Pn value on the scale of 800 m. Based on this analysis, we identified the key factors of heavy metal pollution in the soils of Zhangzhou City and proposed strategic procedures for effective soil pollution prevention and treatment in the future.

Evaluation of the Pollution Status of Lagos Coastal Waters and Sediments, using Physicochemical Characteristics, Contamination Factor, Nemerow Pollution Index, Ecological Risk and Potential Ecological Risk Index

The heavy metals and physicochemical properties of Lagos coastal waters and sediments, Southwestern Nigeria were investigated in 5 stations (station 1-5), to determine their levels, distributions and pollution index. The observed ranges of physicochemical characteristics from the study area are: dissolved oxygen (DO): 2.15-11.3 mg/L; pH: 6-7.7; temperature (Temp): 28.05-29.25°C; biochemical oxygen demand (BOD): 1.6-110.1 mg/L; electrical conductivity (EC): 1.8-29.8 mS/cm; salinity (SAL): 0.02-2.05ppt; total dissolved solids (TDS): 211.8-1210.2 mg/L and total suspended solids (TSS): 12.13-117.95 mg/L. The analyzed physicochemical properties from all the stations are within the desired values for healthy marine ecosystems when compared with Federal ministry of environment (FMENV) Nigeria and World Health organization permissible limits (DO:>5 mg/L; pH:6.5-9; TEMP:<40°C; BOD: 50 mg/L; EC:900 mS/cm; TDS:1000mg/L and TSS:600 mg/L), with the exception of low DO at station 1 and station 5; and high BOD at; station 2 and station 3 respectively. The concentrations of heavy metals present in the water samples followed the sequence: Fe > Pb > Cu > Cr > Zn > Cd, and showed high values for Pb, Cd and Cr, relative to the standard permissible limits according to FMENV (Pb 0.001; Zn 50 mg/L; Cd < 0.0018; Cu 2-4 mg/L and Cr 0.02-2.0 mg/L). The calculated contamination factor (CF) in the sediment samples showed low-moderate contamination for the analyzed heavy metals (Cr, Zn, Cu and Pb), except for cadmium (Cd) that showed extremely severe contamination (CF > 6) values across the sampling stations. The calculated Nemerow pollution index (NPI) and ecological risk index (RI) showed heavily polluted (NPI > 10) values and very high ecological risk (RI > 380) values at Apapa (location 1), Iddo (location 2) and Makoko (location 3). The potential ecological risk factor (Eir) confirmed Cd as the highest polluted heavy metals (Eir >320), with the greatest potential threat to the marine ecosystems in the Lagos coastal waters. The study highlights the impacts of anthropogenic pollutions on the coastal ecosystems and human health.

Rapid monitoring of heavy metal pollution in lake water using nitrogen and phosphorus nutrients and physicochemical indicators by support vector machine

A novel method of predicting heavy metal concentration in lake water by support vector machine (SVM) model was developed, combined with low-cost, easy to obtain nutrients and physicochemical indicators as input variables. 115 surface water samples were collected from 23 sites in Chaohu Lake, China, during different hydrological periods. The particulate concentrations of heavy metals in water were much higher than the dissolved concentrations. According to Nemerow pollution index (Pi), pollution degrees by Fe, V, Mn and As ranged from heavy (2 ≤ Pi < 4) to serious (Pi ≥ 4). The concentrations of most heavy metals were the highest during the medium-water period and the lowest during the dry season. Non-metric Multidimensional Scaling Analysis confirmed heavy metal concentrations had slight spatial difference but relatively large seasonal variation. Redundancy Analysis indicated the close associations of heavy metals with nutrient and physicochemical indicators. When both nutrient and physicochemical indicators were used as input variables, the simulation effects for most elements in total and particulate were relatively better than those obtained using only nutrient or only physicochemical indicators. The simulation effects for As, Ba, Fe, Ti, V and Zn were generally good, based on their training R values of 0.847, 0.828, 0.856, 0.867, 0.817 and 0.893, respectively, as well as their test R values of 0.811, 0.836, 0.843, 0.873, 0.829 and 0.826, respectively; and meanwhile, in both the training and test stages, these metals also had relatively lower errors. The spatial distribution of heavy metals in Chaohu Lake was then predicted using the fully trained SVM models.

Assessment of Metals Concentrations in Soils of Abu Dhabi Emirate Using Pollution Indices and Multivariate Statistics.

The aim of this study was twofold. Firstly, we performed a land capability class determination of the agricultural soils from the Abu Dhabi Emirate, the United Arab Emirates, based on the concentrations of 17 chemical elements determined in the soil samples collected from 84 locations. Secondly, we assess the soil pollution with different metals, using several pollution indices. The results of Principal Component Analysis (PCA) shows that four principal components (PCs) are responsible for describing the total metals concentrations’ variance, the highest contribution on PC1 being that of Mn, and Cr, on PC2 that of Fe, on PC3 that of Cu, and on PC4 that of Al. After determining the optimal number of clusters, we classified the sites into three clusters, while the studied metals were grouped function on their concentrations. Then, we used five indices to assess the pollution level of the soil at the study sites and in the clusters. The geo—accumulation index (Igeo) indicates uncontamination/moderately contamination with Cu in cluster 1, uncontaminated/moderately contaminate soils with Cd, Cu, and Ni in cluster 2, and uncontaminated/moderately contaminated soil with Cu and moderately contaminated with Pb, Zn, and Ni in cluster 3. By comparison, the enrichment factors overestimate the pollution of the studied sites. The pollution load index (PLI) indicates a baseline level of pollution at 14 sites and the deterioration of the soil quality at four sites. The Nemerow pollution index provides similar results as PLI.

Contamination impact and human health risk in surface soils surrounding the abandoned mine of Zeïda, High Moulouya, Northeastern Morocco

The study assesses the levels of 16 heavy metals (HMs) in soils around the Zeida mine to provide information on the extent of contamination, the ecological risk of these HMs in soils, and the health risk to the residents of the Zeida village. Total metal concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS) for 20 sampling stations around the mining area. The average concentrations of HMs (mg/kg) in the study area were as follows: Ag (2.3), As (90.4), Ba (1605.1), Be (3.1), Co (11.2), Cr (57.6), Cu (33.9), Mn (499.6), Mo (6.1), Ni (23.4), Pb (1338.7), Sb (7.4), Se (1.3), Sn (11.3), Sr (596.5), and Zn (87.9). They were higher than those at the control sites. Twelve single and integrated ecological risk indices, namely Nemerow Pollution Index (PINemerow), Contamination degree (Cd), and Potential Ecological Risk (RI), were used and suggested that tailings and their nearby soils had a moderate to high contamination potential. Based on the US Environmental Protection Agency (USEPA), the carcinogenic risk, non-carcinogenic, hazard quotient (HQ), and hazard index (HI) were calculated with three routes: ingestion, inhalation, and dermal for children and adults. For both children and adults, HI for HMs was in the order: Mn > As > Co > Pb > 1 > other HMs. Mn, As, and Co were hazardous at 90% of soil sampling stations, while Pb was hazardous in tailings samples. The inhalation and dermal carcinogenic risks presented negligible to acceptable levels. The ingestion carcinogenic risk posed a significant issue for As, which tended to be serious for children at the majority of sampling sites.

Potentially toxic elements pollution in road deposited sediments around the active smelting industry of Korea

Potentially toxic elements (PTEs) were investigated in the different sizes of road deposited sediments (RDS) around the active smelting industry to understand their sources and to assess the pollution and ecological risk levels. The highest PTEs concentrations was shown near the raw materials import port and the smelting facilities. The fine particles of RDS showed extremely high PTEs concentrations. Zn has the highest mean concentration in the < 63 μm particle size of RDS, followed by Pb > Cu > As > Cr > Ni > Cd > Hg. The PTEs concentrations of this study were the highest values compared to the soils around the smelter and the RDS in urban and industrial areas in the world. This indicates that these PTEs pollution in RDS were mainly attributed to the transportation of raw materials for the smelting industry. According to nemerow pollution index calculation, RDS at all sampling sites with particles of less than 250 mm was seriously polluted with PTEs. The ecological risk was also found to be very high in all RDS fractions and highly toxic elements such as Cd, Pb and Hg pose extremely risk. Given the total amounts PTEs in the road surface, it is necessary to apply RDS removal management plan to reduce the PTEs pollution.

An integrated migration and transformation model to evaluate the occurrence characteristics and environmental risks of Nitrogen and phosphorus in constructed wetland

In this study, an integrated migration and transformation (IMT) model based on microbial action, plant absorption, sediment release and substrate adsorption was firstly established to evaluate the temporal-spatial distribution of N and P in Lingang hybrid constructed wetland (CW), Tianjin. Compared to the conventional transformation model that only considers the microbial action, the IMT model could accurately predict the occurrence characteristics of N and P. In Lingang CW, NO3−-N (0.56–3.63 mg/L) was the most important form of N, and the TP was at a relatively low concentration level (0.04–0.07 mg/L). The spatial distribution results showed that a certain amount of N and P could be removed by CW. Form the temporal perspective, the N and P concentrations were greatly affected by the dissolved oxygen (DO). The simulated values obtained by IMT model indicated that the distribution of N and P was more affected by the temporality compared with the spatiality, which was consistent with measured values. Besides, the PCA indicated that TN, NO3−-N and DO were important factors, which affected the water quality of CW. The Nemerow pollution index method based on the simulated values indicated that Lingang CW was overall moderately polluted, and the subsurface area was the main functional unit of pollutants removal in CW. This work provides a new model for accurately predicting the occurrence characteristics of N and P pollutants in CW, which is of great significance for identifying its environmental risks and optimizing the construction of wetlands.

Land use assessment using indices of heavy metal contamination in soils from intensive agricultural areas

Soil contamination by heavy metals is often caused by industrial and agricultural activities, which directly affects environment quality and food safety, especially for farmlands. To develop indicators for making proper decisions regarding land use, the Soil Heavy Metal Contamination Evaluation System including the Single Pollution Index (Pi), the Nemerow Pollution Index (PINemerow), the Potential Ecological Risk Index (RI), and the Contamination Severity Index (CSI) was developed using data from 499 samples collected from an area of 2017 km2. A risk assessment zoning solution based on PPRC (the Soil Heavy Metal Contamination Evaluation System including Pi, PINemerow, RI and CSI) was proposed, and the study area was mapped for four risk assessment zones as follows: no risk zone, very low risk zone, low risk zone, and intermediate risk zone. Four land use strategies (priority protection, protection, comprehensive monitoring, and warning and control) were proposed. Generally, the risk assessment zoning solution based on PPRC-defined minimizes the potential ecological risk to the land for the scientific evaluation of heavy metal pollution in areas of intensive agricultural activity.

Pollution, human health risk assessment and spatial distribution of toxic metals in urban soil of Yazd City, Iran

Heavy metal pollution significantly reduces the quality of the environment and threatens human health, especially in industrial cities. This study investigated toxic metals concentrations, pollution levels and human health risks assessment of urban soils in Yazd City, as an industrial city in center of Iran. Soil surface samples (0-10cm) were collected from 30 points in the area for geochemical analysis. The concentrations of heavy metals were determined using an inductively coupled plasma mass spectrometry (ICP-MS). The values of the mean concentrations of toxic metals (mg kg-1) in the urban soils decrease in the order of Zn (83.9) > Pb (34.5) > Cr (32.6) > Cu (23.5) > Ni (23.4) > As (5.86) > Co (4.86) > Cd (0.27). The mean concentration of Zn, Pb, As and Cd elements was higher than the background and the crust values. A pollution assessment by Geo-accumulation Index (Igeo), Pollution Index (PI), Contamination Degree (CD), the Integrated Pollution Index (IPI), the Pollution Load Index (PLI) and Integrated Nemerow Pollution Index (INPI) showed that As, Cd and Pb were moderately enriched and the study area polluted considerably by these toxic metals. Based on PI results, 88.9% of the urban soil samples highly polluted by As. Overall, the quality of the urban soil in Yazd City is clearly affected by toxic metals. Due to the prevailing wind direction, the route of the north-south highway of Iran and the population density and traffic of the northwestern and southern areas of the study area were found the highest level of pollution indicators (IPI > 1.8; LPI > 1.3; CD > 15 and INPI > 4.3). The results of Pearson correlation analysis indicated that all pollution evaluation indicators were influenced by As and Cu, and showed high significant correlation with these two elements, while neither of them had a significant relationship with Pb and was found also a weak link statistically with Cd. Health risk assessment of toxic metals has been performed in both carcinogenic and non-carcinogenic sectors. The results indicate that oral intake is the main pathway that toxic metals can harm human health for both the child and adults. The carcinogenic risks (RI) of adults and child by toxic metals were as follows: Ni > Pb > Cr > As > Cd. Hazard quotients (HQ) and hazard index (HI) values for child also were higher than these for adults. Generally, the results demonstrated that the potential carcinogenic health risks for adults of toxic metals were in an acceptable range in study area, whereas for Cr, Ni and Pb with RI > 10-4, the risk of cancer in child probably increases.

Environmental Risk Assessment of Coal-Ash-Amended Soil Based on Continuous Planting of Pakchoi

The agricultural application of coal ash which contains a variety of chemical nutrients may also cause heavy metal pollution of crops and soil. In this study, pakchoi was cultivated for four consecutive seasons in pots of brown soil amended with fly ash or bottom ash. With subsequent plantings, the total concentrations in the four fractions of Pb, Cr and Cu decreased, while the concentrations of Pb, Cr and Zn dissolved in acetic acid increased. The lowest fresh weight of pakchoi were seen when 15% fly ash was applied. The edible parts of pakchoi contained more heavy metals than the roots. Calculating the Nemerow Pollution Index (NPI) according to the Environmental Protection Standards, the risk of heavy metals in coal ash-amended soils was low. With subsequent plantings, the Risk Assessment Code (RAC) of Pb, Cr and Zn increased gradually and Zn eventually reached a medium level. The study confirmed that coal ash had phytotoxic effects on pakchoi and application of coal ash confered a risk of soil pollution.

Implications of the Phytoremediation of Heavy Metal Contamination of Soils and Wild Plants in the Industrial Area of Haina, Dominican Republic

The study evaluates pollution by Pb, Zn, and Cr, and a possible sustainable solution through phytoremediation technologies, in the surroundings of Haina, a very polluted area of the Dominican Republic. Soils and plants were analyzed at 11 sampling points. After sample processing, the elemental composition was analyzed by ICP-OES. Soil metal concentrations, contaminating factors, pollution load indexes, and the Nemerow pollution index were assessed. Soil metal concentrations showed Pb &gt; Zn &gt; Cr, resulting in very strong Pb pollution and medium-impact Zn pollution, with an anthropogenic origin in some sites. This means that some agricultural and residential restrictions must be applied. Accumulation levels in plant tissues, bioaccumulation factors in roots and shoots, and translocation factors were determined for Acalypha alopecuroidea, Achyranthes aspera, Amaranthus dubius, Bidenspilosa, Heliotropium angiospermum, Parthenium hysterophorus, and Sida rhombifolia. The vast majority of the plants showed very low levels of the potentially toxic elements studied, although it may be advisable to take precautions before consumption as they are all considered edible, fodder, and/or medicinal plants. Despite their low rate of bioaccumulation, most of the plants studied could be suitable for the application of phytoremediation of Zn in the field, although further studies are needed to assess their potential for this.

MgO-laden biochar enhances the immobilization of Cd/Pb in aqueous solution and contaminated soil

Great progress has been made in recent years to alleviate the heavy metal pollution, but the development of low-cost and eco-friendly adsorbents is still challenging. In this work, MgO-loaded biochar, as a potential adsorbent, was successfully synthesized via copyrolysis of corn straw and MgCl2∙6H2O at 600 ℃ and used for heavy metal immobilization in aqueous solution and contaminated soil. Nemerow pollution index and potential ecological risk index methods were also used to assess the potential ecological risk of the metals in soil after remediation. The results showed MgO-laden biochar exhibited a much higher Cd2+ adsorption capacity than the pristine biochar. Pseudo-second-order and Langmuir/Langmuir–Freundlich equations could describe the adsorption kinetics and isotherm of Cd2+ well. The maximum adsorption capacity of Cd2+ could reach to 1058.8 mg g−1 estimated by Langmuir–Freundlich equation. Cd2+ adsorption on MgO-laden biochar composite mainly involved the hydrolyzation of MgO, ionization of Mg(OH)2 and precipitation of Cd2+ and OH−. In addition, complexes with oxygen-containing groups and adsorption by Mg(OH)2 also enhanced Cd immobilization. The result of soil-leaching test showed that the concentrations of TCLP-leaching (Toxicity Characteristic Leaching Procedure) Cd and Pb reduced by 22.4% and 29.0%, respectively, after 4% of MgO-laden biochar amendment, and the integrated pollution index and potential ecological risk decreased by 28.9% and 28.5%, respectively. These results suggest that MgO-laden corn straw biochar may be promising for application as a low-cost adsorbent for wastewater treatment and soil remediation.

Determination of background values and assessment of pollution and ecological risk of heavy metals in urban agricultural soils of Yaoundé, Cameroon

Presence of heavy metals in urban agriculture is considered a major ecological risk. The aim of this research is to determine concentrations and background values of heavy metals in urban agricultural soils in Yaounde (Cameroon), in order to assess the degree of soil pollution and to evaluate ecological risk. Forty-five composite soil samples were taken from three market garden sites. Heavy metals (Cd, Cr, Cu, Mn, Ni, Pb and Zn) were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). Geochemical background threshold values (GBTV) were determined using the robust statistical method of median ± median absolute deviation (MAD). Single (geoaccumulation index and enrichment factor) and complex (pollution load index and Nemerow pollution index) indices of pollution and of ecological risk (potential ecological risk index) were calculated. Significant difference between the three market garden sites was evaluated using the nonparametric test of Kruskal–Wallis. Median concentrations varied considerably, ranging from the highest to the lowest levels (mg/kg) as Mn 259.0 > Cu 111.2 > Zn 81.9 > Cr 54.6 > Pb 19.3 > Ni 14.9 > Cd 0.1. All median values were below their corresponding geochemical backgrounds, except for Pb. Single pollution indices showed that the study site was contaminated with Pb. Nemerow pollution index showed that 60% of soil samples were in the very high level of pollution. Based on potential ecological risk index, 16% of soil samples were at high risk. The three market garden sites differed significantly regarding their heavy metal contents, except Cd, as well as their pollution and ecological risk indices with the Nkolondom site having, in general, the highest levels. More than half of the study area is polluted, mainly with Pb, whereas ecological risk is limited to a small part of it. This study can be used as a baseline to develop future long-term risk assessment strategies on the potential migration of heavy metals in urban agricultural soils to vegetables, animals and human beings.