Using the compound system to synthetically evaluate the enrichment of heavy metal(loid)s in a subtropical basin, China

Integrated application of multiple indicators and geographic information system-based approaches for comprehensive assessment of environmental impacts of toxic metals-contaminated agricultural soils and vegetables

Conventional monitoring and mapping approaches are laborious, expensive, and time-consuming because they need a large number of data and consequently extensive sampling and experimental operations. Therefore, due to the growing concern about the potential of contamination of soils and agricultural products with heavy metals (HMs), a field experiment was conducted on 77 farm lands in an area of 2300 ha in the southeast of Shiraz (Iran) to investigate the source of metal contamination in the soils and vegetables and to model spatial distribution of HMs (iron, Fe; manganese, Mn; copper, Cu; zinc, Zn; cadmium, Cd; nickel, Ni, and lead, Pb) over the region using geographic information system (GIS) and geostatistical (Ordinary Kriging, OK) approaches and compare the results with deterministic approaches (Inverse Distance Weighting, IDW with different weighting power). Furthermore, some ecological and health risks indices including Pollution index (PI), Nemerow integrated pollution index (NIPI), pollution load index (PLI), degree of contamination (Cdeg), modified contamination degree (mCd), PIaverage and PIvector for soil quality, multi-element contamination (MEC), the probability of toxicity (MERMQ), the potential ecological index (RI), total hazard index (THI) and total carcinogenic risk index (TCR) based on ingestion, inhalation, and dermal exposure pathways for adults and children respectively for analyzing the noncarcinogenic and carcinogenic risks were calculated. Experimental semivariogram of the mentioned HMs were calculated and theoretical models (i.e., exponential, spherical, Gaussian, and linear models) were fitted in order to model their spatial structures and to investigate the most representative models. Moreover, principal component analysis (PCA) and cluster analysis (CA) were used to identify sources of HMs in the soils. Results showed that IDW method was more efficient than the OK approach to estimate the properties and HMs contents in the soils and plants. The estimated daily intake of metals (DIM) values of Pb and Ni exceeded their safe limits. In addition, Cd was the main element responsible for ecological risk. The PIave and PIvector indices showed that soil quality in the study area is not suitable. According to mCd values, the soils classified as ultra-high contaminated for Cu and Cd, extremely high for Zn and Pb, very high, high, and very low degree of contamination for Ni, Mn, and Fe, respectively. 36, 60, and 4 % of the sampling sites had high, medium, and low risk levels with 49, 21, and 9 % probability of toxicity, respectively. The maximum health risk index (HRI) value of 20.42 with extremely high risk for children was obtained for Ni and the HI for adults and children were 0.22 and 1.55, respectively. The THI values of Pb and Cd were the highest compared to the other HMs studied, revealing a possible non-cancer risk in children associated with exposure to these metals. The routes of exposure with the greatest influence on the THI and TCR indices were in the order of ingestion > inhalation > dermal. Therefore, ingestion, as the main route of exposure, is the route of greatest contribution to health risks. PCA analysis revealed that Fe, Mn, Cu, and Ni may originate from natural sources, while Fe was appeared to be controlled by fertilizer, and Cu primarily coming from pesticide, while Cd and Pb were mainly associated with the anthropogenic contamination, atmospheric depositions, and terrific in the urban soils. While, Zn mainly originated from fertilization. Findings are vital for developing remediation approaches for controlling the contaminants distribution as well as for monitoring and mapping the quality and health of soil resources.

Heavy metal pollution and risks in a highly polluted and populated Indian river-city pair using the systems approach

A sectorial approach for assessing heavy metal pollution in rivers neglects the inter-relationship between its environmental compartments and thus fails to report realistic pollution status and associated ecological and human health risks. Therefore, a systems approach was adopted to assess heavy metal pollution and associated risks in the Yamuna River (Delhi, India), one of the world's most polluted and populated river-city pairs. Sampling sites selected along the river with distinct land use were uncultivated natural floodplain vegetation, marshy area, invasive community, arable land, and human settlements. The multivariate analysis identified sources of pollutions (Pb, Cd, Cr, and Ni [anthropogenic]; Fe and Zn [geogenic]). Across the land use, a high log K_p value of Zn and Pb in water-soil phase than in water-sediment phase indicates their long-range transfer, whereas low log K_p (water-soil) of Cd suggests river sediments as its reservoirs. Comparison of pollution indices of Cd, Cr, and Pb in water, sediment, and soil across the land use suggested the role of vegetation in reducing pollution in the environment. Ecological risk also gets reduced progressively from water to sediment to the soil in naturally vegetated sites. Similarly, in river water, Cr, Cd, Ni, and Pb pose carcinogenic and non-carcinogenic risks to adults and children, which are also reduced in sediments and soil of different vegetation regimes. This study showed the eco-remediation services rendered by natural vegetation in reducing pollution and associated ecological and human health risks. To conclude, using a systems approach has significance in assessing pollution at the ecosystem level, and focusing on riverbank land use remains significant in developing methods to reduce pollution and ecological and human health risks for sustainable riverbank management.

Assessment of toxic metal contamination, distribution and risk in the sediments from lagoons used for fish farming in the central region of Peru

Toxic metal contamination, distribution and risk were evaluated in the sediments of three lagoons used for fish farming in the central region of Peru. The distribution of toxic metals in the sediment was in the following descending order of Zn > V > Ni > Cu > Pb > As > Cr > Co > Cd > Sb. Contamination factor (Cf) and geoaccumulation index (I_geo) values for Co, Cr, Cu, Ni, Pb, Sb, V and Zn indicated low contamination and for Cd moderate contamination. The pollution load index (PLI) ranged from 0.3856 to 0.5622; indicating no appreciable contamination and the modified degree of contamination (mCd) corroborated this result. The potential ecological risk (R_i) in the Tranca Grande and Pomacocha lagoons revealed a low potential ecological risk and in Tipicocha a moderate potential ecological risk. HI values < 1 indicated that non-carcinogenic adverse effects were negligible. In adults, the Total carcinogenic risk (TCR) values for As, Cd, Cr, Ni and Pb were less than 1.00E-04, indicating no significant carcinogenic risk. In children, TCR values showed similar behavior with the exception of As. Therefore, considering that fish production for domestic consumption and export is carried out in these lagoons, it is important to continue monitoring toxic metals to protect the health of these ecosystems and human health.

Anthropogenic Intensity-Determined Assembly and Network Stability of Bacterioplankton Communities in the Le'an River

Bacterioplankton are essential components of riverine ecosystems. However, the mechanisms (deterministic or stochastic processes) and co-occurrence networks by which these communities respond to anthropogenic disturbances are not well understood. Here, we integrated niche-neutrality dynamic balancing and co-occurrence network analysis to investigate the dispersal dynamics of bacterioplankton communities along human activity intensity gradients. Results showed that the lower reaches (where intensity of human activity is high) had an increased composition of bacterioplankton communities which induced strong increases in bacterioplankton diversity. Human activity intensity changes influenced bacterioplankton community assembly via regulation of the deterministic-stochastic balance, with deterministic processes more important as human activity increases. Bacterioplankton molecular ecological network stability and robustness were higher on average in the upper reaches (where there is lower intensity of human activity), but a human activity intensity increase of about 10%/10% can reduce co-occurrence network stability of bacterioplankton communities by an average of 0.62%/0.42% in the dry and wet season, respectively. In addition, water chemistry (especially NO₃^–-N and Cl^–) contributed more to explaining community assembly (especially the composition) than geographic distance and land use in the dry season, while the bacterioplankton community (especially the bacterioplankton network) was more influenced by distance (especially the length of rivers and dendritic streams) and land use (especially forest regions) in the wet season. Our research provides a new perspective of community assembly in rivers and important insights into future research on environmental monitoring and classified management of aquatic ecosystems under the influence of human activity.

Trace Elements in Sediments of Rivers Affected by Brown Coal Mining: A Potential Environmental Hazard

Brown coal remains an important energy source in Europe, including countries such as Germany, Poland, the Czech Republic, and Greece. Open-pit mines disturb the environment in terms of air quality, hydrology, and chemical and biological transformations in rivers receiving mine waters. In the present study, we assessed the impact of mine waters from four brown coal open-pit mines on the contamination of river sediments. Chemical analysis included the quantification of 62 elements, including heavy metals (HMs) and rare earth elements (REEs). The contamination of sediments by HMs was evaluated using the contamination factor (CF), the pollution load index (PLI), and the Nemerow multi-factor index (PI). The potential toxic effects of HMs on aquatic organisms were assessed using the potential ecological risk index (PERI). Detailed analysis of chondrite-standardized concentrations of REEs was performed to describe the effects of mine water on their pattern in sediments. Cluster analysis (CA) and principal component analysis (PCA) were employed to divide study sites into groups and to evaluate the combined effect of sediment texture and site location on HMs and REEs in sediments. The study showed that after mine water discharge, there is a decrease in HM and REE concentrations in sediments. The decrease in each element’s concentration in sites located 100 m downstream of the discharge was caused by washing out of the finest fractions of sediments by mine waters.

Applying synchronous fluorescence spectroscopy conjunct second derivative and two-dimensional correlation to analyze the interactions of copper (II) with dissolved organic matter from an urbanized river

Heavy metal speciation and distribution is significantly influenced by dissolved organic matter (DOM) exhibited in ecosystems, particularly in urbanized rivers. Synchronous fluorescence spectroscopy (SFS) conjunct second derivative and two-dimensional correlation spectroscopy (2D-COS) was devoted to characterizing interactions of DOM-copper (II). Three typical water samples were collected from Baitapu River. Only protein-like fluorescence (PLF) and fulvic-like (FLF) were identified from the SFS. Stability constant (log K) values of PLF complexes with copper (II) varied from 4.277 to 5.833, and proportion of binding fluorescent materials (f) were 0.054-2.640. The log K values of FLF complexes with copper (II) varied from 3.996 to 4.243, while the f values were 0.001-0.036. Obviously, PLF had much stronger complexing capacity than FLF. There were four obvious peaks in the principal component analysis and second derivative fluorescence spectroscopy (SDFS), i.e., tyrosine-like (TYLF), tryptophan-like (TRLF), microbial humus-like (MHLF) and FLF. The log K values of TYLF and TRLF complexes were 4.899-5.907 and 4.598-5.831, respectively, which were similar to those from PLF. The log K values of MHLF complexes varied from 4.311 to 5.760, and the f values were 0.261-8.688. The log K values of FLF complexes were ranged from 4.598 to 5.831, which were higher than those deduced from the SFS. Interestingly, by the SDSF, PLF was divided into TYLF and TRLF, which increased the parameters values from DOM-copper (II) complexes. 2D-SFS-COS revealed that the TRLF was more susceptive response to copper (II) appended than TYLF, MHLF, and FLF. Moreover, TYLF and TRLF could priorly interact with copper (II). The SDSF conjunct 2D-COS could be effective approaches for insight into the complexing heterogeneity of DOM with copper (II). The study could present a support to preventing heavy metals and organic pollution in urbanized rivers.

Ecological Risk Due to Heavy Metal Contamination in Sediment and Water of Natural Wetlands with Tourist Influence in the Central Region of Peru

In this study, the quality of sediment and surface water in two natural wetlands, Paca and Tragadero, in the central region of Peru was evaluated using pollution indices, including the geoaccumulation index, pollutant load index, modified pollution degree, potential ecological risk index, and site rank index, for four heavy metals. Principal component analysis was used to identify potential metal contaminant sources. The determination of Fe, Zn, Pb, and As was performed by flame atomic absorption spectrophotometry. The average concentrations of metals in the sediments of both lagoons decreased in the order Fe > Zn > Pb > As. The analysis of the contamination indices determined that As and Pb are the elements that contribute the most to environmental degradation in both wetlands. There is a strong correlation between the values of potential ecological risk and the modified degree of contamination, revealing that the Paca wetland has a moderate degree of contamination and potential ecological risk, while Tragadero presents a high degree of contamination and considerable potential ecological risk. The application of the site rank index showed that more than 50% of the sampling sites have between high and severe contamination. The principal component analysis presented 79.2% of the total variance. Finally, the results of this study are essential in order to carry out preventive actions for environmental protection in these lake ecosystems of great importance for many activities, such as bird watching.

Exploration of the variations and relationships between trace metal enrichment in dust and ecological risks associated with rapid urban expansion

Trace metals in street dust originate from many natural and anthropogenic sources and may directly or indirectly affect daily life and health. Here, the enrichment factor (EF), an efficient parameter to assess the contamination by trace metals, was evaluated and compared in four different zones of the urban area of Nanchang city during different seasons. Results showed that EFs of trace metals have regional seasonal variations. The EF range of Cr, Ni, Cu, Zn, As, Cd and Pb were found to be (0.76-16.38), (0.66-9.06), (1.09-169.58), (1.52-36.16), (0.44-7.17), (2.07-78.38), (0.95-20.94), respectively. These values indicate minimal to significant pollution. The EF values of Zn, Cd and Pb in street dust show very similar variations as their median and mean values of EF are higher in certain zones, and their seasonal variations are similar. The Ni and As results suggest that anthropogenic influences for these elements are not significant. The Ni may be influenced by land use type rather than point sources and As may be attributed to natural sources. The Principal Component Absolute Scores - Multivariate Linear Regression (PCAS-MLR) model was used to identify the types and contributions of trace metal sources. The main sources of trace metals in dust were found to be industrial discharges and traffic emissions. However, the percentages of their contributions have significant regional differences. The relationship between the EF of trace metals and the ecological risk index (ERI) was also investigated, and indicates that seriously polluted areas correspond to high ERI regions. The land use types and characteristics of the source jointly affects the relationship between EFs and ERI.

The Levels, Sources, and Spatial Distribution of Heavy Metals in Soils from the Drinking Water Sources of Beijing, China

Our study area is the upstream watershed of the Guanting and Miyun Reservoirs; together, these two reservoirs comprise the main drinking water source of Beijing, China. In order to prevent crop contamination and preserve the quality of the water and soil, it is important to investigate the spatial distribution and the sources of the heavy metals in farmland soils on the watershed scale. For this study, we collected 23,851 farmland surface soil samples. Based on our analysis of the concentrations of eight heavy metals in these samples, we found that the overall soil quality in our study area is excellent, but that the Cd, Cu, Zn, and Cr contamination risks are relatively high. Moreover, a percentage of samples exceeded the Cd (1.54%,), Cu (0.28%), Zn (0.25%), Cr (0.13%), Pb (0.09%), As (0.05%), Ni (0.04%), and Hg (0.02%) risk screening values for soil contamination in agricultural land. In addition to determining the spatial distribution characteristics of the heavy metal concentrations of the soil samples, we also conducted a factor analysis and an R cluster analysis (CA) whcih can gathered the similar variables to track the sources of the heavy metals. We found that the Cd, Pb, and Zn are likely sourced from a quartz syenite porphyry body and from coal-fired enterprises, while the Cr, Cu, and Ni contaminations are mainly caused by runoff from iron ore smelting. Additionally, agricultural production contributes to the local accumulation of Cu, and industrial (smelting) discharge is partially responsible for the As contamination. As a result of the atmospheric deposition of pollutants, areas with high Hg concentrations are generally centered on large- and medium-sized cities. Due to these high natural heavy metal background values, the existing and future heavy metal contamination in the watershed poses a serious ecological risk to both the soil and the surface water.

Large-scale evaluation of deposition, bioavailability and ecological risks of the potentially toxic metals in the sediment cores of the hotspot coral reef ecosystems (Persian Gulf, Iran)

Coral reefs of the Persian Gulf are vulnerable to the potentially toxic metals (PTMs) accumulated in the ambient sediments. Nonetheless, few studies have investigated the PTMs pollution and risk in the hotspot coral ecosystems of the Persian Gulf at a large-scale. Hereupon, this study focused on the PTMs contamination, their potential ecological risks, historical depositions, geochemical controls and the plausible pollution sources in the core sediments (0-40 cm) collected from the ten coral ecosystems of the Persian Gulf, Iran. Both total and fraction analysis indicated considerable metal pollution levels. Contamination was steadily decreasing towards the bottom of the sediment core, revealing the impact of a recent anthropogenic input. High metal association with the exchangeable and other mobile fractions was observed, indicating their high bioavailability. Of all the elements analyzed, toxic metals Cd, Hg and As exhibited the highest potential ecological risk (RI). Site rank index (SRI), modified degree of contamination (_mCd), and contamination severity index (CSI) based approaches identified stations ST5, ST9 and ST10 as the most contaminated sites of the study area. The same stations were also found to possess considerable ecological risk. Principal component analysis (PCA) revealed that the stations located in the zone of the highest anthropogenic impact contain pollution sources for all the metals analyzed, whereas areas with low anthropogenic activity are mainly affected by the river runoff and urban emissions.