Spatial distribution and temporal variation of metals in the vicinity of a municipal solid waste incinerator after a modernization of the flue gas cleaning systems of the facility

Effects of long-term zinc smelting activities on the distribution and health risk of heavy metals in agricultural soils of Guizhou province, China

To assess the effect of zinc smelting on environment and human health, the concentration, distribution, sources and health risk of eight heavy metals (Pb, Cd, Cu, Zn, Cr, Ni, Mn, and As) were investigated from agricultural soils in a long-term Zn smelting area in Guizhou, China. Different health risk assessment methods and models were used to access health risks. The results show that the concentrations of all the eight heavy metals were significantly higher than their corresponding background values (p < 0.05). Pb, Cd, and As were the most contaminated elements, with 93.6%, 90.3% and 48.4% of agricultural soil samples higher than the risk screening values, respectively. Statistical analysis indicated that Pb, Cd, Cu, Zn, Mn, and As could be mainly accounted for Zn smelting activities, while Cr and Ni may be generally more controlled by natural sources. The geo-accumulation index (Igeo) suggested that the most seriously contaminating heavy metals were Pb, Cd, and Zn, with 96.8%, 90.3%, and 96.8%, respectively, of the soil samples classified as moderately to extremely contaminated. The non-carcinogenic health risk associated with Pb, Cd and As were observed for children, meanwhile, the carcinogenic risk due to As was found for both adults and children. Regardless of cancer risk or non-cancer risk, local children are at greater risk than adults. Therefore, Pb, Cd and As play the leading role to cause potential health risks in the study area, which need to be paid more attention and also effective control measures should be taken.

Co-Selection of Bacterial Metal and Antibiotic Resistance in Soil Laboratory Microcosms

Accumulation of heavy metals (HMs) in agricultural soil following the application of superphosphate fertilisers seems to induce resistance of soil bacteria to HMs and appears to co-select for resistance to antibiotics (Ab). This study aimed to investigate the selection of co-resistance of soil bacteria to HMs and Ab in uncontaminated soil incubated for 6 weeks at 25 °C in laboratory microcosms spiked with ranges of concentrations of cadmium (Cd), zinc (Zn) and mercury (Hg). Co-selection of HM and Ab resistance was assessed using plate culture on media with a range of HM and Ab concentrations, and pollution-induced community tolerance (PICT) assays. Bacterial diversity was profiled via terminal restriction fragment length polymorphism (TRFLP) assay and 16S rDNA sequencing of genomic DNA isolated from selected microcosms. Based on sequence data, the microbial communities exposed to HMs were found to differ significantly compared to control microcosms with no added HM across a range of taxonomic levels.

Environmental Mn(II) enhances the activity of dissimilatory arsenate-respiring prokaryotes from arsenic-contaminated soils

Many investigations suggest that dissimilatory arsenate-respiring prokaryotes (DARPs) play a key role in stimulating reductive mobilization of As from solid phase into groundwater, but it is not clear how environmental Mn(II) affects the DARPs-mediated reductive mobilization of arsenic. To resolve this issue, we collected soil samples from a realgar tailings-affected area. We found that there were diverse arsenate-respiratory reductase (arr) genes in the soils. The microbial communities had high arsenate-respiring activity, and were able to efficiently stimulate the reductive mobilization of As. Compared to the microcosms without Mn(II), addition of 10 mmol/L Mn(II) to the microcosms led to 23.99%-251.79% increases in the microbial mobilization of As, and led to 133.3%-239.2% increases in the abundances of arr genes. We further isolated a new cultivable DARP, Bacillus sp. F11, from the arsenic-contaminated soils. It completely reduced 1 mmol/L As(V) in 5 days under the optimal reaction conditions. We further found that it was able to efficiently catalyze the reductive mobilization and release of As from the solid phase; the addition of 2 mmol/L Mn(II) led to 98.49%-248.78% increases in the F11 cells-mediated reductive mobilization of As, and 70.6%-104.4% increases in the arr gene abundances. These data suggest that environmental Mn(II) markedly increased the DARPs-mediated reductive mobilization of As in arsenic-contaminated soils. This work provided a new insight into the close association between the biogeochemical cycles of arsenic and manganese.

Heavy metal pollution and health risk assessment of agricultural soil near a smelter in an industrial city in China

To assess heavy metal pollution and human health risk, a total of 28 topsoil samples were collected during four seasons from seven agricultural soil sites near a famous smelter in Jiyuan, China. The maximum concentrations of Cd, Pb, Hg, As, Zn, Cu, Ni, and Cr were 26.00, 2601.00, 3.29, 65.00, 410.00, 156.30, 54.80, and 73.60 mg kg^-1, respectively. Compared with the sampling site nearest to the smelter, the concentrations of six metals at the farthest site were decreased significantly (P < 0.05). All sites were heavily contaminated, with Nemerow index (P) >3.0, and all sites had very high ecological risks related to Cd and Hg. The non-carcinogenic risk for children (based on combined exposure to the eight metals) was above the safety level. The carcinogenic risk of As for adults (8.98 × 10^-6) and children (1.49 × 10^-5) exceeded the acceptable level (1 × 10^-6). Results suggest a serious health risk in the polluted areas, particularly for children.Abbreviation Cd: Cadmium; Pb: Lead; Hg: Mercury; As: Arsenic; Zn: Zinc; Cu: Copper; Ni: Nickel; Cr: Chromium; P: Nemerow index; RI: Potential ecological risk index; E_i: Monomial potential ecological risk of a specific heavy metal; HI: non-carcinogenic hazard index; CR: Carcinogenic risk; TN: Total nitrogen; TP: Total phosphorus; OM: Organic matter; MC: Moisture content; ADD: Average daily dose.

Impact of municipal solid waste incineration on heavy metals in the surrounding soils by multivariate analysis and lead isotope analysis

Municipal solid waste (MSW) incineration has become an important anthropogenic source of heavy metals (HMs) to the environment. However, assessing the impact of MSW incineration on HMs in the environment, especially soils, can be a challenging task because of various HM sources. To investigate the effect of MSW incineration on HMs in soils, soil samples collected at different distances from four MSW incinerators in Shanghai, China were analyzed for their contents of eight HMs (antimony, cadmium, chromium, copper, lead, mercury, nickel, and zinc) and lead (Pb) isotope ratios. Source identification and apportionment of HMs were accomplished using principal component analysis and Pb isotope analysis. Results indicated that the relatively high contents of cadmium, lead, antimony, and zinc in the soils at 250 m and 750-1250 m away from the MSW incinerators were related to MSW incineration, while the elevated contents of the other four HMs were associated with other anthropogenic activities. Based on Pb isotope analysis, the contribution ratio of MSW incineration (which had been operated for more than 14 years) to the accumulation of Pb in soil was approximately 10% on average, which was lower than coal combustion only. Incinerator emissions of Pb could have a measurable effect on the soil contamination within a limited area (≤1500 m).

Estimation of optimal biomass fraction measuring cycle formunicipal solid waste incineration facilities in Korea

This study estimates the optimum sampling cycle using a statistical method for biomass fraction. More than ten samples were collected from each of the three municipal solid waste (MSW) facilities between June 2013 and March 2015 and the biomass fraction was analyzed. The analysis data were grouped into monthly, quarterly, semi-annual, and annual intervals and the optimum sampling cycle for the detection of the biomass fraction was estimated. Biomass fraction data did not show a normal distribution. Therefore, the non-parametric Kruskal-Wallis test was applied to compare the average values for each sample group. The Kruskal-Wallis test results showed that the average monthly, quarterly, semi-annual, and annual values for all three MSW incineration facilities were equal. Therefore, the biomass fraction at the MSW incineration facilities should be calculated on a yearly cycle which is the longest period of the temporal cycles tested.

Two Decades of Environmental Surveillance in the Vicinity of a Waste Incinerator: Human Health Risks Associated with Metals and PCDD/Fs

The concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), as well as the levels of a number of heavy metals, have been periodically measured in samples of soil and vegetation collected around a municipal solid waste incinerator (MSWI) in Tarragona (Catalonia, Spain) for approximately 20 years. Since 2007, the levels of the above-mentioned pollutants have also been determined in air samples by means of either active or passive samplers. In the present study, data regarding the environmental impact of the MSWI, in terms of PCDD/Fs and heavy metals, are updated. The temporal trends of these pollutants were evaluated by comparison with data from previous surveys. In the current survey (2013-2014), mean concentrations of PCDD/Fs in soil, vegetation, and air were 0.63 ng I-TEQ/g, 0.07 ng I-TEQ/g, and 10.1 fg WHO-TEQ/m(3), respectively. Decreases of 47 and 35 % of PCDD/Fs in soil and vegetation, respectively, were observed in relation to the background study (1999). Regarding air samples, a slight temporal decrease of the PCDD/F levels was also found with the remaining concentrations staying nearly constant through time. With respect to metals, notable fluctuations in the concentrations were noted, being dependent on each specific environmental monitor. Overall, the current exposure to PCDD/Fs and metals does not mean any additional health risks for the population living near the facility. In conclusion, the results of the present study show that the environmental impact of the Tarragona MSWI is not significant, in terms of PCDD/Fs and heavy metals, after >20 years of continuous operation.

Past and future cadmium emissions from municipal solid-waste incinerators in Japan for the assessment of cadmium control policy

Cadmium (Cd) is a harmful pollutant emitted from municipal solid-waste incinerators (MSWIs). Cd stack emissions from MSWIs have been estimated between 1970 and 2030 in Japan. The aims of this study are to quantify emitted Cd by category and to analyze Cd control policies to reduce emissions. Emissions were estimated using a dynamic substance flow analysis (SFA) that took into account representative waste treatment flows and historical changes in emission factors. This work revealed that the emissions peaked in 1973 (11.1t) and were ten times those in 2010 (1.2 t). Emission from MSWIs was two-thirds of that from non-ferrous smelting in 2010. The main Cd emission source was pigment use in the 1970s, but after 2000 it had shifted to nickel-cadmium (Ni-Cd) batteries. Future emissions were estimated for 2030. Compared to the business-as-usual scenario, an intensive collection of used Ni-Cd batteries and a ban on any future use of Ni-Cd batteries will reduce emissions by 0.09 and 0.3 1t, respectively, in 2030. This approach enables us to identify the major Cd emission source from MSWIs, and to prioritize the possible Cd control policies.

Contribution of a municipal solid waste incinerator to the trace metals in the surrounding soil

This study analyses the pedological environment of the area near a municipal waste incinerator that has been operating in the south-east district of Pisa for approximately 20 years. There are many other industrial activities in the area besides the incinerator, which represent possible sources of pollution, as well as heavy road traffic. The study area was defined by a 0-4-km zone around the site with a population of approximately 12,000 residents. The study included the physical and chemical characterisation of 100 samples of soil and an analysis of trace metals such as Cr, Ni, Pb, Zn, Hg, As and Cd. The samples were grouped into soil use categories. The results showed Zn, Pb and Hg correlated with their potentially mobile fractions, and suggested an anthropic contribution to their presence in the soil. Ni, Cr and As showed values attributable to a lithological origin. This was consistent with the PCA results. The aim was to define the environmental state of the soil of the area in order to create a reference for future research and to verify the possible presence of pollution from other sources (local industrial activities and traffic).

Toxic emissions from crematories: a review

In recent years, the cremation ratio of cadavers has increased dramatically in many countries. Crematories have been identified as sources of various environmental pollutants, being polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and mercury those raising most concern. In contrast to other incineration processes for which the number of studies on their toxic emissions is considerable, references related to PCDD/F and mercury emissions from crematories and their health risks are very limited. In this paper, the scientific information concerning these issues, using the databases PubMed, Scopus and Scirus, is reviewed. Results show that in comparison with PCDD/F emissions from other sources, those corresponding to crematories are significantly lower, while those of mercury should not be underrated.

Metal levels in sugar cane (Saccharum spp.) samples from an area under the influence of a municipal landfill and a medical waste treatment system in Brazil

In July 2003, duplicated samples of roots, stems and leaves of sugar cane (Saccharum spp.) were collected in 25 points of an area under direct influence of the municipal landfill site (MLS) and medical waste treatment system (MWTS) of Ribeirao Preto, São Paulo, Brazil. Cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), lead (Pb) and zinc (Zn) were determined by atomic absorption spectrophotometry. The following concentrations (mg/kg) were found in roots: Cd, 0.22+/-0.12; Cr, 64.3+/-48.7; Cu, 140.6+/-27.7; Hg, 0.04+/-0.02; Mn, 561.6+/-283.3; Pb, 7.9+/-2.1 and Zn, 177.4+/-64.9. For some metals, these levels are higher than the concentrations previously reported for different plants, reaching, in some cases, values that might be considered toxic for vegetables. Metal levels in stems were 80-90% of those found in roots, while the concentrations detected in leaves were significantly lower than those in roots. The present results suggest that MLS and MWTS activities might have been increasing metal concentrations in edible tissues of sugar cane grown in the area under their influence. Moreover, the traditional agricultural practices in the production of sugar cane could be also another determinant factor to reach the current metal levels. The results of this study indicate that sugar cane is a crop that is able to grow in areas where metals in soils are accumulated.

Trends in the levels of metals in soils and vegetation samples collected near a hazardous waste incinerator

In 1998 and 2001, the levels of a number of elements (As, Be, Cd, Cr, Hg, Mn, Ni, Pb, Sn, Tl, and V) were determined in 40 soil and 40 herbage samples collected near a new hazardous waste incinerator (HWI) (Constantí, Catalonia, Spain). In 2003, soil and herbage samples were again collected at the same sampling points in which samples had been taken in the previous surveys. During the period 1998-2003, As, Be, Cr, Ni, and V levels showed significant increases in soils. In contrast, the levels of Cd, Hg, and Sn significantly decreased. With respect to herbage, while Cr, Mn, and V concentrations significantly increased, those of As levels diminished. On the other hand, human health risks derived from metal ingestion and inhalation of soils were also assessed. In relation to noncarcinogenic risks, all elements presented a value inside the safe interval. In turn, Cd and Cr were also in the safe interval of carcinogenic risks, whereas in contrast As levels clearly exceeded the regulatory limits concerning carcinogenic risks. According to the results of the previous (2001) and current (2003) surveys, the fluctuations in the metal concentrations suggest that the influence of the HWI is minimal in relation to other metal pollution sources in the area.

Levels of metals in soils of Alcalá de Henares, Spain: human health risks

The concentrations of aluminium (Al), arsenic (As), beryllium (Be), cadmium (Cd), chromium (Cr), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), tin (Sn), thallium (Tl), vanadium (V), and zinc (Zn) were determined in soil samples collected in Alcalá de Henares (Madrid, Spain). Human health risks derived from metal inhalation and ingestion of soils were also assessed. For noncarcinogenic risks, the current levels of metals were usually lower than those considered as safe for the general population. With respect to the potentially carcinogenic elements As, Be, Cd, and Cr, the concentrations of Be, Cd, and Cr were lower than the reference values, while the average As concentration (3.4 microg/g) was higher than the safety limit for risk cancer. In general terms, the potential human health impact of ingestion/inhalation through soils of the analyzed elements seems to be rather small.