Assessment of heavy metal contamination in surface sediments from the nearshore zone, southern Jiangsu Province, China

Temporal variation and pollution status of heavy metals in core sediments from Jiangsu intertidal area, China

Eight heavy metal concentrations were analyzed from a 60.35-m-long sediment core in the Jiangsu intertidal area, China. Based on the lithofacies characteristics, mean grain size, downcore distributions of elements, and accelerator mass spectrometry (AMS) 14C and optically stimulated luminescence (OSL) data, the sediments in the core were divided into three units that formed during marine isotope stages 4 (MIS 4), MIS 3, and MIS 1. Except for Cd, all the other heavy metals had the lowest average concentrations in U3, which formed during MIS 4 with the coarsest sediment, representing a fluvial deposit. Most of the heavy metals were positively correlated with Al, Fe, and the total organic carbon (TOC), indicating these metals had the same sources. Pearson's correlation coefficient, enrichment factor, geoaccumulation index, and principal component analysis suggested that there was no element enrichment or contamination in the core sediments and that all heavy metals were naturally sourced.

Heavy metal concentration profiles and pollution assessment in the Jiangsu offshore area, China

The concentration profiles of various major and trace heavy metals (Cu, Pb, Zn, Cr, Cd, As, Hg, Ni, Li, and Co) were investigated along a 40.1-m-long sediment core in the offshore Jiangsu area of China, to assess their depositional trends and contamination levels. All metals, except Cd, exhibited similar profiles with high average concentrations during the Marine Isotope Stage 2-4 period. The sediment trace-metal concentrations were primarily related to grain size and sediment sources, with almost all heavy metals (except Cd) being positively correlated. Enrichment factors, geoaccumulation indices, and principal component analysis indicated no elemental enrichment or contamination. The high EF and I_geo values of As, Hg, and Li may be related to their background values.

Distribution, contamination and provenance of heavy metals in sediments from the nearshore area of Weihai City, eastern Shandong Peninsula, China

We analyzed eight heavy metals (Cu, Pb, Zn, Cr, Cd, Hg, As, and Ni) in 85 seabed sediments off the coast of Weihai City, eastern Shandong Peninsula, China, to reveal their distributions, enrichment status, and pollutant sources. Cu, Pb, Zn, Cr, As, and Ni were enriched in all bays in both the inner and outer waters. However, Cd and Hg were more abundant in Weihai Bay, followed by Rongcheng Bay and Chaoyang Port, with denser populations and more developed industries near the coast. Most areas exhibited slight contamination with As and Pb, with relatively severe contamination in localized areas. Moreover, Weihai Bay showed slight contamination with Cd, Zn, and Hg. Heavy metals are largely influenced by the discharge of anthropogenic pollutants along the coast. It is recommended to implement strict control measures on the discharge of waste into the sea, and ensure the sustainable development of the marine ecological environment.

Trace metals in urbanized coasts: The central Atlantic of Morocco as a case study

This study describes the contamination, accumulation, and ecological risk assessment of five trace metals (Cd, Pb, Cu, Zn, and Cr) in sediments of an urbanized beach in the central Atlantic coastline of Morocco. The two-year investigation (2018 and 2019) included six sampling sites along a 6 km coastal reach. In both years, none of the studied trace metals exceeded the background or the sediment quality guidelines (SQGs). The eco-toxicological indices revealed low degree of contamination, unpolluted ecosystem, and low ecological risk of metals. However, Cd exceeded the background value and some SQGs following the increase of anthropogenic activities in 2019. Likewise, it indicated unpolluted to moderately polluted sediment as well as moderate ecological risk. Overall, it is highly recommended to mitigate the avoidable anthropogenic activities (marine litter generation, sewage discharge, intense urbanization, and vehicle traffic on the beach) that lead to the elevation of metal pollution in the study area.

Records of trace metals since the Holocene in sediments of Laizhou Bay, Bohai Sea, China

Trace metal (Cu, Pb, Zn, Cr, Cd, As, Hg, Ni, Li, and Co) concentration profiles along a sediment core were investigated to obtain background values, assess depositional trends and contamination levels in the Laizhou Bay, China. The enrichment factors of the metals indicated no anthropogenic enrichment, except for Pb, Cd, and Hg, which have been influenced by human activities since 7 ka. The mean concentrations of trace metals in the 10-7 ka phase can be considered as the background values in the study area. Principal component analysis indicated that the metals were mainly naturally sourced throughout the observed depositional period. Their geoaccumulation indices indicated that the sediments were not contaminated by Cu, Zn, Cr, Ni, and Co, but were contaminated by Pb, Cd, and Hg during the 7-0 ka period.

Historical records of trace metals in sediments of the eastern Beibu Gulf, South China Sea

In this study, trace metal (Cu, Pb, Zn, Cr, Cd, As, Hg, Ni, Li, and Co) concentration profiles along a sediment core were investigated to obtain background values and assess depositional trends and contamination levels in the Beibu Gulf. The EFs of all metals indicated no enrichment. The mean concentrations of all trace metals in the 10-6.5 ka phase could be considered the background values in the study area. Factor and principal component analyses indicated that the metals were mainly naturally sourced throughout the observed depositional period. Their geoaccumulation indices revealed that the sediments were not contaminated by trace metals.

Assessment of Potential Ecological Risk of Heavy Metals in Surface Soils of Laizhou, Eastern China

With the rapid industrialization and urbanization, more attention is turning to heavy metal contamination in the soil environment. To assess the potential environmental risk on soil, a comprehensive geochemistry study on heavy metal was performed in Laizhou, eastern China, using 3834 surface soil samples (0–20 cm, regular grid of 1 × 1 km2) and 60 layered soil samples (0–200 cm) were analyzed. The average concentrations of As, Cd, Cr, Cu, Hg, Ni, Zn and Pb were 7.60 mg·kg−1, 0.15 mg·kg−1, 45.50 mg·kg−1, 19.10 mg·kg−1, 44.00μg·kg−1, 18.70 mg·kg−1, 51.40 mg·kg−1 and 29.00 mg·kg−1, which were lower than the threshold levels of the Grade II criteria of China national environment quality standard for soil, but the contents of As, Cd, Hg, and Pb were higher than background values of eastern Shandong Province surface soil. Fractionation analysis showed that the potential bioavailability in surface soils decreases in the order of Cd > As > Cu > Ni > Zn > Cr > Pb > Hg. Soil assessments with enrichment factor, contamination factor, Nemerow composite index, geo-accumulation index and potential ecological risk index, indicate the soil in Laizhou is contaminated strongly with As, Cd and Hg and a moderately Cr, Ni, Cu and Zn. The level of Pb pollution is between moderate to high. Multivariate analyses suggest that Cr and Ni were derived mainly from natural sources, and As, Cd, Pb, while Hg mostly came from anthropogenic sources. Cu and Zn were from a mixture of anthropogenic and natural sources. Our results demonstrate that more attention should be paid to monitoring soil quality in the heavily polluted site.

Occurrence of Virulence Factors and Antibiotic and Heavy Metal Resistance in Vibrio parahaemolyticus Isolated from Pacific Mackerel at Markets in Zhejiang, China

ABSTRACT

Vibrio parahaemolyticus is a widespread bacterium in the marine environment and is one of the leading causes of food-derived bacterial poisoning in humans worldwide. The main objective of this study was to determine the prevalence, virulence factors, and antibiotic and heavy metal resistance profiles of V. parahaemolyticus in Pacific mackerel (Pneumatophorus japonicus) from different markets in Zhejiang Province, People's Republic of China. In total, 112 (31.11%) V. parahaemolyticus isolates were identified from 360 Pacific mackerel samples, with an extremely low occurrence of the virulence genes trh (1.79%, 2 of 112) and tdh (0%, 0 of 112). Antibiotic resistance testing revealed that most isolates showed resistance to ampicillin (96.43%, 108 of 112) and streptomycin (90.18%, 101 of 112), whereas all strains were sensitive to kanamycin, florfenicol, cefamandole, and trimethoprim-sulfamethoxazole. Furthermore, 46.43% (52 of 112) of isolates, which had 12 different phenotypes, were classified as multidrug resistant. In addition, the multiple antibiotic resistance index values of isolates were between 0.05 and 0.63, and the maximum multiple antibiotic resistance index was attributed to two isolates that exhibited resistance to 12 antibiotics. Heavy metal resistance patterns were similar among the six different markets. The majority of isolates showed resistance to Cd2+ (78.57%) and Pb2+ (51.79%), and fewer were resistant to Cu2+ (37.50%), Zn2+ (25.00%), Co2+ (9.82%), Ni2+ (6.25%), and Mn2+ (4.46%). No isolates were resistant to Cr3+. In total, 22.32% (25 of 112) of strains were multiheavy metal resistant. Furthermore, multidrug resistance and multiheavy metal resistance were found to be positively correlated in the V. parahaemolyticus strains by using Pearson's correlation analysis (P = 0.008; R = 0.925). This information will contribute to the monitoring of variations in the antibiotic and heavy metal resistance profiles of V. parahaemolyticus strains from seafood and provide insight into the appropriate use of antibiotics and the safe consumption of seafood.

HIGHLIGHTS

Assessment of nutrient and heavy metal contamination in surface sediments of the Xiashan stream, eastern Guangdong Province, China

In this study, nutrient and heavy metal contamination in surface sediments of the Xiashan stream were investigated. Determining pollution degree of nutrient and heavy metal were the main objectives of this investigation. For this reason, the concentrations of total nitrogen (TN), total phosphorus (TP), seven heavy metals (Cu, Zn, Pb, Cd, Cr, Ni, Hg), and metalloid (As) were analyzed at 55 sampling sites. The mean TN concentration in surface sediments was 5.007 g/kg, while the mean TP concentration was 0.385 g/kg. Based on the sediment quality guideline (SQG_s) and background values of Chinese soil and sediment, the majority of the mean TN concentrations in surface sediments were higher than their background values, while the TP concentrations were different from those observed for TN. For heavy metal concentrations in surface sediments, most of sampling stations were higher than their background values. The mean geo-accumulation (I_geo) indices for heavy metals were ranked as follows: Cd > Hg > Cu > Zn > Pb > Ni > Cr > As. The potential ecological risk index (RI) indicated heavy metal contamination level in Xiashan stream was very high ecological risk. According to I_geo and RI values, heavy metals especially Cd and Hg are influenced significantly by anthropogenic activities. Cd and Hg are not only as pollutant but also considerable contributor to ecological risk. Multivariate statistical investigations showed that there is a significant and positive correlation between Pb, As, and Cd. Cu, Ni, and Cr have similar characteristic and therefore probably originated from the same sources. Suggested by the results, it is necessary to control nitrogen and heavy metal contamination caused by human activities in the study area.

Evaluation of heavy metal pollution in the Zayandeh-Rud River as the only permanent river in the central plateau of Iran

Zayandeh-Rud River is the only permanent river in the central plateau of Iran. This river has been subject to an extensive discharge of wastewater and effluents from several point and nonpoint pollution sources. Accordingly, sediment quality of Zayandeh-Rud River in Varzaneh region, were studied. Algae and the sediment were sampled through 3 replications at 6 stations in the downstream after crossing through the Isfahan city and reaching Gavkhuni international wetland. Chlorophyll content and As, Pb, and Cd concentrations were measured in each sample Cladophora sp. and Oscillatoria sp. were identified using standard identification keys. The mean concentrations of metals in all stations exceeded background levels. Mean concentration of arsenic (162.9 mg/kg) in the sediment is about 31 times more than the ISQG standard (5.9 mg/kg) and considerably higher than the similar studies in Iran and other regions of the world. The mean concentration of As in algae samples is higher than the most polluted areas of the world. The mean concentration of Pb in the sediment (19.69 mg/kg) is lower than the ISQGs standard (35 mg/kg) and most of the studied river in north of Iran such as Chalous, Baboul-Rud, Gorgan-Rud (North), Khiav (North West), and Anzali wetland. The mean concentration of Cd in the sediment (2.11 mg/kg) is significantly higher than ISQG standard (0.6 mg/kg and some north highly polluted wetlands of Iran such as Anzali. There is a significant positive correlation between the mean concentrations of As and Pb in the sediment and Cladophora sp. tissue, and a negative one between the mean concentration of Pb in the sediment and chlorophyll b/a. There are significant negative correlations between the mean concentration of As in the sediment and chlorophyll a, and the total chlorophyll concentration in Oscillatoria sp. The results of Muller index indicate that the concentrations of Pb, Cd, and As in all stations occur in the Unpolluted, Moderate/Heavy, and Heavy/Extreme groups, respectively. Degree of contamination and modified degree of contamination show very high degree of pollution in the studied area. RI in all the stations showed very high ecological risk. The bioaccumulation factor for all metals in both algae is less than one. So, these two species may not be described as heavy metal accumulators. This study is an alarm for the Zayandeh-Rud River as the most important freshwater source for the Iranian Plateau. Graphical abstract.

Ecological risk assessment of metals in sediments and selective plants of Uchalli Wetland Complex (UWC)-a Ramsar site

Wetlands act as kidneys of land and facilitate remediation of metals and other harmful pollutants through uptake by aquatic macrophytes. The aim of the present study was to investigate metal concentrations in sediments and plants, sources of metal origin, and contamination level in Uchalli Wetland Complex. Sediment samples were collected from 15 randomly selected sites. Metal concentrations (Cd, Pb, Ni, Cu, Zn, Cr, As, Mn) in sediments and macrophytes were determined during summer and winter seasons using the inductively coupled plasma technique. Metal concentrations in sediments during summer and winter seasons were in the order as follows: As > Mn > Zn > Cr > Ni > Cd > Pb > Cu and As > Mn > Zn > Cr > Ni > Pb > Cd >Cu respectively. All analyzed metals were within European Union (EU) limits. In macrophytes, these metals were in the order as follows: Mn > As > Ni > Zn > Cr > Cd > Cu > Pb and As > Mn > Zn > Ni > Cr > Cd > Pb during summer and winter seasons respectively. Contamination degree (C_d) (1.023-5.309) for these lakes showed low contamination during both seasons; mC_d values (below 1.5) showed very little contamination degree, while the pollution load index (0.012 to 0.0386) indicated no metal pollution in these lakes. PCA applied on sediment showed that Pb, Zn, Cr, Cu, and Cd had anthropogenic sources of origin. As and Mn were due to natural processes while Ni could be resultant of both anthropogenic and natural sources. PCA on macrophytes showed that Ni, Pb, Cr, Zn, Cu; Cd, As; Mn had anthropogenic, natural, and anthropogenic + natural sources of origin. The study concluded that metal concentrations in sediments were not up to dangerous level.