Past 140-year environmental record in the northern South China Sea: Evidence from coral skeletal trace metal variations

About 140-year changes in the trace metals in Porites coral samples from two locations in the northern South China Sea were investigated. Results of PCA analyses suggest that near the coast, terrestrial input impacted behavior of trace metals by 28.4%, impact of Sea Surface Temperature (SST) was 19.0%, contribution of war and infrastructure were 14.4% and 15.6% respectively. But for a location in the open sea, contribution of War and SST reached 33.2% and 16.5%, while activities of infrastructure and guano exploration reached 13.2% and 14.7%. While the spatiotemporal change model of Cu, Cd and Pb in seawater of the north area of South China Sea during 1986-1997 were reconstructed. It was found that in the sea area Cu and Cd contaminations were distributed near the coast while areas around Sanya, Hainan had high Pb levels because of the well-developed tourism related activities. (C) 2013 Elsevier Ltd. All rights reserved

The estimation of heavy metals in rivers sediments in Changjiang River Delta by visible/near infrared (Vis/NIR) spectroscopy

Diffuse reflectance visible and near infrared spectroscopy (Vis/NIR) was applied to screen the heavy metals (As, Cd, Cr, Cu, Hg, Pb and Zn) in suspended solids collected from the Changjiang River Delta. Principal component analysis (PCA) was used to characterized the spectra data of samples. The reflectance of the spectra and variation trends of spectra reflectance were distinguished by the first two principal components. The samples in Jiangsu Province had lower reflectance than those in Zhejiang, with smooth increase of reflectance in 400-800 nm spectra region. Using selected spectra region (410-2408 nm), the Partial-least square (PLS) regression models were applied to screen As, Cd, Cr, Cu, Hg and Pb in sediment, while Hierarchical principal components analysis (HPCA) regression was used only for Zn. The optimal factor and spectra region were obtained for selected models by comparing different pre-processing procedures. Results showed that potential change of hydraulic condition could degrade prediction ability of spectroscopy for heavy metals. Although the correlation coefficients and residual predictive deviation (RPD) displayed relative poor prediction results, the PLS and HPCA models of spectroscopy are useful non-destructive tools to screen heavy metals in sediment in Changjiang River Delta

Testing coral paleothermometers (B/Ca, Mg/Ca, Sr/Ca, U/Ca and δ18O) under impacts of large riverine runoff

Sea surface temperature (SST) proxies including B/Ca, Mg/Ca, Sr/Ca, U/Ca and delta O-18 were analyzed in the skeleton of a Porites coral collected from the Zhujiang River (Pearl River) Estuary (ZRE). These geochemical proxies are influenced by river runoff and this area of the northern South China Sea is strongly affected by seasonal freshwater floods. We assessed the robustness of each SST proxy through comparison with the local instrumental SST. Coral Sr/Ca shows the highest correlation with SST variations (r (2)=0.59), suggesting Sr/Ca is the most robust SST proxy. In contrast, coral delta O-18 (r (2)=0.46), B/Ca (r (2)=0.43) and U/Ca (r (2)=0.41) ratios were only moderately correlated with SST variations, suggesting that they are disturbed by some other factors in addition to SST. The poor correlation (r (2)=0.27) between SST and Mg/Ca indicates that Mg/Ca in coral skeletons is not a simple function of SST variations. This may ultimately limit the use of Mg/Ca as a coral paleothermometer

Influencing Factors of Elevated Levels of Potentially Toxic Elements in Agricultural Soils from Typical Karst Regions of China

Agricultural soils originating from carbonate rocks within karst regions exhibit inherent high concentrations of potentially toxic elements (PTEs) due to geogenic processes. However, the influencing factors of the elevated levels of PTEs in the naturally contaminated karst regions remain inadequately comprehended. This research investigates the chemical compositions of 278 soils derived from carbonate rocks. Descriptive statistics, stepwise multiple regression, and the random forest (RF) method were applied to screen the significant factors that affect the distribution, migration, and enrichment of the PTEs in soils. Cadmium (Cd) and arsenic (As) are the most highly contaminated PTEs in the soils of the study area, and the average contents of Cd and As in soils are 11.5 and 2.92 times the national soil background value, respectively. The pollution risk ranking of PTEs is Cd > As > Cr > Zn > Pb > Cu > Ni > Hg, using the proportion exceeding the risk screening thresholds of agricultural land as the standard. Soil Fe2O3 and Mn contents, soil pH and total organic carbon (TOC) values, and weathering intensity (characterized using the chemical index of alternation, CIA) are the most important factors influencing the PTE levels in agricultural soils

Cadmium transfer from contaminated soils to the human body through rice consumption in southern Jiangsu Province, China

Bioaccessible cadmium concentration in rice grains can be predicted by phytoavailable Cd concentration in soil.</p