Characteristics of Marine Environmental Geochemistry From Ha Tinh to Quang Nam (60-100m Water Depth)

Abstract

The aim of this study is to elucidate the characteristics of marine environmental geochemistry from Ha TinhQuang Nam (60-100m water depth) based on analysis of geochemical parameters of seawater and surface sediments. Surface sediments that are high in absorbed capacity of toxic substances mainly accumulated in northern study area. Seawater dominantly characterized by weak alkaline-weak oxidation and contained biodegradable organic materials. Almost anion and chemical element concentrations in seawater tended to decrease with depth, with an exception for SO 4 2-, Br -, I -concentrations that had an opposite trend, increasing with depth and B, Hg concentrations displayed a complex variation. Sedimentary environments were highly predominant by weak alkaline-strong oxidizing features and carbonate-rich materials. Concentrations of anions and chemical elements tended to be higher in central area in comparison to northern and southern regions, and positively correlated with fine sediment compositions. Organochlorine pesticides (OCPs) concentration decreased with sediment depth, whilst polychlorinated biphenyls (PCBs) concentration had no clear trend. The organic material, heavy metal, OCPs and PCBs concentrations in seawater and sediments were all lower than environmental standards. The present results have provided important baseline data for monitoring marine environment quality and protecting the marine ecosystem of Ha Tinh -Quang Nam Sea.

Spatial distribution of trace elements in coastal sediments of Ha Tinh province, Vietnam

“…Cu concentration decreased from the coastal area to the nearshore area (Figure 3a) and with the depth of sediment cores (Table 2). The average Cu concentration in the coastal sediments of Ha Tinh province was 10.51 ± 6.30 mg/kg, similar to that in Ha Long bay (14.53 ± 6.30 mg/kg) [14], Tien Yen gulf [15], sedimentary basin of the Red river, Central Vietnamese shelf and slope and Nam Kon Son basin area [16]. Cu concentration was 3-5 times lower than in the coastal sediments of Thanh Hoa province [17] and Cam estuary [18] (Table 3).…”

“…Zn concentration markedly decreased with the depth of sediment layers and from the coastal to the nearshore area (Table 2, Figure 3c). The mean concentration of Zn was approximately that in Ha Long bay [14], Tien Yen gulf [15], the sedimentary basin of the Red river, the Central Vietnamese shelf and slope, and the Nam Kon Son basin area [16], but was 3-5 times lower than coastal sediments in Thanh Hoa province [17] and Cam estuary [18]. The similar concentration of Cu, Pb, and Zn in sediments from the present study with those in sediments from other coastal areas referred that the human activities in coastal areas did not highly impact the marine sediments in Ha Tinh province.…”

“…Pb concentration markedly decreased in the deeper sediment layers (Table 2). Compared with other coastal regions in Vietnam, Pb concentration had a similar range with Ha Long bay [14], Tien Yen gulf [15], the sedimentary basin of the Red river, the Central Vietnamese shelf and slope, and Nam Kon Son basin area [16], but was 6-9 times lower than in the coastal sediments in Thanh Hoa province [17] and Cam estuary [18] (Table 3). Zn concentration ranged from 7.1-86.1 mg/kg, averaging 40.99 ± 21.29 mg/kg (Table 1).…”

“…Mn concentration tended to decrease with the depth of sediment cores (Table 2). Mn concentration was two times higher than that in Tien Yen gulf [15] but lower than that in Ha Long bay [14], the sedimentary basin of the Red river, Central Vietnamese shelf and slope, and Nam Kon Son basin area [16], and the coastal area of Thanh Hoa province [17] and Cam estuary [18] (Table 3). Results showed that this study's higher Mn concentration in the coastal sediments could relate to steel production because manganese phosphate is commonly used to treat rust and prevent corrosion on steel.…”