Vietnam is a country with diverse and abundant mineral resources with nearly 5000 mines and ore spots of about 60 different minerals. Mining and processing of mineral resources have contributed about 9.6–10.6% of the country’s GDP since the year of 2000. However, the exploitation and processing of mineral resources have been leading to a certain soil and sediment contamination by heavy metals. Soil and sediment samples around lead-zince mines have been collected and analyzed for Cu, Zn, As, Cd, Hg, Pb and Ni in Cho Don district, Bac Kan province, Vietnam. Single pollution, geoaccumulation and enrichment indices have been used for assessing the sediment quality in terms of heavy metals by comparison with threshold and ecological risk limits. High concentration of Cu and Zn in the sediment is due to extremely high content of the two metals in the ore-surrounding soil in the lead-zinc mines, i.e. high background values. High concentration of As and Cd in the sediment is affected in a greater extent by high content of the two metals in the ore-surrounding soil in the lead-zinc mines, and in a lesser extent by contamination due to geoaccumulation and enrichment. High Pb concentration in sediment is affected in a greater extent by high content of the metal in the ore-surrounding soil in the lead-zinc mines, and in a lesser extent by contamination due to geoaccumulation and enrichment. The pollution sequence based on an average single pollution index is Pb(125.76) > As(55.48) > Zn(26.82 > Cd(14.17) > Cu(5.08) > Ni(1.36) > Hg(0.42), while based on the average geoaccumulation index, the sediment is mostly uncontaminated with the sequence Cd(1.1) > As(0.7) > Cu, Zn, Hg, Pb, Ni( Hg(4.1) > Pb(1.4) > Cu(0.9) > Ni(0.6). The results highlight the need for a comprehensive and detailed study program on heavy metal content in different soil and sediment resources to identify the magnitude and details of the problem associated with heavy metal contamination for development of a remediation plan and more effective pollution preventing measures including technology develop for recovering of useful components.

The study of the distribution law and origin of groundwater in Quaternary sediments downstream of the Red River Delta is approached in the direction of research on sequence stratigraphy and the distribution law of lithofacies according to space and time. However, the distribution law of lithofacies and groundwater depends on global sea-level changes and tectonic activities as the two most important reasons. Quaternary sediments of the Red River delta downstream have 5 sediment cycles corresponding to 5 sequences: (1) sequence 1 with Early Pleistocene age (Sq₁–\({\text{Q}}_{1}^{1}\)); (2) sequence 2 with early Middle Pleistocene age (Sq₂–\({\text{Q}}_{1}^{{2{\text{a}}}}\)); (3) sequence 3 with late middle Pleistocene age (Sq₃–\({\text{Q}}_{1}^{{2{\text{b}}}}\)); (4) sequence 4 with early Pleistocene age (Sq₄–\({\text{Q}}_{1}^{{3{\text{a}}}}\)); (5) sequence 5 with late Pleistocene–Holocene age (Sq₅–\({\text{Q}}_{1}^{{3{\text{b}}}}\)–Q₂). Each sequence is composed of three sedimentary systems tracts. The lowstand systems tract (LST) is characterized by a lowstand alluvial muddy sand facies complex that acts as a primary freshwater aquifer (S_marLST). The transgressive systems tract (TST) is characterized by a coastal swamp sand mud facies (M_samtTST) and a maximum transgression bay-lagoon mud facies (MmtTST) acting as an aquifuge. The highstand systems tract (HST) is characterized by sand bar facies (SamhHST) and delta plain sandy mud facies (M_samhHST). Thus, vertically Pleistocene sediments have 5 aquifers, in which each aquifer is constituted by the superposition of two successive facies complex: (1) upper part: lowstand alluvial gravelly sand facies complex (LST) and (2) lower part: highstand dune sand bar facies complex (SarLST/SamhHST). The spatial distribution of freshwater aquifers in 3 provinces Northwest Thai Binh, Ninh Binh—southeast Nam Dinh, and northwest Nam Dinh demonstrate the absence of shallow marine-bay mud facies.

This paper presents the results and assessment of the groundwater exploitation reserves in coastal areas of Ninh Thuan province. The research was based on determining the exploitation reserves of all grid cells with dimensions 500 m × 500 m distributed in fresh-salted water areas of the Holocene (qh) and Pleistocene (qp) aquifers. Each grid was assigned the corrected hydrogeological parameter values (depth, gravity coefficient, hydraulic conductivity, and drawdown level). The calculation results show that the total amount of potential exploitation reserves in the entire qh and qp aquifers-distributed areas is 561.8 × 10⁶ m³ per day, whereas in the freshwater area is 345.4 × 10⁶ m³ per day (61.5%), and the saline water area is 216.4 × 10⁶ m³ per day (38.5%). These potential exploitation reserves can be used for groundwater exploitation management and planning in Ninh Thuan province.

The period from 1 ka BP to the present, the changes of the Northern plain coastline are extremely complex under the impact of nature and human activities; it can be divided into 3 periods: (1) Period from 1 ka BP to 1787: formation of highstand deltaic sandy mud facies complex (M_samHST\({\text{Q}}_{2}^{3}\)). The Nam Dinh area is still accreted more strongly than Thai Binh and Ninh Binh. On the contrary, the Bach Dang estuary area was strongly estuaryizated; (2) The period from 1787 to 1960: due to the great flood that broke the Red River dike in 1787, the Red River was filled up and narrowed, to change its flow to the tributary on the Thai Binh side, flowing into the Ba Lat river mouth and the Red River in Nam Dinh turned into the smaller So River; (3) The period from 1960 to present: the Hai Hau coastline began to erode strongly at an average rate of 25 m/year. Meanwhile, the rate of sedimentary accretion at the Day River mouth increased dramatically by 100 m/year.

The paper presents the results of evaluating and determining the potential exploitation reserves of groundwater in Ca Mau province. In particular, the study has identified the regional hydrogeological parameters, assessed potential exploitation reserves of groundwater, forecasted water level fluctuations, determined quantities of groundwater supply from the sea and from rainwater according to space and time, and detailedly established input parameters and boundary value for hydrogeological modelling. Calculation results show that the total potential reserves of qp2-3 aquifer is 1,924,111 m3 per day, in which the fresh water is 1,072,145 m3 per day (accounting for 55.7%) and the salt water is 623,067 m3 per day (accounting for 44.3%).