Hydrochemical Characteristics and Control Factors of Pore-water in the Middle and Upper Reaches of Muwen River

Abstract

In order to study the hydrochemical characteristics and ion sources of pore water in the middle and upper reaches of the Mouwen River, 29 groups of pore-water samples were collected in the Laiwu Basin. The main ion characteristics and their controlling factors of pore-water in this area were analyzed by using correlation and principal component analysis, Piper trigram, and Gibbs diagram methods. The main material sources of pore water in this area were revealed. The results showed that HCO3-, NO3-, SO42-, and Ca2+ were the main anions and cations in the pore water of the middle and upper reaches of the Mouwen River. With TDS >1000 mg·L-1 as the standard, the normal water chemistry type was mainly HCO3·NO3·SO4-Ca and HCO3·SO4-Ca·Mg, whereas the abnormal water chemistry type was mainly NO3·Cl-Ca. The chemical evolution of groundwater was mainly influenced by rock weathering, cation alternation adsorption, and human activities. Na++K+ mainly came from silicate weathering and dissolution, and HCO3-, Ca2+, and Mg2+ came from calcite weathering and dissolution involving carbonate and sulfuric acid. Alternation adsorption of cations and weathering of silicate rock provided a surplus of Ca2+ and Mg2+ for pore water. Industrial and mining activities such as domestic sewage mixing, agricultural planting activities, and iron and coal mining changed the chemical composition of pore water, especially NO3- exceeding the standard, which has become the main problem of the local groundwater chemical environment.