INTRODUCTION Groundwater is a vital source of domestic, industrial, agricultural uses in arid areas where precipitation and fresh surface water are limited.With the rapid development of industry and population growth in developing countries like China, human activity induced groundwater over-exploitation and pollution have become more and more serious. It is reported that there are as many as 2.8 million wells in China 1 and the heavy groundwater extraction has caused many problems such as groundwater level drop, salt water intrusion, ground surface depression, etc. In addition, nitrate pollution caused by agricultural activities has also been widely reported in many parts of China 2-6 . All these reports have indicated that China faces a serious situation of groundwater pollution. These years, many water quality assessment methods have been proposed 7,8 . Water quality index (WQI) is a relatively easy tool and it has been widely used all over the world for the quality assessment of groundwater and surface water. Bordalo et al. 9 used a modified nine-parameter Scottish water quality index to assess the monthly water quality of the Douro river, an internationally shared river, during a 10-year period (1992- 2001), while Chaturvedi et al. 10 assessed the groundwater quality near an industrial area of Balrampur city, India. Zhongning Shikong industrial area is located in the north bank of the Yellow river, Zhongning County, covering an area of 54 km 2 . There are several metal smelting plants in this area such as Ningxia Tianyuan Manganese Company Limited Environmental Chemistry of Groundwater Near an Industrial Area, Northwest China JIANHUA WU 1,2 , PEIYUE LI 1,2,* and HUI QIAN 1,2 1 School of Environmental Science and Engineering, Chang'an University, No. 126 Yanta Road, Xi'an 710054, P.R. China 2 Key Laboratory of Subsurface Hydrology and Ecology in Arid Areas, Ministry of Education, No. 126 Yanta Road, Xi'an 710054, P.R. China *Corresponding author: Fax: +86 29 82339952; Tel: +86 29 82339327; E-mail: lipy2@163.com; wjh2005xy@126.com (Received: 18 February 2013; Accepted: 23 October 2013) AJC-14277 An entropy-weighted water quality index was applied to assess the groundwater quality near an industrial park (China) where several metal smelting plants are located. The study shows that most physiochemical parameters except HCO3 – , NO3-N, TDS, total hardness, F – and Mn are within the permissible limits of WHO standard or national standard of China. The excessive HCO3 – , TDS, total hardness and F – are caused mainly by natural rock weathering processes, while that of NO3-N is caused by agricultural activities and the high content of Mn in groundwater is induced by both natural and human processes. The water quality indexes range from 27.94 to 128.94 %. Sixty five per cent of the total samples are of medium quality, 25 % are of good quality and the remaining 10 % are of poor quality. The high water quality indexes are caused by the excess NO3-N, total hardness and Mn which are mostly human induced. Key Words: Water quality assessment, Water quality index, Groundwater pollution, Anthropogenic interference. which is the largest manganese manufacturer in the world. The industrial production in this area has brought vast profits to local economy. However, at the same time, it also brings groundwater pollution. Therefore, the aim of the study is to investigate the environmental chemistry of groundwater and assess its quality using the internationally used method. EXPERIMENTAL Water sample collection and analysis: Twenty samples were collected in July 2012 from hand pumping wells and the sampling locations are shown in Fig. 1. Samples were analyzed by the laboratory of Ningxia Environmental Protection Office. Each of the groundwater samples was analyzed for major ions (Na + , K + , Ca 2+ , Mg 2+ , Cl – , SO4 2- , HCO3 – , CO3 2- , F – , NH4 + -N, NO3 – -N, NO2 – -N), pH, chemical oxygen demand (COD), total dissolved solid (TDS), total hardness (TH), metasilicic acid, arsenic, volatile phenol, cyanide and heavy metals (copper, aluminum, manganese, zinc, cadmium, mercury, nickel, lead and chromium). During the sample collection, transportation and preservation, all procedures followed standard requirement raised by the Chinese Ministry of Water Resources to ensure the consistency of data. Entropy-weighted water quality index: Entropy-weighted water quality index (EWQI) is an improved water quality index which considers the different significances of different physiochemical indices to the water quality 11,12 . This method has been introduced in our previous studies 11,12 . Since the limit Asian Journal of Chemistry; Vol. 25, No. 17 (2013), 9795-9799 http://dx.doi.org/10.14233/ajchem.2013.15355