(1. Zhejiang Geological Environment Monitoring Station, Hangzhou 310007; 2. Nanjing Institute of Geology and Mineral Resources, Nanjing 2 100 16)

The organic pollutants in shallow groundwater samples of X city in the east were quantitatively analyzed, and the distribution characteristics of organic pollutants in shallow groundwater were studied. According to the detection limit and the standard value of drinking water, the organic pollution of shallow groundwater was preliminarily evaluated by pollution index method, and its sources were discussed. The results show that chloroform is the most common halogenated hydrocarbon, followed by tribromomethane, and polycyclic aromatic hydrocarbons are acenaphthene, acenaphthene, phenanthrene, anthracene, pyrene, benzo [a] anthracene, benzo [b] fluoranthene, fluoranthene, naphthalene and pyrene, and organochlorine pesticides are P, P ′-DDT. The shallow groundwater in X city is slightly polluted by organic matter, among which P, P ′-DDT and benzo [a] anthracene, which have great influence on the environment, should be paid attention to. According to geochemical parameters and shallow groundwater environment background, it is inferred that organic pollutants come from various industrial and mining enterprises, the application of chemical fertilizers and pesticides, the incomplete combustion of landfill sites and fossil fuels, and there are differences in different functional areas of the city.

Key words: shallow groundwater; Organic pollution; Safety assessment; The eastern city of China.

X City is a rapidly rising city in the developed areas of eastern China, located at the intersection of rivers, seas, lakes and rivers. Dense population, rich characteristics of water towns, synchronous development of industry and agriculture, high degree of groundwater development and utilization, complete types of groundwater exploitation, wide exploitation range and large exploitation amount, especially the drinking water source for residents, agriculture and rural ecological construction are closely related to groundwater. With the development of social economy, the pollution load of groundwater is increasing, especially the discharge of organic pollutants is increasing, some of which are often difficult to degrade and have bioaccumulation, "three causes" or chronic toxicity, so the organic pollution of groundwater will threaten the drinking water safety, ecological environment and human health in this area. However, shallow groundwater is more susceptible to pollution. Therefore, the investigation and evaluation of organic pollution of shallow groundwater in X city will provide a basis for the protection of groundwater resources and the prevention and control of organic pollution, and also provide a reference for other cities in the east to carry out the investigation and evaluation of organic pollution of groundwater.

1 Sampling and analysis of samples

In the eastern city of X, shallow groundwater samples are arranged according to urban functional areas such as agricultural areas, residential areas, commercial areas, industrial areas and garbage dumps (table 1).

Table1distribution of shallow groundwater samples in x city

On the basis of field investigation, select a well point which is representative, informative, easy to sample, relatively stable and as close as possible to the previous dynamic monitoring wells.

Prepare sampling equipment: empty bottle at the top, PTFE or glass container with good sealing, PTFE sealing film. The nonvolatile organic water bottle was soaked in 1: 1 nitric acid overnight, washed with tap water for 3 times, washed with water for removing organic substances for 3 times, washed with acetone for 2 times, and dried at 360℃ 1 hour.

Before sampling, clear the accumulated water in the well tube, rinse the sampler or sampling bottle with the water to be collected for 3 ~ 4 times, and then slowly add the water sample into the bottle along the bottle wall. In the process of loading the sample, the bubbles in the bottle shall not roll up and down to make the water sample as full as possible. After the sampling bottle is filled, the sealing pliers should cover the bottle cap or bottle mouth with PTFE film, then plug the bottle cap tightly, turn the bottle over for inspection, and re-sample if there are bubbles. Samples should be stored in a dark and low temperature environment, if possible, at 4℃ or in an environment with ice cubes, and placed in isolation. In sampling, 10% samples are selected to collect parallel samples, and 5% samples are collected on site.

Seven shallow groundwater samples were analyzed. Analysis methods: determination of water quality and volatile halogenated hydrocarbons, gas chromatography, GB/T17130-1997; Water quality-Determination of benzene series-Gas chromatography GB/T11890-1989; Water quality, determination of bhc and ddt, gas chromatography gb/t7492-1987; 16 polycyclic aromatic hydrocarbons, USEPA method 525.2 determination of organic compounds in drinking water, liquid phase extraction, capillary column gas chromatography/mass spectrometry. The analysis and test of the samples are undertaken by the Earth Science Experimental Center of China Geo University, and the instrument and equipment are HPGC-6890 gas chromatograph with the serial number of 1990006. Quality control in testing process.

* * * 44 kinds of organic compounds were detected in shallow groundwater, including 7 kinds of halogenated hydrocarbons, 7 kinds of benzene series (monocyclic aromatic hydrocarbons), 0/6 kinds of polycyclic aromatic hydrocarbons and 0/4 kinds of organochlorine pesticides.

2 evaluation methods

2. 1 Evaluation method of organic pollution of shallow groundwater

Forty-five kinds of organic substances in shallow groundwater are toxicological indexes. The measured concentration Ci of I component in groundwater is compared with its detection limit (control value C0max) and drinking water standard value (table 1) to evaluate the organic pollution of shallow groundwater.

No pollution: Ci≤ detection limit; Light pollution: detection limit < ci ≤ 1/2× drinking water standard value; Moderate pollution: 1/2× drinking water standard value < CI ≤ drinking water standard value; Severe pollution: standard value of drinking water < CI ≤ 5× standard value of drinking water; Extreme pollution: CI > 5× standard value of drinking water.

2.2 shallow groundwater organic matter safety assessment method

The safety of organic matter in shallow groundwater is evaluated by environmental impact degree AS(Ambient Severit), namely:

Compilation of geological survey results in East China: 1999~2005

In formula (1), ASi is the environmental impact degree of an organic substance in shallow groundwater; Ci is the concentration of some organic substances in shallow groundwater;

Compilation of geological survey results in East China: 1999~2005

As the target value of an organic substance I in water, according to the target value of water environment, the compilation of geological survey results in East China: 1999~2005.

, WHO recommended value [4], national standard value [1] and so on. AMEG, namely ambiet multimedia environmental goals, is the limit value of chemical substances or their degradation products in environmental media calculated by the industrial environment laboratory of the US Environmental Protection Agency [3]. The environmental safety assessment of organic matter in shallow groundwater adopts the total environmental impact assessment method. ASsuming that all organic substances have the same potential harm to people and the environment, As long AS As is the same, and assuming that the value of As is linear with the potential harm [3], the degree of environmental harm of shallow groundwater can be approximately expressed as the sum of As components (called total environmental impact), namely:

Compilation of geological survey results in East China: 1999~2005

When TAS is greater than L, it shows that toxic compounds in shallow groundwater are potentially harmful to human health. When TAS value in water is less than 1, the potential harmful effect is not obvious.

3 Results and discussion

3. 1 Detection of Organic Matter in Shallow Groundwater

Halogenated hydrocarbons detected in shallow groundwater in X city are mainly chloroform, followed by tribromomethane, and high-value points are mainly distributed in agricultural areas and garbage dumps (Figure 1, Table 2).

Figure 1 X detection of organic matter in shallow groundwater in the east of the city

Table 2 Organic Content of Shallow Groundwater in East X City and Preliminary Evaluation Results (ng/L)

sequential

No monocyclic aromatic hydrocarbons were detected in the shallow groundwater in X city.

All samples of acenaphthene dihydrogen, acenaphthene dihydrogen, phenanthrene, anthracene, pyrene, benzo (a) fluoranthene and benzo (b) fluoranthene were detected, and the detection rate of fluoranthene was 86%, and the detection rate of naphthalene and hydrazide was 57%. High value points are mainly distributed in agricultural areas, commercial areas and residential areas. Fluorene, benzo [k] fluoranthene, benzo [a] pyrene, dibenzo [a, h] anthracene, indeno [1, 2,3-c, d] pyrene and benzo [g, h, i] perylene were not detected.

The detection rate of organochlorine pesticides in P, P ′-DDT was higher (86%), followed by O, P ′-DDT, γ-HCH (57%) and P, P ′-DDT and δ-HCH (43%). The high-value points are mainly distributed in garbage dumps and industrial areas, followed by agricultural areas and residential areas.

3.2 Preliminary Assessment of Organic Pollution of Shallow Groundwater

Preliminary evaluation shows that the shallow groundwater in X city has been slightly polluted by organic pollutants, and the main organic pollutants are polycyclic aromatic hydrocarbons, DDT and bhc (Table 2).

3.3 Safety Assessment of Organic Matter in Shallow Groundwater

The maximum environmental impact degree of organic matter in shallow groundwater in X city is less than or much less than 1, indicating that it is not harmful to the environment and human health at present. Yes, p'-DDT (0.32) and benzo [a] anthracene (0. 18) are the main arsenic, followed by pyrene (0.042), o-DDT (0.037) and p '-DDD(0.03 1.

The total environmental impact of shallow groundwater in X city is 0.07 ~ 0.43, with an average of 0.20, especially in agricultural areas and garbage dumps. The organic pollution of shallow groundwater in typical urban functional areas does not show obvious potential harm.

3.4 Discussion on the Source of Organic Matter in Shallow Groundwater

In the study of geochemistry and environmental geochemistry, some characteristic compound indexes are often used to judge the source of PAHs in combination with regional environmental characteristics, industrial layout and pollution emission types.

Table 3 Safety Assessment of Organic Matter in Shallow Groundwater in X City

sequential

Note: a. China GB3838-2002 standard limit value of specific project of centralized drinking water surface water source [1]; B1998 who recommended value who drinking water quality standard [4]; C.2002U.S.EPA current drinking water standard [2]; D. China CJ/T206-2005 Urban Water Supply Quality Standard [5]; E.AMEGwh water environment target value [3].

High molecular weight PAHs with more than 4 rings mainly come from high temperature combustion of fossil fuels, while low molecular weight PAHs (with 2 ~ 3 rings) come from oil pollution [6]. The phenanthrene/anthracene ratio (P/A) of PAHs from wastewater discharge and leakage sources such as coking, petroleum cracking, crude oil leakage, coal tar refining and dye industry is 4.4 ~ 7.9, while the P/A value of PAHs from household and domestic stoves, industrial boilers, open-air combustion and fires, motor vehicles and internal combustion engines and atmospheric deposition sources is > 10 [7]. The ratio of fluoranthene/pyrene (Fl/Py) is 1.4, which represents the source of coal combustion products, and the ratio 1 represents the source of wood combustion. If the ratio is less than 1, it indicates that it comes from petroleum [8].

The content of polycyclic aromatic hydrocarbons in shallow groundwater generally decreases in the order of 3 rings > 5 rings > 4 rings > 2 rings > 6 rings. The P/A value is 0.68 ~ 8.52, and the Fl/Py value is 0 ~ 1.03, which shows the mixing characteristics of combustion source and petroleum source. The PAHs content in the 2+3 ring of agricultural area A 1, residential area R 1 and garbage dump W 1 is much higher than that in the 4 ring and above, and the Fl/Py value (0.0 1 ~ 0.62) is less than 1, and the P/A value is 0.60. The PAHs content in agricultural area A2 and commercial area C 1 sample 2+3 is less than or equal to 4 rings or more, and the Fl/Py value is 1.23 ~ 3.45, and the P/A value is 0 ~ 0.25, which mainly comes from the incomplete combustion of fossil fuels, including industrial coal, domestic heating coal and traffic pollution. The PAHs content in ring 2+3 is much higher than that in ring 4 and above, with a large P/A value (6.60 ~ 8.52) and a large change in Fl/Py value (0.3 1 ~ 1.03), so it is a mixed source.

Table 4 Characteristic Index of Polycyclic Aromatic Hydrocarbons in Shallow Groundwater in East X City

4 conclusion

Halogenated hydrocarbons detected in shallow groundwater in X city are mainly chloroform, followed by tribromomethane, and high-value points are mainly distributed in agricultural areas and garbage dumps. Polycyclic aromatic hydrocarbons (PAHs) such as acenaphthene, acenaphthene, phenanthrene, anthracene, pyrene, benzo (a) fluoranthene, benzo (b) fluoranthene, fluoranthene, naphthalene, Qu, etc. 10 are generally detected, and the high-value points are mainly distributed in agricultural areas, commercial areas and residential areas. The detection rate of organochlorine pesticides in P, P ′-DDT, O, P ′-DDT, γ-HCH, P, P ′-DDT and δ-HCH is high, and the high-value points are mainly distributed in garbage dumps and industrial areas, followed by agricultural areas and residential areas.

The preliminary evaluation shows that the shallow groundwater in X city has been slightly polluted by organic pollutants, and the main organic pollutants are polycyclic aromatic hydrocarbons, DDT and bhc.

The maximum environmental impact degree and total environmental impact degree of organic matter in shallow groundwater in X city are both less than or far less than 1, indicating that it is not harmful to the environment and human health at present, but P, P ′-DDT and benzo [a] anthracene with high AS should be paid attention to.

According to geochemical parameters and shallow groundwater environment background, it is inferred that organic pollutants come from various industrial and mining enterprises, the application of chemical fertilizers and pesticides, the incomplete combustion of landfill sites and fossil fuels, and there are differences in different functional areas of the city.

refer to

[1] State Environmental Protection Administration, State Administration of Quality Supervision, Inspection and Quarantine. Environmental Quality Standard for Surface Water GB3838-2002.2002

[2] United States Environmental Protection Agency. Drinking water standards and health recommendations 2002 edition. 2002

Wang Jing, He, Wang Yaoqu, et al. Environmental Assessment Data Manual-Identification Value of Toxic Substances (1 version). Beijing: Chemical Industry Press, 1988, 2 ~ 423.

[4] WHO. Guide to drinking water quality, 2nd edition. Appendix to health standards and other supporting information. Geneva: World Health Organization,1998,2:123 ~152.

[5] People's Republic of China (PRC) and Ministry of Construction. Water Quality Standard for Urban Water Supply CJ/T 206-2005.2005

[6] Erwin L. Impact of land use on biodiversity and life support in life cycle assessment. Journal of cleaner production, 2000, 8:3 13~3 19.

[7] GSchwind P.M., Hites R A. Flow of Polycyclic Aromatic Hydrocarbons to Marine and Lake Sediments in the Northeast of the United States. Journal of geochemistry and cosmochemistry, 198 1, 45:2359~2367.

[8] Edward N.T. Polycyclic Aromatic Hydrocarbons in Terrestrial Environment: A Review. J. environment Qual。 1983, 12:427 ~432

[9] Simoneit B R T. Characteristics of organic matter in troposphere and sources of oil and pyrolysis residues in topsoil in the western United States. Atoms. environment , 1984., 18:5 1 ~67

Present situation and safety evaluation of organic pollution of surface water in X city, eastern China

Yu Guangming 1, Liu Hongying 2, Su Jingwen 2, Zhang Taili 2, Li Wei 1, Shen Manting 2.

(1. Zhejiang Geological Environment Comprehensive Monitoring Station, Hangzhou 310007; 2. Nanjing Institute of Geology and Mineral Resources, Nanjing 2 100 16)

Abstract: Based on the investigation and quantitative analysis of the concentration of organic pollutants in groundwater in X city, eastern China, the distribution characteristics of these compounds were studied. Referring to the drinking water standards and negative detection limits of China, WHO and EPA, the organic pollution of groundwater in X city was evaluated by pollution index method, and the sources of these compounds were discussed.

The results show that chloroform is the main groundwater in X city, followed by bromomethane in chlorinated solvents, anthracene in acenaphthene, acenaphthene, phenanthrene, anthracene, pyrene, benzo [a] acenaphthene, benzo [b] fluoranthene, fluoranthene, naphthalene and polycyclic aromatic hydrocarbons, and P, P ′ in organochlorine pesticides. Most of the surface water in X city is slightly polluted, among which the environmental concentration (AS) of P, P ′-DDT and benzo [a] anthracene is relatively high. According to the geochemical parameters of organic pollutants and the environmental background of surface groundwater, different types of industrial production areas, the use of fertilizers and pesticides, landfill and incomplete pyrolysis of fuel may be different sources of organic pollutants in X city, and there are differences in different functional areas of the city.

Keywords: surface groundwater; Organic pollution; Safety assessment; The eastern city of China