Sampling frequency groundwater

Figure 2. Map of arsenic distributions in groundwater from Bangladesh. The map shows a smoothed distribution determined by disjunctive kriging on 3207 samples of groundwater (<150 m depth, Gaus et al, 2001). Insets are frequency histograms of the concentrations of arsenic (pg F ) in groundwater from three selected study areas analysed in more detail...

Chlordane has been detected in both groundwater and surface water at low levels of 0.001 to 0.01 pg/L (USEPA 1988). A high frequency of chlordane detection was noted in seawater samples collected from a Hawaiian marina up to 90% of all samples contained cw-chlordane, and 68% contained trans-chlordane (IARC 1979). Because of chlordane s use as a soil-injected insecticide and its persistence, it has the potential to contaminate groundwater, particularly when it is applied near existing wells (USEPA 1988). 

Monitor indicator parameters (pH, temperature, conductivity, ORP) in a flowthrough cell every 1-2 minute (min) during purging. At the same frequency, monitor dissolved oxygen and turbidity. Record all measurements in the Groundwater Sampling Form. 

Barium has been detected with a positive geometric mean concentration of 101.6 mg/L in groundwater samples from approximately 58% of the 2,783 hazardous waste sites that have had samples analyzed by the Contract Laboratory Program (CLP) (CLPSD 1989). Barium has also been detected with a positive geometric mean of 62.6 mg/L in surface water samples from 27% of the sites in the CLP statistical database (CLPSD) represent frequency of occurrence and concentration information for NPL sites only. 

The concentrations of arsenic are usually, but not always, stable, Where concentrations are likely to be stable (i.e. deep groundwater), monitoring would normally only need to take place infrequently. Where water supplies for populations are subject to treatment to remove arsenic, samples are normally best taken at the treatment works, where the frequency of monitoring should be sufficient to ensure that the process is effective,... 

Dichloroethane has been detected in groundwater samples taken at an estimated 9% of the NPL hazardous water sites participating in the Contract Laboratories Program (CLP) at a geometric mean concentration of 23.1 ppb for the positive samples (CLP 1989). The compound was also detected in surface water samples taken at an estimated 2% of the NPL hazardous waste sites participating in the CLP at a geometric mean concentration of 24 ppb for the positive samples. Note that these data from the CLP Statistical Database represent frequency of occurrence and concentration information of NPL sites only. 

Groundwater samples taken from 178 hazardous waste disposal sites were found to contain 1,1-dichloroethane at 18% frequency (Plumb 1987), with an average concentration of 0.31 ppm and a maximum of 56.1 ppm (Yang and Rauckman 1987). Using the STORE database. Staples et a]. (1985) reported median concentrations of less than 0.1 ppb in 8,716 samples of ambient water (3% detectable values), less than 1.0 ppb in 1,375 effluent samples (5% detectable values), less than 5.0 ppb in 354 sediment samples (0.6% detectable values), and less than 0.05 ppb in 94 biota samples (no detectable values). Also using the STORE database, Perwak et al. (1982) reported that 1,1 -dichloroethane was not found in the sediment of the lower Mississippi or the western Gulf of Mexico however, a maximum concentration of 5 ppb was detected in sediment samples from the Pacific Northwest. 

Table 6. Frequency distribution of arsenic concentrations in analysed groundwater samples from Nepal (from Chitrakar and Neku, 2001 Tandukar, 2001)...

TABLE 9.13 Frequency with Which Some Pesticides Have Been Detected in U.S. Groundwater Samples... 

Plasticizers have been detected in surface water (Table 18.4) at concentrations ranging from 0.002 to 86 pg/L, and in groundwater samples at concentrations of 8 ng/L to 200 pg/L (Table 18.5). Kohli et al generalized that the most commonly occurring phthalates in siuface water were di-(2-ethylhexyl) phthalate and di-n-butyl phthalate. However, some of the samples in these reports were biased in that the samples were collected from monitoring wells near waste sites and industrial areas. Plasticizers have also been reported in samples of drinking water (Table 18.6) at concentrations ranging from 0.03 to 470 pg/L (see HSDB for specific information on the location of the samples and frequency of... 

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